Fats and Oils Handbook
Michael Bockisch Hamburg, Germany
Champaign, Illinois
This book is dedicated to my wife Gudrun to whom, in the course of doing this translation, revision, and update, I had to break my promise never to write a book again, and also to my son Benjamin and my daughter Valerie. AOCS Mission Statement To be a forum for the exchange of ideas, information, and experience among those with a professional interest in the science and technology of fats, oils, and related substances in ways that promote personal excellence and provide high standards of quality. AOCS Books and Special Publications Committee E. Perkins, chairperson, University of Illinois, Urbana, Illinois J. Endres, Fort Wayne, Indiana N.A.M. Eskin, University of Manitoba, Winnipeg, Manitoba T. Foglia, USDA-ERRC, Wyndmoor, Pennsylvania L. Johnson, Iowa State University, Ames, Iowa Howard R. Knapp, University of Iowa, Iowa City, Iowa J. Lynn, Edgewater, New Jersey M. Mathias, USDA-CSREES, Washington, D.C. M. Mossoba, Food and Drug Administration, Washington, D.C. G. Nelson, Western Regional Research Center, San Francisco, California F. Orthoefer, Monsanto Co., St. Louis, Missouri M. Pulliam, C&T Quincy Foods, Quincy, Illinois J. Rattray, University of Guelph, Guelph, Ontario A. Sinclair, Royal Melbourne Institute of Technology, Melbourne, Australia G. Szajer, Akzo Chemicals, Dobbs Ferry, New York B. Szuhaj, Central Soya Co., Inc., Fort Wayne, Indiana L. Witting, State College, Pennsylvania Copyright 0 1998 by AOCS Press. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means without written permission of the publisher. The paper used in this book is acid-free and falls within the guidelines established to ensure permanence and durability.
Library of Congress Cataloging-in-PublicationData Bockisch, Michael. [Nahrungsfette und ole. English] p. cm. Updated and revised translation of the original German work, Nahrungsfette und ole. Includes bibliographical references and index. ISBN 0-935315-82-9 (alk paper) 1. Oils and fats, Edible-Handbooks, manuals, etc. I. Title, TP670.B5713 1998 6 6 5 4 ~ 12 Printed in the United States of America with vegetable oil-based inks. 543 06 05 04
98- 11974 CIP
Preface Oils and fats have been constituents of human nutrition from ancient times. First, they contain the highest level of energy of all components of food; second, they supply essential elements for the body. However, the fundamental reason for their early and varied use was certainly the fact that they contribute to the development of flavor, making dishes tasty and giving them a good, smooth mouth-feel. In the course of his life, a human being living in the industrial nations consumes approximately three tons of fats and oiIs; about half of them are so-called invisible fats, hidden in other food, e.g., sausage and cheese. In the developing countries, the portion of fat in food intake lies far below the amount recommended by the World Health Organization (WHO). This is not due to limited world resources, but rather to problems of local purchasing power as well as logistics and distribution. Cultivation could easily rise considerably faster than the world population. Fats are an important factor in the economy because of their status as basic constituents of nutrition and the large amounts consumed. This becomes apparent in their ranking second in worldwide traded items. For some countries or regions, they represent an indispensable part of the gross national product and a source of foreign currency. Because of the development of new varieties of oil seeds, the areas under cultivation have been extended in the past decades from the earth’s sun belt to regions of temperate climate, which now deliver a substantial part of that crop. This has led to a shift in economic interests. ‘some of these factors will be discussed in this book to illustrate the large correlations that exist. This book will acknowledge the importance of fats and oils and give a survey of today’s state of the art in technology. Even when considering a topic that is relatively limited in scope, it is impossible for a single person to obtain more than a general view of the field. It follows that to give an adequate description, it is vital to have recourse to the knowledge base established over the years by the publications of many scientists and practitioners. I would like to express my thanks to all those colleagues whose findings and experiences formed a basis for my studies. Technology is not an end in itself. It is justified when it makes it possible to improve the foodstuff offered by nature in whatever way, whether in amount, cost, quality or other criteria that make possible its use or adaptation to our way of life today. To pursue food technology without knowing the “raw material” would mean working in a vacuum and performing “l’arrpour I’m.” In this book, great attention was thus paid to describing the sources of the oils and fats, and also the fats and oils themselves in such a way that the technological steps be well-founded and the purpose clear. Since the industrial revolution, there has been a great boom in the industry of edible fats and oils. The processes that remain in use today are founded on basic findings from approximately 100 years ago. Much has been improved since that time, and many facts already known are exploited today only on the basis of improved technology. Technology will continue to develop in parallel with man’s changing attitude to it. In the broadest sense, progress in biological science and biotechnology contributes to this. Because biotechnological processes are reputed to be more natural V
vi
Preface
than chemical ones, there is an attempt to use enzymic reactions for fat technology. Much more far-reaching effects can be achieved by cultivation or the application of gene technology. Plants containing fats and oils in a desired composition, structure and quality render superfluous certain steps of treatment or modifications. To date, agriculture has not yet fully realized the potential offered by the cultivation of tailormade plants for certain purposes, as opposed to mass cultivation. In addition to these aspects, the development of machines and equipment leading to a more responsible way of dealing with raw materials and the environment continues. New processes of refining are confined mainly to physical modes of operation and protection of energy and water resources, in keeping with the spirit of the period and the desire to keep costs low. The manufacturers of such equipment are constantly engaged in new and further developments. Here, I would like to thank the companies that are mentioned subsequent to the bibliography for their support in providing pictures and information. This book will survey the raw materials predominantly employed and the spectrum of processes used today. Man’s ability to absorb information visually, i.e., via pictures, is many times greater than through the other senses or through transposition from language. A diagram or figure conveys more than a thousand words. To impart information quickly and efficiently, a focus of importance in this book was the explanation of technological steps in the form of graphs, a form of presentation that offers the reader a quick orientation and conveys a general view. Sufficient detail is offered to highlight the critical points without obscuring the presentation of essential information. In that sense, this book can be considered a sort of picture-bookhopefully, in a good sense. Michael Bockisch Vienna, I993
Preface to the English Edition AOCS Press has decided to publish this (originally German) book in English, updated and revised, and I am very grateful for the opportunity to expand its distribution and readership. The book was written primarily for Europe, and especially for Germany; some parts of Chapter 1, in particular, focus on the home situation. These parts have been changed where possible to give a broader picture. However, some figures remain in their original form, describing the situation in Germany. This was the case whenever they were too specific to be changed or when they illustrated certain facts that may well be used as an example for other regions in the world or as representative for the European Union. It is an honor to be able to reach a much wider readership. I translated the book to the best of my ability; however, without the help of my son, Benjamin, who had to do a lot of proofreading, of Ralf Tonn, who assisted me with the translation of Chapter 1, and especially of Iain Gow, Greg Knoll and Michael Gude, who did their very best as co-readers to improve my style, I (or you as the readers) would have been worse off. Both my readers and I owe them our thanks. In the interim between the original German issue and this one, almost half a decade has passed, and some of the trends that could be seen on the horizon have intensified. The skepticism towards any form of technology has increased in some countries, especially Scandinavia and the German-speaking countries, coming very close to hostility at least in some parts of the population. This deepens the gap between the wealthy countries that can afford to reject useful technology and those parts of the world in which technology is urgently needed to feed the increasing and often poor population. It seems that part of today’s fat technology will disappear in Europe or that chemical processes will be replaced by physical ones regarded as more environmentally friendly or by enzymic ones regarded as biological and thus, natural. On the other hand, there is total rejection in some quarters of new technologies such as biotechnology whether the concern is enzymes and their methods of production or genetically modified organisms (GMO). The contradiction between the existence of less technology and the development of new plants that may save some processing steps will be difficult to resolve. The next two to three years will determine where these new developments will be accepted and where they will not. A start was made in 1996 with the introduction of GMO soybeans, with other modified oilseeds following mainly in 1998. Lastly, I hope my readers will follow the advice of the great German poet Wolfgang von Goethe, who said: “Also, we should not deny that we are willing to forgive one or the other typing error in a book because we feel flattered by the fact that we detected it.”
Michael Bockisch Hamburg, 1997
vii
Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
v
Chapter 1
The Importance of Fats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1. A History of the Production of Oil and Fat 1.2. Fat in Food and Food’s Raw Materials 1.3. The Economic Importance of Oils and Fats 1.4 Fat in Nutrition 1.5. Fats and Oils in Legislation 1.6. Fats as Technical Raw Materials 1.7. Fats and Oils as a Source of Energy 1.8. New Sources of Raw Materials 1.9. Substitutes for Fat 1.10. References
1
Chapter 2
Composition, Structure, Physical Data, and Chemical Reactions of Fats and Oils and Their Associates . . . . . . . . . . . . . . . .53 2.1. Components of Fats and Oils 2.2. The Structure of Triglycerides 2.3. Physical Characteristics 2.4. Chemical Reactions 2.5. Lipids 2.6. References
Chapter 3
Animal Fats and Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Milk Fats 3.2. Rendering Fats 3.3. Marine Oils 3.4. References
121
Chapter 4
Vegetable Fats and Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. OiVFat-Containing Plants 4.2. Pulp Oils 4.3. Seed Oils 4.4. Nonedible Oils and Fats 4.5. Other Oil Sources 4.6. References
174
Chapter 5
Production of Vegetable Oils and Fats 5.1. Pulp Oils 5.2. Seed Oils and Fats
......................
345
Chapter 6
Modification of Fats and Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1, Application and Combination of Modification Processes 6.2. Fractionation 6.3. Winterization 6.4. Interesterification 6.5. Hardening 6.6. References
446
ix
X
Contents
Chapter 7
Refining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1, Economic Importance of Refining 7.2. Neutralization 7.3. Bleaching 7.4. Deodorization 7.5. Physical Refining 7.6. Energy Consumption and Investment 7.7. Importance of Refining for Removal of Environmental Contaminants 7.8. References
Chapter 8
Fat as, or in, Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1. Butter 8.2. Margarine 8.3. Edible Fats 8.4. Salad and Frying Oils 8.5. Mayonnaise 8.6, Vegetable Creams, Cream Substitutes 8.7. Peanut Butter 8.8. Margarine and Oils with Medium-Chain Triglycerides 8.9. Monoglycerides and Diglycerides 8.10. References
719
Chapter 9
Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1, Acid Number 9.2. Saponification Number 9.3. Iodine Value 9.4. Peroxide Value 9.5. Unsaponifiable Matter 9.6. Water Content 9.7. Phosphorus Content 9.8. Color 9.9. Hexane in Extraction Meal 9.10. Fibers in Extraction Meal 9.1 1. Protein in Extraction Meals 9.12. Ash Content 9.13. Solid Fat Content 9.14. Dilatation 9.15. Lipids Analysis
803
Chapter 10
Conversion Tables and Abbreviations. . . . . . . . . . . . . . . . . . . . . . .
809
Chapter 11
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
813
Chapter 12
Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
815
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
819
.613
Chapter 1
The Importance of Fats The importance of fats for humans, animals and plants lies in their high content of energy, which permits the greatest possible storage of energy in the smallest possible amount of food substance. In addition, fats allow humans and animals to consume fat-soluble vitamins and provide them with essential fatty acids, that is, those indispensable fatty acids that their bodies are unable to synthesize themselves. Fats are omnipresent in nature, although in the most diverse quantities. In the human body, they play a decisive role as well, beginning with the nutrition of the infant with breast milk. During the first 5 d, breast milk contains an average of 29.5% fat; from d 6 through 10, the amount is 35.2% and later 45.4% (Macy 1949). In the course of life, a human living in the industrial world satisfies an average of >40% of energy demand with fat. Metabolized in the human body, fats yield 38 kj/g of energy (9 kcal/g). In this exothermic reaction, -2000 mL of oxygen per gram of fat is consumed and -1400 mL of carbon dioxide is produced (Peters and van Slyke 1946). In addition to -63 ton of water, 0.5 ton of alcohol, 8 ton of carbohydrates and 2 ton of proteins, humans consume -3 ton of fat during their lives. The efficiency of fat as foodstuff is very high, because the fat contained in food is almost completely reabsorbed by the body; in the feces (in the course of one’s life -5 ton, plus 30 ton of urine) only 3.3% of lipids can be found (Pimparkar 1961). Thus, fats play an indispensable part in nutrition as supplier of energy, source of compounds that the body cannot synthesize by itself, and carrier of vital substances. Fats cannot be replaced by other substances. Apart from this physiological aspect, they are excellent carriers of flavors, and dishes prepared with fats are much tastier than others. Fats also provide a smooth, creamy consistency to many dishes, which translates into a good mouth-feel. This explains in part why the consumption of fat is still very high today, even though the segment of the population performing hard labor has diminished greatly compared with the past, rendering a very high supply of calories no longer necessary (see also Chapter 1.4). The improvement in flavor, in particular, is certainly the reason why fats and oils have been appreciated for a long time. However, only since the beginning of the present century has it been possible in the industrial nations to provide the population with sufficient quantities of fat at reasonable prices (see Chapter 1.3). Because of this increasing importance of fats and oils, governments have intervened to a great extent in their production and distribution in the last 100 years (see Chapter 1.5). European food legislation, in particular, has often been marked by protectionist objectives. The importance of fats and oils to the global economy (Chapter 1.3) becomes clear when considering the amount of oilseed and fruit grown worldwide. In 1995, -60 million ton of palm fruit and -1 1 million ton of olives as well as >200 million ton of oilseeds were harvested. From these amounts, >90 million ton of oils and fats were derived. Many countries are trying to enlarge their shares in the interna-
2
Fats and Oils Handbook
tional market, a strategy that is usually to the disadvmtage of others and leads to defensive measures. National interests play a part here. For example, 10 years ago, the European Union began to promote the cultivation of sunflowers and rape in the area of the Community. A simultaneous attempt to stabilize the Community’s budget deficit by introducing a tax on fat caused the U S . to fear for its soy exports, resulting in a threat of trade obstructions aimed at the European automobile industry. The confrontation was averted in 1987, but it will reappear again and again, unless the issue of a tax on fat is buried for good. In addition to the importance of oils and fats for human nutrition, there is a substantial market for technical fats. The importance of these oils and fats will increase considerably in the future because they represent a vast potential of naturally regenerating raw materials in which the chemical and pharmaceutical industries have a special interest. A short survey of these technical fats is given in Chapter 1.6. The importance of oils and fats for human nutrition, the animal feed produced from the processing of most oil plants and the economic importance of oils and fats, i.e., the fact that many millions of people worldwide make a living by the production and processing of oils and fats, all combine to give special importance to technology. This may even be enhanced if oil-bearing crops could be offered to the chemical industry as a source of regenerating raw materials. Only -1% of -300,000 existing species of plants has thus far been examined for their qualifications as useful plants. Only 300 of these, i.e., 0.1%, are being used agriculturally today. About 7% of these, -20, are oil plants. A considerable potential, which may be suitable for the recovery of oil, thus remains. This is especially true when plants with a special fatty acid pattern are desired. In addition, there are new methods of plant breeding that also may open up new prospects.
1.1 A History of the Production of Oils and Fats From ancient times, man unconsciously consumed fat in his food via plants, fish, and meat. However, the use of oils and fats required some simple techniques. For example, only when the ability to make fm was discovered was it possible to melt the fat of hunted animals and store the fat. Storage also required the ability to produce vessels made from clay or another materials. Mutton tallow and lard, and later butter, cream, and fish oils were known in prehistoric times (Hanssen and Wendt 1965). Vegetable fats from olives and sesame seed, and possibly flax were also known. Until the previous century, the utilization of fats and oils as food went hand in hand with their use as fuel, predominantly for purposes of illumination. Even today, the name “lampante” for certain qualities of olive oil refers to this. As a base for ointments and cosmetics, they are still in use today, just as in the earliest periods. It is known from pictures that food factories were in existence in early days. Wooley (1929) presented a picture of an Egyptian dairy-farm that illustrated, among other things, the process of churning. Erman and Ranke (1923) showed the sequence of operations of a large-scale Egyptian bakery of Ramses 111 in Thebes
Importance of Fats
3
around 1200 B.C. in which a dough resembling a Chelsea bun is being baked in oil. People in the Mediterranean region and in Asia used oils long before those in Central Europe. With olives in the Mediterranean area and sesame in the area of the Euphrates and Tigris, oil plants that do not grow in the temperate latitudes were readily available. The Bible mentions oil in many passages. Moses, for example, required oil as a donation for the Tabernacle’s lamps; cake and pancakes were baked with unleavened oil (2 Moses 29). It was customary to anoint with oil, and Jacob anointed a stone this way to sanctify it. Passages in Luke indicate that oil was a valuable commodity. For instance, there is a description of how a person owed 100 barrels of oil to somebody else (Luke 16: 5.6). The importance of the olive tree to the people in the Mediterranean region also became visible by its being consecrated to the goddess of wisdom, Athene, in ancient Athens; it later became the symbol of peace and promise. Thus, after the Deluge, the dove came to Noah with an olive leaf in its beak (1 Moses 8:1l), a symbol of the world’s survival. Plinius described how to extract olive oil by pressing ripe fruit in a squeezing vise, a procedure customary in his time. Butter (“dense, solid milk foam”) was also mentioned, but only as a replacement for olive oil in times of need, or for baking. Another familiar practice of fat technology was the remelting of lard for cleaning purposes. Roman fat technology spread throughout the Mediterranean region. Excavations in Tunis show its propagation in Northern Africa; in Pompeii and Herculaneum, entire processing facilities consisting of oil mills, oil presses, oil shops, and oil depots were uncovered (UNION 1959). Because the fatty acids corroded copper, oil was transported in vessels made of lead, but also in tanker vehicles. These were carts carrying animal skins enclosed in iron hoops in which the oil was kept. Poppy seed has also been discovered in Swiss lacustrine dwellings dating from the 25th century B.C. It is probable that the inhabitants already knew poppy oil and that people north of the Alps became familiar with oil mainly through the occupation by Roman troops. According to tradition, oil was also extracted from beechnuts that were mashed, then wrapped in cloths and pressed between plates of metal or stone. Every large farm extracted its own oil. Later, agriculture made further progress, and rape and linseed were added as oil fruit. In the 16th century, the profession of the oil miller, who processed the farmers’ seeds, evolved. The oil was extracted by grinding, bruising, or pressing. Later, people shifted to squeezing vises. Windpower was used as propulsion in windmills. In the course of further development, hydraulic presses were built, and from the middle of the 19th century on, it was possible to extract oils and fats from the seeds by means of solvents. When the seafaring European nations conquered the world, the resources were expanded and unknown types of oil fruit with much higher contents of oil and fat than those previously known were brought to Europe. Until the cultivation of soybeans was widely expanded, these oilseeds yielded the substantial part of vegetable fats and oils consumed in Europe. The explosive increase in population in the industrialized countries of the world during the industrial revolution, combined
4
Fats and Oils Handbook
with urbanization, led to a new situation. The population that gathered in the cities had to be fed. This required an entirely new system of food distribution, which adapted itself to the change from domestic supply in small units (farms, villages or small towns) to industrial production. New requirements for food arose, especially concerning its preservation. New products such as margarine (see Chapter 8) and novel techniques such as hardening (see Chapter 6.4) made important contributions to mastering these challenges. Although the main concern in the late 19th and early 20th centuries was the satisfaction of basic needs, in today’s industrial society, there is no longer a problem of quantity. After the decline in food production caused by the two World Wars and the Great Depression, during which the question of “mere nourishing” became important, the essential aspect of the 1960s and 1970s was that of enjoyment. The primary function of food was no longer the supply of calories, but the experience of taste. Accordingly, the focus shifted from the production of quantities, which were in fact available, to quality. In particular, the emergence of the trend toward health consciousness has stimulated the demand for quality. Here the fat industry delivered exceptional contributions. The connection between cardiovascular disease and nutrition was detected in the early days. This knowledge was used to develop special products that provide preventive measures (e.g., becel; see Chapter 1.4). The excessive fat consumption of most of the world’s population and the consequences of overweight have led to the development of reduced-fat and very-low-fat variants of the most diverse types of food. For margarines, for example, the law had to be changed to allow this. Starting with margarines, food groups developed that made possible low-calorie nutrition, or, as in the case of becel (a trademark of Unilever concern), furnish variants of diverse foods free of or low in cholesterol and high in polyunsaturated fatty acids. In recent years, a new trend could be observed developing in parts of the population. Sensitized by a growing awareness for environmental issues, “naturalness” of products has been given high priority. Although the demands resulting from this are partly exaggerated and no longer have a clear foundation, it will lead to changes in technology in some fields, at least in the wealthier countries. In poorer countries, which strive to produce food for mere nourishment and survival, there is little patience for these trends. The priority here is to feed the population. Although the strong increase in population is no doubt leading to problems that cannot be overestimated, the production of fats has always increased at a rate higher than the population growth (see Chapter 1.3).
1.2 Fat in Food and Food Ingredients Fats and oils, as such, are used for the production of food; in addition, unprocessed food or ingredients for food production contain fats and oil, sometimes in substantial quantities. These include fruits and vegetables but also meat and fish (Table 1.1). For oil and fat technology, these figures are important because they help identify the raw materials for oil and fat production. In processed food, oils and fats are
lmportance of Fats
5
TABLE 1.1 Approximate Fat Content of Unprocessed Food FruiVNuts
(O/O)
Bananas Oranges Pears Sw. chestnut Avocado Coconuts' Almonds' Hazelnuts' Walnuts' Pecan nuts*
0.2 0.2 0.4 2.0 17 34 54 62 64 71
VegetabledCereals
Fish
(%)
Meat
(%)
Potatoes Tomatoes Broccoli Cabbage Corn Barley Mushroomst Soybeans
Haddock Cod Mackerel Caviar Herring
0.1 0.3 11.5 15 19 26
Chic ken breast Roast chicken Boiling fowl
1 6 20
0.1 0.2 0.3 0.8 1 .o 1.5 3 20.9
Miscellaneous
Eggs Milk
Eel Shrimp Lobster Mussels
1.5 2 1.3
11.5 3.7
Rabbit
8
Fillet of beef Haunch of beef Beef tenderloin
4.5 7 10
Fillet of pork Pork chop Bacon (lean) (fat)
4.5 7.5 65 88
'kernels. +dried.
also found in diverse quantities. The variety of foods listed below (Table 1.2) ranges from those which are produced by a single treatment step (e.g., by grinding) to those that require many steps of processing because they are composed of many kinds of raw material (Table 1.2). The figures cited can vary considerably and thus serve only as a basis for the order of magnitude of the fat content of the food.
1.3 The Economic lmportance of Oils and Fats Nourishment is an indispensable and essential need of the human race. It is the task of agriculture and the food industry to satisfy this need. Considering the current develop ment of the world's population, a huge demand is arising. This demand has to be satisfied under the best possible conditions. There remains a shortage of supply in many parts of the world. Considering the fat-providing potential of agriculture and industry, this demand should be able to be satisfied easily. In past years, the production of fat has grown at a faster pace than the population (Fig. 1.1). A shortage of supply is thus rather a problem of distribution and purchasing power than one of shortage in the sense of lacking potential. In the coming years, the production of fat will also grow more rapidly than the world population. Mielke (1985) estimated a 1Cfold increase in oil production from the year 1958 to the year 2000. During this period, the amount of soybean oil will increase sevenfold and palm oil production will increase 2.5-fold. For palm oil, this prediction is already far outdated. In the past 10 years, the volume of oilseeds stored as surplus amounted to an average of 14% of production (Mielke 1990).However, as can be seen from Figure 1.2, there is a strong correlation between gross national product, reflecting the standard of living, and fat consumption. Chma, India, Pakistan and Bangladesh currently represent almost one half of the world's pop ulation. Demand for fat by these four countries will increase not only as their popula-
Fats and Oils Handbook
6
TABLE 1.2 Aproximate Fat Content of Processed Fooda Sausages
(YO)
Corned beef Wieners Bavarian veal sausages Cervelat sausage German Fleischwurst Mortadella Calf liver pate Salami Smoked s. spread
6 20 22 35 30 33 35 38 37
Baked products Rolls White bread Crisp bread Zwieback Rich tea biscuit
0.5 1.2 1.5 4 11
Spaghetti . _
1.2
sweets Sugar Caramel Cocoa (slightly defatted) Milk chocolate
Milk products
0 10 25
Yogurt, skim Condensed milk Cream (whippable)
0.1 4-8 27-33
33
Quark Fresh cheese Camembert cheese Edam cheese Parmesan cheese Emmenthal cheese Roquefort cheese Processed cheese
5-1 2 5-1 2 23 24 26 30 32 2 3-2 8
Cereal products Oat flakes Wheat bran Wheat flour Rye flour Corn flour Corn semolina Corn flakes Pop corn
6.5 10
1-2 1 -2 2.6 1.1 0.4 5
Snacks Potato chips Roasted peanuts
(W
(Oh)
40 48
Miscellaneous ~~~~
~
Mustard Salad mayonnaise Mayonnaise Margarine Butter Cod-liver oil
'?his analysis is from European f d ; all values are examples only and may differ from country to country according to local habits, local taste and local legislation.
World
fat production [MMT] 120 100
population [billion] 12
'
8060 -
40 -. World population
__
20 01936
194S
1956
1966
197s
1986
~
1 ' 1996
Fig. 1.1. Growth of world population and oilhat production.
2
0
6 52 82.5 80.5 82.5 99.8
7
Importance of Fats _.
Germany
us.
\
Gross National Product [lo00US$ per capita] Fig. 1.2. Average spending power and fat consumption in different countries (adapted from Leonhard 1995).
tions grow, but it can be predicted that a tremendous demand for fats and oils will be triggered as their gross national product improves. Statistics concerning the world production of oils and fats have existed only since 1942. Estimations at that time, as well as those concerning the years before, were coordinated by the International Agrarian Institute in Rome (today FAO; Schiittauf 1942). Since then, there has been a shift from animal to vegetable fats (Fig. 1.3). As for all food, consumer prices for oils and fats have dropped signfi-
Marine oils Lard, Tallow Butter Pulp oils Seed oils
Fig. 1.3. Proportion of different oil sources on the world fat production.
8
Fats and Oils Handbook
TABLE 1.3 Oil Seed and Oil Fruit Production in the World by Region (O/O of total) Region North America South America China India, Pakistan, Bangladesh USSR (successor states) Europe (without USSR) Africa Malaysia, Philippines, Indonesia All others
1935
1950
1960
1970
1980
1990
1995
17 7 15 11 9 21 7 6 7
24 8 13 9 8 18 8 7 5
24 9 9 9 9 19 9 6 6
27
28 11 7 8 1 15 6 9 6
26 12 9 6 1 0 9 15 5 13 5
24 13 12 1 4 14 4 14 4
10
7 8 1
2 17 7 5 7
cantly in relation to income. Rendered animal fats, and especially butter, were goods in short supply and thus very expensive. For example, in Germany in 1857, -15% of one’s daily food expense was needed to buy only 40 g of butter. In 1800, the entire expenditure for food amounted to -70% of a family’s entire income, in 1900 to -50% and in 1974 to -28%. Today in Western Europe, this fraction is clearly ~ 2 5 %(Gander 1984). The importance of oils and fats has increased during the past 100 years. Since the time before World War I, worldwide production has more than quintupled. The center of oil fruit cultivation was once situated in tropic regions, whereas today it is in temperate latitudes (Table 1.3). To counteract this trend, tropical countries, in particular, Malaysia, Indonesia and the Philippines strive hard to regain their former rank on the scale of producers. On the one hand, it allows them to feed their own growing population; on the other hand, it creates export possibilities and explains why the production of palm oil in these countries has been extended steadily and forcefully for about 15 years. The higher oil yields of cloned palms contributed to this in part. In Malaysia, production rose from 4 million ton in 1985, to -7 million ton in 1990 and to -10 million ton in 1995 (see Chapter 4.2.1). In that country alone, almost two million people make a living from palm oil, and in 1986, this branch of the industry yielded a revenue of almost $1.4 billion (US.). At the same time, these efforts are a prime example of the importance of oils and fats to certain regions of the world. Often, one region’s efforts to raise production are accompanied by countermeasures from another region. In the case of Malaysia, the countermeasure was an attempt to discredit tropic oils. The increase in the production of palm oil was regarded by the U.S. as a danger to its soybean oil market. Campaigns were started with the objective of pushing the tropic oils out of the country as completely as possible. In addition, new directives concerning labeling were passed, forcing the producers to declare the oils used. Public health policy was given as a reason; later, this proved to be true to some extent but that explanation was viewed by Malaysia as simply a pretext. Malaysia believed that concern about losses suffered in the production of soy seed
lmportance of Fats
9
was the actual reason (Anonymous 1987). After fractionation, palm olein is a good raw material (see also Chapter 1.4), and for many products and branches of industry, stearin is also used as a consistent fat. It is expected that the U.S. import of tropic fats will level off at -750,000 ton per year. Of the laurics (coconut and palm kernel oil), 70% go to oleochemical processing. The distribution of the individual types of oil fruit has changed considerably (Fig. 1.4) as shown by the comparison of their distribution in 1935, 1960, and 1995. A projection to the year 2000 (data from Mielke 1994) is also given. Figures 1.5-1.7 show the production of oils and fats during the last 80 years. The figures refer to the amounts of visible fats produced. A distinction must be made between butter, lard, and olive oil, which represent end products suitable for consumption (Fig. l S ) , vegetable oils and fats (Fig. 1.6), which have to be processed, and oils utilized mainly in industry (Fig. 1.7). To simplify the presentation, tallow, and fish oil, which are generally processed further, are listed together with butter, lard, and olive oil which are consumed as such. Figure 1.5 shows that the production of whale oil has virtually disappeared, whereas the production of fish oil is -10 times higher now. This can be attributed
(C = Corn oil; P = Palm kernel oil; S = Sesame seed oil)
Fig. 1.4. Proportion of different vegetable oil sources on the world fat
10
Fats and Oils Handbook
Fig. 1.5. World production of butter, lard, beef tallow, fish oil, and whale oil. mainly to various new catching methods. However, a stagnation of these figures has to be anticipated, also caused by international campaigns toward sustainable fishing. The high increase in tallow production mirrors the rise in beef production. The growth rates, however, are far lower than those of vegetable fats and oils; tallow is only a by-product. The rapid rise in the production of soybeans, which has increased 50-fold, is clearly visible. The growth rate of sunflower seed is even higher. Compared with these amounts, the production of oil-bearing plants utilized mainly in industry is modest; however, the fact that a considerable amount of the edible oils is used for industrial purposes must be noted (see Chapter 1.6). By looking at the production of fat and its products, the political development in the world or in particular countries can easily be inferred. Fat production in Germany (see Chapter 1.3.1), for example, was at its lowest level during both World Wars, but also during the great depression in the 1920s and 1930s. For a good supply at low prices and, related to that, an adequate profit for the farmer, the yield per hectare is essential because in the industrial nations only a high yield per hectare promises sufficient returns. However, during times of extensive shutdowns of areas (e.g., the US.),there are considerations if models exist that are based on less intensive tillage. The yield per hectare thus keeps rising, but at a far slower pace (Fig. 1.8). It is the yields per hectare that indicate the difference between developing and industrialized countries. Cultivation in Third World countries often takes place on very small farms in poor soil with an insufficient supply of water; for particular regions and their state of affairs, this clearly makes sense. Production in the industrialized countries can vary greatly as well (Fig. 1.9). Consider this comparison. By feeding cows the yield of 1 hectare (2000-3000 kg on average), only 2W300 kg of milk fat can be produced. Of course, one must
11
Importance of Fats
Soybean oil Palm oil
Rapeseed oil Sunflower seed oil
Cottonseed oil Peanut oil Coconut oil
Sesame seed oil Olive oil
Fig. 1.6. World production of important vegetable oils.
admit that, for milk, the production of fat is not the main objective. However, byproducts are also gained from most sorts of oil fruit. Not all influences on production can be controlled even when the means are available. The source of raw materials might be exhausted without the possibility of exercising any influence on it, or the opposite may be the case. For example, the production of fish oil in Peru (one of the largest producers, and for its size, by far the largest producer) decreased from 3 11,OOO ton year in 1976 to virtually zero in 1984. Excessive fishing was not the cause, as was speculated initially, but rather a change in the direction of the Humboldt stream, which shifted its flow 350 km to
Fats and Oils Handbook
12
1.5
E r 1.0 C
5 0
ze
Linseed oil Castor bean oil
10.5
P
Tung oil Sperm oil
0 1910
1930
1960
1970
19SO
Fig. 1.7. World production of main vegetable oils for industrial usage.
the west of the Peruvian coast. The fish followed the flow of the stream. The Peruvian boats, equipped for inshore fishing only, were not able to follow the stream, and the entire industry broke down completely. Chile profited from this: its catches in 1989 amounted to -6 million ton and -260,000 ton of fish oil were derived from it.
Fig. 1.8. Production yields of some selected vegetable oils.
Importance of Fats
13
Fig. 1.9. Production yield of some oilseeds in different countries.
The opposite occurred in the insular republics of South East Asia. There, devastating typhoons had gravely affected the coconut crop over many years. Without any identifiable reason, the typhoons changed direction, and the coconut industry began prospering again. World affairs interfere considerably with the production of oil but in different ways than the natural influences listed above. Their influence on oil prices is especially evident (Figs. 1.10 and 1.11). Wars, but also energy crises are mirrored here, although the supply of edible oil has hardly any relation to the production of mineral oil. Depending on the type, the price of vegetable oils is higher or lower than that of soybean oil, whereas the market value of animal fats lies, without exception, below that of soybean oil. However, it must be considered that fish oil, with very few exceptions, is used primarily in hardened form, so that in comparison with tallow and lard, the costs for hardening have to be taken into account. Tallow is usually fractionated before use. Because soybean oil has developed into the predominant oil, the prices of the other oils are to a certain extent dependent on that of soybean oil (Figs. 1.12 and 1.13). These figures show prices leveling off in years when edible oils strongly forced their way into the market and the difference in price for soybean oil, which has been relatively constant (except for some peaks). They also give an idea of the relative value of the various oils and fats. Considering the large volumes of oil produced, the high growth rates and the competitive situation, it is no surprise that oil prices have declined relatively. Depicted in U.S. $ against inflation in the U.S., it becomes obvious that oil prices
Fats and Oils Handbook
14
L I S M 1970 1975 1980 IS85 I990 1-
I I
1065 1970 1975 1980 1985 1990 1096
1400
1200
lo00
800
600400 200 Palm oil
0 1 1966
1970
1976
l&
1986
l&
l&
Fig. 1.10. World market prices of important vegetable oils.
in January 1990, in spite of the increase of the absolute amount in constant money, are only -36% of those in January 1965. During 1987, they dropped temporarily to only 25% of 1965 levels (Fig. 1.14). Taking into account the decline of the U.S. $ in proportion to the currencies of some European countries, the oil has become even cheaper. However, this is compensated partially by lower inflation rates (Figs. 1.15 and 1.24). Because of the historical development of the production of oil fruits in regions completely different from those in which they are consumed, the market has always been international. Oilseeds and oil are usually traded in U.S. $. Because
15
Importance of Fats
1200
Soybean oil
400
1985
1400
1970 1975 lSe0 1985 1990 1995
1985 1970 1975 1980 1985
lee0 1995
World market pnce [US. WMT]
1200 lo00
800
Ittoned oil
800 400 200
Soybean oil 0 '
1
19S5
I
1970
1975
IS60
1985
ID00
1996
Fig. 1.lo. Continued.
the European countries are not self-sufficient, they have to import oilseeds. For the oil milling industry outside of the U.S., which has to commercialize oil as well as meal, the deviation of the exchange rate of the U.S. $ to the respective currency (Fig. 1.15) is added to the deviation of the price for the raw material. This can exert quite a considerable influence on the market position because products made from vegetable oils and fats always compete with indigenous products (e.g., margarine with butter). In addition, extraction meals have to compete with indigenous fodder. The influence of the deviation of the U.S. $ exchange rates against the only stable European currency (German Mark) is made clear. One realizes that the deviation for the European
Fats and Oils Handbook
16
Edible Tallow
1965
1970 1975 1980 1985 1990 1995
1W5
1970 1975 1980 1985 1 W 1995
World market price [US. WMTJ I2Oo
I
1000
800
600
400
200 -.
0 ’
I
igss
1970
197s
is80
198s
isso
,
ims
Fig. 1.1 1. World market price of some animal fats (soybean oil as comparison).
market can thereby become even larger. In times of a powerful dollar, considerable price discrepancies arise that are difficult to pass on to the customer. Prices on the world market do not always depend on supply and demand alone, but also on expectations for the volume of the next harvest. Most deals are closed on futures long before the harvest amount is known. Besides the area that is going to be cultivated in the respective year, information about the expected weather is relevant. However, not even a major regional weather-related catastrophe would be capable of influencing prices substantially. The U.S. exhibits the greatest deviations in the area used for cultivation and thus the strongest influence
Importance of Fats
440
17
World market pnce dfference to soybcen 011 [US$/MT]
300
zoo
loo 0 -100
-100
300 400 1066
1970
1976
1980
1986
1990
1996
World market pnce dfference to soybean oil [US. $IMTl
Peanut oil
400
300
'
1066
1970
1976
1980
1966
1990
1996
Fig. 1.12. World market price difference of some vegetable oils and fats to the price of soybean oil.
on the amount of crop to be expected. According to the previous year's supply and achieved prices, areas of smaller or larger size will be shut down. Because soybean oil is by far the most-produced oil, its quantity influences the prices of the other oils and fats as well. Consequently, the number of acres cultivated in the U.S. in the respective year plays a very important role in the equation. During times of high supply, prices usually drop at harvest time and rise when the provisions run short. During this process, the quality usually declines as well; therefore Brazilian and Argentinean producers generally wait until the supply of the crop in the Northern hemisphere is exhausted, or the quality declines, before they commercial-
18
Fats and Oils Handbook
Fig. 1.13. World market price difference of some animal fats to the price of soybean oil. ize their crop. This is the only way to obtain good prices for relatively smaller producers with higher transportation costs. As a result of intensified cultivation in the Southern hemisphere, fresh soybeans are available twice a year. Apart from production and availability, demand also plays a decisive role in price. When comparing demand with availability, we see that the quantities pro-
Fig. 1.14. Price of soybean oil in current and constant money (US $).
Importance of Fats
19
Fig. 1.15. Price of soybean oil in U.S. $ and in a stable European currency (DM).
duced were almost without exception higher than the demand (Fig. 1.16). This leads to an accumulation, which depresses the prices. Malaysia alone is said to have had a stock of palm oil of -1 million ton in 1988-1989. The econoinic situation in the large countries that are not self-sufficient and are subject to monetary problems is closely linked to demand, and thus to a high
Fig. 1.16. Demand and supply balance for vegetable oils and fats (after Batterby).
Fats and Oils Handbook
20
degree, decisive for price development. On the one hand, there is the Soviet Union (respectively, the successor states), where the import of meals as fodder plays an important role. On the other hand, there is India, which represents a huge market with 9300 million people. In 1986-1987, -2 million ton of oils and fats were imported. The imports in the following years are estimated to be -0.5 million ton, but the most recent estimates suggest even lower amounts; however, the demand that cannot be met that way amounts to 1 million ton per year. In contrast to this, it is expected that Pakistan will increase its imports to almost 1 million ton. In view of these markets, the surplus production is within the range of the deviations of the quantities imported by these countries. The demands are thus not regulated by the actual demands, but by the availability of funds. When we relate the prices for oilseeds on the world market to those for oil, we have to consider that they are determined by the oil content as well as by the usability of the meal as fodder. We see that an intricate web of influences exists that determines the prices. This has direct influence on the supply, more so in some parts of the industrialized countries in which the price for seeds fluctuates around the limit of profitability despite subsidies. Without subsidies, production at today’s prices would not be possible. For the oil mills, the production of soy seed, for example, means that they have the following net profits (Prices Chicago, May 1990): Cost (US. $) lo00 kg 180-200 kg 820-800 kg
soybeans oil extraction meal
Cost of beans Gross profit from oil and meal*
Revenue (U.S. $)
322.12 193.68-2 15.20 134.55-13 1.27 322.12 328.23-336.47
*without any running and processing cost, without losses and depending on the oil content.
This margin (however simplistically calculated) is extremely small for a capital-intensive industry such as oil milling, so that small changes in the meal’s marketability or in the price would render the entire enterprise uneconomical. The economic importance of a raw material, however, reveals itself not only in the supply, but also in the demand. Because oils are traded internationally, their prices are not dependent on the demand in a single country. In addition, there are subsidies for agriculture in many regions. This has repeatedly given rise to international irritations when, for example, the U.S. reproached the European Community for violating the GATT-treaty by means of subsidies and by partially barring the market for agricultural imports (see Chapter 1.3.2). From Brussels’ point of view, these subsidies are necessary to assure some degree of self-supply for certain agricultural goods of the European Community.
lmportance of Fats
21
Subsidies can have other purposes, for example, as an incentive for structural reorganization. For instance, the Community supported the shift from the cultivation of rape with a high content of erucic acid (HEAR) to that with a low one (LEAR). It was intended to arouse the farmers’ interest in rape, which grows well in temperate climates, and to promote its cultivation instead of root crops and cereals, which are produced in excess. In 1988, the subsidy was 5.90 German marks (-3.30 U.S. $) per ton of rape (LEAR). The prices the producer can gain for his products on the market, however, are dependent on the demand in an individual country. In this respect, the price structure of butter and margarine in the individual countries is of interest. In some countries, for a large part of the population, margarine is a substitute for butter. The sales thus depend to a high degree on the relation between the prices for butter and margarine (Fig. 1.17). In Germany, for example, a portion of the consumers buy margarine whenever the price differential to butter increases beyond a certain value. This fact, which applies to other countries as well, was used by the EC-commission to diminish the “butter-mountain” by bringing butter onto the market at a reduced price. In the period from 1982 to 1985, heavily subsidized butter in the EC amounted to >2.2 million ton. To subsidize this quantity, which replaced 80% of the fresh butter, 1600 ECU per ton had to be paid (>3200 German marks or 1500 U.S. $ per ton at the exchange rates of 1986; Friedeberg 1986). In other countries, the image of margarine is completely different, and butter plays only a minor role. Interestingly, this also applies to the Netherlands and Denmark (buttedmargarine 1:7 and 1:3, respectively), countries that are commonly known as “milk countries.” 10
a
8
g
6
Butter
Vegetable
I
2 k
p.. margarine
Butter
4
.-8
Average margarine price
ti
2
0
,
i
I910
4
1930
I
,
1950
1970
1990
Fig. 1.17. Price differential of margarine and butter in Germany.
Fats and Oils Handbook
22
1.3.1 The Economic Importance of Oils and Fats as Well as of Fat Products in Europe and Germany
As stated in the preface, Germany is seen as a particular example of a western European country. In the past 50 years, nutrition habits in industrialized countries have changed drastically (Fig. 1.18), with Germany as an example. (Remark: all data in figures concerning Germany end with the year 1990 because data after the reunification would not be comparable.) In spite of diminishing hard physical labor, caloric intake has grown, and despite the findings and recommendations of nutritionists, the percentage of fat in the diet has increased. Since 1850, the consumption of fat in industrialized countries has risen constantly. It is assumed that the German population satisfies -40% of its energy demand with fats and oils. Currently, the amounts consumed consist of approximately equal shares of butter, margarine, and edible oil, as well as tallow and lard (Fig. 1.19). The proportion of margarine has dropped since the 1950s in favor of edible oil and fat. The market for emulsion fats altogether is currently dropping at a rate of -3% per year. The shift in proportions is disadvantageous for the visible fats, whose proportion or intake can be controlled consciously, and favors the invisible fats (proportion -1: I). Currently, the annual per capita consumption amounts to -30 kg of visible fats (Fig. 1.20). The history of fat policy in Germany (which is representative of other European countries) is depicted comprehensively by Schtittauf and Pischel(1978), whose work is referred to in part in the following paragraphs. Their overview reflects the political turmoil in Europe during the last 80 years. 200
0
I
6
eh)r
1940
I
w
* &--" #*-
1980
. .us*m --m -
1960
1970
1980
1990
Fig. 1.18. Per capita consumption of different food in Germany
Importance of Fats
23
Fig. 1.19. Proportion of some fats and oils on total fat intake.
Today, Germany’s self-sufficiency concerning vegetable oils and fats is quite low. About 90% of the raw materials are imported. In the early 1900s, Germany’s self-sufficiency for fats and oils was -50%; between 1945 and the present time, the overall self-sufficiency is -40%. Despite these shortcomings, there have always been attempts to impose special taxes on the import of oils and fats (fat-tax). Actually, this tax has never been directed against the fats themselves, but against fat products, especially margarine.
Fig. 1.20. Per capita consumption of visible oils and fats in Germany.
24
Fats and Oils Handbook
Toward the end of the last century, with the introduction of margarine, the first legal restraints were introduced; initially, these amounted only to sale restraints (e.g., no butter and margarine in the same room). However, a duty was imposed on the import of margarine or equivalent oil mixtures according to Bismarck’s policy of protective duties. Because this duty did not apply to individual oils but only to oil compounds or to finished products such as margarine, the first margarine plants were built directly along the border in The Netherlands, which were most progressive, so that transportation costs for the duty-free raw materials were as low as possible. During World War I, a considerable shortage of fat occurred. Naturally, imported fats and oils became scarce first, so that fats for margarine were not available in sufficient quantity. From 1917 on, only one third of the required volume of fat could be put on the market. In the respective figures, this becomes apparent through the lows in margarine production, and better yet, in the contrary development of the fraction of margarine and butter at that time. During the time of inflation, caused by the putative upswing during the postwar period, the number of margarine plants in Germany rose to several hundred (today the number is -10). On May 1, 1933, a fat-tax, combined with a fixing of quotas, came into effect in the Third Reich. The production of margarine was frozen at 60% of the 4thquarter output of 1932; moreover, a tax of 0.50 Reichsmark per kilogram of margarine, edible oil, hardened vegetable oil and whale oil was inflicted. An “Agency of the Reich for milk products, oils, and fats” was established. Soon, only a standardized margarine, packed in a simple, brown, unattractive wrapper was permitted to be marketed. As a consequence, 115 out of 148 margarine plants were forced to close. It was not until 1949 that branded margarine products were again permitted to be sold. However, at about the same time, the oil milling industry was financially hard hit because it was forced to sell to the agriculture sector meal at 50% of the world market prices. A fat-tax was again considered in 1950. It was prevented by protests from labor unions and social associations. Instead of the fat-tax, vegetable oils and fats were subsidized through the end of the Korean War. In later years, the fat-tax was considered several times, mainly during the times when there was an excess of butter, the so-called butter mountain, in the European Community. The fat-tax was consistently prevented. The primary reasons for the failure of the fat-tax included strong protests from consumer groups who feared higher prices. Another reason for the failure of the fat-tax was intervention by the U.S. (different reason than before), who did not want to see its export of soy products diminish because of the enormous rise in U.S. soybean production. At that time, the American soy farmers were feeling the effects of poor prices for their crop. Finally, this would have been the first tax that the EC could have inflicted, and increased independently from the individual governments. The EC certainly needed the revenues because subsidies of other agricultural products amounted to several hundred per cent (i.e., in 1977,220% for butter and 107% for olive oil).
Importance of Fats
25
The prices for fats and oils in Germany (as in other European countries with hard currency) in terms of constant money have developed differently from those in the U.S. Two opposing influences are operating here, i.e., the substantially lower inflation rate in Germany compared with that of the U.S. (over a period of 30 years from 1965 to 1995, only -56% of the U.S. rate) and the depreciation of the U S . $ with respect to the German mark (from 1965 to 1990, -45%). The effect is clearly visible in Figure 1.21. Presenting the price for soy on the world market in U.S. S as well as in German marks, according to the respective exchange rate and with an adjustment for inflation, one can see that soybean oil in Germany in terms of constant money costs only -30% of the amount in 1965 (U.S.: 36%; Fig, 1.21). This is reflected in the consumer prices for oils and products consisting mainly of oils and illustrates some of the problems of the fats and oil industry as a whole. After the reduction of the butter-mountain, which had temporarily reached >1.4 million ton, by means of regulative measures by the EC (quotas for milk), a certain pressure to intervene for regulating purposes has subsided. The next decisive step will be the integration of the different forms of agricultural producers in the new and old federal states of Germany into an all-German system. In the new states, a potential for the production of oilseeds is building up; in relation to the population, it is larger than that in pre-unification Germany. The European Union will be faced with the same problem when considering the membership of Eastern European countries such as Poland. Figures 1.22 and 1.23 reflect the situation in the German oil milling industry, which crushes about two thirds of the oil consumed. The development of the amounts of oil produced per variety reflects the European Union’s move towards rape and sunflower, and the crushings demonstrate the dominance of these two
Fig. 1.21. Price of soybean oil in current U.S. $, and current and constant DM.
Fats and Oils Handbook
26 I.o
I
0.8-
Er 0.6 -.-
0
0
3
Rapeseed oil
//I Palm kernel oil
Soybean oil
Oa4
T Peanut oil
\
I+
coconut oil
0.2
Sunflower seed oil
0 I910
1925
1940
1956
1970
1985
Fig. 1.22. Oil produced in German oil mills.
oilseeds over soybeans. Although more southern countries such as France are crushing relatively more domestically grown sunflower seed, this picture can be regarded as typical for Western Europe. In spite of the difficulties with eamings and profits and the strong competition from abroad, the quantities processed increased until 1980 and have since remained
r-
6
5
€ 4
f . P i
e
seeds (total)
Meals (total)
Soybeans Rapeseed Soy meal
2
a
Oil (total)
I
0 1910
1925
1940
1956
1970
1985
Fig. 1.23. Seed processed in German oil mills.
Importance of Fats
27
relatively stable. This is partly a result of the trend to move the mills closer to the large sea harbors, such as Rotterdam in The Netherlands. The quantity of extracted oil has increased because the oil content of rapeseed is higher than that of soybeans. In the processing of soft seeds (rape/sunflower), the Central European mills will thus have greater chances of competition than in crushing soybeans. 1.3.2 Oil Politics in the European Community
At the time when the guidelines of the EC-agricultural policy, which also encompasses the production of oil, were laid down, the degree of self-supply for vegetable oils (except olive oil, which is regulated separately) was ~ 1 0 % and that of vegetable proteins 4%. In the course of the past years, this figure has risen to >50% for vegetable oils (Fig. 1.24). Certain types (rapeseed, sunflower seed) are even exported (Friedeberg 1989). The production is subsidized and protected by duties; in 1962, the EC committed itself in the Dillon-round of the GATT-treaty to not raise the duties on oilseeds, oils, and meals. The subsidies rose from -0.1 billion ECU in 1977 to -3 billion ECU per year in 1988 and have remained on this level. Subsidies were granted without limits on volumes and represented the difference between a representative price on the world market and a desired price (both fixed by the EC-commission for one year). The subsidies are paid via the oil mills. As mentioned above, there are no limits on the acreage and the quantity produced and thus no limits on the total amount of subsidies for an individual producer or, equally, the EC. By changing the targeted price, an incentive to produce oil fruit was
Fig. 1.24. Production of soybeans, rapeseed, and sunflower seed in the European Union.
Fats and Oils Handbook
28
TABLE 1.4 Fatty Acid Composition of Fat in Human Adipose Tissuea and Difference in the Composition of Serum Lipid Extract of Vegetarians and Nonvegetariansb Fatty acid in fat of adipose tissue
(%)
Palmitic Palmitoleic Stearic Oleic Linoleic
25 7 6 45 8
-
All others
9
Vegetarians
Nonvegetarians
Fatty acid (YO) in serum lipids
1982
1986
1982
1986
Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Arachidonic All others
20.1 3 .O 6.3 19.2 36.5 1.5 5.9 7.5
20.7 3.4 6.6 19.1 34.5 1.1 5.6 9.0
21.1 3.4 6.4 22.3 30.9 1.1 6.3 8.5
22.5 3.7 6.3 22.4 28.4 0.9 5.8 10.0
aSource: Ceigy. bSource: Melchert (1988).
created that led to the explosion of quantities as illustrated above. Friedeberg assumed two motives by the EC-commission for this policy. On the one hand, there was the uneasiness in being dependent on others (low degree of self-supply), supported by a very brief embargo on soybeans by the U.S. in 1973; on the other hand, there was the attempt to reduce the weight of the subsidies on grains, which oppressed the Community’s budget. By means of this policy, the support for the production of oilseeds became the third highest item in the EC’s agricultural expenses. The mawtude of the subsidies unduly burdens both the budget and the relationships to nations TABLE 1.5 Cholesterol Content of Food Food Vegetable oildfats Fish oils Lard Milk Milk powder Butter Milk fat Pork (lean, U.S., UK) Pork (+ fat, U.S., UK) Beef (lean, U.S., UK) Beef (+ fat, US., UK) Calf‘s liver Finfish, low fat Finfish, high fat Shellfish, crustaceans E!% Egg yo1k
Cholesterol (ppm) <50 5000-8000 9 80 120 960 2 800 -3400 >59C-670 >650-710 >650-710 720 4900 470-570 590-790 860-1 200 41 0 16,000-1 7,500
Reference %her 1987 Tucker 1993 Seher 1987 Taufel 1993 Taufel 1993 Taufel 1993 Taufel 1993 Larnbert 1993 Larnbert 1993 Lambert 1993 Lambert 1993 Seher 1987 Childs 1993 Childs 1993 Childs 1993 Taufel 1993 Stadelman 1993
lmportance of Fats
29
with large agricultural exports. In 1988, the U.S. issued a fonnal complaint for the first time concerning the violation of GAIT. As a mechanism of stabilization, the commission proposed a fat-tax, which created quite a stir internationally and provoked the U.S. to threaten counteraction. After great protests by most trading partners as well as by many organizations within the EC, the plans were suspended for the time being. Subsequently, the EC searched for alternative solutions and found a system of “stabilizers,” the elucidation of which would be beyond the scope of this book. It is doubtful that this system will lead to the desired outcome. It is also uncertain how these regulations can be made compatible with Article 110 of the EC-treaty, which states that the aim of the EC’s trade policy is to contribute to the general well being through the following: a harmonic development of world commerce, the progressive lifting of barriers in international trade and the reduction of customs barriers. It is certain that the problems cannot easily be solved, but do seriously threaten the budget. In particular, it is difficiult to make compatible the aims of the EC’s agricultural policy according to Article 39; these include a sufficient income for the farmer, stable (internal) markets, reasonable consumer prices, increased productivity, and a secure supply.
1.4 Fat in Nutrition As previously mentioned, fat serves mankind as an energy supply, a reserve of energy, makes possible the intake of vital fat-soluble substances and supplies the body with essential fatty acids. The fat content of the human body is 16%in the embryo, with an adult body consisting of approximately the same percentage; deviations range from 8 to 50% (FriisHansen 1965). Fat is stored mainly subcutaneously and in the muscular tissue, as well as in deposits surrounding the inner organs such as the heart, kidneys, and intestines. In addition to its function as a quickly activated energy source,the subcutaneously deposited fat also serves as an insulating layer against hypothenria; the fat tissue surrounding the inner organs serves as a protective pad against physical injuries. The body can synthesize fat in part from carbohydrates, but to a large extent it is conveyed with food. The amount of fat in the diet cannot be precisely defined because of the influence of general living conditions (Gottenbos 1985 and 1988). Certain fat components, the essential fatty acids, are vital and must be supplied from outside. They are essential components of the cell membrane structure. Their metabolism is well known (Table 1.6; see Numa 1984, for example) leading to precursors of so-called eicosanoids that influence the behavior of the cell and are important for activities such as proper cholesterol transport. Fat conveyed with food passes through the stomach, is emulsified in the intestine by gall bladder secretions and is then hydrolized by lipases (pancrease), which are the enzymes of the intestine and the pancreas. The lipases present in the stom-
Fats and Oils Handbook
30
TABLE 1.6 Metabolism of Essential Fatty Acids Effect
Enzyme working
a-Linolenic acid ALA (18:3w3)
Linoleic acid (18:2w6) A6-Desaturase
.1
-2 H
Elongase
1
+2c
-1
-2 H
I
+2c
I Docosaheptaenoic acid DPA (22:5@6)
1 Docosa heptaenoic acid DPA (22:5w3j
Adrenic acid ADA (22:4w6) A4-Desaturase
I Eicosapentaenoic acid EPA (20:5w3)
Arachidonic acid AA (20:4w6) Elongase
1 Eicosatetraenoic acid (20:4w3)
Dihomo-y-linolenic acid DGLA (20:3w6) As-Desaturase
1 Stearidonic acid (18:403)
y-Linolenic acid GLA (18:3w6)
-2 H
1 Docosahexaenoic acid DHA (22:6w3j
ach separate fat that is hulled in protein from its protein hull. Hydrolysis is continued in the duodenum to yield ~ 1 0 % of triglycerides and diglycerides as well as 40-50% of monoglycerides, 40-50% of free fatty acids and glycerol. In the first 100 cm of the small intestine, the oily solution of triglycerides and phospholipids (chylomikrons) with a droplet diameter of 0.5 pm exists alongside the microchylons (0.05 pm), which consist of mono- and diglycerides and salts of gall acids. These are further broken down into the micellar fraction consisting of monoglycerides, fatty acids and gall acids. The particle size has then reached -0.005 pm, which is sufficiently small to pass through the intestinal wall. Passage is possible for particles smaller than 0.01 pm (Ludwig 1968). The fat is reconstituted after its components have passed through the intestinal wall (Langdon and Phillips 1961). Short-chain fatty acids can pass through the intestinal wall more easily; however, this is not of importance for healthy people (cf. also Chapter 8.8). The fat enters the body via the lymphatic system, and any unneeded surplus is stored in fat deposits; the remainder is conveyed to the liver metabolism. Fats with melting points 4 0 ° C are virtually completely digestible. For additional information on the metabolism see, for example, Welch (1993). For the nutrition physiology of fats, unsaturated fatty acids are especially important (Hunter 1989). They consist of three families and are characterized by the position of the first double bond of the fatty acid chain, counted from the methyl group. An n-x fatty acid has its first double bond between the xth and x + 1 C-atom of the chain counted from the end. The next double bond is usually situated three C-atoms further along the chain. Representatives of the three main groups are as follows:
Importance of Fats
n-3 linolenic acid n-6 linoleic acid n-9 oleic acid, erucic acid
31
(also 0-3) (also 0-6) (also 0-9)
The hydrolysis of fats is performed by the same enzyme irrespective of the fatty acids. Among unsaturated fatty acids, the enzyme has its highest activity for n-3 fatty acids. In the reesterification after passing through the intestinal wall, the composition of the triglycerides in relation to fat taken in with the food is changed because fats stored in different regions of the body exhibit typical fatty acids patterns. Their composition is relatively constant but can be changed by very unbalanced nutrition or high doses of fat. Human adipose tissue is composed essentially of only five fatty acids (Table 1.4). A considerable portion of linoleic acid must be accumulated in the body because linoleic acid, as an essential fatty acid, cannot be synthesized. The difference becomes visible when comparing the relative fatty acid composition of fat in vegetarians with that in nonvegetarians (Table 1.4). Mammals have the ability to convert saturated fatty acids, but only into those that are monounsaturated, with the location of the double bond only at C-9 (Thiele 1982). This chain can be prolonged toward the carboxyl-end, but not toward the methyl-end. Thus, the synthesis of linoleic acid is not possible in animal organisms (cf Chapter 2.1). In addition to linoleic acid, arachidonic acid (formerly called vitamin F; AaesJorgensen 1961) is also regarded as an essential fatty acid. For about 60 years, it has been known that these two fatty acids are vital (Burr and Burr 1929); for example, they comprise the initial stages of prostaglandins (Bergstrom and Samuelson 1965). Prostaglandins were discovered in sperm by von Euler in 1934, but they are present throughout the body. They are the building blocks of hormones and possess their own physiologic activity as well (hypotensive activity, stimulation of the sleek muscles, regulation of the release of fatty acid from fats). Moreover, essential fatty acids are necessary for growth, contribute substantially to the building of cell walls, and form a structurally essential component of phospholipids. They occur mainly in the brain and nerves and participate in many metabolic processes including those of mitochondria. If the supply of essential fatty acids is insufficient, other nonessential ones are built into cell walls, leading to disorders. Among others, Hansen et al. (1958), Thomasson (1953), Holman (1961), Holman et al. (1964), Aaes-Jorgensen (1966) and Vles and Gottenbos (1989) reported such deficiency symptoms. A deficit of essential fatty acids can result, for example, in reduced growth, lowered prostagladin synthesis and skin damage. The symp toms disappear or come to a halt when n-6 essential fatty acids are supplied. The amount of essential fatty acids (e.g., linoleic or arachidonic acid) that should be present in the diet were previously stated to be at least 2% of the entire calorie supply (Holman 1961), which corresponds to an intake of -2.4 g of linoleic acid4187 kJ (lo00 kcal). The recommendations were developed further, and in more recent recommendations by the FAO/WHO (1977), 3% (corresponding to 3.6 g/4187 kJ or loo0 kcal) is stated as the desirable quantity. This percentage should be increased to
32
Fats and Oils Handbook
during pregnancy and to 5 7 % in the lactation period. According to Adam et a!. (1958), infants should receive twice that amount. Wolfram (1987) surveyed the
metabolic effects of a diet rich in linoleic acid. Another important positive quality of essential fatty acids that is the subject of a growing number of studies is their lipid-lowering quality as well as their ability to exercise a favorable influence on an excessive cholesterol level in the blood. This has a special significance for health issues because both an increased lipid level and an increased cholesterol level are considered to be risk factors for heart attacks. Cardiovascular diseases are the number one causes of death in industrial nations throughout the world. The lowering of lipid levels as a precautionary measure has been known for more than 30 years (Ahrens 1957 and 1959, Groen et al. 1952, Kinsella et al. 1952); although it is undisputed among experts, it is repeatedly attacked by lobbies. Mertz (1983) conducted a survey of the current state of knowledge. These findings on the connection between cholesterol levels and cardiovascular diseases were supported by the awarding of the Nobel Prize for medicine in 1985 to Brown and Goldstein, who were pioneers in the studies on this subject. Arteriosclerosis, caused by cholesterol esters and elevated cholesterol level, has clearly been identified as one of the key risk factors for heart disease (LRCCPT 1984, Schlierf 1986). Today, a distinction is made between LDL (low-density lipoprotein), commonly labeled “bad cholesterol,” and HDL (high-density lipoprotein), which is considered “good cholesterol.” HDL is responsible for transporting surplus cholesterol from the body to the liver. Thus it represents a means of transportation. A high level of LDL is directly related to heart disorders. A survey of the influence of nutrition was given by Schettler (1984). The lowering of the cholesterol level is due to the direct supply of linoleic acid and to its relative quantity in the fat. Stamler (1966) showed that when raising the intake of polyunsaturated fatty acids from 9 to 15%, the amount of cholesterol in the blood serum decreases by only 1.2 mg/mL. When the supply of saturated fatty acids is reduced from 16 to 9%, which indirectly results in a relative increase in polyunsaturated fatty acids, the amount of cholesterol in the blood serum drops by 1.9 mg/mL. The fundamental factor is not the amount per se of polyunsaturated fatty acids, but the proportion between them and the saturated fatty acids. This proportion is also called the P/S ratio (P = polyunsaturated fatty acids, S = saturated fatty acids). According to Mertz (1983), the P/S factor in the food of the German population was 0.39. This is far below the desirable ratio of 1:1 (P/S = 1). As a consequence (e.g., for diet margarine), the legislature will probably abandon the exclusive specification of the content of linoleic acid in the declaration of diet products and require in the future that the portion of saturated fatty acids or the P/S quotient be stated. It is doubtful that reaching the positive effects of a higher P/S ratio as stated above through increasing the supply of linoleic acid to the diet will be achieved, especially considering the rivalry between margarine and butter. This is mainly a problem of agricultural politics (cf. Chapter 1.3) and not one of health politics. The fact that it is not the‘ origin of the fat (vegetable or animal), but rather the P/Sratio that is crucial
lmportance of Fats
33
is often neglected. The P/S ratio of butter is 0.05; that of vegetable coconut fat only 0.02. However, in spite of its vegetable origin, the latter is not considered suitable as an exclusive fat for healthy nutrition. The quantities consumed are low because it is not a basic food but one found only in specialty products. Sunflower oil, on the contrary, is especially suitable (P/S = 5.82;Wirths 1981). Its P/S ratio is so high that the sunflower oil can compensate for higher saturated fatty acid intake in the normal fat supply. More recent analyses led to the recommendation to adjust the proportions of polyunsaturated fatty acids, monounsaturated fatty acids and saturated fatty acids (PUFAIMUFAISAFA) to 1:l:l (MI3 1984). These findings do not call into question prevailing nutrition recommendations regarding linoleic acid as an essential fatty acid. Findings in this area have not changed. However, a stronger positive (lowering) influence of the monounsaturated acids (i.e., predominantly oleic acid) on the cholesterol level than estimated has been found. Oils rich in oleic acid (e.g., rapeseed oil, olive oil) can thus be suitable for a cholesterol-reducing diet as well as those with a high PUFA content (e.g., sunflower oil; see, for example, Laasko et al. 1989). However, because the invisible fats are rich in saturated fatty acids, diet margarines should have a content of saturated fatty acids ~ 2 0 % in order to reach the targeted proportion. Altogether, science today is able to correctly predict the average change of the cholesterol level in the blood when nutrition is changed. Findings to date led the U.S. Federal Health Agency (NIH 1984) to recommend that Americans should reduce their present intake of 40% of calories from fat in their diet to 30%. Moreover, they should limit the intake of saturated fatty acids to ~ 1 0 % of the calorie intake and raise that of polyunsaturated fatty acids to 10%of the calorie intake (but not more). The daily intake of cholesterol should be limited to a maximum of 25&300 mg. The European Consensus-Conference (1986) adopted the American values in their recommendations and added maximum values for the therapy of high-risk persons. (Schwandt 1987). The European Arteriosclerosis Society required further measures (Assmann and Schettler 1987). When examining the cholesterol level, it is essential to take into consideration the intake of the cholesterol itself. An important source is animal products, especially animal fats, which typically contain substantial amounts of cholesterol (Table 1.5). According to a general agreement derived from British legislation, substances with 4 0 ppm are regarded as cholesterol free. Vegetable oils not only have the advantage of reducing cholesterol levels, but they also do not add to the intake of cholesterol (Seher 1987). Thus, with an elevated cholesterol level, nutrition with the correct fat must be balanced with a suitable nutrition plan. Proposals were made to shift the P/S factor in the direction of one, but only sick and high-risk people need to take special care. At present, there are efforts to remove cholesterol from butter to avoid at least one of its detriments (extraction with supercritical COz, Kankare and Antila 1989). The findings in the cholesterol debate were surveyed by Goldberg and Schonfeld (1958), Grundy (1986), and McGandy and Hegsted (1973, among others.
34
Fats and Oils Handbook
Knowledge about the disadvantages of animal fats has continually led to attempts to reduce their presence by changes in animal feed (Leaf and Weber 1988). This applies particularly to the feeding of milk cows. It was possible, for example, to raise the content of n-3 fatty acids in milk fat to 6% by mixing fish oil (Menhaden oil) into the fodder (Hagemester 1989). The passage of the n-3 fatty acids from the fodder to the milk fat was between 35 and 40%. In this special instance, such milk fat is preferred to conventional milk fat from the point of view of nutrition physiology. However, it is uncertain whether it will provide a reasonable alternative considering the conversion factor mentioned above. For about 20 years, nutritionists have concentrated on n-3 fatty acids (a-3 FA), because Bang and Dyersberg (1975) observed that the Greenland Eskimos, in spite of their extensive consumption of fat, suffered less from heart disease than the Danes. Their biochemical values were very close to those of a Japanese population of fishermen, who also subsisted mainly on marine animals (Yamori et al. 1985). The Eskimo diet (marine oils) is rich in n-3 fatty acids. In marine oils, n-3 fatty acids are almost exclusively long-chain acids. It is estimated that the required daily quantity of these fatty acids is 0.2% (Benadt 1988). The daily intake with Western food is -1 g of n-3 fatty acids. Investigations concerning the advantages and possible disadvantages of these acids have not yielded any conclusive results to date and are still in progress. However, studies in Europe indicate (Kromhout et al. 1985, study in Zutphen, The Netherlands) that there is a connection. There appears to be definitive evidence that the daily consumption of n-3 fatty acids must exceed an average of 2 g to achieve an effect (Driss and Darcet 1988); this is equivalent to daily consumption of the relatively high amount of 200 g of fish. Findings are not sufficiently advanced to recommend the intake in concentrated form, e.g., in capsules, or to incorporate such fatty acids into fat products. Moreover, the quantity that would then have to be used to ensure the effect is rather high, although their efficiency is 20 times higher than that of linoleic or linolenic acid (Singer). It is also questionable whether a continuous nourishment with foods rich in n-3 fatty acids could be harmful. A survey of the state of the discussion about fatty acids from fish oils was given by Harris (1989). The concern that polyunsaturated fatty acids may be susceptible to oxidative damage and might develop into carcinogenic substances within the body is repeatedly expressed by scientific outsiders, but is unfounded. Dormandy (1983) determined that in-vivo oxidation of fatty acids does not take place. Within the body, as in the intact seed, they are protected by the body’s antioxidants. The consumption of fats oxidized (peroxides) by inappropriate handling is also not dangerous. Fats containing harmful concentrations of oxidized fatty acids are not edible as a result of their very bad taste. The fat supply itself constitutes another problem. Fat consumption in the industrial nations today satisfies between 35 and 45% of our energy demand, and in the developing countries between 10 and 20%. The worldwide consumption of fat during the mid-1970s was 12.5 kg per capita per year. In Germany, for exam-
lrnportance of Fats
35
ple, more than three times that amount of fat was eaten. The level of fat consumption parallels the rise in standard of living. Thus, the consumption of animal and vegetable fats and oils in the U.S. more than doubled between 1950 and 1985 (Hammond 1988). In contrast with Germany, however, there was a strong shift to vegetable oil consumption. This is disquieting in two respects. As a rule, the intensity of physical labor decreases as the standard of living rises. Recommendations for the daily intake of calories are as follows: 2000kcal 2300 kcal 3200 kcal
(8370k.l) (9620 k.l) (13390 k.l)
for light work, for medium work and for hard work.
This would mean that even a constant consumption of fat would be too high, because surplus energy is conveyed to the body. On the other hand, fat consumption is rising because fat makes food tastier. It is recommended that calorie demands met by fats in the diet range between 25% and a maximum of 35%. Adding to this negative trend is the fact that much of the fat in foods is in the form of hidden fats. Hidden fats are fats contained in other foods and consumed unconsciously. This applies especially to meat, sausage, and cheese (c$ Table 1.2). Studies in the Federal Republic of Germany in 1982 showed that >50% of the fats consumed was in the form of hidden fats. In addition to the fact that the population is not aware of which foods contain what quantities of fat, it becomes increasingly more apparent that the predominant part of hidden fats consists of animal fats with a high proportion of saturated fatty acids. In this manner, the P/S quotient is lowered (which is negative), and no essential fatty acids are consumed. When the calorie supply is reduced, which usually occurs by lowering the amount of visible fats, the negative tendency is further intensified. Attempts to exchange the saturated fats in foods for highly unsaturated ones are constantly thwarted by protectionist legislation (c$ Chapter 1.5). Greater freedom remains unattainable as a result of the harmonization of the respective laws and regulations within the European Union. Besides the fat-associated substances, minor components are important as well. Some of these have negative effects but are found only in the grain; in that case, they cannot be used as feed for all animals. Experiments have shown that gossypol from cottonseed causes pathologic changes in the testicles of mammals that can lead to sterility (Berardi and Goldblatt 1980, Xue 1980). For this reason, it was tested in China as a contraceptive for males. Its effect is attributed to the generation of oxygen radicals. Refined cottonseed oil does not contain gossypol, thus the attention is directed exclusively toward cotton grain. Fat-soluble vitamins have considerable positive influences. Vitamins A and the family of carotenes possessing vitamin A activity, as well as vitamins D and E, are fat-soluble and water-insoluble substances. Consequently, these substances occur together only with fat, i.e., they can be conveyed to the body only via fat-containing
36
Fats and Oils Handbook
food (Sebrell and Harris 1954). Vitamin A is necessary for regular growth, normal eyesight and procreative capacity. Moreover, it plays an important role in the stability of the cell membranes. Vitamin D ensures the correct calcium level in serum and is necessary for the normal growth of bones. Vitamin E protects vital substances such as unsaturated fatty acids, vitamins A and D, as well as thiol groups in enzymes from oxidation (c$ Chapter 2.2). In contrast to the essential fatty acids, vitamins occur in animal and vegetable fats, although vitamin E is present in larger quantities only in vegetable fats. Thus, with a normal food supply, deficiency is not an issue. Vitamin E represents one of the essential radical scavengers in lipid membranes (Pryor 1976). It was applied in clinical trials to combat illnesses caused by oxidation processes. These trials were rather successful (Bieri et al. 1983). A protective function towards DNA was observed (Beckmann et al. 1982), as was greater endurance in test animals (Davies et al. 1982). Other experiments suggest that vitamin E has anticarcinogenic effects as well (Wang 1982). p-Carotene also has antioxidant effects. It intercepts singlet oxygen, which has a strong mutagenic effect as a result of its high reactivity (Foote 1988, Krinsky and Deneke 1982). Experiments have also shown a protective function against the development of cancer (Mathews-Roth 1982, Rettura et al. 1983). A survey of the multiple fields of applications was made by Ames (1983). It is assumed that fatsoluble vitamins are helpful against oxidized metabolites of cholesterol that were observed to contribute to the development of heart disorders (Yagi et al. 1981). Apart from the anticarcinogenic effect of some of the minor components in fats, studies reporting a direct correlation between the fat intake and the frequency of breast and colon cancer continue to appear (Doll and Pet0 1981, Fink and Kritchevsky 1981, Kinlen 1983, NRC 1982). To date, it has not been possible to establish a direct connection. However, there seem to be more indications that the frequency of cancer generally rises with caloric intake. Only in this connection could fat be a role-playing factor.
1.5 Fats and Oils in Legislation The legislation in effect for this branch of industry applies to the products, thereby directly affecting the consumer and producer. The legislation also applies to the production process. 1.5.1 Product-Related Legislation
Many foods are narrowly defined by laws and regulations concerning their composition, mode of production and qualities. Not everything can (or should), however, be regulated by laws. In addition to legal directions, certain modes of behavior (principles of the responsible producer, good manufacturing practice) have emerged and various codes have been formulated, e.g., the Codex Alimentarius of the FAO, and the Leitsatze des Deutschen Lebensmittelbuches (Guiding Principles of the German Food Book) is an example for Europe. These guiding principles are
Importance of Fats
37
not legally binding but are consulted to define honest trading practice and are the foundations of legal decisions in case of controversy. In many cases, they fill the gaps where neither laws nor special regulations exist or give specifications which exceed legal limitation or description. In principle, there can be two motivations for product-related legislation in the domain of food, i.e., the protection of the consumer and citizen and aspects of economic policy. The protection of the consumer can include matters of health, but also protection from fraud. Aspects of economic policy might include emergency situations (war/postwar), partial attempts at selfsufficiency, or the preservation of an agriculture that is no longer competitive under the conditions of the world market. Concerning health risks, the protection of the consumer is always foremost and falls under the duties of the state within the obligation of public care. Frequently, however, the extent and the character of the measures to be taken are under discussion. Fats and oils, as such, fall under the common rules on maximum values of environmental pollutants. In contrast, there are very detailed rules for the products described in Chapter 8 (butter, margarine and mayonnaise). Legislative interventions motivated by health policy in the field of oils and fats have rarely occurred. An example is the regulation regarding the maximum content of erucic acid; however, this has been rendered superfluousby the cultivation of new types. For ingredients, processing aids, and additional substances, there are two basic approaches. One is that all substances that are not deemed harmful can be admitted, and consequently, harmful substances are prohibited or restricted in their quantity. The other is that everythrng that is not explicitly allowed is prohibited. The EC follows the second principle in many fields (regulation about the admission of food additives). This is a policy motivated by a desire for control rather than one of protection from danger, a fact that becomes immediately obvious when questioning why an ingredient is prohibited in one food but allowed in another. With few exceptions, one and the same substance cannot be at once both harmful and harmless. Trade policy is aimed primarily at the protection of agriculture. Due to their structure, the European States are not able to offer all agrarian products at world market prices. Therefore a certain protection is advisable to maintain at least partial independence.It must be considered, however, that excessive protection also prevents the seizing of opportunities. Legislation usually intervenes in times of emergencies. This happens primarily by means of regulations or guiding principles. Even more so than laws, guiding principles are a mirror of their times. During World War 11, they gave reliable information about the supply situation in Germany because regulations were in each case adapted to it. Thus, according to the German guiding principles for mayonnaise of 1941, salad mayonnaise, for example, had to contain only 20% oil instead of 50%, and milk and fish protein were allowed as substitutes for egg yolk. 1.5.2 Production-Related Legislation
In the production of oils and fats by means of mechanical or solvent extraction, in their processing or refining, and in the making of products containing fat, the producer
Fats and Oils Handbook
38
is subject to many general legal regulations concerning emissions or sewage, for example, but also to several highly specialized injunctions. These directives can differ widely depending on the location of the business, and even within one country from community to community. Dealing with these regulations in a detailed way and on a universally valid basis is possible but would exceed the scope of this book.
1.6 Fats as Industrial Raw Materials A relatively large portion of edible fats and oils is utilized for industrial purposes
(not nutrition). Often batches that do not comply with the strict demands for foodgrade raw materials are used for this purpose. Worldwide, the production of oleochemicals is -9-10 million ton (Seidel 1983), and a wide range of products is produced (Fig. 1.25). For some oils and fats, the portion not used for nutrition is considerable (Table 1.7). In 1981, after a continuous rise since the first energy crisis in 1973, the price of the raw material ethylene had climbed beyond that of soybean, coconut and palm oils, and tallow (Fig. 1.26). At that time, large chemical companies tried to secure their position by acquisitions that would provide a position in this raw material market. In the meantime, ethylene prices have fallen again. This interest was also motivated by a desire to remain in the market and exert influence on the types of new crops cultivated exclusively for the food industry. Erucic acid is relatively easily modified chemically. With the transition to rape OillFat
Olymml Resins EmulabIan C e i l U I o ~produdion o i for n ~ ~POlyOlS mineral oil produdion CosmsUcs Glymml Eaten Detergents
Auxiliary ~
Fatty h i n o s
Fatty Alcohols
Fatty Amldes
Adddiws for coal flotaUon Anti mnorives Sufladsntr Emubifiers
Esters with polyethybnglycd Fabric deanen Non-ionogenic emuI8hien
Detergents Emutsifien Fire extinguishen
Animal feed soaps Chemicsb fcfthe mineral oil and rubber industry
Fig. 1.25. Simplified flowchart of oleochemicals production.
Importance of Fats
39
TABLE 1.7
Uses of Vegetable Oil for Nonfood Purposesa Oil type and nonfood usage (YO) 0.25
Soybean oil Palm oil Palm kernel oil Rapeseed oil
10 10 40
Coconut oil Castor bean oil Linseed oil Tung oil
55 100 100 100
Type of usage (% of total nonfood usage) 36
Fatty acids Animal feed Soap Other
29 15 13
Paints Lubricants Polymers
3 2 2
aSource: Pryde and Rotfus (1 989).
species with low erucic acid content, the chemical industry was robbed of an important raw material. From then on, the prices for a low tonnage of rape with a high portion of erucic acid (HEAR) were above those of LEAR oil. Today crambe oil, which also possesses 55-60% of erucic acid, is considered to be a replacement for HEAR. Mustard seed oil can also be used. Taken as a whole, the production of raw materials in fat chemistry has developed from synthetic to natural raw materials, and this trend is continuing (Table 1.8). 70
-
.
0
Fig. 1.26. Price relation between soybean oil and ethylene.
Fats and Oils Handbook
40
TABLE 1.8 Oleo Chemicals and Their Raw Material Sourcesa Fatty acids
Amount (1 OOO ton) YO Natural YOSynthetic
Fatty alcohols
Glycerol
Fatty arnines
U.S.
Europe
U.S.
Europe
U.S.
Europe
U.S.
Europe
lo00
650
160
195
350
210
110
64
98 2
99 1
57 43
72 28
16 84
37 63
85 15
100 0
dSource:Seidel (1 983).
1.7 Fats and Oils as a Source of Energy In the course of history, it has been demonstrated repeatedly that fats are suitable as a source of energy. Rudolf Diesel had already determined that his engines could run on edible oil. As early as 1900, a Diesel engine powered by peanut oil was shown at the world’s fair in Paris (Nitske and Wilson 1965). However, the true potential of renewable raw materials may lie not in the combustion of the oils known today but in the utilization of new species. When we compare the qualities of vegetable oils with Diesel fuel, we notice that the caloric value is -10% below that of Diesel oil (Table 1.9). Among renewable raw materials, vegetable oils exhibit the most favorable relation between energy yield and energy investment (Table 1.10).Because vegetable oils have always been used in part as a source of energy, the idea is not new. However, the demands on the oils for use in modem engines have changed compared with those for illumination purposes. A study by Apfelbeck (1988) shows which fuel parameters must be met for today’s vehicles (Table 1.11). When comparing the prices for Diesel and soybean oil, we see that for the time being, there is no point in using edible oils and fats for combustion purposes. TABLE 1.9 Comparison of Diesel Oil, Rapeseed Oil, Sunflower Oil and Their Methyl Esters Sunflower
Caloric value (MJ/kg) Density (dcrn) Viscosity (cP,20°C) Cloud point (“C) Flash Point (“C) Ash (Yo) Sulfur (YO) Sulfur (rnol%) Reference
Diesel oil
Crude oil
Methyl ester
4246 0.835 3.9 -0.6 50-77 0.01 -0.27 -0.1 4 Shell
39.28 0.925 34.7 -6.6 215.5 0.04 0.1 2
40.16 0.880 4.22 0-1 183
-
-
0.01
-
Quick 1989
Rapeseed Crude oil
36.7-37.7 0.91-0.92 68-97.7
-
Methyl ester
37.02-37.20 0.86-0.90 6-9
-
31 7-324 1 1 1-1 75 <0.01-0.5 <0.01-0.05 0.009-0.01 2 0.002-0.006 Bundesurnweltamt 1993
41
importance of Fats
TABLE 1.10 Energy Balance from Renewable Source9 Source
Energy balance investdyielded
Energy yield net ( a h a )
2.8 2.7 2.5 1.3 1.1
43.3 37.9 58.9 18.4 5.2
Sunflower oil Rapeseed oil Ethanol from sugar beets Corn Wheat a%urce: Pernkopf (1984)
TABLE 1.11 Requirements for Fuel Ester9 Free fatty acids Mono-, diglycerides Glycerol Methanol Water Metals (each)
<0.2% <0.1 Y o
=%Source: Apfelbeck (1988)
In this comparison, it has to be considered that in Europe, taxes constitute the largest portion of the price for vehicle fuels. The U.S., with its much lower taxation rate, thus presents a better opportunity (Fig. 1.27). Considering the respective quantities, it becomes obvious that vegetable oils could cover only a small fraction of the demand. Consequently, greater utilization would lead to a considerable shortage of oils for consumption, and thus to rising prices. In spite of these rather poor prospects of finding an economically viable alternative to mineral oil fuels in today’s vegetable oils, experiments partially supported by the German Federal Department of Research and Technology are underway under strictly controlled circumstances to determine the behavior of Diesel engines suited for rapeseed oil (Anonymous 1988). Although experts such as the Federal Agency for the Environment released a study concluding that this route is not viable, new plants have been built. In Austria, for example, more than 10 plants had already been erected; only one is currently still operational at a low level. Even if a redistribution of the subsidies is effected to support these projects, they can hardly be successful given the current low price for mineral oil. The fanners’ associations stated that in 1990, 80% of the arable land of the Federal Republic of Germany would suffice for the production of food. For inactive areas, subsidies of 700-1440 German marks subsidies per hectare are paid currently. Cultivated with rape, these areas would suffice to meet 3 4 % of the annual
Fats and Oils Handbook
42 70 60
.
ziu d
g40 v)
2. 30 8
!5
20
10
0
Fig. 1.27. Price relation between diesel oil and soybean oil in the US.
demand for fuel oil or 10-12% of the demand for Diesel oil (Stover 1988). However, this could be done in a reasonable way only with smaller, decentralized, simple oil mills (delivery by the farmers themselves). Because larger amounts of fat remain in the meal in such mills (pressing only, without preliminary treatment of the seed), higher prices for meal would have to be charged for the process to be economical. This might indeed be possible because such meal has a better value as fodder in terms of energy supplied, but it is doubtful whether the market would honor it. Altogether, this scenario is interesting, but inefficient for the time being. As an example of oil fruits that are not currently in use, a research project conceming the purge nut can be examined. The purge nut is a spurge plant and grows even in tremendous heat and in the poorest soils. The nut was rediscovered by scientists of the Society for Technical Cooperation at the Western tip of Africa. (DPA 1987). An engine powered with its oil ran successfully during a long-term trial. The oil was described as early as 1830 by Geiger, who used it as a laxative. According to scientists, the nut can be used as a raw material for soap production, as a source of energy, and as a supplier of raw chemicals. New raw materials can change the situation, although considerable costs must be expected when deriving the fadoil Erom the raw materials; the chances of commercialization are low at present, considering the present supply of mineral oil on the world market. Another interesting opportunity is to make use of deserts or semi-deserts by growing plants at a very low density and to organize the cultivation effectively over the entire area that remains otherwise unused. However, suitable plants have not yet been found. With an insufficient oil content, used-up auxiliary substances and garbage removal pose sigmficant problems.
importance of Fats
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1.8 New Sources of Raw Material New sources of raw materials can open up in two different ways. It is possible to use new crops for oil supply, especially for industrial use. In addition, it is feasible that new plants can be adapted to new requirements by means of cultivation or by genetic modification. More recent contributions to this discussion (e.g., Richtler and Knaut 1991) cover the entire ecological balance in their reflections, for example, the CO, balance, and as a result, new aspects might emerge. 1.8.1 New Plants Through Plant Breeding or by Genetic Modification
The possibility of modifying plants by means of cultivation is virtually unlimited. All types existing today have been generated via a selection process that has lasted for centuries. However, with today’s technology, it is possible to accelerate this selection mechanism or even to “construct” plants within certain limits. A very good example for the conventional cultivation of an oil plant with new qualities is the “Double-Zero-Rape.’’ First, the fatty acid composition of this type of rape was modified in such a way that it contained (virtually) no erucic acid; then, bitter glucosinolates were removed by cultivation to make the meal more suitable as animal feed. Plans to remove gossypol from cottonseed by cultivation proceed in the same direction. It would make this oil type more applicable, because here, too, the use of the meal could be optimized. However, changing the composition of fatty acids can have other objectives as well. By ingeniously cultivating and blending the raw materials, the amount of oil that has to be modified could be reduced considerably. In the most favorable case, oils with ideal compositions could be processed into products directly from the oil mill. Opportunities lie in the cultivation of types with such an amount of saturated fatty acids that hardening is no longer necessary. An ideal distribution of fatty acids in the triglyceride can make interesterifkation obsolete. Additionally, new plants may yield qualities that render refining at least partially superfluous. Many other improvements are conceivable, but most of them will be achieved in a reasonable time only by means of gene technology. Whether this technology will be accepted by the public-at least in Europe-is doubtful. Achieving these aims would reduce production costs and improve the image perceived by the consumer Species of safflower that possess oil rich in oleic acid already exist; the same is true for sunflower types that contain >80% oleic acid (US.Patents 4627192, 1986, and 4743402, 1988). With increasing frequency, these cultivars are covered by patents, so that efforts of the growers become more interesting on a commercial level. In Canada, rape already provides >50% of the raw materials for margarine. The disadvantage of rapeseed oil is its relatively high content of linolenic acid. Here also, the cultivation of a species with a linolenic acid content ~ 3 % has been successful (Allelix Crop Technology, Canadian Patent 1989). In the new species, linolenic acid is almost completely replaced by oleic acid. The same problem exists for soybeans. Cultivars of soybeans with a low concentration of linolenic acid have been successful. Species with a higher concentration of stearic acid were also found.
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In Chapters 1.4 and 4.3.2, gossypol is mentioned as an undesirable ingredient of cottonseed. Cotton that lacks gossypol-capsules has been cultivated successfully. However, the problem is not yet entirely solved because the new plants or rather their seeds are very vulnerable to infestation with AspergiZZusJuvus (cf.also Chapter 4.3.11; Campbell 1983). Among others, Rtibbelen and Hirsinger (1982 and 1987) reported on methods applied today to create tailor-made plants; more examples are given in Chapter 4.
1.9 Fat Substitutes It has been known for a long time that people in the industrial nations consume too much fat. The main reason is that fat is an excellent carrier of flavors; its physical qualities make food smooth, thereby increasing the pleasant taste considerably. Compared with other food ingredients, fat has more than twice the caloric content. Thus, in the attempt to limit the caloric supply, reducing the intake of fat has the strongest effect (per unit of weight). For these reasons, there have been attempts to find substitutes with reduced or zero caloric value. This is much more difficult than finding a substitute for sugar, because the applications of fat deviate strongly from those of sugar. Saccharin was found early on and later Cyclamate, and some years ago, Aspartame and Acesulfam. Attempts to find a substitute for fat culminated at the end of the 1980s. LaBarge (1988) named the main classes of substances that might serve as lowcalorie oils and as substitutes.These include the following: combinations of water and surface active substances (surfactants), including special proteins and polysaccharides with absorption capacity, compounds such as acetoglycerides and medium-chain triglycerides with a reduced caloric value, compounds that deviate considerably in structure from triglycerides, such as paraffin and silicone, compounds without calories with fat-like qualities, produced mainly through modified ester bonds, e.g., fatty esters of polysaccharides. Only in 1929 did Channon and Collison produce the first reliable study concerning the absorption of fats in the body. Strycker (1941) and Deuel(l948) compiled extensive material by feeding rats. After these experiments indicated which substances are not resorbed, research could be directed systematically. 1.9.1 Carbohydrates
There are some products on the market that could replace fat in their applications. As a rule, they can be used only in low-temperatureapplications and those in which fat is employed to reach a good, smooth texture. They are not suitable as a heat transmitter in roasting and frying. Also, they do not develop the respective flavors. Their primary
Importance of Fats
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effect is to absorb water and give a smooth feeling in the mouth. Examples of such products are polydextrose (Pfizer), which, however, can have a laxative effect, N-Oil (trademark of National Starch Co.) or maltodextrine. Vogt (1987) demonstrated the qualities of a fat substitute based on starch, i.e., enzymically modified potato starch that can be used in place of fat in such foods as stuffings or milk products. 1.9.2 Polycarbonic Acid Esters
Hamm (1984) conducted experiments on polycarbonic acid esters as a fat replacer for margarine and mayonnaise. Margarine was produced with trialkoxy carballylate and jojoba oil (LaBarge 1988). With jojoba oil, however, margarines were not convincing. Trialkoxytricarballylate (TATCA) showed excellent qualities, but failed in the animal-feeding tests conducted to date. 1.9.3 Polyglycerol Esters and Ethers
Polyglycerol esters can easily be produced (Babayan 1968, Mcintyre 1979), but in feeding tests, it did not appear that the caloric value was lower than that of triglycerides. These substances were also not well suited for baking (Babayan 1982). Instead of triglyceride esters, triglyceride ethers can also be synthesized. Several patent applications have been submitted. 1.9.4 Proteins
In 1988, “Simplesse” (trademark of NutraSweet), a fat substitute based on protein was announced by the NutraSweet company. Simplesse is produced by decomposing long-chain proteins into small pieces of -0.001 mm in diameter. The pieces are so small that 50 billion fit on a teaspoon (Wagner 1988). The small particles exhibit the same creaminess as fat, deceiving the taste organs. The sensory sensation of creaminess is actually not related to classes of substances like triglycerides, as was believed for a long time. It is due to particle size and shape. Simplesse is a protein and therefore all applications involving strong heating are impossible. Because its effect is based on a deception of the tongue, Simplesse can be applied only where fat creates a creamy impression in the products. In 1989, NutraSweet intended to introduce Simplesse without examination by the FDA, claiming that it is a food only in “shredded” form. The FDA, however, insisted on a procedure for its approval, which required some time. In the meantime, Simplesse is on the market. 1.9.5 Sucrose Polyesters (SPE)
In the 1950s and 1960s, the basic work for the application of sucrose polyesters had already been done by Rizzi and Taylor (1976). They esterified methyl esters of soybean oil fatty acids with sugar. For synthesis, potassium salts of the fatty acids are formed and are converted with the aid of sodium hydride. Volpenheim (1985)
Fats and Oils Handbook
46
received a patent for replacing sodium hydride with potassium carbonate. For the time being, SPE are the only fat substitutes that can replace fat in practically all applications. Because of their good heat stability, they can also be applied in areas in which the above-mentioned substances fail. In the literal sense, they are simply “fat substitutes.” A major obstacle to their introduction was that SPE have a strong laxative effect when a certain quantity is consumed. Procter and Gamble announced that the problem could be solved by adding an antidote. Meanwhile, the problem has been solved without such an antidote. In addition to Procter and Gamble, Unilever, Mitsubishi, and Dai-Ichi have also worked on SPE (LaBarge 1988). The initial patent held by Procter and Gamble expires in 1998, but will most likely be prolonged by increasing numbers of new patents concerning particular procedures for production. Bernhardt (1988) described the production (Fig. 1.28). Instead of the three fatty acids esterifled to glycerol, sugar is able to bind eight fatty acids. In SPE,the sugar contains six, seven or eight fatty acids, because complete esterifcation of all hydroxyl groups has not yet been successful. SPE are miscible with fadoil and insoluble in water (Mattson 1976). They cannot be resorbed by the body because the body does not possess enzymes to split them. A survey of the possibilities of application, advantages and problems of SPE was made by Toma et al. (1988). When this book was edited in German, the question whether SPE (termed Olestra by Procter and Gamble) could be introduced depended mainly on whether legislative authorities (FDA, Food and Drug Administration, BGA, Bundesgesundheitsamt/ FaffOil
I
Esterriinl,
]
<<< Methanol <<< ~
>>> G cerol
Fatty acid methyl ester
,
Neutralization
I
Bleaching
I
I
Deodorization
I
SPE (fully refined)
Fig. 1.28. Flow chart of SPE production.
Importance of fats
47
German Federal Health Agency) would license it. Licensing is necessary because, according to the prevailing definition, SPE is not a food, but rather a food additive. Licensing had been applied for at the FDA in 1988. Meanwhile Olestra (trademark of Procter and Gamble) has been approved for a certain range of snacks. Application in Europe is still doubtful. 1.9.6 Polymeric Siloxanes
Polymeric siloxanes as well as substituted phenyl-methyl-polysiloxaneswere also investigated as possible fat substitutes. The experiments were conducted at the Institute for Human Nutrition at Michigan State University and did not show any side effects in rats. Experiments in kitchen applications (e.g., frying) were conducted by Zabik (1987 and 1989) and Morehouse (1987 and 1989) and gave satisfying results. The FDA has not yet approved these substances. 1.1 0 References Aaes-Jorgensen, E., (1961) Essential Fatty Acids, Physiol. Rev. 41, 1-5 1. Aaes-Jorgensen, E., (1966) Unsaturated Fatty Acid Isomers in Nutrition, Nutr. Rev. I , 24. Adam, D.J.D., Hansen A.E., and Wiese, H.F., (1958) Essential Fatty Acids in Infant Nutrition 11. Effect of Linoleic Acid on Caloric Intake, J. Nutr. 66, 555. Ahrens B., (1957) The Influence of Dietary Fats on Serum Lipid Levels in Man, Lancet I, 943.5. Ahrens, B., The Effect on Serum-Lipids of a Dietary Fat, Highly Unsaturated, but Poor in Essential Fatty Acids, Lancet I, 115 (1959). Ames, B.N., (1983) Dietary Carcinogens and Anticarcinogens-Oxygen Radicals and Degenerative Diseases, Science 221, 1256-1264. Anonymous, (1988) Rapsol als Treibstoff, Chemische Rundschau 40, 10. Anonymous, (1987) Malaysia Defends Palm Oil, Food Manufacture Int. SeptJOct., 10. Apfelbeck, R., private information to Stover 1988, citation from Stover see below. Assmann, G., and Schettler, G., (1987) Ein Strategie-Konzept der Europaischen Arteriosklerose-Gesellschaft: Die Pravention der koronaren Herzerkrankung, Deutsches Arzteblart-Arztliche Mitteilungen 84, 45-48. Babayan, V.K., and McIntyre, R.T., (1968) Preparations and Properties of Some Polyglycerol Esters of Short and Medium Chain Length Fatty Acids, J. Am. Oil Chem. SOC.48, 307. Babayan, V.K., and McIntyre, R.T., (1982) Polyglycerol Esters: Unique Additives for the Bakery Industry, Cereal Foods World 27, 510. Bang, H.O., and Dyersberg, J., (1975) Haemostatic Function and Platelet Polyunsaturated Fatty Acids in Eskimos, Lancet 2, 433-435. Beckman, C., Roy, R.M., and Sproule, A., (1982) Modification of Radiation-Induced SexLinked Recessive Lethal Mutation Frequency by Tocopherol, Mutat. Res. 105, 73-77. BenadC, A.J.S., (1988) Editorial Comment: Essential Fatty Acids, SA Tijdskrift voor Voedselwetenschap en Voeding I , 2. Berardi, L.C., and Goldblatt, L.A., (1980) Toxic Constituents of Plant Foodstuff; in Toxic Constituents of Plant FoodstufJ; (Liener I.E., ed.), pp. 183-237, Academic Press, New York.
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Bergstrom, S.,and Samuelsson, H., (1965) Prostaglandins, Annu. Rev. Biochem. 101, 34. Bernhardt, C. A,, (1988) Olestra-A Non-Caloric Fat Replacement, Food Technol. Int. Europe 176. Bieri, J.G., Corash, L., and Hubbard, V.S., (1983) Medical Uses of Vitamin E, N. Engl. J. Med. 308, 1063. Burr, G.O., and Burr, M.M., (1929) A New Deficiency Disease Produced by the Rigid Exclusion of Fat from the Diet, J. Biol. Chem. 82, 345-367. Campbell, C., personal information to Ames B.N. (1983), citation from Ames see above. Channon, H.J., and Collison, G.A., (1929) The Unsaponifiable Fraction of Liver Oils. IV. The Absorption of Liquid Paraffin from the Alimentary Tract in the Rat, J. Biochem. 23, 676. Childs, M.T., (1993) Fish, Dietary Importance of Fish and Shellfish, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 1879, Academic Press, London. Davies, K.J.A., Quintanilha, A.T., Brooks, G.A., and Packer, L., (1982) Free Radicals and Tissue Damage by Exercise, Biochem. Biophys. Res. Commun. 107, 1198. Deuel, H.J., (1948) The Digestibility of Rapeseed Oil in the Rat, J. Nutr. 35, 295. DFG, (1983) Deutsche Forschungsgemeinschaft, Zur Bedeutung d e r Fette in d e r menschlichen Entiihrung, WissenschaftlicheArbeitspapiere, Verlag Chemie, Weinheim. Doll, R., and Peto, R., (1981) The Causes of Cancer; Quantitative Estimates of Avoidable Risks of Cancer in the United States Today, J. Natl. Cancer Inst. 66, 1191-1308. Dormandy, T.L., (1983) An Approach to Free Radicals, Lancet 2, 101&1014. DPA, Kraftstoff aus der Nub, from Siiddeutsche Zeitung 4.5.1987. Driss, F., and Darcet, P., (1988) Effet des Huiles de Poison Riches en Acides Gras n-3 sur les Facteurs de Risque des Maladies Cardio-Vasculaires, Revue Frangaise des Corps Gras 35, 7-1 1. Dyerberg, J., Bang, H., and Home, N., (1975) Fatty Acid Composition of the Plasma Lipid in Greenland Eskimos, Am. J. Clin. Nutr. 28, 958-966. Erman, A., and Ranke, H., (1923) Agypten und das agyptische Leben im Altertum, Verlag J.H.C. Mohr, Tubingen. von Euler, US., (1934) Zur Erkenntnis der pharmakologischen Wirkungen von Nativsekreten und Extrakten miinnlicher accessorischer Geschlechtsdriisen, Naunyn-Schmiedeberg 's Arch. Exp. Path. P h a d 78, 175. von Euler, U.S., (1935) iiber die spezifisch blutdrucksenkende Substanz des menschlichen Prostata und Samenblasensekrets,Klin. Wschr. 14, 1182. FAO/WHO (1977) Dietary Fats and Oils in Human Nutrition. F A 0 Food and Nutrition Paper no. 3, Food and Agriculture Organization of the United Nations, Rome. Fink, D.J., and Kritchevsky, D., (1981) Workshop on Fat and Cancer, Cancer Res. 41,3677. Foote, C.S., (1982) Absorption of Singlet Oxygen by p-Carotene, in Pathology of Oxygen, (Autor, A., ed.), pp. 2 1 4 , Academic Press, New York. Friedeberg, A S . , Milking Taxpayers or Making Milk Quotas More Market Oriented, Speech delivered at the 29th Annual General Meeting of the International Federation of Margarine Associations, Oslo, 2. Juni 1986 (Unilever Publication). Friedeberg, AS., Protectionist Rebalancing or Market-Orientated Reform, The EC's Oils and Fats Policy in Focus, Speech delivered at the 10th Anniversary Conference of PORIM, Kuala Lumpur, 1989 (Unilever Publication). Friis-Hansen, B., (1965) in Humun Body Composition, (Brozek, J., ed.),p. 191, Pergamon, Oxford.
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Gander, K.F., (1984) Die Fettversorgung des Menschen aus wirtschaftlicher und technologischer Sicht, Fette Seifen Anstrichrn, 86, 1. Geiger, P.L, (1830) Handbuch der P h a m z i e , Heidelberg. Geigy, J.R. AG, Pharma Basel, Documenta Geigy, Wissenschaftliche Tabellen, 7.Auflage. Goldberg ,C., and Schonfeld G., (1985) Effects of Diet on Lipoprotein Metabolism, Annu. Rev. Nutr. 5, 195-212. Gottenbos, J.J., (1985) in The Role of Fats in Human Nutrition, (Herausgeber Padley, F.B., and Padmore, J. eds.), pp. 117-131, Ellis Howard,Chichester. Gottenbos, J.J., (1988) in Dietary Fat Requirements in Health and Development, (BeareRogers, J., ed.), pp. 107-1 19, American Oil Chemists' Society, Champaign, IL. Groen, J., Tjong, B.K., Kamminga, C.E., and Willebrands, A.F. (1952) The Influence of Nutrition, Individuality and Some Other Factors, Including Various Forms of Stress, on the Serum Cholesterol. Voeding 13, 556. Gmndy, S.M., (1986) Cholesterol and Coronara Heart Disease, A New Era, State of the M e v i e w , J. Am. Med. Assoc. 256,2849-2858. Hagemeister, H., Precht, D., Franzen, M., and Barth, C.A. (1989) Transfer von omega-3Fettsauren in das Milchfett von Kiihen, Proceedings of the Annual Meeting of DGF, Miinster, 1989, p. 22. Hamm, D.J., (1984) Preparation and Evaluation of Trialkoxytncarbakylate, Trialkoxycitrate, Trialkoxyglycerylether, Jojoba Oil and Sucrose Polyester as Low Calorie Replacements of Edible Fats and Oils. J. Food Sci. 49, 419. Hammond, E.G., (1988) Trends in Fats and Oils Consumption and the Potential Effect of New Technology, Food Technol. (Jan.), 117. Hansen, A.E., Haggard, M.E., Boelsche, A.N., Adam, D.J.D., and Wiese, H.F., (1958) Essential Fatty Acids in Infant Nutrition 111. Chemical Manifestations of Linoleic Acid Deficiency, J. Nutr. 66, 565. Hanssen, E., and Wendt, W., (1965) Die Geschichte der Lebensmittelwissenschaft, in Handbuch der Lebensmittelchemie, vol. 1, Springer Verlag, Berlin. Harris, S.W., (1989) Fish Oils and Plasmalipids and Lipoprotein Metabolism in Humans: A Critical Review, J. Lipid Res. 30, 785-807. Holman, R.T., (1961) How Essential Are Fatty Acids? J. Am. Med. Assoc. 178, 930-933. Holman, R.T., (1963) Symposium on Human Calcium Requirements, J. Am. Med. Assoc. 185, 588-593. Holman, R.T., Caster, W.O., and Wiese, H.F., (1964) The Essential Fatty Acid Requirement of Infants and the Assessment of Their Dietary Intake of Linoleate by Serum Fatty Acid Analysis, Am. J. Clin. Nutr. 14, 70-75. Hunter, J.E., (1989) Scientists Discuss Dietary Fatty Acids. J. Am. Chem. SOC. 66, 1251-1256. Kankare, V., and Antila, V., (1989) Extraktion von Milchfett mit iiberkritischem Kohlendioxid, Fat Sci. Technol. 91, 485. Kinlen, L.J., (1983) Fat and Cancer, Br. Med. J. 286, 1081-1082. Kinsella, L.W., Partridge, J., Boling, L., Margen, S . , and Michaels, G., (1952) Dietary Modification of Serum Cholesterol and Phospholipid Lev&, J. Clin. Endocrinol. 12, 909. Krinsky, N.I., and Deneke, S.M. (1982) Interaction of Okygen and Oxy-Radicals with Carotenoids, J. Natl. Cancer Inst. 65, 205-210. Kromhout, D., Bosschieter, F., and Goulander, C., (1985) The Inverse Relation Between Fish-Consumption and 20-Year Mortality from Coronary Heart Disease, N. Engl. J. Med. 312, 1205-1209.
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Laasko, I., Seppben-Laasko, T., Vanhanen, M.D.H., (1989) Effects of Partial Rapeseed Oil Substitution on Serum Cholesterol, DGF Annual Meetin, Miinster, 1989, p. 6. LaBarge, R.G., (1988) The Search for a Low Caloric Oil, Food Technol. 84. Lambert, J.P., (1993) Meat, Dietary Importance, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 2949, Academic Press, London. Langdon, R.G., and Philips A.H., (1961) Lipid Metabolism, Annu. Rev. Biochem. 30, 189-2 12. Leaf, A., and Weber, P.C.,(1988) Cardiovascular Effects of n-3 Fatty Acids, N. Engl. J . Med. 318, 549. Leonhard E.C., The Economics of the Commercial Tropical Oils, Speech delivered at the 21st World Congress of the International Society for Fat Research, The Hague, October 1995. LRC-CPT, Lipid Research Clinic Coronary Primary Prevention Study, JAMA, Deutsche Ausgabe, 231-255, April 1984. Ludwig, L., (1968) Fett und Erniihrung, p. 49, Internationale Margarine Information, Wien. Macy, I.G., (1949) Composition of Human Colostrum and Milk, Am. J. Dis. Child 78, 5 89-503. Mathews-Roth, M.M., (1982) Photosensitizitian by Porphyrins and Prevention of Photosensitization by Carotenoids, J. Natl. Cancer Inst. 69, 279-285. Mattson, F.H.,,Jandacek, R.B., and Webb, M.R., (1976) The Effect of Nonabsorbable Lipid, SucrosePolyester, on Absorption of Dietary Cholesterol by the Rat, J. Nutr. 106, 747. McGandy, R.B., and Hegsted, D.M., (1975) Quantitative Effects of Dietary Fat and Cholesterol on Serum Cholesterol in Man, in The Role of Fats in Human Nutrition, (Vergroesen, A.J., ed.), Academic Press, London. McIntyre, R.T., (1979) Polyglycerol Ethers, J. Am. Oil Chem. SOC.56, 835A. Melchert, H.U., (1988) Fettsaurespektren ausgewahlter Lipidklassen des Serums bei Vegetariern und Nicht-Vegetariern, Lebensmittelchem gerichtl. Chem. 42, 119. Mertz, D.P., (1983) Butter oder Margarine? Zur Klarung einer Streitfrage, Deutsche Apotheker Zeitung, 123, 465. Mielke, R., (1985) Present and Future Position of Palm and Palm Kernel Oil in World Supply and Trade, J. Am. Oil Chem. SOC.62, 193-197, Mielke T., (1990) Current World Supply, Demand and Price Outlook for Oils and Fats, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 1-9, American Oil Chemists’ Society, Champaign, IL. INFORM I , 190, (1990), Morehouse, S.E., (1990), citation from Am. J . Clin. Nutr. 46 (1987), and J. Food Sci. 54 (1989). National Institutes of Health Consumers Development Conference Statement 5, no. 7 (1984), in J. Am. Med. SOC.253, 2080-2086, (1985). National Research Council (1982) Diet, Nutrition and Cancer, National Academy Press, Washington DC. Nitske, W.R., and Wilson, C.M., (1965) Rudolf Diesel, Pioneer of the Age of Power, University of Oklahoma Press, Normann, OK. Numa, S., (ed.), (1984) Fatty Acid Metabolism and Its Regulation, Elsvier Science Publishers, New York. Peters, J.P., and van Slyke, D.D., (1946) Quantitative Clinical Chemistry, Williams & Wilkins, Baltimore.
importance of Fats
51
Pimparkar, B.D., (1961) Correlation of Radioactive and Chemical Fecal Fat Determinations in the Malabsorption Syndrome, Am. J. Med. 30, 910-926. Pryde, E.H., and Rotfuhs, J.A., (1989) Industrial and Nonfood Use of Vegetable Oils, in Oil Crops of the World, (Robbelen, G., Downey, R.K., and Ashri A., eds.), McGraw Hill, New York. Pryor, W.A. (ed.),(1976) Free Radicals in Biology, Academic Press, New York. Quick, G.R., (1989) Oil Seeds as Energy Crops in Oil Crops of the World, (Robbelen, G., Downey, R.K., and Ashri, A., eds.), McGraw Hill, New York. R e m a , G., Dattagupta, C., Listowsky, P., Levenson, S.M., and Siefter, E., (1983) Fed. Proc. Fed. Am. SOC. Exp. Biol. 42, 786. Cited from Ames, B.N., Science 221, citation 116, p. 1256. Richtler, H.J., and Knaut, J., (1991) Umwelt und Fettchemie-Eine Herausforderung, Fen, Wissenschaji Technologie 93, 1-12. Rizzi, G.P., and Taylor, H.M., Synthesis of Higher Polyol Fatty Acid Polyesters, U.S. Patent 3.963.699, (1976). Robbelen, G., and Hirsinger F., (1982) in Improvement of Oil-Seed and Industrial Crops by Induced Mutations, pp. 161-170, Int. Atomic Energy Agency, Wien. Robbelen, G., and Hirsinger F., (1983) Fortschritte in der Welterzeugung von Rapssaaten, Fette, Seifen, Anstrichmittel 85, 395-398. Robbelen, G., and Hirsinger F., (1987) Development of New Industrial Oil Crops, Fat Sci. Technol. 89, 563-570. Robbelen, G., Hirsinger F., and von Witzke, S., (1987) Possible Use of Mutation Breeding for Rapid Domestication of New Crop Plants, Int. Atomic Energy Agency, Wien. Schettler, G., (1984) Der Mensch ist so jung wie seine Gefasse, Piper-Verlag Miinchen. Schlierf, G., (1986) Gegenwiirtiger Stand der Ernahrungstherapie bei degenerativen Herzund Gefabkrankheiten, Therapiewoche 36, 1349-1352, Schiittauf, W., and Pischel, U., (1978) Die Margarine in Deutschland in der Welt, Presseabteilung der Union Deutsche Lebensmittelwerke, Hamburg. Schiittauf, A.W.,( 1942) Probleme der Wel@ettversorgung, Internationale Agrarmndschau, Heft 3, Berlin Schwandt, P., (1987) Therapeutische Effekte diatetischer Mabnahmen bei Patienten mit Hyperproteinamien, Akt. Emahr. 12, 7-10. Sebrell, W.H. Jr., and Harris, R.S.., (1954) The Vitamins: Chemistry, Physiology, Pathology, vol. I, p. 1, vol. 11, p. 131, vol. 111, p. 481, Academic Press, New York. Seher, A,, (1987) Der Cholesterin-Gehalt von Pflanzenolen, Fat Sci. Technol. 89, 27-30. Seidel, H., (1983) Fettchemie hat Zukunft ... (Interview mit Geschaftsleitungsmitgliedern der Schering AG), Chem. Ind. 251. Shell, private information from The Hague Headquarters, the Netherlands (1990). Singer, P., Die Rolle der Eicosapentaensaure im Rahmen polyenreicher Diaten, Sonderdruck der Emihungs-Umschau. Stadelman, W.J., (1993) Eggs, Dietary Importance, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 1534, Academic Press, London. Stamler, J., and Epstein, F.H., (1966) Coronary Heart Disease-Risk Factors as Guide to Preventive Action, Prevent. Med. 27, 1. Stover, H.-M., Munch, E.-W., and Sitzmann, W., (1988) Gewinnung von Mineralolsubstituten aus Olsaaten, Fen, Wissenschaf, Technologie 90, 547-550. Strycker, W.A., (1941) Absorption of Liquid Petrulatum from the Intestine: A Histologic and Chemical Study, Arch. Pathol. 31, 670.
52
Fats and Oils Handbook
TaufeVTerneflunger/Zobel, Cholesterin in Lebensmittellexikon, Behr's Verlag, 1993. Thiele, O.W., (1982) Bedarf des Menschen an essentiellen Fettsiiuren, ZFA Zeitschrifi fiir Allgemeinmedizin 58, 1329-1331. Thomasson, H.J., (1953) Biological Standardization of Essential Fatty Acids, Int. Z . Vitaminforsch. 62, 25. Toma, R.B., Curtis, D.J., and Sobotor, C., (1988) Sucrose Polyester: Its Metabolic Role and Possible Future Applications, Food Technol. 93. Tucker, B.W., and Pigott, G.M., (1993) Fish Oils, Composition and Properties, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 1896, Academic Press, London. Umweltbundesamt, Okologische Bilanz von Raps61 bzw Rapsolmethylester als Ersatz von Dieselkraftstoff (Okobilanz Rapsol), Berlin, January 1993. UNION, 50 Juhre UNION, Werkszeitschrift der UNION Deutsche Lebensmittelwerke, Hamburg, (1979). Vles, Gottenbos, J.J, Nutritional Characteristics and Food Uses of Vegetable Oils, in Oil Crops of the World, (Robbelen, G., Downey, R.K., and Ashri, A., eds.), McGraw Hill, New York. Vogt, L., (1987) Entwicklung und Anwendung eines Fettersatzstoffes, Lebensmitteltechnik, 642. Volpenheim, R.A., Synthesis of Higher Polyol Fatty Acid Polyesters Using High Soap: Polyol Ratios, U.S. Patent 4.518.772 (1985). Wagner, J., (1988) Is There Finally a Perfect Fat Replacer? Food Engineering International 9. Wang, Y.M., (1982) in Molecular Interrelations of Nutrition and Cancer, (Wang, Y.M., Amott, M.S., van Eys, J., eds.), pp. 369-379, Raven Verlag, New York. Welch, V.A., (1993) Fats, Digestion, Absorption and Transport, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 1731, Academic Press, London. Wirths, W., (1981) Kleine Ndhwerftabelle,Umschau-Verlag, Frankfurt. Wolfram, G., (1987) Metabolische Wirkungen linolsaurereicher Kost, Aktuelle Emdhrungsmedizin 12, 11-19. Wooley, C.C., (1929) Vor 5000 Juhren, Verlag H. Franckh, Stuttgart. Xue, S.P.,(1980) Proceedings of Symposion on Recent Advances on Fem'liry Regulation, p. 122,2-5 Sept., Peking. Yagi, K., Okhawa, H., Ohishi, N., Yamashita, M., and Nakashima, T., (1981) Lesion of Aortic Intima Caused by Intravenous Administration of Linoleic Acid Hydroperoxide, J. Appl. Biochem. 3, 58. Yamori, Y., Nara, Y., Iritani, N., Workman, R., and Inagami, T., (1985) Comparison of Serum Phospholipid Fatty Acids Among Fishing and Farming Japanese Populations and American Islanders, J. Nutr. Sci. Vitaminol. 31, 417-422. Zabik, M.E., citation in J. Am. Oil Chem. Soc. INFORM. I 9 0 (1990), citation from Am. J. Clin. Nutr. 46 (1987) und J. Food Sci. 54 (1989).
Chapter 2
Composition, Structure, Physical Data, and Chemical Reactions of Fats and Oils, Their Derivatives, and Their Associates To understand the reactions of fats and oils and the technologies applied, as well as to be able to influence their characteristics and behavior during processing, it is important to know their properties and reactions. The number of main building blocks that make up common oils and fats is relatively small. Most of the different characteristics occur as a result of minor components and the immense number of possible combinations of these building blocks. Under natural conditions, the number of major reactions of oils and fats that lead to alteration is small.
*: H H
-
-
for instance R = - C (CH& CH3
I;
OR,
Scheme 2.1.
Fats are esters of fatty acids with the trihydric alcohol glycerol. Because of the symmetrical structure of the glycerol molecule, two identical outer positions (1-, 3-) and one central position (2-) exist, to which the fatty acids are esterified. The type of fatty acid, as well as the distribution across these positions, determines the characteristics of the triglyceride. Not only the composition by summation equation but also the structure of the triglyceride is therefore of great importance. The share of different fatty acids in the world production of common edible fats and oils is of interest (Table 2.1). The calculation of Boekenoogen (1941) is now more than fifty years old. Today’s distribution is different, mainly as a result of a shift of the main production areas from the tropical regions of the world to those with moderate climates and also because of new crop cultivation. The table shows the distribution of 1941, and 1950 onwards, each calculated for average fatty acid composition per species. The fatty acid composition of the main seed and pulp oils does not differ substantially among the main types. Therefore, shifts of only a few percentage points in the table may be caused by immense shifts in cultivation. So little a share of erucic acid remains, for example, that it disappears by rounding off. In new rape varieties, it is almost completely substituted by oleic acid. Furthermore, the trend toward oilseeds with a high content of essential linoleic acid is clear; coconut oil has drastically
decreased relative to the other oils, resulting in a parallel decrease in the appearance of lauric acid. The fatty acid compositions of the individual oils and fats are described 53
Fats and Oils Handbook
54
TABLE 2.1 Fatty Acid Distribution of the Common Vegetable Fats and 0ilsa.b Share (%) ~
Fatty acid C,,:, C,,:, C,,:,
C12:, C,:, C14:o C,: C,:,
Oleic Linoleic Palmitic Lauric Linolenic Myristic Erucic Stearic All others
~~
1941
1950
1960
1970
1980
1990
34 29 11 7 6 3 3 3 4
30 24 14 8 6 3 8 3 4
29 32 14 7 5 2 5 3 3
30 36 13 4 6 2 2 3 4
31 38 14 4 5 2 0 4 2
31 37 16 3 5 1 0 4 3
agecause fatty acid composition of vegetable oil is not uniform within the same kind of oil, these rounded figures are only indicative; however, they are based on thoroughly calculated figures from averages. bource: Boekenoogen (1 941) and own calculations.
in Chapter 4. Here, only the principles of composition and structure will be discussed. One unsaturated fatty acid is ubiquitous in fats and oils; two are almost ubiquitous. Oleic acid is present in all known fats and oils and also predominates in quantity (Table 2.1). Almost all fats and oils contain its next lower homologues, palmitoleic acid (although in very small quantities) and the double unsaturated acid with the same chain length as oleic acid, namely, linoleic acid, as well as other CIgZ2 acids. None of the saturated fatty acids is omnipresent. However, palmitic acid has almost the same distribution as oleic acid. The distribution of myristic acid and stearic acid is similar to that of linoleic and palmitoleic acid. To date, the fat and oil of -5000 species (animals and plants) have been analyzed. No correlation between their composition and occurrence has yet been found. As early as 1935, Hilditch proposed a link between the fatty acid composition of fats and the evolutionary stage of the species in which they occur-beginning with microorganisms and marine monocellular organisms via marine plants and animals, to both terrestrial animals and plants. No real evidence could be found for this approach, although some indications for this connection may exist (Fig. 2.1). It seems evident that the amount of saturated fatty acids and unsaturated C,8fatty acids (mainly oleic acid) increased during the course of evolution. Unsaturated long-chain fatty acids tended to disappear and palmitoleic acid (due to its occurrence also named zoomaric acid) diminished dramatically. Similar trends are also expected in vegetable fats, but an insufficient number of lower plants have yet been analyzed to prove this. However, some hints can be found in the change of fatty acid composition that occurs during the ripening of seeds following patterns similar to evolution (see also Chapter 4). In total, the spectrum of fatty acids that occur in main edible oils and fats is represented by no more than 10-12 compounds, representing >98 % of all fatty acids in food. Statistically, however, 10 different fatty acids allow the formation of
Composition, Structure, Physical Data, and Chemistry
55
Fig. 2.1. Proportion of certain fatty acids on the fat of sea and land animals (after Hilditch and Williams 1964).
more than 650 different triglycerides. Nature does not follow statistical distribution; therefore not all possible combinations can be found. The model of restricted statistical distribution best simulates reality (see Chapter 2.2). Only a part of the different physical and chemical characteristics of fats and oils is caused by the special characteristics of the fatty acids themselves, or by those fatty acids that represent the residual 2%. One of the main parameters influencing the characteristics of fats and oils is the degree of unsaturation of their fatty acids; this can be changed by hardening (see Chapter 6.5). The other concerns the distribution of the 10-12 main fatty acids over the three different positions of the glycerol molecule. Therefore, great efforts are undertaken to separate certain triglycerides (see Chapter 6.2) or to change their distribution in the glycerol molecule (see Chapter 6.4). Fats have a density d,, of 0.91-0.95 cmVg, a very low vapor pressure and consequently, a very high boiling point. The melting point of oils usually lies below O"C, the melting point of the highest melting fraction of fats at about 75°C. Solubility is very good in nonpolar solvents and chlorinated hydrocarbons. The main chemical reactions that occur naturally are saponification and oxidation. Fats usually are accompanied by lipids such as carotene, sterols and phosphatides. Many oilseeds contain other specific components, which usually have to be removed during processing.
2.1 Components of Fats and Oils 2.1.1 Glycerol Glycerol (propane-l,2,3-triol) is the one and only alcohol to which fatty acids are esterified into triglycerides, i.e., oils and fats. Living organisms synthesize glycerol
Fats and Oils Handbook
56
from hexose; in the body, this reaction is much faster than the synthesis of fatty acids. That is why glycerol is always available in sufficient quantities (Propjak 1953) for the synthesis of fats. The Swedish pharmacist and chemist, Scheele, discovered glycerol in 1783 when he experimented with olive oil. Chevreuil, the father of fat chemistry, gave the sweettasting substance its name, which is derived from the Greek word for sweet.
H
rrzi I
I
I
H or
n n n
H
Scheme 2.2.
Glycerol is a symmetrical triple alcohol (for physical data, see Table 2.2) and is important as the basic component of all triglycerides. However, as the one and only identical alcohol component that is present in all triglycerides, it becomes unimportant for the technology of fats and oils. The only importance is in its reesterification with fatty acids to yield very special dietetic fats (see Chapter 8.7). The situation is totally different in the technical fats market. At present, the world consumption of glycerol is -500,000 MT/y. Most of it is for the chemical and pharmaceutical industry; a smaller part is used for food, tobacco and plastics manufacturing. Since 1948, glycerol has not been exclusively produced from oils and fats; it is also synthesized, for example, from propylene (Sherwood 1960). In difficult times, e.g., during the war in Germany, it can also be produced via fermentation of saccharose or hydrogenation of saccharose and starch with nickel catTABLE 2.2 Physical Data of Glycerol (Propanetrio1)a ~~
Molecular weight Melting point Boiling point Density Refractive index Viscosity relative kinematic Solubility in water in alcohol in benzene Dissociation constant
M= m.p. = b.p. 760 = b.p.1, = D420= n ,,20 =
~
~
92.1 1 2ooC ( 6 8 O F ) 29ooC (554OF) 8 2 . K (360°F) 1.261 1 g/cm 1.4746 1759.6 (cP) 1398.1 (cP) infinitely infinitely infinitely 7.10-15
pK = aSource: Handbodc dCkmistry and Physics (1 976).
14.15
Composition, Structure, Physical Data, and Chemistry
57
alysts. The present use of glycerol in Europe is shown by Steinberner and Preuss (1987), who also further explain glycerol production. 2.1.2 Fatty Acids
Today, >200 fatty acids are known to occur in fats and oils. Only a handful have a share >3% in the triglycerides of edible oils and fats. A further handful fall in the region of 0.5-3.0%. All others exist only as traces in common oils and fats; they can be found in higher amounts in special species. The most important saturated fatty acids were discovered in the first half of the 19th century. The initial discoveries occurred around 1820 with the basic work of Chevreuil who found butyric, capronic, and capric acid as well as palmitic and stearic acid. The others were discovered by Lerch and Fehling (caprylic acid 1844-45) and Marsson (lauric acid 1842 in the fat of laurel, Luuris nobilis). Arachidonic acid was found by Gossmann (1854) in peanut oil, behenic acid by Voelcker (1848) in behenic oil. Hell and Hermans identified lignoceric acid (1880) in beech tree tar. Five years earlier, oleic acid had been identified as the most important component of fats and oils. A survey of the history of discovery and identification of the fatty acids is given by Hilditch and Williams (1964). Ucciani (1995) gives the fatty acid composition of more than 2000 plants. Naturally occurring fatty acids are usually monobasic and unbranched. They are aliphatic monocarbonic acids, mainly saturated or mono- or bi-unsaturated. Higher degrees of unsaturation occur in marine oils. In animal and vegetable triglycerides, even-numbered chain lengths between 4 and 26 carbon atoms dominate; in waxes, chain lengths up to 38 exist. In fats of microorganisms, odd-numbered chain lengths can constitute up to 15% of all fatty acids. In the beginning of fat chemistry, high amounts of C,, fatty acid (margaric acid) had been found. This later proved to be a mixture of C16 and C18 that could not be separated with the analytical methods of that time. In the following sections, fatty acids are described with emphasis on the main members of each family. Selected others are shown in a table. Detailed information on fatty acids, their sources and their properties is given by Hilditch and Williams (1964), Geigy (1968), Baltes (1975), Swern (1982), and Gunstone et al. (1986). Original citation of literature from which physical data are taken can also be found. The main fatty acids also have trivial names that allow for clear classification in the case of saturated fatty acids. For unsaturated fatty acids, cis- or truns-configuration can be deduced mainly from the trivial name. In polyunsaturated fatty acids, the trivial name gives chain length and the number of double bonds; their position and configuration is marked separately. 2.1.2.1 Structure and Nomenclature. Fatty acids are monocarbonic acids that are usually derived from aliphatic hydrocarbons and can be brought into a systematic pattern (Fig. 2.2). All dominant fatty acids of edible oils and fats belong to the
Fats and Oils Handbook
58
families of alkane- and alkene-fatty acids. Their structure and nomenclature follow the common rules of chemistry. However, the main fatty acids also carry trivial names, which are commonly used. The carbon chain is, as usual, numbered from the carbonyl-end to mark functional groups. In addition there is a consensus in fat chemistry to number double bonds beginning from the methyl-group at the tail. Following that, a prefix “n” or ‘‘a” is used with the number of the carbon atom. Four different C1, fany acids are shown in Figure 2.3 with their trivial names, chemical names, structure and sum equation. The structure of fatty acids has a great influence on their physical data. With the main fatty acids from edible oils and fats, structural differences can occur only in the position of the double bond or its configuration (cis- or trans-). The influence of these parameters on the physical properties is shown in Figure 2.4 for the C,, acids, with one double bond in different positions and for both geometric isomers. Tables 2.3 through 2 7 give the physical data and typical sources. 2.7.2.2 Saturated Unbranched Fatty Acids. The lowest homologue, acetic acid (C,) cannot be found in triglycerides. The lowest in the sequence of “real” fatty acids is butyric acid C,, first found in butter as its name indicates.The acids up to C, are liquid and are found mainly in milk fat. Capric, myristic, and lauric acid are typical for coconut oil and palm kernel oil (“lauric fats”), and palmitic and stearic acids are the most common saturated fatty acids. Table 2.3 gives physical data. 2.1.2.3 Unsaturated Unbranched Fatty Acids. These fatty acids are very special because some of them are essential for mammals, i.e., also for man. This means that the body cannot synthesize them and is dependent on an external supply (see Chapter 1.4).
Unk.noh.d 2.1.2.2 2.1.2.4
-
B R W
SubrtyII(.d
2.1.2.4
2.1.2.4
2.1.2.3.1
2.1.2.3.2
Fig. 2.2. Systematic of fatty acids.
m 2.1.2.4
Composition, Structure, Physical Data, and Chemistry
59
/OOH unbranched, di-unwtualCtnnr-9,12octsdhic add (linolelsdbnic add)CitHnOc or H~C-(CH~)~CH~CH-CHZ-CH~CH-(CHZ)~-COOH
Fig. 2.3. C,, fatty acids of different degree of saturation.
70 60
c . .
2G.././..
50
E
tranr-
E40
2
configuration
30
P 20
cisI
10
0 '
2
3 4 5 I 6 7 8 9 1 0 1 1 1 2 Position of the double bond in the C18:l fatty acid
Fig. 2.4. Melting points of CI8:, fatty acid isomers (after Kaufmann 1958 and Markley 1947).
01
0
TABLE 2.3 Physical and Chemical Data of Common Saturated Fatty Acids CnH2n02 n
Trivial name
Chemical name
Molecular weight
4 6 8 10 12 14 16 18 20 22 24 26
Butyric Caproic Caprylic Capric Lauric Myristic Palmitic Stearic Arachidic Behenic Lignoceric Cerotic, Phthioic
n-Butanoic mHexanoic n-Octanoic n-Decanoic n-Dodecanoic n-Tetradecanoic n-Hexadecanoic n-Octadecanoic n-Eicosanoic n-Docosanoic n-Tetracosanoic n-Hexacosanoic
88.1 1 116.16 144.22 172.27 200.32 228.38 256.43 284.49 312.54 340.59 368.65 396.71
Melting point (T) -7.9 -4 16.7 31.3 43.5 54.4 62.9 69.6 75.4 79.9 84.2 87.9
Boiling pointlpressure (“Umm Hg)
Density Refractive index (g/mL at T) n,Yt (unitsPC)
163.51760 205.81760 239.7l760 269/760 2251100 250.5/100 268.511 00 2981100 3281100 306160
0.9387120 0.9290120 0.9088/20 0.8858140 0.8830120 0.8584160 0.8487l70 0.9408120 0.82401100 0.82211100 0.82071100 0.81981100
-
64110 99110 124110 152110 130.511 149.21 167.51 183.611 205.011 257110 272110
-
-
1.39906/20 1.41 635120 1.4285140 1.42855120 1.41 83/82 1.4308/60 1.4276180 1.4297180 1.4250/100 1.42701100 1.42871100 1.43011100
Acid number 637 483 389 325 280 245 218 197 179 164 152 141
2 G: rLJ
a-
0 i z $
[ 3
Composition, Structure, Physical Data, and Chemistry
61
2.1.2.3.7 Monounsaturated fatty acids. The shortest chain unsaturated fatty acid that has been found to date in natural fats is caproleic acid (Clo:l),traces of which have been identified in milk fat. The only monounsaturated fatty acid that occurs in substantial amounts is cis-9-octadecenoic acid, which has the trivial name of oleic acid (for sources and derivatives, see Hilditch and Williams 1964). All other acids occur on average at much lower percentages. This does not mean, however, that their contribution to the fatty acid spectrum of specific sources must be low. Cruciferae, for instance, contain high amounts of cis-13docosenoic acid, i.e., erucic acid (older varieties of rape contained up to 70%). Generally monoenoic acids are found as follows: Cl0:, to C18:1,in milk fats; CI6:, in seed oils. to CZ4:*, in marine oils; and up to Only in special plants have other isomers been found, e.g., cis-6-octadecenoic acid makes up between 4 and 97% (e.g., dill, caraway, persil) of total octadecenoic acid isomers in apiaceae varieties, cis-11-octadecenoic acid up to -20% (mallow) in malvaceae (Seher 1982). Table 2.4 presents the data for monounsaturated acids.
2.1.2.3.2 Polyunsaturated fatty acids. In addition to the cis- or trans-isomers of monoenic acids, polyenic acids offer further potential for isomerization, such as cis- and trans- in one molecule, and for isolated or conjugated double bonds. Polyunsaturated fatty acids (see Table 2.5) with isolated double bonds appear in all edible fats and oils. In native vegetable triglycerides, only all-cis isomers are found, but they are also present in animal fats. However, because the body cannot synthesize them, they are obtained from vegetable food. Highly unsaturated fatty acids occur in organ fats and marine oils. Conjugated polyunsaturated fatty acids are found almost exclusively in nonedible oils and fats. Alkyne fatty 'acids are extremely rare. The most important polyunsaturated fatty acids are linoleic and linolenic, both in amount and in their essential role in the human (animal) diet; arachidonic acid also has this essential role, although it occurs in much smaller amounts. Clupadonic acid is included in the table for its occurrence in fish oils (Table 2.5). 2.7.2.4 Other Fatty Acids. In addition to the unsaturated fatty acids mentioned above, there are alkyne fatty acids, branched fatty acids, alicyclic fatty acids and substituted fatty acids. These subgroups have no importance at all for edible fats. Some are included in the table as examples. Alkyne fatty acids are especially rare. For example isanic fatty acid (17octodecene-9,ll-diyonic acid) is mentioned, found in boleko oil (Baltes 1975) and tariric acid (6-octadecynoic acid), which occurs in piramnia species. Branched fatty acids are found at trace levels in many fats, predominantly animal fats. Substituted fatty acids are rare but equally important. Hydroxy fatty acids account for 53% of the cerebrosides (Chibnall et al. 1953, Mislow and Bleicher 1954) and are very important for brain function.
TABLE 2.4 Physical and Chemical Data of Common Monounsaturated Fatty Acids C"HZ",O2
n
Trivial name
12 Linderic (Laudeic) 14 Myristoleic 16 Zoomaric 18 18 18 18
Oleic Elaidic Petroselink Vaccenic 20 Cadoleic 20 Gondoic 22 Erucic
Molecular weight
Melting point
CH,
5-Dodecenoic
n-9
9
198.31
1.C1.3
17C173113
9-letradecenoic 9-Hexadecenoic (Palmitoleic) 9c-oaadecenoic 9fOaadecenoic 6c-Octadecenoic Ilt-Octadecenoic 9-Eicosenoic 11-Eicosenoic 13-Docosenoic
n-5 n-7
5 7
226.36 254.42
4.5 0.5
183-1 86/14 2 1a22011 5
From
o
("0
(g/mL at "c)
Refractive index n & t (unitsPC)
-
0.913W15
1.4535115
128
283
144m.6 1 8 ~8311 1
0.9130115 0.9003115
1.4549115
112
248
1.4587/20
100
221
1.4582/20 1.4499145 1.4535/47 1.4439160 1.446W50 1.4597/20 1.4W64
90
199 199 199 199 181 181 166
Boiling point pressure/ ("Umm Hg)
Chemical name
Density
Iodine Acid value number
2' i: (L,
i% z
(L,
3
n-9 9 n-9 9 11-12 12 7 n-7 n-11 11 n-9 9 n-9 9
282.47 282.47 282.47 282.47 310.52 310.52 338.58
13 51 32-33 44 24.5 25 33.5
203-20515 28fY100 234115 lW1851O.5 20~210110. 14ai52m.15 172-1 73/3 17W0.1 32W60(d) 203-20511 281130 252-254112
0.895/15 0.85/20 0.8824135
0.8882f25 0.82W100 0.8W55
90
90 90 82 82 75
g
TABLE 2.5 Physical and Chemical Data of Common Monounsaturated Fatty Acids C"H2"-2O2 n
Trivialname x
12 Linoleic 18 a-Linolenic 18 ylinolenic 18 Elaeostearic 20 Arachidonic 20 Timnodonic 22 Clupadonic 22 Cervonic
Miscellaneous n Trivial name 18 Ricinoleic 24 Nisinic 24 Nervonic 24 Cerebronic 24 2-Hydroxynervonic
Chemicalname
4
9,12-Octadecadienoic (LA) 6 9,12,1-decatrienoic (ALA) 6 6,9,12-oaadecatrienoic (CIA) 6 9~,llt.l3t-Octadecatrienoic 5,8,11,1 &Eisosa8 tetraenoic (AA) 10 5,8,11,1417-Eisc+ sapentenoic (EPA) 10 4,8,12,15,19Docosapentenoic (DPA) 12 4,7,10,13,16,19-W cosahexaenoic (DHA)
Chemical name cisl2-Hydroxy9-octadecenoic 4,8,12,15,18,21Tetracosahexaenoic 15-Tetracosenoic 2-Hydroxytetracosanoic 2-Hydroxy15-tetracosenoic
From CH, o
Molecular weight
Melting point
0
n-6
6
280.44
-5.2
n-3
3
278.42
-11
n-6
6
278.42
n-5
5
n-6
Refractive Density index nDM (g/ml at "C) (uniWC)
Iodine value
Acid number
0.9020/20
1.4699/20
181
200
0.9046RO
1.478ORO
2 74
202
-
2 74
202
0.9028/50
1.51 12150
274
202
0.92 19/20
1.4824/20
304
184
1.4977R3
-
186
0.9290RO
1.5014RO
464
170
-
1.5017/20
-
172
Density (g/mLat "C)
Refractive index nDVt (uniWC)
Iodine value
Acid number
0.9403/27
1.4716RO
85
188
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- _
Boiling point I pressure (Wmm Hg) 229-230 I16 23C232 I 17
129 10.02 125 10.05
4
-
-
278.42
49
6
304.46
49.5
235 I 12 217-220 I17
n-3
3
302.45
-
-
170 /1.3 169-171 m.15
n-3
3
330.50
<-78
-
n-3
3
328.49
<<-75
-
Melting point
Molecular weight
n-9
9
298.47
5.5
245 I1 0
n-3
3
356.55
-
n-9
9
366.64
112.5 113.5 40.541 99.5100.5 65
_ _ _ 384.65 n-9
9
382.63
-
-
207-2 12 /2
-
Boiling point I pressure(WmmHg)
From CH, o
K)
-
-
.
Fats and Oils Handbook
64
TABLE 2.6 Occurrence of Minor Fatty Acids in Different Oils ( O h ) In marine oil: herring oila c16:206 0.4 c18:3@6 O.3 0.1 0.4 C2,:403 0.4 in vegetable oil: rapeseed oilb c14:lo9 tr c14:lw7 0.007 c15:1,10 0.02 C1.j:lolo 0.01 c17:O 0.05 C17:1, 0.06
C16:me7
0.3
C162o4 C20:40b
In animal fat: lardb C13:o 0.08 C15:o C23:0br] 0.008 C24:obr] cl5:l 0.01 C17:1 C200br4 0.O2 C22:0br4
0.02 0.004 0.22 0.02
c16:204
Oh
c16:304
0.4
c16:401
c18:303
0.9 0.2
c200
o.l
c2D:lo9
C22:503
0.4
C24:1
C14:loS
0.004
c14:206
tr
c16:1~7
C190
0.02
Cjcj:,oio
0.02 0.29 0.02
c14:303
C15:l&
C1,:o
0.29 0.02 0.06 0.03
C1,:o
0.03 0.02 0.004 0.03
C22:206
C25:0brl Cig:, C24:0br4
C26:&rl C21:1 C260br4
0.4 o.2 Phytanic 0.2
o.6 0.3 0.4
c18:105
tr 0.07
c15:0
C16.06 C20.206
0.20
C2~306
C21:o
0.004 0.02 0.02 0.09
C23:o
c12:1 C22:3 C28:0br3
c202
C ,:,i
c]4:] C22:5 C28:0br4
0.02 0.13 0.20 0.02 0.03 0.02 o.20
aSource: Sigurgisladottir and Pilmadottir (1993). bSource: Sebedio (1 979). cSource: Iverson eta/. (1 965).
TABLE 2.7 Occurrence of Fatty Acidsa Saturated fatty acids CnH2nO2
n 4 6 8
Trivial name Butyric Caproic Caprylic
10 12
Capric Lauric
14
Myristic
16
Palmitic
18
Stear ic
20 22
Arachic Behenic
24
Lignoceric
26
Cerotic
Occurrence in common oils and fats Sources with remarkable moportion (% of total fattv acids) milk fat (3-5) milk fat (2-31, coconut oil (21 milk fat (a), babassu oil (3-51, coconut oil (4-61,palm kernel oil (13), cuphea painter; (65-75), hookeriana (-65) milk fat (3-4), babassu oil (4-7), coconut oil (6-9), cuphea species (88-92) coconut oil, palm kernel oil (45-SO), Litsea sebifera (-95), Cinnamonium inners (-95), cuphea tolucana (-65) coconut, palm kernel, babassu oil (15-1 7), herring oil ( 4 4 , nutmeg oil (177) Gymnacranthera contracta (-85), Scyphocephalum ochocoa (-80), cuphea palustris (-65) coconut oil, palm kernel oil, babassu oil, sesame oil (7-10), cottonseed oil (1 7-25), milk fat (33-38), lard (20-30), tallow (25-40), herring oil (7-1 3) menhaden oil (15-30) Myrica carolinensis (-€lo),Ochna sqarrosa (-73, Rhus succedanea (-70) lard (16-24), tallow (15-30) Canarium schweinfurthii (85), Garcinia species (60-65) peanut oil (5-7), milk fat (2-4) nephelium species (>30) peanut oil ( 5 4 , mustard seed oil (11,s) lophira species (20-35), Psochocarpus tetragonolobus (-20) peanut oil (13), mustard seed oil (Il), adenanthera pav. (-30), eleagnus angustifolia (-2O), tamarindus indica (-20) pentachletra macrophyllia (-5), rumex pseudonatronatus (-3), vermonia anthelmica (-3) Continued
65
Composition, Structure, Physical Data, and Chemistry
TABLE 2.7 (Continued) Monounsaturated fatly acids Occurrence in common oils and fats CnH2n02 n Trivial name Sources with remarkable proportion (YOof total fatty acids) 12 14
Lauroleic Myristoleic
16
Palmitoleic
18
Oleic
18 18 18 20 20
Elaidic Petroselin ic Vaccenic Cadoleic Eicosenoic
22
Erucic
sperm whale oil (4), thohaku nut oil milk fat, tissue fat, liver oil ( I l ) ,whale oil (2,5), sperm whale oil (14) pygnantus kombo (20-23) milk fat, tissue fat (<5), fish oil (go), whale oil ( I 1 51, sperm whale oil sinuata (-70), doxantha unguis (-65), plumeria alba ( ~ 2 7kermadecia ) (55-60) rapeseed oil (LEAR 55-65), peanut oil (45-65), sesame oil (35-50), corn oil (40-50), olive oil (55-85), goose fat (50-65) amaranthus trivolor (-go), garcinia multiflora (-88), corylus avellana (-85) body fat of ruminants Apium leptophyllum (-85), Deverra aphylla (-85), Umbelliferae (1 8-70) butter fat (<2.5), beef tallow sperm whale oil (519) jojoba oil ($30), mustard seed oil 6131, cod-liver oil ($14) Limanthes species (60-75) rapeseed oil (HEAR 40-65), mustard seed oil (I501 Crambe abbessynicum (-60), hispanica (-55)
Polyunsaturated fatly acids Occurrence in common oils and fats CnH2n02 n x Trivial name Sources with remarkable proportion (O/O of total fatty acids) 18
4 Linoleic
18
6 Linolenic
18 20 20 22
6 8 10 10
Elaeostearic Arachidonic Timnodonic Clupadonic
22
12 Cervonic
safflower oil (<80), sunflower oil (S75), poppy seed oil (<65) Myrianthus species (88-94), betula platyphylla (-88) herring oil (go),menhaden oil ($30), linseed oil (f47) Acacia lenticularis (-801, Euphorbia species (75-78); (-linolenic: barley 1-2) Aleuritis species (65-851, Parinarium excelsum (-60) cod-liver oil (125), herring oil (I30), menhaden oil ( 9 9 ) fish oils, fish liver oil cod-liver oil (celO), herringoil (-23), menhaden oil (<12), sardine oil (S14) fish oils
Special fatty acids n Trivial name
Occurrence in common oils and fats Sources with remarkable proportion (% of total fatty acids)
18 24 24 24 24
castor oil (I951 tunny oil brain cerebrosides (701, cardamine graeca (> 50), tropaeolum spp. (> 40) brain cerebrosides (15) brain cerebrosides (12)
Ricinolic Nisinic Nervonic Cerebronic 2-Hydroxynervonic
~~
aFor the fatiy acid composition of thousands of fats and oils of animal and vegetable origin, see among others Hilditch and Williams (1964) and Ucciani (1995).
66
Fats and Oils Handbook
Fatty acids that do not occur in edible fats and oils (with a few exceptions) are not dealt with in this chapter. Detailed information is given by Hilditch (1964) and Geigy (1%8), for instance.
2.2 The Structure of Triglycerides After it had been generally accepted at the beginning of the 20th century that oils and fats were composed of three identical fatty acids bound to one glycerol molecule, it was later found that in reality mixed glycerides predominate (if not, the fatty acid composition does not allow for their formation). Assuming as a model a fat that consists simply of two fatty acids A and B, only two main possibilities exist to distribute these acids to the glycerol molecule (G): (i) Assume that only single-acid triglycerides are formed, resulting in GA, and GB,; (ii) allow for all possible combinations, yielding GA,, GA2B, GAB, and GB,. In the second case, structural isomers of GAzB and GAB, have to be added, namely, (iii) GAAB, GABA and GBAA as well as GBBA, GBAB and GABB. Taking the possible distributions of these two fatty acids A and B on the glycerol molecule, three theoretical models occur that have been the basis of all research about interesterification. These models assume even distribution, minimal distribution, and statistical distribution of the fatty acids in the triglycerides. Assuming even distribution (Fig. 2.5) means that every triglyceride contains one of the two different fatty acids, as long as supply lasts. The model also says that only two different triglycerides exist at the same time but that all four structures given (ii) exist, across the whole range between 0 and 100% of each of the acids A and B. For example, with one third of all acid being A, the mixture would exclusively be 100% GAB,; with one half of all acids being A, it would consist of 50% each GAB, and Proportion of triglyceride type
[%I
0 33.3 66.7 Proportion of fatty acid B (fatty acid A-100-6)
100
[mol%]
Fig. 2.5. Triglyceride distribution of di-acid triglycerides assuming even distribution.
Composition, Structure, Physical Data, and Chemistry
67
GBA,, no other triglycerides being present. Following the model of minimal distribution, only the two single-acid triglycerides GA, and GB, would exist. Their share in the mixture would be equal to the share of the fatty acids A with respect to B (Fig. 2.6). If the triglycerides were synthesized in v i m , the minimal distribution would certainly be excluded for theoretical reasons. The carbon chains of fatty acids are not very voluminous and because they are very similar to each other (except for the chain length), no special distribution would clearly be preferred for steric reasons. Chemical synthesis would lead to almost statistical distribution. That indicates that the probability of occurrence of the four triglycerides GA3, GA2B, GAB,, GB, from (ii) with their isomers (iii) and their relative share of the mixture should be in proportion to the share of A and B in the mixture (Fig. 2.7). Further, it would predict that the acids should be equally distributed to the three positions 1-, 2- and 3of the glycerol molecule, although a differentiation between the 1- and 3-position would not be possible. These distributions, derived from purely theoretical considerations, do not occur in nature because the synthesis of fats does not follow statistical approaches; rather, it is carried out by enzymes whose highly specific catalysis of reactions is determined by blueprints anchored in the genetic information of the animal or plant. Apart from new varieties or new crop species, the genetically steered fatty acid distribution of natural fats and oils can be influenced only to a very limited extent (climate, feeding). One of the proofs for a nonstatistical blueprint is that a natural triglyceride has been found that consists of three saturated fatty acids even when the total of saturated fatty acids is <25%. A significant amount of work has been done to determine the pattern of triglyceride composition or at least some basic principles. Methods to calculate the fatty acid distribution in oils and fats have been given by Litchfield (1973). Mattson and Volpenheim (1961) and Proportion of triglycerlde type (961
60 -
0
33.3
66.7
100
Proportion of fatty acid B (fatty acid A=l00-B) [rnol%]
Fig. 2.6. Triglyceride distribution of di-acid triglycerides assuming minimal distribution.
Fats and Oils Handbook
68
0
25
50
75
Proportion of fatty acid 6 (fatty acid A=100-B)
100 [mol%]
Fig. 2.7. Triglyceride distribution of di-acid triglycerides assuming statistical distribution. Mattson (1963) confirmed the correctness of earlier work from a sample of 30 vegetable oils and fats, describing a predominant distribution of c16:O and C18:ofatty acids to the 1- or 3-position. Analyzing these results, it is evident that in vegetable oils and fats, saturated fatty acids are esterified to the 1- and 3-position as long as this position is available. After that, the residual fatty acids are statistically distributed over the free positions. As a result, the 2-position is occupied mainly by unsaturated fatty acids (Mattson 1963). Apart from its influence on the physical properties, the position of the fatty acids in the molecule also allows a distinction to be made between vegetable and animal fats. In animal fats, the synthesis of triglycerides does not follow the above pattern. Therefore the 2-position is not under proportionally occupied by saturated fatty acids. On the contrary, a slight preference for saturated fatty acids in that position can be found. As a result the ratio of c16:oin the 2-position to total c16:ois significantly different in vegetable and animal fats (Table 2.8). The significant difference between the ratio for vegetable fats and oils (50.3) and the one for animal fats (10.5) is also evidence for the thesis that statistical distribution of the fatty acids does not occur in nature, but that the distribution is genetically steered. From this evidence, Kartha (1962) developed a model that combines statistical and even distribution. This so-called restricted statistical distribution reflects reality much better (Fig. 2.8) than any other model. However, only a few fats come close to this model. The Kartha model corresponds very well to the analytical data for linseed oil or apricot kernel oil. For other oils, deviations from the model must be stated; however, in some cases, these are minor deviations only, and no other model are has been able to come as close to reality.
Composition, Structure, Physical Data, and Chemistry
69
TABLE 2.8 Ratio of Palmitic Acid in 2-Position to Total of Palmitic Acida Ratio (mol %) C16:O in 2-position C16:O total
Oil
0.07 0.08
Cottonseed Olive Peanut Rape Soybean Sunflower Palm
0.08 <0.10 0.1 7 0.1 7
0.25
Fat Cocoa butter Coconut Beef tallow Mutton tallow Lard
0.07 0.1 3 0.47 0.50 0.80
aSources: Mattson (1958, 1953 and 1964), Litchfield (1970 and 1971) and Gunstone and Padley (1965).
To estimate the physical properties of fats and oils, the triglyceride composition is important. According to the purpose of the characterization, the triglyceride composition can be globally indicated by the sum of the chain lengths of the fatty acids esterified to the glycerol or by the sum of double bonds of the whole triglycProportion of triglyceride type
100 80 60
n I
\
[%I
/
40 20 0 0
25
50
75
100
Proportion of fatty acid B (fatty acid A-100-8) (rnol%]
Fig. 2.8. Triglyceride distribution of di-acid triglycerides assuming restricted statistical distribution (after Kartha 1951).
70
Fats and Oils Handbook
Fig. 2.9. Triglyceride composition of vegetable oils (after Litchfield 1973).
eride (Figs. 2.9 and 2-10>.Also, detailed analyses with identification of the three fatty acids exist (for individual oils/fats see Chapters 3 and 4).
2.3 Physical Characteristics The physical characteristics substantially influence the properties of use of oils and fats; chemical properties are of comparably much lower importance because they
Fig. 2.10. Triglyceride composition of fats and oils (after Litchfield 1973).
71
Composition, Structure, Physical Data, and Chemistry
are more important for stability. For a complete understanding of oils and fats processing, knowledge of the physical properties is also important. Melting points and crystal modifications influence fractionation and margarine production; specific density and heat, viscosity and heat of crystallization are of interest for plant designs; structure of triglycerides is required for interesterification; knowledge of solubility is essential for oil extraction and wet fractionation; and vapor pressure and boiling points are needed for deodorization. Physical data are given in the following paragraphs (those that are of specific interest for a certain process only, see the relevant chapters). 2.3.1 Melting Point and Crystal Modification
For fats that require special characteristics (e.g., extra plasticity) and to be able to process them (in margarine making for example), a knowledge of crystal modifications is of importance. Triglycerides exist in three polymorphic modifications, called the a-,p- and P’-modifications. Using infrared (IR) spectral evidence, Chapman (1957b and 1960) classified the crystal structure as follows: a-hexagonal, p-triclinic, and p’-orthorhombic. As with all other polymorphic substances, fats change conformation at specific temperatures. Thus, they follow the path from the thermodynamically least stable to the most stable structure. There is also an amorphous, glasseous form that originates from chilled melts. It is called y-modification. From there, the a-fonn is reached, passing into p’ and p. The transition between modifications is irreversible because their melting points are quite different; an example is shown for single-acidtriglycerides in Table 2.9. Other authors give slightly different values; however, these do not change the picture substantially. TABLE 2.9 Melting Points of the Different Crystal Modifications of Single-Acid Saturated Triglycerides GA3a Melting point of modification (T)
Fatty acid
A
c 8:O c1o:o c12:o c14:0
C160 Cl8:O C18:l CK:, c1&3
C20:O C22:l
a
B’
B
-1 5 15 33 45 55 -32 -45 -44.6 62 17
-2 1 18 35 46.5 56.5 65 -1 2 -1 3 69 25
8.3 31.5 46.5 58 63.5 73.1 4.9 -1 3 -2 4 78 30
aSources: Loskit (1928),Clarkson and Malkin (1934), Wheeler (1940L and Wan (1 991 ).
Fats and Oils Handbook
72
Similar effects can be observed with bi-acid symmetrical triglycerides (characterized as GA,B) showing fairly large differences in their melting points (Table 2.10). The tables show that not only do melting point differences decrease absolutely in the sequence y + p’ 3 p, but also relative to each other as chain length increases. The respective modification influences the crystallization behavior, e.g., speed of nucleation and crystal growth (seeChapters 6.2 and 8). Riiner (1970) shows the transition between modifications in the cooling curves of a hardened oil and a fat (Fig. 2.1 1). The points of the first (TI) and second (T,) deviation of the lines emphasize the building temperatures tl of a-crystals from the melt and the transition temperature from a - to p’-modification. The points, T,and T,, differ from oil to oil (Table 2.11). In mixed-acid triglycerides, the melting point depends not only on the fatty acid composition, but also on the position to which the fatty acids are esterified. For bi-acid triglycerides, a different picture results from the position of the acid A in GAB,, i.e., in the 1- (3-) or 2-position. This determines whether the triglyceride is symmetrically built or not (Table 2.12). Numbers in the diagonals of the two parts of the table stay the same, of course, because they represent single-acid triglycerides that are exactly the same. For distearates with different second fatly acids, this relationship is graphically shown in Figure 2.12. The difference between the melting points of bi-acid triglycerides may be as great as 17°C; however, the values are very different for different acid combinations (Table 2.13). A similar scatter range as that for saturated acid triglycerides is observed for those containing mono- and di-unsaturated acids. Table 2.14 shows the numbers for triglycerides composed of two equal saturated fatty acids ( S ) and TABLE 2.1 0 Melting Point of Di-Acid Symmetrical Triglycerides CBAB and GABA (A = Palimitic or Stearic Acid) in Relation to the Crystal Modification and the Chain Length of the Acids A and B Melting point (“C);fatty acid A in BAB (2-position)
Fatty acid B2 (1,3-)
A = palmitic acid (C16:o) trigyceride modification
A = stearic acid (Cley0) trigyceride modification
Y
a
p’
P
Y
a
p
c12 c14
6 19 38
50
40 45.5 60 65.5 68
5 21 33 49
Cl8
36 42.5 55 56.5 64
34 38
cl 6
27 35 49 45 56
40 43 53 65 65
44.5 61.5 55 68 72.5
53 58 59.3 64 65
57 60.5 63.8 68 72.5
ClO
c12 cl 4 cl 6 C18
59 55
P
Melting point (“C); fatty acid A in ABA (1,3-position)
B (2-) Cl 0
-
47
’
20 34 37
49
42 47 46 45 59
48 50 55 56.5 65
51.5 53.5 60 65.5
68
30 36 44.2 50
-
47 52 56.6 56 55
Composition, Structure, Physical Data, and Chemistry
Temperature ["C]
\+IT
["FI
Ranasaad \Coolingnil
0
5
73
Rate
10 15 20 25 30 35 40 45 50 55 60
1
t -At1
I '2
Time
Iminl
Fig. 2.11. Cooling curves of palm kernel and hardened rapeseed oil (after Riiner 1970).
one unsaturated fatty acid (U) in different positions. In addition to the heat of fusion when melted, there is heat of transition when the fat crystals transform from one to the other crystal modification. Charbonnet and Singleton (1947) give these values for single-acid triglycerides that may indicate an order of magnitude (Table 2.15). The transition time from one crystal modification to the other has been measured by Sat0 and Kuroda (1987) for tripalmitin, dependent on the temperature in an interval from 42 to 52'C. The melting points of the modifications were a = 45'C, P' = 56.5"C and P = 65.5"C. Figure 2.13 shows the transition as follows: from the molten state via all modifications to the P-modification (liquid 3 solid) from a-to p-crystals in solid state (solid + solid) from the molten state of a-crystals to P-crystals (liquid + solid) from p'-to P-crystals (solid a solid) They found that crystal formation for each modification is much faster than the transition of this crystal modification into the more stable one at that temperature. The transition time from a- to P'-modification is described by Riiner (1970) for native and hardened fats. The ordinate of the graph (Fig. 2.14) shows the lifetime of the a-modification. The bars parallel to the abscissa represent these lifetimes; their endpoints show the melting points of the a-form (left endpoint) and the v-form (right endpoint). Transition temperatures are marked on the line TT. The influence of the composition of triglyceride mixtures on their melting and solidification points are shown in Figure 2.15 for the model-system tripalmitidtri-
74
'
Fats and Oils Handbook
TABLE 2.1 1 Transition Points AT, (Melt -+ a-Modification) and AT2 (a + @Modification) and Transition Times At of Fats and Oils Oil/fat
AT1 YC)
AT2 ("C)
33.0 18.0 15.0 30 18 18 19
31.5 16.0 15.0 27.0 18
Beef tallow Cocoa butter Coconut oil Lard Palm kernel oil Palm oil Shea butter Fat (hardened to "C)
AT1
8 14 0 8 0 960 10
<8
15
ATl ("C)
AT2 ("C)
21.5 18.5 26.0 23.0 25.0 29 24
21.5 18.5 26.0 14.0 20.0 24.0 24
Coconut (34) Cottonseed (34) Palm kernel (37) Peanut (33) Peanut (37) Rape (37) Soybean (37)
At (min)
("F)
91.4 64.4 59.0 86 64 64 66
At (min)
AT1
AT2
88.7 60.8 59 80.6 64 ~ 4 6 59 AT2
(OF)
70.7 65.3 78.8 73.3 77.0 84 75
0 0 0 23 13 10 0
(OF)
(OF)
70.7 65.3 78.8 57.2 68.0 75.2 75
aSource:Riiner (1970).
TABLE 2.1 2 Melting Point of the &Modification of Saturated Di-Acid Triglycerides GAB2 in Relation to the Chain Length of the Acid A in 1- or 2-Positiona Fatty acid B i n BAB c4 c6
Melting point ("C); fatty acid A in BAB (2-Position) being c6
c4
m -1 4.G
[ -25
oa
-1.2a 18.7a 38.8 40.1 44.5a 53.1
a Oa
c16 Cl8
Fatty acid B in ABB c6 C8
ClO c12 c14 c16
C18
c10
a Oa
<
-5.0a 8.3 20 30.2 42.5 48.5a 51.8
4.P 15.0a 31.5 38.5 43.5 51.5 57
I
c
c12 c14
noa
c8
-1 1 .oa 43.5a 46.5a 54.8
I 1
1 [
c14
c12
1 I
-1 la 4.0a 21.0a 37.5 46.5 50 53.5 60.5
1 I
3.7a 11.0 25.P 34 48 57 60 63.8
c16
j
1
18 18.la 28.0a 40 45.5 60 65.5 68
c18
1 1
15 32 32 44.5 61.5 55 68 72.5
1
Melting point ("C); fatty acid A in ABB (1-Position) being c4
-1 1 .oa 14.02 36.0a 40.03 43 49
Talcdated by Werdorp.
ClO
c6
&I\
c12
~~~~~
27.0a 34.0a 39 21.2
29.0a 38.0a 48.P 32
34.5 35
46.5 43.5 46.5 45
!F giF , c14
~
c16
c18
i.6,
46.5 54 56
65.6 62.5
65.0 72.5
75
Composition, Structure, Physical Data, and Chemistry
Fig. 2.12. Influence of the fatty acid A on the melting point of the symmetrical triglycerides C,8-A-C18and the unsymmetrical 1 8-CI8-A (after Bailey 1950).
laurin. Theoretical (---) and measured (-) values are compared. In this mixture, the highest depression of the melting point is found at 28% trilaurin. Natural fats and oils, however, are such complex mixtures of different triglycerides that a multitude of effects superimpose upon each other so that individual effects can scarcely be seen. If the amount of crystallizing matter is graphically shown against crystallization time, an S-shaped curve is obtained. Berg and Brimberg (1983) explain this curve, two straight lines connected by an intermediate line, with the kinetics of the process. According to their investigations, crystallization begins with the formation of small crystals (phase I); later these crystals agglomerate (phase II). This is equivalent to flocculation in dispersions and can be described with the same mathematical equations. The crystal flocculates grow and then crystal growth starts again (phase III). TABLE 2.1 3 Difference in Melting Points (“C) of the Positional Isomers of Saturated Di-Acid Triglycerides GA2B Between Positions 1- or 2- of the Fatty Acid B Fatty acid A, in GA,B Fatty acid B
Cl 0 0
C12:O
c14:0
cl 6:O
C18:O
c6:0 G O
24.1 8.3
6.2 1.7 3 .O
6.0 4.5 0.0 3.5
16.0 23.5 6.0 0.5 3.0
9.1 4.2 6.0 1.8 1.8
Cl 0 0 C12:O c14:0
C160 c16:0
7.5 0.5 5.0 3.5
4.5 2.0 16.5
6.0 1 .o
3 .O 5.5
Fats and Oils Handbook
76
TABLE 2.14 Melting Points of the P-Modification of Di-Acid Triglycerides in Relation to the Position of the Unsaturated Acid Ua Unsaturated fatty acid U In USS (1-position) being In SUS (2-position) being Oleic Elaidic Linoleic Oleic Elaidic Linoleic
Saturated fatty acids S2 C8 C l0
-1 4 4 16 25 34.8 38.5
c12 c14
c16
C18
3 15 27 39.5 50.2 61 ,1
-12.5 -0.5 15.5 20.5 26.5 32.5
-1 3 6.2 16.6 26.5 37.5 44.3
-5.6 0.5 6.5 13.5 19 23.5
c12 c14
cl6
Cl8
41 25 35.5 40 40.3 59.6
-1 7.0 -2.0 11.0 21.3 28.5 41.5
In USU (1.3-position)
In SUU (1.2-position)
Fatty acid S C8 ClO
15.9 25.8 36.6 46.1 55 61
u0
4.2
NO
0
-1 1.5 -8.5 -3.5 5.5
5.6 12 19.6 23.9
34.0 35.4 38.7 43.0 44.5 50.1
-1 0.0 -1 0.0 -7.3 -3 .O -2.2 7.0
aCalculatedby Wesdorp.
Essential for the production of fat and fat products is their crystallization time, the time that determines the necessary residence time in a cooler (crystallizers, see Chapter 8.2). For the time span between reaching crystallization temperature and the beginning of crystallization, Blanc (1969) gives the following values: coconut oil lard shea butter
3 min 14 min 45 min
palm oil (hardened) palm oil
5 min 27 min
Crystal modification also influences the specific density. For example, Wan (1991) gives the following values for tristearin: d3,a = 1.014,d3&' = 1.017, and d3,P = 1.043. TABLE 2.1 5 Heat of Transition from a-to P-Modification of Saturated SingleAcid Triglyceridesa Trical/g
I&
kcal/rnol kJ/rnol at (OF) at ("C) aSource: Charbonnet (1947).
rnyristin c14:0
palrnitin Cl60
stearin Cl8.0
-12.6 -52.75 -9.1 1 -38.14 90.0 32.3
-1 3.3 -55.68 -1 0.74 -44.97 112.5 44.7
-13.7 -57.36 -12.21 -51.12 129.2 54.0
77
Composition, Structure, Physical Data, and Chemistry
42
43
44
45
(108°F)
46
47
48
Temperature
49
51
50
["C]
52 (1 26°F)
Fig. 2.13. Transition times from a- to P'-modification in tripalmitin (after Sat0 and Kuroda 1987).
2.3.1.7 Melting Points of Mono- and Diglycerides. Melting points o f monoand diglycerides (that are produced from fats, see Chapter 8.9) lie 10-20°C above those o f their source fats. They follow a uniform pattern. Table 2.16 gives some examples. It can clearly be seen that melting points rise following the line tri-,di-,
Lifetime of (y -modification [min] Peanut oil
m
Rape 39
A
25 Rape 37 Cocoa bMer
15
Shea butter'
Cottonseed 33 Sunflower 33 Soybean 37
Tallow
3 TT
-5
10
14
18
22
(50"F) End points of bars:
26
30
34
left: (y --->B '-modification
38
(1 00°F)
["c]
right: melt --->(y-modification
Fig. 2.14. Lifetime of the a-modification of triglycerides as well as transition temperatures (TT) from the melt to the a-modification (right) and from the a- to the P-modification (left) (after Riiner 1970).
Fats a n d Oils Handbook
78
(185.F)
Temperature ["C]
7 * ('(re
74
Trlpalmltln / Tristearin 70 -
Cloud point
(144'F)
t2P..
60 - x[%] = 0
20
40
60
80
100
0
20
40
Palm oteln x) /
Tristearin x) I Tripalmitin (100-x)
Palm kernel OW \lCIO-x)
Fig. 2.15. Melting points and solidification points of the system tristearinkripalmitin (after Joglekar et a/., 1928 and Watson, 1930); cloud point of the system palm olein/palm kernel oil (after Kun and lbrahim 1991).
monoglyceride. Furthermore, the influence of double bonds in the fatty acids can be seen (melting point drops). Mono- and diglycerides are used as emulsifiers. When storing blends of monoand diglycerides with oils (see Chapter 8.4), their significantly higher melting points must be noted in order to keep all components of the mixture liquid, thus avoiding crystallization, separation, and settling of the emulsifier (partial glycerides). TABLE 2.1 6 Melting Points of Single-Acid Mono-/Diglycerides; P-Modificationa Melting point ("C)
Fatty acid C" c6:0
C8:O
c1o:o c1z:o c14:0 cl 6:O
C18:O c18:1 cl 8:2 c18:3
C,-C,-C, -2 5 8.3 31.5 46.5 57 65.5 72.5 4.9 -13.1 -24.2
C,-OH-C,
44.5 57.5 65.5 73.2 78.2 25.8 -2.6 -12.3
C,-C,-OH
-27 40.8 55.5 62.8 71 .O
C,-OH-OH
OH-C,-OH
19.4
-8
40
29.8 40.4 51 61.2 69.0 75.2 23.5 8.9
53 63 70.5 77.0 81.5 35.2 12.3 15.7
aSources: Bailey (1950), Baur (1 949), Eckey (1954), Hartmann (19581, Martin (1953), Chapman (19571, Filer (1946), Daubert and Lutton (1939, 1944 and 1947), Wheeler (1940), Malkin (1936 and 1954) and Henkel and Cie (1971).
79
Composition, Structure, Physical Data, and Chemistry
2.3.2 Other Physical Data 2.3.2.1 Specific Heat. Several equations exist for the calculation of the specific heat. All of them are empirically determined and are valid only for certain fats and oils in a specific temperature range. However, all of them are accurate enough to be used for most common technical applications. These equations have the following form:
C, = a + b x t (caVg)
v.11
In view of the small differences in a, and the minor influence of the coefficient b (Table 2.17), it is clear that such very small differentiation is not necessary to answer the usual questions in fat processing. Usually, accuracy is satisfactory when using one general value calculated for all fats and oils over the whole temperature range. For higher temperatures Bernardini (1985) gives the following data (soybean oil): 100°C C, = 0.580 ( c d g ) = 2.428 (J/g) 150°C C, = 0.589 ( c d g ) = 2.466 (J/g) 200°C C, = 0.626 (CaVg) = 2.621 (J/g) 250°C C, = 0.698 ( c d g ) = 2.922 (J/g) Temperature dependency for other oils is shown in Figure 2.16. 2.3.2.2 Heat of Fusion and Melting Dilatation. More important than the specific heat is the heat of fusion (Table 2.18). It is equal to the heat of crystallization, but inverse in sign. Its estimation is especially important to calculate the heat transfer in crystallizers and scraped surface heat exchangers (see Chapter 8). The heat has to be removed quickly in order to give defined properties to the product. Bailey (1950) prcb posed the following equation to calculate the heat of fusion for single-acid triglycerides:
AH = 3[(n- 2)a + b]
v.21
For triglycerides with different fatty acids, the following then must be valid:
H = 3b + (nr+ nrr+ nlrl - 6)a
~.31
TABLE 2.1 7 Coefficients for Specific Heat Calculation (Equation [2.1]) Appl icabiIity Trielvcerides
Oils Tallow, palm oil, partially hardened oils Fats, iodine value < l o Source: Bakes (1975).
- t ("C) 15
-t
Coefficient (OF)
60
a
b
0.462 0.475 0.458
0.00060 0.00055 0.00070
ao
Fats and Oils Handbook
[J/sl
Specific heat [cal/g]
1
Soybean oil hardened (1.V.=6.&*'*Lintrd/
\
-2.28
Soybean oil
-2.08
1.88 0
80
(32°F
(1 760F)
160
240
(32WF)
(464OF)
Temperature
["C]
Fig. 2.16. Specific heat of oils and fats depending on temperature (after Clark 1946).
where n, is the number of CH2-groups of the fatty acid in position x, a is equal to AH per CH2-group and b is equal to AH of the end CH3-group. The values for a and b in triglycerides are as follows: for the a- and p-forms, a = 0.81 and 1.06, respectively, and p = -1.28 and 4.70, respectively. More detailed tables with the heat of fusion for different triglycerides in all modifications as well as fatty acids, mono- and diglycerides have been compiled Density [g/ml] 0.95
Corn 011, soybean oil, cottonseed oil
Stearic acid
0.80
.% '
a,;-.'
..L.'
-.. . *'.
+extrapolated
0 (32°F)
5q122)
I 0 0 (212) Temperature ("C]
150(302)
200 (392'F)
Fig. 2.17. Specific density of oils and fats (after Noureddini et al. 1995).
Composition, Structure, Physical Data, and Chemistry
81
Volume
I
Fig. 2.18. Dilatation of a "steep" and a "flat" fat.
<---- Temperature c----
by Bailey (1950). During crystallization, energy equivalent to the heat of fusion is set free as heat of crystallization. There is also the heat of transformation from one crystal modification to another. Fats expand during melting. The melting dilatation is -0.15 mL/g. This dilatation is observed not only during melting but also during transformation between crystal modifications (Table 2.19; see also Fig. 2.19). 2.3.2.3 Specific Density and Thermal Expansion. To speed up processes, for ease of automation and to allow continuous processing, gravimetric dosing is being replaced more and more by volumetric dosing. The quantity to be measured, i.e., weight, which is independent of temperature is thereby substituted by the temperaturedependent quantity, i.e., volume. Usually, it is not possible for the oil to flow through TABLE 2.1 8 Heat of Fusion of Saturated Single-Acid Triglyceridesa ~~
.,
Heat of fusion (cal/gl Fatty acid A in GA3 Trig1yceride Tricaprin Trilaurin Trimyristin Tripalmitin Tr istearin
Molecular weight
measured
calculated
C-
(MI
a
P
a
P
1O:O 12:O 14:O 16;O 18:O
554.8 639.0 723.1 807.3 891.5
-
38.9 46.2 50.3 53.1 54.6
27.88 31.77 34.82 37.11 39.02
42.09 46.49 49.88 52.55 54.73
aSource: Charbonnet and Singleton (1947).
34.6 37.4 38.9
Fats and Oils Handbook
82
TABLE 2.1 9 Melting Dilatation of Saturated Triglycerides Melting dilatation of (mV@
C-
Fattv acid A
12:o 14:O 16:O 18:O p 18:O a
Lauric Myristic Palmitic Stearic Stearic
GA2
A
0.144 0.152 0.162 0.1 67 0.1 92
0.1 43 0.1 81 0.186
Source: Henkel and Cie 1971.
the volume meter at always the same temperature without a large amount of expenditure. Modem microelectronics, however, allow the mechanically measured volume data to be processed electronically thus compensating for temperature effects by correction factors. For that pupose the microcomputer is given an oil- or blend-dependent reference table for the relationship between temperature and density. The knowledge of the specific density is, therefore, now more important than before, particularly because even large tables can now easily be stored and handled by modem process computers. Swem (1982) gives the following equation for density: d,, = 0.8475 + 0.0003* SV+ 0.00014 * N
~2.41
where SV is the saponification value and N is the iodine value. More important than the saponification value is the iodine value. Normally, saponification values for oils and fats are quite similar (190 c SV c 210) which Dilatation [mm3 /25g] ’ 005 * 2
Cocoa butter
llllp6 butter
*
Shea butter Beef tallow
Lard Palm oil (Congo)
50 (1 22°F)
45
40
35
30
25
Temperature [“C]
20
15 (SQF)
Fig. 2.19. Dilatation of some fats and oils (after Jurriens 1968).
TABLE 2.20 Specific Density of Common Oils and Fatsa I (at 1S0U59'F)
II (at 4OoU104"F)
Animal oils and fats Butterfat Lard Tallow Mutton tallow Goose fat Bone oil (cattle) Neat's foot oil
0.935-0.943 0.914-0.922 0.9364.952 0.936-0.960 -
0.890-0.893 0.91 3-0.91 8
Fish oils Herring oil Sardine oil !5perm oil Whale oil Cod liver oil Fish oil
0.91 7-0.930 0.92 74.932 0.875-0.890 0.914-0.931 0.921-0.927 -
Triglyceride
111 111 (at 8OoU176"F)
0.89W.904 0.89M.904 0.896-0.904 0.902-0.906 -
-
-
I (at 1SoU59"F)
Vegetableseedo;is Soybean oil Cottonseed oil Sunflower oil Rapeseed oil Linseed oil Mustard seed oil Coconut oil Palm kernel oil Babassu oil
Palm oil Olive oil Avocado oi I Nonedible oils Castor oil
0.900-0.922 Triglyceride
0.922-0.934 0.91 7-0.931 0.92M.927 0.9104.91 7 0.9304.935 0.912-0.921 0.919-0.937 0.925-0.935 0.925 0.921-0.947 0.914-0.919 -
0.95M.974 0.9364.945 111 111 (at 15OU59"F) ~
Tricaprin Trilaurin Trimyristin Tripalmitin Tristearin
8.913 8.801 8.722 8.663 8.632
-
Trioleic Trilinoleic Trilinolenic
aSources: (I) Festschrift Thod, (11) Codex Alimentarius and (111) Kalu and Hamilton (1992).
9.1 62 0.9303 0.9454
II at
(at 20°U680F)
(at 4OoU104"F)
0.919-0.925 0.91 80.926 0.91 7-0.923 0.91 4-0.91 7 0.91 40.922 0.908-0.921 0.899-0.914 0.91 80.922 0.895-0.903 0.91 0-0.91 6 0.91 0-0.91 6
Fats and Oils Handbook
84
results in an effect on the density on the order of tenths of a percent. For a medium saponification value of SV = 200, Equation [2.4] becomes d,, = 0.9075 + 0.00014. V
12.51
In contrast, a change in IV of 60 results in a change in density of 1% and, using volumetric metering, in a mass difference of 1%. This would be the case, for example, when changing from coconut or palm kernel oil to olive or peanut oil. A change to sunflower oil would even result in a deviation of 2%. Formo (1979) showed the density of cottonseed oil (IV = 110) over a greater temperature range (see also Fig. 2.17). According to his findings, the usual equations require the following corrections for oils rich in CI6and C18fatty acids: linseed oil (IV = 190), correction 4.013; soybean oil (IV = 130), correction +0.004;hardened lard and vegetable oil (IV)= 70, correction -0.006; fully hardened oil (IV = lo), correction 4.010. These corrections are valid only for the area of fully liquid oil (melted fats). Assuming the common saponification value for cottonseed oil (SV = 190-200) Formo's data and corrections correlate well with the equation given by Swern. Table 2.20 shows densities customary in the trade, compiled from two sources. A decrease in density is a consequence of thermal expansion. Hannewijk et al. (1964) classified oils and fats and gave the following equations for the expansion E for three classes: General fats and oils Hard fats, palm oil, butterfat Coconut and palm kernel oil Oils
E=K+sx~ E = 20.4 + 0.020~ E = 20.6 + 0.019t E = 19.8 + 0.015t
where E is the medium expansion (mmV25 g), t is the temperature ("C), K is a constant (dependent on oil and respectively fat) and s is the slope of the oil-specific straight line E against t. These equations have been worked out theoretically by applying statistical methods to the data found by Bailey and Singleton (1945) for single-acid triglycerides as model substances. For practical use, it has been proposed to combine Equations [2.7] and [2.8] to yield the following for fats:
E = 20.5 + 0.020t
[2.10]
The slight deviations caused are not significant in practical use. The expansion that follows the above equation can be combined with data for the density to calculate a percentage expansion that gives a much better impression of the order of magnitude of this effect. To obtain exact values, the density of the specific oil must be used. However, to obtain a reliable overview, it makes sense to calculate using a simplified set of data. The density of vegetable oils is -0.920 (2OoC),which leads to the following:
Composition, Structure, Physical Data, and Chemistry
1 g of vegetable oil = 1.087 cm3
85
[2.11]
Taking into account the theoretical expansion from Equation [2.9], the conclusion is as follows:
E = 19.8 + 0.015 x 20 = 20.1
20.1[mm3/(25 g . t)]= 0.000804 [cmV(g . t)]
[2.12]
From this follows the percentage expansion E% per "C for a temperature of 20°C:
E% = 0.000804 x 100/1.087= 0.074
[2.13]
Under these simplifying assumptions, one can say that vegetable oils expand 0.074% per "C at 20°C. Following the same approach, a value of 0.077% per "C is obtained for fats. Baltes (1975) gives 0.00070 (= 0.07%) for coconut oil, 0.00071 for palm kernel oil, and 0.00068 for all other oils as the coefficient of expansion. For small temperature intervals Ar, E can be multiplied by Ar to yield the overall expansion over that temperature interval. Equation [2.6] then becomes
Etota,= At(K + sr)
[2.14]
where EtOd is the expansion over the temperature interval At. Over large intervals, this calculation leads to an error of -lo%, assuming heating from 100 to 200°C. To avoid this error, one must integrate over the temperature interval (b = beginning, e = end).
By integration Equation [2.6] becomes [2.15] After integration,
Etotal = K(r, - fb)
+ s/2(t,2 - rb2)
[2.16]
and, after breaking up (t,2 - tb2),
Equation [2.17] expresses, in a deducted form, something which is logical in a linear relationship such as expansion vs. temperature, namely, that the corrected value over a temperature range tb and re iS equal to the value calculated with the mean value t, of tb and re. Written differently, Equations [2.14] and [2.17] can be
86
Fats and Oils Handbook
compared as follows:
Etotal= Ar(K + sr)
[2.14]
where tMis the arithmetic mean of temperatures tb and te. The above expansion is valid only for oils and totally melted fats. Such equations can also be defined for the temperature ranges in which triglycerides are completely solidified. The resulting straight line (for fats), however, is not a continuation of the line for the liquid state (oils). Both lines are separated by the area of melting dilatation, i.e., the area that is bordered by the melting of the very first parts of the fat and the melting of the very last bit. The two straight lines for liquid state and solid state do not have to be parallel (Fig. 2.18). While the dilatation curve of a more or less single-acid fat is steep those of plastic fats are flat, because of the overlap of melting dilatation of many different triglyceride components. Apart from using melting dilatation for analytical purposes, it also gives information about the characteristics of a fat: the steeper the curve, the narrower the melting range. With a narrow melting range, the heat of melting has to be delivered altogether almost at “one point” of temperature; thus, a cooling effect in the mouth results when the fat is consumed. A good example for steep fats are cocoa butter, illip6 butter, and coconut fat (Fig. 2.19). 2.3.2.4 Vapor Pressure and Heat of Evaporation. To provide the necessary
conditions for deodorization or physical refining of oils and fats, a knowledge of the vapor pressure of the components to be removed is necessary (e.g., fatty acids, aldehydes or ketones). The vapor pressures of fatty acids, single-acid triglycerides and of two oils, shown in Figs. 2.20 and 2.21, differ mainly in that the comparable vapor pressure of the fatty acids is roughly a hundred times higher. In a double logarithmic diagram, vapor pressure vs. temperature would yield a straight line. In addition to the main components of oils and fats, there is special interest in the minor components that negatively influence taste, smell, and keepability. These are usually ketones and aldehydes whose vapor pressure is significantly higher than that of triglycerides and fatty acids (Figs. 2.22 and 2.23). Chemical antioxidants have vapor pressures on the order of magnitude of ketones and aldehydes. In a logarithmic graph, their vapor pressure forms a straight line from almost 0 at 0°C to lo00 mm Hg at 249°C (butylated hydroxyanisole BHA), 262°C (butylated hydroxytoluene BHT), and 280°C (tert-butyl hydroquinone TBHQ). The vapor pressure of natural antioxidants is much lower, e.g., for tocoperols, it is -50 times lower. Eckey (1954) gives the heat of evaporation for single-acid triglycerides (Table 2.21). As a comparison, the heat of evaporation for water is 2.26 kg/g (539 caVg), i.e., approximately ten times as high compared with fats.
87
Composition, Structure, Physical Data, and Chemistry
Vapor pressure [Pa]
10
1
01
00 1 50
90
130
170
210
250
290
330
(122’F)
(194)
(266)
(338)
(410)
(482)
(554)
(626°F)
Temperature [“C]
Fig. 2.20. Vapor pressure of the fatty acids C6 to CI8 (after Monick eta/., 1946).
2.3.2.5 Viscosity. Viscosity of oils, as with most substances, is inversely proportional to temperature. It is also inversely proportional to the number of double bonds of the esterified fatty acids. However, the first double bond decreases viscosity much more than any subsequent one (Fig. 2.24). In logarithmic graphs, the relationship between temperature and viscosity is repre sented by a straight line. This relationship is shown by an equation that has been Trimyristin Tri palmiti n
Vapor pressure [Pa]
10 1
0.1 0.01
Pressures
0.001
are
0.0001 I 140 160 180 200 220 240 260 280 300 320 (284°F)
(446)
(356)
Temperature ~ C I
(536)
(BOBOF)
Fig. 2.21. Vapor pressure of triglycerides and edible oils (after Perry et a/., 1949 and Stage 1977).
aa
Fats and Oils Handbook
Vapor pressure [Pa]
D
A
C
e
0
80
40
(32°F)
120
200
160
240
(392)
(284)
(176)
280 (536'0
Temperature r C ]
Fig. 2.22. Vapor pressure of some components associated with edible fats and oils (after Stage 1979).
deduced empirically by Gouw et al. (1966); as a comparison, viscosity of water at 20.2'C, 68.4'F is 0.1 cP. log (1.2 + log E) = K 0.95 log (1
+ r/l35)
[2.19]
where K is a constant, t is the temperature ('C), and E is the dynamic viscosity (cP). Vapor pressure [Pa]
E
B F
0 B Nonadecenel C Oleatetracosane
E
.
.
' . '
. .'.
Lauricacld
G Palmitic acid
................. . . . . . . . . . . . . .
. . . . . . . . . . .
0 (W°F)
50
100 (212)
150
200
(347)
250
(-1
300
350 (882°F)
Temperature ['C]
Fig. 2.23.
Vapor pressure of some components associated with edible fats and oils (after Stage 1979).
89
Composition, Structure, Physical Data, and Chemistry
TABLE 2.21 Heat of Evaporation of Triglycerides at Their Boiling Point at 0.0014.050 hPad Heat of evaporation
Boiling point ("Cat)
Boiling point ("F at)
Triglyceride
(cal/g)
U/&)
0.05 hPa
0.001 hPa
0.05 hPa
0.001 hPa
Tricapron Tricaprylin Tricaprin Trilaurin Trirnyristin Tripalmitin Tristearin Sovbean oil
58.6 59.1 53.7 48.8 50.9 47.6 44.9 50.5
245.3 247.4 224.8 213.1 204.3 199.3 188.0 209.3
135 179 213 244 275 298 313 308
85 128 159 188 216 239 253
2 75 355 41 5 471 52 7 568 595 586
185 262 31 8 3 70 42 1 462 487
aSources: Perry eta/. (1949), Eckey (1954), Henkel and Cie (1971), and Kalu and Hamilton (1992).
The viscosities of the different seed oils depend on their triglyceride composition; oils with high trioleate content (for example, olive oil or LEAR rape oil) are significantly more viscous compared with oils such as soybean oil (Fig. 2.25 and Table 2.22). 2.3.2.6 Solubility of Oils and Fats and in Oils and Fats. Solubility of oils and fats in solvent plays a role for three processes described later, namely, oil extraction (see Chapter 5.2.3), extraction of oil from spent bleaching earth (see Chapter 7.3.6) and wet fractionation (see Chapter 6.2.2.3). For the separation sharpness of olein and stearin in dry fractionation, the solubility of fats in oils is of some importance. Oils and fats are practically insoluble in water (hydrophobic) and dissolve better in nonpolar than in polar solvents. This is not true for fatty acids, which are also highly soluble in polar solvents, a property that offers the opportunity to wash them out of fats and oils. Only acetic acid and butyric acid are miscible with water in any proportion. From lauric acid onward, fatty acids are insoluble in water. As can be expected, water solubility decreases with increasing (hydrophobic) chain length of the acid.
2.3.2.6.7 Solubility of oils and fats in solvents. The solubility in different solvents covers a broad spectrum. Of course, solubility also increases with temperature. It also decreases with the increasing chain length of the fatty acids. Solubility of lauric acid and myristic acid at 10'C in toluene is A00 and 100 times higher, respectively, than that of stearic acid, for example (Fig. 2.26 and Fig. 2.27). The same tendency noted in fatty acids is also found in triglycerides, Le., the higher the chain length, the lower the solubility (Figs. 2.28 and 2.29). The solubility of fats in oils where oil is the solvent is a very complex process. Therefore, concepts can be developed only from model systems that have ideal
Fats and Oils Handbook
90
Viscosity [cP]
12 Fatty acids
0
t
Z
I
t
!
c18:o
'
l
I
t
1
1
/
I
1
I
I
I
!
I
/
/
10 20 30 40 50 60 70 80 90 100110120 (50'F)
(149)
(104)
(1 94)
(248OF)
Temperature ["C] Viscosity [cP]
25
j Triglyceride : X
Tristearin Tripalmitin
40 45 50 55 60 65 70 75 80 (1M'F)
(131)
(1 58)
*
Trimyristin
A
Trilaurin Tricaprin
85 (1fi'F)
Temperature ["C]
Fig. 2.24. Viscosity of single acid saturated triglycerides (after Joglekar and Watson 1928 and 1930).
composition and allow simplified assumptions. The most substantial of these assumptions is that fat in oil forms an ideal solution, so that no mixed crystals are formed. For such solutions, melting points have to differ by at least 2 0 T , i.e., m.p.oleinc m.p.stearin - 20 = ideal solution. Hannewijk er al. (1964) has investigated the solubility of stearines in oleines (Fig. 2.30). For calculations Clausius Clapeyron's equation is applicable, assuming constant pressure in a monovariant system. The solubility of the high melting compound (stearin) can then be described as:
Composition, Structure, Physical Data, and Chemistry
viscosity
91
[CP]
120
100
Sunflower oil,
80
p.m.: Castor oil 950 (20%) 125 (50%)
------
60 40
20 .O
20 30 40 50 60 70 80 90 100110 (68°F)
(122)
(104)
(194)
(230°F)
Temperature ["C]
Fig. 2.25. Viscosity of oils and fats dependent on temperature. d In m -=-
Qs
dT
R.TM2
[2.20]
[2.20aI
where m is the molar share of stearin in the mixture (gmol,,ea,in/gmolmixtu,),Ts is the melting point of stearin ("C), TM is the melting point of the mixture ("C), R is the universal gas constant, and Qs is the molar heat of melting of high melting component, i.e. the stearin. Assuminn a constant
(3 heinp
0J2.3 . R. eouation 2 20a hacnmec
log m=-C.-
TS TS
'
[2.21]
TM
Assuming concentrated solutions of the high melting component S and a melting point TM that does not differ greatly from that of S,by approximation T, may be regarded equal to Tsin the denominator. Equation 2.21 then becomes log m = K(T- T,) in which
K=-=C Qs Ts2 2.3. R . Ts2
[2.22]
Fats and Oils Handbook
92
TABLE 2.22 Viscosity
of Fats and Some Fatty Acids at Different Temperatures
Viscosity (cP) at "C ( O F ) Oils 20°C (68°F) Rape oil (HEAR) Palm oil Cottonseed oil Peanut oil Sunflower oil Soybean oil Linseed oil Palm kernel oil Coconut oil Castor oil Olive kernel oil Triglycerides Tricaprin Trilaurin Trimyristin Tripalmitin Tristearin
Fatty acids Palmitic acid Stearic acid Oleic acid Erucic acid
90.9 50 82.6 77 63.7 60.7 47.7
-
950 77 60°C (140°F) 7.77 13.59 17.71
-
38°C (100°F)
50°C (112°F) 28 24 25.3 24 21.5 20.5 17.5 17.4-1 8 16.8-1 7.3 123 24
Reference
98.9"C (210°F) 10.3
-
8.4
7.7 7.6 7.3 6.5 6.1 20.1 9.1
-
7 5 T (167°F)
85°C (185°F)
-
7OoC (1 58°F)
14.6 17.6 20.5 23.4 48.9"C (120°F)
I,IV I I,IV 111 I,IV I,IV I,IV II,IV IIJV II,IV III,IV
-
-
VI,VII VI,VII VI,VII VI,VII VI,VII
6.25 9.1 1 11.70 14.67 18.50
5.51 7.22 9.20 1 1.44 14.31
75°C (167OF)
98.9"C (210°F)
-
-
7.10 9.04
17.70 32.30
13.20 22.40
-
V V V V
4.13 5.08 4.03 6.1 8
aSources: (I)Boekenoogen (1935), (11) Formo (1979), (111) Eckey (1954), (IV) Rescoria and Carnahan (1936), Noureddini era/. (1992), (VI) Kalu and Hamilton (1992), and Joglekar and Watson (1928).
M
For such concentrated solutions a linear relationship may be assumed not only between log m and Vr,but also between log m and Tw As said above, the foregoing is only valid for monovariant systems (no mixed crystals former). However, this equation describes reality quite well (Fig. 2.30). 2.3.2.6.2 Solubility of gases in oils and fats. Solubility of gases plays a role during fats and oils processing. Absorption of oxygen is the basis for later oxidation, and the solubility of hydrogen is important for hardening. Oils are sometimes protected by saturating them with nitrogen, which is also used to whip up some end-products. Formo (1979) gives some linear equations for the solubility of gases [volume dissolved at 760 mm Hg pressure in a volume of oil; tc ("C); tF as follows: (OF)]
(i) S(H,) = 0.0295 + 0.000497 . tc (ii) s ( N 2 ) = 0.0590 + 0.000400 ' tc (iii) s ( 0 2 ) = 0.1157 + 0.000443 ' ?c (iV) S(c0)= 0.0890 + 0.000400 ' fc
-
S(H,) = 0.04544 + 0.000895 tF s(N2) = 0.07180 + 0.000720 ' t F s(0,) = 0.12988 + 0.000797 ' fF S(c0)= 0.10180 + 0.000720' fF
[2.23]
93
Composition, Structure, Physical Data, and Chemistry
Solubility In benzene [% w/w]
10,000 : j i Fatty Acid Caprylic
1,000 i j i ~
Caprlnic
100
+
Lauric
A
Myristic
;:: ...
10
Palmitic
: : I
. . ..
... ...
Stearic
1 i. . :. . . ..
... ...
#
0
10
20
30
40
(92'F)
(SO)
(68)
(86)
(104)
50
(122)
60
70
(140) (lSBeFj
Temperature ["C]
Fig. 2.26. Solubility of different fatty acids in benzene (after Bailey 1950).
The solubility of oxygen is one third to two thirds lower in refined than in crude oils (Ah0and Wahlroos 1967); it increases with free fatty acids (FFA), doubling at about 30%FFA. 2.3.2.6.3 Solubility of water in fats and oils and vice versa. The solubility of water in oils is very low. This small amount is normally of no importance in all technical operations, because water either does not disturb the operation or it can easily be removed. Obviously, that is why almost no data can be found in literature Solubility of stearic acid I96 wt/wtl 10,000
Solvent: 'Toluene I
1
1
1,000
+
'""i
+
*
1
(SOY
Cyclohexane
* Benzene
10
0.1 V 10
* 1 ,CDioxane
Acetonitrile Nltromethane
I 20 (88)
30
40
(6'3)
(104)
50
(122)
6q
(140 Fl
Temperature ['C]
Fig. 2.27. Solubility of stearic acid in different solvents (after Bailey 1950).
Fats and Oils Handbook
94
Solubility in benzene [% w/w]
100 Triglyceride Tricaprin +
Trilaurin
* Trimyristin 9
Tripalmitin
10
Tristearin
,
,
0
10
20
30
40
50
60
70
(32'F)
(50)
(68)
(88)
(104)
(132)
(140)
(158'F)
d
Temperature ["C]
Fig. 2.28. Solubility of single acid triglycerides in benzene (after Bailey 1950).
about solubility of water in oil. For winterized cottonseed oil, Parsons and Holmberg (1937) found 0.075% solubility at 0°C and 0.13% at 32.5"Cwith a linear relation between these points. Outside of this range, solubility rises more quickly. As a trend, it is higher in oils with shorter fatty acid chain lengths (e.g., coconut oil) and increases dramaticdly in oils with hydroxyl groups such as castor bean oil.
Solubility of tristearin [% w/w] Solvent +
Chloroformium
* Benzene * Carbondisulfide
* Ethylether +
0.1
,
0.01 0
(32'F)
10
(50)
Ethanol
I
20
(68)
30
(86)
40
(104)
50
(122)
60
79
(140) (158 F)
Temperature ["C]
Fig. 2.29. Solubility of tristearine in different solvents (after Bailey 1950).
Composition, Structure, Physical Data, and Chemistry
95
Solubility [Mol%] 100
+A
PPO in trilinolein
+B
POP in trilinolein
+C SOS in trilinolein +D
hard. peanut oil / LO
+E hard. peanut oil I LO 10
*F
PPP in triolein
+G SSS in triolein +H SSS in trilinolein
1 15
(59’6
25
(77)
35
(95)
45
(113)
Temperature
55
(131)
65
(149
F)
P = Palrnitic acid S = Stearic acid 0 Oleic acid LO= Linoleic acid
[“C]
Fig. 2.30. Solubility of stearins in oleins (after Hannewijk eta/. 1964).
2.3.2.7 Smoke Point, Flash Point, and Fire Point. The knowledge of these data is of limited interest for oil and fat processing because great care is taken to ensure absence of oxygen when working at higher temperatures. The data are of more importance for those working with oil and fat products, e.g., deep frying. The values given differ slightly among the specific oils because their triglyceride composition varies, as expected in a natural product. It is primarily the FFA content that influences all three points substantially, as shown by Bailey (1951) and Morgan (1942); see Fig. 2.31. The fatty acid composition of the oils and fats plays a minor role and is of influence only when shifting towards medium and short chain lengths. Coconut oil, for example has a significantly lower smoke point. The degree of unsaturation does not appear to play an important role (Table 2.23). The term “smoke point” is misleading because there is no smoke, but there are condensed vapors (clouds) of fatty acids and other lipids. At the fire point, the oil is “actively” burning, whereas at the flash point, decomposition products can be inflamed merely when coming in contact with a flame. For shortenings, the following equation for the relationship between FFA content and smoke point has been developed by Zabik (1962):
FFA = 0.0445 - 0.00174 Ts 2 0.018
[2.24]
where FFA is the percentage of free fatty acids and Ts is the smoke point (“(2). The temperatures given should not disguise the fact that, for igniting an oil, how finely it is dispersed, i.e., its surface area, is also very important. If it is very
Fats and Oils Handbook
96
Free fatty acids
[%I
3.01
’09
$$!
(SW 150
(212 F)
$G
$9:
0
Temperature [‘C]
Fig. 2.31. Smoke, flash, and fire point are dependent on their fatty acid content (after Bailey 1951 and Morgan 1942).
finely dispersed, it can ignite or detonate at much lower temperatures when corning into contact with oxygen. This is important when filters in which the oil is finely dispersed on an adsorbent (such as bleaching earth) are opened when still hot. 2.3.2.8 Refractive Index. The refractive index gives the ratio between the angle of incident light and the refracted beam when passing through a medium. Oils and fats may be characterized by the refractive index, and the progress of a chemical TABLE 2.23 Smoke Point, Flash Point, and Fire Point of Fully Refined Oil9 ~
Oil Rapeseed oil Peanut oil - peanut oil - hardened 32/34 Cottonseed oil - cottonseed oil Soybean oil - soybean oil - hardened 42/44 Sunflower oil Coconut oil Palm oil
0.08 0.09 0.1 1 0.04 0.04 0.1 8 0.04
-
0.04
0.10 0.20
0.06
218 207 198 226 223 185 213 242 223 209 194 223
424 405 388 439 433 365 415 468 433 408 381 433
317 315 333 314 322 318 317 330 318 316 288 314
603 599 631 597 612 604 603 626 604 601 550 597
%urces: Rirnpl (1963), Morgan (1942), W i l e r and Markley (1940), and Pardun (1969).
344 342 363 340 342 357 342 360 342 341 329 341
65 1 648 685 644 648 675 648 680 648 646 624 646
-
Composition, Structure, Physical Data, and Chemistry
97
reaction may be monitored by measuring it. Lund (1922) found an equation that allows calculation of the refractive index of oils and melted fats from the saponification value and the iodine value: t ~ D= t X,
- O.oooO8 * SV + O.ooOo107 . IV
[2.25]
where SV is the saponification value, IV is the iodine value, t is the temperature ("C), x, = 1.4686 for t = 40°C and xt = 1.4650 for t = 50°C. According to Pardun (1976), the equation works satisfactorily only when fresh fats of natural'origin are used (i,e., not oxidized or hardened). In analogy to Chapter 2.3.2.3, Equation [2.25] can be simplified to estimate the order of magnitude more easily. Assuming an average saponification value of 200, it becomes the following:
ID' = X , - 0.016 + O.ooOo107 IV
[2.26]
*
or, for the usual measuring temperature of 40"C, [2.27] Tables 2.24 and 2.25 show refractive indices for single acid triglycerides and for common oils and fats. By plotting the refractive.index mean values of the oils and fats (from Table 2.25) against the mean iodine values from the fact files (Chapters 3 and 4), a regression line can be calculated. The boxes symbolize the ranges of iodine values and the refractive index at 40'C (Fig. 2.32). With a correlation coefficient of 0.989, their relationship is represented by the following equation: nD4'
= 1.44764 + 0.0001528 ' Iv
[2.28]
TABLE 2.24 Refractive Indices of Single-Acid Triglycerides GA,a nDX Fatty acid A
A= c6:0 C8:O
Cl0:O Cl2:O c14:0 cl6:O C18:O
C18:l
Cl8:2 c183
n~~Triglyceride CA3
20°C (68°F)
6OoC (140°F)
20°C (68OF)
70°C (1 58°F)
1.4441 1.4480
-
-
-
-
1.4370 1.4402 1.4428
-
1.4169 1.4230 1.4273 1.4309 1.4337
1.4582 1.4699 1.4800
-
-
-
1.4471 1.4548 1.4645 1.4741
-
aSources: Wheeler eta/. (1 9401, Joglekarand Watson (1 928), and Henkel and Cie (1 971).
Fats and Oils Handbook
98
TABLE 2.25 Refractive Indices of Fats and Oil9 Fatloil
nD40
Milkfat Lard Tallow Mutton tallow Pott whale oil
at 4OoC (1 04°F)
1.452-1.457 1.448-1.460 i ,448-1.460 1.448-1.460 1.467-1.475 1.465-1.467 i . 4 5 a i ,466 1.466-1.470 1.472-1.475 1.467-1.469 1.460-1.465 1.465-1.469 1.467-1.470 1.465-1.468
Fish oil Rapeseed oil (LEAR) Cottonseed oil Soybean oil Linseed oil Sunflower oil Peanut oil Sesame oil Safflower oil Corn oil Grape seed oil Walnut oil Niger seed oil Wheat germ oil Rice bran oil Poppy seed oil Mustard seed oil Palm oil Olive oil Avocado oi I Coconut oil Palm kernel oil Cocoa butter Babassu oil Shea butter lllip6 butter Mowrah butter Borneo tallow
-
-
1.449-1.455 1.4677-1.4705 1.448-1.450 1.448-1.452 1.456-1.458 1.448-1.451 1.465-1.466 1.459-1.462 1.458-1.461
-
1.457-1.461
-
1.455-1.458 1.456-1.458 1.470-1.478 1.464-1.466 1.466-1.468 1.465-1.469 1.472-1.475 1.466-1.468 1.461-1.465 1.465-1.468 1.467-1.469 1.465-1.466 1.461-1.471 1.469-1.475 1.467-1.469 1 . m - 1 ,478 1.466-1.469 1.467-1.470 1,463-1.466 1.453-1.456 1.461-1.462 1.461-1.465 1.448-1.450 1.449-1.450 1.456-1.458 1.449-1.451 1.463-1.466 1.459-1.462 1.458-1.461 1.456-1.457
~~
aSources: Left column, Codex Alirnentarius; right column, Wissebach (1969)
2.4 Chemical Reactions
Except for hardening, no purely chemical reactions are conducted in oils and fats processing. However, unwanted nontriglyceride components may be separated by chemical means without affecting the remaining triglycerides. An example are FFA that are saponified by alkali and separated via the aqueous phase. Together with the intentional reactions during processing, a natural product undergoes a broad range of reactions that are triggered or promoted by its natural environment or induced during processing. These reactions are described in the following sections.
99
Composition, Structure, Physical Data, and Chemistry
Iodine value
2ool 200
150
150
loo(. 100
50 0 1.44%
1.453
1.458
1.463
1.468
1.473
1.47%
Refractive index
Fig. 2.32. Relationship between refraction index and iodine value of fats and oils.
2.4.1 lsomerization
2.4.7.1Geometrical Isomerization. Natural vegetable oils and fats contain unsaturated acids almost exclusively in the cis form. At high temperature (around 150"C), with surface active components (such as Kieselgur and bleaching earth) present, and during hardening, these double bonds can be isomerized into the trans form. As mentioned previously, vegetable oils and fats are almost trans free (below detection limit in seeds). Trans fatty acids occur in most animal fats, e.g., in butterfat at a level of 2 . 5 4 5 %(varying between summer- and winter-butter) (Patton et al. 1960). Kaufmann and Mankel (1964) found considerable amounts of trans fatty acids in beef tallow (4.6-lo%),goat (6.8-11.1%)and mutton (10.7-15.8%). 2.4.7.2 Positional Isomerization. As well as geometrical isomerization, positional isomerization can also take place, which means a shift of isolated double bonds toward a structure containing more conjugated double bonds. This isomerization can occur at very high temperatures during alkali treatment. Such conditions do not occur during correct processing of oils and fats for edible purposes.
2.4.2 Polymerization
If fats and oils are heated above 250'C and kept at that temperature, the probability of fatty acid dimerization (intermolecular) or cyclization (intramolecular) increas-
Fats and Oils Handbook
100
es. Because only thermal dimerization can be observed under normal conditions of oils and fats processing, the term polymerization, frequently used for this phenomenon, is misleading. Only in refining are the temperatures applied at levels high enough to reach that range. Therefore, they have to be monitored carefully (see Chapters 7.4 and 7.5). Because the reaction is time dependent, residence time has to be kept as short as possible. Great efforts in recent years have succeeded in drastically reducing dimerization to such an extent that it can almost be avoided in well-run refineries. If oil is kept for an extended period in an open atmosphere at high temperature (e.g., deep frying), oxidative polymerization can occur, as indicated by a deeper color and increased viscosity. In oxidative polymerization, fatty acid molecules are intramolecularly or intermolecularly bound via an oxygen bridge. Splitting off oxygen can lead to cyclization, dimerization and polymerization. Polymerization is technologically used only for oils that are not intended for edible purposes. Tung oil, for example, is polymerized by being kept at 300°C for 12 min; a cross-linked polymer is formed. 2.4.3 Au toxidation
Autoxidation is a radical chain reaction. After an induction period, it may run very fast under certain circumstances. A chemical attack on the alkyl group is followed by a chain reaction, resulting in a hydroperoxide group (-OOH) in the chain. The chain reaction is started by peroxy-, alkoxy- and alkyl-radicals
R-OO', R-O',
R'
[2.29]
The chain reaction proceeds by reaction with oxygen or RH
R' R-00' R-0'
+
O=O
+
R-H R-H
+
+ -+ +
R-00' R-OOH+R' R-OH+R'
[2.30]
It is accelerated by branching of the chain
R-OOH 2R-OOH
-+ -+
R-0'
+
R-0' +
'OH R-OO'
+ HzO
[2.31]
The chain reaction ends by combination of two radicals
R' R' R' R-0' R-OO' R-0'
+ + +
+ +
+
R' R-0' R-OO' R-00' R-OO' R-0'
[2.32]
Composition, Structure, Physical Data, and Chemistry
101
Autoxidation is promoted by heat and light (energy) and heavy metals can catalyze the process. The energy that is needed to split an allyl-positioned H-atom decreases from 99 kcal/mol for the methylene group via 80 kcaVmol for a molecule with one allylic group to 40 kcal/mol for a molecule with three allylic groups. Highly unsaturated oils are especially susceptible to this type of reaction. The hydroperoxides formed (they themselves are almost neutral in taste) react further to aldehydes, ketones and fatty acids, all of which negatively influence taste (see also Equation [2.33]. These are removed during deodorization (see Chapter 7.4). Gunstone and Hilditch (1945) gave the relative reaction rates (R) for the oxidation of oleic acid (R = 1) c linoleic acid (R = 10) c linolenic acid (R = 25). Erickson and List (1985) calculated the inherent stability of common oils and fats, giving reaction rates that are naturally inversely propodonal to the oxidation stability, i.e., the higher the reaction rate, the lower the stability (Table 2.26). Belitz and Grosch (1982) determined the speed of oxidation for unsaturated C,, fatty acids (Table 2.27) and described the oxidation mechanisms. Natural antioxidants in vegetable oils and chelate-building additives, such as citric acids that can bind trace metals, help to avoid oxidation. To prevent metal catalysis of oxidation, processing equipment for fats and oils should not be fabricated in mild steel. However, mild steel can be coated to prevent contamination of the oil by trace metals. This coating can be of synthetic resin or resin from polymerized edible oil. For the latter, the equipment is filled several times with hot oil so that a thin film of polymerized oil resin builds up on the walls as a protectant. Under certain circumstances, lipochromes, natural antioxidants such as carotinoids, can also act prooxidatively under the influence of light. It is therefore recTABLE 2.26 Relative Rates of Reactivity of Common Oils and Fats. Stability Calculated as Decimal Fraction Fatty Acids Multiplied by Relative Rate of Reaction with Oxygen of Each Fatty Acidd Oillfat Safflower oil Soybean oil Sunflower oil Corn oil Rapeseed oil (LEAR) Cottonseed oi I Peanut oil Lard Olive oil Palm oil Tallow Palm kernel oil Coconut oil 'Source: Erikson (1985).
Stability
Iodine value
7.6 7.0 6.8 6.2 5.5 5.4 3.7 1.7 1.5 1.3 0.86 0.27 0.24
149 132 136 128 120 110 100 62 82 50 44 13 8
Fats and Oils Handbook
I02
TABLE 2.27 Rate of Oxidation of Fatty Acidsa C
Fatty acid
Induction period (h)
18:O 18:l 18:2 18:3
Stearic Oleic Linoleic Linolenic
-
Relative speed of oxidation
1
82 19 1.34
100 1,200 2,500
aSource: Belie and Crosch (1982).
ommended that packaging chosen for products containing deodorized oils be impermeable to light or able to absorb those wave lengths that start the oxidation processes. 2.4.4 Hydrolytic Splitting (lipolysis)
Hydrolytic splitting becomes a problem only when microorganisms or enzymes affect fats and oils. Fats and oils are quite resistant against an attack of water alone. However, it has to be taken into account that the activity of microorganisms increases with the water content and is possible only above a certain water content. At 2 0 T , -0.1% of water is soluble in oil, and solubility increases with temperature. Enzymes may arise from the fat itself (in seed oils from the seeds, for example) or from microorganisms that settle on the fat or oil. In particular, molds such as Aspergillus niger, produce high quantities of enzymes. During the sequence of processing steps, hydrolytic attack is a problem only during oilseed storage and transport. After extraction, the risk is low unless storage conditions are poor, because enzymes are usually inactivated by then. In principle, fat can be split more easily if fatty acids are short chained. The enzyme reaction begins with triglycerides because the reaction rate decreases in the sequence triglyceride > diglyceride > monoglyceride. There are unspecific lipases and also others that specifically split certain fatty acids or stereospecifically attack certain positions of the triglyceride (see Chapter 6.4). 2.4.5 Saponification
Free fatty acids react with alkali to form soaps as follows:
R-COOH + NaOH + R-COONa + H,O
[2.34]
The sodium soaps formed are water soluble enough to be separated from the oil or fat as an aqueous solution. As a side reaction, a very small part of the triglycerides is saponified, i.e., hydrolyzed. C3HS(COOR),+ 3 NaOH + C,H,(OH),
+ 3 NaOOCR
[2.35]
composition, Structure, Physical Data, and Chemistry
103
Hydrolysis takes place in three stages; usually the last stage is not reached. For analytical purposes, fats are saponified to determine the unsaponifiable content and to analyze its components (see Chapter 9.5). 2.5 Lipids
Oils and fats contain natural admixtures of nontriglycerides that stem from the seed or pulp in vegetable oils and from the adipose tissues in animal fat. These compounds occur associated with fats and oils in the animal or plant cells and dissolve in the oil. Like the oils and fats themselves, they belong to the large group of lipids. The classification of the compounds said to belong to this group is somewhat artificial and should be viewed from a historical perspective. The usual definition for lipids is that they are insoluble in water but soluble in nonpolar solvents. The group derived its name from its predominant members, fats and oils. In the following sections, the most important groups of lipids that occur in common oils and fats or their sources are illustrated. The following compounds associated with triglycerides belong to this group: hydrocarbons, carotinoids, oil-soluble vitamins, waxes, phospho-, glyco- and sulpholipids. A detailed list of all known lipids including their formula, data and references is given by Gunstone et al. (1986). 2.5.1 Lecithins
Oilseeds contain lecithins whose role is to stabilize the oil, i.e., the energy reserve, in the seeds. During oil extraction, part of these disperse in the oil; usually they are separated and sold as special products. Lecithin was discovered in 181l, when Vauquelin reported fat-containing substances from the brain that contained phosphorous. Schneider (1992) defines lecithin as follows: (i) historical: phosphorous-containing lipid from egg and brain; (ii) scientific: phosphatidylcholine (1,2-diacyl-sn-glycero- 3phosphorylcholine); (iii) commercial and legal: mixture of polar and nonpolar lipids with a minimum of 60% acetone-insoluble substances; (plant and animal origin; European ingredient no. E 322). Schneider also offers the following characteristics: (i) appearance: highly viscous or semiliquid or powder products of brown color; (hydrolyzed, highly viscous or pasty fluids, light brown or brown color); (ii) content: not ~ 6 0 % acetone-insoluble substances; (hydrolyzed, not 4 6 % acetone-insoluble substances); (iii) volatile substances: ~ 2 % determined after 1 h drying at 105°C (221°F); (iv) toluene insoluble: ~ 0 . 3 % (v) ; acid value: <35 mg potassium hydroxide/g; (hydrolyzed, <45 mg potassium hydroxide/g); (vi) peroxide value: 10 or less (mequivkg). The term lecithin encompasses those phospholipids that are found in the oil after extraction. There are three main classes of compounds: phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinosite (PI) (Fig. 2.33). These three classes account for three fourths of all lecithins in soybean oil. Generally, soy lecithin is meant when lecithin is referred to because only soybean oil
Fats and Oils Handbook
104
II CH2 - 0 C - RI
-
Fig. 2.33. Chemical structure of the most important glycerophospholipids. contains substantial amounts (Table 2.28). The production of lecithin is described in Chapter 5.2.5.1. American soy lecithin contains -50% phosphatides, 4 . 5 % glycolipids and the same amount of carhhydrates (Weber 1981).The share of phosphatldylcholine is 4.070of the phosphatides,i.e., 20% of the total soy lecithin. The family of phospholipids houses a great variety of substances because of the very different fatty acid residues (R) and the possibility of binding to two different positions 1- (3-) or 2-. For saturated fatty acids, position 1- (3-) is preferred, for unsaturated, position 2-. Lecithins have many uses (Table 2.29), for example, as emulsifiers for margarines (see Chapter 8.2). Pardun (1988) gives a very detailed description of all aspects of lecithins in a monograph. Crude oils extracted each year contain -850,000 tons of lecithin of which -140,ooO tons are produced. TABLE 2.20 Phosphatides in Oilseeds and Seed Oila Phosphatides (YO) in seedshans
seed oil
Soybeans
1.5
Cottonseed Sunflower seed Peanuts Rapeseed Linseed Corn germs
1.ax2 1.3-2.7
0.5 0.5 1.5 0.75
0.5-1
aSowce: Pardun (1989).
-
-
.o
0.3-0.4 0.2-0.5 -1.8 1-2
Composition, Structure, Physical Data, and Chemistry
105
TABLE 2.29 Use of Lecithina YO
Margarine Baked products, chocolate, ice cream Animal feed Technical products Cosmetics Pharmaceutics
20-30 25-30 25-30 15-20 3-5 -3
aSource: Pardun (1989).
2.5.2 Hydrocarbons Aliphates and terpenoids occur naturally in fats and oils. Polycyclic hydrocarbons can also be found but come from the environment. This is especially hue for coconut oil (see Chapter 4.3.6) whose starting material, copra, is sometimes dried over an open fire. Aliphates and terpenoids are completely removed during fullrefining (seeChapter 7.7). Aliphatic hydrocarbons of natural origin have been identified up to a chain length of Cd5.Usually the chain length is odd-numbered and exists in both forms, unbranched and branched. From the terpenoid family, squalene must be mentioned, because it is contained in substantial amounts in some liver oils. It also occurs in olive oil in remarkable quantities compared with other vegetable oils; it is a marker substance to prove adulteration of olive oil. Squalene consists of six isoprene-units and contains six (all-trans) double bonds. It was discovered by Tsujimoto (1906); see Tables 2.30 and 2.31 and Fig. 2.34. TABLE 2.30 Squalene Content of Some Oilsa Oil Shark liver oil Cod-liver oil Olive oil Rice bran oil Corn oil Cottonseed oil Soybean oil Sunflower oil Sesame oil Linseed oil Peanut oil Rapeseed oil
Saualene Content (Yo) 20-88 0.33 0.090-0.708 0.33 0.0164.042 0.0034.01 5 0.002-0.022 0.008-0.019 0.003-0.01 1 0.004-0.028 0.0024.049 0.003402 8
aSources: Fitelson (1943a), Fabris and Vitagliano (1955), Hadorn (1953), Cracian eta/. (1963)and Tiufel eta/. (1940).
Fats and Oils Handbook
106
TABLE 2.31
Physical and Chemical Data of Squalene (Spinacene) 2,6,10,15,19,23-Hexamethyl-2, 6,10,14,18,22-tetracosahexaene Molecular weight Sum equation Form Iodine value Flash point Melting point ("C) (OF)
Boiling point
(OC) (OF)
Refractive index Density (2014)
WmL)
41 0.74 C30H50
Colorless oil
360-3 80
-200 --75 --lo3 280 at 17 hPa 536 at 17 hPa 1.496520 0.8584
Sources: Neumijller 1993, CRC 1976.
2.5.3 Sterols Sterols are polycyclic alcohols derived from sterane (cyclopentanoperhydrophenantrene) as a base structure. Under the name of sterane, other structures also can be found. Sterols account for the majority of the unsaponifiable fats and oils. Following their natural occurrence, one distinguishes among zoosterols from animal origin, phytosterols from plants and mycosterols from lower organisms such as fungi (Table 2.32). For the biosynthesis of sterols, see Ehrhart and Ruschig (1972). For rape oil, brassica-sterols are characteristic and are used to detect adulteration with other oilsin this case, adulteration of other oils with rape. Phytosterols are not absorbed by the human body, and lower organisms are not yet used as a source for fats and oils; to date, only zoosterols are of importance. However, phytosterols have recently gained attention as food additives in margarine. Table 2.32 gives the sterol content of some oils and fats. The most noted of these is cholesterol (Table 2.34), the first sterol that was discovered. Cholesterol's main source is in food of animal origin and especially animal fat. It is derived from sterol by adding an OH-group to C3, one methyl group each to CISand CI9,and an eight-carbon atom side chain to C,, (Fig. 2.35); physical and chemical data in Table 2.33. Vegetable oils and fats are cholesterol free, following the general agreement that all substances with a cholesterol content 4 0 ppm are regarded as cholesterol free. Cholesterol as a constituent of animal fat is important in so far as it can be linked to heart disease (see Chapter 1.4).
Fig. 2.34. Chemical structure of squalene.
Composition, Structure, Physical Data, and Chemistry
107
TABLE 2.32 Sterol Content (%) of Oils and Fat9 Butter oil Lard Tallow Mutton tallow Fish oil Cod-liver oil Halibut liver oil Herring oil (hardened) Menhaden oil (hardened) Coconut oil Palm kernel oil Cocoa butter Babassu oil Rapeseed oil (LEAR) Cottonseed oil Soybean oil Linseed oil Sunflower oil Peanut oil Sesame oil Safflower oil Corn oil Olive kernel oil
0.24-0.1 4 0.11-0.12 0.08-0.1 4 0.03-0.1 0 0.3 0.42-0.54 7.6 0.6 0.4 0.06-0.08 0.06-0.12 0.1 7-0.20 0.07-0.09 0.35-0.50 0.26-0.31 0.15-0.38 0.37-0.43 0.25-0.40 0.19-0.25 0.43-0.55 0.28-0.38 0.58-1 .OO 0.23-0.30
aSources: Copius Peereboom and Beekes (1 962), Fedeli eta/. (1 9661, ltoh eta/. (1973)and Urakam eta/. (1976).
2.5.4 Lipochromes
At present, more than 550 different carotenoids out of 100 million tons that nature produces every year have been isolated (Rodriguez-Amaya 1993). Carotenoids are derived from a base molecule consisting of a Cd0chain, which is composed from eight isoprenic units. Because of the conjugated double bonds and dependence on the class of substituents, they are colored dark yellow to red. Their absorption maxima lie between 425 and 525 nm. Carotenoids are sensitive to oxygen and light and are natural colorants for food. One distinguishes between a-, p-, and y-carotene (trivial names). a-Carotene contains one a- and one p-ionone ring; p-carotene contains two p-ionone rings; and y-carotene has one additional double bond but only one ring (Fig. 2.35). The main source for a-carotene is palm oil, in which it can account for more than 30% of all carotene contained. Carotenes function as provitamin A. Two molecules of vitamin A can be obtained by symmetrical splitting of p-carotene and the addition of water; a- and y-carotene yield only one molecule of vitamin A. Chlorophyll, another colorant, occurs mainly in those oils that are produced from beans, but also in rape, olive, and avocado oil. Apart from virgin olive oil (as
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108
TABLE 2.33 Physical and Chemical Data of Some Sterols Cholesterol
Sterol Chemical formula Molecular weight Form
Density Melting point
C27H460
(g/mL)
PC) (OF)
Boiling point
("Cat hP) ("Flat hP)
386.67 Colorless rhombic or triclinic leaves 1.052 148.5 299.3 233 at 0.5 451 at0.5
Stigmasterol
Campesterol
PSitosterol
C29H480
C28H480
412.71 Colorless crystals
400.72 Colorless crystals
C2gH500 41 4.72 Colorless plates or needles
170 338
157-1 58 3 15-31 6
137-1 40 278-284
a result of the mild refining process), the green color is usually removed by refining. Crude rapeseed oil contains 5-10 ppm chlorophyll, soybean oil up to 1.5 ppm. 2.5.5 Lipovitamins
2.5.5.1 Vitamin A. As seen previously, carotenoids (Table 2.35) can be transformed into vitamin A (Fig. 2.37). Vitamin A (retinol, Table 2.36) itself is usually found in marine liver oils. Quantities can be high (Table 2.37). Deficiency of vitamin A can lead to night blindness or even blindness, with overdosage of vitamin A causing headache and vomiting. It is usually supplied as its acetate or palmitate. A recent overview is given by Woollard (1993) and Furr (1993). TABLE 2.34 Cholesterol Content of Some Oils and Fat9 FaVoil Crude oils Peanut Corn Soybean Olive Rapeseed Sunflower Refined oils Cottonseed oil Coconut oil Palm Palm kernel Animal fat Butter fat Lard ahrce: seher and Cundlach (1982).
Cholesterol (ppm)
10.3 19 7.9 6-7.4 12.5-33.6 1.6-7.7 15.4 5.6 8-2 6 8.4-28.5 2450 980
Composition, Structure, Physical Data, and Chemistry
Cholutro(:
R - H
cnpwkol: R - CH3 Bnuicr(.rm: R - CH3b22 stbmnw: R = 42t1sb22
m:R
H
1 09
= 4 z b
Fig. 2.35. Chemical structure of sterane and cholesterol.
2.5.5.2 Vitamin D. Vitamin D belongs to the family of sterols (Fig. 2.38, Table 2.38). Butter contains 0.0003-0.0015% vitamin D. Vegetable oils and fats and animal fat do not contain vitamin D in amounts worth mentioning. Therefore, vitamin D is added to many fat products such as margarine. Vitamin D deficiency manifests itself by osteomalacy (softening of bones due to insufficient incorporation of minerals), which can lead to deformations if it occurs at a young age. Overdosage leads to vomiting, diarrhea, and in severe cases, kidney damage. An overview on vitamin D is given by Woollard (1993) with the physiologic aspects covered by Maiyar and Norman (1993). 2.5.5.3 Vitamin E (Tocopherol). Tocopherols were first isolated in 1936 by Evans et al. Their structure was described in 1938 by Femholz. To class@ them systemati-
cally, Karrer (1938) introduced the name tocol for the base molecule, 2-methyl-2From this base, all seven known (4',8', 12-trimethyltridecyl)-6-hydroxychromane. tocopherols can be derived. They are built by supplementing positions 5,7 and 8 with one to three methyl groups (Fig. 2.39). The only important ones, however, are the a-, 7- and 6-tocopherols. Tocopherols are used as antioxidants because they trap TABLE 2.35 Physical and Chemical Data of Carotenes
a
Carotene
B
Y
Provitamin A Chemical formula Molecular weight Form Density Melting point
C40H56
C40H56
536.90 Deep purple plates or prisms
536.90 Deep purple hexagonal prisms
(g/mL)
1 .oo
1 .oo
("0
187.5 3 69
183 3 63
("F)
Sources: Roche 1970, CRC 1976, Ceigy 1968, Neurnuller 1987.
C40H56
536.90 Red prisms 177.5 352
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110
Fig. 2.36. Chemical structure of the most important carotenoids. OH
Fig. 2.37. Chemical structure of vitamin A.
hydroperoxide intermediates both in vitro and in vivo, thus breaking the chain reaction. The tocopherol content of different oils is given in Table 2.39; an overview is given by Woollard (1993) and Pryor (1993). Table 2.40 presents the physical and chemical data of tocopherols. 2.5.6 Special Compounds of Single Seeds and Oils
Some oilseeds give rise to extracted oils that contain components that make them less suitable for nutrition or restrict their usage in animal feed. There are continuTABLE 2.36 Physical and Chemical Data of Vitamin A (Retinoi, Axerophytol)a Vitamin A Chemical formula Form Soluble in Insoluble in Molecular weight Melting point
C20H300
("C) ("C) (OF)
uvnl,,
C22H3202
Palmitate C36H6002
Yellow crystals
(OF)
Boiling point
Acetate
(nm)
Pale yellow Yellow oil crystal powder or crystal mass Fats and oils, alcohol, ether, chloroform, acetone Water 286.46 328.5 524.9 63-64 57-60 28-29 14547 134.5-1 40 a2-84 1 73-1 38 at l o 6 hPa 343-352 at l o 6 hPa 325 326 326
aOne international unit (1 iu) corresponds to 0.300 pg all-trans-retinolor to 0.344 pg of highly pure retinyl acetate or to 0.549 Fg retinyl palmitate. One retinol equivalent (RE) corresponds to 1 pg all-trans-retinol. Sources: Roche 1970, CRC 1976, Ceigy 1968, Neumuller 1987, Wollard 1993.
111
Composition, Structure, Physical Data, and Chemistry
TABLE 2.37 Vitamin Content of Fish Oils
Liver oil Cod Sea-salmon Halibut Tuna Whale
A (1000 I.E./g) 0.2-1 0 1- 3 2 0-3 00 30-80 30-50
D (i.E./g) 60-300 8C-100 200&4000
-
Source: Baltes (1975).
Fig. 2.38. Chemical structure of vitamins D, and D3.
ous efforts to eliminate such compounds from the seed by new sorts of cultivation. In part, these efforts have already been successful (see Chapter 4.3.5rape), but for other seeds, these restrictions still exist. Some of these compounds are described in the following sections. TABLE 2.38 Physical and Chemical Data of Vitamin D (Calciferol)a ~
~
D2
Vitamin D
(Ergocalciferol)
Chemical formula Molecular weight Form Soluble in insoluble in Melting point
C28H440
396.63
("C)
("0 Sublimation at Density (20/4) ha,
(g/mL) (nm)
Prisms fats and oils (slightly),alcohol ether chloroform water 115-118 2 39-244 0.0006 hPa 1.39920, 264.5
aOne international unit (1 iu) corresponds to 0.025 pg of crystalline vitamin D, or D,. Sources: Roche (19701, CRC (1976), Ceigy (1 968), Neumuller (19871, Wollard (1993).
~
D3 (Cholecalciferol) C29H440
384.62 Needles
84-85 183-1 85
264.5
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112
Fig. 2.39. Chemical structure of tocopherols.
2.5.6.1 Sesarnol. Sesame oil contains small amounts of sesamol as well as -0.3% sesamolin, a glycoside of sesamol from which it can be obtained by hydrolysis. Additionally, there is 0.5-1.0% sesamin (Fig. 2.40, Table 2.41). 2.5.6.2 Gossypol. Gossypol is a major pigment in cottonseed and therefore a companion of cottonseed oil. It is a complex phenolic substance (Fig. 2.41, Table 2.42), forming poisonous yellow crystals that cause hemolysis by affecting membrane permeability; it does not appear in refined oil. However, it restricts the use of the meal (see Chapter 4.3.2).A detailed description is given by Marlunann and Rzhekhin (1969). 2.5.6.3 Glucosinolates of Rape. The glucosinolates of rape are derivatives of ally1 isothiocyanate (Fig. 2.42). Immediately after rapeseed has been reduced for extraction, hydolysis of the glucosinolate begins, transforming it into esters of isothiocyanicacid TABLE 2.39
Tocopherol Content of Oils and Fat9 Oh
OiVfat Palm oil Olive oil Soybean oil Cottonseed oil Sunflower seed oil Peanut oil Rapeseed oil Sesame oil Linseed oil Safflower oil Corn oil Palm kernel oil Coconut oil Cocoa butter Babassu oil Lard Tallow Fish oil
a 50-70 80-85 5-1 2 60-80 10-15 50 2-1 5
of Total tocopherols
P 0-6
0-4
-
0-7
-
-
0
0-2 90-95 37-50
0-1
-
-
c60 4-1 5
Y
6
3C-40 0-1 5 60-80 2wo 2-1 0 50 85-98
6-1 0
-
400-700 30-800 920-1800 900-1 100
0-4
500-800
0
15-30
-
0-2
0
95-98 5-6 5M3
0-1 0 0
c20 0-10
<20 75-97
c20
0-4
-
Total tocopherols (PPm)
0
480 800-1 200 188 1 1 0-280 300-3000 200-900 0
80 30-1 30 30 27 10 10
JSources:Lange (1950), Brown (1 952), Schmidt (19681, Taufel and Serzisko (1962), Cracian (19651, Hwrmann and G e m (19821, and Woollard (1993).
Composition, Structure, Physical Data, and Chemistry
113
TABLE 2.40 Physical and Chemical Data of Tocopherolsd Tocooherol -tocol Sum equation Molecular weight Form Soluble in Insoluble in (g/mL) Density Melting point (%C) ('/OF) Boiling point (%C)/at hP (%F)/at hP &ax (nm)
5,8-dimethyl
5,7,8-trimethyl
C28H4802
C29H5002
8- methyl
7,8-dimethyl C28H4802
C27H4602
416.66 Pale yellow viscous oil Oils and fats, alcohol, organic solvents Water
43 0.69
40.264
416.66
0.950 2.5-3.5 3 6.5-38.5 200-222113 39242811 3 294
200-2 1011 3 392-41 0/13 297
-3 to -2 2 6.5-2 8.5 200-2 1011 3 3 9 2 4 1 0/13 298
150176 302176 298
aOne international unit (1 IU) corresponds to 1 mg d!-a-tocopherol-acetate. Sources: Roche (1 970), CRC (1 976), Ceigy (1 968), Neumuller (19871, Wollard (1993).
Fig. 2.40. Chemical structure of sesamol (left) and sesamolin (right).
To prevent the formation of these harmful (for animal feed) substances, the enzyme thioglucosinase is inactivated by conditioning the seed (see Chapter 5.2.4.1). By cultivation of 00-rape varieties, the amount of glucosinates has decreased substantially so that they are now of minor importance. The ally1 isothiocyanates can rearrange to isothiocyanates or thiocyanates or decompose to nitriles and sulfur. A more detailed overview is given by McGregor (1993). TABLE 2.41 Physical and Chemical Data of Sesamol, Sesamin, and Sesamolin Sesamol Molecular weight Sum equation Form Melting point Boiling point
138.12 C7H603
("C) ("F)
("C) ("F)
Colorless crystals 65-66 149-50 135-1Mat 16 hPa 275-284 at 16 hPa
Source: Budkowski (1964), CRC (1976), Neumuller (1987).
Sesamin
Sesamolin
354.34
370.34
C20H1 8O6
CZOH184
Needles 123-1 24 253-255
White plates 93-94 199-201
Fats and Oils Handbook
114
OH
Fig. 2.41. Chemical structure of gossypol.
TABLE 2.42 Physical and Chemical Data of Gossypol 1,1’,6,6‘,7,7’-Hexahydroxy-5,5’-diisopropyl-
3,3’-dimethyl[2,2’-binaphtalenel-8,8’-dicarboxy-aldehyde Molecular weight 518.84 Sum equation Form Melting point
C30H3008
(“C) (OF)
Canary yellow (poisonous) crystals 184 (crystallized from ether) 363
Source: Neurnuller 1987.
Fig. 2.42. Chemical structure of rape glucosinolates. References Aho, L., and Wahlroos, O., (1967) A Comparison Between Determinations of the Solubility of Oxygen in Oils by Exponential Dilution and Chemical Methods, J. Am. Oil Chem. SOC.4 4 , 6 5 4 6 . Bailey, A.E., (1950) Melting and Solidification of Fats, Interscience Publishers, New York. Bailey, A.E., (1951) Industrial Oil and Fat Products, Interscience Publishers, New York. Bailey, A.E., and Singleton, W.S. (1945) J. Am. Oil Chem. SOC. 22, 265. Bakes, J., (1975) Gewinnung und Verarbeitung von Nahrungsjetten, Paul Parey Verlag, Berlin. Baur, F.J., Jackson, F.L., Kopl, D.G., and Lutton, E.S., (1949) J . Am. Chem. SOC. 71, 3363-3366.
Composition, Structure, Physical Data, and Chemistry
115
Belitz, H.-D., and Grosch, W., (1982) in Lehrbuch der Lebensmittelchemie, Springer Verlag, Berlin. Berg, T.G.O., and Brimberg, U.I., (1983) Uber die Kinetik der Fettkristallisation, Fette, Seifen, Anstrichmittel 85, 142-149. Bernardini, E., (1985) Oils and Fats Processing, Publishing House, Rome. Blanc, J., (1969) Techniques modernes de fabrication des margarines, Rev. Fr. Corps Gras 16,457471. Boekenoogen, H.A., (1935) Die Viskositat der fetten Ole, Fettchem. Umschau 42, 177-180. Boekenogen, H.A., (1941) Olien Vetten, Oliezandan 26, 143, from Hilditch, T.P., and Williams P.N., ( 1 W ) The Chemical Constitution of Natural Fats, Chapman & Hall, London. Brown, F., (1952) The Estimation of Vitamin E, Biochem. J. 52, 523-526. Budkowski, P., (1964) Recent Research on Sesamin, Sesamolin and Related Compounds, J. Am. Chem. SOC.41, 280-285. Chapman, D., (1957a) The Structure of the Major Component Glyceride of Cocoa Butter and of Major Oleodisaturated Glyceride of Lard, J. Chem. SOC.1502-1508. Chapman, D., (1957b) Infrared Spectra and the Polymorphism of Glycerides III,Palmitodistearins and Dipalmitostearins,J. Chem. SOC.2715-2720. Chapman, D., (1957~)The 720 cm-1 Band in the Infrared Spectra of Crystallized Longchain Compounds IV, J. Chem. SOC.489-4491. Chapman, D., (1960) Infrared Spectroscopic Characterization of Glycerides, J. Am. Oil Chem. SOC.37,73. Charbonnet, G.H., and Singleton, W.S., (1947) Thermal Properties of Oils and Fats VI, Heat Capacity, Heats of Fusion and Transition and Entropy of Trilaurin, Trimyristin, Tripalmitin and Tristearin, J. Am. Oil Chem. SOC.24, 140-142. Chevreuil, M.E., Recherches sur les Corps Gras, 1823. Chibnall, A.C., Piper, S.H., and Williams, E.F., (1953) Biochem. J. 55,707. Clark, P.E., Waldeland, C.R., and Cross, R.P., (1946) Specific Heat of Vegetable Oils from 0°C to 280°C, Ind. Eng. Chem. 38,350-353. Clarkson, C.E., and Malkin, T., (1934) Alteration in Long Chain Compounds 11: An X-Ray 666-671. and Thermal Investigation of the Triglycerides, J. Chem. SOC., Codex Alimenturius of the Food and Agricultural Organization (FAO), United Nations, Rome. Copius Beereboom, J.W., and Beekes, H.W., (1962) The Analyses of Mixtures of Animal and Vegetable Fats. 111. Separation of Some Sterols and Sterol Acetates by Thin Layer Chromatography, J. Chromatogr. 9, 3 16-320. CRC, Handbook of Chemistry and Physics, CRC Press, Cleveland, Ohio, 1976. Daubert, B.F., and Lutton, E.S., (1947) X-Ray Diffraction Analyses of Synthetic Unsaturated Monoacid Diglycerides, J. Am. Chem. SOC.69, 1449. Detwiler, S.B., and Markley, K.S., (1940 )Smoke, Flash and Firepoints of Soybean and Other Vegetable Oils, Oil & Soap 1 7 , 3 9 4 0 . Eckey, E.W., (1954) Vegetable Oils and Fats, Reinhold Publishing Co., New York. Erikson, D.R., and List, G.R., (1985) Storage, Handling, and Stabilization of Edible Fats and Oils, in Bailey's Industrial Oil and Fat Products, Vol. 111, (Appelwhite, T.H., ed.), pp. 273-3 10, John Wiley & Sons, New York. Evans, H.M., Emerson O.H., and Emerson G.A., (1936) The Isolation from Wheat Germ Oil of an Alcohol, Having the Properties of Vitamin E, J. Biol. Chem. 113,319-332.
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Fabris, A,, and Vitagliano, M., (1955) Richerche sull’hsaponificabile degli Olii e di Alcuni Grassi; Il Dosamento degli Idrocarburi Totali, dell0 Squalene e delle Sterine, Ann Sper. Agr. Nuova Sene 45,625-659. Fedeli, E., Lanzani, A., Capella, P., and Jacini, G., (1966) Triterpene alcohols and sterols of vegetable oils, J. Am. Oil Chem. SOC. 43,254-256. Fehling, H., (1845) Die Sauren des Cocosnubols, Ann. 53,399-41 1. Filer, L.J., Jr., Sidhu, S.S., Daubert, B.F., and Longenecker, H.E., (1946) X-Ray Investigation of Glycerides 111; Diffraction Analysis of Symmetrical Monooleyl-Disaturated Triglycerides, J. Am. Oil Chem. SOC. 68,167. Fitelson, J., (1943a) Detection of Olive Oil in Edible Oil Mixtures, J. Assoc. 08 Agric. Chem. 26,499-505. Fitelson, J., (1943b) The Occurence of Squalene in Natural Fats, J. Assoc. 08 Agn’c. Chem 26,506-510. Fitelson, J., (1945) Report on (The Analysis of) Oils, Fats and Waxes, J. Assoc. 08 Agric. Chem. 28,282-289. Formo, M.W., (1979) Physical Properties of Fats and Fatty Acids, in Bailey’s Industrial Oil and Fats Products (Swern, D., ed.),p. 188, John Wiley & Sons, New York. Furr, H.C., (1993) Retinol, Physiology, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 3907, Academic Press, London. Geigy, Documents Geigy, edited by von K. Diem and C. Lenmer, J.R. Geigy S.A., Basel, 1%8. Gbbmann, (1854) iiber die Arachinsaure, Ann. 89, 1-1 1. Gouw, T.H., Vlugter, J.C., and Roelands, C.J.A., (1966) Physical Properties of Fatty Acid Methyl Esters. VI. Viscosity, J. Am. Oil Chem. SOC. 43,433444. Gracian, J., Arevalo, G., and Martel, J., (1963) Caracteristicas del Aceite de Oliva de Produccion Nacional; Datos Correspondientes a las Provincias Andaluzas IV,El Indice de Escualeno y su Aplicacion con Fines Analiticos, Grasas y Aceites 14, 101. Gunstone, F.D., (1958) An Introduction to the Chemistry of Fats and Fatty Acids, Chapman & Hall Ltd., London. Gunstone F.D., Harwood, J.L., and Padley, F.B., (1986) The Lipid Handbook, Chapman & Hall, London. Gunstone, F.D., and Hilditch, T.P., (1945) The Union of Gaseous Oxygen with Methyloleate, Linoleate and Linoleate, J. Chem SOC. 836-841. Gunstone, F.D., and Padley, F.B., (1965) Glyceride Studies. Part 111. The Component Glycerides of Five Seed Oils Containing Linolenic Acid, J. Am. Oil Chem. Soc.42,957. Hadorn, H., and Jungkunz, R., (1953) Nachweis und annlhernde Bestimmung von Cruciferenolen in SpeiseBlen nach dem Bleisalzverfahren, Mitt. Gebiete Lebensm. Hyg. 44,453466. Handbook of Chemistry and Physics, (1976) CRC Press, Cleveland, OH. Hannewijk, J., Haighton, A.J., and Hendrikse, P.W., (1964) Dilatometry of Fats, in Analysis and Characterization of Fats, Oils and Fat Products, (Boekenoegen, H.A., ed.), Interscience Publishers, London, p. 118-182. Hartmann, L., (1958) Advances in the Synthesis of Glycerides of Fatty Acids, Chem. Rev. 58,845-867. Hell, C., and Hermanns, O., (1880) Ber. 13, 1713, quoted from Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constitution ofNatura1 Fats, Chapman & Hall, London. Henkel & Cie, (1971) Fettchemische Tabellen, 3rd ed., pp. 44-47.
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Herrmann, K., and Gertz, C., (1982) Hochdruckfliissigchromatographische Trennung individueller Tocopherole und Tocotrienole in Speisefetten und Speiseiilen an Kunsaulen, Lebensmittelchemie u. gerichtl. Chemie 36,53-58. Hilditch, T.P., (1935) The Fats: New Lines in an Old Chapter of Organic Chemistry:Jubilee Memorial Lecture, Chem.Ind.. 34,139-145,163-167. Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constirution of Natural Fats, Chapman BE Hall, London. Hoerr, C.W., Pool, W.O., and Ralston, A.W., (1942) The Effect of Water on the Solidification Points of Fatty Acids, Solubility of Water in Fatty Acids, Oil & Soap 19, 126- 128. Itoh, T., Tamura, T., and Matsumoto, T., (1973) Sterol Composition of 19 Vegetable Oils, J. Am. Oil Chem. Soc.50,122-125. Iverson, J.L., Eisner, J., and Firestone, D., (1%5) Detection of Trace Fatty Acids, J. Am. Oil Chem. SOC. 42,1063. Joglekar, R.B., and Watson, H.E., (1928) Rysical Properties of Pure Triglycerides, Ind. Inst. Sci. 47,365-368T. Jumens, G., (1968) in Analysis and Characterization of Oils, Fats and Fat Products, (Boekenoogen, H.A., ed.), Interscience Publishers, London. Kalu, C.U., and Hamilton, R.J., (1992) Triglycerides, Structure and Properties,in Enqcropaedia of Food Science, Technology and Nutrition, p. 463 1, Academic Press, London. Kartha, A.R.S., (1951) Studies on the Natural Fats, Ph.D. Thesis, University of Madras, India. M a , A.R.S., (1953a) The Glyceride Structure of Natural Fats. I. A technique for the quantitative determination of Glyceride Types in Natural Fats, J. Am Oil Chem SOC. 30,280-282. Kartha, A.R.S., (1953b) The Glyceride Structure of Natural Fats. II. The Rule of Glyceride Type Distribution of Natural Fats, J. Am. Oil Chem SOC.30,326-329. Kartha, A.R.S., (1954) The Glyceride Structure of Natural Fats. III.Factors Goveming the Content of Fully Saturated Glycerides, J. Am. Oil Chem. SOC. 31.85. Kartha, A.R.S., (1962) Glyceride Type Distribution Rule Calculations, J. Am. Oil Chem. SOC. 39,272. Kaufmann, H.P., (1958) Neuzeitliche Technologie der Fette und Fettprodukte, Mtinster. Kaufmann,H.P., and Mankel G., (1964) h r das Vorkommen von trans-Fettshen, Fette, Seifen, Anstrichmitte 661,613. Kun, T.Y.,and Ibrahim, A., (1991) Palm Olein Improves Cooking Oil Blends, Palm Oil Developments 3, Sept. 1991. Lange, W., (1950) Cholesterol, Phytosterol, and Tocopherol Content of Food Products and Animal Tissues, J. Am. Oil Chem Soc. 27,414422. Lerch, f.U., (1844) h r die fluchtigen Siiuren der Butter, Ann. 49,212-231. Litchfield, C., (1970) Taxonomic Patterns in the Fat Content, Fatty Acid Composition and Triglyceride Composition of Palmate Seeds, Chem. Phys. Lipids 4,96103. Litchfield, C., (1971a) Positional Distribution of Medium Chain Length Fatty Acids in Dicotyledon S e e d Triglycerides, Chem Phys. Lipids 6,200-204. Litchfield, C., (1971b) The Distribution of Oleic, Linoleic and Linolenic Acids in Cruciferae Seed Triglycerides, J. Am. Oil ChemSoc. 48,467472. Litchfield, C., (1973) Taxonomic Patterns in the Triglyceride Structure of Natural Fats, Fette, Seifen, Anstrichmittel 75,223-23 1. Loskit, K., (1928) Zur Kenntnis der Triglynride, 2 physik. Chem. 134,135-155.
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Lund, J., (1922) Die Beziehungen zwischen den Fettkonstanten, Z. Untersuch. Nahrungs. u. Genubmittel44, 113-187. Maiyar, A.C., and Norman, A.W., (1993) Cholecalciferol, Physiology, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 919, Academic Press, London. Malkin, T., and Shurbagy, M.R., (1936) An X-Ray and Thermal Examination of the Glycerides 11: The a-Monoglycerides, J. Chem. SOC. 1628. Malkin, T., Shurbagy M.R., and Meara M.L., (1937) An X-Ray and Thermal Examination of the Glycerides 111: The a-Diglycerides, J. Chem. SOC. 1409. Markley, K.S., Fatty Acids, Interscience Publishers, New York, 1947 and 1960. Markmann A.L., and Rzhekhin V.P., (1969) Gossypol and Its Derivatives, Israel Program for Scientific Translations, Jerusalem. Marsson T., (1842) ijber Laurin und das feste Fett der Lorbeeren, Ann. 41,329-336. Martin J.B., (1953) Preparation of Saturated and Unsaturated Symmetrical Monoglycerides, J. Am. Chem. SOC.75,5482. Mattson, F.H., (1962) Synthesis and Properties of Glycerides, J. Lipid Res. 3,281-296. Mattson, F.H., (1963) The Specific Distribution of Unsaturated Fatty Acids in Triglycerides of Plants, J. Lipid Res. 4, 392. Mattson, F.H., and Volpenheim, R.A., (1961a) The Specific Distribution of Fatty Acids in the Glycerides of Vegetable Fats, J. Biol. Chem. 236, 1891-1894. Mattson, F.H., and Volpenheim, R.A., (1961b) The Use of Pancreatic Lipase for Determining the Distribution of Fatty Acids in Partial and Complete Glycerides, J. Lipid Res. 2 , 5 8 4 2 . McGregor, D.I., (1993) Glucosinolates, in Encyclopaedia of Food Science, Food Technology and Nutrition, Academic Press, London. Mislow, K., and Bleicher, L., (1954) The Configuration of Cerebronic Acid, J. Am. Chem. SOC. 76,2825-2826. Monick, J.A., Halden, H.D., and Marlies, C.J., (1946) Vapor-Liquid Equilibrium Data for Fatty Acids and Fatty Methyl Esters at Low Pressures, Oil & Soap 23, 177. Morgan, D.A., (1942) Smoke, Fire and Flash Points of Cottonseed, Peanut and Other Vegetable Oils, Oil & Soap 19, 193-198. Neumuller, Calciferol, in Rompp Chemielexikon; p. 557, Frankh’sche Verlagsbuchhandlung, Stuttgart, 1987. Neumiiller, Carotinoide, in Rompp Chemielexikon; p. 609, Frankh’sche Verlagsbuchhandlung, Stuttgart, 1987. Neumiiller, Gossypol, in Rompp Chemielexikon; p. 1543, Frankh’sche Verlagsbuchhandlung, Stuttgart, 1987. Neumiiller, Sesamol, in Rompp Chemielexikon; p. 38 18, Frankh’sche Verlagsbuchhandlung, Stuttgart, 1987. Neumiiller, Squalen, in Rompp Chemielexikon; p. 3941, Frankh’sche Verlagsbuchhandlung, Stuttgart, 1987. Neumiiller, Tocopherol, in Rompp Chemielexikon; p. 4286, Frankh’sche Verlagsbuchhandlung, Stuttgart, 1987. Noureddini, H., Teoh, B.C., and Clements, L.D., (1992a) Densities of Vegetable Oils and Fatty Acids, J. Am. Chem. SOC.69, 1184-1 188. Noureddini, H., Teoh, B.C., and Clements, L.D., (1992b) Viscosities of Vegetable Oils and Fatty Acids, J. Am Chem SOC. 69, 1189-1 191. Pardun, H., (1969) Analyse der Fette und Fettbegleitstoffe, in Handbuch der Lebensmittelchemie, Vol. IV,p. 481, Springer Verlag, Heidelberg.
Composition, Structure, Physical Data, and Chemistry
119
Pardun, H., (1988) Die Pflanzenlecithine, Verlag fiir die chemische Industrie, (Ziolkowsky, H., ed.). Pardun, H., (1989) Pflanzenlecithine - wemolle Hilfs- und Wirkstoffe? Fat Sci. Technol. 91, 45-58. Parsons, L.B., and Holmberg, C.O., (1937) The Estimation of Water in Salad Oil and Determination of Its Solubility at Ordinary Temperatures, Oil & Soap 14, 239-241. Patton, St., McCarthy, R.D., Evans, L., and Lynn, T.R., (1960) Structure and Synthesis of Milk I, J. Dairy Sci. 43, 1187-1 195. Perry, E.S., Weber, W.H., and Daubert, B.F., (1949) Vapor Pressure of Phlegmatic Liquids I: Simple and Mixed Triglycerides, J. Am. Chem. SOC.71, 3720-3726. Propjak, G., Hunter, G.D., and French, T.H., (1953) Biosynthesis of Milkfat in the Rabbit from Acetate and Glucose; the Mode of Conversion of Carbohydrate into Fat, Biochem. J. 54, 238. F‘ryde, E.H., (1985) Fatty Acids, The American Oil Chemists’ Society, Champaign, IL. Pryor, W.A., (1993) Tocopherols, Physiology, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 4575, Academic Press, London. Rescoria, A.R., and Camahan, F.L., (1936) Animal and Vegetable Oils, I d . Eng. Chem 28, 1212. Riiner, U., (1970) Investigation of the Polymorphism of Fats and Oils by Temperature Programmed X-Ray Diffraction, Lebensmittelwiss. u. Technologie 3, 101. Rimpl, E., (1963) personal communication by H. Pardun, Analyse der Fette und Fettbegleitstoffe; Handbuch der Lebensminelchemie, Vol. IV,p. 481, Springer Verlag, Heidelberg, 1969. Roche, Vitaminkompendium, Hoffmann LaRoche AG, Basal, 1970. Rodriguez-Amaya, D.B., (1993) Carotenoids, Properties and Determintion, in Enzyclopaedia of Food Science, Food Technology and Nutrition, p. 707 Academic Press, London. Sato, K., and Kuroda, T., (1987) Kinetics of Melt Crystallization and Transformation of Tripalmitin Polymorphs, J. Am. Oil Chem. SOC.64,124-127. Schmidt, H.E., (1968) Bestimmung von Tocopherolen in Olen und Fetten: EinfluB des Tocopherol-Gehaltes von Erdnub- und Sojaol auf den Oxydationsverlauf dieser Ole beim Erhitzen, Ferre, Seifen, Ansrrichmittel70, 63-67, 159-61. Schneider, M.,(1992) Lecithine-Gewinnung, Eigenschaften und Bedeutung fiir die industrielle Anwendung, Far Sci. Technol. 94, 524-533. Sebedio, J.L., and Ackman, R.G., (1979) Some Minor Fatty Acids of Rapeseed Oil, J. Am. Chem. SOC.56, 15-2 1. Seher, A., and Gundlach, U., (1982) Isomere Monoensluren in PflanzenBlen, Fene, Seifen, Anstrichmittel 84, 342-349. Sieber, R., ( 1995) Konjugierte Linolsauren in Lebensmitteln: eine UbersichtJConjugated Linoleic Acids in Food: a Review; Emiihrungflutrition 19, 265-270. Sigurgislad6ttir, S., and Pglmad6ttir, H., (1993) Fatty Acid Composition of Thirty-Five Icelandic Fish Species, J. Am. Oil Chem. SOC.70, 1081-1087. Sherwood, P.W., (1960) Survey of the Chemical Utilization of Propylene, Ind. Chem. 36, 542-546. Sonntag, N.O.V., (1979) Structure and Composition of Fats and Oils, in Bailey’s Industrial Oil and Furs Products. (Swern, D., ed.), pp. 1-98. John Wiley & Sons, New York. Stage, H., (1977) Feinvakuumdestillationsanlagen im Lichte des Umweltschutzes, Seifen, Ole, Fette, Wachse 103, 151-154,207-210,269-272.
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Stage, H., (1979) Heutiger Entwicklungsstand der Anlagen zur physikalischen Raffination pflanzlicher Ole, Seifen , Ole, Fette, Wachse 105, 395401. Stage, H., (1982) Moglichkeiten des Umweltschutzes bei der physikalischen Raffbation und Fettsauredestillation, Ferte Seifen Anstrichmitte 841,333-338. Steinberner, U., and Preuss, W., (1987) Glycerin-Ein fettchemischer Grundstoff im Wandel der Zeiten, Fett: Wissenschafr Lutd Technologie 89,297-307. Swern, D. (ed.)(1982) Bailey’s Industrial Oil and Fat Products, John Wiley & Sons, New York. Taufel, K., and Serzisko, R., (1962) Zum Tocopherolgehalt einiger Fette und Ole; 2. Mitteilung: Verteilung der Tocopherole in ausgewwten Produkten, Nahrung 6,413422. Taufel, K., Heinisch, H., and Heimann, W., (1940) Zur Frage der Verbreitung von Squalen in pflanzlichen Fetten, Biochem Z 303,324-328. Thorl, Festschrift “75Jahre mrl”, F. Thorl’s Vereinigte Harburger blfabriken, 1958. Tsujimoto, M., (1906) Regarding Shark Oil, J. SOC. Chem. Ind. Jpn. 9,953-958. Ucciani, E., (1995) Nouveau Dictionaire des Huiles V~g~tales-Compositions en Acides Gras, Lavoisier Tec & Doc, Paris. Urakam, C., Oka, S., and Han, J.S., (1976) Composition of the Neutral and Phospholipid Fractions from Ginkgo Nuts and Fatty Acid Composition of Individual Lipid Classes, J. Am. Oil Chem. SOC. 53,525-529. Volcker, A., (1848) Behenol, Ann. 64,342-346. Wan, P.J., (1991) Properties of Oils and Fats, p. 39 in Introduction to Fats and Oils Technology, AOCS Press, Champaign 1991. Weber, E.J., (1981) Compositions of Commercial Corn and Soybean Lecithin, J. Am. Oil Chem. SOC. 58,898-901. Wesdorp, L.H., (1990) Unilever Research Vlaardingen, personal information. Wheeler, D.H., Riemenschneider, R.W., and Sando, E.W., (1940) Preparation, Properties and Thiocyanogen Absorption of Triolein and Trilinolein, J. Biol. Chem 132,687-699. Wissebach, H., (1969) Pflanzen und Tierfette (ausgenommen Milchfette). Vorkommen, Gewinnung, Zusammensetzung, Eigenschaften Verwendung, in Lebensmirtelchemie, Vol. IV,Fette und Lipoide p. 9-147, Springer Verlag, Berlin. Woollard, D.C., (1993a) Tocopherols, Properties and Determination, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 4569, Academic Press, London. Woollard, D.C., (1993b) Retinols, Properties and Determination, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 3901, Academic Press, London. Woollard, D.C., (1993~)Cholecalciferol, Roperties and Determination, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 912, Academic Press, London. Zabik, M.E., (1962) Correlation of Smoke Point to Free Fatty Acid Content in Measuring Fat Deterioration from Consecutive Heatings, Food Technol. 16, 111.
Chapter 3
Animal Fats and Oils Animal fats can be categorized as milk fats, rendered fats, and fish oils (marine oils). The main representative of milk fats is the fat of cow's milk (milk fat, butter fat, butter oil), All other milks are of almost no importance as far as their fats are concerned. They have their importance as such or as the base for milk products and cheeses. Even when consumed in high tonnages, their fat is not processed separately but as an integral part of that kind of food. Traditionally, the production of butter is a subject of dairy technology. It is therefore described only briefly in Chapter 8. Rendered fats, even if produced in high tonnages, are by-products of meat production. There is no livestock that is bred for its fat. In this respect, rendered fats differ from at least some of the oilseeds, which are grown mainly for oil production with the meal being a by-product. Marine oils are usually by-products of fish caught to be processed as a protein source. However, there are also some fish that are caught with the main purpose of oil production. As a source, a broad spectrum of species from small fish such as sardines to large mammals such as whales is available (in the case of whales, one has to say was available). In total, animal fat production was recorded at -20 MMT (ISTA Mielke 1994), consisting of -7 MMT of tallow and grease, 5.5 MMT of lard, 6 MMT of butter fat, and 1.2 MMT of fish oil. Milk fats, rendered fats, and marine oils differ considerably in their fatty acid composition. Compared with other fats, milk fats contain remarkable amounts of short-chain fatty acids ranging from C4to Clo. Fats from adipose tissue consist of saturated fatty acids, whereas marine oils contain huge amounts of polyunsaturated fatty acids, poly in this case in the real sense of the word, meaning more than three. The fatty acid composition can be influenced to a limited extent by the fodder of the animals. This is especially true for poultry. The linoleic acid content of poultry fat can be increased, for example, by feeding large amounts of grain. Compared with normal feed, lard is softer if pigs are fed mainly with corn or peanuts. However, the potential degree of influence is usually low. As always in nature, there is a striking and interesting example to prove the opposite. The birgus latro crab, which lives in the sea around the Seychelles islands, has as its only fodder the coconuts that have fallen on the beach. The crab's body fat has almost the same composition as that of coconut oil (Hilditch and Muti 1939). The higher the animals stand on the ladder of evolution, the lower the probability that their fatty acid composition will be influenced by their diet. Because fat production is typically only a by-product of meat production, attempts to change the fat composition by changing the feed remained mainly of academic interest. The only exception were trials in the 1970s to increase the linoleic acid content of milk fat in an attempt to avoid the debate concerning the negative influence of milk fat on coronary hem disease. 121
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122 Butterfat (milk fat)
Flrh oll
Milk
&
I
1 - 1
1
Buner fst
”
>=--
Tallow, lard
Fish dl
Fig. 3.1. Animal fat production; schematic overview.
In the sections that follow, the fatty acid composition of different fats is given. The sources from which the data were taken are represented by Roman numerals which correspond to the literature index (Chapter 3.4.1). Very detailed information can be found in Hilditch and Williams (1964). The data refmed to as FA0 were taken from the yearly bulletin of the United Nation’s Food and Agricultural Organization.
3.0 Summary Matrices with animal fat are totally different from those of vegetable fats. The adipose tissue of meat stock is used for fat production, whereas a large proportion of the fat remains with the meat and is consumed directly with the meat or processed into meat products such as sausages. In dietetic terms, it becomes “invisible” fat (see Chapter 1.4). Fat from meat stock is produced by rendering and subsequent separation via presses or centrifuges (Fig. 3.1). The residue is dried and used as animal feed. Fish oil production follows the same pattern. The solid residue is dried and sold as fish meal. Butter fat (oil) is produced mainly by melting and clarification of butter.
3.1 Milk Fats
’
In addition to protein and the other components that are necessary for mammals to raise their young, all milks contain fat as a source of energy and as a carrier for fatsoluble vitamins. At first sight, the fat content is not very high (Table 3.1). However, fat accounts for approximately one third of the dry matter. In total, roughly 20 million tons of milk fats are produced per annum (Table 3.2). A majority of the milk fat is consumed with the milk as such or in milk products such as cheese, cream or yogurt. The remainder is used for butter production (see Chapter 8.1). Part of the butter is processed further to butter fat. The fatty acid composition of milks is special in that milks contain relatively high amounts of short-chain fatty acids. Because they can easily pass through the intestinal wall and even be directly resorbed via the portal vein without prior splitting, the short-chain fatty acids are easily digestible for the mammals’ offspring.
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TABLE 3.1 Mammalian Milk Composition (Average over Many RacesBreedsP Fat
Water
Carbohydrates
Protein
Milk
(%)
(YO) (% dry m)b
(YO) ( O h dry m)
(%)
cow Sheep Goat Horse Camel Human
88.5 81.6 86.6 91.1 87.1 87.7
3.7 7.5 4.2 1.3 4.2 4.4
4.6 4.4 4.8 6.3 4.1 6.9
3.2 5.6 3.6
32.2 40.8 31.3 14.0 32.6 35.8
40.0 23.9 35.8 70.8 31.8 56.1
2.1 3.7 1.0
(% dry m)
27.8 30.4 26.8 23.6 28.7 8.1
aSource: Ceigy (1968). b% dry rn, % dry matter.
Milk fats are characteristically different from body fats (Fig. 3.2). The dominating milk is cow’s milk; its fat is considered exclusively in Chapter 3.1.1. Details on the chemical or physical properties of milk can be found in Alais (1961), Kiermeyer and Lechner (1973), Veisseyre (1973, Tape1 (1976), Walstra and Jeuness (1984) and Wong (1988). 3.1.1 Fat of Cow’s Milk (Milk Fat, Butter Fat, Butter Oil)
Milk yield has been dramatically increased in the past 40 years and will be increased further-in some parts of the world also with the aid of hormones. Usually, the increased yield is a result of new breeds and improved feeding. The milk yield of German cows, for example, was 2,600 L per year in 1951; it increased to 4,000 L in 1976 and is >8,000L today. The best cows achieve yields of close to 16,000L. Today, embryos of high-yielding cows can be bought at auction sales. They are implanted into the uterus of other cows, thus ensuring that yield and overall production are increased (Table 3.3). The main “milk countries,” however, can be identified only if production data from the table are brought into relation with 8na or population
-
TABLE 3.2 Milk Producing Stock and World Milk and Milk Fat Production in 1994 Production (miI Iion/MMT)
Nu,mber
Milk
Fat
cowsa Buffalo Shew Goats
225.5 138.4 1 ,145.7 492.2
488.6 48.2 8.0 10.5
16.9 1.8 0.7 0.4
aMilk producing stock only. Source: IAO Production Yearbook 1994.
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Fig. 3.2. Fatty acid composition of different milks. of a country. If this is done, Denmark and Ireland (not in the table) stand out, countries with >5 million tons of milk per annum and a relatively small population. In the European Community, subsidized overproduction of milk became a severe problem in the 1980s when the so called “butter mountain” reached 1.4 MMT. Fixed subsidies accompanying a milk quota regulation system solved this problem. There still exists some discrepancy between demand and supply between certain regions; however, the overall situation seems to be balanced out. Current moves in world trade (GATT) are leading to further reductions in subsidies and probably to an eventual elimination of quotas. In Germany, the fat content of milk is slightly above 4%. It varies depending on feeding. The same can be said about the fatty acid composition. In areas in which cows cannot be left outside to grass all year round but are stable-fed during winter, there is a great difference between summer butter and winter butter. Summer butter usually has a deeper yellow color than the pale winter butter; it is also softer. The difference in consistency is due mainly to feeding and corresponds to the degree of unsaturation of the fatty acids, reflected by the iodine value (Fig. 3.3). Summer butter is produced during the grassing period when fodder is more unsaturated in its fatty acids. Winter butter properties come from silage fodder. Recently one succeeded in changing the milk fat composition towards higher oleic acid content and less saturates, by feeding rapeseed for instance (Frede 1992). This difference is no longer obvious in many countries; summer butter is frozen and blended with winter butter or winter butter is colored with carotene. Both measures are taken to obtain butter with similar properties and appearance year round.
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125
TABLE 3.3 Cow Milk and Butter Production in the World and in Some Selected Countries (MMT)
Total world
us. Brazil India Germany France Netherlands Poland UK Italy
1960
1970
1980
1990
1993
1994
324 57.0 5.9 8.1 20.5 25.0 7.0 12.5 12.0 9.2
364 53.2 7.3 8.9 21.7 27.5 8.2 15.0 13.0 9.4
42 3 58.1 1 1.4 3.2 24.5 32.1 11.8 16.3 15.9 10.8
469 66.0 13.2 22.5 24.0 27.5 11.3 15.4 15.0 10.9
461 68.3 15.7 30.6 28.1 25.3 11.0 12.6 14.8 10.3
459 69.7 15.8 30.0 28.2 24.9 10.8 12.2 15.0 10.3
1990
1993
1994
Butter and Chee Production Expressed as Fat (MMT) 1960 1970 1980 Total world
U.S. USSR EU (10) India
4.4 0.5 0.8 1.1 0.5
4.9 0.4 0.8 1.3 0.5
5.7 0.4 1.1 1.7 0.6
6.2 0.5 1.3 1.5 0.9
6.0 0.5
6.0 0.5
1.1 0.9
1.1 1.o
-
Source: UNION 1979 and F A 0 Production Yearbooks
Fig. 3.3. Iodine value of milk fat depending on the season (after Precht 1988).
-
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126
Butter fat is rich in palmitic and oleic acid (-25% each) and contains more shortchain fatty acids than most other fats. As with all ruminants, the t r m fatty acid (TFA) content is quite high. TFA are produced in the cow’s rumen during enzymic hardening. Naturally, fatty acid composition also depends on the breed, the feed and the area in which the cows are raised; thus a great variation in composition occurs (Fig. 3.4). 3.1.2 Milk Fat Production
As already mentioned, milk fat production is traditionally a branch of dairy technology because it has normally been produced from butter. Today, the following forms are differentiated: anhydrous milk fat, produced from fresh milk, cream or butter (fat content > 99.8%);anhydrous butter oil or anhydrous butter fat, produced from butter or cream (fat content > 99.8%);and butter oil or butter fat produced from butter or cream (fat content > 99.3%) (IDF Standards 1977). Although many industries such as the ice cream industry have been using butter for their products, the new trend is to use butter fat (anhydrous milk fat) because it is more homogeneous in terms of its processing properties. In some countries that allow reconstitution of butter, stockkeeping anhydrous milk fat is easier than storing butter. Further, processing of butter fat (for instance fractionation or hardening) is still restricted in some countries such as Germany; others are totally open in this respect. Traditionally, butter fat is obtained from butter. The membrane hulls around the fat globules of milk are destroyed by beating. Mechanical treatment induces agglomeration of the fat grains and phase inversion. Butter fat is then obtained by melting butter, separation of the fat phase, followed by clarification. Using the direct route
Fig. 3.4. Fatty acid composition of butter fat.
Animal Fats and Oils
127
from milk, cream is preconcentrated, the membrane hulls are destroyed and the fat directly separated by centrifugation of the highly concentrated cream (Fig. 3.7).
3.7.2.7Butter Oil (Butter Fat) Production from Butter. Butter oil production lines have an output of 1-10 ton/h (Fig. 3.6a). Usually deep frozen butter is used, which is warmed until it is pumpable. After complete melting in a plate heat exchanger (A) it is pumped into a buffer tank (B). If fresh butter is used, it is recommended to pass the butter through a vacuum chamber (C), thus easing the concentration steps that follow. The holding time in the buffer is necessary to ensure degassing of the molten butter. From the buffer, a self-discharging separator (D)splits the butter fat from the butter serum, concentrating the fat phase to 99.5%. The wet butter oil is heated again in a plate heat exchanger (E) to - W C ,and water is subsequently evaporated in a vacuum chamber @) to a maximum concentration of 0.1%. To recover heat, the butter oil is cooled countercurrently, passing (E) again. It is stored in (G). See also Figure 3.5. 3.7.2.2 Direct Milk Fat Production from Cream (Milk). A more or less novel process is to produce milk fat directly from full milk (Fig. 3.6b). To do so, cream which is obtained from milk by centrifugation passes a plate heat exchanger (H) and is heated to 55°C to inactivate lipolytic enzymes. It is fed into a self-cleaning centrifugal separator (J), which performs a preconcentration. The skim milk leaving the preconcentrator passes another separator (L) to recover residual fat. The skim milk leaves the plant countercurrently, heating the incoming cream as it is being cooled. In the late 1980s, the plant design contained a so-called clarifixator, a combination of preconcentrator and phase inverter. The latter was achieved using a toothed cavitation disc that breaks the emulsion by disintegrating the fat globules. This occurs when the cream concentrated in the first part of the clarifixator has reached a concentration of 75-80% fat. Today, this module of the processing Passing another line is no longer built. It has been replaced by a homogenizer (M). separator (N) and a plate heat exchanger (P),the butter oil is pumped via an evacuated vessel (0)into a storage tank (R). The part of the cream that was separated from the butter oil in (N) returns to the main stream to be partly reprocessed. This process is much less frequently used than milk fat production using butter as source material. One of the reasons is that butter from subsidized deep-frozen intervention stocks may be used.
3.1.3 Fact File of Butter Fat (Butter Oil, Milk Fat) Average (European) data for butter oil are given in Table 3.4 and Figure 3.9 and the triglyceride composition is given in Figure 3.8. See also Kermasha 1993).
3.2 Rendered Fats Bodies of cattle contain -5% fat, those of pigs -25%, whereas their carcass fat is 10 and 30%, respectively. Despite this relatively low percentage, the amount of
Fats and Oils Handbook
128
Full fa; milk
-
(3.5 4.3 %)
,
Cream
I
I
+
Cooling. @ing I l
c
>>> Skim Mik
Batch, 10-18'C, 2-10 h (without step N: 10-14%; 10 h) U
c
(if in step 111 t > 12% and ca.2h)
1
M'C, aeparaton. 2nd shge of Concentn(ion >>> Sweet crcam butter d u c t i o n >>> (sa8.1.5.5)
Skim milk
euitrr
usually rtomd d.ep frozen I
Holding for cwnpbh, making
Butter oil I
I
(99.5%)
I
Heating
to pumpability
to W C , pMe h u t exchanger; removal of water Water >>>
1 C
1
Cooiina
I
I
Butter oil
tO<WC
(> 99.9%)
Fig. 3.5. Flow chart of butter oil production from butter.
rendered fat produced per year is enormous as a result of the immense number of animals killed (Table 3.5). In the table, the difference between the number of slaughtered animals and quantity of animal stock is a consequence of the time required for the animals to reach the desired weight.
Animal Fats and Oils
129
Fig. 3.6. Plants for the production of butter oil from butter and from cream (redrawn courtesy of Tetra Lava1 Food AB, Lund). The determination of the amount of fat is not simple because a significant part is not processed separately but eaten with the meat without the consumer’s awareness (so-called hidden fat). Another substantial part is consumed in sausages, corned beef and other meat products. These hidden fats account for considerably more than half of the fats obtained from animal sources. The fat content of animals for slaughter has substantially decreased during the past 40 years. In the 1950s (in Europe) emphasis was placed on calorie intake, i.e., fat meat, whereas now the consumers ask for lean meat. In the 1950s in Germany, for example, the price for fat pork belly was 90% of that for lean pork chops; in the mid 1970s, it was 55%; and today it is <40%. The breeders, among others, followed this trend by breeding the 14-rib-pig and promoting lean races. As a result of such activities, the amount of fat per animal has drastically decreased. However, despite the decline of production in the former USSR, world lard production has
Fats and Oils Handbook
130
,+, Full fat milk
CIO'C
15
!c
vTfat)
!
Butt.rmilk
Conorntration Butter oil
(99.5% fat)
Fig. 3.7. Flow chart of direct butter oil production from milk. Butter oil
( > m.Q%Fat)
risen to about 5.5 MMT per year in the first half of the 1990s; the production of tallow and grease is just slightly <7 MMT. The carcasses of animals for slaughter vary in fat content depending on species, age, state and keeping (feeding) and sex (male, female, gelding). Although very lean meat is almost fat free (-1.5%), the fat content rises from medium fat (20%)to fat meat (30%) and reaches its maximum in adipose tissues (bacon fat, leaf fat), which can contain up to 95% fat (pig). Generally, the fat content rises from birth to killing but may have reached its maximum before killing (Fig. 3.10). As a matter of principle, female and gelded animals can be fattened more easily than males. Dahl(l973) reported that, under identical conditions, oxen accumulated 57% more adipose tissue than bulls. The kind of fat produced depended mainly on the genetic blueprint, i.e., its species. Feeding was found to influence the fatty acid composition but only to a limited degree. The same publication shows a proportionality between iodine value of the oils fed and the linoleic acid content of these pigs' lard. In general, one speaks about visceral (or
Animal Fats and Oils
131
Butter oil (fat) Tligly~xridrtype POP, MSO, SSLn, PSL POO, SOL LaSO, MPO, PSLn, PPL, MSL
MOO, SLL, SOLn LLL, OLLn CyOO, COL, LaLL, OLnLn LUn
LLnLn, CLL, CPLN, CyOL. CoCO
LnLnLn, CyLL, COOL. BuOO Proportion [mol%]
Fig. 3.8. Main triglyceride composition of butter oil (after Bornez 1992).
killing) fats from around the kidneys, the stomach, the intestine and the heart and about skeletal (or cutting) fats which are subcutaneous fats or fats from carcass butchery. During slaughtering, organs and cells are damaged so that their liquids are released. The enzymes present in these liquids can lead to lipolytic degradation. This is, of course, especially valid for lipases from the intestinal tract of the animals and consequently less critical for adipose tissues (skeletal or cutting fats) than for visceral or killing fats. The reaction rate of lipolysis increases with temperature but even at 4°C (-30°F) free fatty acids are formed quite rapidly (Figure 3.1 1). From the graph, it is clear that visceral fats are much more susceptible to hydrolysis. Consequently, fat production should take place as soon as possible after killing. 3.2.1 Fat Production
Fat can be produced batchwise with the use of manual techniques by melting the raw material in open vessels. It can also be done on a semi-industrial or industrial scale, semicontinuously or continuously. The quality of the source material depends mainly on the care taken during slaughtering. Overviews of different processing techniques are given by Dupjohann and Hemfort (1975) and Diipjohann (1989) who describe plants of Westfalia Separator AG (Figs. 3.12, 3.16, 3.18 and 3.19). A brief survey was presented by Hughes (1993).
Fats and Oils Handbook
132
TABLE 3.4 Fact File of Butter Oil (Milk Fat, Butter Fat) German: Milch-, Butterfett
French: graisse de beurre
Relative density Refractive index Saponification value Iodine value
(at 40°C; ref. water 20°C) (nD40) (mg KOH/goil) (Wijs method)
Spanish: grasa de mantequilla 0.9354.943 1.452-1.457 21 8-235 25-38 ~
Melting point:
28-38OC
Solids content at
("VF)
10/50
20/68
30/86
35/95
(YO)
43
18
5
0.5
World market price per MT
(average 1990)
~
1 5-25°C
Solidification point
3740 U.S. $
The draft Codex defines: Anhydrous milk fat, milk fat, anhydrous butter oil and butter oil are fatty products derived exclusively from milk and products obtained from milk by means of processes that result in almost total removal of water and nonfat solids. Ghee is a product obtained exclusively from milk, cream or butter by means of processes that result in almost total removal of water and nonfat solids, with an especially developed flavor and physical structure. Anhydrous milk fat or butter oil Milk fat, butter oil and ghee Minumum milk fat (% m/m) 99.8 99.6 Maximum water (% m/m) 0.1 Maximum free fatty acidsa 0.3 0.4 Maximum peroxide valueb 0.3 0.6
-
d m as oleic acid. bMilliequivalent of oxygenkg fat. a%
3.2.7.1 Slaughter. Slaughter was described in an overview by Troeger (1993). More detailed information was given by Prandl et al. (1988). It is essential for slaughter houses to strictly follow the rules of hygiene (for Europe issued as an EU directive, with certificates needed). This reduces the risk of microbiologic contamination from claws, coat or hide, sex organs, mouth, gullet, and the contents of stomach and intestine. The innards should be taken from the body in their entirety. It is very important to avoid major damage to the intestine and the lymphatic vessels so as to prevent quick degradation of the fats produced. For details on slaughter house hygiene, see the special literature, for example, Prhdl. 3.2.7.2 Batch and Semicontinuous Fat Production. The easiest (manual) way to extract animal fat batchwise is by finely grading the adipose tissue and melting it out in open vessels. Cracklings (greaves) and water collect in the lower part of the vessel and the fat swims on top. It is separated by decantation or by means of faucets built into the side wall. Mechanical disintegration helps to break up the structure and to ease fat release from the cells. Heating the fat-containing raw material also has the function of break-
Animal Fats and Oils
Fatty acid Butyric Caproic Caprylic Capric Lauric Myristic Palmitic Stearic C20+C22 Oleic Linokic C20 + C22
133
Proportion [K: C 410 C 6:O C 8:O C 10:0
c 12:o C 14:O C 16:O C 18:O sat. C 18:l C 18:2 unsat.
Trans fatty acids, total
2.8 1.4
0.8 2.0 2.2
-
-
3.8 2.8 1.7
3.0
- 3.5 5.5 - 13.5 24.5 - 36.5 6.5 - 13.0 1.5 19.5 - 32.5 1.2 - 3.3 3.5
e
2.0
-
7.5
Proportion [%
Fig. 3.9. Fact file of m i l k fat;
fatty acid composition.
ing up the cells and decreasing the fat’s viscosity. Depending on the type of fat, heating to 105°C decreases its viscosity to 15-20% of its value at 35°C (Sobstad 1990). Desirable side effects of heating are sterilization and enzyme deactivation; additionally, protein denaturation helps in breaking emulsions and separating the molten fat. This pattern of basic technological steps, namely, disintegration, heating and separation, can be found in all industrial rendering processes, however, in a further developed and more sophisticated form. Further development of this simple process includes melting in autoclaves in which heating is achieved by direct steam injection. Because the autoclaves are run batchwise, at best a semicontinuous process can be achieved when two or more autoclaves feed a press alternately. The process time in the autoclave is 4-6 h and the proTABLE 3.5 Stocks Slaughtered and M e a t Production in 1994 Number (million)
Cattlebeef Pigs/pork Sheep Goats Hens Turkeys
Stocks
Slaughtered
Meat production (MMT)
1288 a75 1,086 609 12,020 247
239 101 461 253
50.05 79.00 6.89 3.06
Source: F A 0 Production Yearbook 1994.
-
-
-
Fats and Oils Handbook
134
0
4
8
1 A-
2
*
a
2
4
t-ksl
Fig. 3.10. Composition of pigs, dressed weight (after Dahl 1973). cessing temperature is -150°C. An alternative is indirect heating of the autoclave. Using this process, the water of the fat-bearing material is evaporated and the fat is obtained at 110-1 15'C. The advantage of dry rendering is that considerably less effluent is created compared with wet rendering. Its disadvantage is that burning is possiFree fatty acids formed 2.0 I
[%I
I
I
0
1
2
3
4
5
6
7
8
9
storage at 4°C [days]
m
f
l
Fig. 3.11. Enzymic formation of free fatty acids during storage at 4°C (after Dahl 1973).
Animal Fats and Oils
135
Fig. 3.12. Semicontinuous dry rendering installation for processing animal raw tats (Westfalia Separator AC, Oelde).
ble, leading to poorer quality of the cracklings. Figure 3.13 gives the flow chart of the process that is schematicallyshown in Fig. 3.12. The fat bearing raw material (A) is fed to the processing line. After passing a metal detector (A), it enters a miner (B) for mechanical disintegration of the cells. After preheating in a melting tube (C), it enters the rendering tank @), i.e., the autoclave, which is described below. For continuous operation, several autoclaves have to feed one press. After switching off the vacuum pump, the content of the rendering tank is emptied via a sieve (E). There the cracklings are separated from the liquefied fat and the rekdual water. The retained cracklings are fed to a screw press 0. The fat is separated from the solids. Dripping fat from the sieves and fat obtained from the press are united and fed to a decanter (G) in which 8-2Wo of the solids are removed, these may be fed back to the press 0.After adding 1-2% of water and reheating, the fat obtained in the decanter is polished by a separator (H)and stored (J). If 10% of water is added to the fat before the decanter, a lighter colored oil is obtained (Dbpjohann and Hemfort 1975).
136
Fats and Oils Handbook
crud,kt
El
nt
Fig. 3.13. Flow chart of the dry rendering process.
All plants with a screw press should also have a metal detector to avoid damage to the press. There are different types of such equipment. The Krupp Maschinentechnik types consist of a screw conveyor (2.2 kW power supply) housed in a pipe containing a central plastic section. This section is equipped with a transmitter and a detection coil. The transmitter coil creates an electromagnetic field, which is received by the detection coil. If a metal piece passes this section, the field is distorted and an electrical current is induced in the detector. The signal created is amplified and operates a shutter that automatically opens to remove the metal particle from the stream of goods. Because this system also detects noniron metals, all metals can be separated. The capacity of dry rendering plants is limited by the throughput of the screw press (Fig. 3.14), which is fed by several autoclaves. In the screw press shown in Figure 3.14, the prepared fat-bearing material (A) is fed via the screw (1) into the press chamber (2)which holds the main worm shaft (3). The worm shaft is driven by an electrical motor (4) via a spur gear. The screw is housed in a horizontal cage (5) that allows the fat to separate (6) and retains the solids. The diameter of the screw rotating in this cage increases in the direction of the product flow to compensate for the volume loss due to the extracted fat and to increase pressure. The
Animal Fats and Oils
137
Fig. 3.14. Screw presses for the rendering industry (courtesy of Krupp Maschinentechnik GmbH, Hamburg).
138
Fats and Oils Handbook
fat flows through the slots of the cage, is conveyed out (7), and collected (B). The expeller cake (C, with 10% of residual fat) is broken (8) and conveyed for further processing. Depending on their size, common screw presses have a throughput of up to 4.5 M T h (Table 3.6). They are fed by the above-mentioned autoclaves shown in Figure 3.15. The prerendered meat pulp (P) enters the autoclave via (4). In this dry rendering process, the pulp is heated to sterilization temperature by contact with the inner walls of the double-jacketed vessel (3), which is steam heated (Sl). The electrically driven (2) double-walled shaft and the paddles of the stimr (1) are also heated by steam (S2). After sterilization, the content is pressed through a sieve disk (6) into the discharge opening (3,which is COM~C~XIto the stirrer shaft by the inner pressure. This causes further disintegration of the meadfat, making the following press extraction more effective. If sterilization is not necessary, a simpler layout can be chosen. A range of the size of such autoclaves is given in Table 3.7. To avoid the danger of spreading pathogens during processing and distribution of animal by-products, such offal has to be sterilized in pieces with a size not exceeding 50 mm, according to the European Union guideIine 90/667. To fulfill these prescriptions and to comply with the latest environmental legislation on emissions, which can hardly be met by the old autoclave generation, Krupp has replaced the above-mentioned autoclaves with a newly constructed continuous Helix sterilizer (Fig. 3.15). The Krupp Helix sterilizer is designed as a horizontal, cylindrical vessel rotating around its longitudinal axis with a charging chamber (B) on one end and a discharging chamber @) on the other end. The meat pulp (A) enters the chamber at a temperature between 133 and 14o'C. The atmosphere in the charging chamber (B), which is only half filled with meat pulp at s t e d h t i o n temperature, is kept at a minimum pressure of 3 bar. The headspace is saturated with water coming from the pulp. While passing the helix (C), which takes at least 20 min, the level of the pulp TABLE 3.6 Technical Data of Screw Presses for the Rendering Industry (Types EP; Krupp Maschinentechnik GmbH, Hamburg) EP-19
Input Output (cake) Residual fat in cake Required drive rating Size (excl. drive) (Lx D x H) Space required Length of screw Weight without drive Source: Krupp.
EP-07
EPb9
1 .0-1.9 2.0-2.8 3.1-6.2 0.6-1.2 1.3-1.8 2.0-4.0 10-12 10-12 10-12 90-1 10 110-132 30-45 3450x 1200x 1250 4550x 1360x 15OO 4550x 136Ox 1500
10 -1 900 5
15 -2550 10
15 -2550 105
Animal Fats and Oils
139
Fig. 3.15. Conventional autoclave sterilizer and novel Helix-sterilizer (courtesy of Krupp Maschinentechnik CmbH, Hamburg).
Fats and Oils Handbook
140
TABLE 3.7 Technical Data of Agitated Autoclaves (Type SSK, Suitable for Sterilization and Type E; Trademarks of Krupp Maschinentechnik CmbH, Hamburg) 12 (SSK) Cylinder data Length Diameter, inside Heating surfaced Autoclave data Length incl. drive Width Height Space required Weight Capacities Driving power Throughputb ~~~~~~~
~
Capacity incl. agitator (m3) 5.7 (E) 10.7(E)
14.7(E)
51
5000 1300 40
6000 1600 60
7000 1750 80
7440 2100 2712 10 25
7200 1500 4350-5850 10.8 13.7
8600 1800 4600-61 00 15.5 20.3
9750 2000 4800-6300 19.5 31.3
55 5-7
37 0.88-1.6
55 1.5-4.0
75 / 90 2.C-5.0
4700 1940
~~
Source: Krupp.
~lnclusiveagitator. bWithin an extraction line, depending on loading and unloading time, processing conditions and type of raw material.
remains constant. The headspace is completely water-saturated, thus ensuring sterilization. By the rotation of the windings, the meat pulp is continuously transported in partial quantities from the charging to the discharging chamber (D), which is equipped with a blade wheel. The sterilized meat pulp leaves at (F). This sterilizer can be used in any continuous plant design as shown in the following section.
3.2.7.3 Continuous Processes. Continuous plants consist of a sequence of machines for disintegrating and melting the raw material, separating the solids from the fat and the fat from the water. These machines are adjusted to each other by their throughput. Usually the wet rendering process is applied, i.e., heating by direct steam injection. Figure 3.16 shows such a plant, supported by its process flow chart (Fig. 3.17). The raw material (A) graded in the slaughter house is fed by conveyor screws (2) through a metal detector (3) into the mincer (4). Typically, the cutter consists of a rough cutter, precutter, double knife and a perforated plate with bores 4-8 mm in diameter. After prerendering in the melting tube (9,the disintegrated material enters the rendering tank (6), which is equipped with an agitator, steam regulator and deaerator. From the melting tank, the material is conveyed with an eccentric screw pump (7) to a decanter (8) where the residues (B) are separated from the liquid phase. This liquid consists of condensed steam, stickwater, liquefied fat and some residual solids. It is reheated in (9) and fed to a separator (1 1) by another eccentric screw pump (10). The solids (C) ejected from its self-cleaning bowl are fed back to the rendering tank (6).The fat leaving the separator is reheated and pumped to the second separation stage (12). For polishing, hot water may be
Animal Fats and Oils
141
Fig. 3.16. Wet rendering installation for processing animal raw fats with further degreasing of cracklings (redrawn courtesy of Westfalia Separator AG, Oelde).
added to improve separation. The polished fat obtained (D) is stored in (13). In case the residues are to be degreased further (residual fat content 4-8%), they (B) are conveyed into a storage tank where they are merged with the solids separated in (1 1) and (12). This mixture is reheated and passed through the clarifying decanter (14) and finally cleared via the separator (15). The fat emulsion (E) is then fed back into the rendering tank (9) and the solids (F) are added to the residues. The efficiency of the process can further be enhanced by introducing a separation decanter (8). As in the previous process (shown in Figure 3.16) the product is conveyed to the decanter by means of an eccentric screw pump (7) where the three phases
142
Fats and Oils Handbook
X
1
Fig. 3.17. Flow chart of animal fat production (lard, tallow, as in Fig. 3.16).
are continuously separated into fat, stickwater, and cracklings (B). The fat leaving the decanter is postheated in a tank (9) and fed to the separator (1 1) for fine clarification. Residual solids are removed (C) and the fat @) is stored in (15). Figures 3.19 and 3.21 show wet rendering plants (schematic and photograph), Figure 3.20 gives the respective flow diagram, and Table 3.8 liftsthe operational data. 3.2.7.4 Production of Bone Oil. Bone oil is extracted in plants equipped with an autoclave (Fig. 3.22). The bones are fed in at (l), broken in (2) and fed into a dry rendering autoclave (3, see also Figure 3.15, upper part) where they are thermally broken up and dried. Passing a prerendering unit with a built-in iron separator (4), the prepared raw material is fed into a screw press ( 6 ) after passing a buffer (5). The fat from (4) and (6) is combined and precldied in (7). A decanter (8) is used for the final separation of the fat (F)and the solids that were reprocessed in
Animal Fats and Oils 1.wO.O ko 750.0 kg
143
F W scum M M n l (100% Fat
75,O %
--n
Y
t
f
Fig. 3.18. Mass and energy balance of fat production, wet rendering process (after Dupjohann 1989/1996 and Westfalia Separator AG, Oelde).
(5). The press cake from (6) is ground (9) and conveyed to the meal storage (M). All vapors from the plant are condensed in (10) and the waste water (W) passes through an effluent treatment plant.
3.2.1.5 Solvent Extraction. This process is applied only for the extraction of animal fat for technical purposes (Fig. 3.23). The raw material is introduced via (1) and is conveyed into the stinwl autoclave after being disintegrated (2).In the autoclave (3), it is
144
Fats and Oils Handbook
Fig. 3.19. Wet rendering installation for processing animal raw fats using a separating decanter (redrawn courtesy of Westfalia Separator AG, Oelde).
sterilized and mixed with the solvent (usually perchloroethylene). The miscella (see also Chapter 5.2.4) is withdrawn through the bottom of the vessel, buffered in (4), and is recirculated for a second extraction step into the extractor (3). After the second use, the solvent is evaporated (5), and the crude fat is preclarified in (6)and pumped to the storage (F) after a fine clarification step in the decanter (7). Solid residues separated in (7) are fed back into the extractor (3). The solvent is evaporated from the solids, leaving the extractor (3) by direct steam (8). The bone/meat pulp is almost solvent free and comprises 4040% water. It is continuously dried in (9) and the dried meal is ground in a mill (10) and transported to the meal storage (M). The vapors, which contain some solvent, are condensed (1 l), and the water and solvent from the condensate are sepa-
Animal Fats and Oils
145
TABLE 3.8 Operational Data for a Wet Rendering Plant as Shown in Figure 3.1 9 (Courtesy of Westfalia Separator) Energy consumption
(kW/MT of raw fat) (kg/MT of raw fat)
Electrical energya Steam (3 barla Water consumption Hot water (t > 95%C) Cold water Operating water pressure YielddCapacities Capacity Fat yield
16-22 0.1-0.1 7
-250 -40 3
(MT of raw fat/h) (% fat content of raw material)
3 96-99
aDepending on type temperature on delivery of the raw material.
rated (12). The water is pumped to the effluent plant 0. All vapors from the plant that are difficult to condense are processed in a special treatment installation (L). In addition to the Krupp immersion plant described above (process flow chart in Figure 3.24), which is also available for continuous processing, plants for the percolation process are used (for example, De Smet extractors). In such plants, the raw material is broken up in a cooking step. The excess tallow is allowed to drip off onto a tray with a perforated bottom, thereby leaving a residue with typically 30-35% fat. This residue is coarsely ground so that the particle size (also bones) is reduced to <3 cm. Through a valve, the material is conveyed into the storage chamber of an extractor, which resembles those described in Chapter 5.2.3.4.3. The extracted material is separated from the solvent in a toaster; the solvent is evaporated from the miscella, conAdipose tissues
I
I
I
Sorting I
1 (5-6 rnrn diameter) 90-95'C, dired stearn
m Separation
Decanter
_ I
X
Fig. 3.20. Flow diagram of-fat production with rendering vessels.
146
Fats and Oils Handbook
Fig. 3.21. Wet rendering plant (Westfalia Separator AG, Oelde).
Animal Fats and Oils
147
Fig. 3.22. Plant for the press extraction of bone oil (Krupp Maschinentechnik GrnbH, Hamburg).
Fig. 3.23. Animal fat solvent extraction plant (Krupp Maschinentechnik GmbH, Hamburg).
Fats and Oils Handbook
148 Source material
I
1-L
Separation Mbmlla
I
hnter R
r Vapor mndrnution
t
I
Crude oil
~
Fig. 3.24. Flow diagram of solvent extraction (for technical use only).
densed and reused. There is no need for a miscella filtration because the material to be extracted acts like a filter cake and holds back all small particles. The loss of solvent (usually hexane) is <0.5%. 3.2.1.6 Combined Solvent Press Extraction. This process is similar to those described above. However, it combines solvent extraction and press extraction. The raw material is dried, first pressed and then solvent extracted. This lowers the amount of solvent that has to be removed, thus saving energy and reducing cost. In addition, plants exist that achieve the separation of miscella and extracted solid residue by pressing rather than decantation.
3.2.2 Lard The world population of pigs has increased considerably during the past five decades (Table 3.9). Currently, the world production of lard is -5 MMT per year. The dressed weight of pigs contains slightly above 30% fat (Fig. 3.25). Very fat pigs can contain more than 50% fatty matter, which is dispersed in the meat and concentrated in some fatty tissue, such as 6 5 % dressed weight (%dw) of bacon fat or leaf fat, 3%dw of cutting fat and 1% trimming fat. Lard is rich in palmitic and
Animal Fats and Oils
149
TABLE 3.9 Stock of Pigs and Lard Production in the World and in Selected Countries Stock of pigs Total world (M head) USSR
us. Brazil Germany FR Germany (former GDR) Sudan Mexico Poland Romania Vietnam Netherlands France Canada Japan Spain EU (10) Lard production Total world (MMT) USSR EU (1 0)
us. China PR
1935
1950
1960
1970
1980
1990
1994
50 32 22 12 -
20 59 25 10 -
530 58 56 53 15 7 9 13 5 9
567 56 61 66 20 9 7 10 14 6 6 11 7 6 7 65
779 74 57 34 23 12 18 19 20 11 9 10 11 11 10 10 78
857 79 53 33. 23 12
875 58 31 26
12 12 11 12 17 107
11 18 110
-
-
-
2 7 -
-
-
17 19 12
-
18 19 9 15 14 13 11
6 -
4 -
3 9 5 4 6 -
1935
1950
1960
1970
1980
1990
1994
2.9 -
3.0 -
4.4
4.4 0.6 0.7 0.8 0.5
4.0 0.7 1.0 0.5 0.8
5.4 0.8 1.2 0.4 1.6
5.7 1.2 1.2 0.4 2.0
2 7
-
-
-
0.5
0.5 0.9 0.4
Source: Schiittauf (1940), UNION (19791, and F A 0 Production Yearbook ( 1 994).
oleic acid (ratio 1:2), which account for three fourths of all lard fatty acids (Fig. 3.26). This has a strong influence on the triglyceride composition of lard. More than half of the triglycerides are composed of these two fatty acids, and 2-palmitodi-olein accounts for almost 20% (Fig. 3.27). Within limits, the composition of pig fat can easily be influenced by dietary intake.
Fig. 3.25. Composition of whole pigs and their dressed weight.
Fats and Oils Handbook
150
Fig. 3.26. Fatty composition of lard. Lard, which is partly modified via hardening and interesterification (Chapter 6.3 and 6.4), constitutes a good shortening for the baking industry and is used in the U.S.in large quantities. Because of traces of associated substances, it creates a nice crust and a special flavor in deep frying. It is therefore heavily used for baking
PPS, PSP
Pss. SPS
sss Wmr8
pop, Ppg MPO PSO. pos. SPO pm).
sos, sso oUvn MOO. OM0
oso. so0
wo OPO PPL SPL 0lh.n OOO PSO, SLO, SOL 0lh.n
sso
-
OOL. OLO PLL, SLL, W L n
WW
3.27. Triglyceride composition of lard (afterJurriens 1968).
Animal Fats and Oils
151
and deep frying despite the usually recommended restraint from animal fats. The definition for lard from the codex is as follows: “Lard is the fat rendered from fresh, clean and sound fatty tissues from swine (Sus scrofu) in good health, at the time of slaughter, and fit for human consumption as determined by a competent authority recognized in national legislation. The tissues do not include bones, detached skin, head skin, ears, nails, organs, windpipes, large blood vessels, scrap fat, skimmings, settlings, pressings, and the like, and are reasonably free from muscle tissue and blood. Rendered pork fat is the fat rendered from the tissue and bones of swine (Sus scrofu) in good health, at the time of slaughter, and fit for human consumption as judged by a competent authority recognized by national legislation. It may contain fat from bones (properly cleaned), from detached skin, from head skin, from ears, from tails and from other tissues fit for human consumption.” The values of the characteristic analytical parameters for lard and rendered pork fat differ only slightly from those given for lard in the fact file (Table 3.10 and Fig. 3.28). 3.2.3 Beef Tallow
The number of livestock cattle has increased by 50% over the past four decades (Table 3.11). The number slaughtered per year comprises 20% of the stocks; the world tallow production is currently -6 MMT. The proportion of fat in the dressed weight varies greatly (Fig. 3.29). Lean beef contains -8% fat, fat beef, up to 25%. On average, the proportion of visceral fat (or killing fat; from kidneys, stomach, intestine and heart) is -2% of the dressed weight of which -40% is kidney fat. TABLE 3.1 0 Fact File of Lard German: Schweineschmalz
French: saindoux
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 40°C; ref. water 20°C)
Spanish: manteca 0.896-0.904 1.448-1.460 192-203 45-70 < 10
(mg KOH/g oil) (Wijs method) (g/kg oil)
Melting point:
2840°C
Solids content at
(VF)
10/50
20168
Solidification point 30/86
35/95
(Oh)
65
50
25
15
World market price
Price index (1995 average compared to average) 10 years ago 81 o/o 20 years ago 96O/o
(US$/MT)
2 2 -32°C
min
0
max
1972-1995
170
465
763
1982-1 979 1980-1989 1990-1995
170 332 229
481 533 325
763 710 500
Fats and Oils Handbook
152 Lard
C 14:l
C 17:O C 17:l
C 20:4
<
1.0
Trans hay .cidr.hW
Fig. 3.28. Fact file of lard; fatty acid composition.
Including skeletal fats (or cutting fats), -3% of the animal’s body is fat (half of the share in pigs). The definitions for different quality grades are as follows: “Premier Jus (Synonym: Oleo Stock) is the product obtained by rendering at low heat the fresh fat (killing fat) of heart, caul, kidney, and mesentery collectTABLE 3.1 1 Stock of Cattle and Tallow Production in the World and Some Selected Countries Stock of cattle
1935
1950
1960
1970
1980
1990
1994
Total world (M head) U.S. Brazil USSR Argentina France Germany UK EU (10)
-650
798 80 51 56 42 16 11 10
1013 104 79 83 43 20 13 12
1118 110 95 95 48 22 14 13
1264 99 134 121 51 21 16 12 84
1288 101 152
-
1220 112 117 115 56 24 15 13 85
Tallow production
1935
1950
1960
1970
1980
1990
1994
Total world (MMT)
1.7
2.2
4.2 2.3 co.1 0.2 0.1 0.5 co.1
5.0 2.8 0.1 0.3 0.2 0.6 <0.1
6.3 3.2 0.1 0.4 0.2 0.9 0.1
6.8 3.2 0.2 0.4 0.2 1.0 0.3
7.0 3.2 0.2 0.3 0.2 1.0 0.4
us.
Brazil USSR Argentina EU (1 0) China PR
66 60 33 16 12 9
-
-
-
Source: Schuttauf (1940), UNION (1979), and F A 0 Production Yearbook (1994).
-
50 20 16 12 80
Animal Fats and Oils
153
Fig. 3.29. Compositionof whole cattle and their dressed weight. ed at the time of slaughter of bovine animals (Bos tuunrs) in good health at the time of slaughter and fit for human consumption as determined by a competent authority recognized in national legislation. The raw material does not include cutting fats. Edible Tallow (Synonym: Dripping) is the product obtained by rendering the clean, sound, fatty tissues (including trimming and cutting fats), attendant muscles and bones of bovine animals (Bos taunts) and/or sheep (Ovis aries) in good health at the time of slaughter and fit for human consumption as determined by a competent authority recognized in national legislation.” The characteristic chemical and physical parameters do not differ substantially between premier jus and edible tallow. Apart from these two, bone oil and neat’s foot oil are also produced. Bone oil from fresh marrow bone can be used for edible purposes; other bone oil and neat’s foot oil are allowed only for technical use. Beef tallow contains mainly palmitic, stearic and oleic acid (Fig. 3.30). Neat’s foot oil serves as a high-grade lubricant for fine mechanical instruments. Its special properties are said to be due to the palmito-di-olein it contains. Tallow contains a wide spectrum of fatty acids and triglycerides. More than 50 different triglycerides in concentrations S . 1 % each have been identified. Unlike most other fats and oils, there is no predominant triglyceride with a high share. Only two, namely, palmito-oleo-stearin and palmito-di-olein, have a proportion >lo% (Fig. 3.31). The fact file reflects the characteristics as given in the Codex Alimentarius (Table 3.12 and Fig. 3.32). 3.2.4 Mutton Tallow
Mutton tallow is produced mainly in countries with large stocks of sheep and high consumption of mutton. Around 450 million sheep and lambs are slaughtered yearly, yielding >6 MMT of meat. Assuming -3% of fat (living weight), this corresponds to -0.5 MMT of total fat or -0.2 MMT of rendered fat. In some countries
Fats and Oils Handbook
154
Fig. 3.30. Fatty composition of beef tallow.
sss pss, SPS MSM, MSP. MSS, MPP PPP others PSO, POS
s o , sos PPO, POP MOP, PMO others, tnnsqlymrider PSL. PLS, SPL OPO POP
oso. so0 MOO, OM0 POSO, SPOO. SOP0 PPOO, POW, POOP others. tranr-gtycsrider
000 SLO, OSL, SOL PLO, POL, LPO POOO, OPOO others. trana-giycsrider 0 0 L , OLO others Proportion [mol%]
Fig. 3.31. Triglyceride composition of beef tallow (after Jurriens 1968).
Animal Fats and Oils
155
TABLE 3.1 2 Fact File of Edible Tallow German: Rindertalg
French: sulf comestible
Relative density Refractive index Saponification value Iodine value
(at 4OOC; ref. water 20°C) (nD40) (mg KOH/g oil) Wijs method)
Melting point:
0.893-0.904 1.448-1.460 190-202 32-50
Solidification point
40-50°C
Solids content at
Spanish: sebo
30-38OC
( O U T )
10/50
20/68
30186
35/95
(YO)
65
45
25
15
World market price Price index (1995 average compared to average) 124% 15 1Yo 248% 385%
10 years ago 12 years ago 30 years ago 35 years ago
(US$/MT)
min
0
max
1960-1995
123
326
655
1960-1969 1970-1979 1980-1989 1990-1995
123 162 242 310
160 362 420 337
218 643 621 650
(for example, Iran) fat-tail sheep, which store fat in a deposit'under the tail, are raised. This is used for fat production by hanging the tail in a warm environment and collecting the fat dripping out in a small bucket. The fatty acid spectrum of mutton tallow resembles that of beef tallow with the predominant fatty acids being palmitic, stearic and oleic acid (Fig. 3.33) The proportion of tram fatty acids is very high (-10%). The definition of mutton tallow is the same as that of beef tallow (see Chapter 3.2.3). Table 3.13 gives the fact file of mutton tallow.
Edible tallow (premi
-
Fatty acid shod chain Myrirlic Myriotobic Pentadscanic iso, anteis0 Pairnnk Palmilobic Maw& Margarolsic iso, anteiso stoaric
Obic Linoleic Linolenic
1
CC14 C 14:O C 14:l C 15:O C 15 C 16:O C 163 C 17:O C 173 C 17 c 18:O c 18:l c 18:2 C 163
Trans fatty acids. total
IW 'roporlion[%]
Bone grease
~
14 05 05
< 25 78 18 10 c 15
-
170 - 3 7 0 07 88 05 20 < 10 05 - 20 6 0 -400 260 -500 05 50 < 25
-
-
-4
'roporlbn [%]
Fig. 3.32. Fact file of edible tallow; fatty acid composition.
0.2
. 1.6
1
-
0.5
. 2.0
5
18 -32 2.5 9
-
3 -16 43 - 6 2 1.5- 3 1
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Fig. 3.33. Fatty cornposition of mutton tallow.
3.2.5 Poultry Fat The number of poultry held world wide exceeds 10 billion. The fat that is obtained during killing is usually not processed separately. The fatty acid composition differs from species to species (Fig. 3.34). Except for goose fat, definitions can rarely be found. The German codex defines goose fat as follows: ''Goose fat is produced from the fatty tissue of geese and often for a better consistency is blended with declared propomons of lard." The fact file shows goose fat only (Table 3.14 and Fig. 3.35).
3.3 Marine Oils The term marine oils covers oils of all waterborne animals, fish or mammals, such as whales or seal. Hunting seal is of restricted regional importance only for TABLE 3.1 3 Fact File of Mutton Tallow German: Hammeltalg
French: suif de mouton
Relative density Refractive index Saponification value Iodine value
(at 40°C; ref. water 20°C) (nDa) (mg KOWg oil) Wijs method)
Spanish: sebo de corder0
0.893-0.904 1.448-1.460 190-202 32-50
~
Melting point:
45-50°C
Solidification point
Solids content at
("CpF)
10/50
20168
30186
35/95
(%)
60
37
20
12
30-38OC
Animal Fats and Oils
157
Fig. 3.34. Fatty composition of poultry fats.
Eskimos; consequently seal fat is not discussed here. A detailed description of the oils of almost all marine-born animals was given by Hilditch and Williams (1964); a survey of the present usage of marine oils is offered by Opstved et al. (1990). In the following paragraphs, the production of whale and fish oils is described. Whale oil is mainly of historical importance because only Iceland, Japan, and to a smaller extent, Norway, are countries still hunting whale. The amounts of oil, however, are negligible. Fish oil is a by-product of industrial fishing and the fish meal industry. Fish oil is therefore described in more detail. A debate is going on to restrict fish oil production to the amount that can be produced from sustainable fishing. In countries with a long shore line, such as Chile, for example, fish oil is of major importance. After slight hardening and fractionation, it can even be used as a salad oil. TABLE 3.14 Fact File of Goose Fat ~
~~
German: Ganseschmalz
French: graisse d'oic
Spanish: grasa de oca
Relative density Refractive index Saponification value Iodine value
(at 4OOC; ref. water 2OOC) (nD40) (mg KOH/g oil) (Wijs method)
0.902-0.906 1.456-1.462 191-1 98 59-81
Melting point:
25-37°C
Solidification w i n t
Solids content at
(VF)
10/50
20/68
30/86
35/95
(Oh)
35
18
5
1
16-22°C
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158
Fatty acid Myristic Paimnic Palmnoleic
stearic Oleic Linoleic Linolenic Elcosenic
C 14:O
C 16:O C 163 c 18:O c 18:l
c 18:2 C 18:3
c -
.
18.0 25.0 1.0 - 5.0 5.0 8.0 50.0 -64.0 6.0 15.0 0.5 5.5
.
. -
20:1
Proporlion [%I
Fig. 3.35. Fact file of goose fat; fatty acid composition.
3.3.1 Whale Oil
International agreements have eliminated whale hunting almost completely, so that whale oil is no longer of significant importance. Some 40 years ago it was still important, and 60 years ago, margarine producers, for example, Walter Rau in Germany, had their own fleet of whale hunting boats. In 1957, an international conference agreed on quotas that allowed the hunting of 16,000 so-called “blue whale units,” which is equivalent to -0.3 MMT of whale oil. However, until the 1960s, 0.5 MMT of whale oil was landed yearly. For illustration, the composition of blue whales is shown in Figure 3.36. The liver of blue whales contains -2.5% of an oil rich in vitamins; it was used to produce vitamin A concentrates. Apart from the liver, the following portions of oil can be found in the subcutaneous fatty tissue, the meat and the bones: blubber, -50%; meat, -12%; and bones, -35% (up to 52%). This means that up to 25% of a blue whale, which can weigh up to 135 MT, consists of oil. The oil of arctic whales consists of 30% unsaturated C22and C24fatty acids; that of antarctic whales contains only -20%. This is reflected in the fatty acid composition as shown in Figure 3.37. The triglyceride composition was described by Hilditch (1939) who reported the following values for arctic whale oil:
Fig. 3.36. Composition of blue whale bodies.
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159
Fig. 3.37. Fatty composition of whale oils.
8 mol% 66 mol% 12 mol% 6 mol% 4 mol%
C,,:,-myristic acid-palmitic acid x {14, 16, 20, 22) 18:n-Cx: n-Cx: 0 C18:n-(Cx:n)2 x {14, 16, 20, 22) (Cx:nh-Cx:~ (Cx:n)3 x I14, 16, 20, 221
where CXZn is an unsaturated fatty acid with x carbon atoms and n double bonds and CxZ0 is a saturated fatty acid with x carbon atoms. Whale oil quickly becomes rancid, because of its high amount of polyunsaturated fatty acids and therefore was only used after hardening. Until the 1950s, it was an important ingredient of margarine. The head oil of the sperm whale, the so-called sperm oil, contains -50% of unsaponifiable matter. It is comprised of >50% waxes (fatty acid esters of longchain alcohols) of mainly cetyl alcohol. Sperm oil used to be the basis of liniments (see also Chapter 4.4.3). After hardening, products with unique and interesting properties could be obtained. Today, jojoba oil is used mainly as a replacement for sperm oil. Analytic and characteristic parameters of oils from different whale species can be found in Wissebach (1969) as well as Hilditch and Williams (1964).
3.3.1.7 Whale Oil Production. Modem whale hunting fleets fully processed the whale on the high seas. Each factory ship was accompanied by 8-15 hunting boats. A factory ship was able to process 1-2 whales per hour, depending on their size. Processing 25 whales per day (average weight 75 MT) yields 470 MT of oil. To obtain this weight in oil, 12,OOO-13,OOOpigs weighing 150 kg each would have to be killed.
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To obtain the oil, the crude whale material is cooked and the oil is separated by decanters from the stickwater. The oil is clarified and collected, and the residues are further processed for glue manufacture (Fig. 3.38).
3.3.2 Fish Oil Fish oil is a by-product of the use of fishing as a source for protein or one of the two main products when whole fish is immediately processed for fish meal and fish oil production. The worldwide catch is -70 MMT per year. Populations of oil herring in the East Atlantic and of Menhaden in the West Atlantic have declined, leading to stagnation in the production of fish meat and fish oil. In addition, the anchovy catch on South America’s west coast has decreased considerably. This is due to the fact that the fish follow the Humboldt stream that passed the Peruvian coast until the 1960s. Recently, the stream has changed its direction and is now passing at a distance more than 350 km from the coast. In modem factory ships, by-catch and the residues from filleting fish are the source material for fish meal and fish oil production. The production of meal is about five times higher than that of fish oil. The dra-
sw S R
Whsk oil
---Ezka
VImln QwIQo(II(y <<<
Fig 3.38. Flow chart of whale oil production.
Animal Fats and Oils
161
matic decrease in Peru's fish oil production as a result of the above-described change of the behavior of the Humboldt stream is striking (Table 3.15). The processing of fish yields three groups of substances, water, fish oil and solids (mainly protein). Fish as a raw material contains only 25-35% dry matter; consequently, substantial amounts of water have to separated. On the high seas, its disposal does not create any difficulty at all; however, for shore-based plants, it may cause problems. The oil content varies from species to species. In typical fat fish, it can reach up to 21% (herring), 18% (sardines) and 16% (pilchard); the average oil content is -3-5% below these values. Fish oil is rich in polyunsaturated fatty acids, the proportion of which depends on the fish species and on where they are caught (Fig. 3.39). Fish oil is usually hardened before use because this modification improves the oil's keepability and reduces the tendency to become rancid. Rancidity is caused by the high degree of unsaturation, i.e., high number of double bonds per fatty acid molecule. Fish oil contains such a large number of fatty acids with equal numbers of carbon atoms but different number of double bonds that these fatty acids are usually not individually shown to characterize the oil. They are listed as CXIn with x being the number of carbon atoms in the chain and n being the average number of hydrogen atoms required to saturate the double bonds or, alternatively, with n indicating the average number of double bonds per fatty acid molecule (as in this book, Table 3.16). However, among the more than 60 different fatty acids identified so far, >80-85% are represented by four groups of fatty acids: C,,:, and C,,:,, Cl,:, and Cls:l, CZal and C22:1,and Cm5, C22:5, and c22:6 (Tucker 1993). In the majority of all triglycerides, the polyenic fatty acids are bound to the 2-position and the monoenic acids to positions 1 and 3. More than 90% of all polyunsaturated fatty acids in fish oils are of the 0-3 type (see also Chapter 1.4). The colder the water, the higher the amount of highly unsaturated fatty acids of the fish. The fact file in the left part of Figure 3.40 shows the average composition of fish oil as recorded in the German Codex. The large number of species TABLE 3.1 5 Production of Fish Oil in the World and Some Selected Countries
Total world (1000 MT) Japan Norway
us. Denmark Iceland Chile Peru USSR Germany Canada
1935
1950
1960
1970
1980
1990
1995
300
300
-
-
700 30 175 85 48 6 12 160 30 12 33
1400 87 180 93 51 7 23 31 1 60 14 27
1500 237 188 142 118 84 83 78 92 18 10
1500 490 115 140 85 105 190 120 95
1400 280 110 130 58 110 190 130 60
-
-
-
-
-
-
-
-
-
-
-
Source; Schuttauf ( 1 940),UNION (1 9791,and F A 0 Production Yearbook (1995).
-
-
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162
Fig. 3.39. Fatty composition of fish body oils.
and the great influence of their environmental conditions, however, make it necessary to appreciate that a wide variation is possible. This is reflected in some extreme cases that are also given in that figure. It must be mentioned that Tucker stated that fish oil analysis is not very representative because it is based largely on single sampling, which does not take into account the environmental effects, the age and the differences between species and subspecies.
3.3.2.1 Fish Oil Production. Figure 3.41 gives a simplified flow chart of fish oil production. The most important facet of fish processing is efficient separation of its three main components, dry substance (protein), oil and water. For good quality, it is essential to keep the contact time to a minimum. Traditional plants use screw presses to separate the liquid (oiywater) from the solid phase. The raw fish material is prepared by an initial cooking step to coagulate the protein and to open up the fat-containing cells. This processing step is essential for the quality of the products and also pasteurizes the fish and inactivates enzymes. Usually, horizontal cookers are used through TABLE 3.1 6
Average Number (n) of Double Bonds per Fatty Acid Molecule in Fish Oils
Herring Pilchard Sardines Menhaden Salmon
-1.0
-1.0
-
1.2-1.7 -1.0 -1.0 1.5-1.7 -1.0
1.5-2.2 1.5-1.7 1.5-1.9 1.6-2.0 2.6-2.8
2.2-3.5 2.0-2.2 2.2-2.6 4.0-5.0 4.2-4.7
3.8-5.5 4.0-4.5 2.3-2.7 3.84.0 6.4-6.8
1.8-2.0 4.3-5.5
-
-
125-160 16G190 160-1 90 155-1 95 140-1 65
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Fish oil Proportion [%I
Falty acid
C 14:O
Myristic Palmitic Paimitoleic Stearic Oleic Linoleic Linolenic Eicosenic Tirnnodonic Cetoleic, (+ erucic) Docosapntaenoic Clupanodonic
C 16:O C 16:l c 18:O c 18:l c 18:2 C 18:3 c 20:l C20:5 C22:l C 22:5 C 2216
0-3 0-11
0-3 0-3
Proportion [%]
Fig. 3.40. Fatty file of fish oil; fatty acid composition.
which the mashed fish is conveyed by screws (Fig. 3.43). The cookers are heated by steam via a jacket. In the event that the raw material is difficult to open up, steam may also be injected directly. The cooker in turn feeds a screw press, which separates liquids and solids. The expelled solids (Graxen with 32-35% dry matter) are milled and fed to a drier; the liquids from the press, the press water, is pumped into a buffer vessel where it is heated with direct steam. A decanter is fed from the buffer, which removes residual solids that are combined with those from the screw press and are jointly TABLE 3.1 7 Fact File of Fish Oil ~
German: Fischol
French: huile de Poisson
Spanish: aceite de pescado
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 40°C; ref. water 2OOC) (nD40) (rng KOH/g oil) (Wijs method) (gkg oil)
0.900-0.922 1.467-1.475 179-1 98 105-1 90 <1 5
Melting point:
<
Solids content at
("CPF)
0132
10150
20168
30186
35/96
(%)
0
0
0
0
0
Solidification point
(US$/MT)
<
rnin
0
rnax
Price index (1995 average compared to average)
1962-1 995
76
300
592
10 years ago 20 years ago 30 years ago 35 years ago
1960-1 969 1970-1979 1980-1989 1990-1995
76 147 133 200
156 364 326 342
237 592 488 525
153% 134% 2 1 1Yo 455%
'
Fats and Oils Handbook
164
Whole fish
&
Fish oil
Fig. 3.41. Simplified flow chart of the whole-fish process.
processed further. The press water is heated in a second buffer vessel by direct steam injection and is fed to a separator,passing a rotary brush strainer. The strainer (Fig. 3.42) guarantees that fibrous residues that have passed the decanter are separated, thus preventing blockages in the feed, disc stack and nozzles. The suspension is fed into the strainer via an inlet (1) where the solids collect on the inside of a cylindrical, perforated strainer insert (2) and are pushed down into the conical sediment holding space (3) by rotating brushes (4). The solids are discharged periodically through the solids outlet (6). A tangentially arranged flushing connection ( 5 ) serves as cleaning device for the strainer. Application of a strainer in the plant is optional; however, it increases the standing time. After reheating and the addition of hot water, the press water is fed into a selfcleaning separator for deoiling, and the separated water is pumped to the evapora-
Fig. 3.42. Rotary brush strainer (courtesy of Westfalia Separator AG, Oelde).
Animal Fats and Oils
165
Fig. 3.43. Conventional fish oil production process (redrawn courtesy of Westfalia Separator AG, Oelde).
tion plant. The turbid oil is heated again and passes a second separator for polishing, i.e., removal of residual water. Modern decanters for preclarification of the press water achieve throughputs of up to 70,000Lh;the residence time is on the order of some seconds only. For the deoiling of press water, self-cleaning separators can process up to 80,000 LJh (Westfalia 1996). The clean oil that leaves the processing line contains -0.1% water, whereas the fat content of the stickwater varies between 0.1 and 0.6% depending on the conditions of the raw material and the thermal treatment. The size of the decanters for press water clarification is determined by the location of the plant. Shore-based plants with a capacity up to 60,OOOLm are pos-
166
Fats
and Oils Handbook
Cooker, breaking up calls. pasteuruing
1
Steam injection
Press water (liquor) I
90-95'C. Steam injection Rotary brush strainer. removing coarse and fibrous solids Separator
i
I
n
-
1
Direct steam
I
Concantrate
<<< Hot water, 9O'C
t
t
>>> EMuent (max 0 6% fatty matter)
Fig. 3.44. Flow chart of fish oil production (as in Fig. 3.43). sible, allowing the processing of press water with up to 25% dry matter. On the high seas, plants on ships achieve only 25% of this throughput. The largest twostage separators have a throughput of 80,000 L h , one-stage separators only 60% of that. On the high seas, throughputs of -10% of these values can be realized.
Animal fats and Oils
167
Fig. 3.45. Fish oil production with the whole-fish process (redrawn courtesy of Westfalia Separator AC, Oelde).
In the so-called full fish process (Fig. 3.45), the plant configuration is changed. After the cooker, the fish passes a decanter, which separates the solids from the liquid phase before the screw press. The liquid from the press is fed back into the product stream before the decanter and passes through it again. The clarified press water is pumped through a rotary brush strainer and is reheated and separated by a separator (Fig. 3.46). The turbid oil and the solids are processed further as illustrated in Figure 3.43. Modern plants are equipped with three phase decanters instead of the layout described above, thus using less equipment. The decanter and the two separators in Figure 3.44 are replaced by one decanter that separates the solids from the liquid and also splits the liquid into an oil and a water phase. This process is limited to solid contents <40% voVvol and to raw materials with oil contents of <15%. The separation sharpness is less well defined than with the previously described processing equipment. Oil contents <0.8% in the stickwater and water contents <0.5% in the oil have to be accepted. The graxen have a humidity of 65-68%, which is equivalent to what can be achieved in the traditional process. With three phase decanters, throughputs of 1.8 M T h in the conventional process and 1.5 MT/h in the full fish process can be achieved. Special processes that achieve very high yields have been developed for lodde (Figs. 3.47 and 3.48). Figure 3.49 shows a fish oil production plant with a selfdischarging separator (Westfalia Separator AG) in the foreground. 3.3.2.2 Breaking Cells Up with Voltage Pulses. After disintegration of the fish, the cells are broken up to improve the oil release. In the traditional process, this is
168
Fats and Oils Handbook
Fig. 3.46. Flow chart of the whole fish process.
--
b
avr
Fig 3.47. Installation for fish meal and fish oil production with three phase decanters (redrawn courtesy of Westfalia Separator AG, Oelde).
169
Animal Fats and Oils
Fish
I
Cooker (A), breaking up calls, pasteurizing
R =Residue SW =Stickwater
I
W W C , steam injection (C)
Heating
Three phase decanters (D)
SW Stickwater <<<
Oil
R
Ij Fish meal
Clean fish oil
Fig. 3.48. Flow chart of fish oil production with three phase decanters.
done mechanically; the cells are cracked by mechanical stress or during heat treatment by thermal expansion of the liquids in the cell. Thermal disintegration inevitably denatures the protein. To avoid protein degradation by high temperatures and to make proteins accessible for further com-
Fig. 3.49. Installation for fish liver oil production (courtesy of Westfalia Separator AG, Oelde).
Fats and Qils Handbook
170
Fig. 3.50. Plant for fish liver oil production (redrawn courtesy of Westfalia Separator AC, Oelde).
mercial use, the Elcrack process was developed by Krupp (no longer available). For this process, cell walls are perforated by low-frequency high-voltage electrical pulses; above a particular field strength, this leads to a perforation of the cell walls. The field strength that has to be applied is inversely proportional to the size of the cells. In fish, muscle (250 pm) and fat cells (150-250 pm) are relatively large; consequently, only low field strengths are required for perforation. In this process, proteins already coagulate at 30°C and can thus be treated gently. Because this process is not applied, no further details are given here. 3.3.3 Fish Liver Oil Fish liver oils are especially rich in vitamins A and D and are therefore high-grade carriers of vitamins. Decanters can separate up to 6 MTh of mashed fish liver. Four rotary brush strainers are needed in the line to keep pace with the decanter. Separators ashore can be fed with up to 5 MTh of mashed liver; on the high seas TABLE 3.1 8 Average Number (n) of Double Bonds per Fatty Acid Molecule in Fish Liver Oils Liver oil
Cod Tuna Halibut Haddock
cl6:n
CI 8:n
C20"
C22:n
Iodine value
1.o-1.2 1.2-1.3 -1 .o -1 .o
1A 1 . 5 1.4-1.5 -1 .o 1.2-1.4
-3.0 2.5-2.8 2.6-2.8 2.8-3.1
3.3-3.5 3.4-3.7 3.5-3.8 3.3-3.7
150-1 75 155-1 80 15C-170 170-1 90
Animal Fats and Oils
171
Raw fish liver I Conveying, dblntegration (A) Buffer tanka Coagulation (B)
J.
Clean liver oil
Fig. 3.51. Flow chart of fish liver oil production (as in Fig. 3.50).
Fig. 3.52. Fatty acid composition of fish liver oils.
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Fats and Oils Handbook
aboard a ship 1.5, M T h is the maximum. The yield of the process shown in Figure 3.50 is 95-96%; the flow chart in Figure 3.51 explains the process. In addition to the large amount of vitamins, fish liver oil is also rich in polyunsaturated fatty acids (Fig. 3.52). The fatty acids are distinguished only by their chain length, not by the number of double bonds. Table 3.16 shows the average number of double bonds for the acids shown in Figure 3.52.
3.4 References Alais, C., (1981) Science du lait, Principes des Techniques Laitieres, SEP-Verlag, Paris. Tetra Laval, uAlfa-Laval, Technical Information: Anhydrous milk fat, a product with wide industrial potential/Butterol-HerstellungNerfahren zur Herstellung wasserfreien Milchfettes,Turnba, Schweden. Anonymous, (1984) Bundesanzeiger, Der Bundesminister der Justiz, Bekanntmachung von weiteren Leitsatzen des deutschen Lebensmittelbuches,26 Mai, 1984. Bornaz, S . , Novak, G., Parmentier, M., (1992) Seasonal and Regional Variation in Triglyceride Composition of French Butterfat, J. Am. Oil Chem. SOC. 69, 1131-1 135. Dahl, O., (1973) Schlachtfette, Fleischforschung und Praxis, Heft 10, Verlag der Rheinhessischen DruckerwerkstiWe,Alzey . Dupjohann, J., and Hemforth, H., (1975) Verfahren zur Verarbeitung von tierischen Rohfetten unter besonderer Beriicksichtigung zenhfugaler Kliir- und Trennvorg2inge, Sonderdmck aus Fette, Seifen Anstrichmittel,Heft 3. Dupjohann, J., and Hemforth, H., (1989) Separatoren, Decanter und Prozeblinien fur die Gewinnung von Speisefett, Broschiire der Westfalia Separator AG, Oelde. Frede, E., Precht, D., Pabst, K., and Philipzcyk, D., (1992) h e r den Einfluss der Menge und technischen Behandlung von Rapssaat im Futter der Kuh auf die Htirteeigenschaften des Milchfetts,Milchwissenschft 8,47. Geigy, Documenta Geigy, edited by von K. Diem and C. Lentner, J.R. Geigy, S.A., Basel, 1968. Hilditch, T.P., and M u d , H.S.(1939) The fat of land crabs (Seychelles Islands), J. Chem. SOC. I d . 58,351-353. Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constitution of Natural Fats, Chapman & Hall, London. Hughes, D., (1993) Production of Animal Fats, in Encyclopaedia of Food Science, Food Technology and Nutrition, Academic Press, London. ISTA Mielke, (1994) Oil World 2012, ISTA Mielke, Hamburg. Kennasha, S . , Kubow, S . , Safari, M., and Reid, A., (1993) Determination of the Positional Distribution of Fatty Acids in Butterfat Triacylglycerols, J. Am Oil C h m SOC. 70, 169-173. Kiermeier, F., and Lechner, E., (1973) Milch und Milcherzeugnisse, Paul Parey Verlag, Berlin. Krupp, Krupp Industrietechnik GmbH, Hamburg, Technische Information: Verwertung sanlagen fur tierische Abfdle/Schneckenpressen Typ EP/ Riihnverksautoklav Typ SSW Fischverarbeitungnach dem Elcrack-Prozess. Opstevdt, J., Urdahl, N., and Pettersen, J., (1990) Fish Oil-An Old Fat Source with New Possibilities, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 250-259, American Oil Chemists’ Society, Champaign IL.
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Mdl,O., Fischer, A., Schmidhofer, T., and Sinell, H.-J., (1988) Handbuch der Lebensmitteltechdogie: Fleisch, Technologie und Hygiene der Gewinnung und Verarbeitung, Verlag Eugen Ulmer, Stuttgart. Precht, D., (1988) Qualitatseinstufung und schnelle Jodzahlbestimmung von Butterfett anhand der Triglyceridanalyse, Z. Lebensmitteluntersuch. Forsch. 187,457-482. Schuttauf, W., and Pischel, U., (1978) Die Margarine in Deutschland in der Welt, Presseabteilung der Union Deutsche Lebensmittelwerke, Hamburg. Sobstad, G., (1990) The Effect of Process Technology on Fat Quality, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 31-36, American Oil Chemists’ Society, Champaign, IL. Sobstad, G., (1990) The Technology of Separation and Purification of Marine Oils, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp, 3 7 4 2 , American Oil Chemists’ Society, Champaign, IL. Smet, Extraction de Smet S.A., Edegem, Technical Information: Extraction of Animal Products . Topel, A., (1976) Chemie und Physik der Milch, VEB Fachbuchverlag, Leipzig. Troeger, K., (1993) Slaughter, in Encyclopaedia of Food Science, Food Technology and Nutrition, Academic Press, London. Tucker, B.W., and Pigott, G.M., (1993) Fish Oils, Composition and Properties, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 1896, Academic Press, London. UNION, 50 Jahre UNION, Werkszeitschrift der UNION Deutsche Lebensmittelwerke, Hamburg, (1979). Veisseyre R., (1975) Technologie du h i t , Verlag La Maison Rustique, Paris. Walstra, P., and Jeuness, R., (1984) Dairy Chemistry and Physics, John Wiley & Sons, New York. Westfalia, 1985 and 1996, Technical Information: Separatoren, Decanter und Prozesslinien fiir die industrielle Fischverarbeitung/Separatoren und Decanter in der Fischindustrie, Technische Information, Westfalia Separator AG, Oelde. Wong, N.P., (ed.), (1988) Fundamentals of Dairy Chemistry, Van Nostrand Reinhold Co., New York.
3.4.1 References for Fatty Acid Composition I
Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constitution of Natural Fats, Chapman and Hall, London. Rudischer, S., (1959) Fachbuch der Margarineindustrie,Fachbuchverlag, Leipzig. Ill IV Wissebach, H., (1969) Pflanzen und Tierfette (ausgenonunen Milchfette). Vorkommen, Gewinnung, Zusammensetzung, Eigenschaften Verwendung; in Handbuch der LebensmittelchemieIV,Springer Verlag, Berlin. XXI Sonntag, N.O.V., (1979) Structure and Composition of Fats and Oils, in Bailey’s Industrial Oil und Fat Products, (Swem, ed.),Interscience Publishers, New York. XXII Baltes, J., (1975) Gewinnung und Verarbeitung von Nahrungsfetfen, Verlag Paul Parey, Berlin.
Chapter 4
Vegetable Fats and Oils
Almost all plants contain fats or oils, mainly in their seeds. The amount varies from very little to as much as 7 0 4 0 % (Table 4.1). For a plant to be suitable for oil production on the scale required today, it must meet the following two criteria: (i) The oil or fat content must reach the minimum for commercially viable exploitation. (ii) The plant must be suitable for high acreage cultivation. The only exceptions are plants that contain oils or fats unique in their composition or with properties that cannot be found elsewhere. The number of oil-bearing plant varieties is quite high. However, only a limited number are exploited and traded worldwide; many are of regional importance only or serve very special purposes. These will be mentioned only briefly. In principle, there are two groups of fats and oils, denominated after their source, namely, pulp oils and seed oils. Within these two groups, further categorization is possible, usually based on the fatty acid composition, on the state of aggregation or on the species or group of species in which the oils occur (Table 4.2). In this chapter, the most important source materials are covered in some detail, giving their history, economic importance, composition and usage. Furthermore. their yearly production and yields are shown. The data are from Schuttauf (1978) and the F A 0 Production Yearbook unless otherwise stated; the references are therefore not repeated in the individual tables. The figures given for the year 1935 are actually averages of 1934-1938, and the data for the year 1950 do not include the Soviet Union. Some 1970 data are from 1969, and the 1935 data for India and Pakistan are summarized under India. TABLE 4.1
Fat Content of Food Edible part of
Fab'oil
Potatoes Lentils, dried Mushrooms, dried Oat flakes Wheat germ Soybeans Coconuts Peanuts, roasted Almonds Walnuts Pecan nuts
(-O/O)
0.1 1 3 6.5 11 20 34 44 54
64 71
174
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Vegetable Fats and Oils
TABLE 4.2 Classification of Oils and Fats Pulp oils: palm oil, olive oil, avocado oil Lauric oils: coconut oil, palm kernel oil, babassu oil, laurel oil, nutmeg oil, dika butter Fats rich in palmitic and stearic acid: cocoa butter, illip6 butter, mowrah butter, shea butter, borneo tallow Seed oils rich in palmitic acid: cottonseed oil, cereal germ oils, corn oil, pumpkin oil Seed oils rich in oleic and linoleic acid: sesame oil, sunflower oil, safflower oil, niger oil, linseed oil, poppy-seed oil, grape-seed oil, walnut oil, fruit-seed oils, berry-seed oils, tea-seed oil Oils of Legurninosae: peanut oil, soybean oil, lupine oil Oils of Cruciferae: rapeseed oil, mustard-seed oil
All information given on the composition of the oil fruit and oilseeds is typical, but not definitive, because of variations resulting from the many subspecies, the progress in plant breeding, the climate, and the location of the fields. The fatty acid composition includes data that were published by three different authors. The light bars show the minimum content mentioned in the respective publication; the dark bars reflect their maximum. This may include rare varieties; consequently, the figures may differ considerably from the averages. The Roman numerals in these fatty acid composition graphs indicate the reference and are explained in Chapter 4.6.2.0. The triglyceride composition of the main oils is also given, using the following abbreviations: C La S L
= capricacid
= lauric acid = stearic acid = linoleic acid
Ca M A Le
= = = =
caprinic acid myristic acid arachic acid linolenic acid
P = palmitic acid 0 = oleic acid Er = erucic acid
Production flow charts illustrate how to extract the main oils and fats; following these there are fact files, with the most important data compiled for the individual oil or fat. Unlike the fatty acid composition graphs mentioned above, these figures are from the Codex Alimenturius or governmental publication and exclusively represent seed varieties that are commonly traded. For different periods of time, average prices, as well as minimum and maximum prices, and price indices are given in the Codex. For those oils that are not commonly traded, the price of April 1990 is given; with these figures, one has to bear in mind that 1990 was a year with a relatively low price level in relation to the historical averages. A more detailed review of oil-bearing plants with a description of subspecies, information on different stages of plant development as well as requirements in
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terms of soil and climate, sensitivity towards pests and diseases, and information on harvesting in different regions is given by Weiss (1983). Godin and Spensley (197 1) collected information on tropical plants. Lennerts (1984) describes the origin of oil plants as well as their utilization and that of their extraction meal. A detailed description of the preparation for extraction can be found in Bernardini (1985). Salunkhe and Desai (1986) discuss the parameters that influence the seeds after harvesting. More general references are given in Chapter 4.6.0.
4.0 Summary New methods of plant breeding enable the cultivation of oil plants with desired properties at an ever increasing rate. The yield depends on the species, but can be improved by appropriate dates of sowing and harvest, irrigation, fertilization, and the right plant density. Most oil plants originate from large-scale agriculture or plantations. Pulp oils are processed close to the plantations because the harvested fruit quickly spoils and cannot be easily transported. Seeds from oils plants are more suitable for transport. In fact, they are better transported than extracted oil, because the oil is protected in the seed. To maintain quality, they must be dried to an adequate moisture that differs from seed to seed. Ventilation and possibly also cooling are necessary for long storage. Because of the different mechanical stability of the different seeds, certain heights of the storage silos must not be exceeded. Origin, yield and fatty acid composition, as well as usability of the meal, differ from seed to seed. These factors determine its price.
4.1. Oil/Fat-Containing Plants With -39 kJ/g (-9 kcal/g), fat has an extremely high caloric value, more than double that of carbohydrates. It is therefore best suited to store energy reserves; metabolic processes involved allow this energy to be released quickly. Plants therefore use oils in their metabolism as well as for energy storage. The high caloric value is related to the high proportion of carbon atoms (7675% of the molecular weight). It has been shown that plants initially store surplus energy as carbohydrates. During seed ripening, these carbohydrates are transformed into triglycerides. This happens according to an individual time pattern for each species and with individual intensity. Trials have been conducted with radioactive-marked linflowers, and they showed that fat is built from the 25th day on. In cotton, this process begins later, but with much higher intensity. As an example for seed oil plants, an investigation of Harris et al. (1978) can be cited; they traced the formation of fatty acids during the ripening of sunflower seed (Fig. 4.1). George and Arumughan (1993) did the same for palm oil. Anthesis of sunflowers is -90 d after sowing, and it can clearly be seen from the figure that each of the four main fatty acids then passes a maximum proportion. This starts with C16:O and shifts to C18:2, which constitutes the highest proportion (-75%) in
177
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Proportion of fatty acid [%]
Proportionof fatty acid [%I
Days after anthesis
Days after anthesis
Fig. 4.1. Fatty acid distribution in developing sunflowerseed and palm fruit (after Harris et al. 1978 and George and Arumughan 1993).
the ripened seed. In other fruit, this development can be completely the opposite. Padua-Ressurection and Bannon (1979) found that unripe coconuts contain -30% oleic acid and 20% linoleic acid -8 mo after anthesis. This proportion decreases to <5%, respectively, to 1% during ripening; the amount of lauric acid compensates for it, rising from 16% to almost 50%. In the ripened seed, the fat offers the plant a maximum of energy content with a minimum of space required because of its high caloric value. During germination, this fat is reconverted into carbohydrates, thus setting free the energy. To start the reaction, H20
carbohydrate
t)fat
high amounts of water are necessary, which is the main influence on the reaction equilibrium. The low water content of the ripening seed shifts the equilibrium in the direction of fat, and the much higher water content of the germinating seed in the direction of sugars. One gram of fat is converted into 2.7 g of carbohydrates. Using this reaction, the plants manage to set free the complete energy stored in the seed within 12 h. The synthesis of fat in the plant is started by the individual synthesis of its two components, glycerol and fatty acids. Glycerol is formed with the help of adenosintriphosphate from the dihydroxiacetonphosphate of the carbohydrate cycle (Diivel). The synthesis of fatty acids has been researched with radioactive marking. Carbon dioxide is attached to acetyl-coenzyme-A with the aid of a biotin CO, complex yielding malonyl-coenzyme-A. After that, another acetyl residue is attached, which via keto acids (splitting off C02) leads to fatty acids. Fatty acid
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coenzyme-A complexes are attached to the glycerol phosphate, from which the triglyceride is formed via several intermediates. In palm fruit until wk 12, the oil makes up for 0.05% of the fresh mesocarp; in wk 16 it has reached 9%, 35% in wk 20, and 44%in wk 24 (George and Arumughan 1993). The oil is stabilized in the seed by a novel class of proteins, the so-called oleosins. These serve as stabilizers of oil-body emulsions especially during seed dehydration and may play a role in facilitating the mobilization of storage oil after seed germination (Murphy 1993). The majority of plants that are used for oil production contain the oil in their seeds. The traditional oil plants are grown in the earth‘s sun belt because high energy, which can be obtained only from sunlight, is needed for the synthesis of fats. Only in recent times have plants from moderate climates been used in larger amounts. To do so, efforts had to be made in plant cultivation, a development that can be characterized as stormy. Figure 1.6 show the production trends of moderate climate plants such as soybeans, sunflower and rape and that of tropical plants such as coconuts and palm fruit. 4.1.1. The Composition of Oil Fruit and Oilseeds
Oils and fats of the main oilseeds are equal in that they have similar fatty acid composition. This is restricted mainly to five fatty acids, namely, myristic, palmitic, stearic, oleic, and linoleic acid, with some allowance for linolenic acid. Often oil fruit and oilseeds contain by-products that have to be separated, for example, lecithin in the case of soybeans. These by-products are used in other ways. The presence of some unwanted by-products (lipids), such as gossypol in cottonseed or erucic acid in traditional rapeseed, caused heavy restrictions to be imposed on the usage of the extraction meal and the oil. Here, the cultivators were and are challenged to grow better varieties. Breeding new varieties can lead to either radical changes, e.g., in the fatty acid spectrum or to minor improvements such as less sensitivity toward climate changes, higher resistance against pests and disease or higher yields. Rapeseed (see Chapter 4.3.5) can serve as a striking example for a total change in a seed’s oil composition. Comparing two sorts of traditional rape with two species of low erucic acid content, a dramatic change can clearly be seen (Fig. 4.2); this change has led to a tremendous increase in rapeseed production. Erucic acid has been bred out of rape with only negligible amounts remaining. Today, rape oil can be used for human consumption in unlimited proportions. In addition to selling the oil, marketing the extraction cake and meal is also essential; thus, restriction can also come from that side. Along with its changed fatty acid composition, rapeseed is also a good example for the changes in the meal composition. It was the cultivation of OO-species that heavily improved the usage of rape’s nonfat portion. This change is of equal importance to the breeding of low-erucic varieties, because the commercial success of the oil milling industry
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Fig. 4.2. Comparison of old HEAR rapeseed fatty acid composition with recent LEAR types (after Weiss 1983).
also depends on the marketability of the meal and new high-oleic species that excited the market place (Table 4.3). From 1992, the Commission of the European Union began to subsidize only rape seed with a content of c20 pmol of glucosinolates/g of air-dried seed. This created political pressure on the West European farmers to grow only the new varieties. TABLE 4.3 Comparison of Novel and Traditional Oilseeds ~
~~
Content in air-dried seed Rape varieties Variety Traditional Double-zero Planned
GIucosi nolates
Sulfur
(mol/g)
(mg/g)
70
4.5 2.0 <1.3
30 <20
New varieties of high oleic oilseeds compared with traditional seeds Oleic acid content (%) Seed Corn Sunflower Safflower Peanut (African) Rapeseed (LEAR)
High oleic seed
Traditional seed
65-80 80-90 75-80 75-80 85-90
33 24 13 59 56
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Fats and Oils H a n d W
TABLE 4.4 Examples for New Cultivations with Noncharacteristic Fatty Acid Composition Approximate fatty acid composition (%)
Soybeans 56 4 21 8 10 traditional 61 7 3 25 4 low palmitic 9 4 49 2 36 low linolenic 20 8 16 48 8 high stearic 27 4 15 45 9 high palmitic 8 3 63 24 2 high oleic 2 70 4 15 2 high oleidlow saturate 4 76 high oleic 8 3 8 3 85437 low linolenic, high oleic 1-2 2 high stearic 18-34 10-14 8-1 o 38-53 7-9 9-1 0 42-48 20-34 high linolenic Sunflower seed traditional 7 5 24 63 0 4 high oleic 6 85 5 0 4 high oleic, 80 4 80 10 0.1 high oleidlow stearic 4 2 88 5 0 Rapeseed (Canola) 2 56 4 traditional 21 10 4 high oleic 2 80 6 6 4 high oleic 2 70 15 3 3 83 4 high oleic 6 4 >90 high oleic Linseed 7 traditional 4 20 17 52 Linola (high linoleic) 6 4 16 72 2 Extreme varieties c12:0>50%; c,2:0 + c1,:o > 60% Rapeseed (Canola) Cocoa butter alternatives Rapeseed (Canola) High content of medium-chainfatty acids (MCFA) Rapeseed (Canola) High content of medium-chaintriglycerides (MCT) Rapeseed (Canola) Soybeans C18:o > 30% C22:1 > 75% Rapeseed (Canola) Ci,:, > 90% (1997), Ci,:, > 95% (2002) Sunflower seed C1&, > 90% Sunflower seed Corn Oil content > 8%
Pioneera Pioneera Pioneera Pioneera Pioneera SVOb DupontC Dupontd Dupontd Dupontd
PimP SVOb PioneeP
Pioneera SVOb Duponte Lembkef
CSlROs Calgeneh Calgeneh Calgeneh Calgeneh Duponte Lembkef Pioneeri SVOb Dupontd
apioneer International Inc.; ~ V specialty O ~rcductsIK.;Slabas 1995;BrogIie I 997;Sader 1993;krauen 1997;Wnited Grain Growers and Haumann 1990; hVoelker 1997;$atu 1997.
The freedom of influence that plant breeders have on the plant’s composition becomes apparent when traditional types are compared with new cultivations (e.g., safflower, Fig. 4.3). Recently, high-oleic varieties of many species have been developed to improve the oil’s oxidative stability, mainly during deep frying. Seed oils with noncharacteristiccompositionhave been bred and will be cultivated soon (Table 4.4).
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Fig. 4.3. Influence of the genotype on the fatty acid composition of safflower seed oil (after Weiss 1983).
Not all varieties bred are interesting for farming. Some serve as intermediates for further breeding; others derive their importance from their genetic composition. Often, the germ of the seed has a different fatty acid composition than the seed (Fedeli er al. 1972). However, this is not used with the exception of corn and other germ oils (see Chapter 4.3.12). In these cases, the seed as such does not contain oil.
4.1.2 The Yield of Oil Fruit To convey an impression of the different external influences on the yield, some publications are referenced. To start with, the timing of sowing can influence the yield (Fig. 4.4). In some cases there are periods or points in time that lead to satisfactory results, followed by dramatic shortfalls in yield when sowing takes place later. Similar findings have been made by the authors regarding plant density. It influences the yield, the size of the seeds, their oil content and thus the oil yield, i.e., the most important criterion of the oil industry (Fig. 4.5). Even with much lower plant densities in arid regions, an influence can be detected. Here, however, it is minor. Higher plant density increases the oil content by 1% (Holt and Campbell 1984). Minimum and maximum yields of the seed (based on the oil content) lie between 1000 and 1600 kg/ton. Following simple rules that are different from plant to plant (e.g., a plant density of -60,000 plantsha for sunflower), the yield can be tremendously increased-in this example, by 60%. Sawan et al. (1993) showed that plant density also has some influence on the fatty acid composition. For cottonseed, he measured a linoleic acid content of 47.83% for fields with
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182
Yield roo0 kglha]
-1
I,
Sunflower (Australia)
I
24
40
32
48
4
12
4
Week of sowlng
Fig. 4.4. Dependency of the yield on the sowing time (after Barkla and Pritchard 1980, Weiss 1967 and 1983, and Mukurasi 1978). 166,000 plants per hectare; 222,000 plants decreased it to 43.64% and with 333,000 plants per hectare, only 41.54% could be reached. The variety also has great influence. This holds true not only for the composition but also for yield. Observing different species of Canadian rape, it becomes apparent that, with the introduction of new varieties with new properties, the proSeed weight [g/lOOO seeds] Yield “000 kg/ha] 10 [
Oil content
[%I
40
20
40
60
80
100
120
140
160
180
Plant density [rounded; ‘000 plants/ha]
Fig. 4.5. Dependency of sunflower seed and oil yield on the plant density (after Barkla and Pritchard 1980).
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183
TABLE 4.5 Yield of Different Rape Varietiesa
Variety
Approved for cultivation
Target Turret oso Zephyr Midas Tower Regent Westar
1966 1970 1968 1971 1973 1974 1978 1982
Type
bushellacre
Yield relative (%)
++ ++
38.4 40.7 37.2 37.8 41.4 36.2 40.1 45.4
100 106 97 98 108 94 104 118
0 0 0 00 00 00
dSource: R6bbelen (1 984). b++, traditional variety (HEAR, high erucic).
duction yield is always lower in the beginning and then increases during further improvement (Table 4.5). In the beginning, the main attention of the breeders is given to the new properties of the seed and only later to yield improvement, while maintaining these new properties. It is striking that in the course of their development, all new sorts reach a higher yield than the traditional ones, thus making their acceptance by farmers much easier. In the example, the novel seeds are represented by low-erucic 0-rape as well as low-erucic low-glucosinolate 00-rape; the traditional species are higherucic high-glucosinolate (marked ++). The kind and quality of soil also influences the yield of oil fruit, as with all other plants. Weiss (1967) compares the yields of Kenyan soybeans grown on different soils. Plants grown on red effusive rock yield 500 kg/ha on average,whereas almost 1100 k g h a could be reached on loamy soil with some granite sand. Fertilization with phosphates increased yield by up to 15%. On the latter soil, fertilization had a more positive effect than on red effusive rock. The geographic location also plays its role. Figure 4.6 shows the influence of night and day temperature difference on the fatty acid composition of sunflowers. Linoleic acid content rises proportionally with temperature differences. The fatty acid composition is important, not because of higher yields, but because of the higher prices obtained for high-linoleic sunflower oil. This high-polyunsaturated fatty acid (PUFA) sunflower oil (for sunflower: high-PUFA = high-linoleic acid > 69%) has a price that is up to 20% higher compared with ordinary sunflower oil. Besides these effects, the influence of fertilization has also been researched intensively. There, the right combination of fertilization and irrigation is the key to success (Fig. 4.7). The amount and composition of the essential trace elements vary from plant to plant, naturally. An overview is also given by Weiss. Oklahoma State University showed the effect of irrigation on the yield of peanuts. Figure 4.8 illustrates that by keeping the plant density and the distance between the rows constant, the yield could be tripled.
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Fig. 4.6. Dependency of the fatty acid composition of sunflower seed oil on the climatic conditions (after Robertson and Russell 1972).
The right time for sowing has been discussed briefly above. However, there is also the right point in time for harvesting. Mazzani and Allievi (1966), using the example of sesame seed, show that the yield can increase steadily until the right moment and then decrease sharply. The method of harvesting depends on the plant Yield [kgiha] 2500
2000
1500
1000
500
0
56
112
168
224
Nitrogen fertilizer [kg/ha] Fig. 4.7. Influence of fertilizers and irrigation on the yield of soybeans (after Henry and MacDonald 1978).
Vegetable Fats and Oils
185
Fig. 4.8. Dependency of plant density and irrigation on the yield of peanuts (after Weiss 1983, Oklahoma State University).
and the location (country). The plant determines to what extent mechanical harvesting is possible. This is mainly for oilseeds that are grown on a large scale. The oil fruit of tropical regions is derived mainly from trees. Because there are no seasons, the same tree carries blossoms, fruit and all stages of development in between. Therefore, harvesting remains predominantly manual. Efforts are being made to mechanize the harvesting process there also. In the next sections of this chapter (4.2 and 4.3), harvesting is described briefly according to species. The exploitation of all means of plant breeding and agricultural techniques has led to a substantial increase in yields, not only for the oilseeds grown in moderate climates (see Chapter 4.2.1), but also for tropical trees. Figure 1.8 shows this clearly for many countries. 4.1.3 Harvest and Harvesting Losses
Because harvesting and storage have a substantial influence on the quality of the oil and on the processing steps to follow, these are also briefly covered here. In 1967, Cramer stated that the production of oilseeds could be 32%higher if only the losses from weeds, pests, and plant diseases could be excluded (Table 4.6). Although these figure are relatively outdated, they still seem generally valid for some parts of the world as the progress in some countries is balanced out by negative development in others; the shift of oil fruit production to the industrialized countries, however, has improved the situation if viewed as a percentage of total production. In addition to these preharvest losses, 30% more is said to be lost as a result of unprofessional or inadequate treatment after harvesting (Booth 1984).
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186
TABLE 4.6 Preharvest Losses in Oil Seed Productiona Cause
Loss (%)
11 10
Insect damage Plant diseases Weeds Total
11 32
Postharvest Losses in Developing Countriesb Country
Oilseed
Kenya Thailand Paraguay
Peanuts Soybeam Soybeans
Loss (Yo)
30 25-68 15
aSource:Cramer (1 967). bSource: National Academy of Science (1978).
Cramer estimated the losses to be -42 MMT,equivalent today to -13 billion US. $. Today’s estimates are losses of -10% of the world’s harvest. Taking into account the increased tonnage, as an absolute amount, this represents -55 MMT of oilseeds and oil fruit with a value of some 17 billion U.S. $. Table 4.6 also gives some loss figures that are taken fmm a study by the National Academy of Science (Postharvest Food Losses in Developing Countries, Washington, DC,1978).Losses caused by harvesting result mainly from not choosing the right time and the right equipment. Meeting both demands is much more difficult in high-acreage cultivation than in artisanal farming. Small areas can be harvested quickly when the right time of seed ripeness has been reached. Vast areas can be cleared only one after the other because of the need for capital-intensive machines that are available only in limited numbers. Harvesting sensitive seeds such as peanuts is more difficult mechanically than harvesting by hand, as is still done in the majority of African countries. Labor ram in industrialized countries make mechanical harvesting of such seeds psible, as they by far outweigh the possible decreases in yield. The slight disadvantages that industrialized farming may have for one or the other seed are overcompensatedby far by the better infrastructurein the postharvesting processes. These are mainly better drying, quicker transportation and better storage conditions. But even under the best possible conditions, harvesting loss cannot be avoided. A study of Ohio State University (Table 4.7) shows that, assuming optimal conditions in soybean harvesting, -3% of the beans will still be lost, compared with an average of 7%. In total, the losses are a sum of adverse preharvest effects such as insect damage, fallen seeds, weeds, broken plants, plant diseases, and rotting plants plus a number of negative influences during harvesting such as the speed of the combindharvester, the mesh size of the sieves, the cutting height, the speed of air during air classification, the revolutionary speed of the cylinder, as well as the threshing itself and the state of the plants.
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Vegetable Fats and Oils
TABLE 4.7 Estimated Harvest Loss (YO) of Soybeans with 3 5 0 0 kgha Yielda Source of loss Shattering
Stubble Lodged Cylinder Cleaning Total
Average operation
Excellent operation
3.5 1.1 1.9 0.4 0.4 7.3
1.3 0.6 0.8 0.0
0.2 2.9
aSource: Ohio State University.
Like preharvesting, postharvesting losses result from a variety of reasons that can be categorized as biological, biochemical and physical. These influences, however, can be well controlled. Biological influences start with the consumption of the seeds by insects, birds and mammals (mainly rodents) and end with spoilage by microorganisms such as yeasts and molds. Processes that proceed in the seeds, such as germination, are worth mentioning. Biochemical processes are mainly oxidation and hydrolysis. These cannot be totally suppressed but are usually caused by incorrect or unfavorable storage conditions (e.g., temperature, moisture). They occur in particular when the seeds have had to withstand improper mechanical stress (e.g., splits, squeezes). In principle, oil fruit yielding pulp oil are much more sensitive than those delivering seed oils. Therefore, the latter are usually processed in the country of destination, whereas pulp oils are exclusively extracted in the country of origin. 4.1.4 Drying of Oilseeds
Oil fruit yielding pulp oils are quickly processed after harvesting in close vicinity to their place of origin. Therefore, only oilseeds are stored. Here, it is very important to lower the water content to a degree that stops all biological and enzymatic activity in the seed. The influence of the water content on the biological activity, represented by its most important parameter, the formation of free fatty acid (FFA), has been researched by many teams. As an example, Figure 4.9 shows this influence on soybeans (Robertson er al. 1985). Table 4.8 gives an indication of the maximum water content that allows for good storage; other authors report slightly different figures. If the moisture is higher than that noted, enormous spoilage of the seeds by microbiological attack is possible. Fungi can multiply explosively, hand in hand with a temperature increase caused by their biological activity. This temperature increase then creates ideal living conditions for thermophilic bacteria; their metabolism adds futher to the temperature increase. Christensen (1%8) observed a container holding nonventilated soybeans with a seed
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Free fatty acids [%I
Free fatty acid [%] 12
12
SOOd
Soybeans
moisture
10
10
8
0
6
6
4
4
/ztUre
seed
2 0 '
0
0
4
0
12
16
20
24
20
0
Storage at 20°C [weeks]
4
0
12
16
20
24
20
Storage at 20°C [weeks]
Fig. 4.9. Free fatty acid formation in soybeans in relation to the seed moisture (after Robertson eta/. 1985).
moisture of 13.2%. After half a year, steady temperature increase could be observed, reaching as high as 93°C after a year. After a hole was made in the container, the temperature increased to 200°C within hours. The beans were totally rotted by a fungal inetion. Although conditions are rarely that drastic, maximum allowable storage time depends clearly on temperature and moisture (Fig. 4.10). Lower moisture represents optimal storage moisture. However, it must always be evaluated whether higher seed quality, which is equivalent to higher oil quality, pays back additional drying cost. Drying itself can be done at the ambient air temperature without any equipment as well as with the aid of dryers. Drying begins with removing outer moisture from all fresh seeds. Then the inner moisture diffuses to the outer parts, where it is TABLE 4.8 Maximum Moisture for Good Storage of Oil Seedsa Oilseed
Maximum water content (%)
Soybeans Copra Cottonseed Safflower seed Linseed Sunflower seed Palm kernels Rapeseed Peanuts aSources: Custafson (1 9761,Patterson (1 989).
13.0 7.0 10.0 11.0 10.5 10.5 8.0 7.0 11.0
Vegetable Fats and Oils Temperature
189
['C]
Fig. 4.10. Allowable storage time for soybeans depending on seed moisture and temDerature (after Spencer 1976).
Allowable storage time [days]
also removed. After some time, an equilibrium between the ambient atmosphere and the seed is reached. This equilibrium depends on the ambient temperature and the relative humidity of the surrounding air (Table 4.9). Because relative humidity is temperature dependent, the relative humidity at 30°C must be 20% higher to yield the same seed moisture compared with 10°C (Fig. 4.11). Detailed information on the energy needed for seed drying is given by Bernardini (1985), for example. Seed hulls and stems may serve as fuel for the dryer if they have no better use. Drying can be carried out in horizontal dryers in which the seed is transported countercurrently to the hot air or in horizontal rotating cylinders. The temperature of the drying air is 250°C. Assuming that the dryer is being fed with air of this temperature and that the seed is to leave the dryer at 70°C, dryers with a cylinder diameter of 1.25 m (4 ft) and 10 m length (30 ft) have a throughput of 50 todd. Doubling the cylinder length and increasing its diameter by 50% increases the throughput to 200 todd. Rotary dryers are best suited for quick drying of very wet material (Fig. 4.12). TABLE 4.9 Seed Moisture in Hygroscopic Equilibrium with the Relative Humidity of the Storagea Seed moisture in equilibrium (% at 25°C) Relative humidity in air
31 .O 43.0 51 .O 62.0 71.2 81.1 93.0 aSources: Ramstadt (1942), Lamour (1 944).
Sunflower seed
Soybeans
6.1 7.4 8.3 10.4 12.2 16.4 25.1
5.2 6.3 6.9 8.1 9.5 11.7 16.9
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Relative humidity [%I 100
20 %
18 % 16 % 14 % 12 % 10 %
9080 -
70 -
Moisture content of soybeans
60 50 40 0
5
10
15
20
25
30
35
40
Temperature ["C]
Fig. 4.1 1. Seed moisture of soybeans depending on relative humidity and temperature. The seed is fed (A) and transported into the drying cylinder (C) by a bucket elevator (B). The seed is collected in (D) and discharged. Hot air delivered by the boiler (E) is blown countercurrently through (C) and is sucked off via (F). Dust is separated and collected in (G) (Fig. 4.13). Besides these dryers, there are other types for drying of less wet seed, such as soybeans (Fig. 4.14). These consist of cells (fed via A) that are passed through by the seed that leaves the dryer at B. During the passage, the seed is exposed to a countercurrent stream of hot air that enters at C with a temperature of 75-95°C. The less moist air from the lower parts
0
2
4
6
8 1 0 1 2 1 4
Length of Cylinder [m]
Fig. 4.12. Temperature during drying of oilseeds (after Bernardini 1985).
Vegetable Fats and Oils
191
A
Fig. 4.1 3. Rotationary seed dryer.
1”1
Fig. 4.14. Vertical seed dryer.
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192
of the dryer (C and D) is recirculated, and the very moist air from E is released to the atmosphere at 3545°C.The recirculated air from D has to pass a filter (F) before being reheated, in order to avoid ignition of dust particles. The energy consumption for drying can be enormous. It depends on the amount of water (W, kg of water per ton of seed) that has to be removed. W can be calculated from the initial water content (Wi) and the water content of the dried seed (Wd) as follows: W = (Wi - Wd) . 10[kg H,O/ton seed]
~4.11
To calculate the energy needed for drying, not only the water to be removed but also the temperature of the air injected and sucked off must be considered. Apart from that, the relative humidity of the drying air plays a role. During drying, the dried seed is heated up and this energy also has to be factored in. To calculate the technical data for dryers, the specific heat of the seeds can be assumed to be 0.5-0.6. Following a calculation by Bernardini (1985), drying a seed with a thermal efficiency of 60%, an air temperature of 20°C when entering the boiler and a temperature of 100°C when feeding the dryer, energy consumption ( E ) can be calculated as follows:
E = 49,960 . W [kT/ton]
r4.21
Drying the seed makes sense only if carried out to a level of seed moisture that improves storage stability and does not deteriorate the seed’s mechanical stability. Furthermore, attention must be paid to the fact that the seed is in equilibrium with the ambient air,a state that depends on the relative humidity of the air in the storage. This equilibrium seed moisture is re-established during storage, independent of the moisture level that the seed had been dried to before (see Fig. 4.10). It is therefore important to maintain adequate storage conditions after drying. 4.1.5 Seed Storage
Despite good drying and good storage conditions, aging of the seed continues, so that storage time cannot be unlimited (Fig. 4.15). During aging, positive effects for oil processing such as decreasing enzyme activity go hand in hand with negative effects such as a tendency toward peroxidation. Measuring a seed’s ability to germinate is a good method of estimating the stress seeds are exposed to during storage. The two are inversely proportional. Many a paper exists that correlates germination ability with storage duration, storage temperature and relative moisture. There is the commercial aspect, namely, that seeds that are well stored and transported have fewer FFA and are less oxidized, thus yielding higher prices. There is also the quality aspect. Damage to the oil cannot be totally removed during processing, and in any case, such oils require much more severe treatment. It is recommended that seeds be well ventilated if stored for a long period of time. A temperature range of 4-1O’C helps because it dramatically slows down all
Vegetable Fats and Oils
193
I
+
lmpairud synthesis of enzymes
Continuous nuclease activity
I
+
+ of major enzymes
Loss of ribosome integrity
Ribo-
I
Impaired protein synthesis
I and DNA polymerase
Failure of synthesis of functional RNA
wed viability
I
and template activity
7 endodesoxyribonucbase --t
Aaina of dw seed
+
nucleus Aging of dry seed
+
&ins of dry seed
+
Fig. 4.15. Biochemical processes during aging of seed (Chavan e t a / . 1984).
biologic aging processes; furthermore, insects can no longer tolerate the living conditions. In addition to maintaining adequate temperature and moisture levels, attention must be paid to mechanical stress. The pressure that is imposed on the seeds depends on the height of the silo (when filled) and the seed’s bulk density. Because there is a limit to mechanical seed stability, losses also occur from this aspect of storage. The volume stream is also very much influenced by bulk density (Table 4.10). Of course, for storage conditions and silo construction, bulk density is not the determining factor in itself but rather in its combination with seed stability, a factor that varies from seed to seed. Often during cultivation of new sorts, higher oil yield results in seeds with a thinner hull, leading to less mechanical stability and thus to oil losses by splits during storage. Seeds can be stored in metal or concrete silos or in halls. Metal silos are well suited for small volumes or as intermediate stores at the farms. The wall strength
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TABLE 4.1 0 Bulk Density of Oilseeds Bulk density (@) Soybeans Cottonseed Cottonseed delintered Cottonseed dehulled Sunflower seed Peanuts, whole Peanut kernels Palm kernels Rapeseed Copra (dep. on size) Safflower seed Linseed Sesame seed Grape seed Castor beans
750-780 280-320 480-580 550-650 4W50 280-330 630-650 56-0 650-720 300-500 700-740 680-720 590-630 470-520 550-590
should be higher than that calculated for normal stability. For a silo 4 m (12 ft) in diameter and 10 m (30 ft) in height, the minimum wall should be 2 mm; among other reasons, this is to prevent heavy deformation in the upper part during (too) quick emptying (Bernardini 1985). Table 4.1 1 gives some storage capacities. For big bulk storage, concrete silos are preferred. The usual layout is square, octagonal or round, usually grouped to improve mechanical stability. Silo height is limited to the mechanical stress that the seed can stand. If pressure (i.e., height) is too great, the lower seed layers can become extremely damaged. Furthermore, there is a danger of bridge formation. Extreme forces that may damage even the silo itself can be set free if such bridges break. Storing soybeans in a silo 50 m (150 ft) in height, for example, puts the lower layer of beans under a pressure of 4 bar. In a round silo 10 m in diameter and 50 m in height, -2700 ton of beans fall down when a bridge formed at a height of 5 m breaks. Spencer (1976) found during his trials that 95% of broken beans consisted of major parts, but that 5% of the splits werepo small that they were removed as “impurities” during seed cleaning. For this reason and for reaTABLE 4.1 l Storage Capacity of Silos Amount of stored seed (tondl0 m height;1000 IbdlO ft height) Silo format (grid 10 m) Round Octagonal Square
Soybeans -600 -700 -850
-85 -95 -120
Sunflower seed -330 -380 -460
-45 -55 -65
Rapeseed -510 -600 -730
-70 -85 -100
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Cracked seed 1% after threshing] VU
30 -
20 -
10-
0 -
I
Fig. 4.16. Relationship between seed moisture and rate of split rapeseed (after Appelqvist and Johansson 1963).
sons of oil quality, splits should thus be avoided. However, it is clear that they cannot be totally avoided, especially not during filling of the silos, when beans crash onto the silo’s floor or onto other beans. The portion of splits does not depend only on the height of the fall, but also on the elasticity of the seed, which is usually associated with its moisture (Fig. 4.16). The results obtained after mechanical stress by threshing can be transferred to storage. Generally, the height of silos should not exceed five times their diameter (Table 4.12). Cottonseed is traditionally stored in large warehouses that allow for storage of up to 1 MMT. Usually a conveyor belt under the roof and central ventilation in the lower part, as well as a tunnel for inspection walks are installed. The storage must be well ventilated because remaining linters act as insulation. Normally there is a cooled wooden floor. Storage of copra, unlike all other seeds, requires special care with the conveying equipment. All other oilseeds are uniform within the same type with very limited differences in size, whereas copra is very irregularly broken, with some small TABLE 4.12 Amount of Broken Beans After Bouncinga Proportion of broken beans (YO) when falling onto Falling height -m (4%) 30 (100) 2 0 ( 60) 10( 30) aSource: Patterson (1 989).
concrete
beans
4.5 2.1 1.1
3.2 1.4
0.7
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196
pieces and others that may be as large as 10 cm. Buildings for copra storage are usually lightweight construction halls to which it is delivered directly by truck. All other seeds are stored on the floor of simple halls or silos of different forms. 4.1.6 Transport of Oilseeds
Transport outside the factories is by truck, rail or ship, where special care has to be taken to ensure dry compartments and to carefully check previous cargos. In the factories and in loading or unloading, various conveying equipment is used. These include belt conveyors (horizontal or maximum 20"slope), screw conveyors (horizontal or steep slope), conveying trough, bucket elevator (vertical), sliding cell or chain conveyors (horizontal and vertical), pneumatic conveyors (horizontal and vertical) and suction air conveyors (horizontal and vertical). Belt conveyors allow fast transportation of a large volume at low energy consumption. Because of their open construction, they are easy to maintain and not very sensitive toward foreign material (e.g., metal pieces, stones). However, they are also open for further contamination. The belt runs via two or three V-shaped rolls that form an angle of 10-30". It is driven on the one side and tightened on the other. Slopes of >20" are almost impossible to engineer (Figs. 4.17 and 4.18). Screw conveyors (S) have the advantage of transporting the seed in a closed sys tem if the screw runs in a pipe. It can also run in a U-shaped trough (trough conveyor; T). If the pipe is built as a sieve, they are called sieve conveyors (Fig. 4.19). These enable the separation of small foreign particles and dust from the seed during transport without extra effort. Screw conveyors are designed to swivel and allow for transport even at steep angles (if built into a pipe, even vertical transport). Their one disadvantage is their straight construction, which makes it impossible to pass obstacles without interruption. The other is the high shear stress that can lead to unwanted damage of the seed. The conveying capacity (C,) can be calculated as follows: Cs= ( & . R . r . S . 6 . X . 60. ~)/4000(to&)
[4.31 where d (m) is the diameter of the screw (pipe), x (5%) is the degree of filling, s (m) is the slope of the helix, r (min-1) is the rotational speed of the screw, 6 is the bulk density, and v is the loss factor if not conveyed horizontally (8 -15' + v = 0.7; 8 -25" + v = 0.5). The slope of the screws may differ in the same screw over its length. The slope close to the feeding point determines the amount conveyed. Figure 4.20 shows the conveying capacity of different types of screw conveyors for a filling factor of 33%. For extraction meal, a filling factor of 30% is common; for oilseeds, 45% can be assumed. Free-flowing materials can have up to 40% higher throughput; nonfree-flowing goods may result in 20%less. Pipe screw conveyors (P) have a 2-2.5 times higher capacity than trough screw conveyors (T), given the same screw diameter and revolution speed. For vertical transport, capacity decreases significantly. To allow the same capacity as for horizontal screw conveyors, transporting vertically (V), the revolutionary speed of the screw has to be five times higher.
(a)
Vegetable Fats and Oils 197
Fats and Oils Handbook
198
Belt conveyor -A)
v=1.3
w=600
"B)
v=1.2
w-500
+C)
v=1.2
w=450
*D)
v=1.2
w=400
*E)
v=1.0
w=350
+F)
v=1.0
w=300
v = belt velocity [m/sec] w = belt width [mm]
Fig. 4.18.
Energy consumption of belt conveyors and quantity conveyed (after Bernardini 1985).
The energy consumption (E,) for the conveyor can be calculated as follows:
E, = L . C, (f k sin 0)/367
(kW)
i4.41
where L (m) is the total length of conveyor, C, (ton/h) is the conveying capacity for screw conveyors (see Equation. [4.3]),fis the product specific factor (f= 2 for oilseeds and extraction meals) and 0 (") is the slope. As can be seen from the equation, the energy consumption increases linearly with the length of the conveyor and the amount conveyed. The slope 0 adds a nonlinear part to the equation. For vertical transport, bucket elevators are more suitable. They consist of a chain of buckets that can hold the conveyed product. Close to the top, these buckets are turned upside down for discharge (Fig. 4.21). The amount conveyed for such equipment can be calculated as follows:
i
E
Fig. 4.1 9. Screw conveyor.
Vegetable Fats and Oils
199
1OOO.D where C, (tonih) is the conveying capacity for bucket elevators, B (L)is the content of the individual bucket, v ( d s ) is the velocity of the bucket, x (%) is the degree of filling, 6 is the bulk density and d (mm) is the distance between the buckets. The degree of filling is reduced with increasing bucket speed; it increases with the slope of the conveyor. German Industrial Standards (DIN) define the bucket size and the corresponding quantities conveyed for granular products (DIN 15232) and for oilseed meals (DIN 15231; Fig. 4.22). The energy consumed (E,) can be calculated according to Equation [4.6]; energy to be installed (Ei) is expressed by [4.7]. Equation
(a)
where g (m/s*) is the acceleration due to gravity, h (m) is the conveying height, Ps (kW) is the conveying power input, PN (kW) is the no load power input and o is the efficiency. Redler conveyors consist of open rectangular or square boxes that slide on a fixed belt and transport the goods by dragging them along. They are able to cope
\
500-
R = Revolutionary speed (min-’)
D = Diameter of the screw (mm)
T
Screw conveyors
4001 300
Trough conveyor (T)
Vertical conveyor
N’
200
.
100
0 R= D(T)= D(P)=
20
1250 975
40 630 630475
240 80 100 200 250 290 165 385 290
80 315
280
215
320 =DO
Fig. 4.20. Quantity conveyed by screw conveyors depending on screw diameter and revolutionary speed.
200
Fats and Oils Handbook
Fig. 4.21. Bucket conveyor.
Fig. 4.22. Quantity conveyed by bucket conveyors at 90% filling.
Vegetable Fats and Oils
201
with steep slopes and to convey large bulk. Energy cost is relatively high as a result of the high frictional forces that have to be overcome. In contrast to the conveyors described above, it is possible to heat or cool the conveyed goods. This principle is also applied in solvent extraction (see Chapter 5.2.3.4.3). A Redler with a chain height of 25 cm and cells of 30 x 40 cm has a throughput of -60 m3/h if running at 0.2 d s (see also Fig. 4.23). Chain conveyors work similarly. Instead of a cell, runners, wings, scrapers or U-shaped track links are dragged over the belt, dragging along the goods. If the distance between the links is narrow, chain conveyors can manage almost all transitions from horizontal to angled operation. Figure 4.24 shows the amount conveyed for a bulk density of 600 g/L and a speed of 0.1 d s . Pneumatic conveyors allow transport of goods in whatever direction wanted. This flexibility must be paid for by an energy consumption that is four to five times greater than with the other conveying systems. However, the goods are transported more gently than with most mechanical means. A problem is caused by the dust, so that filters have to be installed. Air speed required is -20 d s ; the ratio of air to goods conveyed is 1.2.
-
4.1.7 Storage and Transport of Oils
In contrast to almost all other oils that are extracted in factories located close to the consumer, palm oil and its fractions are processed in the neighborhood of the plantations and then shipped. Consequently, other precautions have to be taken to safeguard quality. PORul (Palm Oil Research Institute of Malaysia, 1985) has therefore published recommendations that guarantee maintenance of optimum quality; some of them were derived from the Codex Alimentarius or later found their way Quantity conveyed [rn3/h] I "
h = 220 rnrn
60 -
Sliding cell conveyor
50 v = 0,2 (rn/sec)
40 -
h = 175 mrn
30 -
h = 150 rnrn
20 10-
0
Fats and Oils Handbook
2 02
Quantity conveyed at 0.6 kg/dm3 bulk density
speed
800
[m/secl 1 .o
Chain conveyor 600 -
0.8 0.6
400 -
0.4
200
140
0.2
240
440
340
540
640
Chain width [mm] Fig. 4.24. Quantity conveyed by Redler conveyors depending on their size.
into that codex. Examples for contracts and international trading terms can be found in Ludwicak (1990), Fleming (1990) and Backlog (1990), for example, and from the International Association of Seed Crushers (Anonymous 1980). Following these recommendations, ship tanks that are not stainless steel should be coated with an appropriate coating. Copper, brass and bronze should not be present. The tanks must be heatable; however, to avoid local overheating, heating should not be faster than 5'Ch if agitation is not possible. To ensure good loading and unloading, the temperatures given in Table 4.13 should be guaranteed. TABLE 4.13
Recommended (Un-)LoadingTemperatures for Oils and Fat@ ("C)
aSource: Ccdex Alimentarius (1 992). %fees above slip point.
(OF)
Max.
Min.
Max.
55 70 35 35 35 25 25 ambient 25 25 30 55 60 15b lob
112 150 86 86 86 68 68
131 158 95 95 95 77 77 77 86 140 2 76
Min. Palm oil Palm stearin Palm olein Palm kernel oil Coconut oil Cottonseed oil Peanut oil Other salad oils Fish oil Tallow Hardened oils
Temmrature
50 60 30 30 30 20 20
77 131 186
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203
TABLE 4.14 Recommended Storage Temperatures for Oils and Fat9 ("C)
Palm oil Palm stearin (hard) Palm olein Palm kernel oil Coconut oil Seed oils Tallow
Temperature
Min.
Max.
32 40 25 27 27
40 45 30 32 32 ambient
44
49
(OF)
Min.
Max.
90 104 104 113 77 86 81 90 90 81 ambient 111 120
aSource: Codex A h e n m i u s (1992).
Such temperature recommendations are also given for storage to prevent crystallization, which causes inhomogenity (Table 4.14). Reliable producers ask for a record of previous freight from the transportation companies to avoid contamination; they can then decide whether the ship or truck is suitable for the transport of seeds or oils. The method of transport depends mainly on the fat or oil transported. Crude oils will be refined after transport; thus, conditions do not have to be well controlled. They can be transported and stored in large tanks. The more refining an oil has undergone, the less one has the ability to compensate for damage during storage. Such oils are therefore transported and stored in quantities that can be used up within days. Fully refined oils may require transport and storage under nitrogen. In this case, it can be more important to protect the oil film on the walls of an empty vessel from oxidation (large surface exposed to oxygen from the air) rather than saturating the headspace of a full tank with nitrogen. For transport tankships, rail tankers and trucks can be used. The further the oil has been processed, the more road transport is chosen, because this is usually much faster, with less aging of the product. The tanks themselves can be made from mild steel or stainless steel. The kind of vessel chosen depends on the oil and the pretreatment. Mild steel containers should be flushed with hot oil several times before their first usage. This creates an oil film on the surface that mildly polymerizes and forms a sort of coating, protecting the oil from iron intake, which catalyzes autoxidation. 4.1.8 Usage of the Nonfat Part of Seeds
Besides the fats and oils that are delivered by the oil fruit, special attention has to be given to the use of their nonfat part. On the one hand, this means dealing with those parts that are not suited for human consumption such as shells of babassu nuts or peanuts or the stems of palm fruit. To a greater extent, this means marketing expeller cakes and extraction meals that remain after separating the oil. The
Fats and Oils Handbook
2 04
commercial success of an oil mill is closely linked to the ability to sell these meals at reasonable prices. This is more evident if one has in mind that the nonfat part usually accounts for >50% of the seed weight, and even as much as 80% for the dominant seed soybeans. As early as the year 1700, the idea arose to use the oil cake that had formerly been thrown away as feed. From 1900 onward, real research on its usage has been started and has answered the question of which oil cakes are suitable for which animals. The use of the meal is restricted in many cases because it contains natural components that cannot be fed to certain groups of animals, or at least only in limited amounts. Often these restricting components can be removed or inactivated by additional meal treatment. In some cases, new species have been bred to improve the usage of the meal. In the following, some examples are given to illustrate common uses. A broad and detailed overview can be found in Lennerts (1984). Most restrictions in meal usage are covered briefly in the section describing the respective oil plant. In case of feed-stuff for livestock, it is very important that the meal contain some components, usually special amino acids, in sufficient quantities and that these also be easily accessible to the animal. This means that digestibility must be ensured. A key quality factor for a feed protein is the concentration of available lysine (Table 4.15). TABLE 4.15 Amino Acids in Soy Protein from Dehulled and Nondehulled Seed, Soybean Meal and Rapeseed MeaP Soy protein Proportion (%)
Dehulled
Nondehulled
Soybean meal
Alanine Arginine Aspartic acid Cysteine Glutamic acid Glycine Histidine lsoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tryptophan Tyrosine Valine
4.6 6.9 11.5 1.5 19.2 4.4 2.6 4.7 7.7 6.4 1.5 4.8 5.1 5.6 4.0 1.3 3.3 4.8
4.0 7.0 11.1 0.9 16.3 3.9 2.4 4.4 7.2 5.8 1.2 4.6 4.7 4.9 3.7 1.3 3.3 4.6
1.9 2.9
aSource:DLC, from Lennerts (1985) and Clandinin (1978).
0.3 8.1 2.1 1.1 2.1 3.4 2.8 0.6 2.2 2.3 2.3 1.7 0.5 1.3 2.3
Rapeseed meal 1.6-1.7 2.1-2.2 2.5-3.1 0.2-0.5 6.4 1.a-i.g 1.o 1.3-1.5 2.5-2.7 2.1 0.7 1.4-1.5 2.3-2.7 1.6-1.7 1.6-1.7 0.4 0.8-0.9 1.&1.9
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TABLE 4.16 Digestibility of Soy Meala ~~
~
Digestibility of soy meal components (%) Non-heat treated
Heat treated
52 68 44
63 82 52
Dry matter Crude protein N-free extract
aSource: Niveld and Terpstra, from Lennerts (1985).
Digestibility can be increased by heat treatment (toasting, see Chapter 5.4). In the case of soybeans, it can be improved by 20% (Table 4.16). However, this is less than the difference in digestibility for different sorts of livestock and poultry. Extraction meal from dehulled seed contains fewer trace elements and fewer vitamins than that from nondehulled seed. However, that plays a minor role compared with the protein portion that is increased by dehulling (Table 4.17). The meal is further processed for feed-stuff, which is usually regulated by law. As an example, the German regulation for different sorts of sunflower meal is given in Table 4.18. The composition of the meal is given in the respective sections dealing with the individual oil plants.
TABLE 4.17 Trace Elements and Vitamins of Soy Meala Proportion (ppm of dry matter)
Proportion (ppm of dry matter)
Trace element
Nondehulled
Dehulled
Vitamins
Nondehulled
Iron Manganese Zinc Copper Molybdenum Iodine Cobalt Fluorine Chromium Nickel Barium Aluminum Boron
130.0 27.0 55.0 15.5 3.6 0.5 0.25 4.7 1.o 16.0 6.7 32.0
122.0 25.0 48.0 14.0 3.8
Vitamin E
1.2 6.7 3.2 4.8 27.0 16.0 0.6 2800
-
0.08 2.1
36.0
aSource: Kling and Wohlbier (1983) with permission
Bl BZ Bb
Nicotinic acid Pantothenic acid Folic acid Choline
Dehulled 1.3
-
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206
TABLE 4.1 8 Standardized Sunflower Meals According to German Regulations Standard (% of dry matter) Water Sunflower cake Dehulled Partially dehulled Nondehulled Sunflower meal Dehulled Partially dehulled Nondehulled Sunflower meal, fat added Dehulled Partially dehulled Nondehulled
Fat
Fiber 46
4 3 4 3 4 3
<27.5 <30
4 3 4 3
>4
4 3
>4
<13
>4
<27.5 <30
<13 4 3 4 3
>4 >4 >4
46
<27.5 <30
Proportion in standard types (%) Water
Fat
>3 8 >5 >2 9 >5 no standard type
>40 >30
Fiber
<2 1
<22
no standard type no standard type no standard type no standard type
4.2 Pulp Oils Pulp oils occur finely dispersed in the fruit's endosperm, which has a very high water content. They require special treatment, preferably immediately after harvesting. Any mechanical stress that leads to damage of the cells, but also aging as such, initiates enzymic reactions that lead to fat splitting or other spoilage. This means that pulp oils are usually extracted in close proximity to the location of origin, which usually is smaller decentralized oils mills near the plantations. In addition to the two main contributors (palm oil and olive oil), there is a third that is produced in small quantities, namely, avocado oil. This oil is very edible; however, because of its high price, low tonnage and high image, it is used mainly in cosmetics. 4.2.1 Palm Oil ----4.2.7.7 Betany and History of the O i l Palm. In Europe, the- P
r Gil Eannes in 1434 first reported about oil palms (Elueis guineensis). Today, they flourish mainly in the western part of Africa, Indonesia and Malaysia, recently also in Brazil and more recently in Colombia. Oil palms grow to 20 m in height and grow best at temperatures of 24-27'C. They require a humid climate. Cultivated oil palms carry fruit from their fourth year onward. Palm fruit can then be harvested for 40-50 y with the maximum yield being reached after 12 y (Fig. 4.25). In plantations they are replaced after -25 y. The palm is the oil producer with the highest yield; each tree can produce almost 20 MT of fruit bunches per year. In addition to the trees from plantations, wild palm trees are also used as a source for palm fruit. However, these carry fruit only after 10 y and at lower yields.
Vegetable Fats and Oils
207
Fig. 4.25. Oil palm and oil fruit.
New cultivations stay -30% smaller to allow for easier harvesting. Oil palms are one of the best examples of the cloning technique in modern agriculture (Unilever 1985). For cloning, samples of the root of a high-yielding robust oil palm are taken. They are placed in a special nutrient medium where the cells of the root begin to multiply. The mass formed is known as the callus. From the callus, tiny oil plantlets begin to grow. These plantlets are transferred to different culture media at various stages of growth to provide them with the nutrients they need. While still in test tubes, they are kept in controlled environments. Later, they are transplanted into polybags and shipped to the plantations. Because these piants may be grown from many different palm species (Jones 1984), new methods of breeding arise (Tan et al. 1985).However, cloning is still the exception.
208
Fats and Oils Handbook
Pollination of the palms had been done manually up to the 1970s using especially designed bellows attached to a long pipe to blow pollen onto female flowers. Oil palms flower for 3-8 d and only one third of the blossoms bear fruit. After importation of oil palms to Malaysia, New Guinea and the Solomon Islands, the palms bore fruit only when manually dusted. In 1977, an entomologist from the Commonwealth Institute of Biological Control was put in charge by Unilever to investigate the case. He discovered that, contrary to long held belief, the plants were not wind pollinated, but in fact insects did the job in Africa, their country of origin. In particular weevils of the genus Elaeidobius (see Fig. 4.26) had developed a symbiotic relationship with the palm and were the principal agents involved. These were not present in South East Asia. In some areas, a local insect (Thrips hawaiiensis) had taken over the job. However, it was much less effective. Only after the influence of the beetle on the fauna of the “importing” countries had been carefully investigated and found not to be at all harmful to the ecological equilibrium of the host country were Elaedobius weevils brought to Malaysia in 1981. The yield of the palms immediately increased by up to 50%. New plantations added to the trend, and the supply of palm oil from South East Asia has risen substantially over recent years (see also Patzaris 1985 and 1986). A large part of the supply, especially the olein from fractionation (see Chapter 6.2.3.4) is consumed in the region as salad oil. 4.2.7.2 Composition and Properties of Palm Oil. African oil palm contains 40% pulp, the Asian varieties up to 65%. The pulp itself contains -40% oil (Fig. 4.27).
Fig. 4.26. Elaeidobius kamerunicus.
Vegetable Fats and Oils
2 09
Poor keepability of the fruit leads to immediate processing of the pulp close to the plantation; palm kernels, however, can be stored longer and transported without difficulties. Palm oil is rich in palmitic and oleic acid, adding up to almost 80% of the fatty acids. In some oils, up to 0.8% palmitoleic and linoleic, as well as 1.1% arachic acid, may be present (Fig. 4.28). Special coverage of African palm oil can be found in Congopalm (X) and of Malaysian palm oil in Berger (XV). Because of its composition, palm oil consists of two main fractions that are liquid and solid, respectively, at moderate ambient temperature. This makes it especially suitable for the above-mentioned fractionation (see Chapter 6.2). The triglycerides present in palm oil and their proportion underline these properties (Fig. 4.29). 4.2.7.3 Economic Importance of Palm Oil. Palm oil supply has increased sharply over the last two decades (Table 4.19) because of the vast increase in pro-
Oil palm fruit
Fig. 4.27. Composition of palm fruit.
Fats and Oils Handbook
21 0
Fig. 4.28. Main fatty acid composition of palm oil.
Palm dl TrigC=*
typs
PPP PMP, MPP. PPS, PSP sss, SPS, PSS
-
MOP POP POS
sos PPO SPO, PSO,
sso-
Po0 SOO, MOO PLP MLP, SLP, PPL SPL, SSL, SLS
-
OOO MOL, POL. SOL MLO, PLO, SLO
-
OOL, OLO, P U others Proportkn [% Wrn]
Fig. 4.29. Triglyceride composition of palm oil (after Coleman 1961).
21 1
Vegetable Fats and Oils
TABLE 4.19 Palm Oil Production Palm oil (MMT)
1935
1950
1960
1970
1980
1990
1993
1994
Total world Nigeria Indonesia Malaysia
0.65 0.25a 0.30 0.05
0.90 0.28a 0.33 0.11
1.10 0.42 0.14 0.09
1.75 0.48 0.20 0.62
5.00 0.67 0.72 2.53
11.10 0.90 1.94 6.09
14.40 0.83 3.42 7.40
14.66
1995
15.60 0.84 0.87 4.10 4.30 7.22 7.81
aBritish West Africa.
duction in South East Asia, mainly Malaysia. The yield there increased from 2.8 toniha in 1878 to 3.4 ton in 1933, 4.5 ton in 1969 and up to 5.7 tonha in 1978 (Berger 1983). Today it is -4 t o h a on a worldwide basis with an additional 0.5 tons of palm kernel oil. Other areas that have a climate suitable for palm cultivation are trying hard to become self-sufficient or to extend their production for export. In Asia, this holds true mainly for the Philippines, and in South America, for Brazil and Colombia. Prices have dropped as a result of high stocks. Palm oil stocks of Malaysia had been estimated to reach 1 MMT in 1988 and more than that in 1989. In 1992, they were said to have decreased to 660,OOOtons with an ending stock in 1993 of -1.2 MMT. The production is expected to more than double from 1995 to the year 2020 with a production of -35 MMT. 4.2.7.4 Harvest of Palm Fruit and Oil Exfraction. Usually palm fruit bunches are harvested when five to Seven individual fruits have fallen from the bunch (TPI1971); however, this time point represents a compromise. Although some parts of the fruit are not yet ripe, the fruit has to be cut because others might become overripe. At this stage, they quickly begin to develop FFA, which causes a deterioration in oil quality. Bafor (1986) describes all of the p e e d i n g s during ripening. The fruit bunches are cut with long knives (old varieties) or with short knives or mechanically for the recent species. They have a weight of up to 40 kg and along with the pulp contain up to 2000 red brown oval nuts 3-5 cm in length and 2.5 cm in diameter. These are further processed to palm kernel oil, a lauric seed oil (see Chapter 4.3.8).One thousand kernels weigh -8 kg. The processing scheme for palm oil is given in Figure 4.30.
4.2.1.5 Fact File of Palm Oil. The fact file (Figs. 4.31 and 4.32 and Table 4.20) shows the physical data of palm oil, its composition and the development of world market prices. As for olive oil, virgin palm oils of the fmt pressing also exist and are only of local importance. More detailed information on palm oil is given in the references section. Palm oil is very well researched because marketing organizations exist that promote its use. Reports on its potential use have been published in recent years by Beny and Awang (1983), Ong (1984), Kheiri (1985), Traitler and Dieffenbacher (1985, cocoa butter substitutes), Okawachi et al. (1985, fat specialities) and Berger (1985 and 1986).In 1990, a palm oil congress was held in Hamburg; its proceedings also contain valuable infoimation.
Fats and Oils Handbook
212 Palm. fruit
(Bunchar) 2 . 5 3 bar, 130135'C, 50-75 min Autoclam (1.5 bb 20 t Wnt.nt); a p r d t y por Ilne Up I0 10 vh Inr&rtbn of lpolytic enrym; operho of calls
FNB l o o r e d up lo W.5% if Itrrllization b well dom Robthgdrwn WW b w ; cspdtypof U r n up to 32 vh
=.a cooking
9C-lOo'C, 20-30min 3 5 m' Content; (up lo 10 vh of who* bunchar)
-
S a m presses (up to 20 vh); maidurl oil < 7%, broken kernels < 5%
Vibraling rusen (Seprratlon of major bNbn material) t
t
CIPriRcslbn, wrrhing
+
Maling lo cn.W C
Nub
+
(W 4.3.8)
Fbn
a 8
Ciarificltmn. wrhw
r
Sewraton I-+
i Wno
>>> f FNB
~8-
Water < 6.1%
a
I
Burning material or brlngingbeck to p*ntotion aa hrtl(ber
Crude palm oil
Fig. 4.30. Flow chart of palm oil production.
I
Palm oil
IP r o P o [%I~ ~
Fatty add
MyMtic Palrnitii Palmitolek Stearic Oleic Linokic Linobnic Arachic
C 14:O C 16:O C 16:l C 18:O C 18:l C 18:2 C 18:3 C2O:O
< 0.4 2.0 47.0 0.6 3.5 6.0 36.0 -44.0 6.5 12.0 c 0.5 c 1.0
0.5 41.0
-
-
Proportion [%]
Fig. 4.31. Fact file of palm oil (fatty acid composition). 4.2.2 Olive Oil
4.2.2.1 Botany and History of Olives. Olive trees occur mainly around the Mediterranean where they have been established for centuries. Most likely the olive originated in Asia Minor. In the Bible alone, olives are mentioned more than 200
Vegetable Fats and Oils
21 3
Fig. 4.32. World market price development of palm oil.
times. For example, a dove brought Noah a branch of an olive tree as a divine sign that the flood was over. Most likely olives found their way from Asia Minor to Europe around 1700 B.c., approximately the time when Athens was founded. The Greek legislation of Solon, as recorded by Plutarch, fined anybody who cut more than two olive trees per year and per plantation; they recognized the importance of the trees. Around the year 700 B.C., olives came to today’s Italy, and by 200 B.C. they had spread over the whole of the Roman Empire. From Spain, at that time a Roman province, the oil reached as far as the British Islands in the second century. After that, it was almost completely consumed by the citizens of Rome and free trade became forbidden. TABLE 4.20 Fact File of Palm Oil German: Palmol
French: huile de palme
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 50°C; ref. water 20°C) (nD40) (mg KOH/g oil) (Wijs method) (g/Kg oil)
Melting point Solids content at
0.891-0.899 1.449-1.455 190-209 50-55 <12
Solidification point
30-37OC ( O U T )
Spanish: aceite de palma
27-43T
10/50
20/68
30/86
35/95
50
27
8.5
4.5
(YO)
World market price (ex Sumatra)
Price index (1 995 average compared to average) 1 2 6% 10 years ago 20 years ago 148% 235% 30 years ago
(U.S. $/MT)
min
0
rnax
1962-1 994
144
393
937
1962-1 969 197CL1979 198C-1989 1990-1995
144 177 199 275
222 436 472 416
288 807 937 740
214
Fats and Oils Handbook
Fig. 4.33. Olive branches and fruit.
Olive trees need an average yearly temperature of 15-20°C. The evergreen trees are up to 20 m high and yield up to 55 kg of olives per tree; they can reach ages of over 2000 y (Fig. 4.33). 4.2.2.2 Composition and Properties of Olives. Taking the whole olive including its kernel, the oil content is -30%, on average; however, the yield after oil extraction by pressing is only a little above 20%; the kernel contains -12% oil with a composition that is similar to that of the pulp oil (Fig. 4.34). The pulp oil can contain up to 80% oleic acid. Besides the main fatty acids (Fig. 4.35), 0.2% lauric acid, up to 1.3% arachic acid, 2.5% palmitoleic acid and 0.1-1.7% myristic acid occur. The proportion of polyunsaturated fatty acids is low. The high image of olive oil is also based on its extraction technique that permits it to be left it in a so-
Fig. 4.34. Composition of olives.
Vegetable Fats and Oils
21 5
Fig. 4.35. Main fatty acid composition of olive oil.
called virgin state. The fatty acid composition varies greatly depending on the region of origin (Gracian et al. 1968, Fig. 4.36). The proportions of various triglycerides (Fig. 4.37) present the profile that can be expected from the fatty acid composition. The paramount triglyceride is the single acid triolein; oleic acid is present in 97% of all triglycerides. 4.2.2.3 Economic Importance of Olive Oil. The economic importance of olive oil is increasing in Europe, as demand grows because of the promotional activities of the European Union Commission as well as because of the oil’s good image.
Fig. 4.36. Main fatty acid composition of olive depending on the country of origin.
Fats and Oils Handbook
21 6 Olive oil T-(vp PPO
Pso ohur Po0
so0 PPca
dhn OOO pa. SOL pooo 0th.n OQ
RL POL. c4ml
OU OOL.
omrn opwr
-Iwm1
Fig. 4.37. Triglyceride composition of olive oil (after Descargues and Bezard 1981).
The amounts available differ greatly from year to year. In 1987/88, a record harvest delivered 1.9 MMT of oil, whereas a year later, the yield was only 1.6 MMT (Table 4.21). Estimates differ on how much of the crop is extracted for oil. Raina (1993) estimates 93%; other sources suggest 85%. The amount of oil is always -20% of the tonnage of harvested fruit. The Mediterranean countries continue to be the main source of olives. However, other countries have attempted to grow the fruit. Brazil’s first mentionable crop was in 1990, but still in negligible quantities. 4.2.2.4 Harvesting Olives and Oil Extraction. Olives should be harvested shortly before complete ripening, which is indicated by blackening of the fruit (Table 4.22). TABLE 4.21 Olive and Olive Oil Production as Well as Number of Trees (mil1ions)d
Total world, olives Italy Greece Spain Portugal Tunisia Total world, olive oil (MMT)
Trees
1935
1950
1960
1970
1980
1990
1994 1995
800 181 118 189 50 56
4.5 1.3 0.5 1.8 0.4
4.8 1.2 0.5 1.6 0.4
7.1 2.1 0.4 2.4 0.3
7.2 2.4 1.0 1.8 0.3
9.2 1.6 1.3 3.0 0.25 0.33
11.3 2.6 1.9
-
8.0 3.0 1.5 2.0 0.3 0.5
1.0
1.1
1.38
1.63
1.75
1.77
-
-
-
aApproximately90% used for Oil extraction; extraction oil equivalent -25%.
2.7 0.2 0.6 1.96
9.3 3.O 1.6 1.6 0.2 0.6 1.59 -
Vegetable Fats and Oils
217
TABLE 4.22 O l i v e Harvesting Periods
France Greece Italy Portugal Spain Turkey
Jan
Feb
Mar
H H
H
H
H
H
Apr
May
June July Aug
H H
Sept
H H H H
Oct Nov Dec H H H H H
H H H H H
H H
Traditionally, the three following methods are used: Brucatura, picking the olives from the tree; Raccattattura, collecting the fallen olives; and Scuotitura, shaking the tree (for example, mechanically) and collecting the fallen fruit. During harvesting, the olives are usually exposed to mechanical stress. This leads to damage of the cells and initiates fat spoilage. This holds especially true for the raccattattura olives because they fall from the tree when they are ripe and soft. They are easily damaged by the lightest pressure. This is the reason for the extraction of the oil immediately after harvest. Extraction is done mainly in small, decentralized mills. Today, mechanical picking is possible (Chabar and Zguial 1987). Figure 4.38 gives the flow chart for the production of olive oil.
4.2.2.5 Fact File of Olive Oil. This fact file shows the physical and chemical data of olive oil (Fig. 4.39 and Table 4.23). For olive oil, different traded qualities exist that allow very different pricing. Virgin olive oil is the highest quality with the following three grades: extra virgine @FA c l%),virgine (FFA c 1.5%) and semi-fine (FFA c 3%). The lowest edible quality grade is must oil. The oil called “lampante,” which is for industrial purposes, may have a higher FFA content (FFA c 3.3%). Virgin olive oil contains pigments that are left in the oil. Minguez-Mosquera et al. (1991) determined up to 54 ppm of the chlorophyll type and up to 22.5 ppm of the carotenoid type. In 1990, the price for virgin olive oil was -$5000/ton. Sources for more detailed information can be found in the references section. 4.2.3 Avocado Oil 4.2.3.1 Botany, Composition, and Properties of Avocado Oil. Avocado (Persea gratissima gaertueri) is a 12- to 15-m high evergreen tree that grows mainly in the Mediterranean region and in the Southern U.S. Although the kernel has an oil content of only 1-2%, the mesocarp of the avocado contains a substantial amount of oil, depending on the sort, i.e., normally 10-30% of the total fruit weight. In the edible part, Florida fruit commonly contain -40% oil; the Turkish avocado, however, can contain as much as 75% oil (Fig. 4.40). As in palm oil, -tic and oleic acid are the main fatty acids with oleic acid being dominant. Additionally, up to 2.2%myristic acid and 1% arachic acid are to be found (Fig. 4.41).
Fats and Oils Handbook
218
1-
< 40.C. for hqh amounb of virgin oil r n . p u W n of the oii in miiaxeun
i win
(MH a d b n i( needed)
last melueur, to make the pulp mon nuid
big decanten (continuously)
Olive oil
I Proportion[%I
Fstty add Palm& PlhitObic
Stesric oleic Linobic
Linobnic Arachic
c 180 C 16:l C 18:O C 18:l c 182 C 183 c 20:o
-
7.5 20.0 0.3 3.5 0.5 5.0 55.0 83.0 3.5 -21.0 < 1.5 < 0.0
Fig. 4.39. Fact file of olive oil (fatty acid composition).
219
Vegetable Fats and Oils
TABLE 4.23 Fact File of Virgin a n d Refined O l i v e Oil a n d O l i v e Pomace Oil German: Olivenol
French: huile d'olive
Relative density Refractive index Saponification value Iodine value p-Sisterol Unsaponifiable matter
(at 20°C; ref. water 20°C) (nD40) (mg KOH/g oil) W i j s method) (% of total sterols) (gkg oil)
Spanish: aceite de oliva 0.910-091 6 1.4677-1.4705 184-1 96 75-94 593 4 5
Solidification point
ooc
Melting point
-9 to 0°C
Solids content at
(OCPF)
0.32
514 1
10/50
20/68
30/86
35/95
(%)
<0.3
0
0
0
0
0
World market price (U.S. $/MT)
min
Price index for virgine 1995 average compared with 10 years ago 150% with20yearsago 180% with30yearsago 320%
1964-1 995 1964-1 969 1970-1979 1980-1989 199C-1995
Differences for olive pomace oil Refractive index Saponification value Iodine value Unsaponifiable matter
920 1073 920 2255 3235
Virgine 0 3900 1220 2055 3070 5145
--1
max
Lampante min 0 max
6950 1375 31 15 3965 6950
780 790 780 1885 2670
(nD40) (mg KOH/g oil) (Wijs method) (gMg oil)
2845 888 1565 2215 3725
3885 1095 2505 2910 3885
1.4680-1.4707 182-1 93 75-92 <30
Differentiation of virgin olive oil (V), refined olive oil (R) and refined olive pomace oil (P) Max satur.FA in 2-position
v R P
Max. acidity KOH/g oil
1 .5% 1.8% 2.2%
Definitions for olive oil
6.6 0.6 0.6
Peroxide value
Extinction 232 270
Volatile matters
Insoluble impurities
9 0 210%
3.5
-
50.2% 20.1'/0
-
6.0
50.10% 50.05% 20.05%
0.3 1.1 2.0
10.1%
trans fatty acidsa
alnternational Olive Oil Council Trade Standard (May 1992) limits for all olive oils as percentage of total sterols: cholesterol 50.5%; brassicasterol 50.1%; campesterol 54.0%. Olive oil (R) Nonextracted oil, nonpomace oil, blend of refined olive oil and virgin olive oil; total sterols 51 000 ppm. Virgin olive oil (V) Mechanically extracted only, under restricted thermal conditions that 0 do not cause any alteration; all virgin oils (V): total sterols ~ 1 0 0 ppm. Extra virgin olive oil (V) Organoleptically rated 6.5, FFA < 1% w/w, calculated as oleic acid. Fine virgin olive oil (V) Organoleptically rated 5.5, FFA < 1.5% w/w, calculated as oleic acid. Semifine virgin olive oil (V) Organoleptically rated 3.5, FFA < 3.5% w/w, calculated as oleic acid. Lampante olive oil Organoleptically rated <3.5, FFA > 3.3% w/w, calculated as oleic acid. Refined olive oil (R) Olive oil refined without alteration; total sterols 51000 ppm, Extracted from olive pomace; not re-esterified; crude: total sterols Olive pomace oil (P) 12500 ppm; refined: total sterols 1 1800 ppm.
220
Fats and Oils Handbook
Fig. 4.40. Avocado fruit and composition of avocado (photo: Schuster 1992; courtesy of DLG Verlag, FranMu rt).
Of the only 1 or 2% of the oil contained in the kernel, -55% is unsaponifiable matter (Bide and Young 1971, Mazliar 1975). The kernel oil consists of approximately (depending on sort) 20% palmitic, 3.8% palmitoleic, 0.6% stearic, 28% oleic, 40% linoleic and 6.5% linolenic acid (Nagalingam 1993).
Fig. 4.41. Main fatty acid composition of avocado oi I.
22 1
Vegetable Fats and Oils
TABLE 4.24 Avocado production Avocado
1980
1990
1993
1994
1995
Total world (MMT) Mexico
1.40 0.42 0.17 0.13 0.1 1
1.46 0.32 0.16 0.13 0.1 2
1.98 0.75 0.13 0.1 5 0.1 2
2.06 0.72 0.14 0.1 5 0.12
2.06 0.74 0.1 6 0.1 5 0.12
us. Dominican Republic Brazil
4.2.3.2 Economic Importance of Avocado Oil. The oil has no real importance as an edible oil (production figures in Table 4.24). However, it is one of the three well-known pulp oils and therefore mentioned here. As mentioned earlier, its main usage is in the cosmetics industry. 4.2.3.3 Harvesting, Storage, and Oil Extraction of Avocados. Avocados do not ripen on the tree but only after picking. It is assumed that inhibitors hinder the ripening processes on the trees (Biale 1950, Tingwa and Young 1975). The right time for picking is determined by measuring the fat content (8% w/w, U.S. fruit), dry matter (>22%)or by judging the color. Figure 4.42 shows the processing steps of avocado oil production. 4.2.3.4 Fact File of Avocado Oil. Table 4.25 presents the information for avocado oil.
4.3 Seed Oils In contrast to oil fruit, oilseeds are less sensitive toward spoilage because they are much more stable mechanically and have a much lower water content. It is therefore much better to store the seeds than it is to store the oil because the seeds are equipped by nature with protective mechanisms and protective substances. These mechanisms have to ensure that the energy reserve of the seed, namely, the fat, can survive the time to germination-and that may be very long. Even seeds of wellknown plants that are not at all connected with oils and fats contain triglycerides, sometimes in surprising amounts (Table 4.26). Despite their high fatloil content, most of these seeds are not used for oil production; the number of seeds extracted is very limited. Some of the potential seeds for oil extraction occur as waste in the production process of other food (e.g., tomato seeds in tomato juice production or grape seeds in wine-pressing); however, they are contained in matrices that are very difficult to process; therefore they cannot be extracted economically today. Others grow wild and are dispersed in regions difficult to access, such as the babassu palm, for example. Some plants with high oil content contain unwanted components that are difficult to separate, or their extraction meal is of no use at all.
Fats and Oils Handbook
222
Avocado
(whole hitwith stone)
Washing
Removal of dirt
Grounding
Hammer mill (thorough mechanical breakdown. avoiding m u b i o n fornation)
Ground avocado Double wall mixing trough; indirectly heatable disintegration of oil wlb
Muing Dwelling
I
Fruit flesh, stones Hot water >>>
Decanters (conunuowly)
Polishing
Separators
I
Avocado oil
Fig. 4.42.
Effluent
F l o w chart of avocado oil production.
TABLE 4.25 Fact File of Avocado O i I German: Avocado61
French: huile d'avocat
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 25°C; ref. water 20°C) (nD40) (mg KOH/g oil) (Wijs method) (fig oil)
Melting point:
-C '
World market price per MT (mid-1995)
Spanish: aceite de aguacate
Solidification point
0.9104921 1.466-1.468 185-1 97 70-95 4 6 7-9°C
37OC-3900 U.S.$
The following section deals with those seeds that are used for oil extraction worldwide or at least in substantial parts of the world. In Chapter 4.4, three wellknown oils are briefly covered, even if they are not suitable for human consumption. For the benefit of completeness, a few oils are described that are of special interest although they occupy only a small market segment, e.g., walnut oil or grape seed oil.
Vegetable Fats and Oils
223
TABLE 4.26 Fat Content of NonoiI Seeds
Seed
Fat (Yo)
Apple Apricot Lemon Coniferae Tomato
20 40 50-54 25-30 25
4.3.1 Soybeans
4.3.1.1 Botany and History of Soybeans. Soybeans (Glycine soju) stem from China, where they were mentioned in the history of the emperor Chennung (2800 B.C.). Today, they are still mainly cultivated there, as well as in the U.S. and Brazil. Recent theories assume that the true origin of the bean is Australia, from where it has conquered the Pacific region (Broue et al. 1977 and 1978). Soybeans have been native for a long time in Japan where primarily their protein content (for tofu and similar food) plays an important role. The U.S., today's prominent producer, started cultivation at the beginning of the 20th century (Probst and Judd 1973). Soybeans came to Europe with missionaries (1740) who brought them to the Paris botanical garden. In 1872, the soy plant was exhibited as a plant with potential at the Vienna world's fair. It came to Central Europe (Germany) in 1872, brought home from the German-French war by an officer named Werhahn, who cultivated it on his farm at Meissen, a city close to Saxony's capital Dresden, mainly known for its china. Soybeans can stand moderate climate but are sensitive toward cold nights. The plants can be grown up to -3000 m (10,000 ft) above sea level. Optimal living conditions are days 12-16 h long and temperatures of 3&32"C (Salunkhe 1986). The higher the temperature, the more the proteidfat ratio is shifted towards fat (Hymowitz and Newall 1981). Soy plants can grow to 30-180 cm in height. Their fruit are hulls 2-10 cm in length and 2 4 cm in width that hold 1 4 beans (Fig. 4.43). These beans are oval to round, yellow to violet; they rustle in their hull when they are ripe. The weight of 1000 seeds is between 50 and 350 g. Besides the oil content of 17-25 % (usually 20% or a little below), the high protein content of 3 0 4 0 % is of special importance. Soybeans are one of the most prominent protein sources in the world.
4.3.7.2 Economic Importance of Soybeans. Within 50 years, soybeans have developed into the most important oilseed grown and comprise approximately one third of all oilseeds cultivated. More than 50% of the beans come from the U.S. (in the fall) (Table 4.27). In the 1970s, cultivation in South America started and now accounts for -25% of the world harvest (in the spring). Due to that southern hemisphere crop, fresh beans are now available twice a year. Maximum yields in 1994 have been reported by Italy (3606 kgha), Ethiopia (3090 kg/ha), Egypt (2883 kg/ha), and the U.S. (2815 kg/ha); Ethiopia and
Fats and Oils Handbook
224
Fig. 4.43. Soybeans. Zimbabwe, which ranked numbers one and two in 1990 (4356 and 3453 kgha, respectively), were down to 3090 and 2500 kg/ha, respectively. Western Europe (European Union) had an average of -2300 kgha. The lowest yields of those countries monitored by the F A 0 were reported for Kazakhstan (229 kgha), Ethiopia (309 kgha), and Malaysia (333 kgha) (see Table 4.28). TABLE 4.27 Soybean Production (-85% Used for Crushing; Crushing Oil Equivalent -1 8%) Soybeans(MMT)
1935
1950
1970
1980
1990
1993
1994 .-
1995
Total world
12.3 1.2 10.0
46.5 17.3 27.3 7.7 15.1 30.8 8.0 11.5 8.3 0.08 0.3 1.5 0.001 0.001 0.03
93.8 54.8 7.6 13.4 3.6 0.04
107.8 52.3 11.5 19.9 10.7 2.2
114.9 50.9 15.3 22.6 11.0 1.4
136.7 69.6 16.3 24.9 11.3 1.0
129.9 58.6 13.5 25.6 12.0 1.0
us.
China PR Brazil Argentina EU (10)
-
-
1960
-
-
TABLE 4.28 Production Yield of Soybeans Soybeans(kg/ha)
1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world
1090 1160 1160
1180 1400 1670 930
1080 1600 780 1140 980
1330 1800 840 1250 1030
1480
2030
1900
1703 1989 1099 1578 2014 1891 2697 1690
1840 2180 1302 2094 1601 2359 3134 2585
1857 2194 1237 2123 2159 2456 3155 1577
2207 2781 1735 2164 2038 2610 3350 1805
2022 2347 1662 2196 2044 2578 3614 1704
us.
China PR Brazil Argentina France Italy Spain
-
800
-
-
-
-
-
-
-
Vegetable Fats and Oils
225
The increase in acreage in the US.,the dominant producer, occurred rapidly. It developed from cultivation in Iowa, Illinois, Indiana, and Idaho in 1940, with Missouri, Minnesota and Arkansas added in 1950, and Mississippi, Kansas, and North Carolina in 1960. Increases in yield were paralleled by increases in acreage. In 1927, an acre yielded -12.2 bushels (-700 m a ) , whereas it doubled by 1960 and increased by another 60% to date. As a result of its dominant position, soybean oil plays a leading role in pricing (Figs. 1.10 and 1.13). The share of the value of the oil as a percentage of the price of whole beans dropped from -55% to -30% between 1950 and late 1980 (Erickson 1990). The market is now driven more by demand for meal than by the demand for oil. 4.3.7.3 Composition and Properties of Soybeans and Their Oil. Soybeans have a thin hull that makes up -7% of the seed weight. Depending on the genotype, the protein or oil content can be above or below the average. Nondehulled beans have an oil content of -20% (Fig. 4.44). Soybean oil is a good all-round oil. Its iodine value lies between 120 and 143, its solidification point below -8°C. It is rich in unsaturated fatty acids, with a relatively high amount of linoleic acid and, compared with other seed oils, a very high content of linolenic acid (Fig. 4.45). In addition to the main fatty acids, the oil contains up to 0.5% myristic acid and up to 3.5% saturated fatty acids with more than 20 C-atoms. In its triglyceride composition, the high amount of triglycerides with six and more double bonds appears remarkable (Fig. 4.46). Extraction meal from soybeans has a protein content of 40-50%. After heat treatment (toasting; see Chapter 5.4), the meal is suitable for animal feeding. Digestibility is then >80% because antitrypsine-factors are destroyed. Toasting is regarded optimal if the urease activity is ~ 0 . mg 5 nitrogen/(g min) and the protein has a solubility of 2040% in water (Lennerts 1984). The meal should not be stored longer than 3 mo (meal properties are listed in Figure 4.47).
-
Fig. 4.44. Composition of soybeans.
226
Fats and Oils Handbook
Fig. 4.45. Main fatty acid composition of soybean oil.
Because soybeans are an important protein source, they play a paramount role in food technology, not only in fat technology. Overviews include Smith (1972), Circle (1972), and more recently, Erickson (1995). 4.3.7.4 Soybean Harvest, Storage, and Oil Extraction. Soybeans are harvested with harvest-threshers when the plant is dried and the leaves have already fallen
Fig. 4.46. Triglyceride composition of soybean oil (after Johanssonand Bergenstahl 1995).
227
Vegetable Fats and Oils
Fig. 4.47. Composition of expeller cake and extraction meal of soybeans.
(Table 4.29). After harvesting, the seed should be stored with a moisture of <15% (optimal 13%), because higher water content promotes the formation of FFA. In the fields, the beans need 12-24 d to dry from the 5 0 4 0 % water content of the natural seed to the desired value. Water content <12% should be avoided because this decreases the mechanical stability of the seed (Weiss 1983). Above 12%, the growing conditions for fungi improve; however, they do not endanger the beans if storage lasts <1 y (Christensen and Dorworth 1968); other authors assume storability of many years with that moisture content, if stored below 20°C. The ability to germinate serves as a yardstick for the negative influences of storage. It is 100% after 12 wk if stored at 15"C, 90% at 20"C, and 10% at 25°C. Stored at 3072, the beans no longer germinate at all (Christensen and Dorworth 1968). To prepare for extraction, soybeans do not require any special pretreatment (Fig. 4.48). 4.3.7.5 Fact File of Soybean Oil. The fact file summarizes the fatty acid composition, physical data, and price development of soybean oil (Table 4.30, Figs. 4.49 and TABLE 4.29 Seeding and Harvesting Periods for Soybeans Jan ~~~
Feb
Mar
Apr
May
H H
H H
June
July
Aug
Sept
Oct Nov Dec
_ _ _ _
Argentina Brazil China PR
us.
S S
S
s
s
H
H
H
H
H
Fats and Oils Handbook
228
I
ahulanp (5.2.1.2.3)
-+
-+
b1UbblA
7065%
Fig. 4.48. Flow chart of soybean oil production.
4.50). Further sources that contain detailed information on soybeans and its oil are list-
ed at the end of this chapter. The importance of soybeans is shown by the fact that Food Science and Technology abstracts alone list more than 20 publications yearly dealing with soybean oil. In addition, it is mentioned in many other publications.
Vegetable Fats and Oils
229
TABLE 4.30 Fact File of Soybean Oil (Bean Oil) German: Sojaol
French: huile de soya
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 20°C; ref. water 20°C)
Spanish: aceite de soja
0.91M . 9 2 5 1.466-1.470 189-1 95 120-1 43 c15
(nD40) (mg KOWg oil) Wijs method) (fig oil)
Melting point:
-9 to -1 1°C
Solids content at
("v"F)
0/32
5/41
1Q/o
2W68
3W86
35/95
(%)
0.5
0
0
0
0
0
Solidification point
World market price
Price index (1 995 average compared to average) 10 years ago 103% 20 years ago 104% 30 years ago 262%
C 14:O C 119 7.0 c 11:1 C 18:O 3.0 c 181 18.0 C 18:2 50.0 C 18:3 5.1
c mo c 20:l
-8 to -1 8 T
(US. $/MT)
min
0
max
1962-1995
157
440
1044
1962-1 969 1970-1979 1980-1989 1990-1995
157 220 279 398
223 487 493 508
303 303 1044 670
< 0.5 14.0 < 1.0 5.5 -20.0 -57.0 10.0 c 0.8
-
-
< 1.0
I
P
W PI
I
Fig. 4.49. Fact file of soybean oil (fatty acid composition). 4.3.2 Cottonseed Oil
4.3.2.1 Botany and History of Cotton. Cotton (Gossypim)is cultivated mainly for its fiber. The ratio of fibers to seed is -1:2. The seed itself contains -2&25% fat. From tools and fabrics found in excavations, it can be concluded that cotton has been cultivated for 45W5000 years. Up to 600B.c., India maintained a monopoly on cotton (called woven wind). In the period 600-500 B.C., cotton came to Egypt;later, in 333 B.C.,it was imported to Europe by the Greek emperor, Alexander the Great. The oil content of the seeds is mentioned for the first time by the Greeks, Herodot and Theophrast. In the Middle Ages, the seed was rediscovered by Marco Polo (1271) who reported on it. Only in the 19th century did it become an item traded worldwide because only then did mechanical delintering, spinning and weaving equipment
230
-I----
Fats and Oils Handbook
World market price [US $ and
Moo
_ _ - ~ Soybean oil
I
Moo
Fig. 4.50. World market price development of soybean oil.
become available (Lennerts 1984). The first important cottonseed oil mill was opened at the beginning of the 19th century in Natchez, Mississippi. The plants bring forth large attractive flowers; the seeds are 8-12 mm in length, egg shaped, and brownish black (Fig. 4.51). Besides the thin, hard hull and the fibers, there is a kernel that comprises -50% of the seed. The kernel itself contains -20-35% oil and up to 40% protein, so that the oil of the delintered seed accounts for -22.5% and of the nondelintered seed for -15% of the total weight. 4.3.2.2 Economic Importance of Cotton. Detailed records on the cotton imports and exports of the U.S. and the UK have existed since 1697. This allows the increasing importance of cotton to be easily tracked and shows an exploding tonnage in the 19th century (for details see Bailey 1948).
Fig. 4.51. Cotton.
Vegetable Fats and Oils
231
TABLE 4.31 Cottonseed Production (-80% Used for Crushing; Crushing Oil Equivalent -1 5%) Soybeans (MMT)
1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world USSRa China PR US. India Pakistanb Brazil Egypt EU (10)
12.8 1.3 1.5 4.9 2.3
10.6 1.0 5.0 0.9 0.5 0.4 0.8
18.3 2.6 3.0 5.4 1.5 0.8 0.9 0.8 0.1
21.1 4.6 3.0 3.9 2.1 1.1 1.3 0.9 0.2
21.6 4.5 4.5 4.0 2.8 1.3 1.1 0.8 0.2
33.8 4.9 8.9 5.5 3.6 3.0 1.2 0.5 0.5
30.5 4.4 7.5 5.7 4.2 2.7 0.7 0.6 0.6
34.1 4.0 8.7 7.0 4.7 3.0 0.9 0.5 0.6
36.1 4.2 9.5 6.3 4.8 3.7 0.9 0.5 0.6
0.8 0.8 -
-
dAnd successor states. b1935 figures for India and Pakistan summarized under India
Between 1940 and 1944, cottonseed oil was driven out of the number one position in the U.S. by soybean oil. In this period, its share in shortening production decreased from 68.9 to 37.4%, whereas that of soybean oil increased from 17.7 to 47.4% (Black 1948). An idle capacity in cottonseed mills of >9.5 MMT resulted (Alderks 1948). This capacity was then shut down. Egypt and the U.S. are well known as producing countries; the highest production, however, is in China and the USSR (1990). Between 1980 and 1990, a renaissance of cotton caused a worldwide production increase of -90%. Earlier, synthetic fibers had made cotton less important followed by a decrease in importance of the by-product cottonseed oil. Still, cottonseed has the second highest tonnage of all oilseeds, admittedly with a relatively low oil equivalent (Table 4.3 1). A relatively high amount of the seed is used directly as animal feed without prior oil extraction. The 1994 maximum yields were in Turkmenistan (6417 kgka), Israel (4505 kgka) and Syria (3495 kgka); the lowest yields of all recorded countries occurred in Antigua and Barbuda (157 kgka), Uganda (165 kgka) and Kenya (244 kgha; Table 4.32). The markets for cottonseed oil are mainly those of the producing countries. In Europe, cottonseed oil has no importance at all. TABLE 4.32 Production Yield of Cottonseed Cottonseed(kg/ha) 1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world USSRa China PR US. India Pakistana Brazil Egypt
400
610 1280
660 1650 610 860 240 610 450 1270
1251 3075 1613 1493 495 1027 465 2646
1596 2642 2395 1882 694 1644 964 2296
1594 2250 1791 843 1463 1071 2916
1602 2356 2073 925 1673 1157 2243
1683 2638 1575 903 1806 1180 2775
390 510 430 230 390 1030
-
360 550 170 360 290 980
-
860 250 460 350 1130
V o r 1935, India and Pakistan are summarized under the heading India.
232
Fats and Oils Handbook
Fig. 4.52. Composition of cottonseed. 4.3.2.3 Composition and Properties of Cottonseed and Its Oil. Starting with the whole seed, cottonseed has the composition shown in Figure 4.52. After delintering, this changes dramatically. Cottonseed has an iodine value of between 99 and 117. The oil is rich in unsaturated fatty acids, with linoleic acid comprising two thirds of that content. Palmitic acid comprises two thirds of the saturated acid content. Besides the common main fatty acids, cottonseed oil can contain up to 2.8% palmitoleic acid. "he solidification point of the oil lies some degrees below 0°C. Despite its relatively high content of polyunsaturated fatty acids, cottonseed oil contains the highest amount of saturated fatty acids of the seed oils (Fig. 4.53). Typically 2&25% of the oil solidifies when cooled (Jones 1990). The type of triglyceride is dominated by that with two molecules of linoleic acid and one molecule of saturated fatty acid, predominantly palmitic acid (Fig. 4.54). The majority of cottonseed oil in the US.is further processed (Chapter 6.4) to yield a vegetable equivalent to lard. Less than 20% is used as oil as such or in margarine. Cottonseed oil for use as salad oil has to be winterized. The nontriglyceride content of cottonseed kernels is rich in protein (-58%). It is used mainly as fodder. Most of the cottonseed is processed in the country of cultivation, with the oil and meal being shipped to the customer, if exported. Because of its high content of gossypol (see Chapter 2.6), the protein is toxic for pigs and poultry and therefore not suitable as an all-round feed-stuff. Meal from nondehulled cottonseed has a low digestibility; therefore, upper limits for raw fiber content are set (Fig. 4.55).
Vegetable Fats and Oils
233
Fig. 4.53. Main fatty acid composition of cottonseed oil.
Fig. 4.54. Triglyceride composition of cottonseed oil (after Oueadrogo and Beard 1982).
234
Fats and Oils Handbook
Fig. 4.55. Composition of expeller cake and extraction meal of cottonseed.
Expeller meals contain 0.5-0.95% gossypol, of which 1&13% is free gossypol that is poisonous for some animals. In trials, amounts of slightly above 0.1% free gossypol were fatal when feeding calves. Developmental disturbances with piglets were reported with an amount as low as 0.01% gossypol. Eggs from hens fed with cotton meal show a greenish to black discoloration when stored (Lennerts 1984). The protein can also be used as a base material for adhesives; the hulls can serve as filling material for plastics as well as a source material for the production of furfural and tannin (Salunkhe 1986). Extracted gossypol can be used as an antioxidant for nonedible products. The oil-soluble gossypol is carried in small capsules in the seed that are destroyed during seed processing, thus freeing the gossypol. There have been attempts to breed new varieties of cotton that lack these capsules. Such cotton would dramatically improve the utilization of the meal. 4.3.2.4 Harvest, Storage, and Oil Extraction of Cottonseed. Cottonseed ripens 6-8 wk after flowering and is harvested together with its wool. Before processing for oil (see Fig. 4.56),small linters have to be removed from the seed. Mechanical delintering is not easy. In particular, the dust that is generated creates great problems. Therefore, alternatives processes have been tested. One of these alternative processes is wetting the seed with diluted acid followed by evaporation of the water. Thus the acid becomes concentrated and loosens the linters from the hull. The acid-loaded linters removed cannot be used further; they are waste. Usually the linters are sold to the cellulose industry. The main harvesting periods are spring in the southern hemisphere and autumn in the northern. In Indonesia, harvesting can be done year-round as a result of the constant temperature.
Vegetable Fats and Oils
235
Cottonwed (whLrsrcl,nowoal)
Oilmntent-13.5% Removal of sand,straw, cor*gn malerial (a. 10Otld per Line) Seed mobtum c 10%
Bulk den*
280290 pn; (f stored mom than 6 wsekr t
ZO'C)
I
Dellntering (5 2 I 4) I
07-80% fm ofl l n l a
Cutthg seeds to h a t sepamtm of h u h b l 5 % residual hulk tor tmnw prmiitbn during w h t exhldion Cap.city of bb machines-75 Vd >>> H u b Dehulbd wed
=)
=.
Filling maLsri.l tor pbtles Pmductbn ol xylou. Wnl. tannin
Bulk danrity 630 gA Oil rantent -26% (10% residual hub)
I
11011S'C mobtum dropr horn II-20% to -5% Treatment also hem to lructivmgwrypol
(5.2.4.1)
Expefb mka
K&#
.c
and flaking
R d d W (R)
MU&*
4 Extradon m a 1
I
n cake
Crude cdtonwed oil
Fig. 4.56. Flow chart of cottonseed oil production.
After delintering, cottonseed still contains some fibers that could not be removed (also a lot of fluff remaining). Before storage and shipment, the seed is dried with hot air. If the water content is >15%, the FFA content rises to >15% after 100 d of storage (Freyer 1934). Therefore, with a humidity above 15%, stor-
Fats and Oils Handbook
236
TABLE 4.33 Fact File of Cottonseed Oil German: Baumwollsaatol
French: huile de coton
Spanish: aceite de algodon
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 2ooC; ref. water 20°C) (nD40) (mg KOHIg oil) (Wijs method) @'kg oil)
0.9184926 1.458-1.466 189-1 98 99-1 19 4 5
04°C
Cloud point:
-3 to -1°C
Solidification point
Solids content at
("CPF)
0/32
514 1
10150
20168
30186
35/95
(Oh)
<0.5
0
0
0
0
0
World market price
Price index (1 995 average compared to average) 104% 10 years ago 20 years ago 105% 30 years ago 2 64%
(U.S. SIMT)
min
0
max
1962-1 994
235
529
1257
1962-1 969 1970-1979 198G1989 199G1995
235 280 446 515
29 603 642 686
408 1257 1063 900
age temperatures of 20°C should not be exceeded. With moisture content ~ 1 2 % (Anonymous 1962),no increase in FFA could be detected. Cottonseed has to be well ventilated during storage because enzyme activity induces exothermic processes that heat up the seed insulated by the adhering fluff. The necessary storage conditions are given by Alderks (1948).
4.3.2.5 Fact File of Cottonseed Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.33, Figs. 4.57 and 4.58). Further literature is given at the end of this chapter.
Fig. 4.57. Fact file of cottonseed oil (fatty acid composition).
Vegetable Fats and Oils
237
Fig. 4.58. World market price development of cottonseed oil. 4.3.3 Sunflower Oil
4.3.3.7 Botany and History of Sunflower. Sunflower (Helianthus annuus) stems from America and had already been cultivated in the U.S. when the first Europeans arrived. The seeds were roasted and milled (Carter 1978). Findings in Arizona and New Mexico indicate that it had been used as early as 3000 B.C. In 1569, the sunflower came to Southern Europe with the Spanish explorer Monardes. From there, it spread across the whole continent and was introduced to Russia by Tsar Peter the Great, who brought it back from one of his trips to the West. Russia has become one of the main countries for sunflower production. Having been forgotten in the U.S. and almost erased, it was reimported in the 18th century (Hurt 1948). Further importance came only after World War I1 when a species cultivated in Russia that was suitable for mechanical harvest was reintroduced. Sunflower grows in a moderate climate mainly in America, Europe and China with temperatures predominantly between 20 and 2 9 2 , although optimal temperatures would be 27-28°C (English ef al. 1979). Sunflower can stand temperatures between 8 and 34°C with a high tolerance against differences in day and night temperature. The plant reaches 1-3 m in height, sometimes up to 5 m, normally with flat roots. The stem has a diameter of 5-6 cm, with an upper limit of 10 c m Sunflowers turn their heads following the movement of the sun until almost all of the flowers that together build the head are pollinated; then the head stays fvted to the east (Fig. 4.59). It takes -70 d from sowing to flowering. After 130 d, the seeds are mature and 10 d later they can be harvested. The head consists of 1 W O O O single blossoms. The thousand-seed weight is between 50 and 150 g. 4.3.3.2 Economic Importance of Sunflower. Sunflower production has increased during the last 25 years mainly because of the high content of linoleic
Fats and Oils Handbook
238
Fig. 4.59. Sunflower.
acid that is considered nutritionally positive (essential fatty acid). In the European Union, sunflower production has increased 300-fold from 1960 to 1985 (Table 4.34). Production is sensitive to weather influences. In the US.,for example, in 1988, only 700,000 MT could be grown as a result of bad weather; in addition, this small amount had an atypically low proportion of linoleic acid. Maximum yields in 1994 were reported to the F A 0 by Italy (2596 kg/ha), Greece (2577 kg/ha) and Austria (2544 kg/ha); minimum yields came from Tanzania (370 kg/ha), Namibia (457 kg/ha) and Mozambique (500 kg/ha; see Table 4.35). Sunflower oil is usually higher in price than soybean oil. See Table 4.36 for seeding and harvesting dates. TABLE 4.34 Sunflower Seed Production (-SSo/0 Used for Crushing; Crushing Oil Equivalent -43%) ~
Sunflowerseed(MMT) Total world USSR U.S. Argentina Romania Bulgaria Turkey Hungary Yugoslavia France China PR India Spain EU (10)
~~
~
~
~~
1935
1950
1960
1970
1980
1990
1993
1994 1995
2.5 2.0
3.0 1.0
6.2 3.9
10.0 6.0 0.1 0.8 0.8 0.4 0.4 0.1 0.3 0.1
15.7 5.3 3.5 1.7 0.9 0.4 0.6 0.5 0.3 0.3 0.3
22.1 6.5 1.0 3.9 0.6 0.4 0.9 0.7 0.4 2.3 1.5 0.6 1.3 3.6
20.0
22.2
1.2 3.0 0.7 0.4 0.8 0.7 0.2 1.6 1.3 1.4 1.3 3.6
2.2 4.0 0.8 0.6 0.7 0.7
26.2 7.0 1.8 5.5 0.9 0.7 0.9 0.8
-
-
2.1 1.3 1.5 1.0 3.5
2.0 1.3 1.5 0.6 3.5
-
-
0.2 0.2 0.1
-
1.0
-
0.1 0.2 0.1
0.8 0.5 0.3 0.1 0.1
-
-
-
-
-
-
-
-
0.1
0.1
-
0.2
-
-
Vegetable Fats and Oils
239
TABLE 4.35 Production Yield of Sunflower Seed Sunflowerseed (krr/hai
1935
1950
1960
1970
1980
1990
1993
1994
1995
610 590 880 880 890 850
680
870 940
1170 1280 930 850 1300 1590 1090 1410 1410 1610 1270
1173 1138 1323 93 1 1640 1716 1260 1796 1796 2348 1095
1355 1406 1378 1409 1408 1301 1385 1879 1870 1978 1807
1071 966 ' 1160 1435 1183 904 1367 1751 1950 2090 1773
1158
1219
1580 1902 1312 1201 1263 1604
1333 1954 1306 1444 1500 1583
2082 1699
2067 1561
Total world USSR
us. Argentina Romania Bulgaria Turkey Hungary Yugoslavia France China
760
650 970 1450 900 1320 1320 1180 1200
-
830 980 900 930
970 1550
-
-
-
-
-
-
-
4.3.3.3 Composition and Properties of Sunflower Seeds and Their Oil. The kernel accounts for 70% of the seed. An oil content of -55% leads to 40% oil for the whole seed (Fig. 4.60). Sunflower oil contains >85% unsaturated fatty acids with more than two thirds of all fatty acids being linoleic acid. Selected parcels of oil contain >69% linoleic acid (usually called high-PUFA); the limit for highPUFA is not regulated but lies between 68 and 70%). The linoleic acid content is very much dependent on the climatic conditions (Fig. 4.61), so that high-PUFA seed normally OCCUT in U.S. and French seeds. In France, there is a difference of 20%(rel* tive) in linoleic content between seeds from the north and the south of the country (Veldstra and Klere 1990). Large differences between day and night temperatures p r e mote linoleic acid formation. The solidification point is below -15°C; the iodine value lies between 110 and 145. If the linolenic acid content is higher than 0.1%, adulteration with rape oil can be suspected. Linolenic acid content of sunflower is always below 0.1%. New cultivations are high in oleic acid because of linolenic acid. Besides the main fatty acids and the above-mentioned linoleic acid, sunflower oil contains between 0.1 and 0.2% palmitoleic acid and traces of myristic acid. Sunflower oil and the sunflower itself are very well researched and documented so that the dependency of its composition on the temperature (Harris et al. 1978), the ripeness TABLE 4.36 Seeding (S) a n d Harvesting (H)Periods for Sunflowers Jan Argentina Romania USSR
us.
Western Europe
.
Feb
Mar
Apr
May
.
H
H
H
. .
s s
. .
.
s
.
s
.
s
June July
Aug
.
Sept
.
Oct Nov Dec
s
.
. .
H H
H H
H H
. .
.
. H
H H
H H
. .
.
Fats and Oils Handbook
240
Fig. 4.60. Composition of sunflower seed.
(Afzalpurkar 1979), the size and form of the head (Afialpurkar 1980), the different zones of the head (Ivanov et al. 1978), the environmental conditions (Davidescu e l al. 1979) and the genotype and creation of cultivation (Jaky et al. 1983) are well known. In addition, the influence of the lipids from the hull (Mdler et d.1985) and the Wax content, depending on the type (Morrison and Robertson 1983) and on irrigation-and sowing date (Momson and Robertson 1984), have been investigated. As can be expected from the fatty acid composition, trilinoleate dominates the triglyceride composition. The amount of triglycerides with four or more double bonds is >80% (Fig. 4.62).
CIS
ma
ca9
Cl8A
Cl8P
Fatty acid
Fig. 4.61. Main fatty acid composition of sunflower oil.
Vegetable Fats and Oils
241
Fig. 4.62. Triglyceride composition of sunflower oil (after Perrin and PrCvot 1995).
The nonfat content of sunflower kernels contains between 40 and 45% protein and is well suited for animal feeding. Because of the low lysine content, its amount is restricted in pig and poultry feeding. As noted above, in addition to the original types, new cultivars with different fatty acid composition are grown today. Types with fewer hulls and higher protein content are also cultivated; these can be much better used than the traditional ones, which have hull contents up to 45%. The figures show only these recent varieties, having hull contents of -30% (Fig. 4.63). More than 80% of the waxes of the seed is concentrated in the hulls. Sunflower meal (blended with flour) can be used for human nutrition. Protein concentrates from sunflower have an excellent digestibility; however, they are dark in color, which restricts their use. Their production is described by Clark et al. (1980). 4.3.3.4 Harvest and Storage o f SunflowerSeed, After fading, the plants dry in the fields and are harvested by combine harvesters. To harvest with minimum losses, the state of ripeness should be equal for all plants. Beyond that, it is important that they all have the same height because only then can the combine harvester be correctly adjusted. After maturing, FFA formation increases, which requires timely harvest. Losses from pests, plant diseases and weeds are an estimated 30% (Cramer 1967). After threshing, the sunflower straw is usually plowed under or burned; rarely is it used as fodder. Storage must be with a seed moisture <9.5% to avoid strong enzymic reactions heating up the seed. These reactions start within 12 h once the seed moisture is >20% (Sallans et al. 1976).
Fats and Oils Handbook
2 42
Fig. 4.63. Composition of expeller cake and extraction meal of sunflower seed. The processing steps of sunflower extraction (Fig. 4.64) do not differ significantly from those of soybean oil extraction. For use as a salad oil, sunflower oil has to be dewaxed if processed with its hulls. Otherwise, it becomes cloudy at refrigerator temperatures (see Chapter 6.3). 4.3.3.5 Fact File of Sunflower Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.37, Figs. 4.65 and 4.66). Further literature is given at the end of this chapter. 4.3.4 Peanut Oil
4.3.4.7 Botany and History of Peanuts. Peanuts (Arachis hypogaea), botanically beans not nuts, are a papilionaceous flower that most likely originated in Brazil. Therefore, it became known to the rest of the world only after the discovery of America, where it had already been grown since between 3000 B.C.and 2000 B.C. by the Incas. The Portuguese quickly transplanted the peanut to their African colonies (16th century). It came to China via the Philippines where it was brought by the Spanish from Cuba. The Spaniard Oviedo described it for the first time when he lived on the island from 1513 to 1524. Only in the 19th century did it obtain some importance in Europe and North America. Today, peanuts are cultivated in regions with a median temperature of 22"C, mainly in India, China, West Africa and the south of the U.S. The plant grows to a height of 3 0 4 0 cm. Its flowers require 2-3 mo for development. After pollination, the fruit-bearing part bows to the bottom and grows into the (preferably sandy) soil.
Vegetable Fats and Oils
P8ylt.d wnllowrr ma1
243
Crude sunflower wed oll
Fig. 4.64. Flow chart of sunflower oil production There the h i t develop within 2 mo to complete ripeness. Peanuts cannot stand frost; they prosper best if the average monthly temperature is >25"C (Fig. 4.67). 4.3.4.2 Economic Importance of Peanuts. Peanut cultivation increased within the last 25 years mainly in China (Table 4.38). However, only -40% is used for oil extraction (Ory and Flick 1990). The U S . is the only country in which a remarkable amount of peanuts are processed as a spread (seeChapter 8.6 regarding peanut butter).
Fats and Oils Handbook
244
TABLE 4.37 Fact File of Sunflower Oil German: Sonnenblumenol
French: huile de toumesol
Relative density Refractive index Saponificationvalue Iodine value Unsaponifiable matter
(at 20°C; ref. water 20°C) (nD@) (mg KOH/g oil) Wijs method) (fig oil)
Spanish: aceite de girasol 0.91 84.923 1.467-1.469 188-1 94 110-143 4 5
Cloud point:
-1 0°C
Solids content at
("CPF)
0/32
514 1
Solidification point 10150
20t68
30186
35/95
(Old
0
0
0
0
0
0
World market price
Price index (1995 average compared to average) 112% 10 years ago 90% 20 years ago 234% 30 years ago
-1 6 to -1 8°C
(US. $/MT)
min
0
max
1963-1 994
151
481
1178
1963-1 969 1970-1979 1980-1989 1990-1995
151 288 309 420
233 589 546 540
336 1178 95 1 745
surllam dl
P.Mtowc
UnoWC
C161
C103
c7.20, cu.0 m:1. c22:1. c241
< 0.5 c 0.5
Fig. 4.65. Fact file of sunflower oil (fatty acid composition).
The best 1994 yields of peanuts in shells were produced by Israel (6563 kgha) followed by Greece and Saudi Arabia (4OOO kgha each). In the small farms of Africa, 450 kgha is rarely exceeded; the lowest yields reported have been in Mozambique, Cameroon and Zambia (311, 313 and 323 kgha, respectively). For yields >1500 kgha, irrigation is a prerequisite (Table 4.39). The oil had high importance in the 1950s but has been displaced by other oils as a result of its high price. 4.3.4.3 Composition and Properties of Peanuts and Their Oil. The kernels make up -55% of the nut; they contain -45% fat, so that the fat content of the whole nut is slightly below 25%.They deliver -5.8 kcaVg (24.3 kJ/g; Fig. 4.68). Peanut oil is low in saturated fatty acids and especially rich in monounsaturated fatty acids, i.e., oleic acid. It therefore has a low solidification point, just a little
Vegetable Fats and Oils
245
Fig. 4.66. World market price development of sunflower oil. below 0°C. Its iodine value is 80-106. A small portion of high-melting triglycerides gives the oil a gel-impression at -5°C and below. These triglycerides are removed by winterization. Besides the main fatty acids, peanut oil can contain up to 0.5% myristic and up to 2.4% palmitic acid. There are also genotypes with 1.2 % linolenic and 1.2% eicosenoic acid (Fig. 4.69). The main triglycerides are those containing oleic acid, as can be deduced from the 50% oleic acid content. More than 50% of the triglycerides contain four or more double bonds (Fig. 4.70). The nonfat part of the kernels is used for animal feeding. If carefully processed, it can also be used for human consumption. Large-scale processing of peanuts with
Fig. 4.67. Peanut
Fats and Oils Handbook
246
TABLE 4.38 Peanut Kernel Production (-55% Used for Crushing; Crushing O i l Equivalent -47%)a ~
PeanutkernelsIMMT)
1935
1950
1960 1970
1980
1990
1993
1994
4.1 1.5 1.3 0.3
4.7 1.5 1.1 0.4 0.0 0.0 0.3
5.6 2.1 0.8 0.4 0.1 0.4 0.2 0.0
9.3 2.7 2.0 0.8 0.4 0.4 0.2
13.3 5.3 2.1 0.5 0.2 0.6 0.7
13.6 4.0 4.5 0.8 0.2 0.3 0.6
15.1 4.5 5.1 1.0 0.4 0.4 0.6
Total world India China PR
us. Sudan Senegal Nigeria EU (10)
-
0.2
-
_
7.3 2.7 1.4 0.7 0.2 0.3 0.2 0.0
0.0
0.0
0.0
1995
14.6 3.7 5.4 0.8 0.3 0.4 0.8 0.0 0.0
aAssumingkernel weight as 53% w/w of nut in shell.
TABLE 4.39 Production Yield of Peanuts in Shells Peanuts (kg/ha)
1935
1950
1960
1970
1980
1989
1993 -
1994
1995
Total world India China PR U.S. Sudan Senegal Nigeria Greece Italy Spain
960 980 1800 840 42 0
840 650
880 71 0
1330 500
1420 970
2040 2280
1860 1730 1560
1340 2100 2290 1500
950 800 1210 2300 990 670 1120 2000 2370 1670
1000 838 1487 2590 792 659 899 2763 2683 2495
1124 988 1737 2357 72 7 934 a75 3267 2500 2500
1235 92 6 2491 2250 548 849 1180 3294 4000 2795
1280 976 2562 2942 805 805 925 3538 3875 2797
1245 855 2684 2571 803 940 850 3538 3875 2857
Fig. 4.68.
-
Composition of peanuts.
Vegetable Fats and Oils
Fig. 4.69. Main fatty acid composition peanut oil.
Fig. 4.70. Triglyceride composition of peanut oil (after Perrin and PrCvot 1986).
247
248
Fats and Oils Handbook
the aim to produce peanut meal for human consumption was described in 1980 in the Oil Mill Gazette. The nuts are dried to 12% humidity, heated up to 82"C,kept for 30 min at that temperature and then further dried to 6%.They are flocculated and the oil is extracted. A white meal with 65%protein content is obtained (Fig. 4.71). Peanuts can be used for different purposes such as peanut-based cheese, milk and curd (Ramaturi 1964, Kelkar 1950 and Desikachar 1946). Protein production for special diets is also possible (Arthur 1951, Subramanyan et al. 1957). A large part of the production is used for snacks, chocolate bars and in the bakery industry. The wooden fibers of the shells are mainly burned. They can also serve as raw material for fiber boards in the building industry or as filling material; the plant itself can be used as silage fodder. 4.3.4.4 Harvest and Storage of Peanuts. Peanuts contain 1 4 kernels that are covered by a shell. In Africa, harvest remains predominantly manual; in the U.S., it is exclusively mechanized. The plants are tom from the soil after the tap-root, which may reach as deep as 2 m, has been cut. Then, they are left for 2 4 wk for drying until the nuts are picked (Table 4.40). Usually the nuts are transported as they are. The thousand-seed weight is 4W500 g. The nuts have a moisture content of 3040% ahd have to be dried after harvesting. To do so, they are left in open bags in warmer regions until they have the desired moisture of 5-10% (preferably 4.5%). In moderate climate, they are dried in a stream of warm air that is 10% above ambient temperature. To avoid splitting of the kernels, a drying rate of O S % h is targeted. Humidity is quickly conveyed from the kernels to the shells and from there released to the surrounding
Fig. 4.71. Compositionof expeller cake and extraction meal of peanuts.
249
Vegetable Fats and Oils
TABLE 4.40 Seeding and Harvesting Periods for Peanuts Jan China India Sudan
Mar
Apr
May
June July Aug
s s
H H
us. Senegal Nigeria
Feb
s s
Sept
Oct Nov Dec
H H
H H
H
H
S
s
s
H
S H
s
s
H
H H H H H H
H H H H
air. Peanuts are stored as whole nuts because this is the best protection against pests. Peanut produced for human consumption, and not for extraction, require more controlled storage conditions, i.e., lower temperature and better ventilation. Given 0°C and a relative humidity of 60-70%, peanut kernels can be stored up to 2 y (Woodroof 1983). Whole nuts can be stored 50% longer; however, relative humidity of the surrounding air should then be much lower to avoid rotting. Storage under N, or CO, atmosphere avoids losses from pests. The main threat, however, is mold (Aspergillusjluvus) toward which the nuts are very sensitive if stored or transported incorrectly. If they get wet, nests of mold can be built that grow to 2 m in diameter. This happens easily when a ship takes in water during sea transport. These molds are dangerous because they may produce highly toxic aflatoxins. Aflatoxin was discovered (and at the same time, the special sensitivity of peanuts) when -100,OOO young turkeys died in 1960 in England after they had been fed peanut extraction meal (turkey-X-disease). Discovering the reason for the widespread dying-off and developing reliable methods of analysis were extremely problematic. Temperatures between -16 and 38 "Care especially dangerous for peanuts (Anonymous 1978). Aspergillus jluvus already grows well when the moisture of the nuts is above 15%. From 27°C upward, aflatoxin formation is promoted, requiring 7-9 d (Diener and David 1966). A combination of environmental conditions have to be met to make the molds produce aflatoxin; appropriate storage prevents this. Removal of the toxin from the meal is practically impossible because it can resist temperatures up to -300°C; if it is in the oil, it can almost completely be removed during refining (see Chapter 7.7). Animals are very sensitive to aflatoxins. Aflatoxin causes liver cancer in animals. Although the carcinogenicity of aflatoxins in humans has not been proven, strict limitations on the level allowed are in effect. In some countries, they are so strict that peanuts for human consumption have to be checked one by one. They pass a photocell and those with a certain greenish color are sorted out. At present, the limits are 22 ppb in the U.S. (and 10 ppb in Germany) for the sum of aflatoxins B1, B2, G1 and G2; the limit for aflatoxin B1 is 5 ppb because the mechanism of aflatoxin formation has been found and analytical methods have been developed. The mold does not represent a real danger any more, but
250
Fats and Oils Handbook
Md.tw 4.5%
Fig. 4.72. Flow chart of peanut oil production.
it can cause immense commercial damage. Analysis of aflatoxin is very difficult because other substances simulate aflatoxin; the procedure should be limited to specialized laboratories. Figure 4.72 shows the processing of peanuts. 4.3.4.5 Fact File of Peanuts. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.41, Fig. 4.73 and 4.74). Further literature is listed at the end of this chapter.
Vegetable Fats and Oils
251
TABLE 4.41 Fact File of Peanut Oil German: Erdnukl
French: huile d’arachide
Spanish: aceite de cacahuete
Relative density Refractive index Saponification value Iodine value UnsaDonifiable matter
(at 20°C;ref. water 20°C)
0.914-0.917 1.460-1.465 187-1 96 80-1 06 <10
(nD40)
(mg KOH/goil) Wijs method) (g/ke. oil)
Cloud point:
-2oC
Solidification point
Solids content at
(OCPF)
0132
5141
1W50
20168
3W86
35/95
(%)
c6
<5
<4
<2
0
0
World market orice
Price index (1 995 average compared to average) 1 1 1 Yo 10 years ago 1 26% 20 years ago 273% 25 years ago
-2 to +3oc
0
rnax
236
686
1213
236 329 446 543
287 707 754 987
359 1213 1179 1060
(U.S. $/MT)
rnin
1967-1 994 1967-1 970 1970-1979 1980-1989 1990-1995
Peanut oil
Lho*nb
C 183
I-wl
I
Fig. 4.73. Fact file of peanut oil (fatty acid composition). 4.3.5 Rapeseed 4.3.5.1 Botany and History of Rape. Rape (Brmsica napus, Brassica campestris) is today cultivated mainly in Canada, Europe, India and China. It is much more durable than the other oilseeds, because it is able to withstand spring frost. It is therefore suitable for farming in the moderate- climates of the north (or the far south). Its origin is still not clear, but it appears to lie in Eurasia where it is already mentioned around 2000 B.C.;there is also a citation in Indian Sanskrit. In middle Europe, it is first mentioned in Holland in 1360 as “raepssaet.” Genotypes farmed today reach a height between 80 and 150 cm. Rape ripens 30-40 d after pollination. The pods have a length between 5 and 10 cm and are filled
252
Fats and Oils Handbook
Fig. 4.74. World market price development of peanut oil. with 1 5 4 0 seeds that have a diameter between 1.75 and 2 mm. The thousand-seed weight ranges from 4.0 to 6.5 g in winter rape and 2.5 to 4.0 g in summer rape (Fig. 4.75). 4.3.5.2 Economic lmportance of Rape. Until some 10-15 years ago, rape oil was not suitable for human nutrition in large amounts because it contained up to 30% erucic acid. In animal trials (with pigs), it was shown that erucic acid deposits in the heart muscle and negatively influences the metabolism of kidneys, spleen, thymus and thyroid gland.
Fig. 4.75. Rape.
Vegetable Fats and Oils
253
The use of rapeseed oil was therefore limited as a result of the restriction on the erucic acid content in food (oil), and the cultivation of new genotypes began. The cultivation of rape in Canada had been promoted during World War 11 by the British Army; they needed it as a lubricant because of its high erucic acid content (Carr 1990). The development of new rapeseed varieties, more suitable for human use, was undertaken in Germany and Canada because the climate of these countries is more suitable for the cultivation of rapeseed, but not for soybean. The first successful new variety was Canbra-rape (for details see Ackman 1984). The name was then abandoned after the company that had developed the variety adopted Canbra as their company name. The varieties that are mainly used today are known under the name Canola. In Germany, the first new types were approved for farming in autumn 1973; in the U.S., rapeseed with low erucic acid has been approved since 1985 (Sebastian 1985). Only 1.5% erucic acid was then left in the oil. Since 1977, the amount has been limited to 10% (of the oil) in the European Union and was further restricted to 5% in 1979. The latest Codex limits erucic acid content in low-erucic acid rape (LEAR) to 2%. In connection with the last revision, the Codex Committee refused to officially name low-erucic varieties Canola. A growing demand for oils with a high erucic acid level permits some countries to continue to grow HEAR (HEAR is priced higher than LEAR). Trace fatty acids in rape are reported by Sebedio and Ackman (1979) and Ackman and Sebedio (1981), for example (see also Table 2.6). The fatty acid composition is dependent on the temperature during growing as shown by Diepenbrock (1984). The latest development is double-zero rape, combining low erucic acid content with a low content of glucosinolates. The meal of these varieties is well suited for animal feed, whereas the old sorts could not be used for cattle and poultry.This develop ment has had great influence on the production volumes, especially in Europe (Table 4.42). The most recent trials have been done to cultivate triple-zero rape with the aim to also reduce its fiber content. Success here would further increase rapeseed’s importance. In 1994, the highest yields were reported from Algeria (6188 kgha), Belarus and Boznia Herzegovina (4OOO kgha each). Mexico is listed with a doubtful 11,333 kgha. The lowest in 1994 were Ethiopia (533 kgha), Estonia (667 kgha) and Bangladesh (710 kgha; see Table 4.43). The price of rape oil is close to that of soybean oil. TABLE 4.42
Rapeseed Production (-98% Used for Crushing; Crushing Oil Equivalent -41 %) Rapeseed (MMT)
1935
1950
1960
1970
1980
1989
1993
3.9
-
4.8 0.0
2.5 0.8
0.8
3.8 0.3 0.9 1.1 0.2
6.5 1.6 1.0 1.5 0.7
12.0 3.4 2.4 1.4 1.2
24.5 3.3 6.9 4.1 5.9
26.5 5.5 6.9 4.9 6.0
1994
1995
30.0 7.2 7.5 5.4 6.3
34.7 6.4 9.8 5.9 7.7
~
Total world Canada China PR India EU (10)
-
3.1
-
Fats and Oils Handbook
254
TABLE 4.43 Production Yield of Rapeseed Rapeseed (kg/ha) Total world Canada China PR India Denmark Germany FR France Italy Netherlands UK
1935
1950
1960
1970
1980
1990
1993
1994
1995
580
520 820
620 430
540 910 530 390
700 1010 360 490
1740 1090 980 2140
1470 1160 900 1900
969 1171 927 499 2105 2583 2359 2100 3207 2846
1409 1264 1317 826 3091 3002 2902 2415 3250 3156
1319 1335 1309 773 2543 2828 2840 2360 3250 2679
1312 1257 1296 856 2186 2649 2649 2084 2000 2549
1408 1221 1416 888 2353 2856 2856 2017 2500 2989
-
-
-
-
470 1620 2190 1450 1340 2700
-
-
2180 1780 1850 2910 2490
4.3.5.3 Composition and Properties of Rapeseed and Its Oil. Rapeseed has a relatively low hull content. In contrast to most other oilseeds, it is processed nondehulled (Fig. 4.76). The meal of the traditional varieties was restricted in its use for animal feed, whereas the new varieties, low in glucosinolates, have no limit at all. Breeding LEAR has lifted all restrictions on use of the oil (Figs. 4.77 and 4.78). In addition to the above-mentioned and the common fatty acids, rape oil may contain up to 2.0% behenic and up to 1.5% lignooeric acid. The content of arachidonic acid may account for 3.5%; in extreme cases it can be 12%. The disappearanceof erucic acid is also reflected in the triglycende composition (Figs. 4.79 and 4.80). Meanwhile there is further effort to develop new varieties because of the high linolenic acid content. Starting in France, where the linolenic acid content in oils for deep frying has been restricted to 2%, a need has arisen for new varieties m v o t et al. 1990) with a linolenic acid content <3%. The spectrum of higlycerides of such varieties shows that all triglyceride types containing linolenic acid are reduced and types
Fig 4.76. Composition of rapeseed.
Vegetable Fats and Oils
255
Fig. 4.77. Main fatty acid composition of HEAR rape oil.
LLeLe and OLeLe completely disappear in favor of OOL,which increases by 25%; linolenic acid is almost completely substituted by linoleic acid. Rape meals consist of one third protein with a favorable amino acid spectrum. The content of crude fiber (12%) is double that of soybeans, thus increasing the nondigestible part. After limiting the glucosinolates (S-content in traditional seeds
Fig. 4.78. Main fatty acid composition of LEAR rape oil.
Fats and Oils Handbook
256
Rapeseed oil Triglyosride tvr#
SOEr SErEr
OOEr ElOEr SOL
SLEr
OLEr
€En SLL SLeEr
Eru OLeEr ErLsEr Sue ErLLe ErLeLe LLLa Proportion [% Wrr
Fig. 4.79. Triglyceride composition of HEAR rapeseed oil (after Jurriens 1968).
-0.45%) in the new varieties (S-content in the seed < 0.2%),the meal can be better used; however, its energy content is 30%less than in soybean meal (Fig. 4.81). Animals eat the new meal much more quickly and completely, whereas the old varieties were left d i s h e d . It should not be used for the feeding of hens (production
000 POL
LOO POLn OOLn OLL PLLn OLLn LLL OLnLn LLLn Proportion [% m/rn
Fig. 4.80. Triglyceride composition of LEAR rapeseed oil.
Vegetable Fats and Oils
257
Fig. 4.81. Composition of expeller cake and extraction meal of rapeseed.
of brown eggs) because it can negatively influence the eggs’ taste. Double-zero rape also has such a high sinapin content that it is not suitable. The portion used in hen farming should not exceed 5%. Signoret and Vermeersch (1988) showed that meal from dehulled seed can be much better digested. It contains 5@%0 less cellulose, has a 15% higher energy content and delivers 20% more energy as a result of better digestibility. Dehulling is done by dropping the seed on a quickly rotating disk and removing the hulls by air separation. There has been no breakthrough yet for that process. 4.3.5.4 Harvest and Storage of Rapeseed. Today’s winter rape varieties are harvested 180-240 d after sowing compared with 85-125 d for summer rape. Ripening is signaled by browning of the stem and darkening of the pods. The seeds then rattle in the pod and have a moisture content of -15%. Harvest is done by combine harvesters (Table 4.44). There is a great danger of losing up to 30% of the seed if not enough care is taken. Losses of 5 1 0 % are normal. Seed with 8-9% humidity can be stored withTABLE 4.44 Seeding and Harvesting Periods for Rapeseed Jan
Feb
Mar
S
China Cerrnany France H
H
May H
s s
s s
H
H
Canada India
Apr
s
s
Sept
Oct Nov Dec
H H
H H
H H H
H
H
June July Aug H H H
H H H
H
H
S
H
H H H
258
Fats and Oils Handbook
out drying. Seeds with normal humidity between 10 and 15% have to be dried; otherwise, they substantially lose quality within 24 h even if stored at only 20°C. If storage is for only 1 mo, drying to 12% is sufficient; for longer periods and for transport, a humidity of 7-9% is necessary. Moisture contents <6% make the seeds rough and susceptible to damage. At 2% moisture content, the portion of broken seeds is 10 times higher than with 8% (Appelqvist and Ohlson 1972). Yields are as high as 3.5 tonha maximum. Breeders believe that new cultivations will yield up to 10 tonha. Figure 4.82 shows the processing of rapeseed. 4.3.5.5 Fact File of Rapeseed Oil. The fact file gives the fatty acid composition, the physical data as well 8s price development (Table 4.45, Figs. 4.83 and 4.84).
C&np.dl
(e4eummQ
Fig. 4.82. Flow chart of rapeseed oil production.
259
Vegetable Fats and Oils
TABLE 4.45 Fact File of Rapeseed Oil (LEAR) German: Rapsol
French: huile de colza
Spanish: aceite de colza
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter Crismer value Brassica sterol
(at 20°C;ref. water 20°C) (nD40) (mg KOH/g oil) Wijs method) (gkg oil)
0.914-0.920 1.465-1.467 182-1 93 110-126 <20
67-70 >5
(Yoof total sterols) Solidification point
Cloud point:
-10 to-12"c
Solids content at
("CpD
0/32
5/41
10150
20168
30186
35/95
(YO)
<1
0
0
0
0
0
World market price
Price index (1995average compared to average) 1 1 8% 10 years ago 1 16% 20 years ago 213% 25 years ago
<
(U.S. $/MT)
min
0
max
1970-1995
208
480
968
1967-1970 1970-1979 1980-1989 1990-1995
236 208 199 385
287 499 464 498
359 968 863 731
c 16:1
c 2o:o
Fig. 4.83. Fact file of rapeseed oil (fatty acid composition),
Fats and Oils Handbook
2 60
Fig. 4.84. World market price development of rape oil.
Further literature is given at the end of this chapter. The equivalent data for HEAR are as follows: density, 0.9 10-0.920; refractive index, 1.465-1.469; saponification number, 168-181; and iodine value, 94-120. The unsaponifiable matter is equal to the value for LEAR. At present, HEAR rape is sold with a price premium because demand is higher than supply. 4.3.6 Coconut Oil
4.3.6.7 Botany and History o f Coconuts. Coconut palms (COCOS uncifera) grow in a belt between 20’ north and 20” south of the Equator in regions with a yearly average temperature of almost 30°C. The area used comprises some 3.5 million hectares (Woodroof 1979). If the temperature falls below 20”C, the palm does not flourish. It grows in altitudes up to 1500 m (4500 ft). After 6-9 y, the 30-m (100-ft) high trees begin to carry nuts and, after 15-20 years (most profitable age), produce between 50 and 100 nuts per year; the palms carry blossoms and all stages of fruit at any time so that harvesting is done continuously throughout the year (Fig. 4.85). It appears that the plant has been used in India for >2500 years. In the literature of this region, it appears in 300 B.C. for the first time. The name “Coco” is the Spanish word for monkey or grotesque and was given to the nut around the year 1500. In 1820, the British captain Boyd brought coconuts to the UK. Initially, his business was not very successful, but later the fruit was cleverly marketed and became fashionable in Europe. That was also true for the fibers, which were regarded as chic and used as carpets in departmental stores (The Times 26.1.1832). In plantations, palms are planted at a distance of 8 m, thus allowing -150 treesha. The yield then is -10,OOO nuts per year, equivalent to 1.5-2.0 ton of coconut oilha. 4.3.6.2 Economic lmportance of Coconuts. With the colonization of Asia, the palm’s products quickly reached global distribution and importance. Dutch and
Vegetable Fats and Oils
261
Fig. 4.85. Coconut.
Portuguese colonists landed on Ceylon (today’s Sri Lanka) in 1740 and began to develop plantations. In 1842, 1 million palms were already planted; in 1860, it was 20 million, and for 1907, the estimate was that fruit from 60 million palms was harvested. For many islands in the Pacific, the coconut was the only source of income. Only because of the low absolute amount of nuts (caused by the small size of their territories), they do not appear in the production table (Table 4.46). At present, coconut production is -40 million. 4.3.6.3 Composition and Properties of Coconuts, Copra, and Coconut Oil. Coconuts weigh between 700 and 1500 g; they are covered by a fibrous tissue that accounts for up to 60% of their weight and that is removed after harvesting. The nut is TABLE 4.46 Copra Production (-1 00% Used for Crushing; Crushing Oil Equivalent -76%) Copra (MMT) Total world Philippines Indonesia India Malaysia CeylodSriLanka
1935
1950
1960
1970
1980
1989
1993
1994
1995
2.5 0.6 0.7 0.0
2.5 0.8 0.5 0.2
3.3 1.4 0.6 0.3
3.4 1.2 0.7 0.4
4.9 0.2 1.1 0.4
5.1 2.1 1.3 0.4
4.8
1.9 1.3 0.5
4.7 1.9 1.2 0.5
4.9 2.1 1.1 0.5
0.2
0.1
0.2
0.2
0.2
0.1
0.1
0.1
0.1
0.2
0.2
0.3
0.2
0.1
0.2
0.1
0.1
0.1
2 62
Fats and Oils Handbook
Coconuts
Fig. 4.86. Composition of coconuts.
then cut open (an experienced worker can open up to 2000 nuts/d) and the kernel, amounting to -2040%, of the whole nut’s weight, is taken out and dried (Fig. 4.86). This yields the so-called copra, which has a fat content between 60 and 70%. Depending on the species, 4000-6000 nuts are needed to produce one ton of copra. Copra is usually sun dried. Often, however, it is dried over an open fire with the fibers used as fuel material. Therefore, the crude fat has to be analyzed for its content of polycyclic hydrocarbons before it is bought by the manufacturers of shortenings or white fats. Because of its high lauric acid content (up to 52%), coconut oil belongs to the group of so-called laurics. The iodine value of the oil shows that it contains ~ 1 0 % unsaturated fatty acids. Solidification takes place at 18-23°C. Melting occurs in a very small temperature range so that the heat of melting is very quickly needed and consumed, thus producing a cooling effect in the mouth. In addition to the fatty acids mentioned in Figure 4.87, coconut oil can contain up to 0.3% (in rare cases 1%) capronic acid and up to 1.5% arachic acid. Its triglycerides do not contain more than one double bond (Fig. 4.88).
Vegetable Fats and Oils
2 63
Fig. 4.87. Main fatty acid composition of coconut oil.
Coconut cake and its meal have been used as fodder for cattle for over 100 years. The crude fiber content of 13-15% is quite high, which is compensated for by the fact that the other components can very easily be digested. An earlier concern that feeding coconut cake might negatively influence milk quality was disproved (Fig. 4.89).
Fig. 4.88. Triglyceride composition of coconut oil.
Fats and Oils Handbook
2 64
Fig. 4.89. Composition of expeller cake and extraction meal of copra.
4.3.6.4 Harvest and Storage of Coconuts. Harvesting is usually done -1 mo before ripeness, i.e., -1 1 mo after pollination of the blossom. The nuts are cut off in plantations or collected from the ground on the Pacific islands. The palm carries fruit for 60 y. Copra should have a moisture of 7% maximum. If relative humidity is high (>85% at t = 28.5 f 3.5'C and >95% at t = 40°C), there is a danger that the nuts or the copra could acquire mold infections (Salunkhe and Desai 1986). The growth rate of the molds depends on the moisture content. Child (1974) describes the dependency as follows:
H20 c 7%
green molds
8%c H20 c 2%
brown and yellow molds
H2O > 12%
black molds
(Aspergillus niger)
H2O >> 12%
white molds
(Rhizopus species)
(Penicillium glaucum, Aspergillus glaucus)
-
(various Aspergilli)
Graalmann (1990) reports that in 1987/88, 40% of the Philippine harvest had to be rejected because the aflatoxin B1-content was above the German limit. Following that, there was considerable investment in dryers to avoid such disasters in the future. The method of harvesting does not greatly influence the commercial benefit that can be drawn from the fruit. Nambiar (1983) describes a novel process that is said to have a 10 times higher yield. In this process, the nuts are carefully opened
265
Vegetable Fats and Oils
aCJuIlhg (5.2.1.1)
siu dudion (5.2.1.3)
I.
blla
PHCiar
Mnd pnuino (5 2 2)
PlUpmukq (6 2.2)
li
r
Cnrdo coconut dl
Fig. 4.90. Flow chart of coconut oil production. and the milk is collected and separated into oil and protein. Figure 4.90 shows a flow diagram of coconut processing. 4.6.3.5 Fact File of Coconut Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.47, Figs. 4.91 and 4.92). Further literature is given at the end of this chapter.
Fats and Oils Handbook
266
TABLE 4.47 Fact File of Coconut Oil ~~~
~~
German: Kokosfett
French: huile de coco
Spanish: aceite de coco
Relative density Refractive index Saponificationvalue Iodine value Reichert value Polenske value Unsaponifiable matter
(at 2ooC; ref. water 20°C)
0.908-0.921 1.448-1.450 248-265 6-1 1 6-8.5 13-1 8 4 5
(nD40) (mg KOH/goil) Wijs method)
(fig oil)
Melting point:
20-28oC
Solidification point
Solids content at
(VF)
0132
10150
20168
25/77
30186
35/95
(YO)
>95
81
64
5
0
0
World market price
Price index (1995 average compared to average) 10 years ago 112% 167% 20 years ago 30 years ago 2 1 0%
1a 2 3 o c
(U.S. $/MTJ
min
0
max
1963-1995
144
501
1433
1963-1 969 1970-1979 1980-1989 1990-1995
144 188 220 275
293 532 598 498
41 1 1224 1433 755
-
propom [%I
Fatty pcid
-
0.4 0.8 5.0 10.0 4.5 8.0 4 . 0 51.0 18.0 -21.0 7.5 10.0 2.0 4.0 6.0 10.0 1.0 2.5 0.6
Cspronc C.~tylic cspric LSIJ~C Myrhtk Palmltic Stbark
C8:O C 8:O c lo:o C 120 C 14:O C 18:O C l8:O obic c 18:l Un&k C 1 8 2 C18:3 C24:l
-
-
-
propom WI
Fig. 4.91, Fact file of coconut oil (fatty acid composition).
4.3.7 Sesame Oil 4.3.7.7 Botany a n d History of Sesame. It has been proven that sesame (Sesamum indicum; Sesamum orientale) was already used by the Persians around 2100 B.C.;the assumption is that it had been in use since about 4000 B.C.Sesame was of immense importance. King Sargon 11, for example, introduced price control and paid out wages partly in sesame seed (Burkhill 1953). The plant was well known to all cultures in Asia and was later exported to other continents. The well-
Vegetable Fats and Oils
267
Fig. 4.92. World market price development of coconut oil. known saying “Open sesame” is derived from the plant and was an invocation to make the pod burst and release the seed. At all times, the oil has also been used as a remedy, especially for intestinal problems. Cosmetic use is also reported. The Greek goddess Hera rubbed herself from head to foot with sesame oil before she seduced the god Zeus (Homer, Iliad). A report from the times before our modem oil production in oil mills was given by Napoleon (war in Egypt, beginning of the 19th century). At that time, the seeds were soaked in water, then roasted for some hours, crushed between milling stones and subsequently extracted by means of lever presses. Today sesame is cultivated mainly in India and China, but also in Sudan and Mexico. The plant requires a temperature of 20°C in the beginning of its development, some humidity during growing, and dry weather during ripening. It can be sowed to altitudes of 1200 m (4000 ft) if a frost-free period of at least 5 mo is guaranteed. Sesame flowers after 45 d, and its oil forms between d 12 and 24 of maturation (Fig. 4.93). Normally, a sesame plant reaches aheight of 6CL120 cm and bears its seeds in capsules 2.5-8.0 cm length with a diameter between 0.5 and 2.0 cm. The thousandseed weight is 4-8 g of white to brownish seeds that are 4 mm long, 2 mm wide and 1 mm thick. 4.3.7.2 Economic lmportance of Sesame. In contrast to the other oilseeds, the main cultivation areas lie outside Europe and the Americas, where the oil is rarely found (Table 4.48). Sesame seed belongs to the high-fat seeds with more than 50% of its dry matter being oil. The yields are low because it is grown mainly in nonindustrialized regions or countries. On small farms, a yield of 300 kgha is normal; the highest yields reported
Fats and Oils Handbook
2 68
Fig. 4.93. Sesame. are 10 times that. The highest yields recorded in 1994 were from Ethiopia (3846 kgha), Israel (1515 kgha) and Lebanon (1455 kgha); the minimum yields were from Sudan, Guinea and Chad (197, 200 and 243 kgha, respectively; Table 4.49). The plant is regarded as risky for farmers because exceptionally low yields can be caused by too much rain; there can also be too much variation in ripeness times TABLE 4.48 Sesame Seed Production (-65% Used for Crushing; Crushing Oil Equivalent -43%) Sesarneseed(MMT)
1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world India China PR Mexico Sudan
1.60 0.40 0.85 0.02 0.03
1.78 0.40 0.83 0.07 0.13
1.44 0.37 0.29 0.12 0.18
1.87 0.44 0.36 0.25 0.20
2.60 0.49 0.45 0.16 0.25
2.35 0.55 0.42 0.07 0.07
2.32 0.57 0.56 0.04 0.18
2.66 0.84 0.54 0.05 0.17
2.76 0.93 0.54 0.05 0.20
TABLE 4.49 Production Yield of Sesame Seed Sesameseed (kglha)
1935
1950
1960
1970
1980
1989
1993
1994
1995
Total world India , China PR Mexico Sudan
360 240 590 420 320
360 200 560 490 670
290 150
330 180 410 830 400
303 185 484 586 286
339 250 583 592 138
342 260 704 930 142
373 340 913 980 126
351 343 900 962 125
-
640 430
Vegetable Fats and Oils
269
Fig. 4.94. Composition of sesame seed.
of the individual capsules or easy bursting of the capsules during harvest. The oil is very expensive so that it is rarely traded worldwide and is used mainly in the countries of production. 4.3.7.3 Composition and Properties of Sesame Seed and Its Oil. Figure 4.94 shows the composition of sesame seed. The oil consists of >75% unsaturated fatty acids, with almost equal portions of oleic and linoleic acid (Fig. 4.95). The solidification point is -3 to -6"C, and the iodine value ranges from 104 to 120. Sesame oil may contain 0.5% palmitoleic acid and up to 0.1% (in special cases 0.9%) of
Fig. 4.95. Main fatty acid composition of sesame seed oil.
Fats and Oils Handbook
2 70
myristic acid. As can be predicted from the fatty acid composition, more than 60% of the triglycerides of sesame oil contain four or more double bonds (Fig. 4.96). The nontriglyceride components of the seed serve as fodder. They contain 35% protein. The plant itself is of no value and is plowed under, at least in largescale farming. Apart from the ash content, sesame meal is very similar to soybean meal (Fig. 4.97). The amount of meal fed to milk cows should be restricted to 1.2 kg/d to prevent a decrease in milk quality due to the carry over of fatty acids. Because the price is high, livestock feeding is rarely done. However, it is used to feed deer because it helps in the development of beautiful antlers. For human nutrition, the meal is of no use because the bitter hull cannot be satisfactorily separated. 4.3.7.4 Harvest and Storage of Sesame Seed. Harvest takes place approximately 100-110 d after sowing (Weiss 1983) with new cultivations after 70-75 d (Mantilla 1977).When harvested, the upper capsules are not yet ripe, but ripen postharvest during drying (Table 4.50). After drying, the seed is threshed. It can also be harvested by means of a combine harvester. Great care has to be taken then not to squeeze the seed. Figure 4.98 shows a processing flow chart.
Sesame oil TriglY-m type POP POS
Po0 SO0 PLP PLS
OOO PLO SOL SLO POL
OOL OLO SLL PLL LOL POLL OLL UL Proportion [% m/n
Fig. 4.96. Triglyceride composition of sesame oil (after Ouedraogo and Bezand 19811.
Vegetable Fats and Oils
Fig. 4.97. Composition of expeller cake and extraction meal of sesame seed.
Fig. 4.98. Flow chart of sesame seed oil production.
271
Fats and Oils Handbook
2 72
TABLE 4.50 Seeding and Harvesting Periods for Sesame Seed Jan
Feb
Mar
Apr
May
June July
s
India China Mexico Sudan
S S
H H
s
s
H
H H S
Aug
Sept
H
H H H
Oct Nov Dec
H H H H
H H H H
H
H H
TABLE 4.51 Fact File of Sesame Oil ~~
~~
~
German: Sesamol
French: huile de sesame
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 20°C; ref. water 200C) (nD40) (mg KOH/g oil) W i j s method) (fig oil)
Melting point:
-"C
Solids content at
("(3°F)
0132
514 1
20168
(O/O)
<1.2
<0.5
0
Spanish: aceite de sesame 0.91 54.923 1.465-1.469 187-1 95 104-1 20 <20
Solidification point 30186
-3 to doc 35/95
0 '
0
World market Drice per MT (mid-1995) -3500 U.S. $
Sesame oil Fatty acid Pabnltic Palmitobic Stearic
Proportion [%I
C 16:O C 16:l C 160
7.0 3.5 35.0 35.0
- 12.0 < 0.5 6.0 50.0 50.0 < 1.0 < 1.0 < 0.5
-
-
IProportion [%I I Fig. 4.99. Fact file of sesame oil (fatty acid composition).
4.3.7.3 Fact File of Sesame Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.51,Fig. 4.99).Further literature is given at the end of this chapter.
Vegetable Fats and Oils
273
TABLE 4.52 Palm Kernel Production (-1 00% Used for Crushing; Crushing Oil Equivalent -45%) Palm kernels(MMT)
1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world Malaysia Nigeria Indonesia
0.71
0.83
-
-
0.95 0.02 0.43 0.03
0.91 0.09 0.30 0.05
1.47 0.53 0.29 0.13
3.47 1.85 0.33 0.43
4.34 2.27 0.39 0.82
4.35 2.20 0.38 0.95
4.79 2.40 0.40 1.08
4.3.8 Palm Kernel Oil 4.3.8.7 Botany of the Oil Palm Nuts. Palm kernel oil is extracted from the seeds (nuts) of the oil palm (see Chapter 4.2.1). The fruit bunches have a weight of 50-65 kg. Up to 2000 nuts can be separated from it, accounting for 10-15% of the bunch’s weight. They are brown, oval, between 1 and 2 cm long and have a shell that is as hard as stone. The thousand-seed weight is 6-10 kg. For further processing, they are dried at 60°C and then opened mechanically. Thus the dark brown kernels of hazelnut size, containing 4 5 0 % oil, are obtained. 4.3.8.2 Economic Importance of Palm Kernel Oil. Production has shifted from Africa to Asia. With that change came the shift in importance to new varieties that have a higher portion of pulp and fewer nuts (Table 4.52). Coconut oil and palm kernel oil can almost completely substitute for each other. Therefore, to a certain extent, their prices are coupled. The amount of palm kernel oil decreases relative to palm oil as more and more new varieties with lower nut contents are grown. Worldwide production of palm kernels in 1994 was 4.35 MMT, of which more than two thirds was from five Asian countries. 4.3.8.3 Composition and Properties of Palm Kernels and Their Oil. Although the nuts account for -45% of the fruit’s weight for African oil palm, it is only -7% for the more recent Asian varieties (Fig. 4.100). The aim is to breed new seedless
Fig. 4.100. Composition of palm kernels.
2 74
Fats and Oils Handbook
Fig. 4.101. Main fatty acid composition palm kernel oil.
varieties so that only the oil of the pulp is extracted (see also Chapter 4.2.1). Heavy promotion of the palm's use and the higher yield of the Asian species shifted the center of activity in palm oil production from Africa to southeast Asia; of course, palm kernel oil production is coupled to it. Palm kernel oil (or in moderate climate, palm kernel fat) solidifies between 20 and 24'C and is highly saturated (Fig. 4.101) with an iodine value of 13-23. The proportion of saturated fatty acids is >go%, with the most prominent being lauric acid; therefore palm kernel oil belongs to the group of lauric oils. The proportion of lauric oil in the total oil rises to a maximum after 14 wk of ripening of the fruit bunch. Palmitic, stearic, oleic and linoleic acid that constituted 80% of the total 10 wk after frutification are then reduced to 20% (Hartley 1957). In addition to the above, the minor fatty acids include up to 1.9% arachic acid and <0.6% palmitoleic acid. Of the higlycerides of palm kernel oil, 99% contain at least one molecule of lauric acid (La in Fig. 4.102). The expelled palm kernel cake is not very cohesive and is therefore usually sold as flour. Although its protein content of 17-19% is the lowest of all oilseed meals, it is well accepted as animal feed. In spite of this low protein content and an equally high content of crude fibers that do not add to the caloric value, it is very suitable for use as dairy fodder (Fig. 4.103). 4.3.8.4 Harvest and Storage of the Palm Nuts and Extraction of the Oil. Unlike palm oil, which is a pulp oil, palm kernels do not have to be processed close to the plantation. They are extremely hard and can be transported and stored without risk. Despite that, oil production is usually in the country of origin.
Vegetable Fats and Oils
2 75
Palm kernel oil Tligly-W tyl#
CalPlP CaLaLa, C a w LalPP, LlMM LaLaLa, CaLaM Law MMM LaPS, MPP, MMS MOP ppo
POS
sos LOO, OLaO
Fig. 4.102. Triglyceride composition of palm kernel oil (after Johansson and Bergenstahl 1995).
Palm fruit are harvested all year round. Because the fruit does not ripen symetrically, the timing of harvest must be given attention. When the major part of the fruit is ripe, part of the fruit is already ovempe and the top is not yet ripe. The fruit bunches are cut off with knives, collected and directly transported to the local m i l l s for processing. Figure 4.104 shows the processing steps of palm kernel oil production.
Fig. 4.103. Composition of expeller cake and extraction meal of palm kernels.
Fats and Oils Handbook
276
j*
-10 h, moMum C7%
Fig. 4.104. Flow chart of palm kernel oil production.
4.3.8.5 Fact File of Palm Kernel Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.53,Fig. 4.105). Further literature is given at the end of this chapter. 4.3.9 Linseed Oil 4.3.9.1 Botany and History of Linseed. Flax is a plant 60-120 cm in height and is most likely one of the oldest cultivated plants. Mummies from as early as 2000 B.C. have been found wrapped in linen. In a pyramid, linseeds from the period around 3500 B.C. have been discovered. Linseed came to Europe around the first century and from there was taken to America by the first settlers. Once cotton could be cheaply imported into Europe and cultivation began in the U.S., the importance of flax quickly
Vegetable Fats and Oils
277
TABLE 4.53 Fact File of Palm Kernel Oil German: Palmkernfett
French: huile de palmiste
Spanish: aceite de palmiste
Relative density Refractive index Saponification value Iodine value Reichert value Polenske value Unsaponifiable matter
(at 40°C; ref. water 20°C) (nD40) (mg KOH/g oil) Wijs method)
0.899-0.914 1.448-1.452 23G254 1420 4-7 8-1 2 <10
(gkg oil)
Melting point:
25-3OOC
Solids content at
("CPF)
10/50
15/59
Solidification point
20/68
25/77
30/86
35/95
(Old
70
59
39
17
0.5
0
20-24T
World market price
(U.S. $/MT)
min
0
max
Price index (1 990 average compared to average)
1972-1 995
21 6
589
1322
10 years ago 15 years ago
1972-1 979 198Cb1989
21 8 216
607 575
1322 1232
97% 103%
Palm kernel oil Propodton[%I
Fsnv Caprok Caprylic copric Lsurlc
C 6:O
Myrhtk
C14:O C18:O c 180
Pshnltk
Wric
c 8:O c 1o:o c 12:o
2.4 2.6 41.0 15.0 8.5 1.3 12.0 1.0
*
-
-
0.8 6.2 5.0 55.0 18.0 10.0 3.0 19.0 3.5
Fig. 4.105. Fact file of palm kernel oil (fatty acid composition).
decreased. Today, in some parts of Europe, there is a revival triggered by the Green movement and promoted by new varieties. Linseed requires mean temperatures of 18-21°C. In warmer regions such as India, it is a winter crop because too high temperatures lead to plant diseases that do not occur at lower temperatures. After fading of the white to blue-violet flowers, a 6- to 8-mm capsule develops that holds the shiny deep brown seeds in two chambers of two seeds each (Fig.
4.106; for seed composition, see Fig. 4.107). The seeds have a long, oval shape and are -4 mm in length. Depending on whether the plant is cultivated for the flax
Fats and Oils Handbook
2 78
Fig. 4.106. Linseed in bloom and seed forms (photo: Schuster 1992; courtesy of DLG Verlag, Frankfurt.)
Fig. 4.107. Composition of linseed.
fibers or for the oil, different species are cultivated. The variety Linum usifutissimum is grown mainly for oil production and is usually only 60 cm tall. 4.3.9.2 Economic Importance of Linseed. In the past few decades, linseed production shifted from its mother country India to the U.S. and Canada (Table 4.54). In 1994, the highest yields were reported from Mexico, China and Tunisia (3000, 2625 and 2136g/ha, respectively); Lithuania, the Russian Federation and Belamssia (125, 135,222 kgha, respectively) showed the lowest production (Table 4.55). TABLE 4.54 Linseed Production (-80% Used for Crushing; Crushing Oil Equivalent -34%) Linseed (MMT) Total world Argentina Canada
us. USSR India EU (10)
1935
1950
1960
1970
1980
1990
1993
1994
1995
2.7
2.9
-
-
0.03 0.21 0.84 0.43
0.21 1.17
3.1 0.83 0.45 0.54 0.40 0.45 0.06
3.9 0.78 0.70 0.89 0.45 0.47 0.05
2.9 0.83 0.81 0.33 0.25 0.27 0.05
2.6 0.44 0.94 0.10 0.20 0.34 0.10
2.09 0.11 0.63 0.09
2.51 0.15 0.96 0.07
2.65 0.14 0.10 0.06
-
0.41
-
-
-
-
0.27 0.28
0.32 0.37
0.43 0.27
Vegetable Fats and Oils
2 79
TABLE 4.55 Production Yield of Linseed Linseed (kgha)
1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world Argentina Canada
450 660 270 420 290
520 620 560 630 250
410 590 560 570 190 220
560 870 910 650 340 240
450 766 893 794 183 225
593 733 1291 947 185 290
753 792 1240 1144 305
867 996 1334 1072 353
825 928 1282 944
us. USSR India
-
386
4.3.9.3 Composition and Properties of Linseed and Its Oil. Linseed contains -34% fat and 23% crude protein. The oil is one of the rare sources of linolenic acid with an average proportion of >50%. In addition to the main fatty acids shown in Figure 4.108, it contains 0.2-1.0% arachic acid, 0.5% behenic acid and traces of myristic acid. The oil is highly unsaturated with an iodine value of 170-200 and a solidification point of -25 to -20°C. Linseed oil is used mainly in the chemical and pharmaceutical industries and for paint production. It belongs to the drying oils, which means that it can polymerize quickly in air. In Europe, it has only minor importance as food. Around the German capital Berlin, for example, linseed oil is eaten as a specialty item. In India, however, 40% of the oil produced is for human consumption. This may change with the new varieties (called for instance linola) that contain very low proportions of linolenic acid. The fatty acid composition explains why more than half the triglycerides of linseed oil contain a molecule of linolenic acid and almost half of them house four or more double bonds (Fig. 4.109).
Fig. 4.108. Main fatty acid composition of linseed oil.
7
2 80
LSL,
Fats and Oils Handbook
su
L e u , SLaS OLLe, LOL.. OLeL
OLELO, Ldxs
ptoportbn I% MI
Fig. 4.109. Triglyceride composition of linseed oil (after Hilditch and Williams 1964).
Pigs can be fed linseed cake only in limited amounts because its lysine content is very low. For cattle, however, it is very well suited because the protein content of -35% is quite high (Fig. 4.110). Attention has to be paid to a glycoside in linseed meal that holds bound hydrocyanic acid. This is enriched in the germ and can be set free if appropriate conditions are provided (water, t 37"C,enzyme emulsine). Linseed cake with >250 mgkg hydrocyanic acid should not be used as fodder (Lennerts 1984). The rest of the plant is also used. For that,the flax straw is bound into bundles for fermentation and either placed in water for 4 d or cooked in a soda solution, after which it is washed and dried. The fibers are then drawn manually or separated by machines. The straw yields 20-25% fibers.The chaff is used as dry fodder.
-
4.3.9.4 Harvest and Storage of Linseed and Extraction of the Oil. The capsules are harvested when 90% of them are ripe. In industrialized countries, the
Fig. 4.1 10. Composition of expeller cake and extraction meal of linseed.
281
Vegetable Fats and Oils
TABLE 4.56 Harvesting Periods for Linseed Jan Argentina Canada
Feb
Mar
May
June July Aug
Sept
Oct Nov Dec
H
H
us. USSR India
Apr
H
H
H
H
H
H
H
H
H H
H
H H
process is mechanized. In India, much of the linseed is still threshed by stamping oxen. In this case, most of the fibers are so heavily damaged that they are of no further use. Flax delivers -75% straw and 12.5% each of chaff and seeds. Table 4.56 shows the harvest periods for linseed. The proportion of oil in the seed increases from the 10th to the 35th day after flowering; it progresses by leaps during the first 7 d of oil production and then rises constantly from 2.5 to 35%. Figure 4.1 11 shows the processing diagram for linseed oil production. Fd SmM -34% Dlyhg(4.1.4)
Uo#un40.5%
8 Rb&&n
(5.2.1.3)
CodUmhg (5.2.1.4)
to 1R- 1B
5&7S’C, -30 mk, mowln 7-7.596 (~~IT&IY M d W condlgonhg)
Fig. 4.111. Flow chart of linseed oil production.
Fats and Oils Handbook
2 a2
TABLE 4.57 Fact File of Linseed Oil German: Leinol
French: huile de lin
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 20°C; ref. water 20°C) (nD40) (mg KOH/g oil) (Wijs method) (fig oil)
Spanish: aceite de linaza 0.91 4-0.922 1.472-1.475 188-1 96 169-1 96 7-1 5
Melting point:
-"C
Solidification point
Solids content at
("0°F)
0/32
5/41
20/6a
30186
35/95
(%)
1.5
<1
0
0
0
World market price
Fatty acid
-1 8 to -27°C
(US. $/MT)
min
0
max
1990-1994
340
514
a25
Proportion [%I
IPropomon [%I I Fig. 4.112. Fact file of linseed oil (fatty acid composition).
4.3.9.5 Fact File of Linseed Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.57, Fig. 4.112). Further literature is given at the end of this chapter. 4.3.10 SafflowerSeed Oil
4.3.70.7 Botany and History of Safflower.
Safflower seed is the seed of Carthamus tinctorius, which has been grown for a long time for oil production and as the botanical Latin name suggests, for coloring purposes. The coloring matter arises from carthamin and iso-carthamin (C21H22011 x H20). Like cotton, which lost its importance with the development of artificial fabrics, safflower's importance vanished with the invention of aniline colors. Safflower was already well known to the old Egyptians. It was identified in 1887 by Schweinfurth as one of the holy gifts to the mummy of pharaoh Amenophis I (1600 B.c.).The importance of safflower is illustrated by the fact that only the Pharaoh himself had the right to grow and market safflower. In Europe, safflower was frst mentioned by the German philosopher, Albertus Magnus, around the year 1200.
Vegetable Fats and Oils
283
Fig. 4.113. Safflower and safflower seed (photo: Schuster 1992; courtesy of DLC Verlag, FranMu rt).
A fatty acid composition of >75% linoleic acid gives safflower oil a great qualitative importance. Quantitatively, however, it is small and not only because of the high price. Depending on the planting density, safflower grows very branched or unbranched. It prefers temperatures of 24-32°C; -70 days after sowing, it begins to flourish. Seed formation begins 30 d later, and in another 20 d, the plant is ripe for harvesting. The roots of the safflower reach 2-3 m deep; its height varies between 50 and 200 cm, depending on variety and climatic conditions (Fig. 4.1 13). Safflower seeds are 6 1 0 mm in length and resemble those of the sunflower, but with a thicker hull. The yield is 1000-2500 seeds per plant. Earlier varieties had a hull content of some 70%; in recent varieties, this has been reduced to 45%. Because of the enormous proportion of hulls and the fact that the meal has no value at all, interest in safflower will remain limited. However, as a source of high-linoleic acid oil (highPUFA oil), it will be the plant of choice unless new breeds of other plants come up with similar contents. 4.3.10.2 Economic Importance of Safflower. The importance of safflower is in its linoleic acid content, which is required for products with high-PUFA claims. The amount produced is very limited (Table 4.58). The highest yield in 1994 was reported for Argentina (2667 kgha), the lowest for Pakistan (500 kgha). 4.3.7 0.3 Composition and Properties of Safflower Seed and Its Oil. Almost 50% of safflower seed is hull (Fig. 4.114). Where the oil is concerned, one could almost speak about single-acid triglycerides because linoleic acid makes up almost 80% of the fatty acids (Fig. 4.115). In addition to the main fatty acids, traces of linolenic acid (in special varieties up to 3%) and up to 1.5% myristic acid can be found. Because of the high proportion of linoleic acid, almost 90% of all triglycerides contain four double bonds or more, and more than half of it is trilinoleate (Fig. 4.1 16).
Fats and Oils Handbook
284
TABLE 4.58 Safflower Seed Production and Production Yield (-100% Used for Crushing; Crushing Oil Equivalent -1 7%) ~~
Production (MMT)
Production yield (kgha)
Safflower seed
1970
1980
1990
1995
1970
1980
1990
1995
Total world Mexico
0.6 0.25
1.0 0.58
0.9 0.16 0.49 0.17 0.01
0.9 0.11 0.46 0.19 0.01
680
693 1102 381 1267
720 900 549 1786 -708
808 1161 606 1984 700
India
us.
EU (10)
0.13
0.19
0.19
0.14 0.01
-
-
-
Fig. 4.115. Main fatty acid composition of safflower seed oil.
Vegetable Fats and Oils
285
Fig. 4.1 16. Triglyceride composition of safflower seed oil (after Jurriens 1968).
4.3.10.4 Harvest and Storage of Safflower Seed and Extraction of the Oil. The plant is harvested with combines -35-40 days after flowering when it is not yet totally dried (the outer leaves of the corolla are then brown). The moisture content of the seed must not exceed 8% (small storage facilities) and would be better at -5% (essential for silo storage); seeds with higher moisture must be dried. Usually the seed is not stored, but harvest dates are coordinated with the oil mills. The seed is partially dehulled; the hulls are used in the cellulose industry or for the production of insulating material. Its expeller cake and extraction meal are relatively rich in protein (Fig. 4.117). Because of the high portion of hulls, safflower seed contains only 15% oil. Figure 4.1 18 shows the production diagram of safflower seed oil extraction. 4.3.10.5 Fact File of Safflower Seed Oil. The fact file gives the fatty acid composition, the physical data as well as price development (Table 4.59, Fig. 4.119). Further literature is given at the end of this chapter. 6050
40-
30-
a m0 Wmtm
Rotah
Fat
Fiber
Kfm exbrct
Aeh
Fig. 4.1 17. Composition of expeller cake and extraction meal of safflower seed.
Fats and Oils Handbook
2 86
I
Urblctbn (5 2 3)
,,
I
B
t
I
I
Extmdbn mal
C r u d e ~ ~ o i l
Fig. 4.1 18. Flow chart of safflower seed oil production. TABLE 4.59 Fact File of Safflower Oil German: Distelol, SafloroI
French: huile de carthame
Spanish: aceite de cartamo
Relative density Refractive index Saponification value Iodine value UnsaDonifiable matter
(at 20°C; ref. water 20°C)
0.922-0.927 1.467-1.470 186-1 98 130-1 50 45
Melting point
-"C
Solids content at
("VF)
i%)
(mg KOHIg oil) (Wijs method) (dkg oil) Solidification point
-1 3 to -20°C
0132
10150
20168
30186
35195
0
0
0
0
0
World market price (US. $IMT)
1991
1992
1993
1994
-880
-1280
-1580
-1260
Vegetable Fats and Oils
287
Safflower seed oil FanY add
Pmpom1 ~x1 2.0 -10.0 4 0.5 1.0 .10.0 7.0 -42.0 64.0 -81.0 < 1.0 0.5 < 0.5
P w m n PA1
Fig. 4.1 19. Fact file of safflower seed oil (fatty acid composition).
4.3.11 Cocoa Butter
4.3.1 7.1 Botany and History of Cocoa. The cocoa tree (Theobroma cacao) grows mainly in the tropical forests of Africa. The plant stems from Central America and was exported to Africa, which is now responsible for 75% of the world production. In the plantations, the tree is kept at a maximum height of 4 m by clipping. It delivers 20-50 pods that contain 35- 50 seeds each. The weight of a single dried seed is -1 g. 4.3.7 1.2 Economic importance of Cocoa. Cocoa butter, as the fat is called, becomes available during further processing of cocoa. Although a by-product only, it is very valuable. As early as 1809/10, there have been international congresses in Paris that dealt with the protection of cocoa products against imitation. In the year 1970, the world production of cocoa butter amounted to only 130,000 MT, a tiny amount compared with other oils and fats (Table 4.60). However, the cocoa product industry is only a small branch of the food industry, and cocoa butter can relatively easily be substituted by cheaper fats (see Chapter 6.2.3.5). Apart from its role in sweets, cocoa butter is also a source material in the pharmaceutical industry. The naine cocoa butter cannot be used for fat that is produced by the extraction of whole nondehulled cocoa beans; the name is protected for fat that is won by press extraction of cocoa powder. After the common frst pressing, yielding -75% of the fat of cocoa, a hard, partly deoiled mass remains that still contains 22-24% fat. Further vigorous pressing leads to cocoa powders with not >lo% fat remaining. TABLE 4.60 Cocoa Bean Production Cocoa beans (MMT)
1935
1950
1960
1970
1980
1990
1993
1994
Total world Ivory Coast Brazil Ghana Nigeria Ecuador Malaysia
0.72
0.77
1.20 0.09 0.16 0.44 0.20 0.04
1.35 0.15 0.18 0.39 0.22 0.07
1.70 0.43 0.33 0.27 0.17 0.08 0.04
2.47 0.75 0.40 0.30 0.16 0.40 0.26
2.50 0.80 0.34 0.24 0.14 0.08 0.23
2.56 0.81 0.34 0.27 0.14 0.08 0.23
-
0.12 0.28 0.09' 0.02
-
0.14 0.27 0.10 0.02
-
-
-
288
Fats and Oils Handbook
TABLE 4.61 Cocoa Bean Production Yield Cocoa beans (kgha)
1960
1970
1980
1990
1993
1994
Total world Ivory Coast Brazil Ghana Nigeria Ecuador Malaysia
126 105 150 450 215 45
150 240 200 380 215 90
358 529 689 223 241 300 801
464 714 571 333 229 290 969
454 61 8 464 240 337 251 624
439 505 475 264 338 255 62 7
-
-
Highest 1990 yields have been reported from Haiti (2273 kgha), Indonesia (1625 kgiha) and the Solomon Islands (1389 kgha); 4 y later, Haiti was down to 1111 kgha and Indonesia was down to 1167 kg/ha. The record yield of 1994 was that of Sierra Leone (1667 kgha). The lowest yield of all countries that reported to the FA0 came from Liberia (31 kgha), followed by the Central African Republic with only 45 kgha (Table 4.61). 4.3.1 1.3 Composition and Properties of Cocoa Seed and Its Oil. After fermentation, 32-47 kg of fermented dried crude cocoa beans are left from the initial lo00 kg of fresh fruit. The water content of the fresh beans (30-35%) increases during fermentation to -60% and reaches 5 7 % after drying. Then the beans are roasted. Fermented, roasted cocoa kernels reach a fat content of -60% (Fig. 4.120). Apart from the main fatty acids shown in Figure 4.121, up to 1% arachic acid, 0.2% myristic acid and 0.3% palmitoleic acid can be found. The iodine value lies between 34 and 40.The point of gravity of cocoa butter triglycerides is with three configurations that have in common a molecule of an unsaturated fatty acid (oleic acid in nine out of ten cases) in the 2-position. The 1- and 3-positions are occupied by palmitic and stearic acid, single or in combination (Fig. 4.122). After fermentation, the hulls are separated from the kernels by sucking them off. They contain 2 4 % fat that is extracted with hexane for nonedible purposes. Besides technical cocoa fat, the hulls also contain 0.8-1.2% theobromine, a compound needed in the pharmaceutical industry. To obtain this, the extraction meal of cocoa fat extraction is heated to 60°C and again extracted, this time with a mixture of dichloroethane and ethanol. The residue is cleared of extraction solvents and used in animal feeding. The fat extracted from the hulls has an iodine value of 35-65 and a melting point of 28-35°C. It contains >20% unsaponifiable matter (for a comparison: cocoa butter 0.348%). 4.3.11.4 Harvest and Storage, Fermentation of Cocoa and Cocoa Butter Production. After harvest, the beans are left in the pulp of the pod, fermented and
roasted. Only fruit that is ripe enough contains enough sugar for fermentation. The process is the only really successful way to remove the pulp that sticks firmly to the
Vegetable Fats and Oils
289
Fig. 4.120. Cocoa fruit and composition of cocoa beans (photo: courtesy of Karlshamns, Karlshamn.
seeds. Beyond that, flavors or flavor precursors build in the beans that further develop into flavors during drying and roasting. Fermentation takes 4-8 d, with intermixing required after 24-48 h. Unripe or broken beans are sorted out and the rest is dried in the air or in dryers. Cocoa butter production is schematically shown in Figure 4.123.
Fig. 4.1 21. Main fatty acid composition of cocoa butter.
Fats and Oils Handbook
290
MOP. MOS
Fig. 4.1 22. Tryglyceride composition of cocoa butter.
I
c
P
LFalmkn7 Y
4
Fig. 4.123. Flow chart of cocoa butter production.
291
Vegetable Fats and Oils
TABLE 4.62 Fact File of Cocoa Butter German: Kakaobutter
French: beurre de cacao
Spanish: manteca de cacao
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 15°C; ref. water 20°C) (nD40) (mg KOH/g oil) Wijs method) ( g k g oil)
0.945-0.976 1.456-1.458 19C-200 34-40 2 4
Melting point
32-36OC
Solids content at
("0°F) (Oh)
Solidification point 10/50
20/68
30/86
35/95
82
77
55
3
World market price per MT (mid-1995)
Cocoabutter
21-27OC
-3800 U.S. $
I Proportion [%I
Fatty acid
-
Linoleic Linolenic Arachic
22.6 30.4 0.1 0.5 30.2 36.0 29.2 36.4 C 18:2 1.3 4.0 < 0.5 C 18:3 < 1.2 C 20:O
-
I Proportion [%I I Fig. 4.1 24. Fact file of cocoa butter (fatty acid composition),
4.3.1 1.5 Fact File of Cocoa Butter. The fact file gives the fatty acid composition, the physical data as well as the world market price in 1990 (Table 4.62, Fig. 4.124). Further literature on cocoa and cocoa butter is given at the end of this chapter. 4.3.12 Corn Oil
Corn (Zea mays) is cultivated mainly in the temperate latitudes. It is rarely used for corn oil production. Oil is obtained from the germ, which is recovered during starch production (Fig. 4.125). Corn has very high yields (e.g., 8697 kgha in 1994 for the U.S.) that can be brought to records of 18,678 kg/ha (United Arab Emirates) by irrigation in warm climate. The germ from the corn flour industry contains -20% oil, that from the starch industry -50%. Because corn oil is a tiny by-product only, the worldwide tonnage is very limited (Table 4.63). Oil quality to a large extent depends on the pretreatment and the separation of the germ. The total amount of corn grown worldwide is -450 MMT.
Fats and Oils Handbook
2 92
Fig. 4.1 25. Corn. TABLE 4.63 Corn Oil Production ~~~~~
~
Corn oil (MMT)
1935
1950
1960
1970
1980
1990
1993
Total world
0.10
0.12
0.19
0.33
0.27
0.30
0.33
From Figure 4.126, it can be seen that corn has a total oil content of -6%, all of which is concentrated in its germ. Besides the main fatty acids (Fig. 4.127), it has up to 0.3%each of capric, myristic and palmitoleic acid as well as 0.4%each of arachic, arachidonic, behenic and lignoceric acid. Oils of the northern hemisphere contain 10-13% more linoleic acid than those from the southern. The iodine value is 100-135, and the solidification point lies below -10°C. Distribution of the fatty acids on the different triglycerides of corn oil shows that
Fig. 4.1 26. Composition of corn (maize).
Vegetable Fats and Oils
293
Fig. 4.127. Main fatty composition corn oil.
more than 65% of the triglycerides contain four or more double bonds; more than 40% even contain five or more (Fig. 4.128). Corn oil is regarded as a very stable oil. Depending on the source of the germ, the protein content of the cake can vary between 12 and 21%. Its digestibility is very good. In the market, mainly meal
Fig. 4.128. Triglyceride composition of corn (Strecker eta/. 1990).
Fats a n d Oils Handbook
294
Fig. 4.129. Composition of expeller cake and extraction meal of corn germ.
from solvent extraction can be found; however, it does not play a significant role (Fig. 4.129). The diagram shown in Figure 4.130 also shows the preceding process of starch manufacture. The fact file reports the fatty acid composition, physical data and price development (Fig. 4.13 1, Table 4.64). The low values for lauric and myristic acid given in the Codex Alimenturius can cause problems because unadulterated corn oils have been found that contained up to 0.3% of these acids. Portions that lie above these values suggest adulteration. More information on corn oil can be found in the literature given at the end of this chapter. 4.3.13 Olive Kernel Oil
Olive kernel oil is extracted from the kernels of olives (see Chapter 4.2.2),which contain -12%. Its composition is similar to the composition of olive (pulp) oil (Fig. 4.132). It is usually produced from the olive press cake. If pure olive kernel oil is wanted, the kernels have to be separated from the rest of the cake (rarely done). 4.3.14 Babassu Oil
4.3.14.1 Botany and History of the Babassu Palm. The babassu palm (Orbignya oleifera) grows mainly in some Brazilian provinces. Its lifetime is -200 y, and it begins to carry fruit after 8-10 y. The palm grows -20 m high and has leaves 6 m in length that are pinnated and strongly erect. Because they stand upwards at an angle of -25" to the stem, the plant can be recognized from a great distance. The fruit bunches are up to 100 cm in length and hold 200-600 fruit. They produce 1-6 bunches per year (Fig. 4.133). The fruits ripen between July and November, fall to the ground and are collected. The main harvest period is September-October. The 8-15 cm long and
Vegetable Fats and Oils
Corn
maize)
295
oii contents
5052’C, pH 3.5-4.0, -8 h
Water >>>
Oil contenl-48%
to water content < 50% In p m r
Watering
to water content < 3%, rnuttipb-hlbe dryer
EWadlon(523) I
I
I
CbrlRaUon
Evaporation of (5 2 3 3)
SObnt
!.
I CNde Maize (Corn) Oil
Fig. 4.130. Flow chart of corn oil production.
Corn oil (maize oil)
I Proportion [%I
Fatty acid
C 16 1
Palrnltoleic
Arachic
I
C 20 0
< 05
< 20 < 10 < 05 < 05
Fig. 4.1 31. Fact file of corn (fatty acid composition).
1-
Fats and Oils Handbook
296
TABLE 4.64 Fact File of Corn Oil (Maize Oil) _ _ _ _ _ _ ~ ~
~
German: M a i d Maiskeimol
French: huile de mais
Relative density Refractive index Saponificationvalue Iodine value Unsaponifiable matter
(at 20°C; ref. water 2oDc) (nDm) (mg KOHlg oil) (Wijs method) Cgncg oil)
Cloud point
--1 OOC
Solids content at
(VF)
0132
10150
(Yo)
<0.5
0
Spanish: aceite de maiz 0.91 0 4 . 9 2 5 1.465-1.468 187-1 95 103-1 28 <2 8
Solidification point
World market price
Price index (1 995 average compared with average) 10 years ago 106%
-1 0 to -1 8°C
20168
30186
35/95
0
0
0
( U S $lMT)
min
0
max
1982-1994
416
642
810
1982-1 989 1990-1995
41 6 540
61 6 678
91 1 810
5-9 cm thick babassu nut weighs 15CL200 g and contains 3-8 kernels. Up to 60% of it consists of a stone-hard shell that can be cracked only with immense effort. The first nuts that came to Europe reached a Liverpool harbor in 1867. Because the English were unable to crack the nuts, they threw them into the sea. The subspecies, the Cohune palm, grows in Yucatan and the adjacent Middle American region.
4.3.14.2 Economic Importance of Babassu. By common consent, the babassu palm represents a high potential source for fat. The estimate of this potential, how-
Fig. 4.132. Main fatty acid composition olive kernel oil.
Vegetable Fats and Oils
297
Fig. 4.133. Babassu nut. ever, differs extensively. Adames (1943) cited a number of 5 to 25 billion for Brazilian trees growing on an area of 13.4 million hectare. Up to 500 trees per hectare have been reported, but Adames’ estimate would mean 2000 trees per hectare. Given the whole area in which these trees could thrive, a more serious estimate is 2 W 3 0 0 trees per hectare, indicating that 2.5-3.5 billion trees would be more realistic. There are a lot of problems related to the utilization of that potential because the trees stand singly in the rain forest, mainly in regions that are not accessible to traffic. There are no plantations yet, and the yield is reported to be low if the trees are standing close to each other. In addition, the numbers that can be found in the literature on the yield per tree and the weight of the fruit bunches holding the nuts are very different and contradictory. Salunkhe and Desai (1980) describe the fruit bunches as consisting of 200-600 fruit with a total weight of 14-19 kg. However, when they give the weight of each single fruit as 150-200 g, a discrepancy occurs. The authors relate that the trees produce 1 4 bunches per year. Godin and Spensley (1971) report a yield of 1 tody. These figures are more consistent with the weight of the individual fruit and the number of nuts. They are confirmed by an ad hoc commission of the U.S. government (1975), which states the same number and reports 90 kg of kernels and a bunch weight of 14-90 kg. The authors mentioned first also make reference to reports of 20 k g h a yearly yield. Even if that is the weight of the kernels only and not that of the fruit, it must be incorrect regarding the given fruit weight and number of bunches. Lennerts (1984) reports that during the periods when fruit is ripe, the ground in some areas is covered up to 50 cm with nuts. That would stand for a much higher yield. Balick (1985) proposes 20 kg fruit per wild tree and 2000 kg annual yield per hectare. That would mean a plant density of 100 trees per hectare.
298
Fats and Oils Handbook
Although this seems to be on the low end, it would mean a potential of 27 MMT of fruit or 1.5 MMT of fat, provided it could be fully exploited. For cultivated trees, Balick mentions 7000 kg/ha, assuming 100 trees or 12,000 kg/ha for 120 treesha. This seems unlikely because common opinion is that the trees carry more fruit when standing less densely. Even disregarding this,fact, it seems difficult to believe that a 20% higher population of trees yields a 70% higher quantity of fruit. It seems that there are immense differences in opinion concerning babassu’s potential. One is well defined, namely, that it offers an enormous potential for Brazil. Assuming that the conservative numbers of the published estimates are true, the potential would still be 27 MMT of nuts, which is equivalent to 1.5 MMT of fat. To be optimistic, it could be much higher. A better utilization up to now is hampered by the difficult access to the regions with trees, by the fact that they grow wild and thus singly, by the difficulty in mechanization and the low oil yield of the nuts (see below). If the trees can be cultivated in plantations and the oil/shell ratio of the nuts can be improved, babassu will have a future. Regarding the production figures of babassu oil, it has to be taken into account that for the amount of kernel processed, a 12-fold amount of nuts, i.e., 3.3 MMT of nuts, have to be collected. The fat of the kernel is press or solvent extracted. The palm also delivers protein, wood of good quality and charcoal. 4.3.14.3 Composition and Properties of Babassu Nuts, Their Oil, and Extraction of the Oil. The kernel accounts for only 8-10% of the nut’s weight. It contains
60-70% fat, which means that the fat content of the whole nut is only 5-7% (Fig. 4.134). This creates a problem in that, for the production of one ton of babassu oil, more than the tenfold of stone-hard nut shells have to be removed and disposed. They are used directly as fuel or converted into coke and bumt afterward. In a side process, up to 17% furfural can beproduced. Babassu oil is similar to coconut oil. It contains >60% lauric and myristic acid and is only 17% unsaturated. The iodine value is between 10 and 18; the solidifica-
Fig. 4.134. Composition of babassu nuts.
Vegetable Fats and Oils
299
Fig. 4.135. Main fatty acid composition of babassu oil.
tion point is 21-23°C (Fig. 4.135). In addition to the fatty acids shown, babassu oil can contain up to 0.2% capronic acid. These fatty acids distribute as 63% trisaturated triglycerides, 30% monounsaturated ones and 7% di-olein-monosaturates (Jackson and Longenecker 1944). If no shell particles are present, babassu meal can be used similarly to coconut meal (Fig. 4.136). Fat extraction is similar to copra; however, cracking the nuts is very difficult (Fig. 4.137).
Fig. 4.136. Composition of expeller cake and extraction meal of babassu kernels.
Fats and Oils Handbook
3 00
I
Crudr babanu oil
e r r l u
Fig. 4.1 37. Flow chart of babassu oil production. 4.3.14.4 Fact File of Babassu Oil. The fact file of babassu oil shows its fatty acid composition, the physical data and the 1990 world market price (Table 4.65, Fig. 4.138). 4.3.15 Grape Seed Oil
The seeds of grape (Vitisuiniferu) contain 6% of oil in the dark varieties and 20% in the sweet white varieties. Because the seeds are the waste of wine pressing, grape seed oil is a by-product only (Table 4.66,Fig. 4.139). To extract the oil, the seeds are isolated from the husks and washed to remove carbohydrates and adherent pulp (Fig. 4.142).They are dried and then press or solvent extracted. Husk that has been distilled is no longer suitable for oil extraction. Grape seed oil is very heat stable, so that it is sometimes also used for industrial purposes. In addition to the main fatty acids shown in Fig. (4.140),grape seed oil contains up to 0.1% arachic, up to 0.6% palmitoleic and ~0.4%linolenic acid. On the whole, it is very similar to sunflower oil. The iodine number varies in the interval between 100 and 106.The extraction meal is suitable for animal feeding (Fig, 4.141),but it can also be burnt as a fuel substitute or used as fertilizer (Bernardini
Vegetable Fats and Oils
301
TABLE 4.65 Fact File of Babassu Oil German: Babassufett
French: beurre de babassu
Spanish: manteca de babasu
Relative density Refractive index Saponification value Iodine value Reichert value Polenske value Unsaponifiable matter
(at 2OOC; ref. water 20°C)
0.9144.91 7 1.448-1.451 2 45-2 56 10-18 4.5-6.5 8-1 0 c12
(mg KOH/g oil) Wijs method)
@kg oil)
Melting point
22-26OC
Solidification point
Solids content at
(VF)
10/50
20/68
30186
35/95
(Oh)
80
35
0
3
World market price per MT ex factory Brazil (mid-1995)
Myhtic Plhitic stboric Okic Linobk
95tL1000 U.S. $
I
Babassu oil
cspiylii Caprk Lauric
21-23OC
C8:O C 100 c 12:o C 14:O C 160 C 18:O c 18:1 C 182
-
2.6 6.3 1.2 7.6 40.0 -55.0 11.0 -27.0 5.2 11.0 1.8 7.4 9.0 -20.0 1.4 6.6
-
-
I proportion “I I Fig. 4.138. Fact file of babassu oil (fatty acid composition). 1985). The fact file (Table 4.67, Fig. 1.143) contains its fatty acid composition, the physical data, and the world market price of 1990. 4.3.16 Niger Seed Oil
Niger seed (Guizotiu ubyssinica) belongs to the same botanical family as sunflower. It stems from the Abyssinian highland. Since the 1940s, it has been grown TABLE 4.66 Amounts of Grape Seed Available in 1980a
1980 (MT) aSource: Bernadini (1985).
Italy
France
Spain
Argentina
150,000
70,000
5000
27,000
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Fats and Oils Handbook
Fig. 4.139. Grapes, grape seed, and composition of dried grape seed (photo: Schuster 1992; courtesy of DLG Verlag, Frankfurt).
Fig. 4.140. Main fatty acid composition of grape seed oil.
Vegetable Fats and Oils
303
Fig. 4.141. Composition of grape seed extraction meal.
in Germany, France and Switzerland. Today, the harvested amount is -400,000 tons per year. The plant can grow to 1.50 m in height, but usually remains el m. Its stem is 2 cm in diameter and is branched. It flourishes for 15-30 d with light yellow blossoms. The seeds are 3-5 mm long and 1.5 mm wide. The thousandseed weight lies between 3 and 5 g (Fig. 4.144). In addition to the main fatty acids (Fig. 4.145), niger seed oil can contain up to 1% arachic acid and in special varieties up to 3% linolenic acid. Oil production is almost identical to that for sunflower oil (see Chapter 4.3.3.5). The fact file shows the physical data (Table 4.68). 4.3.17 Borneo Tallow
Borneo tallow (also called illipB butter) draws its main importance from the fact that it is well suited as a source material for cocoa butter substitutes (see Chapter 6.2.3.5). Small portions also go into the cosmetics and detergent industries. The tree from the family of shoreae begins to develop fruit after 18-20 years. It mainly grows wild, and as the name already indicates, its main growing area is the island of Borneo. The production varies from year to year and is heavily dependent on the weather; for example, in a year of heavy rain, the areas in which the trees grow can scarcely be reached, and the nuts are flushed away. Often the trees grow in swamps or along river banks. One way to collect the floating nuts is to construct bamboo barricades that block their way down the rivers. It is said that the trees grown in plantations have a yield of 1100 kgha. The kernels contain 45-70% fat. To separate the kernels, the nut either has to be split mechanically or brought to germination. The shell is then removed manually. The cake from borne0 nut extraction can be fed. It resembles peanut meal, but with -10% less protein.
Fats and Oils Handbook
304
Grape bunches Removal of
-+
+
I
I
Extrsction (5.2.3) II
I
solvent (5.2.3.3) Condenrstion of extraction sotvent Extractknmeal
Crude grape seed oil
Fig. 4.142. Flow chart of grape seed oil production.
Borneo tallow has the fatty acid composition shown in Figure 4.146.In addition to the acids shown, up to 0.3% linolenic acid can be found, and in extreme cases, 2.8% linoleic acid. The iodine value is 30-38, and its solidification point lies between 22 and 30'C. The main types of triglycerides have one or two double bonds (Fig. 4.147).The fact file gives the physical data (Table 4.69).
Vegetable Fats and Oils
305
TABLE 4.67 Fact File of Crapeseed Oil German: Traubenkernol
French: huile de +pin de raisin
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter Erythrcdiols
(at 2WC; ref. water 20°C) (nD40) (mg KOH/g oil) (Wjs method) (gkg oil) (% of total sterols)
Melting point
0.923-0.926 1.473-1.477 188-194 13c-138 <20 <20
Solidification point
-"c
~~
~~
Solids content at
Spanish: aceite de pepita de uva
~
~
_
~~
-1 0 to -24°C _
_
_
~
(VF)
0/32
10150
20/68
30/86
35/95
(YO)
0
0
0
0
0
World market price per MT (mid-1995)
~
~
730-760 US. $
Grape wad oil
5.5 -11.0
Paknno*ic C 16:l wwic I c 18:o obit
unowc
c 1a:1
Cl82 C183
LinolenC AmMc
cm:o
Behdc
c2:o
3.0 12.0 58.0
-
0.0
-im
- 78.0
< 1.0 < 1.0
*opoma, b l
Fig. 4.143. Fact file of grape seed oil (fatty acid composition).
4.3.18 Walnut Oil
At present, walnut oil is fashionable in the gourmet kitchen. However, the amount is very small and it will stay a specialty oil in a narrow market segment. Walnut oil is produced by press extraction of walnut kernels. It is rich in unsaturated fatty acids, which comprise >90% of the oil (Fig. 4.148). Its physical data and the world market price of 1990 are given in the fact file (Table 4.70). 4.3.19 Rice Bran Oil
In many countries that grow rice, rice bran oil is produced as a by-product. It is the only cereal oil that is produced in large quantity. Still the amount is not very high, because only a small fraction of the potential is used today. The rice grain accounts for two thirds of the unskinned rice. During milling, the bran is obtained (skin and germ, 5-5.5% of the whole grain);the bran has an oil content of 12-18% (Fig. 4.149). This means that the potential of rice bran oil is -0.8% of the total rice produced. Only 8% of this potential is exploited today, representing -340,OOO MT/y (Table 4.71).
306
Fats and Oils Handbook
Fig. 4.144. Niger flower, niger seed, and composition of niger seed (photo: Schuster 1992; courtesy of DLC Verlag, Frankfurt.)
Fig. 4.145. Fatty acid composition of niger seed oil.
Vegetable Fats and Oils
307
TABLE 4.68 Fact File of Niger Seed Oil German: Nigersaatol
French: huile de niger
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 200C; ref. water 20°C) (nD40) (mg KOHIg oil) (Wijs method) (gkg oil)
Melting point
-"C
Solids content at
KF"-') (O/O)
Spanish: aceite de niger 0.91 0-0.91 5 1.466-1.469 188-1 94 128-1 36
4 5
Solidification point
-8 to -20°C
0132
10150
20168
30186
35195
0
0
0
0
0
World market price per MT ex factory India (mid-1995)
-1050 U.S. $
The main fatty acid is oleic acid. In addition to its relatively high proportion of linoleic acid, the amount of palmitic acid is remarkable (Fig. 4.150). Dasgupta (1981) analyzed the triglyceride composition and found 30% GU,, -50% GSU, and 20% GS,U (Fig. 4.151).
Fig. 4.146a. lllip6 plant, nuts, and composition of illip6 nuts (photo: courtesy of Karlshamns, Karlshamn).
308
Fats and Oils Handbook
Fig. 4.146b. Main fatty acid composition of borneo tallow.
Fig. 4.147. Triglyceride composition of borneo tallow (after Meara and Zuky 1940) and shea butter (after Sawadogo and Bezard 1982).
Vegetable Fats and Oils
309
TABLE 4.69 Fact File of Borneo Tallow (Illip4 Butter) German: Borneotalg, Illip6butter
French: suif de BornQ
Relative density Refractive index Iodine value Unsaponifiable matter
(at 4 K ; ref. water 20°C)
Spanish: aceite de borneo 0.901-0.902 1.459-1.462 50-64 14-23
(Wijs method) (gkg oil)
Melting point
25-29°C
Solidification point
Solids content at
(VF)
0/32
10150
20168
30186
35/95
(YO)
80
75
58
0
0
World market price per MT (mid-1995)
17-22°C
2300 US. $
The production and refining process is very different, depending on the FFA content of the matrix. Due to the production process of the main product, rice, crude bran that has ~ 1 0 % FFA can rarely be found. If the bran, after separation from the rice grains, is heated for -3 h and held at a temperature between 85 and 100°C, oil with ~ 1 0 % FFA can be obtained (Fig. 4.152). The physical data are given in the fact file (Table 4.72). 4.3.20 Other Edible Oils
The vegetable fats and oils listed in Table 4.73 with their composition and physical data have regional importance only or are produced only in low tonnages.
Fig. 4.148. Main fatty acid composition of walnut oil.
Fats and Oils Handbook
310
TABLE 4.70 Fact File of Walnut Oil German: Walnussol
French: huile de noix
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 20°C; ref. water 20°C) (nD40) (mg KOHIg oil) (Wijs method) (gkg oil)
Melting point
-‘C
Solids content at
(“(3°F)
Spanish: aceite de nuez
0.909-0.91 1 1.469-1.475 186-1 97 143-1 67 4-5
Solidification point
(Oh)
-1 2 to -29°C
0132
10150
20168
30186
35/95
0
0
0
0
0
World market price per M T (mid-1995) World production
-3000 U.S. $ -950,000 MT of nuts
Fig. 4.1 49. Composition of rice. TABLE 4.71 Rice Production in the World and Potential for Rice Bran Oil Year 1994 (MMT)
Rice
Total world China India Indonesia Bangladesh Thailand Vietnam Burma Japan Brazil
535 178 118 46 28 19 23 19 15 11 9 4.6 1.3
us.
Egypt Italy
Rice bran
26.8 8.9 5.9 2.3 1.4 0.95 1.15 0.95 0.75 0.55 0.45 0.23 0.07
Potential amount of rice bran oil
4.0 1.3 0.9 0.35 0.21 0.14 0.1 7 0.14 0.1 1 0.08 0.07 0.035 0.01 1
Vegetable Fats and Oils
31 1
Fig. 4.150. Main fatty acid composition rice bran oil
4.4 Nonedible Oils and Fats Besides edible oils and fats, those for chemical and technical purposes are also grown, however, on a comparably small scale. Some of these will be mentioned briefly in the following section. 4.4.1. Castor Oil
Castor (Ricinus communis L.), belonging to the family of Euphorbia plants, is a perennial plant of 1-2 m, and, in special cases, 3-5 m in height. It is grown in trop-
Fig. 4.151. Triglyceride composition of rice bran oil (after Choi and Park 1983).
Fats and Oils Handbook
312
Rice i
I
Oil content 4.8%
Dehulling
I -___ -*
I
>>> Dehuihd rim
-.
Riw'bran (hulls and gem. oil content 12-18%)
85-1WC, 3 h, insctlvaticn ofenzymes (preferably al the mill) Pelbting
Cooking
Steam
Improve prccintiin during extraction
+
Flaker rolls
(Immersionextmdion)
t
c
I
Extraction solvent fE) >>*
I1
1 -
'I
/I t
I
I
I
Extraction (5.2.3) I
Residue (R)
Mismlla
Evaporation of
Evaporation of
I--
I
Extractibn meal
Crude rice bran oil
Fig. 4.152. Flow chart of rice bran oil production.
TABLE 4.72 Fact File of Rice Bran Oil ~
~
~
Spanish: aceite de arroz
German: Reisol
French: huile de riz
Relative density Refractive index Saponification value Iodine value Unsaponifiable matter
(at 25OC; ref. water 25°C)
0.91 6-0.921 1.465-1.470 181-1 94 98-1 10 3-5
(flD40)
(mg KOH/g oil) (Wijs method) (dkg oil)
Melting point
-5 to -1 0°C
Solidification point
Solids content at
("(2°F)
0132
10150
20168
30186
35/95
(Oh)
<0.5
0
0
0
0
World market price per MET ex factory India (mid-1995)
950-970
U.S.$
--"C
31 3
Vegetable Fats and Oils
TABLE 4.73 Fact File of Different Minor Edible Oils and Fats Shea butter
Fulwah tallow
Mowrah butter
Oat oil
Fatty acid cl 6:O C18:O
c18:l
C18:2 cl 8:3
C20:O Melting point ("C) Solidification point ("C) Relative density (at 40°C) Refractive index (1-1~40) Iodine value Unsaponifiable matter ( O h )
6 41 49 4 32-42 17-27 0.9014.902 1,465-1.466 55-65 2-1 1
56.5 3.5 36 4 -27 38-43 0.909-0.91 0 1.455-1.458 40-50 2-3
23.5 19 43 14 25-42 18-25 0.904-0.909 1.458-1.461 55-65 <2
10.5 58.5 31 -15 to-21 -0.909 1.464-1.468 100-115 1 .C-2.5
Pumpkin seed oil
Wheat germ oil
Hazelnut oil
Almond oil
13
<0.3 3-1 0 1-1.5 85-88 3-9
<1.5 3.0-4.5 2-4 77 17-20 -1 0 to -21 0.902-0.904 1.1 62-1.465 93-1 05 0.5-1 .O
-
Fatty acid c1 4:O c1 6:O
cl 8 : O
C18:l C18:2 c18:3
C20:O
Melting point ("C) Solidification point ("C) Relative density (at 40°C) Refractive index (nD40) Iodine value Unsaponifiable matter ( O h )
16 5 24 54 0.5 -
<0.5 -
-1 5 to -1 6 0.9034.909 1.466-1.469 1 1 5-1 30 0.5-1.5
-14 to-19 0.915-0.91 7 1.468-1.478 115-125 3.5-6
1 30 44 11
-
-1 8 to -20 0.988-0.904 1.462-1.463 84-90 0.3-0.5
Continued
ical and subtropical regions and produces seeds over a period of 10-15 years. In the mid 1980s, the hectare yield was an average of 650 t, with the highest being in the Philippines (3 636 tonha) and the lowest in Burundi (160 tonha; Table 4.74). The castor bean consists of a capsule containing dark brown seeds that are 9-20 mm long, 6-15 mm wide and 4.5-9 mm thick. The seeds have a kernel that accounts for -25% of the seed weight. The thousand-seed weight is -650 g, the bulk weight -400 g/L. The seeds contain lipolytic enzymes that act so vigorously that slight damage to the seed leads to enormous fat splitting (Fig. 4.153). Varieties that do not burst are harvested from the bush after drying; others must be gathered before drying. After suitable pretreatment, castor oil can be used to produce drying oils, paints and source material for man-made fibers. Cautious hydrogenation yields a waxy hard fat (melting point 8686°C). Ricinolic acid ( S O % ) dominates the fatty acid spectrum (Fig. 4.154). The expeller extraction cake is not directly suitable for
Fats and Oils Handbook
314
TABLE 4.73 (Continued) coffee oil
Tea seed oil
POPPY seed oil
Pecan nut oil
3 28 12.5 17.5 36 3 8-9 0.950-0.952 1.462-1.472 75-1 10 2-28
<5 4.5 <87 7 -
-
-
<5 3 30 62
-
-
4 3 75 15
-5 to -1 5 0.899-0.904 1.466-1.470 85-90 <1.5
-1 5 to -20 0.908-0.91 1 1.467-1.470 189-94 0.4-1.2
0.904-0.906 1.461-1.466 97-1 07 0.3-0.7
White mustard seed oil
Black mustard seed oil
Hemp seed oil
Peach kernel oil
<0.5 1.5 <0.5 22 14 <7 7 2 44 0.903-1 .OOO 1.463-1.466 94-1 04 0.7-1.5
Fatty acid c14:0 c1 6:O
Cl8:O C18:l C18:2 c20:o c16.0
Melting point ("C) Solidification point ("C) Relative density (at 40°C) Refractive index (nD40) Iodine value Unsaponifiable matter (%)
Fatty acid cl4:O
C160 c16:0
C18:l C18:2 c1 8:3
C20:O C20:l c22:o
C22:l Melting point ("C) Solidification point ("C) Relative density (at 40°C) Refractive index (nD40) Iodine value Unsaponifiable matter ( O h )
<2 <0.5
4.5-1 0
-
6-20 14-28 14-28
-
<0.5 <2.5 40.5 0.9034.91 1 1.464-1.467 101-112 0.7-1.5
-
-
2-8
-
60-80 17-31
-
-
-
-15 to-27 0.913-0.91 5 1.466-1.470 149-1 67 0.5-1 .O
0.901-0.905 1.462-1.466 95-1 11 ,0.5-1 .O
TABLE 4.74 Castor Bean Production i n the World and Some Selected Countries Castorbeans(MMT)
1935
1950
1960
1970
1980
1990
1993
1994
1995
Total world Brazil India China PR
0.18 -
0.22
0.26 0.27 0.11 0.05
0.72 0.23 0.11 0.09
0.84 0.30 0.22 0.12
0.86 0.30 0.25 0.12
1.16 0.04 0.70 0.28
1.34 0.05 0.88 0.26
1.33 0.03 0.90 0.28
-
-
Vegetable Fats and Oils
31 5
Fig. 4.153. Castor plant, castor seed and composition of castor seed (photo: Schuster 1992; courtesy of DLG Verlag, Frankfurt).
animal feed because it contains 0.8-1.0% poisonous ricin. Steam treatment during removal of solvents reduces the amount to e l 0 ppm. This no longer leads to intoxication of the animals, but the meal is not well accepted as fodder. Even with evidence from as early as 1885 that purified meal is no risk, castor meal is still not allowed as fodder in Germany. Data for castor oil is shown in Table 4.75. 4.4.2 Tung Oil
Tung oil is the oil from the seeds of a tree that originates in China (Aleurifisfordii and Aleurifis monfuna).The fruit of this tree that is 12 m (A.fordii) or 20 m (A. montuna) in height contain 3-5 seeds. The seeds have a hard shell and contain -50% fat in their kernels. The tree can stand winter temperatures down to -15°C; the yield, however, suffers at or below -6°C. A. monfuna can be cultivated to altitudes of 1800 m, but to produce fruit, it requires 470 h above 7°C at least. The nuts are manually or mechanically harvested. Best yields reported are -3000 kgha. The shells of the seeds are used to loosen up the soil. The expeller cake contains 25% protein; it cannot be used for feeding because it also contains poisonous by-products and is therefore returned to the soil as fertilizer.
Fats and Oils Handbook
316
10
Proportion [%]
Fatty acid
RiCil0l;eiC acid
Fig. 4.154. Main fatty acid composition of castor oil.
The world harvest of tung oil is -400,000 tody, with up to two thirds coming from China and one third from South America. Tung oil is used mainly in the paint industry and for polishing liquids. In humans, it causes nausea and, if heavily in contact with the skin, leads to inflammation that heals only very slowly. Its main triglyceride is trielaeosterin. The equivalent fatty acid accounts for up to 80% of all fatty acids of tung oil (Fig. 4.155). Its processing is shown in Figure 4.156. Table 4.75 shows the main data for tung oil. TABLE 4.75 Data of Castor Oil and Tung Oil Castor beans (MMT) German French Spanish Solifidification point Relative density Refractive index Iodine value Unsaponifiable matter World market price mid-1 993 mid-1 995 World production 1980 1994 1995
Castor oil
Tuna oil
Rizinusol huile de rizen aceite de ricino -12 to-18 1.466-1.473 0.942-0.952 82-90 2-3
Tungol; chinesisches Holzol huile d'abrasin aceite de tung -17 to-21 1.51cL1.514 0.922-0.927 160-1 75 4-1 0
-1 000 -900
-2800 -1400
-0.30 -0.40
-0.08 -0.09
Vegetable Fats and Oils
31 7
Fig. 4.155. Main fatty acid composition of tung oil.
4.4.3 lojoba
Jojoba (Simmondsia chimensis) grows wild in the southwestern United States and northwestern Mexico. The name comes from the Indian word "jojowi" (Anonymous 1980). The plant is an evergreen bush that reaches a height of 50-600 cm with tap roots that can reach 10 m into the ground. The bushes can become as old as 200 y and can survive only 120-200 mm of rain annually. After 25 y, they yield up to 13.5 kg of nuts per bush. They deliver a waxy fat of interesting properties. The fruit are long, oval, green capsules that hold 1-3 seeds 12-18 cm in length and 6-12 cm in width (X). The thousand-seed weight is 400-1000 g. After harvest, they must be dried to a maximum humidity of 9-10% if storage is intended. At present, the world harvest is 40,000 tody. Jojoba fruit contain -80% wax (Yermanos 1975; Fig. 4.157). The wax is a paramount source for the fatty acids shown in Figure 4.158. It does not contain triglycerides and therefore is not a fat, although always regarded as one. It contains only waxes of alcohols with longchain rare fatty acids. Jojoba oil is very similar to sperm oil and can be used to replace it. This is very important because whale hunting has been given up by almost all countries. In some respects, jojoba oil is even better than sperm oil, having the great advantage that it needs no special purification. Table 4.76 compares the properties of jojoba oil with sperm whale oil.
4.5 Other Oil Sources The first m a l s to use microorganisms for fat production were made in Germany during World War 11(Woodbine 1959). It was recognized that microorganisms reproduce rapidly. Those living on fat use it as their main source for carbon. Under special cir-
Fats and Oils Handbook
318
i - P I
Exbudon(S.2.3)
I
Fig. 4.156. Flow chart of tung oil production.
Fig. 4.157. Jojoba plant, jojoba seed and composition of jojoba seed (photo: Schuster 1992; courtesy of DLG Verlag, Frankfurt).
Vegetable Fats and Oils
31 9
Fig. 4.158. M a i n fatty acid composition of jojoba oil.
cumstances, however, other microorganisms that use different material for their nutrition synthesize fats and oils. This offers the opportunity to allow microorganisms to accomplish the following: to produce fat that they synthesize from nonfat feed, to process low-grade fats or waste fats that are not suitable for human consumption into edible grade fats, and to modify fats by feeding them fat with unwanted fatty acid composition, for example, to yield the desired composition. Glatz et al. (1984) studied many microorganisms and found that Candida lypolytica is able to incorporate and accumulate fat if fed fat. As shown later, fat production starts only when other nutrients, mainly nitrogen compounds, are scarce and growth is hindered. The cells “fatten.” The fat in the media is split using the microorganism’s own lipases, absorbed into the cell and resynthesized into triglycerides. Figure 4.159 shows the results of feeding four different fats. TABLE 4.76 Comparison of Jojoba Oil with Sperm Oila
German French Spanish Sulfur content (O/O Wuwt) Melting point (“C) Neutralization number Saponification number Flame point (“C) 5ource: Miwa (1 979).
Jojobaoil
Sperm oil
Jojobaol huile de jojoba aceite de jojoba 11.0 9-1 5 3.5-7.0 81-118 223-248
Spermol huile de spermaceti aceite de espermaceti 11.0 15 3.0 167 240
320
Fats and Oils Handbook
In addition to the possibility of producing fat that is not suitable for human nutrition, there are also microorganisms that build fat from other substrates. Bacterial fats or fats obtained from molds or yeasts could play a substantial role in the fat production of the future. Up to now, molds and yeasts showed the highest potential for fat production. But there are also some bacteria and algae that can be considered. However, Ratledge et al. (1984) assumed that conversion factors of 25% will rarely be exceeded and calculated (1982) that feeding 100 g glucose yields -25 g fat. Therefore, for large-scale manufacture, it is important to find a cheap substrate to feed the microorganisms. Bird and Molton (1972) showed the possibility of using hydrocarbons as a nutrient. The biomass left after oil extraction might be used as animal feed. There are not sufficient trials yet to confirm that. Not all microorganisms that produce sufficient fat could be used for production because many build poisonous by-products. In the following, a short overview is given on the state of the art reached in the late 1980s. Microorganisms are regarded as fat-building if they contain ATP. Thls enables them to quickly produce acetyl coenzyme A and thus produce fat with acceptable speed. The following examples do not claim to be complete; they are meant only to illustrate the potential. Because there are not yet any microorganisms used for fat production, it cannot be predicted which species will be best suited for large-scale industrial exploitation. Therefore the microorganisms have been chosen only as examples. With the great progress that is being made in biotechnology, it is only a question of time until this potential will be fulfilled. This is especially true for the fatty acid composition. Because bacteria have a short life cycle, multiplication is
Fig. 4.159. Comparison of main fatty acid composition of oils fed to and yielding from Candida lipolytica (after Clatz e t a / . 1984).
32 1
Vegetable Fats and Oils
much faster than with other living organisms. Desired triglyceride types can therefore be bred much more quickly than in plants. Ratledge and Wilkinson (1988) give a very detailed overview on the subject. 4.5.1 Fats from Yeasts and Molds
Yeasts and molds in general can contain up to 70% lipids (Table 4.77). A detailed overview is given by Ratledge (1982). The oils of yeasts are composed of 80% triglycerides, up to 5% diglycerides, low amounts of monoglycerides, and up to 10% FFA. The triglyceride content of molds varies much more than that of yeasts. There are examples for lipid contents of 16% of which 40% are FFA but also extremes of 92% lipids with practically no FFA. The fatty acid composition resembles that of vegetable oils, with emphasis on oleic and palmitic acid. Fat-producing molds and yeasts are grown in that they are deprived of nutrients necessary for multiplication, but at the same time, given an excess of carbohydrates. The cells “fatten” by converting carbohydrates into fat via their metabolism (Fig. 4.160). The figure shows the development of fat after essential ammonium compounds have been kept back. The carbodnitrogen ratio then lies between 50:1 and 60:l. Figures 4.161 and 4.162 prove that the most prominent fatty acid is oleic acid, with palmitic acid ranked second.
4.5.2 Bacteria Fats Bacteria produce much lower amounts of fats than yeasts and molds. The fats contain mainly palmitic acid, and also single unsaturated fatty acids, but no polyunsaturates. They contain up to 20% FFA. Wayman et al. (1984) describe Arthrobacter A K 19, a soil bacterium that lives off short-chain hydrocarbons. Brought onto a mineral support and fed with glucose solution, this bacterium converts 78.3% of its cell dry matter into fat within 13 d (Fig. 4.163). An investment of 7 g of glucose is required to yield 1 g of fat. The fatty acid composition has been analyzed by Kormendy and Wayman TABLE 4.77 Oil Content of Different Species of Yeasts and Moldsa ~~
Species (yeasts)
Candida lipolytica Trichosporum cutaneum Candida curvata Lipomyces lipoferus Endomyces vernalis Rhodotorula glutinis aSource: Ratledge (1 984)
Fat content (YO)
36 45 5a 63 65 71
Species (molds)
E utomophthora virulenta Aspergillus flaws Phytium ultimum Fusariurn bulbigenum Aspergillus fischeri Penicillium lilacinum Mucor circinecelloides
Fat content (%)
26 2a 49 50 53 56 65
fats and Oils Handbook
322
Ammonia content [gj]
Fat content [% w/w] Blo mass [g/I]
1.6 I 1.4 1.2
30
1
0.8
20
0.6
0.4
10
0.2
0
0 0
8
16 24 32 40 48 56 64 72 80 88 96
Time [h]
Fig. 4.160. Fat production in molds after stopping NH, supply (after Boulton 1982).
Fig. 4.161. Main fatty acid composition of fat produced by yeasts (after Ratledge et a/. 1984).
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Fig. 4.162. Fatty acid composition of fat produced by molds (after Ratledge et a/. 1984).
(1974; Fig. 4.164). In contrast to vegetable and animal fat, >17% of the fatty acid chains in the triglycerides of this bacterium have an uneven number of carbon atoms. Growth and fatty acid composition are influenced by many factors. In many trials, it has been shown that the maximum fat content could be reached by feeding 0.2 m o m glucose, pH 7-8, and 8 mmol phosphate concentration (Fig. 4.165). 4.5.3 Fats from Algae
Algae are a great potential source for all kinds of food source materials because of their ability to photosynthesize (Fig. 4.165). They are used for human nutrition but also for fish and animal feed. In Africa, China, Japan, and Oceania, >1 million tons of algae are harvested each year (Michanek 1978). Algae fats, like those from bacteria, contain a large number of fatty acids with an uneven number of chain carbon atoms. However, the majority of fatty acids here too are those well known from conventional fat sources. Algae fats of the family of Chlorophyceae are dominated by palmitic and oleic acid, with some remarkable amounts of linoleic acid (Table 4.78).
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Fat content
20
[%I
Cell-/Fat weight [g/l]
e Fat content
[%I
* Cell weight [g/l]
Fat weight [g/l]
0 1
3
5
7
9
11
13 15 17 19 21
23
Growth [d] Fig. 4.163. Fat content of Arthrobacter AK79 grown on 0.2m glucose solution at 25°C (after Wayman eta/. 1984).
Algae of the family Bacilluriophyceae contain substantial amounts of palmitoleic acid, but only a small proportion of oleic, linoleic and linolenic acid (Fig. 4.167). Algae from the Cyanophyceae family contain large amounts of CI6and CISfatty acids with more than two double bonds. The total of these fatty acids can reach >80% (Fig. 4.168).
Fig. 4.164. Main fatty acid composition of oil from Arthrobacter AK79 grown on 0.2m glucose solution (after Kormendy eta/. 1974).
Vegetable Fats and Oils
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Fig. 4.1 65. Dependency of the fatty acid composition of Arthrobacter AK 19 on ternperature and nutrient (after Wayrnan e t a / . 1984). One assumes that the fat content of algae for fat production can be increased to -50%. Here also the fat content rises if other nutrients fall short. The cost for algae fats is forecast conservatively by Shifrin (1980) to lie between 70 and 700 U.S.$ per ton, depending on the feed-stuff. They could therefore become a serious competitor for vegetable oil.
Fig. 4.166. Yield of conventional oil fruit and potential oil sources (after Princen 1979 and Calvin 1979).
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TABLE 4.78 Oil Content of Different Species of Algae
Fat content Species
(YOof dry matter)
~~
Chlorella ellipsoida Chlorella pyrenoidosa Chlorella sorohiniana Ochrornionas danica Thalassiosira fluviatilis
3 w 5 1C-85 15-39 53 50
Swrce: Princen (1979).
Fig. 4.167. Fatty acid composition of fat produced by algae (Chlorophyceae, after Shifrin 1984).
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Fig. 4.1 68. Fatty acid composition of fat produced by algae (Bacilloariophyceae,after Shifrin 1984).
4.6 References
4.6.'0 General Literature on Oil Plants Applewhite, T.H., (ed.)(1987) Proceedings of the World Conference of Biotechmlogy for Fats and Oil Industry, Hamburg. Backlog, B.P., (1990) Storage Handling and Shipping Practices Buyerrnecipient Viewpoint, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R, ed.), pp. 28-30, American Oil Chemists' Society, Champaign, IL. Bailey, A.E., (1951) Industrial Oil and Fat Products, Interscience Publishers, New York. Bally, W., (ed.) (1962) Tropische und Subtropische Weltwirtschuftpjlanzen, Olpfanzen, Ferdinand Enke Verlag, Stuttgart. Becker, M., and Nehring, K., (1%5) Handbuch der Futtermittel, Paul Pimy Verlag, Hamburg. Bemardini, E., (1985) Oilseeds, Oils and Furs, Publishing House B.E.Oil, Rome.
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Duvel, D., in Pflanzliche Rohstofle der Margarine, Information des Margarine-Institut fur gesunde E m h n g . Eckey, E.W., (1954) Vegetable Fats and Oils, Reinhold, New York. FOA Production Yearbook, Food and Agricultural Organization of the United Nations, Rome. Franke, G., (1975) Nutzpf2anzen der tropen und Subtropen, S . Hirzel Verlag, Leipzig. Gander, F.K., (1969) Technologie der Speisefette und Fettprodukte, in Handbuch der Lebensrnittelchemie IV,Springer Verlag, Berlin. Gander, F.K., (1 969) Wirtschaftliche Bedeutung der Speisefette, in Handbuch der Lebensrnittelchemie IV,Springer Verlag, Berlin. Godin, V.J., and Spensley, P.C., (1971) TPI Crop and Product Digest No.1 Oils and Oil Seeds, The Tropical Products Institue, Foreign Commonwealth Office, London. Irvine, F.R., (1969) West Afncan Crops, Oxford University Press, London. Kirschenbauer, H.G., (1960) Fats and Oils, Reinhold Publishing, London. Lennerts, L., (1984) Olschrote, Olkuchen, pjlanzliche Fette und Ole, Verlag Alfred Strothe, Hannover. Matheson, E.M., (1976) Vegetable Oil Seed Crops in Australia, Holt Reinhart and Winston, Sydney. Menninger, E.A., (1977) Edible Nuts ofthe World, Horticultural Books, Inc., Stuart, FL. Pardun, H., (1969) Analyse der Fette und Fettbegleitstoffe, in Handbuch der Lebensrnittelchemie IV,Springer Verlag, Berlin. Purseglove, J.W., (1969) Tropical Crops, Longmans, Bristol. I. Dicotyledons I LII. Monocotyledons I 11. Dicotyledons 11 IV.Monocotyledons 11 Rehm, S., and Espig, G., (1976) Die Kulturpjlanzen der Tropen und Subtropen, Verlag Eugen Ulmer, Stuttgart. Robbelen, G., Downey, R.K., and Ashri A., (eds.) (1989) Oil Crops of the World, McGraw Hill, New York. Salunkhe, D.K., and Desai, B.B., (1986) Postharvest Biotechnology of Oilseeds, CRC Press, Boca Raton, FL. Schiittauf, W., and Pischel, U., (1978) Die Margarine in Deutschland in der Welt, Presseabteilung der Union Deutsche Lebensmittelwerke, Hamburg. Swem, E., (ed.) (1951) in Bailey’s Industrial Oil and Fat Products, Interscience Publishers, New York. TPI (1971) Tropical Product Institute, (see Godin and Spensley). Vaughn, J.G., (1970) The Structure and Utilization of Oil Seeds, Chapman & Hall, London. Weiss, E.A., (1983) Oilseed Crops, Longman Verlag, London. Wissebach, H., (1969) Pflanzen und Tierfette (ausgenommen Milchfette). Vorkommen, Gewinnung, Zusammensetzung, Eigenschaften Verwendung, in Handbuch der Lebensmittelchemie IV,Springer Verlag, Berlin. Wolff , LA., (1982) CRC Handbook of Processing and Utilization in Agriculture, Vol. III, CRC Press, Boca Raton, FL.
4.6.1. Cultivation, Harvesting, Transport, and Storage Anonymous (1984) Bundesanzeiger, Der Bundesminister der Justiz, Bekanntmachung von weiteren Leitsatzen des deutschen Lebensmittelbuches, 26. Mai. 1984.
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329
Anonymous (1962) The Wealth of India, Raw Materials, Vol. 6, New Dehli Council Sci. Ind. Res. Anonymous (1980) Oilseeds, Oils and Fats, International Association of Seed Crushers, London. Appelqvist, L.A., and Johansson, S.A., (1963) Riskerna vid alltfor kraftig nedtorkning av oljevbtfro, Svensk Frb'tidning 32,97-101. Barkla, F., and Pritchard, K., (1980) Proc. 4th Aust. Sun$ Con$ Shepparton Vic.5 , 18-22. Beumer, B., and Wehmeier, K.H., Fordem und Heben 10, 1960; 11, 1961 (separate printing, Hannover-Messe 1964). Booth, G.R., (1984) Post Harvest Handling and Storage m; Pulses, Oilseeds and Nuts, Agribuy. Worldwide 5,20. Chavan, K.P.S., Purkar, J.K., and Banerjee, S.K., (1984) Ageing Induced Changes in Seeds, Seed Res. 12,53-71. Christensen, C.M., Sunflower Seed Storage: A Progress Report, Protokoll der 3rd Int. Sunflower Con$, pp. 84-96, Crookston, MN, August 1968. Chu, Y.H., and Lin, J.Y., (1993) Factors Affecting the Content of Tocopherol in Soyabean Oil, J. Am. Oil Chem. SOC.70,126-1268. Clanindin, D.R., Robblee, A.R., Slinger, S.J., and Bell, J.M., (1978) Composition of Canadian Rapeseed Meal, in Canadian Rapeseed Meal: Poultry and Animal Feeding, pp. 8-15, publication 5 1 of Rapeseed Association of Canada, Winnipeg. Cramer, H.H., (1 967) Plant Protection and World Crop Production, PflanzenschutzNachrichten der BAYER AG, Leverkusen. CSIRO, Technology Statement: A Summary of the Status of Research, Development and Commercialisationof Linola, June 1990. Fager, G.M., Kinney, A.J., and Hitz, W.D., (1995) Using Biotechnology to Reduce Unwanted Traits, INFORM2, 168-169. Fedeli, E., Cortesi, N., Camurati, F., and Jacini, G., (1972) Regional Differences of Lipid Composition in Morphologically Distinct Fatty Tissues IV; Safflower and Sunflower Seeds, J. Am. Oil Chem. SOC.49,233-238. Fleming, R., (1990) Trading Rules and Regulations, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 15-23, American Oil Chemists' Society, Champaign, IL. Geigy Documenta, (1968) Diem, K, and Lentner, C., (eds.),Wissenschaftliche Tabellen, Basel. George, S., and Arumughan, C., (1993) Positional Distribution of Fatty Acids in Triglycerols of Developing Oil Palm Fruit, J. Am. Oil Chem. SOC.70, 1255-1258. Gustafson, E.H., (1976) Loading, Unloading, Storage, Drying, and Cleaning of Vegetable Oil Bearing Materials, J. Am. Oil Chem. SOC.53,248-250. Harris, H.C., McWilliams, J.R., and Mason, W.K., (1978) Influence of Temperature on Oil Content and Composition of Sunflower Seed, Aust. J. Agric. Res. 29, 1203-1212. Haumann, B.F., (1990) Low Linolenic Flax: Variation on Familiar Oilseed, INFORM 1, 934-94 1. Haumann, B.F., (1992) Monounsaturates Grow, INFORM 3,666477. Henry, J.L., and MacDonald, K.B., (1978) Effects of Soil Fertilizer Nitrogen and Moisture on Yield, Oil and Protein Content of Rape Seed, Can. J. Soil Sci. 58, 303-310. Holt, N.W., and Campbell, S.J., (1984) Effect of Plant Density on the Agronomic Performance of Sunflower on Dryland, Can. J. Plant Sci. 64,599405,
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Kling-Wohlbier, (1983) Handelsfittem’ttel, Verlag Eugen Ulmer, Stuttgart. Kliipfel, O., and Beumer, B., (1977) Lose-Verladesysteme fur Schuttguter in LKW, Eisebahnwagen und Schiffe, Zement-Kalk-Gips 30,299-306. Kliipfel, O., and Beumer, B., (1979) GegenwPrtiger Stand in der HochleistungsGurtbechenverkstechnik, Zement-Kalk-Gips 32,149-1 55. Lamour, R.K., Sallans, H.R., and Craig, B.M., (1944) Hygroscopic Equilibrium of Sunflower Seed, Flax Seed and Soya Bean, Can. J. Res. 22F, 1-8. Ludwiczak, J., (1990) Marine Transportation of Edible Oils and Fats, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.),pp. 25-27, American Oil Chemists’ Society, Champaign, IL. Luhs, W., and Friedt, W., (1994)The Major Oil Crops, 13, in Designer Oil Crops, Verlag Chemie, Weinheim. Mahatta, T.L., Technology and Refining of Oils and Fats, Small Business Publications, Dehli. Mazzani, B., and Allievi, J., (1966) Effects of Different Harvest Dates on Yield and Some Seed Characteristics in Two Sesame Varieties, Agron. Trop. 16,223-228. Mukurasi, N.J., (1978) Research on Rapeseed and Fodder Rape at Uyole (Tanzania), Proc. 5th Int. Rapeseed Konfi, pp. 28C-283, Malmo, Sweden. Murphy, D.J., (1993) Structure and Function of Oleosins in Oil Plants, INFORM 4,922-932. Murphy, D.J.(ed.), (1994) Designer Oil Crops, Verlag Chemie, Weinheim. Niyveld and Terpstra, citation from Lennerts, L., Olschrote, Olkuchen, pflanzliche Ole und Fette. O’Keefe, S.F., Wiley, V.A., and Knauft, D.A., (1993) Comparison of Oxidative Stability of High- and Normal-Oleic Peanut Oils, J. Am. Oil Chem. SOC. 70,489492. Orlage, citation from Lennerts, L., blschrote, Olkuchen, pflanzliche Ole und Fette. Padua-Resurrection, A.B., and Banzon, J.A., (1979) Fatty Acid Composition of the Oil from Progressively Maturing Bunches of Coconuts, Philipp. J. Coconut Stud. 4, 1-15. Patterson, H.W.B., (1989) Handling and Storage of Oilseeds, Oils Fats and Meal, Elsevier Applied Science, London. Pioneer International Inc., (1994) Information; Identity Preserved Vegetable Oils... from the Speciality Plant Products Division of Pioneer Hi-Bred International, Inc. PORIM, (1985) Recommended Practices for Storage and Transport of Edible Oils and Fats, Palm Oil Research Institute of Malaysia. Ramstadt, P.E., and Geddes, W.F., (1943) The Respiration and Storage Behavior of Soybeans, Minnesota Agr. Expt. Sta. Techn. Bull. No.156. Robertson, J.A., Russell, R.B., (1972) Sunflower, America’s Neglected Crop, J. Am. Oil Chem. SOC.49,239-244. Robertson, J.A., Russell, R.B., Roberts, R.G., and Chapman, G.W., (1985) Changes in the Oil Type Sunflowerseed Stored at 20%C at Three Moisture Levels, J. Am. Oil Chem SOC.62, 1335-1339. Robbelen, G., (1984) ZFMA Scientific Symposium, Salzburg. Sawan, Z.M., Basyony, A.E., McCuistion, W.L., and El Farra, A.H.A., (1993) Effect of Plant Population Densities and Application of Growth Retardants on Cottonseed and Quality, J. Am. Oil Chem. SOC. 70,313-317. Slabas, A.R., Simon, J.W., and Elborough, K.M., (1995) Transgenic Oilseed Harvest to Begin in May, INFORM2,152-167. Spencer, M.R., (1976) Effect of Shipping on Quality of Seeds, Meals, Fats, and Oils, J. Am. Oil Chem. SOC. 53,238.
Vegetable Fats and Oils
331
SVO Specialty Products, Inc., Technical Bulletins, Complement 70% Oleic Canola Oil, TRISUN Brochure. Ulmig citation from Lennerts, L., Olschrote, Olkuchen,pflanzliche Ole und Fette. United Grain Growers, (1994) Information Wirprdsentieren Linola. Vaughn, J.G., (1970) The Structure and Utilization of Oil Seeds, Chapman & Hall, Ltd., London. Weiss E.A., (1967) Soya Bean Trials on the Uasin Gishu, Western Kenya, East Afr. Agric. For. J. 32 223-228. Wohlbier citation from Lennerts, L., Olschrote, Olkuchen,pjlunzliche Ole und Fette. 4.6.7.1 References for Fafty Acid Compositions Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constitution of Natural Fats, Chapman & Hall,London. II Pardun, H., (1969) Analyse der Fette und Fettbegleitstoffe, in Handbuch der Lebensrnittelchernie N, Springer Verlag, Berlin. III Rudischer, S., (1959) Fachbuch der Margarineindustrie,Fachbuchverlag, Leipzig.
I
IV Wissebach, H., (1969) Pflanzen und Tierfette (ausgenommen Milchfette). Vorkommen, Gewinnung, Zusammensetzung, Eigenschaften Verwendung, in Handbuch der LebensrnittelchemieN , Springer Verlag, Berlin. V Weiss, E.A., (1983) Oilseed Crops, Longman Verlag, London. VI Kling-Wohlbier, (1983) Handelsfuttermittel,Verlag Eugen Ulmer, Stuttgart. W Oetker, (1983) Lexikon Lebensmittel und Ernahrung, Ceres Verlag, Rudolf-August Oetker KG, Bielefeld. VIII Lennerts, L., (1984) Olschrote, Olkuchen, pflanzliche Fette und Ole, Verlag Alfred Strothe, Hannover. IX Williams, K.A., (1950) Oils, Fats and Fatty Foods, J.A. Churchill, Ltd., London. X Congopalm, (1970) Sociek? Cooperative, Avenue des Aviateurs 538, Kinshasa, Congo. XI Sonntag, N.O.V. (1979) Structure and Composition of Fats and Oils, in Bailey’s Industrial Oil and Fat Products, (Swem, ed.),Interscience Publishers, New York. XII Gracian, J., (1968) in Analysis and Characterization of Oils, Fats and Fat Products, (Boekenoogen, H.A., ed.),Interscience Publishers, London. XIII Korp and Landskoug XIV Godin, V.J., and Spensley, P.C., (1971) TPI Crop and Product Digest No.1 Oils and Oil Seeds, The Tropical Products Institue, Foreign Commonwealth Office, London. XV Berger, K., (1986) Palm Oil Products, Food Techno[.,Sept. XVI Bailey, A.E., (1951) Industrial Oil and Fat Products, Interscience Publishers, New York. XVII Meursing, E.H., (1976) Kakaopulver f i r die verarbeitende Industrie, Kakaofabrik de Zaan, Holland. XVIII Werman, M.J., Neeman, I., (1987) J. Am. Oil Chem. SOC.64,229. XIX Bemardini, E., (1985) Oilseeds, Oils and Fats, Publishing House B.E.Oi1, Rome. XX Appelquist, L.-A., and Ohlsson, R., (1972) Rapeseed, Cultivation, Composition, Processing and Utilization,Elsevier Publishing Co., Amsterdam. XXI Nangalingam, T., (1993) Avocados, in Encyclopaedia of Food Science, Food Technology andNutrition, p. 291, Academic Press, London. The above references themselves are sometimes a compilation of literature data that can be looked up in detail under the given reference.
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4.6.2 Pulp Oil Delivering Oil Plants; Pulp Oil 4.6.2.1 Palm Oil Bafor, M.E., and Osagie, A.U., (1986) Changes in Lipid Class and Fatty Acid Composition During Maturation of Mesocarp of Oil Palm Variety Dura, J. Sci. Food Agric. 37, 825-832. Berger, K.G., (1985) Quality Control in Storage and Transport of Edible Oils, J. Am. Oil Chem. SOC.62,438442. Berger, K.G., (1985) The Industrial Uses of Palm and Coconut Oils, OlPagineux40,613-640. Berger, K.G., (1986) Handling and Storage of Palm Oil, J. Am. Oil Chem. SOC.63,80-87. Berger, K.G., (1993) Oil Palms, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 4674, Academic Press, London. Berry, S.K., and Awang, C.R., (1983) Physico-Chemical Characteristics of Palm Olein and Soybean Fat Blends, Vortrag Symposium Palm Oil Product Technology of the 80s, pp. 483498. Bockisch, M., (1993) Vegetable Oils, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 4683, Academic Press, London. Coleman M.H., (1961) Further Studies on the Pancreatic Hydrolysis of Some Natural Fats, J. Am. Oil Chem. SOC.38,685. George, S., and Arumughan, C., (1993) Positional Distribution of Fatty Acids in Triglycerols of Developing Oil Palm Fruit, J. Am. Oil Chem. SOC.70, 1255-1258. Goh, S.H., Choo, Y.M., and Ong, S.H., (1985) Minor Constituents of Palm Oil, J. Am. Oil Chem. SOC.62,237-240. Hartley, C.W.S., (1967) The Oil Palm, Longman, London. Jones, L.H. (1984) Novel Palm Oils from Cloned Palms, J. Am. Oil Chem. SOC.61,1717-1719. Kheiri, M.S.A., (1985) Present and Prospective Development in the Palm Oil Processing Industry, J. Am. Oil. Chem. SOC.62,210-219. Law, K., and Thiagarjan, T., (1990) Palm Oil-Edible Oil of Tomorrow, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R.,ed.), pp. 260-269, American Oil Chemists' Society, Champaign, IL. Maclellan, M., (1983) Palm Oil, J. Am. Oil Chem. SOC.60, 368-373. Okawachi, T., Sagi, N., and Mori, H., (1985) Confectionary Fats from Palm Oil, J. Am. Oil Chem. SOC.62,421425. Ong, A.S.H., (1984) Highlights of Research on Food Uses of Palm Oil, Palm Oil Dev. 1,4-6. Pantzaris, T.P., (1985) Palm Oil, Palm Kernels and Elaeidobius, Palm Oil Res. Inst. of Malaysia, Palm Oil Dev. 3,7-9. Pantzaris, T.P., (1986) Palm Oil, Palm Kernel Oil and Elaeidobius. II. Change in Relation of Palm Oil and Palm Kernel Oil Production, Palm Oil Dev. 4, 1-3. Rossell, J.B., King, B., and Downes, M.J., (1985) Composition of Oil, J. Am. Oil Chern. SOC. 62,221-229. Southworth, A,, (1985) Palm Oil and Palm Kernels, J. Am. Oil Chern. SOC.62,250-253. Tan, B.K., Ong, S.H., Rajanaidu, N., and Rao, V., (1985) Biological Modifications of Oil Composition, J.Am. Oil Chem. SOC.62, 230-236. Timms, R.E., (1985) Physical Properties of Oils and Mixtures of Oils, J. Am. Oil Chem. SOC. 62,241-249. Traitler, H., and Dieffenbacher, A,, (1985) Palm Oil and Palm Kernel Oil in Food Products, J. Am. Oil Chem. SOC.62,417421,
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Unilever, (1985) Technology Applied to Third World Needs, Unilever Plantations Group, London. 4.6.2.2 Olive Oil Bockisch, M., (1993) Vegetable Oils, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 4684, Academic Press, London. Chahbar, A., and Zguigal, Y., Mechanical Harvesting of Olives in Morocco, Olivae 4, 29, Dec. 1987. Descargues, G., and Bezard, J., (1981) Triacylglycerol Structure of a Consumer-Available Virgin Olive Oil, Riv. Ital. Sost. Grasse 58, 613-619. Fedeli, E., (1983) Miscellaneous Exotic Oils, J. Am. Oil Chem. SOC.60,404406. Gracian, J., Arevalo, G., and Martel, J., (1963) Caracteristicas del Aceite de Oliva de Produccion Nacional, Datos Correspondientes a las Provincias Andaluzas IV,El Indice de Escualeno y Su Aplicacion con Fines Analiticos, Grasas y Aceites 14, 101. Gracian, J., Arevalo, G., and Martel, J., (1964) The Chemistry and Analysis of Olive Oil, in Analysis and Characterizationof Oils, Fats and Fat Products 11, (Boekenogen, H.A., ed.), pp. 3 15-606, Interscience Publishers London, New York. Mendoza, J., Gomez, M., and Casado, F., (1990) Technological Evolution of the Different Process for Olive Oil Extraction, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson D.R., ed.),pp. 341-347, American Oil Chemists’ Society, Champaign, IL. Minguez-Mosquera, M.I., Rejano-Navmo, L., Gandul-Rojas, B., Sanchez-Gomez, A.H., and Garrido-Fernandez, J., (1991) Color-Pigment Correlation in Virgin Olive Oil, J. Am. Oil Chem. SOC.68,332-336. Ministerio de Agricultura, (1983) Las Raices del Aceite de Oliva, Lisbon. Raina, B.L., (1993) Olives, in Encyclopaedia of Food Science, Food Technology and Nutrition, pp. 3353-3358, Academic Press, London. 4.6.2.3 Avocado Oil Ahmed, E.M., and Barmore, C.R., (1980) Avocado, in Tropical and Subtropical Fruit, (Nagy, S . and Shaw, P.E., eds.), AVI Publishing, Westport, CT. Biale, J.B., and Young, R.E., (1971) The Avocado Pear, in Biochemistry of Fruits and Their Products, Chapter 1, V01.2, (Hulme, A.C., ed.), Academic Press, London. Caldwell, B.E., (ed.), (1973) Soybeans, Improvement, Production, and Uses, American Society of Agronomy, Inc., Publishers, Madison, WI. Hill, L.D., (ed.) (1976) World Soybean Research, The Interstate Printers & Publishers, Inc., Danville, IL. Lanzani, A., Bondioli, P., Mariani, C., Fedeli, E., Ponzetti, A., and Pieralisi, G., (1986) A Method for Wet Production of Oil and Protein from Avocado, Riv. Ital. Sost. Grasse 63, 487-492. Mazliak, P., (1975) Les Lipides de l’Avocat, Fruits 20,49-57. Nangalingam, T., (1993) Avocados, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 291, Academic Press, London. Tingwa, P.O., and Young, R.E., (1975) Studies on the Inhibition of Ripening in Attached Avocado (Persea americana mill.) Fruits, J. Am. SOC.Hom’c. Sci. 100,447. Werman, M.J., and Neeman, I., (1987) Avocado Oil Production and Chemical Characteristics, J. Am. Oil Chem. SOC.64,229-232.
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4.6.3
Seed Oil-Delivering Plants; Seed Oils
4.6.3.1 Soybeans Breene, W.M., Lin, S., Hardman, L., and Orf, J., (1988) Protein and Oil Content of Soybeans from Different Geographic Locations, J. Am. Oil Chem. SOC.65, 1927-1931. Broue, P., Kuzin, V.F., and Alekseeno, B.I., (1977) Biosystematics of Subgenus Glycine v.: Isoenzymatic Data, Aust. J. Bot. 25,555-556. Broue, P., Kuzin, V.F., and Alekseeno, B.I., (1978) CSIRO Annu. Rep. Comonwealth Scient$c and Industrial Research Organization,Canberra, Australia. Caldwell, B.E., (ed.), (1973) Soybeans, Improvement, Production Uses, No. 16 Series Agronomy, American Society of Agronomy, Inc., Publishers, Madison, WI. Christensen, C.M., and Dorworth, C.E., (1968) Influence of Moisture Content, Temperature and Time on Invasion of Soybeans by Storage Funghi, Phytopathology 3,69-84. Christensen, C.M., Dorworth, C.E.,and Kaufmann, H.H., (1971) Biological Processes in Stored Soybeans, in Soybeans: Chemistry and Technology, Vol. I. Proteins, (Circle, S.J., and Smith, A.K., eds.), AVI Publishing, Westport, CT. Chu, Y.H., and Lin, J.Y., (1993) Factors Affecting the Content of Tocopherol in Soyabean Oil, J. Am. Oil Chem. SOC.70, 1263-1268. Circle, S.J., and Smith, A.K., (1971) in Soybeans: Chemistry and Technology, Vol. I. Proteins, AVI Publishing, Westport, CT. Erickson, D.R., (1983) Soybean Oil: Update on Number One, J. Am. Oil Chem. SOC.60, 351-356. Erickson, D.R., (4.) (1995) Practical Handbook of Soybean Processing and Utilization,AOCS Press, Champaign, IL. Erickson, D.R., and Weidexmann, L., (1990) Soybean Oil-Modem Processing and Utilization, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson D.R., ed.),pp. 275-283, American Oil Chemists’ Society, Champaign, IL. Hill, L.D., (ed.)(1976) World Soybean Research, Interstate Printers and Publishers, Danville,
IL. Hymowitz, T., and Newall, C.A., (1981) Taxonomy of the Genus Glycine, Domestication and Uses of Soybeans, Econ. Bot. 35,271-288. Johansson, D., and Bergenstahl, B., (1995) J. Am. Oil Chem. SOC.8. Jurriens, G., (1964) Analysis of Glycerides and Composition of Natural Oils and Fats, in Analysis and Characterizationof Oils, Fats and Fat Products II, (Boekenogen, H.A., ed.), p. 289, Interscience Publishers, London. Markley K.S., (ed.), (195 1) Soybean and Soybean Products, Interscience Publishers, New York. Milner, M., (1951) Biological Processes in Stored Soybeans, in Soybean and Soybean Products, (Markley, K.S., ed.), Interscience Publishers, New York. Probst, A.H., and Judd, R.W., (1973) in Soybeans: Improvement, Production and Uses, (Caldwell, B.E., ed.),American Society of Agronomy, Madison, WI. Rose, LA., (1988) Effects of Moisture Stress on the Oil and Protein Components of Soybean Oil, Aust. J. Agric. Res. 39, 163-70. Smith, A.K., and Circle, S.J., (eds.) Soybeans: Chemistry and Technology, AVI Publishing, Westport, CT. Tanteeratarm, K., Wei, L.S., and Stenberg, M.P., (1989) Effect of Soybean Maturity on Storage Stability and Process Quality, J. Food Sci. 54,593-597. Weiss, E.A., (1983) Soyabean, in Oilseed Crops, pp. 341-401, Longman Verlag, London.
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4.6.3.2 Cottonseed Alderks, O.H., (1948) Cooking of Meats and Recovery of the Oil, in cottonseed and Cottonseed- Products, (Bailey, A.E., ed.),Interscience Publishers, New York. Anonymous (1962) The Wealth of India, Raw Materials, Vol. VI,New Dehli. Bailey, A.E., (1948) Cottonseed and Cottonseed-Products,Interscience Publishers, New York. Black (1948) in Bailey A.E., Cononseed and Cottonseed-Products, Interscience Publishers, New York. Cherry, J.P., (1983) Cottonseed Oil, J. Am. Oil Chem SOC.60,367-368. Clark, S.P., (1980) Quality Oil from Acid Delinted Cottonseed, J. Am. Oil Chem. SOC.57, 376379. Freyer, E., (1934) Additional Data on the Relation of Moisture Content to the Increase of the Free Fatty Acid Content of Cottonseed in Storage, Oil & Soap 11, 162-164. Jones L., (1990) Understanding Cottonseed Oil, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practises, (Erickson, D.R., ed.), pp. 299-305, American Oil Chemists’ Society, Champaign, IL. Jumens, G., (1964) Analysis of Glycerides and Composition of Natural Oils and Fats, in Analysis and Characterizationof Oils, Fats and Fat Products II, (Boekenogen, H.A., ed.), p. 289, Interscience Publishers, London. Murti, K.S., and Achaya, K.T., (1975) Cottonseed, Chemistry and Technology in Its Setring in India, Publications and Information Directorate, New Dehli. Ouedraogo, M.A., and Bezard, J.A., (1982) Les TriglycCrides de 1’Huile de Coton, Rev. Fr. Corps Gras 29, 11-16. Prentice, A.N., (1972) Cotton, with Special Reference to Africa, Longman Group, Ltd., London. Sawan, Z.M., Basyony, A.E., McCuistion, W.L., and El Farra, A.H.A., (1993) Effect of Plant Population Densities and Application of Growth Retardants on Cottonseed and Quality, J. A m Oil Chem SOC.70,3 13-3 17. Seiboldt citation, from Lennerts, L., (1984) Olschrote, Olkuchen, pjkmzliche Fette und Ole, Verlag Alfred Strothe, Hannover. 4.6.3.3 Sunflower Seed Afzalpurkar, A.B., and Lakshimanarayana, G., (1979) Changes in the Seed Characteristics and Oil Composition During Sunflower Seed Maturation, J. Oil Technol. Assoc. Ind. 11,8344. Afzalpurkar, A.B., and Lakshimanarayana, G., (1980) Variations in Oil Content and Fatty Acid Composition with Sunflower Head Size and Shape, J. Am. Oil Chem.SOC.57, 105-106. Anonymous, Proceedings of loth International Sunflower Conference, Australia, March 14-18, 1982. Anonymous, IX Conferencia Intemacional a 2 Girasol, Instituto Nacional de hvestigaciones Agrarias, Torremolinos, 1980. Campbell, E.J., (1983) Sunflower Oil, J. A m Oil Chem. SOC.60,387-392. Carter, J., (ed.),(1978) Sunflower, Science and Technology, Vo1.19, American Soc. of Agron. Madison, WI. Chavan, V.M., (1961) Niger and Sunflower, Indian Central Oilseeds Committee, Hyderabad. Clark, S.P., Wan, P.J., and Matlock S.W., (1980) Pilot Plant Production of Sunflower Seeds Flour, J. Am. Oil Chem.SOC.57, A275-2779. Davidescu, D., Crisan, I., Davidescu, V., and Borza, J., (1977) Zusammenhang zwischen den Umweltbedingungen und dem Olgehalt von Sonnenblumen- und Sojasaat, Proceedings Sunflower Congress, pp. 3 11-327.
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Earle, F.R., Vanettwen, C.H., Clark, T.F., and Wolff LA., (1968) Compositional Data on Sunflower Seed, J. Am. Oil Chem. SOC.45,876-879. English, S.D., McWilliams, J.R., Smith, R.C.G., and Davidson, J.L., (1979) Aust. J. Plant Physiol. 6 , 149-164. Harris, H.C., McWilliam, J.R., and Mason, W.K., (1978) Influence of Temperature on Oil Content and Composition of Sunflower Seed, Aust. J. Agric. Res. 29, 1203-1212. Holt, N.W., and Campbell, S.J., (1984) Effect of Plant Density on the Agronomic Performance of Sunflower on Dryland, Can. J. Plant Sci. 64,599-605. Hurt, E.F., (1948) Sunflowerfor Food, Fodder, and Fertility, Faber & Faber, London. Ivanov, P., Kovacheva, P., and Nokolova, V.,5 (1978) Chemische Zusammensetzung von Sonnenblumenol aus verschiedenen Teilen des Blutenkopfes, Rasteniev”dni Nauki I , 27-3 1. Jaky, M., Kurnik, E., Peredi, J . , Szanto, I., Szabo, R., and Palos, L., (1980) Untersuchungsergebnisse uber Sonnenblumen, Fette, Seifen, Anstrichmittel 82, 110-1 16. Jaky, M., Kumik, E., Peredi, J., Szanto, I., Szabo, R., and Palos, L., (1983) Untersuchungen zur Fettsaurezusammensetzung von Sonnenblumenol, Erniihrungsforschung 28, 142-144. Jumens, G., (1964) Analysis of Glycerides and Composition of Natural Oils and Fats, in Analysis and Characterizationof Oils, Fats and Fat Products 11, (Boekenogen, H.A., ed.), p. 289, Interscience Publishers, London. Leibovitz, Z., and Ruckenstein, C., (1981) Die modeme Verarbeitung von Sonnenblumensaat, Fette, Seifen, Anstrichmittel 83, 534-540. Miller, N., Pretorius, H.E., du Plessis, L.M., and van der Walt, W.H., (1985) The Effect of Hull Lipids on Sunflower Seed Oil Quality, Lebensmittelwissenschaft u. Technologie 18, 333-334. Morrison, W.H., and Robertson, J.A., (1978) Effects of Drying on the Sunflower Seed Oil Quality and Germination, J. Am. Oil Chem. SOC.55,272-274. Morrison, W.H., and Robertson, J.A., (1983) Variation in the Wax Content of Sunflower Seed with Location and Hybrid, J. Am. Oil Chem. SOC.60, 1013-1014. Morrison, W.H., Sojka, R., and Unger, P.W., (1984) Effects of Planting Date and Irrigation on Wax Content of Sunflower-Seed Oil, J. Am. Oil Chem. SOC.6I, 1242-1245. Pemn, J.-L., and Prevot A., (1986) Utilisation d’un Detecteur h Diffusion de la Lumikre Laser dans l’Etude des Corps Gras par CHLP; 11. Analyse des TriglycCrides des Huiles et des Graisses, Rev. Fr. Colps Gras 3 3 , 4 3 7 4 5 . Sallans, H.R., Sinclair, G.D., and Lamour, R.N., (1976) Spontaneous Heating of Flax Seed and Sunflower Seed Stored Under Adiabatic Conditions, Can. J. Res. 22f, 247. Schmidt, L., Marquard, R., and Friedt, W., (1989) Stand und Perspektive der Zuchtung von ‘high-oleid-Sonnenblumen f i r Mitteleuropa, Fat Sci. Technol. 91,346-349. Veldstra, J., and Klere, J., (1990) Sunflower Oil, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 284-288, American Oil Chemists’ Society, Champaign, IL. Weiss, E.A., (1983) Sunflower, in Oilseed Crops, pp. 402-462, Longman Verlag, London. 4.6.3.4 Peanuts Anonymous, (1978) The Philippines Recommendationsfor Peanuts, The Philippines Council for Agriculture and Resources Research.
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Anonymous, (1973) Peanuts-Culture and Uses,A Symposium, American Peanut Research and Education Association, Stone Printing Co., Roanoake, VA. Arthur, J.C., (1951) Proteins for Special Diets, Peanut J. Nutr. World 21,30. Ayres M., (1983) Peanut Oil, J. Am. Oil Chem. SOC.60,357-359. Desikachar, H.S.R., De, S . S . , and Subramanyam, V., (1946) Nutritive Value of Peanut ‘Milk,’ Sci. Cult. 12, 151. Diener, U.L., and David, N.D., (1966) Aflatoxin Production by Isolates of Aspergillusflavus, Phytopathology 56, 1390. Juniens, G., (1964) Analysis of Glycerides and Composition of Natural Oils and Fats, in Analysis and Characterizationof Oils, Fats and Fat Products II, (Boekenogen, H.A., ed.), p. 289, Interscience Publishers, London. O’Keefe, S.F., Wiley, V.A., and Knauft, D.A., (1993) Comparison of Oxidative Stability of High- and Normal-Oleic Peanut Oils, J. Am. Oil Chem. SOC. 70,489-492. Kelkar, G.M., (1950) Groundnut Milk and Curd, Sci. Cult. 16, 16. Ory, R., and Flick, G., (1990) Peanut Oil-Chemistry and Properties, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 306-308, American Oil Chemists’ Society, Champaign, IL. Pattee, H.E., and Young, C.T., (eds.), (1982) Peanut Science and Technology, American Peanut Research and Education Society, Inc., Yoakum, TX. Sanders, T.H., (1993) Groundnut Oil, in Encyclopaedia of Food Science, Food Technology and Nutrition, p. 4670, Academic Press, London. Singleton, J.A., Pattee, H.E., (1987) Characterization of Peanut Oil triacylglyterols by HPLC, GLC and E M S , J. Am. Oil Chem. SOC.64,534-538. Subramanyam, V., Narayan Rao, M., and Swaminathan, M., (1957) The Nutritive Value of Low Fat Groundnut Flour, Bull. Can. Food Technol. Res. Inst. 5,6. Weiss, E.A., (1983) Groundnut, in Oilseed Crops, pp.100-160, Longman Verlag, London. Wilson C.T., (ed.), (1973) Peanuts-Culture and Uses, American Peanut Research and Education Society, Inc., Stillwater, OK. Woodroof, J.G.,( 1966) Peanuts: Production, Processing, Products, AVI Publishing, Westport, CT. 4.6.3.5 Rapeseed Ackman, R.G., and Sebedio, J.-L., (1981) The Minor Fatty Acids in Rapeseed Oil, Proceedings 5th International Rapeseed Conference,Vol. II, pp. 9-12. Ackman, R.G., (1984) Chemical Composition of Rapeseed, in High and Low Erucic Rapeseed Oil, (Kramer, J.K.G., Sauer, F.D., and Pigden, W.J., eds.), Academic Press, London. Alter, M., and Gutfinger, T., (1982) Phospholipids in Several Vegetable Oils, Riv. Ital. Sost. Grasse 59, 14-18. Appelqvist, L.-A,, (1969) Lipids in Cruciferae IV,Fatty Acid Patterns in Single Seeds and Seed Populations of Various Cruciferae and in Different Tissues of Brassica napus, Hereditas 61,943. Appelqvist, L.-A., (1969) Lipid Patterns of Some Cruciferae, Riv. Ital. Sost. Grasse 46,478487. Appelqvist, L.-A., (1970) in Rutkowski (ed.), International Symposium for the Chemistry and Technology of Rapeseed Oil and Other Cruciferae Oils, Warsaw. Appelqvist, L.-A,, and Ohlsson R. (eds.), (1 972) Rapeseed: Cultivation, Composition, Processing and Utilization,Elsevier, Amsterdam.
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Carr, R., (1990) RapeseedJCanola, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 289-298, American Oil Chemists’ Society, Champaign, IL. Diepenbrock, W., (1984) EinfluB der Temperatur auf die Fettsaurezusammensetzung von Triglyceriden und Galaktolipiden aus Rapssamen, Zeitschnji f i r Acker- und PJlanzenbau 153,208-215. Downey, R.K., (1963) Oil Quality in Rape Seed, Can. Food Ind. 34,34. Kramer, K.G., Sauer, F.D., and Pigden, W.J., (eds.), (1983) High and Low Erucic Rapeseed Oils, Production, Usage, Chemistry and Technological Evaluation, Academic Press, Toronto. Mag, T.K., (1983) Canola Pressing in Canada, J. Am. Oil Chem. SOC.60,380-384. Ohlofson, J.S.R., (1983) Rapeseed Oil, J. Am. Oil Chem. SOC. 60, 385-386. Peterson, B., Potlaka, O., and Toregard, B. (1981), HPLC Separation of Natural Oil Triglycerides into Fractions with the Same Carbon Number and Numbers of Double Bonds, J. Am. Oil Chem. SOC.58, 1005-1009. PrBvot, A., Pemn, J.L., Laclaverie, G., Auge, P., and Coustille, J.L., (1990) A New Variety of Low Linolenic Rapeseed Oil; Characteristics and Room Odor Tests, J. Am. Oil Chem. SOC. 67,161-165. Rapeseed Conference, Proceedings of the 5th International, Malmo, June 12-16, 1978. Rapeseed and Rapeseed Products, International Conference on the Science, Technology, and Marketing, St-AdBle,QuBbec, Sept. 20-23, 1970. RapskongreD,Protokolle des 4. Internationalen, Giessen, 4.-8. Juni 1974. Robbelen, G., (1983) Fortschritte in der Welterzeugung von Rapssaaten, Fette, Seifen, Anstrichrnitel85, 395-398. Sebastian, J., (1985) New Food Oils. Rapeseed Approved for US.Consumption, Bakers Digest 8,59. Sebedio, J.-L., and Ackman, R.G., (1979) Some Minor Fatty Acids of Rapeseed Oil, J. Am. Oil Chem. SOC.56, 15-21. Sehevic, D., Jovanivic, K., Basic, V., Stojak, L., Koludrovic, B., Jesic, L., Balzer, I., and Hrust, V., (1980) Qualittit und Menge des 61s und der Glucosinolate in Rapsol, Hrana i Zshrana 21,4749. Signoret, A., and Vermeersch, G., (1988) Le DBpelliculage des Grains de Colza: Premiers Rtsultats Indusrriels, Rev. Fr. Corps Gras 35,391-96. Sorensen, H. (ed.), (1985) Advances in the Production and Utilization of Cruciferous Crop, Martinus Nijhoff/Dr. W. Junk Publishers, for the Commission of the European Communities, Dordrecht. Weiss, E.A., (1983) Rapeseed, in Oilseed Crops, pp. 161-215, Longman Verlag, London. 4.6.3.6 Coconuts Child, R., (1964) Coconuts, Longmans, London, (2nd ed. 1974). Dale, A.P., and Meara, M.L., (1955) Component Fatty Acids and Glycerides of Coconut Oils, J. Sci. FoodAgric. 6,162-166. Fremond, Y., Ziller, R.,de Nuce de Lamonthe, D., (1966) The Coconut Palm, International Potash Institute, Bern. Ignacio, L.F., (1985) Present and Future Position of Coconut Oil in World Trade, J. Am. Oil Chem. SOC.62,197-203.
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Montenegro, H.M., (1985) Coconut Oil and Its Byproducts, J. Am. Oil Chem SOC. 62,259-260. Thampan, P.K., (1981) Handbook on Coconut Palm, Oxford and IBH Publishing Co., New
Dew. Woodroof, J.G., (1979) Coconuts: Production, Processing, Products, AVI Publishing Co., Westport, CT Young, F.V.K. (1983), Palm Kernel and Coconut Oils: Analytical Characteristics, Process Technology and Uses, J. Am. Oil Chem. SOC. 60,374-379. 4.6.3.7 Sesame Seed Anonymous, (1988) Unterkommission fiir pflanzliche Ole ‘SesamB1; Characteristica und Analysenmethoden’, Riv. Ital. Sos. Grasse 65,4546. Burkhill, I.H., (1953) Habits of Man and the Origins of Cultivated Species of the Old World, Proc. Linn. SOC.London 164, 1241. Fukuda, Y., and Namiki, M., (1988) Recent Studies on Sesame Seed and Oil, J. Jpn. SOC.Food Sci. Technol. 35,552-562. Montilla, D., (1977) Arawaca, an Early Variety of Sesame, Agron. Trop. 27,483487. Osman, H.E., (1988) Relationship Between Seed Yield, Oil Content and Their Components in Sesame, Acta Agron. Hung. 37,287-292. Ouedraogo, M.A., and Bezard, J.A., (1981) Structure GlycBridique de 1’Huile de SBsame, Rev. Fr. C o q ~ Gras s 28,473476. Sarkar, S., and Bhattachqya, D.K., (1987) Seed Composition of Some New Varieties of Sesame, J. Oil Technol,Assoc. Ind. 19, 13-15. Weiss, E.A., (1971) Castor, Sesame and Saflower, Leonard Hill, London. Weiss, E.A., (1983) Sesame, in Oilseed Crops, pp. 282-340, Longman Verlag, London. 4.6.3.8 Palm Kernels Carsten, H.A., Hilditch, T.P., and Meara, M.L., (1945) The Component Acids of the Testa and Kernel Fats of the Oil Palm,J. SOC. Chem. Znd. 64,207. Dale, A.P., and Meara, M.L., (1955) Component Fatty Acids and Glycerides of Coconut Oils, J. Sci. FoodAgnc. 6,162-166. Graalmann, M., (1990) Laurics (Coconuflalm, Kernel), in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.),pp. 270-274, American Oil Chemists’ Society, Champaign, IL. Hartley, C.W.S., (1957) The Oil Palm, Longman, London. Johannsson, D., and Bergenstahl, B., (1995) J. Am. Oil Chem. SOC. 72. Southworth, A., (1985) Palm Oil and Palm Kernels, J. Am. Oil Chem. SOC.62,250-253. Young, F.V.K., (1983) Palm Kernel and Coconut Oils: Analytical Characteristics, Process Technology and Uses, J. Am. Oil Chem. SOC. 60,374379. 4.6.3.9 Linseed Green, A., and Marshall, D.R., (1981) Variations for Oil Quantity and Quality in Linseed. Aust. J. Agric. Res. 32,599-607. Haumann, B.F., (1990) Low Linolenic Flax: Variation on Familiar Oilseed, INFORM I , 934-941. Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constitution of Natural Fats, Chapman & Hall, London.
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Kaufmann, H.P., and Keller, M., (1929) Die rhodanometrische Bestimmung linolensaurereicher Fette, Analyse des Leinols, Z. angew. Chem. 42, 2&23,73-76. Rose, W.G., and Jamieson, G.S., (1941) The Composition of Seven American Linseed Oils, Oil andSoap 18,173-174. Schuster, W., Marquard, R., and Iran-Nejad, H., (1978) Uber die Veranderung einiger Qualitatsmerkmale bei verschiedenen Olleinsorten unter kontrollierten Klimabedingungen, Fette, Seifen, Anstrichmittel SO, 173-180. 4.6.3.10 Safflower Seed Earle, F.R., Wolff, LA., Mallan, J., Bagley, M.O., and Wolff, I.A., (1960) Search for New Industrial Oils II: Oils with High Iodine Value, J. Am. Oil Chem SOC.37,48. Edwards, W.G.H., and Robb, A.J.D., (1951) Studies on Linseed Oil I, the Unsaturated Fatty Acids of Some New Zealand Linseed Oils, J. Sci. Food Agric. 2,429-430. Griffiths, H.N., Hilditch, T.P., and Jones, E.C., (1934) The Oleic-Elaidic Acid Transformation as an Aid in the Analysis of Mixtures of Oleic, Linoleic and Linolenic Acids, J. SOC. Chem. Ind. 53, 13T, 75-8 1T. Gunstone, F.D., and Hilditch, T.P., (1946) The Use of Low Temperature Crystallization in the Determination of Component Acids of Liquid Fats II: Fats Which Contain Linolenic as Well as Linoleic Acids, J. SOC.Chem. Ind. 65, 8-13. Hilditch, T.P., and Seavell, A.J., (1950) The Component Glycerides of Drying Oils 11,. Linolenic-Rich Oils, J. Oil Chem. Assoc. 33,24. Hilditch, T.P., Bridge R.E., and Seavell, A.J., (1951) Variations in the Composition of Some Linolenic-Rich Seed Oils, J. Sci. Food Agric. 2,543-547. Jurriens, G., (1964) Analysis of Glycerides and Composition of Natural Oils and Fats, in Analysis and Characterization of Oils,Fats and Fat Products II, (Boekenogen, H.A., ed.), p. 289, Interscience Publishers, London. Kaufmann, H.P., and Keller, M., (1929) Die rhodanometrische Bestimmung linolensaurereicher Fette, Analyse des Leinols, Z. angew. Chem. 42,20-23,73-76. Mary, W., Crombie, L., Comber, R., and Boatman, S.G., (1955) The Estimation of Unsaturated Fatty Acids by Reversed Phase Partition Chromatography, Biochem. J. 59,309. Sallans, H.R., and Sinclair, G.D., (1944) Relation Between Iodine Value and Fatty Acid Composition of Linseed Oil, Can. J. Res. 22, 132. Smith, J., (1990) Safflower, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 324330, American Oil Chemists’ Society, Champaign, IL. Weiss, E.A., (1971) Castor, Sesame and Saflower, Leonard Hill, London. Weiss, E.A., (1983) Safflower, in Oilseed Crops, pp. 216-281, Longman Verlag, London. 4.6.3.7 1 Cocoa Beans Boekenoogen, H.A., (1968) Analysis and Characterization of Oils, Fats and Fat Products, Interscience Publishers, London. Coleman, M.H., (1961) Further Studies on the Pancreatic Hydrolysis of Some Natural Fats, J. Am. Oil Chem. SOC.38,685. Fincke, H., (1965) Handbuch der Kakaoerzeugnisse, Springer Verlag, Berlin. Isler, H., (1960) Kakao und Schokolade, in Ullmanns Enzyklopiidie der Technischen Chemie, Vol. 9, pp. 164173, Verlag Urban und Schwarzenberg, Miinchen. Kickarts. R., (1987) Der Puringehalt des Rohkakaos in Abhangigkeit vom Kakaobohnengewicht,Z. Lebensm. u. gerichtl. Chemie 41, 130-132.
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Knapp, A.W., (1946) Rev. Int. Choc. 1. Knapp, A.W., (1 955) Die Kakaobutter-Kennzahlen und deren Bestimmungsmethoden, Int. Fachschr. Schokolade-Industr. 10,42-54. Lange, H., and Fincke, A., (1969) Kakao und Schokolade, in Handbuch der Lebensmittelchemie, Vol. VI,pp. 2 10-304, Springer-Verlag, Berlin. Lindner, (1953) Kakao und-erzeugnisse, Verlag A.W. Hayn’s Erben, Berlin. Meara, M.L., (1949) Configuration of Naturally Occuring Mixed Triglycerides V: The Configuration of the Major Component Glycerides of Cocoa Butter, J. Chem. SOC., 2 154-2 157. Meursing, E.H., (1976) Kakaopulver f i r die verarbeitende Industrie, Kakaofabrik de Zaan Holland. Rohan, T.A., (1963) Processing of Raw Cocoafor the Market, F A 0 Study No. 60, Rome. Wirth, W., (1955) Kakaobohnen-Untersuchungen aus den Liefemngen 1952-54, Zucker und Sugwarenwirtschaji 8,801-808. Zurcher, K., (1988)Kakao, in Lebensmitteltechnologie,Springer Verlag, Berlin. 4.6.3.12 Corn Germ
Jurriens, G., (1964) Analysis of Glycerides and Composition of Natural Oils and Fats, in Analysis and Characterization of Oils, Fats and Fat Products 11, (Boekenogen, H.A., ed.), p. 289, Interscience Publishers, London. Leibowitz, Z., and Ruckenstein, C., (1983) Our Experiences in Processing Maize Germ Oil, J. Am. Oil Chem. SOC.60,395-399. Saker, A,, Fahmy, A.A., and Roushdi, M., (1986) Evaluation of Some Chemical Components in Wheat, Maize and Rice Germ Oil, Grasas y Aceites 37, 134-136. Stolp, K.-D., (1988) Maisstkrke, in Lebensmitteltechnologie, Springer Verlag, Berlin. Strecker, L., Maza, A., and Winnie, G.,( 1990) Corn Oil-Composition, Processing and Utilization, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practises, (Erickson, D.R., ed.), pp. 309-323, American Oil Chemists’ Society, Champaign, IL. 4.6.3.13 Olive Kernels (See Olives) 4.6.3.14 Babassu
Adames, G.E., (1943) Babassu, a Hard Nut to Crack, Agriculture of the Americas 10, 3. Anonymous, (1975) Underexploited Tropical Plants with Promising Economic Value, Report of an Ad Hoc Panel of the Advisory Committee on Technological Innovation, Board on Science and Technology for International Development Commission on International Relations. Balick, M.J., and Pinheiro, C.U.B., 0 Que e Babacu, Special Palm Symposium Presented at the 36th Congress0 Nacional de Botanica, Curitaba, Parana, Brazil 1985, citation from Robbelen G., Downey R.K., Ashri A., (eds.), Oil Crops ofthe World. Balick, M.J., Pinheiro, C.U.B., and Gershof, S.N., (1977) Nutritional Evaluation of the Jessenia batua Palm: Source of High Quality Protein and Oil from Tropical America, E o n . Bot. 35,261-271. Gonsalvez, A.D., (1955) 0 Babacu, Ministerio da Agicultura, Rio de Janeiro, Brazil. Inmay H., (1949 Cochabamba, Bolivia) The Cusi Palm, 0 Phalerate and Babassu Oil, Revista de Agricultura 6,29.
3 42
Fats and Oils Handbook
Markley, K.S., (1971) The Babassu Oil Palm of Brazil, Economic Botany 25,267-304. de Silva, S.A.F., (1971) Primeira Contribuacao ao Catalog0 Sistematico de Plantas Brasileiras Produtoras de Olio, Ministerio da Agricultura,Rio de Janeiro, Brazil. Vivacqua, A., (1957) Exploitation Rationelle du Babassu au Bresil, Oliaginewr 12,697-700. Weiss M., (1955) Le Babassu, Richesse Nationale du Bred, Oliagineux 10,839-843. 4.6.3.15 Grape Seed Galan, M., Martinez Massanet, G., Montiel, J.A., Pando, E., and Rodriguez, Luis F., (1986) Studien an agrarischen Nebenprodukten I: Extraktion, physikalische Daten und Fettsaurezusammensetzung von Palomino Traubenkemol, Grasas y Aceites 37, 179-1 82. Martinez Massanet, G., Montiel, J.A., Pando, E., and Rodriguez, Luis F., (1986) Studien an agraxischen Nebenprodukten II: Fettsaurezusammensetzungvon Palomino Traubenkemol, Grasas y Aceites 37, 233-236. 4.6.3.7 6 Niger Seed Dunn, H.C., and Hilditch, T.P., (1950) African Drying Oils II: Components of Some LinoleicRich Oils; Niger-Seed Oil, J. SOC. Chem Ind. 69, 13-15. Weiss, E.A., (1983) Crambe, Niger, and Jojoba, in Oilseed Crops, pp. 463-527, Longman Verlag, London. 4.6.3.17 Borneo Tallow, Shea Butter Meara, M.L., and Zaky, A.H., (1940) Fatty Acids and Glycerides of Seed Fats of Allanbackia floribunda andparviflora, J. SOC. Chem. Ind. 59,26. Sawadogo, K., and BBzard J., (1982) Etude de la Structure Glyceride du Beurre de KaritC, Olkgineux 37,69-74. 4.6.3.18 Walnut Oil Mehran, M., (1974) Oil Characteristicsof Iranian Walnuts, J. A m Oil Chem. SOC. 51,477-478. 4.6.3.19 Rice Bran Oil Anonymous, (1985) Rice Bran: An Under-Utilized Raw Material, United Nations Industrial Development Organization,Wien. Bhattacharyya,A.C., Majumdar, S., and Bhattacharyya, K., (1987) Refining of High FFA Rice Bran Oil by IsopropanolExtraction and Alkali Neutralisation,Oleaginewr 42,431-433. Chakrabarty, M., (1990) Rice Bran-a New Source for Edible and Industrial Oil, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 331-340, American Oil Chemists’ Society, Champaign,IL. Choi, S.A., and Park, Y.H., (1983) Studies on the Triglyceride Composition of Rice Bran Oil, Korean J. Food Sci. Technol. 15,108-1 11. Dasgupta, J., Bhattacharyya, D., Chakrabarty, M.M., and Adhika~i,S., (1981) A New Method for Glyceride Composition Determination by Colorimetry, J. Am. Oil Chem. SOC. 58, 6 13-615. Fedeli, E., (1983) MiscellaneousExotic Oils, J. Am. Oil Chem. SOC. 60,404-406. Gupta, H.P., (1989) Rice Bran Offers India an Oil Source, J. A m Oil Chem. SOC. 66,620-623.
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Hemavathy, J., and Prabhakar, J.V., (1987) Lipid Composition of Rice (Oryza sativa L)Bran, J. Am. Oil Chem. SOC.64, 1016-1019. Kim, C.J., Byun, S.M., Chegh, H.S., and Kwan, T.W., (1987) Comparison of Solvent Extraction Characteristics of Rice Bran Pretreated by Hot Air Drying, Steam Cooking and Extrusion, J. Am. Oil Chem. SOC.64,514-516. Murti, K.S., and Dollear, F.G., (1948) Rice Bran Oil. Composition of Oil Obtained by Solvent Extraction, J. Am. Oil Chem. SOC.25,211-223. Nasirullah, H., Krishnamurty, M.N., and Nagaraja, K.V., (1989) Effect of Stabilization on the Quality Characteristics of Rice-Bran Oil, J. Am. Oil Chem. SOC.66,661663. Palipane, K.B., and Swamarisi, C.D.P., (1985) Composition of Raw and Parboiled Rice Bran from Common Sri Lankan Varieties and from Different Types of Rice Mill, J. Agric. Food Chem. 33,732-734. Prabhakar, J.V., (1988) Rice Bran Processing for Oil and Meal, in Trends in Food Science and Technology, (Raghavendra Rao, M.R., ed.), pp. 468-474, Mysore, India. Ramakrishna, P., Subramanian, R., Manohar, B., and Venkatesh, K.V.L., (1988) Moisture Content, Strength and Extractability of Rice Bran Pellets, J. Food Eng. 7,281-287. Swift, C.E., Fore, S.P., and Dollear, F.G., (1950) Rice Bran Oil. Stability and Processing Characteristics of Some Rice Bran Oils, J. Am. Oil Chem. SOC.27, 14-16.
4.6.4 Nonedible Fats and Oils 4.6.4.1 Castor Beans Weiss, E.A., (1971) Castor, Sesame and Safflower, Leonard Hill, London. Weiss, E.A., (1983) Castor, in Oilseed Crops, pp. 31-99, Longman Verlag, London. 4.6.4.. Tung Oil Fonrobert, E., (1951) Das Holzol, Berliner Union Verlag, Stuttgart. 4.6.4.3 lojoba Anonymous, Proceedings of the I979 Arizona Jojoba Conference,Tucson, 1980. Anonymous, (1985) Jojoba, New Crop for Arid Lands, New Material for Industry, Report of the Ad Hoc Panel on Technology Innovation, Board of Science and Technology for International Development, Office of International Affairs, National Research Center, National Academy Press, Washington, DC. Anonymous, (1977) Jojoba, Feasibiliryfor Cultivation on Indian Reservation in the Sonoran Desert Region, Committee on Jojoba Production Systems Potential Board on Agriculture and Renewable Resources, Commission on Natural Resources, National Research Council, National Academy of Science, Washington, DC. Baldwin A.R., (ed.), (1988) Seventh International Conference on Jojoba and Its Uses, American Oil Chemists’ Society, Champaign, IL. Miwa, T.K., (1971) Jojoba Oil Wax Esters and Denvated Fatty Acids and Alcohols: Gas Chromatography Analyses, J. Am. Oil Chem. SOC.58,259-264. Miwa, T.K., and Rothfus, J.A., (1979) J. Am. Oil Chem. SOC.56,65. Yermanos, D.M., (1975) The Composition of Jojoba Seed During Development, J. Am. Oil Chem. SOC.52, 115. Yermanos, D.M., (1974) Agronomic Survey of Jojoba in California, Econ, Bot. 28, 160.
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Weiss, E.A., (1983) Crambe, Niger, and Jojoba, in Oilseed Crops, pp. 463-527, Longman Verlag, London. Wisniak, J., (1988) The Chemistry of Jojoba, American Oil Chemists’ Society, Champaign, IL.
4.6.5 Alternative Sources for Oils and Fats Asselineau, J., (1962) Les Lipids Bactkriens, Henmann-Verlag, Paris. Bird, C.W., and Molton, P.M., (1972) The Production of Fatty Acids from Hydrocarbons by Microorganisms, in Topics in Lipid Chemistry 111, (Gunstone, F.D., ed.), pp. 125-170, Elek Science, London. Boulton, C.A., (1982) Ph.D. Thesis, University of Hull. Calvin, M., (1979) Petroleum Plantations for Fuel and Materials, BioScience 29,533. Glatz, B.A., Hammond, E.G., Hsu, K.H., Baehman, L., Bati, N., Bednarski ,W., Brown, D., and Floetenmeyer, M., (1984) Production and Modification of Fats and Oils by Yeast Fermentation, in Biotechnology for the Oils and Fats Industry, (Ratledge, Dawson, and Rattray, eds.), American Oil Chemists’ Society, Champaign, IL. Kates, M., (1964) Bacterial Lipids, in Advances in Lipid Research II, (Paoletti, R., and Kritchevsky, D., eds.), pp. 17-90, Academic Press, New York. Kormendy, A.G., and Wayman, M., (1974) Characteristic Cytoplasmic Structures in Microorganisms Utilizing n-Butane and n-Butanol, Can.J. Microbiol., 225. Michanek, G., (1978) Trends in Applied Phycology, with a Literature Review: Seaweed Fanning on an Industrial Scale, Bot. Mar. 21,469-475. Murali, H.S., Singh, L., Sankaran, R., and Sharma, T.R., (1987) Biosynthesis of Oil by Fusarium spp., Lebensm-Wiss. u. Technol. 20,296-299. Princen, L.H., (1979) New Crop Developments for Industrial Uses, J. Am Oil Chem Soc.56, 845. Ratledge, C., (1982) Microbial Oils and Fats: An Assessment of Their Commercial Potential, Prog. Ind. Microbiol. 16, 119-126. Ratledge, C., Dawson, P., and Rattray, J., (4s.) (1984) Biotechnology for the Oils and Fats Industry, American Oil Chemists’ Society, Champaign, IL. Ratledge, C., and Wilkinson, S.G., (1988) Microbial LipidF, Academic Press, London. Shifrin, N.S., (1980) Ph.D. Thesis, Massachusetts Institute of Technology, Cambridge, MA. Shifrin, N.S., (1984) Oils from Microalgae, in Biotechnology for the Oils and Fats Industry, (Ratledge, Dawson, and Rattray, eds.), American Oil Chemists’ Society, Champaign, IL. Shifrin, N.S., and Chisholm, S.W., (1980) in Algal Biomass: Production and Uses, (Shelef, G., and Soeder, C.J., eds.), ElseviedNorth Holland Biomedical Press, Amsterdam. Wayman, M., Jenkins, A.D., and Kormendy, A.G. (1984), Bacterial Production of Fats and Oils, in Biotechnology for the Oils and Fats Industry, American Oil Chemists’ Society, Champaign, IL. Woodbine, M., (1959) Microbial Fat: Micro-Organisms as Potential Fat Producers, Prog. Id. Microbiol., 179.
Chapter 5
The Extraction of Vegetable Oils The extraction of oils and fats is a craft that has been carried out since mankind's earliest days. The production of oils and fats has long been associated with certain professions, depending on the source of the oil and fat, for example, milk fats with alpine herdsmen and alpine dairies, today with industrial dairies; rendering fats with butchers, slaughter houses and Medieval oil mill t rendering plants; fish and whale 18th century French oil mill & oil with fishermen and whale hunters; and vegetable oils with oil mills. The production method of the oils depends on the raw material. The only raw materials that can be stored without quality deterioration for a long period are oilseeds. Under good storage conditions, the time between two harvests can easily be bridged. The situation for oil fruit delivering pulp oils is totally different. Immediately after harvesting Courtesy of Margarineinstitut fur gesunde Ernahrung, Hamburg, Germany. (and for some fruit already during ripening), enzymic degradation reactions start that quickly deteriorate the oil quality substantially. Therefore, these fruit are mainly processed close to the place of harvest. The same holds true for animal fats that are also enzymically preloaded and thus attacked as a result of the slaughtering process. Milk fat is also processed immediately after milk production because milk is very sensitive to spoilage. In addition, immense storage and cooling capacities for adequate storage would be required for a product containing 90% water and only -4% fat. Furthermore, production of milk fat is usually done from deepfrozen butter. The production of animal fats is described in Chapter 3; in the following, the production of fats and oils from vegetable sources is described exclusively. These sources are discussed in greater detail in Chapter 4. 345
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346
5.0 Summary Pulp oils are produced close to the production location of the oil fruit. As a pretreatment, palm fruit are cooked (and thus sterilized) and the fruit is then separated from the bunch stalk; olives are only crushed. Then the oil is extracted by pressing and the must is centrifuged. The press cake from pulp oils can be dried and used as combustible material, thus providing part of the energy needed for their production. Oilseeds can be stored and transported easily. Vegetable oils are therefore extracted close to the consumer. As a pretreatment, oilseeds are cleaned, possibly dehulled, reduced, heat-treated and flocculated. The oil of all oil fruit can be press-extracted; oilseeds can be solvent extracted. The press and extraction meal from seed oil production is usually used as fodder. Figure 5.1 gives an overview of the different processes.
5.1 Pulp Oils Because of the quick spoilage of the oil fruit that deliver pulp oils and the completely different and difficult matrix compared with seed oils, pulp oil production has developed as an independent technology. In the following, the production of the two most important pulp oils, palm oil and olive oil, is described. Palm fruits and olives as such are described in Chapter 4.2. 5.1.1 The Production of Palm Oil
In the home country of palm oil, West Africa, thousands of small plants extract palm oil for the marketplace in their vicinity, which is usually their own village. Oil produc-
Oil tor technical usage
Remainder
+
+
t
-P
C
Meal (Animalfeed) t
011
Fig. 5.1.
Flow chart of vegetable oil extraction.
C
Extraction of Vegetable Oils
347
tion there follows traditional methods, i.e., fermentation of the fruit, separation of the pulp and the kernels, sterilization, size reduction and crushing, press extraction and clarification of the oil. For fermentation, the fruit bunches are stored for 3 4 d. Thereafter, the pulp and the kernels are separated and sterilized by cooking them for 1 h. Drums of -200-L capacity are normally used for this purpose. Sometimes the fruit are cooled and then trampled down. Trampling down is often carried out in a wooden tub called a canoe. Usually, however, this is done by beating with wooden clubs. The mixture of nuts and pulp is deoiled in screw presses. For clarification, the upper foamy part of the water-oil mixture is decanted and cooked. The yield of this kind of oil extraction is between 40 and 65%. The industrial process of palm oil extraction is usually also done in decentralized smaller plants because palm fruits easily spoil and therefore cannot be transported over long distances. In principle, oil extraction follows the ancient method; however, almost all processing steps are mechanized (Fig. 5.2). In many parts of the world (especially South East Asia, Malaysia, and Indonesia), this industry developed explosively; thus, these small factories (Fig. 5.3) are frequently most modernly equipped. At the moment of harvest, the free fatty acid content of palm oil is ~ 1 %It. then increases rapidly, thus requiring precise coordination between harvesting and processing.
I
Palm fruit II Steriiiiation of the
(Bunches)
1
2.5-3bar. 130-135'C. 54-75 min Autoclaver (1.5 b i 20 t mntent): capadty per line up to 10 tlh inactivation of lipomc enzymes: opening of WIIS FNU loosened (up to 99.5%) provided that steriluatbn is well done Rotary dlum stripper with buffles; capadty per line up to 32 tlh >>>
-)
Cooking
Presring
Separation
W1OO'C. 20-30 min 3 5 m' content; (up to 10 t/h of bunches)
-
Stems, stalkr, =3 Q f r u w parta of bunches
back to plantation as fertiiiier
Suaw prcnses (up to 20 Vh): residual oil c 7 1 , broken kernels c 5%
Vibrating screen or settling tanks (separation of mapr foregn material)
Heatrng to ca 98'C
Nuts
Fibers
(see438) Separators >>>Vegetationwater >>> Water < 0 1%
to environment
1
ccc Water IBOD<100mq/I) Fmtiiuer to plantahon <<< Sludae
Crude palm oil
Fig. 5.2. Flow chart of palm oil production with presses.
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Fig. 5.3. Palm oil mill with fruit bunches prepared for sterilization (above) and feeding a sterilizer (below); courtesy of PORIM and schematic drawing of 197Os, local palm oil mill (after Usine de Wecker SAr.l., Luxemburg, courtesy of Gandes).
5.1.7.7 Sterilization of the Fruit Bunches. The first operation in palm oil processing is the sterilization of the fruit bunches, which disintegrates the bunch, loosens the fruit and facilitates the separation of the nuts; an important secondary effect is the inactivation of enzymes and microorganisms. Their activity would otherwise increase the amount of free fatty acids. Sterilization is done in autoclaves, which are fed with small wheeled vessels holding the bunches. The autoclave is heated with steam of 2.5-3 bar to 130-135°C and held at that temperature for 50-75 min. Well-pollinated bunches of fruit develop a very dense fruit package that is much more difficult to penetrate with the steam; therefore the holding time must be increased. An autoclave can hold as much as 20 ton of palm fruit. Including loading and discharge, the process takes -2 h. This results in a capacity of -10 to& and per autoclave. 5.1.7.2 Separation of the Nuts and the Pulp from the Stalk. After sterilization, the stalk tissue is softened and the nuts sit loose. The bunches are then threshed and the fruit are thereby beaten off the stalk. To do so, the fruit pass through a horizontal cylindrical rotating cage (rotary drum stripper) equipped with iron bars.
Extraction of Vegetable Oils
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While passing through this cage, the fruit (consisting of the pulp hull and the kernel) are beaten off the bunch. The cage is constructed of longitudinal channel bars that allow the fruit to fall through once they are detached from the stalk. After coarse impurities are removed, the nuts are separated from the hull. This is done by a mechanical squeezing and stirring process that lasts -20 min. During this operation, the pulp of the nut hulls separates from the nuts and a homogeneous oily mash is prepared and fed to the press. The efficiency that can be reached in this process (called digestion) depends largely on good sterilization. Big rotary drum strippers have a capacity of up to 32 ton/h.
5.7.1.3 Pressing and Working Up. The majority of mashed pulp and nuts is expelled in a press. Such presses have a capacity of up to 15 to&. Ramecourt (1976) reported that the oil loss in the dried fibers was <6%. The proportion of broken nuts in the residue should be <5%. The press liquor consists of more than one third palm oil. The rest consists of water, turbid components and impurities such as sand. The press liquor passes a settling tank and is then separated by centrifugation. The yield can be improved if the mix is heated to <100"C before separation. The press cake is removed with a screw, shredded, and the nuts are separated from the rest with paddles. They are dried, broken, and the fat from the kernel is extracted (see Chapter 4.3.8.). The palm oil is polished and dried before being sent to storage. 5. 7. 7.4 Waste Disposal and Recycling. The hard hulls of the nuts can be used in the boiler house for energy production. They have a caloric value of -17 MJMT (4000kcaVMT). The same holds true for stalks, stems and the residual extracted pulp. The energy required to process 1 ton of fruit bunches, -500 kg of steam and 20-22 kWh electrical energy, can be generated mainly by processing the waste. Increased attention is given to environmental aspects. Hirsinger and Knaut (1994) describe the approach as one that produces as little waste as possible and reintegrates as much of the material as possible into the plantation cycles. They describe the different side products that stem from the extraction process, i.e., palm oil mill effluent, a liquid mixture containing fat, fibers, mineral components and ash; palm oil mill effluent sludge, stemming from clarified palm oil mill effluent; ash from incineration (energy generation); empty fruit bunches; surplus palm nut hulls (used for road construction); and decanter solids (rich in nutrients, used as fodder). Water is released into the environment if it meets the prescribed environmental standards (Biological Oxygen Demand (BOD) < 100 mg/L). Some years ago, old palm trees were burned; now they are mechanically reduced in size and dispersed in the plantation. Slightly >20% wt/wt of the fruit bunches entering the mill has to be disposed off as empty fruit bunches. The residues that were formerly burned had found use as a fertilizer. However, the organic part was lost. Now the empty bunches are brought back to the soil. The same is done with the digested sludge from effluent treatment.
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5.1.2 Olive Oil Production
After harvesting, olives are exposed to enzymic processes that call for immediate processing to avoid fat splitting. Therefore, the oil is usually processed in small plants close to the farms. Olive oil is contained in the pulp as well as in the kernels. Its botany, economic importance and the harvesting methods used as well as its composition are described in Chapter 4.2.2 (pulp oil) and Chapter 4.3.13 (olive kernel oil). Figure 5.4 shows the improvement in the olive oil extraction process (Fig. 5.5) over time. In the old days, the fruit was crushed in the mills (1) and placed into bags (2) or frames (3). Compared with the time when the must was extracted with lever presses (4), today’s hydraulic presses (5) have drastically improved the process. After a time-consuming settling process, the oil was skimmed ( 6 ) and then placed in jars (7) or tanks (8). The oil was separated from the must water by sedimentation and decantation. Another advance in efficiency was made when centrifugal separators (12) were first introduced. Modem plants use automatic preparation of the fruit (13) and must separation via three-phase decanters (14) that separate oil, water and the accompanying solids. Because local processing is still used today, the process is on a much smaller scale than the extraction of oilseeds. There are two
Fig. 5.4. Olive oil production in the course of time (courtesy of Westfalia Separator AC, Oelde).
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351
Olives Washing, removing foreign material (5.2.1) Crushing (5.1.2.2) (5.1.2.3)
1 Must separation
Expelling, centrifugation, percolation (5.1.2.4)
I Oil separation
Centrifugation (5.1.2.4.1)
I'
Olive oil Fig. 5.5. Processing flow chart of olive oil production. principal methods of oil production, i.e., pressing and separation via centrifuges. Depending on the separation method chosen, the fruit must be pretreated. The choice of method itself depends on whether the fruit were picked from the tree, picked up or mechanically harvested. If they are picked naturally, the proportion of leaves, stocks and other foreign matter is much less than with the two other methods. 5.1.2.7 Washing and Removal of Foreign Material. Washing and removal of foreign material are unnecessary processing steps if the oil is press extracted because the presence of leaves or twigs in the pressing process does not negatively influence oil quality and does not harm the press. If centrifuges are used it is extremely important to carry out these steps because foreign material (except the leaves) can easily damage the centrifuges. Leaves are sucked off by automatic machines. The olives are washed with circulating water.
5.7.2.2 Olive Crushing. The objective of this processing step is to break the cell walls in order to release the oil and to form larger droplets, which can more easily be separated. Metal mills require less energy for the drive than stone mills. Their disadvantage lies in trace metals which may be transferred to the oil, reducing its oxidative stability. Oil produced using metal crushers leaves the disintegration section at an -10°C higher temperature. A taste difference between the two oils is noticeable. 5.1.2.2.7 Stone mills. Stone mills consist of a round granite base block -2 m in diameter that carries a metal vessel consisting of a truncated cone that tapers off to the lower end where it is fixed to the granite (Fig. 5.6). In the upper part, two or three granite milling stones run in an upright position at -15 min-1. The milling
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Fats and Oils Handbook
Fig. 5.6. Stone mill to crush olives.
stones have a diameter of -120 cm and a thickness of -40 cm. These milling stones mill down the olives, produce the pulp and break the stones. The advantage of granite milling stones is that almost no metal traces can reach the oil, thus prolonging its keepability. In addition, the pulp is not heated, the mechanical strain is low and there is no emulsion formation. The process is discontinuous. 5.1.2.2.2 Metal crushers. The principle of metal mills is that the olives are thrown against a metal wall where they burst. Usually, they are centrifugally flung away from a rotating disk and crushed at the wall of a conical vessel in which the disk is rotating. From there, they slide into the lower part and are conveyed off. This process can be carried out continuously. Therefore, metallic mills are usually used in oil mills that use continuous separation to extract the oil. 5.1.2.2.3 Hammer crushers. Continuous plants also use hammer crushers in which the fruit are crushed and beaten at the same time. Then 30% warm water is added in a mixer before the pulp is fed with an eccentric screw pump to the decanter for must production. Oils produced with a metallic crusher tend to have a more bitter taste (Martinez Moreno et al. 1957). 5.7.2.3 Mixing. After crushing, the paste has to be mixed to allow the fine oil droplets to coalesce into larger ones. This is done by stirrers that are equipped with blades or that are spiral shaped. The effect is shown in Table 5.1. Olive extraction
Extraction of
Vegetable Oils
353
TABLE 5.1 Olive Oil Droplet Size Distribution (%) Depending on Processing Step9 After Crushing Mixing
4 5
15-30
30-45
45-75
75-1 00
>150
6
49 18
21 18
14 18
4 19
6 25
2
aSource: di Ciovacchino (1989).
yield is proportional to mixing time and mixing temperature. Giovacchino (1996) reported a 10% increase in yield by increasing the temperature from -18 to 32°C and a 7% increase by doubling the mixing time from 30 to 60 min. After first mixing, the pulp can be further disintegrated by using machines that resemble meat mincers; they consist of a rotating knife behind a perforated plate.
5.7.2.4 Oil Extraction. In former times, oil extraction was done exclusively with presses. Today, this process is still very common (-50%). To improve the oil separation, processing aids that attack the cell walls and ease the oil flow may be added (Montedoro and Petruccioli 1974). These processing aids are used only when difficult raw materials have to be processed. The headings of the following sections always relate to the frrst (and essential) step of the total extraction process. A second step with centrifugation always follows to separate oil and must (Fig. 5.9). 5.1.2.4.1 Oil extraction with presses. Pressing is done discontinuously in a frame press, which holds a stack of alternately arranged mats and metal disks fmed in their position by a central spine. The olive pulp is smeared on the filter cloth. Such presses hold up to 500 kg of pulp per cycle. One pressing cycle takes up to 2 h; the pressure applied to the olive pulp is -15-20 MN/m2 (150-200 kg/cm2) in single pressing; for double pressing, it is 10-15 MN/m2 (100-150 kg/cm2) in the first step and up to 45 MN/m* (450 kg/cm2) in the second step. The vertical spine is hollow and perforated, thus allowing the must to drain off. A hydraulic pump drives a piston that puts pressure on the pulp by pressing the stack of frames toward the upper part of the press. If double pressing is applied, the pulp has to pass to subsequent presses; the first press applies only about half of the pressure of the second one. Recently, semiautomatic devices have been put in place that reduce labor cost for charging and discharging frame filter presses. 5.1.2.4.2 Oil extraction with centrifuges. Oil extraction can also be done in one step using decanters. This process was made possible by the development of centrifuges that allow for a ratio G of centrifugal acceleration to acceleration by gravity (see Chapter 7.2.6.1, Equations [7.6a] and [7.6b]).
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Fats and Oils Handbook
Fig. 5.7. Three-phase decanter for olive oil recovery (Source: Westfalia Separator AG, Oelde).
Such machines allow direct oil extraction without prepressing. They manage to separate the solid from the liquid phase in one step and at the same time split the liquid phase into oil and water (Fig. 5.7). The second step of oil extraction, irrespective of prepressing or preseparation with centrifuges, is the clarification of the oil with a separator. In this process, solids are also separated. However, because these are particles that cause only turbidity, they are few in number and no decanter is necessary (Figs. 5.7 and 5.8). If processing is done via centrifuges and if two decanters and two separators that jointly feed one separator are used to polish the oil, capacities of 150 ton of olives per 24 h and per line can be achieved.
Extraction of Vegetable Oils
355
Fig. 5.8. Operational principles and constructional features of separators used in olive oil extraction (courtesy of Westfalia Separator AC, Oelde).
356
Fats and Oils Handbook
TABLE 5.2 Technical Data of Separators for Palm Oil and Olive Oil Clarificationa Polishing centrifuges Maximum throughput Bowl content Solids content (bowl) Bowl speed, max, Energy requ. drive Length Width Height Weight
6,600 7 3 7500 5.5 1265 860 1400 91 5
Separation centrifuges
10,000
12,000
25,000
50,000
150,000
12 6 6500 11 1400 860 1700 1210
12.5 6.5 6500 11 1650 980 1700 1000
26.5 16 5000 25 1500 1300 2200 2375
46 25 4500 45 1950 1400 2100 31 25
125 57 3300 70 2685 2400 2250 6500
Types SA ...006 and SA ...076.Source: Westfalia Separator AC, Oelde.
If centrifugation is used for the separation of the solid phase from the liquid phase, prior dilution becomes necessary. The amount of water added depends on the individual characteristics of the plant but usually lies between 75 and 125% wt/wt of the pulp. To preserve the oil quality, the water added should be tempered (2&25"C). Technical data of centrifuges are given in Table 5.2. Figure 5.10 shows a processing line for continuous olive oil production. This line is in contrast to the more traditional and artisanal approach to olive extraction. The olives (A) are delivered to a receiving hopper and conveyed (2) to the leaf blower (3). There, leaves and twigs are removed while the olives are further cleaned from sand and earth in a downstream washer (4).The clean fruit enter a hammer mill (6) where the entire fruit is ground. The olive paste from (6) is fed to a mixer (7) where the paste is heated to 35°C. Cellular tissues are broken up and the flow behavior of the paste is improved. The pulp is then pumped into a threephase decanter (12) by means of an eccentric screw pump (8). Hot water (up to 30%) is added to ease separation into oil (D), vegetation water (E) and solids (F). The two liquid phases pass through a vibrating screen (11) where light suspended particles are removed. The water (E) is deoiled in a separator (14). Residual water and solids are removed from the oil (D) also using a separator (13), and the clean oil is stored (G). Separated vegetation water may be reused or diluted after having been cleaned. 5 . I .2.4.3 Percolation extraction. The principle of percolation extraction is based on the different adhesion of the systems oiYmetal and watedmetal to the metal. A perforated steel plate is submerged into the must. Because of the different surface tensions, its holes are filled with oil, whereas water is rejected. If a large number of plates are immersed in and drawn off the must, they become coated with oil. Thus the oil is separated from the vegetation water. Such machines carry the name Sinoles system; its principle has been known since 191 1 (Martinez Moreno et al. 1957). Machines that can process up to 350 kg
Extraction of Vegetable Oils
357
pulp per hour have 5120 sheets with a total surface area of -6000 m2. They rotate 7-8 timedmin; they are immersed into the must and the oil is allowed to drip off. The advantage of this process is that it can be automated. However, the amount of unrecovered oil is high. Therefore, this process is most often combined with pressing or centrifugation (Petruccioli 1965; Fig. 5.11). The lower labor rates of this process are offset by the high investment cost so that it is not frequently used.
Fats and Oils Handbook
358
-
Fig. 5.10. Olive oil recovery with decanters and separators (courtesy of Westfalia Separator AG, Oelde).
Olives
Washing and removal of leaves and twigs
usually manyfold (5.1.2.3)
Sheets with 6,000 m' surface area, rotational speed 7-8 rnin.1, 350 kg of pulp I
Must (water content 55-65%)
I
c
c
ccc Water
Centrifugation I
Must
I
Oil Vegetation water
Vegetation water
-+
~
~
-
+
>>> vegetation water
Olive oil
Fig. 5.11. Extraction of olive oil by means of percolation and centrifuges.
Extraction of Vegetable Oils
359
5.7.2.5 Processing the Residues 5.1.2.5.7 Husk (pomace) processing. Smaller oil mills ship the pomace to larger plants for extraction of the residual oil. The husk, which holds up to 55% water, is first dried. After drying in horizontal rotary dryers, the husk consists of the following: water, 6-8%; oil, 5-9%; kernels (seeds), 40-50%; skins, 9-10%; and crude fiber, 20-30%. The dried husk is solvent-extracted to recover the residual oil. The extraction meal can be burned for energy generation or (without kernels) used as an additive to fodder. It may also serve as fertilizer (Fig. 5.12). In many mills, the kernels are separated before oil extraction. The oil content of the husk thereby increases to -18%. If the extraction meal is burned, solvent recovery may be less carefully conducted than when it is used as fodder. 5.1.2.5.2 Vegetation water. In the Mediterranean region, almost 10 MMT of olives is harvested every year. During processing, -4 MMT of vegetation water emerges, creating a major effluent problem. Bernardini (1985) gave details on the composition of the waste water as follows: water, -85% and organic components, -13%, of which oil comprises -0.15% and inorganic components -2%.
5.7.2.5.3Comparison of consumption. Table 5.3 clearly reflects that double pressing allows for the highest oil yield in combination with the lowest amount of
"'"I""
H20 C 15%
Hi0
Anirnalfeed
15%
Revolving furnace
t t t
Residue<<<
t
fuel e Residue<<<
t
t
1
Revolving furnace
G
1
-
'I
l~?
~~-
>>>Seeds>>>
-+
I
Extraction
1 k
I ? ilk >>> Residue >>>
Oil
1
e c fuel c= Residue<<< _A'/
Separation of seeds
pL +
v;
-+ 4-
t
Extraction solvent
---y Residue >>>
Fats and Oils Handbook
360
TABLE 5.3 Yields in Olive Oil Production Using Different Techniquesa Waste water
Pulp
Oil yield Water content Oil content Pressing (D = 40 cm) Double pressing Centrifugation PercoIat ion Percolationkentrifugation
(YO)
(YO)
(%)
85-91 89-94 80-88 35-70 81-90
22-28 20-25 40-55 55-65 38-52
5-7 4-5 3.5-5.5 7-1 3 2.5-5
Amount Oil content (%) (Uton olives) 40-60 40-60 100-150 2-6 100-150
0.2-0.6 0.2-0.6 0.41.0 0 . 4 1 .o 0.3-0.8
aSource: di Ciovacchino (1989).
effluent. However, this cannot be the only parameter influencing the decision concerning which process is used. In addition, energy consumption and labor as well as investment cost have to be considered. Total consumption is given in Table 5.4.
5.2 Oilseed Extraction Unlike raw materials that deliver pulp oils, oilseeds can easily be stored over long periods and transported without major risks. Therefore, they are usually extracted close to the location where the crude oil is further processed. In principle, oilseed extraction consists of four basic steps:
1. Seed cleaning and pretreatment 2. Oil extraction (expelling or solvent extraction) 3. Working up the miscella or expelled oil 4. Working up the extraction meal Figure 5.13 shows these steps in more detail in a flow chart of seed oil extraction principles. The machines and plants shown and described in the following serve only as examples. Others exist from different manufacturers. Technical data given for some of the machines are meant to provide an overview rather than present the TABLE 5.4 Energy Consumption in Olive Oil Production Process step Washing and cleaning Stone milling Metal milling Beating Press extraction Centrifugation
(kWhlton) 3-5 10-20 12-1 4 15-1 8 12-20 60-80
Extraction of Vegetable Oils
I
361
CNda on
w-
-
+
+
Fig. 5.13. Flow chart of seed oil extraction.
latest technological developments. For the most current information, the suppliers should be contacted. Besides the technological aspects, running an oil mill consists mainly of the task of managing the mass flow. On its way through the mill, the volume stream is constantly changing (Fig. 5.14). Large oil mills have to manage mass flows of several million metric tons, i.e., up to 10,OOO MT/d. 5.2. I Seed Pretreatment
All oilseeds have to be prepared for extraction. The individual steps required depend on the kind of seed and on the technology chosen. The steps are schematically given in Figure 5.15. Special treatment for single seeds is given below.
Fats and Oiis Handbook
362
Fig. 5.14. Volume flow through an oil mill (after Weber 1987)
Figure 5.16 shows the common pretreatment steps. The dried seed (A) is conveyed with a screw conveyor, which feeds an iron separator ( 2 ) . Impurities are pneumatically removed and discharged via (C). The seed is then dehulled (4), if necessary, and further conveyed (D). In (6), it is reduced and flaked. From the flaker, it is conveyed to the extraction plant (B).
Seeds from Storage Metal separation (5.2.1.1.1) Sieving, air separation (5.2.1.1.2)
a Primary Breaking
Secondary Breaking
Cutting copra. breaking Seeds (5.2.1.3.1)
Corrugating (5.2.13.2)
I Conditioning
Heating (5.2.1.4)
I Flaking
Flaking (5.2.1.3.3)
+
1 structuring
t
Prepared Seed
I
ExtNSiOn (5.2.1.5) ALCON-Process
Oil Extradion
Fig. 5.1 5. Preparation of oilseeds for extraction.
Extraction of Vegetable Oils
3 63
Fig. 5.1 6. Seed pretreatment.
5.2.7.I Seed Cleaning. Oilseeds bear foreign material introduced during harvesting, transportation or storage. These materials may be seeds of weeds, leaves, twigs, and other plant material. Foreign seeds have no influence on the oil quality, whereas leaves and twigs disturb the subsequent processing. Impurities may also consist of sand, earth, stones, and metal parts from harvesting machines or transports. These damage the plant and therefore must be removed, even if they are inert toward the oil. According to U.S. standards (Official Grades of the U.S. Department of Agriculture), soybeans may contain 1% of foreign material to meet grade 1,2, and 3% to meet grades 2 and 3, respectively, and 5% of impurities to be graded 4. Figure 5.17 reflects the situation in a German oil mill during one year. The figure shows foreign seeds and impurities found in shipments of rapeseed and sunflower seed. The figures fluctuate according to the season, the quality of the seeds purchased and the region of origin. They cannot be seen as representative, but exemplary. Figure 5.18 offers a schematic of the cleaning steps through which the seeds have to pass. 5.2.7.1.1 lron separators. Iron separators separate magnetic metal particles from the seeds to protect the machines employed. A tramp iron separator consists of a drum equipped with an electromagnet. The material is fed onto a vibrating chute that is driven by an electric motor and an eccentric shaft. The drum, which consists of nonmag-
Fats and Oils Handbook
3 64
Average amount of foreign material [%]
4 n Sunflower seed
* Railway, Ship Q
Truck
Rapeseed *Railway,
Ship
+Truck
60.
v
50 40
30
20 10 0
netic hard steel, is fed constantly and driven by a geared motor. Inside the drum, a stationary electromagnet induces a magnetic field. This magnetic field captures magnetic metal particles that are separated from the main stream (Fig. 5.19). Iron separators have a capacity of up to 20 tonh (Table 5.5). The machines described in the table have a rotary speed of 1400revolutions/min and the drum diameter is always 300 111111. 5.2.1.1.2 Separation of nonmetallic impurities. Principally, there are two ways to separate nonmetallic impurities. The first is sieving, with the prerequisites of an even-sized seed and a clear size difference compared with the foreign material. The
3 65
Extraction of Vegetable Oils
seeds from storage, or transport
Sbve, collr80
(5.2.1.1.2.1)
(5.2.1 .I.2.1) 3
t
--t
4-
Iron separation
rnagnetkally (5.2.1.1.1)
Blowing or suction (5.2.1 .I .2.2)
Fig. 5.18. Removal of foreign Clean Seed
3
Dehulling or Bnaking
material from oilseeds.
non
Fig. 5.19. Iron separator (courtesy of Krupp MaschinentechnikCmbH, Hamburg).
Fats and Oils Handbook
366
TABLE 5.5 Technical Data
of Tramp Iron Separator+ Capacity (m3/h)
Length Width Width of vibrating chute Length of vibrating chute Magnetic drum length Diameter Drive power Speed Weight
(mm) (mm) (mm) (mm) (rnm) (rnm) (kw) (rnin-1) (kg)
3-5
4-7
6-10
a12
1995 825 300 350 350 300 0.55 1500 400
1995 1025 500 550 550 300 0.55 1500 450
1995 1170 650 700 700 300 0.75 1500 500
1995 1325 800
850 850 300 0.75 1500 550
10-15 2100 1525 1000 1050 1050 300 1.10 1500 650
-
Type MT, courtesy of Krupp MaschinentechnikCmbH.
second is wind sifting (air separation), which requires that the seed and the impurities to be removed have a different specific density. Sieving is done mainly with the use of vibrating screens that are perforated with holes larger than the seed being processed. Thus leaves, twigs and other larger impurities are held back and can be removed. Thereafter, the material passes through a sieve with holes smaller than the seed, which separates sand and other fine foreign material. If trough conveyors (see Chapter 4.1.6) with a sieve-like perforated trough are used, these impurities can automatically be removed during internal transport. Air separation consists of a large fan that blows or sucks off lighter foreign material. Parameters to be considered are the density of the sifting gas (in this case, air) and the material to be slfted. Furthermore, the resistance coefficient of the particles, their resistance area, the speed of the gas and the material and the particle diameter are of importance. Usually, the impurities to be removed are so different from the seeds in terms of density and flow resistance that their separation does not create any difficulties. Figure 5.17 also shows some graphs that indicate what material is sucked off as a function of the suction power. It can be seen that the suction power has to be well controlled; otherwise, too much of the seed is sucked off along with the impurities. To retain as much of the seed as possible, wind screening is therefore often done in two steps. In the first, the impurities are completely removed with a relatively high amount of seed carried along. In the second, the seed is recovered with as low an amount of impurities as possible. 5.2.1.2 Dehulling (Decorticating). To extract the oil of nuts such as palm nuts, coconuts and babassu nuts, the nuts have to be dehulled, i.e., they have to be cracked. For babassu and African palm nuts, this is still done by hand to a great extent. Most oilseeds that could be extracted after size reduction are also dehulled. Extraction without dehulling would be possible; however, the hulls usually do not contain fat and therefore reduce the capacity of the plant. Also, they may contain components that would have to be removed from the oil afterwards or reduce its
Extraction of Vegetable Oils
367
TABLE 5.6 Average Hull Contents of Oilseeds Oilseed
(%)
Soybeans Cottonseed Sunflower seed Peanuts Rapeseed Sesame seed Copra Palm nuts Safflower seed Babassu nuts
7 31 30 47 15 8 1
55 48 68
quality. The economic soundness of dehulling depends on the share of the hull in the total seed weight (Table 5.6). Soybeans, for example, have a very thin hull that does not greatly hamper extraction. Therefore, dehulling used to be uncommon. Today, however, soy beans are very often dehulled because this step is essential if high protein (HP) meal is required. Rape is not dehulled at all, but there are some findings (Schneider 1979, Schneider and Rass 1997, Signoret 1988) that may make it more common in the future. Cottonseed is always delinted and dehulled; the same holds true, naturally, for peanuts. Sunflower seed is also usually dehulled. There are different methods for dehulling, including hammer mills for nuts, rollers, disk attrition mills and many others. In disk attrition mills, the seed is fed via a funnel. It falls onto two vertical corrugated disks. Depending on the seed, the corrugation may be fine or coarse. Disks that are toothed or equipped with usually rectangular and blunt-edged bars also exist (see Fig. 5.20) for purposes such as
Fig. 5.20. Dehulling machine (courtesy of SKET, Magdeburg).
Fats and Oils Handbook
368
peanut dehulling. Depending on the construction principles, both disks rotate in a parallel direction (with a differential speed of --1:1.25; -lo00 seedmin) or one of the disks is static. The opening between the disks can be adjusted. The seed is fed into the center of the disks. From there, the particles are centrifuged to the outside from where they drop and are collected. Table 5.7 gives an indication of sizes and consumption. Rollers follow a different principle; however, they may be similarly constructed. One possibility is a pair of horizontal corrugated rolls that rotate with similar differential speed as described above for the disks. A second possibility is a roll that rotates inside a cylinder; a third is a pair of rolls that is cavitated instead of toothed. The capacities depend on the machine size but also differ from seed to seed. Another technique is dehulling by pneumatic impact. There the seeds are blown against a wall and crack.
5.2. I .2. I Hull separation. Hulls can be removed by screening, air separation and electroseparation. Screening is done via vibrating sieves. Air separation follows the same principle as described for the removal of impurities. Electroseparation is an interesting principle applied, for example, to sunflower hulls. The hullkernel mixture is fed with a vibration feeder to a roll from which it passes close to a corona electrode, which is a fine piece of electrical wire. Because of the different influence of the electrical field on hulls and kernels, the former are more deflected than the latter, thus falling into different boxes. Electroseparators (Fig. 5.21) with a capacity of 2 M T h have a connected load of -3 kW.Their outer dimensions are 2300 x 1750 x 1200 mm.
5.2.7.2.2Dehulling of the individual seeds and nuts. The dehulling process must be adapted to the individual seed or nut. It may differ considerably and may also influence the use of the meal. 5.2.1.2.3 Dehulling of soybeans. Soybeans have to be dehulled if high protein (HP) meal is required. Dehulling performed before extraction is called “head end.” TABLE 5.7 Technical Data of Dehulling Machinesa Peanuts output
MTh
2.1
Length Width Height Disk diameter Drive Weight
(mm) (mm) (mm)
1725 830 930 560 4 730
T y p e AS; SKET.
(mmj
(kWh)
(kgj
2.5 1900 1010 1140 710 7.5 1170
Cottonseed
2.9
900 11
1.7 1725 830 930 5 60 7.5 730
2.3 1900 1010 1140 710 11 650
3.3
900 19.5
Extraction of Vegetable Oils
3 69
Fig. 5.21.
Drawing of electric separation and electric separator (photo: courtesy of SKET, Magdeburg).
If the hulls are separated from the extraction meal, it is called “tail end.” For headend dehulling, the beans are broken and the hull, which is not fixed very tightly to the kernel, is loosened. The hulls are then separated by wind sifting. Beans that are not dehulled are separated from the main stream of broken beans by sieving. Residual hulls are removed from the broken beans in a second round. The hulls are then once more air separated to recover parts of beans that had been blown off with the hulls. The hulls are burned or blended with the meal to standardize it. Good head-end dehulling yields a hull content of dehulled seed el%(see Fig. 5.22). 5.2.1.2.4 Delinting and decorticating of cottonseed (Fig. 5.23). Cottonseed is a very special case because it has to be delinted before dehulling. Lint is made up of the residual woolly fibers that stick to the seed. To remove them, the seed passes rotating disks equipped with sawteeth. The lint is then brushed or blown off from the teeth of these disks. The lint (9697%) is removed in this process; the remain-
Fats and Oils Handbook
3 70 Nondehulledwhole beans
r+l
Dehulling
and Breaking
I
>>> Hulls (with m a l l amount of beans)
I ,
I Sieving
nondehulled
Hulls
broken beans (and hulls)
3
Fuel Additive to meal
Dehulled, broken beans
Fig. 5.22. Dehulling of soybeans.
der has the important function of holding together the hulls that would otherwise easily break into tiny particles during dehulling. Air classification is thus facilitated. The residual 3 4 % of lint is then removed together with the hulls. The separated lint passes a cleaning step to remove filth and bran; then it is pressed into bales. Chemical delinting is an alternative. Diluted acid is sprayed on the cottonseed, which is then dried. The acid is thereby concentrated and loosens the lint from the hull. The disadvantage of this process is that further use of the lint is limited. White seed
I
Black seed a d ISconcentrated and separates linters from seed >>> Linters
3
waste. FUOI
F
ccc Linters
Seed
I
seeds cutto half
pneumatlcslty, to &15% hull content -~
+
>>> Hulls ~
=
Filling nutonal for piastIcd
3
PlOdudlOn of xylore. furfurel, tannin
Delinted dehulled seed
Fig. 5.23. Delinting and dehulling of cottonseed.
Extraction of Vegetable Oils
371
In addition to the lint, dust and any other fine foreign material are removed before dehulling. The capacity and the efficiency of dehulling machines strongly depend on the proportion of lint. If it exceeds the commonly achieved 3 4 % and rises to -lo%, the capacity of dehulling is halved. In the early 1980s, the maximum daily output was -75 MT. Since then, new machines that allow the dehulling of 250 MT of delinted seed daily have been used (Lester 1987).
5.2.7.2.5 Dehulling of sunflower seed. Sunflower seed should be dehulled because the hulls make up 30% of the seed weight. Dehulling is also important because the seed holds a lot of waxes that would be transferred to the oil during extraction. The wax content of oil from nondehulled seed is approximately five times higher than from dehulled seed. However, a small proportion of hulls (<15%) remains in the seed to ease percolation during solvent extraction; otherwise, the kernels would bake together. The extraction meal of dehulled sunflower seed may be sold as HP meal. Beal (1987) gave an overview of the advantages of sunflower seed dehulling. 5.2.1.2.6 Dehulling of peanuts. Peanuts can be dehulled easily because they are freely contained in the hull. The hulls, which make up 50% of the weight, are easily air separated because their density difference to the kernels is very high. The hulls are burned or used as fillers for construction material or fiber boards.
5.2.7.2.7 Dehulling of rapeseed. To date, rapeseed is only rarely dehulled. Some investigations have been performed concerning the benefits of dehulling rapeseed, including those by Schneider (1979) and Signoret (1988). Schneider also showed detailed photographs, illustrating the dehulling process, and explained the mechanism (Fig. 5.24). There are two major routes that have been followed for dehulling. One is pneumatic impact, i.e., blowing the seed against a wall to crack it. The other is defined deformation. Rapeseed hulls make up 12-18% of the seed. The hulls contain 12-15% lipids, which are more difficult to extract than the lipids from the kernel. This means that dehulling slightly reduces the overall oil yield. On the other hand, partially dehulled rapeseed (hull content 7%) increases the oil content of the rape kernels prepared for extraction to -50%, thus improving utilization of the capacity of the oil mill. Environmental considerations comprise a second reason that may make dehulling of rape more attractive in the future. Wolff (1983) proved that, during desolventizing, extraction meals from rape hull fragments, the whole rapeseed, and rapeseed kernels behave very differently. Desolventizing at 105°C for 100, 60 and 30 min is required to reach a residual hexane level of 2000 ppm. Conversely, after 90 min of desolventizing, they contain -2500, 1500, or 500 ppm, respectively, of residual solvent. This makes dehulling a very attractive option. In addition, the meal produced from dehulled rapeseed has 50% less cellulose, i.e., it has better digestibility and a higher nutritional value.
-
3 72
Fats and Oils Handbook
Fig. 5.24. Principal of rapeseed dehulling by deformation (after Schneider and Rap 1997; adapted from FetVLipid with permission).
The trends toward pressing that have emerged in some countries may not play any role unless white rape can be bred. Rape hulls contain a very dark-colored component that is partly extracted with the oil. Oil from dehulled seed is much lighter in color and requires only a reduced bleaching effort. 5.2.1.2.8 Cracking of coconuts. Coconuts are hand-cracked in the country of origin; the pulp is separated and dried to produce copra. 5.2.1.2.9 Cracking of palm nuts. Palm nuts are usually cracked in hammer mills, They fall on quickly rotating massive paddles where they crack or fall on quickly rotating disks. From there, they are centrifuged to the outer wall of the milling vessel where they are cracked. The separation of the kernels from the shells can be done in two ways. One method is to use the shape of the kernels and the shells. Both are fed to a conveyor belt that runs at a steep angle. The kernels roll down because of their regular round shape; the shells remain on the belt because of their irregular toothed shape. Thus the shells are removed by the belt. The second method is the separation by salt water. The difference in density, which is insufficient for wind screening, is then used. The shells swim on the water, whereas the kernels sink. They then have to be redried.
Extraction of Vegetable Oils
3 73
5.2.7.2.7 0 Dehulling of safflowerseed. It is quite difficult to dehull safflower seed because the hulls are thick and hard, but the kernels are soft. Separation is done via a rotor and corrugated disks. 5.2.7.2.7 1 Cracking of babassu nuts. Babassu kernels are still mainly cracked manually. Machines built for that process have never worked to the user's satisfaction. The shells are burned or used for furfuralproduction. 5.2.1.2.12 Dehulling of jojoba. Jojoba dehulling is relativdy difficult because the machines easily became stuck as a result of the jojoba waxas. Therefore, an attempt was made to dehull it in a deep-frozen state, The results obtained were very satisfactory, but the process was too expensive. 5.2.7.3 Reduction and Structuring of Oilseeds. All oilseeds have to be reduced to obtain good extraction results. Most of the seeds are small enough so that only fine grinding is necessary. This is different for palm nuts, which require an initial coarse reduction. Special equipment is needed for copra, which is shipped in pieces of up to 10 cm; a special cutting step has to be taken. The number of reduction steps required for individual seeds is listed in Table 5.8. In the folhwing, plants for oilseed reduction are described. 5.2.1.3.1 Coarse reduction. Copra is delivered frm the mncries of origin in irregular large pieces. These pieces have to be broken down to t)re dze of oilseeds t l m ,copra has to before they can enter the normal oil extraction procwi, T pass so-called copra cutters before it enters corrugaM milis, The cutter consists of claw-shaped knives that cut the copra while slawly mtatiln$ toward stationary TABLE 5.8 Reduction of oilseeds Number of treatments Cutting Soybeans shredding Sunflower seed Rapeseed Cottonseed decorticated Peanuts kernels Corn germs Palm kernels Babassu kernels Coma
Breaking 2
2 0-1 2 1 2 2-3 2-4 2-3
RolIing 1 1 1 1
1 1
1 1 3-4 2-3 1
Fats and Oils Handbook
3 74
Fig. 5.25.
Copra cutter with removed knife guard (type MR; courtesy of Krupp Maschinentechnik GmbH, Hamburg).
grates. The knives are arranged side by side on a horizontal square shaft. Figure 5.25 displays a copra cutter, and Table 5.9 summarizes its technical data. 5.2.1.3.2 Fine reduction and flaking. Reduction, fine reduction and flaking are done with fluted breaker rolling mills and flaking mills. Table 5.8 shows which oilseeds have to pass the breaking steps and how often the process steps must be performed. To reduce the size of oilseeds in a fluted breaker rolling mill (Fig. 5.26; technical data, Table 5.10), the material is fed in a steady flow to the rolls. There it is crushed, ground or shredded for further processing. To ensure even distribution TABLE 5.9 Technical Data of Copra Cuttersa Capacity (MT/h)
2.5 Length, overall Width, overall Height Knife shaft diameter Length Gear motor Speed Number Service weight
(rnrni (mm) (mm) (rnm) (rnm) (kw) (min-1) (ka)
Type MR, courtesy of Krupp Maschinentechnik GmbH
1985 440 655 250 700 5.5 150 1 880
3.1
5.0
2125 440 655 250 800 7.5 150 1 1050
2500 640 880 350 1000 17 100 1 1650
10.0 3750 780 785 350 1000 11 100 2 2300
Extraction of Vegetable Oils
375
Fig. 5.26. Fluted breaker rolling mill (type R300; courtesy of Krupp Maschinentechnik GmbH, Hamburg).
and a constant feed to the rolls, the seed has to pass a variable-speed vibrating feeder located in the inlet hopper. The pair of rolls rotates at different speeds in opposite directions. Together with the corrugated surface, this ensures that the material is neither rubbed nor squeezed but cut in order to have the best possible disintegration of the oil-bearing cells. The design of such pairs of rolls is modular so that they can easily be stacked. The clearance between the rolls can be adjusted by hand to fit the material fed. TABLE 5.10 Technical Data of Fluted Breaker Rolling Mil& Maximum throughput Length Width Height Roll diameter Length Drive motors, power Power, total Number Speed Weight, net
Peanut kernels
(MTh)
8.3
13.0
(mm) (mm) (mm) (mrn) (mm)
2190 1120 1220 300 800 1500 11 1 1500 2350
2695 1120 1220 300 1250 1500 18.5 3 1500 3000
(kw) (min-1) (kg)
Type R300, courtesy of Krupp MaschinentechnikCrnbH.
Soybeans 12.5 2190 1120 1890 300 800 1500 11 1 1500 0
Palm kernels
20.0
6.7
10.0
2695 1120 1890 300 1250 1500 18.5 3 1500 5600
2190 1120 2560 300 800 1500 11 1 1500 6250
2695 1120 2560 300 1250 1500 18.5 3
1500 8150
3 76
Fats and Oils Handbook
For flaking, the seed particles pass a pair of rolls that rotate at identical speeds. Therefore, compared with the mills described above, the shear stress is lower. The seed particles are usually flaked to a thickness of 0.20-0.35 mm. Table 5.21 shows the common figures. Although many theories exist concerning optimum thickness, it is based mainly on empirical experience. Most of the formulas given are somewhat contradictory because it is difficult to compare or to keep the processing conditions constant. In addition, one must keep in mind that oilseeds are a natural raw material in which individual batches can differ substantially. As the best known relation in use, Lajara (1990) quoted the findings of Othmer and Agarwal(l955) as follows: -dC/dt = 0.173 . F 3.97 . C 3 . 5 where dCldt is the rate of extraction, F is the flake thickness and C is the residual oil. The equation shows that to increase (theoretically) the extraction rate 100 times (C kept constant), the flake thickness has to be reduced to 32%; to reduce the residual oil content from 2 to 1%, it has to be reduced to 55% (extraction rate kept constant). Flaking mills (Fig. 5.27) can be used for flaking or intensive grinding of finely sized or precrushed oilseeds. They are used to flake precrushed soybeans or finegrained seeds, such as rapeseed, linseed or decorticated sunflower seed. A variable-speed vibrating feeder ensures uniform supply of material. If no material is fed, an automatic control prevents the two rolls from coming into direct contact. The machine houses two rolls, one of which is fixed. The second roll is movable on
Fig. 5.27. Flaking mill without roll cover (type Q800; courtesy of Krupp Maschinentechnik CmbH, Hamburg).
Extraction of Vegetable Oils
377
TABLE 5.1 1 Technical Data of Flaking Mill9
Output (MT soybeansfh) (mm) (mm) (mm) (mrn) (mm)
Length Width Height Roll diameter Length Drive Weight, net
(kw) (kg)
4-6
5-8
6-1 0
11-15
2210 1400 1639 600 1250 55 8750
2410 1400 1639 600 1250 75 10,000
2660 1400 1639 600 1250 90 1 1,400
2760 2100 2 600 800 1250 75 20,900
Type Q600 and 4800, courtesy of Krupp Maschinentechnik GrnbH.
slide bearings. Both rolls are driven through V-belts by separate electric motors. In the type described, the contact pressure of the rolls is generated by an electrohydraulic power unit and transmitted by means of hydraulic presses to both journals. The pressure can be as high as 90 bar. Technical data of some flaking mills are given in Table 5.11. The mill shown in Figure 5.27 runs at 1500 min-1; the; rolls have a diameter of 800 mm. The throughput is -10-15 MT/h for precmshed soybeans. For sunflower, it is 7040% of these values, and for rapeseed, up to 115%. 5.2.1.3.3.3 Extrusion (expanders). To assure good percolation, the reduced seed
sometimes has to be structured. The two main methods developed to achieve this are extrusion (expanders) and the ALCON process. Both processes include a heat treatment step. Extrusion is applied in the US.mainly to soybeans and cottonseed. The extruder (also called expander, Fig. 5.28) is fed by a screw. It consists of a horizontal cylinder Dry feed
4
Staam (into product)
Water (into product)
1
E f for mixing
proceulng conornono and adapWon to d1-t product#
Fig. 5.28. Drawing of an interrupted-flight expander.
Fats and Oils Handbook
378
housing a screw that conveys the material. This cylinder can be heated and has openings to bring in water or steam. The goal of extrusion is to denature the seed protein, if not already achieved in earlier processing steps. Thus the structure of the seed is broken up to ease oil extraction. Extrusion is done after conditioning and flaking. In the first part of the extruder, the seed is brought to a water content of 10-15% and is heated to 105-120°C while passing the machine. The pressure applied to the product by the screw pressing it to the reduced outlet opening leads to a further temperature increase. To bring the temperature to the desired level, additional steam may be injected. It is also possible to modify the outlet width to control the pressure. The line of extruded product leaving the extruder is cut into small pieces. Small clouds of condensing steam appear as the product leaves the extruder and is released to ambient pressure. After cooling to 60"C, extraction can take place. Lusas and Wathius (1988) found that extrusion is also suitable for inactivating aflatoxins in peanut meal. 5.2.1.3.4 The ALCON process. The Alcon process (Fig. 5.29) is based on a patent held by Akzo-Nobel. Its main feature is a special heat treatment of soybeans between the flaking and extraction steps. In an apparatus that resembles a stack cooker, steam is injected in a f i s t step. This stage is intended to raise the water content to 15-20%. Simultaneously, the flakes are heated to 95-1 10°C. While this temperature is maintained for about 15 min, the wetted flakes agglomerate under stimng. In a third stage, the agglomerates are dried and cooled to extraction temperature (Fig. 5.28). Penk (1980) listed the following advantages: -50% higher bulk density compared with conventional flakes; 2.5 times higher percolation rate; reduction of hexane retention in the meal by 15-30%; and increased proportion of hydratable lecithin, leading to 100% higher lecithin yield. The increase of hydratable phosphatides facilitates degumming, making levels of 10 ppm phosphorous more easily achieved. In addition, the refining cost can be reduced. The disadvantage of the process lies in its lower meal yield. However, this only deviates slightly from that of the traditional method.
Flaked Seed to 15-20% Water Content
I
I 95-1 10°C
I 95-1 lO'C, Stirring, 15 min
I
I 60% (Extradin Temperature)
I
Agglomerates
to Extraction
Fig. 5.29. The ALCON process.
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379
5.2.7.4 Heat Treatment. Seed heat treatment (conditioning) is important to achieve high oil yields. There are technological aspects that influence the extraction process, such as the following: protein coagulation, which breaks the intercellular emulsion cracking of cell membranes, which increases oil extractability decrease in viscosity, which makes the oil more fluid Effects that bear on the product quality include the following: sterilization; enzyme inactivation (better digestibility of the meal, less oil hydrolysis); and decomposition of trace components, which negatively influences digestion, thus hampering the use of the meal as fodder. Conditioning is always coupled with the adjustment of a certain water content. The desired effect is to give the seed the right elasticity and to avoid causing the flakes to crumble finely at low humidity. Two main construction principles are common for conditioners, namely, stack cookers (vertical) and drum conditioners (horizontal). Drum conditioners deliver a more constant quality because the controlled flow of the seed ensures more uniform heating and residence time. For direct expelling, no conditioning is necessary. 5.2.7.4.7 Stack cookers. Usually stack cookers form a unit with the screw press (Fig. 5.30). They consist of a vertical cylindrical vessel that houses several trays. Through an inlet, the seed is fed to the upper tray, which is equipped with heating coils on the bottom. Each tray has an outlet that leads to the next lower one. All trays are equipped with a central, sickle-shaped paddle stirrer that sweeps the tray. The stirrer distributes the seed over the tray, ensuring the correct residence time before the valves to the next tray open and the seed is dropped. In this way, the seed is first warmed up and then the desired humidity is adjusted with injected steam. In the processes described in the following sections, the seed is kept warm or postheated and dried again if necessary. For the subsequent extraction, the seed has to be cooled to avoid evaporation of the extraction solvent. 5.2.7.4.2Drum conditioners. Drum conditioners consist of a sequence of horizontal drums. These drums are each double-walled and insulated against heat loss and can thus be heated with steam up to 10 bar. The seed is fed to the topmost heating drum by means of a screw conveyor. It passes through the heating drums conveyed by a special agitator (Fig. 5.31, lower left) that must ensure good lateral mixing. The material is uniformly treated to guarantee optimum heat transfer and even retention time. Vertical dosing screws force the seed material into the next drum and serve as a discharge in the last drum. The first drum also offers the opportunity to spray in water. At least two drums, i.e., the first and the last, are equipped for direct steam injection. Each drum is connected to the central vapor chimney. The number of drums required depends on the kind of seed and on the capacity. Figure 5.31 shows a drum conditioner with three drums; the technical data are given in Table 5.12.
380
Fats and Oils Handbook
Fig. 5.30. Stack cooker screw press combination. 5.2.2 Oil Extraction by Expelling
In most oil mills oil extraction is done with screw presses, as pre-extraction before solvent extraction or as direct press extraction. Until the end of World War 11, press extraction was the commonly used technique and solvent extraction was done only rarely. Then, pressing lost attention and was applied only as a prepressing step before solvent extraction or was completely replaced by direct solvent extraction. Up to the early 1990s, direct press extraction was done only rarely because it did not yield residual oil contents significantly 4 % . Today, however, under the pressure of environmentalists, it seems to be experiencing a renaissance. In Scandinavia in the early 1990s, for example, a strong demand originated for directly pressed oil. If expelling is done as a first step before solvent extraction, a residual oil content of 15-20% is targeted. Open presses are common today only in olive oil extraction. For oilseed expelling, closed screw presses are used almost exclusively. Figure 5.32 gives a schematic view of the extraction process and Figure 5.33 offers a pictorial view. The screw press (2) is fed from a cooker (1). The extracted oil passes through an oil foots separator (3) and a polishing filter (6) before it enters the storage tank (G). The turbid solids from (3) are fed back to the press where they are reprocessed.
Extraction of Vegetable Oils
381
Fig. 5.31. Horizontal cooker (type TK; courtesy of Krupp Maschinentechnik GmbH, Hamburg).
The cake (16) is broken (14) and then either conveyed to the solvent extraction plant or bagged or stored in bulk. 5.2.2.7 Parameters Influencing Press Extraction 5.2.2.7.7 Water content. Seed conditioning usually aims at a water content of 3-6% for expelling. The residual oil content of the meal is independent of the water content. Krupp trials (Fehrenfeld 1977) showed that the optimum seed humidity lies between 2 and 4% if screw presses are used (Fig. 5.34, upper left). It is striking that the residual oil content steeply increases at a water concentration <2.5%. Most likely, the seed loses too much of its elasticity.
Fats and Oils Handbook
382
TABLE 5.1 2 Technical Data of Drum Conditionersa Typical approximate throughput (MT/h)
4
6
10
10
Length (mm) 51 20 51 20 5120 Width (mm) 1900 1900 1900 Height (mm) 2930 41 80 6690 Heating drum Diameter (mm) 900 900 900 Length (mm) 3600 3600 3600 Number 2 3 5 Heating surface (m*) 20 30 50 Power consumption Cylinder drives (kw) 15 22.5 41 Dosing screw (kW) 1.5 1.5 1.5 Weight, net (kg) 8000 1 1,500 19,500 (Dried to 3% water, At 80"K, 11 bar); speed of drive motors: 1500/min-l.
14
8280 1900 4885
10,390 2000 4885
1250 5400 2 59
1250 7500 2 82
44 2.2 19,500
60 2.2 25,000
aType TK, courtesy of Krupp Maschinentechnik GmbH.
5.2.2.1.2 Capacity of the press and power applied. Figure 5.34 (upper right) shows the influence of the press capacity on the residual oil content. These results stem from Krupp trials (press type Krupp SVP,copra, 49 min-1). Again, this graph also shows the influence of humidity. As could be expected, the amount of oil left in the meal also depends on the press energy (Fig. 5.34, lower left).
Prepared Oil Seeds Crushing
(5.2.1.3)
Cake (1520% 0.1 content)
I Breaking
I
I
1
1-1
Breaking
I
Meal
(5.2.1.3.1)
I
Crude Oil
Fig. 5.32. Processing flow chart of press extraction.
Extraction of Vegetable Oils
Fig. 5.33.
3133
Press extraction of oil. Source: DGF.
5.2.2.2 Screw Presses. Screw presses can be operated continuously. A screw' press consists of a horizontal strainer cage that houses the screw. The strainer cage should be built divided in halves, hinged onto the press housing, thus enabling opening after loosening interlocking bolts and easy access for maintenance and repair. Usually the diameter of the cage is constant from the beginning to the end. whereas the worm shaft diameter rises in this direction. This is necessary to maintain the pressure as compensation for the volume reduction caused by the loss of' the extracted oil. In this way, the available cage volume decreases. The slope of the worm increases in order to increase pressure. Conical throttle rings ensure that pressure is built up. After passing these rings, the meal is expanded and mixed to be compressed again in a later step. The worm geometry of mode m presses allows operation without the use of a force-feeding device. Usually the presses are built in such a way that segments of the worm can be freely arranged along the shaft. This gives the freedom to adjust standard design presses to individual needs. Although presses exist without a throttle and with seven segments, those with throttles need only three. Figure 5.35 gives the pressure in a screw press with and without throttles. The joints between the individual worm elements are sensitive toward pressure. When throttles are used, they are therefore arranged parallel to the part just behind the throttle where the pressure is lower. The press cage has a special profile that allows for maximum oil drainage. The oil flows out between the cage lining bars and is collected at the bottom of the press, from where it flows out. The diameter of the meal outlet, the arrangement of the throttles and the screw design determine the pressure inside the press. Pressures of up to 3000 bar can be reached, causing temperatures up to 170°C. Under normal circumstances, for pre-
Fats and Oils Handbook
3 84 Residual oil content [%I
Residual oil content ("h] [%] 20
7 II L"
25
18-
1616
A
Rapeseed 17.0MTIh * Copra 19.0 MT/h
I
01,'" 0
Rapeseed 7.2MT/h
1
14-
1
'
2 3 4 5 6 7 Moisture [% wt/wt water]
8
12 135
155
Seed moisture
[%I
175
215
195
235
Mass flow [MT/d]
Power applied [kW]
15 lo l2l4 l6
- - - - ' 52
2o 22 24
Residual oil content [%]
Fig. 5.34. Residual oil content depending on the seed humidity (upper left, after Fehrenfeld 1977), the throughput (upper right, after Homann 1978) and on the power applied (lower left, after Homann eta/. 1978).
pressing, presses reach for 3 0 4 0 bar in combination with a temperature of -95°C; for full pressing, the goal is to reach 400 bar in combination with 115-125OC. It can therefore not be termed cold-pressed oil. Only if much lower yields are accepted can temperatures <60°C be achieved. Figure 5.36 shows a screw press and Table 5.13 gives the technical data. If special presses are used (e.g., former V-Pex presses of Krupp), direct pressing after seed cleaning becomes possible without any further seed pretreatment. That means that breaking, flaking and conditioning may be omitted. These machines use throttles, thus imitating to a certain extent the extrusion (expanding) process. The power needed for the drive is approximately twice as high in this case as in conventional presses. The benefits are a 2% lower residual oil content and the energy saved by omitting the pretreatment steps.
Extraction of Vegetable Oils
385
without throttles Cage length
r
Fig. 5.35. Pressure over the cage length of a screw press (after Homann e t a / . 1978).
Such presses are -60% longer, 70% heavier and also more expensive. The total investment costs, however, are less because the cost of machines for pretreatment is saved. The manufacturers claim a 25% lower energy consumption for the total process. 5.2.2.3 Treatment of the Extracted Oil. The press oil leaving the press must be coarsely purified. To do so, oil foots separators are used. Figure 5.37 shows two types; their technical data are given in Table 5.14. These machines can be used for coarse screening of the foots of the crude press oil. Additional filtering is needed in any case; however, the filtering unit is somewhat relieved. The unit shown in the upper part of Figure 5.37 consists of a screen that is spring-mounted above an oil collecting pan. It is set into vibration according to a circular oscillating principle. The spring steel wire screening has a mesh size of 0.4-0.6 mm. Type SK consists of a welded sheet steel tank in which a drag chain fitted with scraper plates rotates. Foots, which are heavier than the oil, settle on the tank bottom and are transported by the perforated scraper plates to a special slotted screen inside the tank at a level above the oil level. Oil carried along with the foots can drop from the screen. The foots themselves are discharged by a conveyor screw. As full pressing becomes increasingly attractive in some regions, further purification of the press oil may be needed after screening. One possibility is to use a decanter (Fig. 5.38). The oil coming from the press is coarsely clarified (2). Hot water at -95OC is added (F) to ease the separation of the remaining solid particles. The pump (3) conveys the mixture to a plate heat exchanger (4)where it is steamheated to 95°C. After some time in a holding tank to swell the undesired particles, the mixture is fed to a decanter (6). The separated solids are removed with a maximum of 0.5% solids remaining. The oil is dried in a vacuum drier (9) and then stored.
386
Fats and Oils Handbook
Fig. 5.36. Screw press for edible oil extraction (courtesy of Krupp Maschinentechnik GmbH, Hamburg).
5.2.2.4 Treatment of the Cake. The cake has to be broken for further utilization of the meal either for solvent extraction or to process the meal as such. This is done with cake breakers that are integrated into the press or with an external cake breaker such as the one shown in Figure 5.39. In particular, cake that has to
Extraction of Vegetable Oils
387
TABLE 5.1 3 Technical Data of Screw Pressesa Prepress EP-07
EP-09
EP-08
EP-16
5.5-7.5 18-22 4550 1360 1850 1 10-1 60 1 1,000
8.5-1 0.5 18-22 4550 1360 1850 160-250 12,000
1 .O-1.5 5-8 4550 1360 1850 75-1 10 10,000
2.5-3.0 5-3 5900 1460 1850 160-200 15,000
Type Capacity Residual oil in cake Length without motor Width Height Drive Weight
(MTh) (O/d
(mrn) (rnm) (mrn) (kw) (kg)
Full press
Type EP, courtesy of Krupp Maschinentechnik.
Fig. 5.37. Oil foots separators type V and SK (courtesy of Krupp Maschinentechnik GmbH, Hamburg). TABLE 5.14 Technical Data of Oil Foots Separatora
Capacity (MT press oilh) Length Width Height Screen, length width surface Weight, net Drive motor(s), power S P d
1730 1240 880 1250 400
-
450 3 3000
Type V and SK, courtesy of Krupp MaschinentechnikCrnbH.
2365 1370 1260 1800 600
-
900 3 3000
3730 1520 1335 3000 700 1200 4 1500
4000 1600 2000
-
4000 2100 2000 -
1.7 2600 2.6
3.1 3500 2.6
-
-
-
388
Fats and Oils Handbook
Press extraction and clarification of press oil with decanters; schematic and plant (courtesy of Westfalia Separator AG, Oelde).
Fig. 5.38.
undergo further solvent extraCtion has to be granulated. A cake breaker consists of a pair of toothed rolls through which the cake is fed by means of a vibrating feeder. There the press-extracted material is precrushed. One of the rolls is directly driven; the other uses gear wheels. In a second step, the material is further broken down by a pair of fluted rolls arranged below the toothed rolls. The fluting depends on the type of material crushed and the fineness required (technical data,Table 5.15).
389
Extraction of Vegetable Oils
Fig. 5.39.
Cake breaker (Type SZR 300; courtesy of Krupp Maschinentechnik GmbH,
Hamburg).
5.2.3 Solvent Extraction Extraction is always applied when a residual oil content <2% is desired. For oilseeds with high oil content, press extraction is advantageous because it is commercially more sound. If the oil content in the seed is low, the 2-3% residual oil may account for > l o % of the total oil content. This makes solvent extraction more favorable because a residual oil content <1% can be achieved. Solvent extraction can also be directly applied, but is mainly combined with a prepressing step. In the prepressing step, the oil content is reduced to 15-20%. Thus the economic advantages of both processes, press and solvent extraction, are comTABLE 5.1 5 Technical Data of Cake Breakersa Capacity ( M T h )
6-7 Length Width Height Gear motor for toothed rolls Power Fluted rolls drive motor Power Speed Weight, net
8-9
10-11
(rnm) (mm) (rnm)
2190 1120 1610
2430 1120 1610
2695 1120 1610
(kW)
4
4
4
(W (rni n-1)
(kg)
T y p e SZR, courtesy of Krupp Maschinentechnik CmbH.
11 .o 1500 3000
15.0 1500 3300
18.5 1500 3750
390
Fats and Oils Handbook
bined, i.e., the lower cost for pressing and the good yield of solvent extraction. For some seeds, however, solvent extraction is chosen only to simplify the process. On the other hand, there is a trend toward full pressing as a result of consumer wishes. Unlike pressing, solvent extraction requires several process steps to remove the solvent from the meal and also from the oil. Furthermore, the entire plant must be explosion proof, which means high investment costs (see Chapter 5.2.3.2.3). Additionally, attention must be paid to numerous legal prescriptions. Figure 5.40 gives an overview of solvent extraction. The seeds are broken in (l), conditioned (2) and then flaked (3). The flakes are then extracted (4)in a carousel extractor with the solvent coming from (13). The miscella is collected in ( 5 ) and pumped ( 6 ) to desolventizing (7). The oil leaves the plant at (G)while the solvent is condensed (12) and stored (13) for reuse. The meal is conveyed to (9) for desolventizing. The cake is broken (lo), bagged (1 1) and leaves the plant (H). 5.2.3.1 The Theory of Extraction. Extraction in its simplest form is based on the fact that a component (extractive or solute) distributes between two phases according to an equilibrium determined by the nature of the component and the two phases. If a second phase (in our case the extraction solvent) is brought in, this second phase is continuously enriched with the extractive until equilibrium is reached. Oil extraction from seeds, however, is not that simple because it does not take place in an ideal simple system. As a matter of fact, two different extraction processes mn simultaneously or one consecutively. One is dissolving the oil that is set free from
Fig. 5.40. Processing flow chart and schematic (after DGF 1975) of solvent extraction.
Extraction of Vegetable Oils
’‘ ‘I
391
cracked oil-bearing seed cells; the other is extracting oil from intact cells. Besides that, in the case of oil extraction, one cannot really speak of phases because the carrier of the oil, i.e., the seeds, cannot be in real equilibrium with the solvent. In principle, all oilseed extraction processes follow the same pattern. The extractive (oiYfat) is locked in a cell behind the cell walYmembrane system. This system encloses the oil and is connected to the seed particle surface via a capillary. Some of the cells may be cracked; however, most of them are supposed to be intact, thus determining the extraction rate. The seed particles are surrounded by solvent that enters via the capillaries. This capillary solvent then permeates the cell membrane, forming with the cell lipid the cellular miscella. This miscella then permeates back, forming the capillary miscella. It diffuses back to the surrounding solvent forming the bed miscella (Schneider 1991). The driving force for this process is the concentration difference between the cellular and capillary miscella. After the bed miscella has been removed, three kinds of residual miscella remain to be dealt with: the bed, the capillary and the cell miscella. The bed m i s cella can be washed off easily with fresh solvent, whereas the other two remain bound to residual lipid and are thus difficult to remove. Several researchers have tried to describe this rather practical side of the pmess by using a theoretical model. The main problem is the lack of a real equilibrium as described above, with the additional consequence that no distribution factors exist. One of the basic theoretical approaches was proposed by Schoenemann and Voeste (1952), yielding a model that describes extraction, a model that will soon be replaced by more recent approaches. They defined two quasi-phases to be able to describe equilibria between these phases. Phase I: that part of the solvent that is in the pores of the so-called carrier (the seed particles) or that is bound to its surface by adhesion and contains dissolved oil, called “absorbed miscella.” Phase 11: the free-flowing extraction solvent that also contains dissolved oil (the miscella), called “free miscella.” Between these quasi-phases, an equilibrium can be defined with the effect that the free miscella (phase II) is enriched with oil as long as its oil concentration is lower than that of phase I. Depending on whether the extraction is done in stages or continuously, a defined equilibrium is formed for each stage or the equilibrium is continuously shifted. From these theoretical considerations, equations have been deduced.
where E is the extract of the free miscella, e is the extract of the absorbed miscella, F is the free miscella, f is the absorbed miscella and y is equal to E/F,the extract concentration of the free miscella.
Fats and Oils Handbook
392
The equation is valid for absolute countercurrent extraction. To convert the equation into a tool to work with, en andf, must be determined empirically. The difference between the initial and the removed amount of solvent (miscella), f,, thus represents that part of the solution that is absorbed by the carrier. The concentration yn of the free miscella is then plotted against that of the absorbed miscella x,. The equilibrium between the two is represented by the straight 45" line originating from the origin of the coordinates. The plots are valid for isothermal conditions and identical periods of extraction and removal. If data x, and yn are calculated from the experimental data of an oilseed with an initial oil content of 20%, the following results are obtained: = 200 g of oil in = 200 g of oil in = 250 g of oil in 4 ebeg = 250 g
20% oil content
1000 g of seed 800 g of carrier 1000 g of carrier
If the maximum residual oil is fixed at OS%, then the following is obtained:
0.5% residual oil simplified -)
eend
= 5 g of oil in -5 g of oil in = g
This means that Eend = ebeg- eend = 250 - 5 = 245
995 g of carrier 1000 g of carrier
-+
Eend = 245
g.
Assuming that a miscella with 30% oil is desired, the 245 g must represent 30%, leading to the following: Fend
= (100/30) ' 245 g = 817 g
15.31
Because the fresh seed does not contain any solvent,fbeg = ebeg= 250 g; following Equation 15.21, this leads to:
With the experimental data from Table 5.16, the graph shown in Figure 5.41 results. To determine the number of theoretical stages, a parallel to the abscissa that goes through the desired miscella end concentration on the ordinate (y, = 30) is plotted. The vertical on x, shows the resulting saturation concentration. Then one continues with a parallel through the point where the perpendicular passes through the empirical working curve; one then raises the vertical again and so on until the desired yn is reached or the first time passed. The number of parallels touching the equilibrium line equals the number of theoretical stages necessary to achieve the desired concentration.
Extraction of Vegetable Oils
393
TABLE 5.16 Experimental Data to Determine the Theoretical Number of Stage9 Oil content of drained miscella (%)
Carrier T (g)
Absorbed miscella fn (g)
Absorbed extract en (g)
50 30 20 10 0
1000 1000 1000 1000 1000
a74 600 530 480 450
43 7 1 ao
106 48 0
aSource: DCF (1975).
It is clear that the amount of extract is proportional to the extraction duration and asymptotically approaches the extractable amount. The extraction rate E can theoretically be calculated, following the work of Boucher et al. (1942):
where 0 is the oil content of the seedmeal, b indicates before extraction and e is at the end of extraction. Only diffusion processes have been considered for the following equation:
30 -
25 20 15 -
10-
50
10
30
20 xn
40
50
(%I
Fig. 5.41. Graph for the graphical determination of the necessary extraction stages (after DGF 1975).
Fats and Oils Handbook
394
,
where Z is the extraction duration (h), P is the platelet thickness (cm), and D is the diffusion coefficient (cm2h). Following Fan et al. (1948), this equation can be simplified for long extraction times to become
8 E=--.IOY 7L2
where
y=-
n 2 .D.Z 4
4
or, expressed differently,
D.Z
log E = -0.091 - 1.07-
i5.81
P2
Boucher experimentally challenged the above equation and found that the forms of the graphs from theory and experiment are similar (Fig. 5.42). There are several hypotheses concerning what step determines the extraction rate. As mentioned above, older publications (Boucher et al. 1942, King 1944) point to the diffusion of the extractive in the miscella as rate determining. Othmerlejs (1955 and 1959) hypothesis is that the miscella flow in the capillaries; Karnofsky (1949) and Coats and Wingard (1950) believe that the rate of dissolution of the extractive in the solvent is rate determining. Schneider (with some evidence) based his recent investigation on Raclejs (1967) earlier findings that assign the main influence to the membranekell wall system. It is beyond the scope of this book to present more detail, but it seems logical that the oil-bearing cell has a major influence on oil extraction. Therefore, new findings may change the current view. Extraction yleld [% of total fat] 100
10
Peanut flakes 0 66mm thick, 14 0% humidity, 25 0°C Cottonseed flakes 0 43mm thick, 11 6% humidity, 65 5°C
1
0
20
60 80 100 Extraction duration [min]
40
120
140
Fig. 5.42. Extraction curve for hexane extraction (after Boucher eta/. 1942).
Extraction of Vegetable Oils
395
5.2.3.2 The Extraction Solvent 5.2.3.2.7 Selecting the extraction solvent. Ideally, lipid solvents that are to be applied for oil extraction have to fulfill several requirements that may be contradictory, with a fair compromise needed for practical application. Such (ideal) properties of an optimal solvent include the following: high oil solubility at low temperature high selectivity for the extract, in this case, triglycerides chemical inertness, to avoid side reactions and to protect the equipment noninflammable, nonexplosive, nonirritant, noncaustic, and nonpoisonous low viscosity and surface tension to guarantee good percolation and surface wetting easily removable as completely as possible from the meal and the oil, with low energy requirements immiscible with water, to remove water easily from the solvent fixed, low boiling point or boiling region, with low heat of evaporation environmentally friendly Obviously no extraction solvent is able to fulfill all of the properties from the list above. Therefore, a best compromise has to be made according to a priority list. Some of the potential solvents are discussed briefly in the following with their advantages and disadvantages as well as some discriminating criteria and their performance (Table 5.17). Based on the table, trichloroethylene seems to be the best choice at first sight. However, there are some severe drawbacks such as high toxicity even at low concentration, high boiling point (87OC) and low selectivity. Compared with hexane, trichloroethylene dissolves three times the amount of components that are insoluble in petrol ether, mainly undesirable components that have to be removed later by refining. Even its considerable advantages of being noninflammable and nonexplosive cannot compensate for its disadvantages. TABLE 5.1 7
Extraction Potential of Solvents under Laboratory Conditionsa Oil content of seed (YO)
Residual oil content (% of initial) Hexane
19.29 Flaked soybeans Peanutcake 12.60 Sunflower seed cake 1 1.90 D Rapeseed cake 14.55 E Flaked grape seed 15.75 F Olive pomace 6.21 Extraction time: 4 h; extraction temperature: 45OC;
A B C
aSource: Bernardini (1985).
Benzene
CS,
2.0 2.2 1.6 2.8 2.5 2.1 4.3 4.9 3.9 5.4 4.9 3.5 4.1 4.4 3.7 15.6 14.8 11 .o 2.79 mL solvent/lOO g of seed.
C,HCI, 0.09 1.6 2.6 1.9 2.0 6.1
Fats and Oils Handbook
396
TABLE 5.1 8
Physical Data of Extraction Solvents ~~~
Solvent Hexane Benzenes
cs2 C,HCI,
Boiling point
Molecular weight
Specific density at 20°C (g/cm3)
86.2 84.0 76.1 131.4
0.6603 0.700 1.2632 1.464
68.95 60.7 46.25 87.0
("C)
Heat of evaporation
(kJ/mol) (kJ/kg) 31.9 27.7 28.4 34.8
370.2 329.7 372.9 264.8
Specific heat (cal/g) U/g)
2.205 2.205 1.004 0.933
9.232 9.232 4.204 3.906
Vapor pressure at 20°C (hPa)
160 144 413 80
Taking into account the specific properties of the solvents (Table 5.18), it can easily be seen that carbon disulphide is not a good choice because of its low boiling point and extreme vapor pressure at low temperature. Additionally, it is easily inflammable and highly toxic. The low heat of evaporation of trichloroethylene turns out to be a disadvantage compared with hexane and gasoline once the specific density is taken into account as well as the fact that solvent extraction is volume oriented (volume extract per volume of solvent). For all of these reasons, hexane and gasoline, with their narrow boiling range, are dominant today all over the world except in the case of some very special applications. Before hexane, carbon disulphide and trichloroethylene were used. The former had been banned early, but the latter was used for some time in the U S . Insufficient removal led to diseases of cattle that were fed the meal. The relevant commission of the DFG (German Society for Science) declared chlorinated hydrocarbons undesirable auxiliary materials for food and fodder production in 1964. For special purposes, alternative solvents were tested. For example, trials to extract cottonseed oil with isopropanol and ethanol were carried out in the 1950s, because this solvent combination made it possible to extract the gossypol together with the oil. Thus the extraction meal became more suitable for animal feed. However, the oil then contained considerably higher amounts of phosphatides, carbohydrates and other ethanol-soluble components that had to be removed during refining. In addition, solvent removal is more energy intensive than in the case of hexane. Therefore isopropanoVethano1 never really made it to the factory floor. In addition, a process developed by the U.S. Department of Agriculture (1962) to extract cottonseed with a mixture of acetone/hexane/water (55:44:3) was not successful in practice although the feeding properties of the meal were excellent. The glucosinolate content of rapeseed was reason enough to research new extraction solvents. Rubin et al. (1986) found that rape extraction meal could be obtained with glucosinolate levels below the detection limit, if extraction took place in a two-phase system. One phase consisted of hexane, the second of a mixture of water (0-15%), ammonia (0-14%), and some lower alcohols. Methanol was better suited than ethanol. Isopropanol and t-butanol did not perform well. The process is described in Chapter 5.2.6.3.
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5.2.3.2.2 Physical properties of the extraction solvent. As noted, the extraction solvent greatly influences the extraction yield and therefore the commercial success. On the one hand, there is the need to heat it up and to remove it after extraction. On the other hand, expenditure is necessary because of the fact that the solvent is flammable and explosive. The density of the miscella rises with the amount of oil (extract) that is dissolved. Rice and Hamm (1988) measured densities of different miscella at different temperatures (Fig. 5.43). Low viscosity is favorable for extraction, especially in percolation extraction. This would be one of the major advantages of supercritical CO, extraction (see Chapter 5.2.6.1). The viscosity of hexane decreases almost linearly from 0.4 CP (0°C) to 0.37 CP at 15°C. Between 15 and 25"C, the curve is steeper and then becomes almost linear again to 50°C (0.25 cP). In addition to density and viscosity, the oil content of the miscella also influences the vapor pressure. Figures 5.44 and 5.45 show this influence for different concentrations of a hexane/cottonseed oil miscella. In other words, these different vapor pressures lead to different boiling points (Fig. 5.46). This is important for solvent removal from the oil. Today, hexane is used almost exclusively as solvent; Table 5.19 shows the characteristics of commonly traded technical hexane. As can be seen, some minor amounts of other hydrocarbons are present. These, however, do not in any way influence its use. 5.2.3.2.3 Handling the extraction solvent. The extraction solvent has to be removed carefully from the oil and the meal for reasons of product safety, health care and protection of the environment. Careful handling is also necessary for reaDensity [g/crn3]
0
10
20
30
40
50
60
70
80
90 100
Miscella [%rn/rn hexane; 100 - %hexane = %rn/rn oil]
Fig. 5.43. Density of a hexanelsoybean oil rniscella, dependent on the oil content (after Rice and Harnrn 1988).
Fats and Oils Handbook
398
Mlscella vapor pressure [hPa]
,
w
1000
500 -
(Pure hex-ane)
Hexane content [% wt/wt]
40 30 20
100
!
I
I
I
0
20
40
60
80
,
,
I
100
120
140
160
Temperature [“C]
Fig. 5.44. Vapor pressure of a hexanekottonseed oil rniscella dependent on the ternperature (after Pollard eta/. 1945).
sons of safety at work. Hexane/air mixtures are explosive within a range of 1.2-7.4% v/v of hexane (Fig. 5.47). It is known from trials that the saturation concentration is never reached in the head space above liquid hexane. Therefore, one can never be sure if the atmosphere is not explosive even if the hexane saturation concentration at the given temperature would be too high for an explosion. Therefore, special care is essential. Vapor pressure [hPa]
85°C
0
1
2
3
4
5
Soybean oil In the rniscella [% wt/wt]
Fig. 5.45. Vapor pressure of a hexanekoybean oil rniscella dependent on the oil concentration (after Smith and Wechter 1950).
Extraction of Vegetable Oils
Boiling point 140
399
["C]
813
l-
I
Ambient pressure
120
50
55
60
65
70
75
80
/
1013 //
85
90
95
100
Oil in miscella [% wt/wt]
Fig. 5.46. Boiling point of a hexandcottonseed oil miscella dependent on oil concentration a n d pressure (after Pollard eta/. 1945).
Unlike the hydrogen in hardening, which also forms a highly explosive mixture with the oxygen of the air,the vapors of extraction solvents are all denser than air. Therefore it is not possible to vent via roof windows. On the contrary, these vapors collect on or close to the bottom, especially in deeper parts of the building such as cellars. Therefore, buildings housing extraction plants are designed differently.
5.2.3.3 Extraction Processes and InfluencingParameters 5.2.3.3.7 The percolation process. The percolation process is based on the principle of permanent wetting of the surface by percolating solvent. On the basis of the theories described in Chapter 5.2.3.1, this means that there is a permanent TABLE 5.19 Physical Data of Extraction Solvents Present in Extraction Hexane
Solvent n-Pentane n-Hexane n-Heptane Cyclohexane 2,3-Dirnethylbutane 2-Methylpentane 3-Methylpentane
Molecular weight
Spec if ic density at 20%C (g/crn3)
Boi Iing point Kp760 ("C)
Refractive index nD20
72.15 86.14 1100.2 1 84.16 86.1 8 86.1 8 86.1 8
0.626 0.660 0.683 0.779 0.661 6 0.6532 0.6645
36.07 68.95 98.42 80.74 58 60.27 63.28
1.3575 1.37506 1.38777 1.42 662 1.3750 1.3715 1.3765
Proportion in extraction hexane (%)
<2 45-95
-
1-20
400
Fats and Oils Handbook
Fig. 5.47. Vapor pressure of hexane and explosion limits.
exchange between the free-flowing solventhiscella and the solvent that is trapped or absorbed by the meal. Percolation ensures that locally saturated solvent is permanently replaced by fresh or nonsaturated solvent/miscella. A prerequisite for success in this process is that the solvent can freely pass (percolate) through the seed particles. The process also needs “free” oil, i.e., effective seed pretreatment with as many opened cells as possible. The advantage compared with the immersion process is that there is no need to agitate the seed particles, thus avoiding an undesired further reduction in their size. However, the formation of fine meal particles cannot be totally avoided. Only a limited portion of these blends with the miscella because the percolated seed works like a filter and holds them back. Miscella oil contents of 30% can be reached if the principle of countercurrent flow is well applied. 5.2.3.3.2 The immersion process. Unlike the percolation process, the seed is completely dipped into the solvent in the immersion process. The principle implies that highly concentrated miscella is replaced by fresh solvent if there is no forced solvent movement. Therefore the static system needs agitation to ensure that locally concentrated solvent is replaced. The resulting shear stress leads to increased formation of very small seed particles that later have to be removed from the miscella. Generally the immersion process is better suited than percolation if the oil has to be extracted from a difficult matrix, such as one with a high fiber content and low oil concentration. An immersion matrix rarely reaches an oil concentration >13%. 5.2.3.3.3 The extraction temperature. Temperature is important for extraction because it decreases viscosity and increases the solubility of the extract. The solubili-
Extraction of Vegetable Oils
401
ties of oil in different solvents are given in Chapter 2.3.2.6.1. Lower viscosity and higher solubility result in a higher extraction rate (Fig. 5.48). The differences in the extraction rate are not extreme, but the application of heated extraction solvent is advantageous. The effect is much stronger for olive husk extraction for which the extraction rate is only -78% at 20°C, but almost 90% at 50°C. As can be seen from Figure 5.49, the temperature influences not only the extraction rate but also the proportion of non-oil lipid and non-lipid components in the crude oil. The removal of these components by refining incurs substantial costs, a fact that must be considered. 5.2.3.3.4 The extraction time. The extraction time influences the extraction rate because dissolution and diffusion processes require time. The time needed depends on the kind of seed, its pretreatment and the equipment used. Wingard and Phillips (1949) investigated the dependency (Fig. 5.50) of the oil content of the seeds and the extraction time. Similar observations were made by other authors. It becomes apparent that for most oilseeds the asymptotic part of the extraction curve can be reached within 30 min. This means that further extraction requires excessive time, and it must be determined whether the increased oil yield warrants the prolonged cycle time. Following Wingard and Phillips, the time t needed to reach a residual oil content as low as 1% is proportional to an exponent of the temperature, T
t
- 7L
where -1.9 < y < -2.4 Extraction yield [%]
Extraction duration: 2 h Extraction solvent: 2790 cm3/1OOg seed
100
- -. -.
-c
98 A'
Extracted goods: Soybeans, flaked
*A -*-
Sunflower seed
.*. D Rapeseed cake -v-
'B 96
E Grapeseed, flaked
/--1
_ . . *.-. '
..
D
B Peanut cake
+C
r5.91
94 92
E
I
90 20
30 40 50 Temperature of extraction solvent ["C]
Fig. 5.48. Dependency of extraction solvent temperature and extraction rate (after Bernardini 1985).
Fats and Oils Handbook
402
Phosphatide content of the degummed crude oil [%] I
11
/,
i
0.8
0.6 0.4 0.2
Fig. 5.49. Phosphatide content of degummed soybean
0 40 42
44
46 48 50 52 54 56 58
Miscella temperature [“C]
oildependingonthetemperature of the extraction miscella (after Kock 1981).
5.2.3.3.5 The amount of solvent. The influence of the amount of solvent-or better the ratio of solvent to extraction goodsdepends on the seed composition. The amount of solvent needed increases with the fiber content. Bernardini (1985) found for different seeds that the extraction rate reaches an asymptotic value for ratios of solvent to extraction goods >2800 cm3: 100 g seed. This asymptotic value was between 87 and 97% depending on the seed. Reducing the amount of solvent by half decreases the yield by 5%. Residual oil [% of the extraction meal] flaked
2-LL
3-
Cottonseed
Linseed
1
Soybeans
0
Fig. 5.50. Residual oil in the
Extraction of Vegetable Oils
403
In addition to the amount of solvent, the concentration of the miscella also plays a role. The higher the proportion of oil dissolved, the lower the energy required to evaporate it. However, from a certain miscella concentration onwards, the residual oil content in the seed increases (Weber 1976 and 1981). This can be compensated by increasing the extraction time. Because the capacity of the plant is thereby reduced, a commercially sound compromise must be found. 5.2.3.3.6 The influence of seed humidity. Seed pretreatment, in addition to conditioning, size reduction, and flaking, includes adjustment of humidity. For storage, the seed moisture is adjusted to the optimum (see Chapter 4.1.4). As a polar substance, water hinders wetting of the seed surface and penetration of the solvent into the seed. It also reduces the diffusion coefficient. Fan ef al. (1948) found that every 1% of water reduces the diffusion coefficient by -0.4 cm%. However, a certain seed moisture is also required because it has the important advantage of giving the seed flakes an elasticity and preventing them from crumbling into dusty particles, thereby increasing the bulk density and hindering percolation. Furthermore, the humidity influences the proportion of nontriglyceride components in the crude oil. More polar components are carried over. Kock (1981) determined the proportion of phosphatides in crude oils, depending on the water content of the extracted seed. He found a proportional relationship but could not formulate it as a mathematical equation. From an analysis of >I00 samples, he could deduce that there is a strong tendency that the portion of phosphatides increases by 0.2% per 1% of seed moisture (between 11 and 14% seed moisture). 5.2.3.3.7 The influence ofparticle size and shape. Particle size and shape play an important role in successful extraction. On the one hand, the particles must permit unhindered free solvent percolation. On the other hand, the particle size must allow for good extraction of each particle by minimizing the diffusion. With respect to the first point, the extraction goods must not be too fine, thus making solvent percolation difficult. For some seeds, which tend to break apart, the extraction goods must be structured. One option is to leave a certain proportion of the hulls in the meal. In the case of sunflower seed, for example, only part of the hulls is removed; the residual hulls serve to loosen the extraction goods and to ease solvent percolation. Another method of structuring is extrusion. The platelet thickness that guarantees best extraction can be quantified. For the platelet thickness, Coats and Wingard (1950) developed an equation similar to the one Fan ef al. (Chapter 5.2.3.3.4) found for the extraction time. Their calculations yielded the following equation (see also Table 5.20 and Fig. 5.51): t-m
[5.10]
or, using an empirical individual constant K,typical for the extractability of the seed
t=KPY
[5.11]
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404
TABLE 5.20 Constants for determination of the extraction yield depending on flake thickness Flaked Soybeans Cottonseed Linseed Peanuts
Y
k
2.3-2.5 1.5 7 3.2
6-2 0 14G270 3600 1.4
where y reflects the influence of the platelet thickness on the individual seed, t is the extraction time needed to reach a residual oil content of 1% and P is the platelet thickness of the seed. Some of the figures in Table 5.20 are data from single trials and can therefore serve only as an indication for the order of magnitude. It becomes clear that linseed extraction is quite difficult and that the flake thickness plays a very important role. Further investigations of the authors showed that the values for K and y remain in the same order of magnitude when the type of solvent and the humidity are varied. Figure 5.51 reflects the influence of the flake thickness on the extraction. These data can be seen in a new light as a result of their assignment (Schneider 1992) to different phases of extraction. The initial period (0-6 min), characterized by a rapid decline of the residual oil content, is due to oil extracted from cracked cells (c.c.). After that (6-20 min), a period starts in which the effects of washing off the oil of cracked cells and diffusion (c.c. + d.) overlap each other. For the rest of the Residual oil [% of carrier]
30
Flake thickness
I I
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 Extraction duration [rnin]
Fig. 5.51. Extraction rate depending on the seed flake thickness (after Depmer, cited from DGF 1975).
405
Extraction of Vegetable Oils
TABLE 5.21
Flake thickness for the extraction of oilseeds (mm) Soybeans Cottonseed Sunflower seed Peanuts Rapeseed Copra Sesame seed Palm kernels Linseed Safflower seed Babassu kernels
0.25-0.35 0.20 0.30-0.35 0.25-0.35 0.20-0.25 -0.30 0.20-0.25 0.30-0.35 0.20-0.25 0.30 0.30-0.35
extraction time, characterized by the almost linear part of the graph, extraction from closed (noncracked; n.c.c.) cells dominates. The effect is even clearer when the ordinate is plotted on a linear scale; on the other hand, this makes it more difficult to distinguish the four lines. The empirical optimum flake thickness commonly used today differs from seed to seed; Table 5.21 gives some data. Extrusion (see Chapter 5.2.1.3.3) was applied on a large scale in the U.S. for the first time in 1976. At the end of the 1980s, >60% of the soybeans and >50% of the cottonseed were extracted after extrusion. Extrusion applied after flaking has the advantage of a much higher bulk density. Flaked seed weighs around 550 g/L, whereas flaked extruded seed reaches 850g/L, i.e., -50% more. This significantly increases the plant capacity. Furthermore, extruded seed is mechanically more stable, allows for better solvent percolation and eases desolventizing by using even less energy. Combined with extrusion, a heat treatment can be conducted to inactivate lipases. Applying extrusion technology to soybeans, cottonseed and rice bran has been described by many authors, including Williams and Baer (1965), Bredeson (1983), Farnsworth et al. (1986) and Kemper (1989). Lusas and Wathuis (1988) gave an overview of the state of the art. The authors estimate the savings than can be achieved with this technology to be around $1/MT of seed. Because the seed cells are cracked under the mechanical stress, the extent to which flaking the seed improves solvent extraction has been debated. On the one hand, there are indications supporting this view (Schepinka 1934). On the other hand, the sheer stress applied on the individual cell cannot be that high because the cells are only one fifth the platelet size. Experience has shown, however, that seeds that have passed a corrugated roll have a higher content of oil that can be “washed out.” This free oil obviously plays a role, and there have been many attempts to explain the extraction process. 5.2.3.3.8 Heat treatment. Heat treatment influences the seed components. The water content is slightly reduced and the proteins are denatured. Thus the oil is pre-
Fats and Oils Handbook
406
sent in the cell in a sort of emulsion and can coalesce to form larger droplets. Increased temperature has an identical effect on oil finely dispersed in the cell. It can more easily coalesce as a result of the lower viscosity and eventual cracking of the cells. These larger droplets can be extracted much more easily. 5.2.3.4 Extraction Plants 5.2.3.4.7 Batch extractors. For a long time, batch extractors were the only equipment used for solvent oil extraction. Because of their widespread use and the many different Manufacturers, a great variety of batch extractors exist. Their design principle, however, is always the same. Batch extractors (Fig. 5.52) have a seed inlet (a) and an opening (b) for discharge. The extraction solvent is pumped in via (c) and the miscella sucked off via (d). To evaporate the solvent from the extracted seed, live steam can be blown in (e). The resulting vapors leave the vessel via (f); ventilation is possible (g). As a result of their processing principle, batch extractors are immersion extractors and therefore are equipped with a stirrer. The extraction solvent is always freshly added to the seed, stays in the vessel for the extraction period and is then pumped off. The ratio between solvent and extract (oil) becomes greater with every stage and thus more uneconomical. The meal is desolventized in the same extraction vessel. Batch extraction is no longer applied in high capacity plants; it continues to have some importance in special applications such as the extraction of special pharmaceutical oils or spent bleaching earth (see Chapter 7.3.6). However, viable commercial
B Drive
Fig. 5.52.
Batch extractor (after DGF 1975).
Extraction of Vegetable Oils
407
application would be only for processes with low throughput, i.e., those run only from time to time or in which the application of continuous processes has no payback. Because batch extractors do not allow running the process countercurrently or continuously, they have almost disappeared for bulk oil production.
5.2.3.4.2 Group extractors. Some disadvantages of batch extractors can be overcome if several batch extractors are combined into a group extractor. A semicontinuous process results that also allows for countercurrent extraction. The single batches that together make up the group extractor resemble the batch extractor from Figure 5.52. These single extractors (A-E; Fig. 5.53) are grouped in such a way that the extraction solvent can be pumped from A to B, from B to C and so forth. In addition, miscella can be pumped from the last extractor in the row E into the first one, A. Stage I is the stage that contains fresh nonextracted seed. Stage I1 contains extracted seed, whereas stage 111 contains the furthest extracted seed. The extraction solvent (miscella) is pumped in a countercurrent direction from I11 to I. During this process, A is refilled with fresh seed and extracted seed is discharged from B. Thereafter, in cycle 2, the fresh seed is in A, the most extracted in D; B is refilled and C is the discharge stage. The cycles then continue in the manner shown in Figure 5.53. 5.2.3.4.3 Continuous percolation extractors. As in group extractors, extraction is also done countercurrently in the various continuous extractors. With variations in the details, all of these extractors follow the same principles. After World War 11, the first basket-type extractor was constructed by Bollmann (Fig. 5.54). In this device, the extraction material is fed from the top to the baskets of the extractor. These baskets circulate clockwise. The extracted seed is discharged by turning the basket upside down after almost one cycle. The extracted meal is conveyed to desolventizing. The extraction solvent is pumped onto the fresh seed at two thirds of the height of the left vertical chain of baskets. It percolates through all baskets. This ensures that the furthest extracted seed is exposed to the freshest solvent. Having percolated the vertical left row of baskets, the miscella is collected in a bottom tub and pumped to the top of the right part. There it is sprayed onto the fresh seed. After percolating all right side baskets, it is collected in a bottom tub from which it is pumped to the oil recovery plant. The upper left third of the plant allows the miscella to drain off as much as possible. Another variation is the carousel extractor, manufactured, for example, by Krupp and Blaw Knox. This type of extractor (Fig. 5.55) consists of a sequence of cells that are arranged in the form of a carousel. The cell wheel is housed in a gas-tight cylindrical shell that is horizontally divided by a slit bottom. The cell wheel rotates above this bottom. The extraction material is continuously flowing into (A) from a feeding chute. It is conveyed clockwise over the stationary bottom to the discharge point (C), which is a sectoral opening in the bottom. From there, the extracted meal falls into the discharge chute from which it is continuously removed.
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Fats and Oils Handbook
Fig. 5.53. Extraction sequence with a group extractor. The miscella collection chambers are formed by the weir-divided subcompartment just below the slitted bottom. They divide the different miscella concentrations from each other. The slitted bottom is formed from profile bars (Fig. 5.56) with wedge-shaped cross sections. As a result of the material gliding over it, the bottom is self-cleaning.The rotational speed of the extractor wheel is adjusted to the needs of the individual extraction material and may vary between 45 min and 30 h. The flow of the solvent miscella begins at the point at which fresh solvent flows onto the seed (B), i.e., close to the extracted material discharge. The solvent
Extraction of Vegetable Oils
409
Extraction
Fresh extraction solvent
Flnal mircelk
,
Fig. 5.54. Bollrnann basket type extractor (redrawn after DGF 1975).
becomes a low-concentration miscella after having passed the first cell of almost completely extracted seed; it is collected in the chamber below the cell. This also ensures that almost all miscella still contained in the extracted seed is washed out. This first miscella is then pumped through all other cells in a counterclockwise manner. The rich miscella is then pumped off (D). Before the extraction meal is discharged, it passes a draining area where as much of the bound solvent as possible is drained off. The lower part of Figure 5.55 shows the concentration of oil in the seed as well as in the miscella while passing the extractor. The darker the shade of gray in the seed, the higher the oil concentration; the lighter the shade of gray in the miscella, the richer it is. Figure 5.56 shows some details of carousel extractors. The equipment may be up to 15 m in diameter, allowing for a capacity of as much as 4000 MT soybeadd. The working volume may reach 380 m3 (-280 ton soybeans). The higher capacity extractors have two cell wheels mounted above each other. In this case, partly extracted seed is discharged from (C) of the upper wheel to (A) of the lower one in order to continue with a second extraction cycle. Table 5.22 gives the technical data of carousel extractors. If the cell wheel of a carousel extractor is uncoiled, in a sense, and brought into a straight line, belt, sliding bed or sliding cell extractors result. Figure 5.57 shows an example of a belt extractor, a deSmet type. This extractor is a horizontal unit equipped with a moving belt that transports the extraction goods countercur-
41 0
Fats and Oils Handbook
Fig. 5.55. Carousel extractor; sectional operating diagram of one-stage extractor and material flow (courtesy of Krupp Maschinentechnik GmbH, Hamburg).
rently to the incoming solvent. There are no walls in the belt to separate chambers from each other. The manufacturer claims that this increases seedsolvent contact, produces fewer fines and makes filtration of the miscella unnecessary. Rakes scrape the top of the bed after each miscella spray. As in the carousel extractor, the miscella from each area of the belt is collected and sprayed again onto less extracted seed. If a chain of connected bottomless frames moves parallel to a belt such as the one described above, a Lurgi system frame belt extractor results (Fig. 5 . 5 8 ; for technical data, see Table 5.23). The framebelt combination moves counterclockwise. The frames separate the seed batches from each other while they are trans-
Extraction of Vegetable Oils
A
= selfcleaning slitted bottom
= model photo = Shipment of 4,000MTtd extractor C D-G = stages of construction = adjustment of slitted bottom D E = collection chamber for different miscellas F = cell wheel with straight separation walls G = extractor finished and erected H = medium size outdoor installation
6
Fig. 5.56. Carousel extractor; details.
41 1
Fats and Oils Handbook
41 2
TABLE 5.22 Technical Data of Carousel Extractor+ Capacity (MTld with 0.8% residual oil and 12% seed moisture) 420
630
900
1250
2000
4000
Diameter (mm) 4500 5300 6000 Consumptiodton of seed Energy (kWh) 2.5 2.2 2.0 Steam (kg) 10.5 10.5 10.5 Including heating of flakes by 10 K in the extractor
7000
8000
9000
11,000
15,000
1.9 10.5
1.7 10.5
1.6 10.5
1.4 10.5
1.3 10.5
200
300
aCourtesy of Krupp Maschinentechnik CmbH.
Fig. 5.57. Continuous De Srnet belt extractor (courtesy of de Srnet S.A., Edegem).
Extraction of Vegetable Oils Chaln drlve
Slew, belt drum
Pumpa
Upper
rleve belt
Lower sievebelt
Frame cells
Dralnagm chambers
41 3 Drainage chambers
Feeding hoppor
Extraction meal discharge
Spraying heads
4'4"' 4'" 4'&$3'
$'"
+&on
Fig. 5.58. Frame belt extractor (courtesy of Lurgi GmbH, Frankfurt). TABLE 5.23 Technical Data of Solvent Extractorsa
Capacity (MT soybeandd) Length Width Height Weight Energy consumption (max) Steam consumption
100 (mm) (mm) (mm) (k@ (kWh) (kg/h)
Capacity (MT soybeandd) Length Width Height Weight Energy consumption (max) Steam consumption
12,600 1240 3525 30,000 8 25 100
(mm) (mm) (mm)
(k@ (kWh) (kg/h)
12,600 1400 3360 28,000 8 25
Frame belt extractor 500 1000
19,900 1830 4450 40,000 17 125
21,100 2775 4430 85,000 22 250
Sliding cell extractor 500 lo00
20,000 2000 4300 62,000 18 125
21,200 3000 4300 70,000 28
250
2000-2400 24,600 3275 5100 125,000 40 500600 2000-2400 26,000 3800 4320 120,000 60 500600
Energy consumption for filling, main drive and discharging; steam consumption without warming of fresh hexane. aCourtesy of Lurgi CmbH, Frankfurt.
41 4
Fats and Oils Handbook
ported on the belt. At the end of the belt, the frames are canied a little further horizontally. Because the supporting bottom of the belt is then missing, the seed falls out of the frame. The lower belt begins further left, so that the falling seed is collected in turned frames for a second extraction. At the right end of the belt, the extracted seed then falls out of the frame into the discharge hopper. Such equipment is no longer built by Lurgi, but still exists in many plants. These machines have been replaced by sliding cell extractors. By replacing the parallel moving belt with a static sieve plate, one obtains a sliding cell extractor. The extraction goods are conveyed by means of sliding cells that are open at their upper and lower sides, i.e., actual sliding frames. This equipment is mechanically much simpler and cheaper and has therefore replaced the frame belt extractors. Only cottonseed may cause some problems in the sliding cell reactor because the slits may become obstructed by cottonseed lint. The latter two types of extractors are usually constructed with nine extraction stages. They are able to handle up to 2400 MT of seedd. The extraction principle resembles that of the extractors described previously. Flakes are fed to a hopper (Fig. 5.59) and countercurrently extracted with the freshest solvent meeting the most extracted flakes; the miscella is pumped counterclockwise onto the seed. The C.M.B. basket extractor follows the same pattern; however, the flakes are conveyed in individual baskets. The baskets are fixed to a chain that passes the extractor in four levels. The miscella then subsequently percolates each of these layers, thus in effect following the countercurrent principle. Put into the context of the complete process, Figure 5.60 shows a plant designed by Lurgi. The seed (1) is fed into a sliding cell extractor (A) and the miscella leaves it at ( 2 ) . The extraction solvent is removed via the columns (B), (C) and (D). The crude oil is degummed in (E) and (F) if desired or necessary. The extraction meal is further processed in (H) and (J) to be marketable. The extraction solvent is condensed (K, L and M), and the vapors are also freed from solvent. The crude oil is pumped to storage (3). Such a plant with a capacity of 2400 MT/d requires a building -40 m in length, 25 m in width and 18 m high. The energy consumption is given in Table 5.24.
5.2.3.4.4 Continuous immersion extractors. The prototype of all extraction plants is the Hildebrandt extractor (Fig. 5.61). Its simplified construction principle is a Ushaped tube through which the extraction goods pass from one end to the other. On their way, the extraction goods pass through the solvent that is fed at the other arm of the tube. Following the principle of communicating tubes, the level of solvent is equally high in both arms of the tube. Therefore, the extraction goods are fully covered with solvent. The Hildebrandt extractor follows the immersion process. The solvent feed is located at a slightly higher position than the solvent outlet, thus guaranteeing that the miscella flows off without pumping. On its way out of the extractor, the miscella passes through a filter. The extraction goods are conveyed through the extractor by means of screws. The residence time in the apparatus is between 1 and 1.5 h. The oil concentration in the miscella never exceeds 13%.
Extraction of Vegetable Oils
41 5
Fig. 5.59a. Sliding cell extractor type Lurgi (courtesy of Lurgi GmbH, Frankfurt). Other extractors are V-shaped (olier extractor). The flaked seed sediments slowly on one side of the V, thus slowly passing through the solvent. The residence time is increased by deflecting sheets. From the bottom part, the flakes are continuously conveyed into a basket elevator by means of a screw. This elevator conveys the extracted flakes to the outlet. The solvent, as always, flows countercurrently. In the U.S., the Anderson-type extractor was frequently used. It resembles the V-
41 6
Fats and Oils Handbook
Fig. 5.59b. Sliding cell extractor type Lurgi (above) and 4000 MT/d extraction plant (courtesy of Lurgi GrnbH, Frankfurt).
shaped olier extractor. However, the extraction goods are fed into a vertical cylinder and removed from the bottom by means of a Redler conveyor. The solvent is fed close to the narrowest point and removed shortly before the place where fresh flakes are fed. A more recent construction employing this principle is the Bernardini Ih4MEX extractor (Fig. 5.62). It consists of a vertical cylindrical vessel with its largest diameter at the top where its walls are parallel. Close to the bottom, they are conical shaped. The extraction goods are fed from the top with a screw
Extraction of Vegetable Oils
41 7
Fig. 5.60. Extraction plant, schematic overview (courtesy of Lurgi GmbH, Frankfurt). feeder, thus ensuring even distribution over the solvent surface. From there, the goods sink through the solvent while being permanently agitated. After extraction, they are conveyed by means of a screw to a bucket conveyor, which discharges the extracted flakes at (B). The miscella flows off at (D) after having been fed at (C). Immersion extractors are suitable mainly for fibrous material, vegetable and animal materials. 5.2.3.4.5 Combined extraction plants. The advantages of percolation and immersion can be combined by sequential use of two plants. Such plants are offered by the C.M.B. company under the name Percolimm. A percolation extractor Simplex 40 (Fig. 5.63) is used in sequence with an immersion extractor IMMEX (Fig. 6.62). The flaked seed is percolation extracted, leaves the extractor with a residual oil content of 5% and is fed into the immersion extractor and then TABLE 5.24 Consumptions for Oil Extraction per Ton of Seeda Plant capacity (MT/d) Consumption/MT of seed
300
600
1500
240-260 260-280 250-270 (k@ Steam (kWh) 18 12 9 Electrical energy 18 18 . 18 Cooling water (m3, 7°C) (k@ 1.3 1.2 1.1 Solvent Data equivalent to plant in Figure 5.61; inclusive drying, cooling and degumrning. Tourtesy of Lurgi CmbH, Frankfurt.
2400 230-250 8 18 1.o
Fats and
41 8
Oils Handbook
Extraction
$4
E3a
Fig. 5.61. Extractor, Hildebrandt type.
desolventized. The combination of the processes avoids the disadvantageous low oil content of ~ 1 3 % in the immersion process, because the immersion miscella is used as a solvent in the percolation extractor. Seeds require 30 min to reduce their oil content to 6 5 % by percolation extraction. After that, an additional 150 min is required to reduce it further to between 0.3 and 0.5% by the immersion process. Because of the different residence times in both extractors, the combined process requires careful planning. 5.2.4 Processing the Miscella, the Meal and the Vapors
The miscella has to be carefully desolventized to produce an edible grade oil and for reuse of the solvent. Independent of the fact that traces of extraction solvent that might remain in the oil would be completely removed during refining, the oil has to leave the oil mill with as little residual hexane as possible. In addition to the solvent from the miscella, the solvent from the vapors that are collected from all over the plant also has to be removed. These vapors are condensed and consist mainly of vapors formed when the extraction solvent evaporates at 50-60°C, together with water from the seed. The meal also has to be freed from solvent not only to fulfill the legal requirements for animal feed but also to prevent explosion risks during storage, bagging and transport. Basically, solvent may escape in five different ways as follows: with the crude oil, with the extraction meal, with the air that leaves the plant, with the effluent (condensed water) and through leakage. The last-mentioned can be prevented by good design and careful maintenance. Losses from cases 1 through 4 can be minimized by
Vegetable Oils
41 9
Fig. 5.62. Immersion extractor (type IMMEX, courtesy of Bernardini 1985).
Fig. 5.63. Basket extractor (Type C.M.B. Simplex-40; courtesy of C.M.B. Pomezia).
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Fats and Oils Handbook
good manufacturing practice; this is of paramount importance because hexane losses are not only environmentally unfriendly but also costly and constitute a high explosion risk. Figure 5.64 gives an overview on the total process of solvent recovery. 5.2.4.1 Processing the Miscella. Special care has to be taken in working up the miscella because the oil has to leave the oil mill at edible grade quality and also to avoid any explosion risk (Fig. 5.65).
5.2.4.I. I Miscella filtration, Filtration of the miscella is necessary to separate small seed particles and fines. The fines content is significantly higher if the miscella originates from direct solvent extraction (no prepressing). The extraction principle also plays a role. Miscella from the immersion process contains more fibrous material than miscella from percolation plants. Additionally, the type of seed has to be considered. Cottonseed miscella, for example, is much richer in fibers than sunflower seed or soybean miscella. If a considerable amount of fiber has to be removed, a preclarification step with centrifuges may be useful. If filtration is not conducted carefully, fibers occupy the heating surfaces of the evaporation equipment. They act as insulation, reducing the heat transfer and thus the plant’s efficiency. Bernardini (1985) gave the filtration rate depending on the filtration time and the kind of seed (Fig. 5.66). Filtration can be carried out with the usual Niagara filters, which are also used for solvent fractionation. C.M.B. offers a special filter, shown in Figure 5.67. In this filter, the miscella is fed into (F) and passes through the filter plates (C). The filtered miscella leaves at the outlet (H). If the filter cake is thick enough to be discharged, solvent is sprayed (E) on rotating plates that are driven by the motor (I). The filter cake is washed off and collected at the bottom from where it is removed by the conveying screw (D) to leave the filter via (G). 5.2.4.I .2 Oil recovery from the miscella. The percolation miscella has an oil content of 20-30%, thus a solvent content of 70-80%; immersion miscella contain -87-93% solvent. It can easily be seen that considerable amounts of solvent have to be distilled off. With increasing oil content, the vapor pressure of the system increases and thus the boiling point of the miscella rises (see Chapter 5.2.3.2.2). This requires increasing amounts of energy. Solvent removal should be done at low temperature to protect the oil and save energy. Oil quality also suffers if contact time with the heat exchangers is too long, especially for oils of high lecithin content. Therefore a compromise has to be found between low contact time and low temperature. Principally, the solvent is removed in a three-stage operation. In the first step, the miscella passes a pre-evaporator for quick removal of the main part of the hexane. Afterwards, the residual hexane is removed in two steps under always sharper conditions. Figure 5.68 schematically shows a plant for solvent recovery from oil. After passing the filter (l), the oil is preheated (2). There are different designs for such equipment. One possibility is that the oil streams along hot surfaces formed, for
Extraction of Vegetable Oils 42 1
Fats and Oils Handbook
422
0
>>>vawn>>>
200 hPa. usualiy cp. 9%
Evaporation I
Drying
Crude oil
>>>vapors>>>
ahvays d 1 0 ' C
0
100 hPa
,
0
>>>vapors >>>
(Residual hexane < 50pprn; in good plontn < 10ppm)
0 sea figure 5.64
Fig. 5.65. Solvent recovery from miscella.
example, by bundles of steam-heated tubes. Then the oil is fed from the top to the main evaporatdr. There, almost 80% of the solvent is removed at -300 hPa vacuum and at -95°C. To save energy, these evaporators are currently heated by the hot vapors coming from the meal desolventizer. The second step is performed under similar conditions; there, evaporation reduces the solvent to 3 4 % of its initial amount. In a third step, the oil with a residual amount of solvent has to pass through a stripping column (4) with a lower vacuum (usually 200 hPa is suffi-
Filtration capacity [l/m2filtration area]
700_ I 600 Miscella -+
500
Soybean-
* Sunflower-
400
Rapeseed-
300
+ -
.. Peanut+Sesame-
\
200 100 1
2
3
4 . 5
6
7
0
Filtration duration [h]
Fig. 5.66. Filtration rate depending on filtration time and the type of seed (after Bernardini 1985).
Extraction of Vegetable Oils
423
s
Fig. 5.67. Filter for miscella filtration (courtesy of C.M.B., Pomezia). cient). Live steam injection supports evaporation. In a subsequent step, the almost solvent-free oil is dried (5) and the last parts of solvent are removed together with the water. The vapors from the plant-almost exclusively solvent and water-are condensed (6) with cold water or air.
Fig. 5.68. Miscella distillation and condensation plant (courtesy of Lurgi GmbH, Frankfurt).
424
Fats and Oils Handbook
Part of the processing is a steam distillation in which water and solvent are separated. The solvent is reused. Residual solvent is completely removed from the water in a postevaporation step. The vapors from that part of the plant are collected and cleaned (see Chapter 5.2.4.3). Bernardini (1985)calculated that -25% of the energy for solvent evaporation is required to heat the miscella to its boiling point; the rest is for evaporation. To process 1 MT of a 30°C miscella containing 30% oil (solvent boiling point 68"C), -80,000 kcal is necessary. 5.2.4.2 Solvent Recovery from the Meal. The meal coming from the extractor contains 25-35% solveat; it is, in a sense, impregnated with it. The meal must be carefully processed to remove the solvent as completely as technically possible. This desolventization is necessary to fulfill legal demands for animal fodder, to reduce pollution of the environment and to avoid any explosion risk (Fig. 5.69). Residual hexane may cause a problem with some seeds, such as rape. The solvent cannot be steamed out of the cells sufficiently because it is bound to remaining lipids (Schneider 1991). The nature of the solvent removal process is already predetermined in the pretreatment steps before oil extraction. For rapeseed, residual lipid (and thus solvent) is retained in the hull cells that are not broken up in the flaking rolls or in the screw press. Therefore, good seed pretreatment is not only a prerequisite for high oil yield but also vitally necessary for an efficient processing of the meal. In batch plants, this desolventizing step is conducted in the same batch vessels in which the extraction was done. In continuous extraction, special desolventizing plants are required. This has to be done with great care and under protective conditions because the meal can easily be damaged, thus reducing its quality. For some
I
Mal
(R..idulhau*
(n#y~rtmg.mdwm=u
-
b. < 3Qoppm)
Fig. 5.69. Recovery of solvent from extraction meal.
Extraction of Vegetable Oils
42 5
seeds such as soybeans, solvent removal is combined with a heat treatment step called toasting; it destroys the anti-trypsin factors with the aim of improving the digestibility of the meal. Older plants consist of several horizontal stacked cylinders (Fig. 5.70). The meal is fed (A) and screw-conveyed to the right relative to the left. Within the individual cylinders, the meal is conveyed by a system of mechanical paddles; at the end of each cylinder, it falls to the next lower one, thus zigzagging through the apparatus. The cylinders are equipped with steam jackets to heat the meal to -100°C and to evaporate the solvent. In the last cylinder, live steam may be injected to expel the last traces of residual solvent. The desolventized meal leaves the plant at (B); the vapors are condensed with water in (C). More modem equipment consists of a vertical cylinder holding a series of stacked trays. The meal is fed with a screw conveyor and heated on the double bottom of the trays over which it is transported by means of a sweeper. Once the residence time on the individual bottom is completed, a hole in the tray bottom opens and the meal is swept to the lower tray. As in the tube desolventizer described above, steam can be injected into the lowest tray. Figure 5.7 1 shows a desolventizer/toaster/dryer/cooler(for technical data, see Table 5.25). The apparatus consists of a heated, cylindrical housing containing a num-
UrtnCtlDnmufhed
A
I
-I
B orolm(iaddaut*(
Fig. 5.70. Drawing of a horizontal desolventizer (redrawn after Bernardini 1985).
42 6
fats and Oils Handbook
Fig. 5.71. Desolventizer-toaster-dryer-cooler; sectional operation diagram, perforated bottom for desolventizing stage (lower left) and outdoor installation (upper left, courtesy of Krupp Maschinentechnik CmbH, Hamburg).
ber of heated decks that are hermetically separated from each other. Agitator arms move the meal onto the decks and sweep it to the next deck. During the passage of the meal through the cylinder, countercurrent steam is blown in. Toward the end of the process, the meal undergoes hydrothermal treatment that destroys indigestible or harmful substances, thus improving digestibility. The lower part of the apparatus houses the drying and cooling section. This section is equipped with air baffle plates.
Extraction of Vegetable Oils
42 7
TABLE 5.25 Size of Desolvent izers Capacity (MTld)
Diameter (mm)
50 100 2 00 300
1400 1600 1900 2200 2500
5 00
Trays number
Height (mrn)
6 9 9
500 500
9 12
600 600
500
Hot and cold air is sucked in and pressed through the meal bed, removing moisture and heat and some of the meal bed as well. Toasting is necessary for soybean meal (to destroy antitrypsin factors). Before the introduction of 00-rape, the heat treatment during meal desolventizing also reduced the amount of glucosinolates. If combined equipment such as that described above is not applied, the meal should be dried after desolventizing. If it is toasted, it must be dried.
5.2.4.3 Vapor Treatment. Vapors originate from all steps of oil extraction and further processing, but mainly from desolventization. These vapors are collected from all over the plant and condensed. The resulting mixture is separated. The solvent (upper layer) is decanted from the water layer and pumped to storage. Traces of solvent that remain in the water are distilled off by direct steam heating of the water to 95°C. The resulting vapors are fed back to the condenser (Fig. 5.72). The air from the plant also has to be cleaned (Fig. 5.73). It is precooled and washed in an absorption column with pharmaceutical mineral white oil. This oil consists of aliphatic hydrocarbons; it absorbs the hexane, thereby removing it from Vapors
(loaded with extraction solvent)
from all over the plant
ccc Water P
Water
(with traws of extradion solvent)
Separation
settling, decanting
I
+
>>> Extraction solvent 3
Re-use
Waste' water (with traces of extradion solvent) <<< Steam
+
E
e
n
t
>
>
,
~
t
I apom
Effluent
Fig. 5.72. Solvent recovery
Fats and Oils Handbook
42 8
Waste air (with extraction sokent vapor) from all over the plant I
'I I
I I
I/
*>> mineral white oil (and extraction solvent)
I
Extraction sotvent vapors
Eftluent (free of extraction solvent)
Condensation
/ ~e-uw t Extraction solvent
Fig. 5.73. Waste air cleaning.
the vented air. The mineral oil is then heated in a stripping column where it releases the absorbed hexane. The hexane vapors are condensed and the absorptive is cooled and reused. An alternative to this process is the cleaning of exhaust air by open or catalytic combustion. However, the process is unreliable and expensive. Assuming that the hexane in the exhaust air (40°C) of a 480 todd extraction plant (2.12 kg/m3 air) was burned, a total of 550 ton hexane would be lost yearly, assuming 40m3h of exhaust air (Weber 1972). Based on the same data, Weber calculated the consumption levels required to recover hexane from the air as follows: 100 kg steam, 2 m3 cooling water and 2 kWh electrical energy. 5.2.5 Treatment of Crude Oils
Crude oils usually have to be refined. This can be done in the oil mill in an attached refinery or in refineries belonging to the plants in which the oil is processed further. Degumming, however, which is actually a refining step, is done mainly in the oil mills at present and therefore described in this chapter. One of the reasons for performing the degumming step at the oil mill is that the gums can be sprayed on the meal if the lecithin is not recovered. In refineries, however, the gums are a waste material. Degumming is essential for almost all uses of soybean oil.
5.2.5.7 Degurnrning. Phospholipids, proteins and carbohydrates, vegetable gums and colloidal components negatively influence the keepability of an oil. They are undesirable materials in refining because they increase the neutral oil loss and also hamper other operations. For example, they obstruct crystallization during the fractionation process and clog the pores of hardening catalysts. In salad oils, they would collect at the bottom of the bottle and make the oil appear spoiled.
Extraction of Vegetable Oils
429
For these reasons, oils that contain a certain amount of these substances have to be degummed. Degumming means the removal of the entire group of the abovementioned components irrespective of whether they really are gums or not. 5.2.5.2 The Theory of Degumming. Two kinds of phospholipids exist, those that are hydratable and those that cannot be hydrated. The relative rate of hydration was given by Seghers (1990; P represents phosphatidyl): P-choline (PC), 100; P-inositol (PI), 44; P-ethanolamine (PE), 16; and P-acid (PA), 8.5. Their calcium salts have an even lower hydration rate of 1. Hydratable phospholipids can be removed easily by the addition of water. The process can be conducted rapidly at elevated temperatures or slowly at low temperatures. The temperature, however, has to stay below the temperature at which the phospholipid hydrates begin to form liquid crystals (usually -40°C). Taking up water, phospholipids lose their lipophilic character, become lipophobic and precipitate from the oil. Nonhydratable phospholipids have to be converted to hydratable ones, usually by acidulation followed by neutralization. Traditionally, this conversion was done with acids that are sufficiently strong to hydrate phospholipids without hydrolyzing the triglycerides. Many different acids have been proposed, ranging from hydrochloric and citric acid (Hvolby 1971, Paulitz 1983), nitric, sulfuric and phosphoric acid (Paul 1968) and sulfurous acid (Merat 1955) to oxalic acid (Ohlson and Svensson 1976), which had been proposed for easier effluent treatment. A variety of other acids have also been tested. At present, citric and phosphoric acid are used almost exclusively. Even acid-treated PA and PE still have low hydration rates that may be increased by the addition of alkaline sodium solution. Acids are also often used to increase efficiency (better hydration); in this case, it is again citric and phosphoric acid that are recommended. If sulfuric acid is used instead, the oil can be used for non-food purposes without further refining. Some oils can also be heat-degummed. They are heated to 240-280°C and the gums precipitate. This is called “breaking” the oil. More recently enzymes, in this case phospholipase-A,, have been used to convert nonhydratable phosphatides. The enzyme attacks the 2-ester bond and splits off the relevant fatty acid, thereby easing hydration. The enzyme is sensitive toward heat and can therefore be destroyed by heating the oil. The reaction is best carried out at 6 0 ° C which is the temperature with the highest enzyme activity.
-
5.2.5.3 The Degumming Process. Until the 1920s, soybeans were extracted with a mixture of benzene and alcohol to produce lecithin. Bollmann then showed the way to produce lecithin from extracted soybean oil. Soybean oil contains 1-3% phosphatides. After being hydrated with water, they become lipophobic and precipitate from the oil. The precipitate can easily be separated from the oil by centrifugation because of its higher specific weight. In the past, degumming was a batch process, whereas today it is almost completely done continuously in the big oil mills. The lecithin sludge (also called break material) that is separated via centrifugation weighs about twice as much as the lecithin it contains. Pardun (1979) analyzed a water
Fats and Oils Handbook
430 Water degummlng WDG
T2%?1°'
(for saybans onb, w 5.2.1.3 3)
Crud? oil
Safinco degummlng Van de Moortde D.
Awn soybean oil
Dynamic m i n g -45 mh
3 0 6 0 min
2-3mln
Mino
Water degummed oil (P< 2ooppm)
Degummed ALCON oil
(P< bpm)
UF degummed oil (P < 5 r n )
Fig. 5.74. Simplified flow charts of different common degumming processes (1 = or water degumrned oil; p. = patent and/or process). content of 35-50% and found 15% soybean oil and soy fatty acids and 35-50% crude phosphatides. To recover lecithin from the sludge, it must be dried quickly to prevent further hydrolysis. Usually thin-film evaporation is chosen because a relatively moderate temperature of 80-95°C is sufficient at 70-400 hPa to evaporate the water within 1-2 min. Thus, the lecithin is protected against quality deterioration. If batch drying is applied, a temperature of 60-80°C is necessary at 25-75 hPa for 3-4 h. 5.2.5.4 Silicate Degumming. A new way to remove phosphatides and metals from oils and fats is the application of silicates (see, for example, Welsh and Bogdanor 1986). They reported several trials that yielded good results. The silicate is mixed with the oil at 70-100°C; the mixture is agitated for -30 min and then filtered. A single use of silicate replaces bleaching earth, filter aid and citric acid and is reported to be more efficient than bleaching earth at a lower rate of consumption. Table 5.26 shows a comparison based on the trials of the manufacturer.
5.2.6 New Processes There is ongoing effort to find new ways to extract oils and fats. The primary goal in this search is to eliminate the solvents currently in use. Solvents are not present in the refined oil, not even in minute traces. An increasing number of consumer groups, however, oppose the fact that they are applied at all. One way to avoid the
Extraction of Vegetable Oils Superdegumming Unilever p.
43 1 TOPd
umming
Van de%xtele p.
Crude oil '
h 70.C
CN& oil '
Crude oil ' Heating
<<< CMC acid Dynamie mhing
-
10 min
25-3O'C
Stntic mhing
I
-
65'C
Holdinp
2.3 h
I
- 60%
Mating
I Sepantiw
Superdegummed oil (P < 3oppm)
Unidegumming Unilever p,
Dry degumming
Superdegummed oil
Water degummed oil
Enzymaa deg. Lurgi p. Water degummed oil (P < 2 F m )
(P < 30ppm)
Mating <<
Unidegummed oil (P < 8PFW
Degummed bleached oil (to Woriration)
Fig. 5.74. (Continued).
use of solvents is to apply processes resembling those used in olive and palm oil extraction. At present, however, these processes have yields that are not economically sound. A possible solution to the problem might be to sell the higher fat content meal at higher prices or to use the solvent-extracted oil for technical purposes. Another novel process is supercritical CO, extraction. Sufficient solubility of the
Fats and Oils Handbook
432
stirrirg
w m i n
e Ladthin 81-
3540% Watsr 1-2 min, 70-400 hPa, t K lc 1%
Drying
Film evaporator 80.%'C,
cwling
c SO'C (avoid8 darkening)
2030'C (storage alabilily over many months)
I
Crude lecithin
Crude soybean oil (dogummod, 0250.5% water)
Fig. 5.75. Acid degumming process. oil in carbon dioxide can be achieved only at very high pressures, and on a large scale, the resulting problems have not yet been solved. There will be further development in that direction.
5.2.6.7 High Pressure CO, Extraction. High pressure CO, extraction is applied mainly in decaffeination of coffee and tea, debittering of hop as well as for the extraction of hop and other natural flavors. The solubility of these components in supercritical CO, is much lower than that of oils and fats; however, their amount, as trace components, is also much lower (Table 5.27). The process can also be applied for the extraction of oils and fats from seeds. It has the principal advantage TABLE 5.26 Degumming Properties of Silicates and Bleaching Earths Propetty
Silicate
Suiface area (m*/g) Volume of pores (mug) (% at 95OOC) Volatiles pH (15% aqueous suspension) Bulk density (kg/m)
800 1
65 4.5
500
Bleaching earth 200 0.2 10 4
560
433
Extraction of Vegetable Oils
TABLE 5.27 Solubility of Different Substances i n Supercritical C 0 2 at 300 bard Extracted substance Rapeseed oil Vani Ilin Arnica extract Hop extract Nicotine Caffeine
Solubility (gkg solvent) 68 45 27 19 15 4.5
aSource: Beutler (1988).
that solvent removal is much easier; residual CO, is not at all critical because it is a natural component in the air and in food. The high investment cost, the difficulty in applying the process continuously and the high energy requirements are disadvantages of this process. 5.2.6.7.7 The theory of supercritical liquid extraction. If gases are compressed and become supercritical, their properties change and some of their parameters become similar to to those of liquids (Table 5.28). The density of supercritical fluids can be varied by changing the temperature and pressure, thus adjusted to the needs for extraction of certain seeds. The viscosity of supercritical fluids is much lower than that of ordinary fluids, offering great advantages. Sievers (1985 and 1986), Sievers and Eggers (1990) and Penninger (1985) discussed the characteristics of liquid C 0 2 as an extraction solvent. Above 31"C, CO, is in the supercritical state in which a distinction can no longer be made between the liquid and gaseous phases. It has gained the properties of a solvent. The most important parameter for oil extraction with CO,, of course, is the solubility of the oil. This solubility can be calculated only very inaccurately. To obtain reliable information, single-phase equilibria have to be measured. Figure 5.76 shows a comparison of calculated (Eggers 1985) and measured (Quirin 1982) data for the solubility of soybean oil in C02. The solubility, at first sight, is proportional to the pressure. In reality, it is proportional to the solvent density (usually proportional to the pressure) unless chemical interactions dominate. The aim, TABLE 5.28 Physical Data of Liquids, Gases and Supercritical Gases
Liauids
Supercritical gases
Gases
Density (gcrn3) 0.6-1 .O Dynamic viscosity (kgrns) Diffusion coefficient (crn2/s) 0.00001
0.24.95 -0.0001 0.00014.001
-0.001 -0.0001 0.1
Hexane Supercritical C 0 2 (60°C 1 bar) (50°C 300 bar) 0.000233
0.000008620
Fats and Oils Handbook
434
Solubility [% m/m] 10
I 80°C
lines: calculated 8
points: measured
6 4
2 0
0
100
200
300 400 500 Pressure [bar]
600
700
800
Fig. 5.76. Solubility of soybean oil in supercritical CO, (calculated data from Eggers
1985; experimental data from Quirin 1982). therefore, is normally to reach as high pressures as possible (Brunner 1983, Eggers and Stein 1984, Eggers et al. 1986). If 2, 4 or 6% hexane is added to the C02, the solubility of a fatty alcoholhydrocarbon mixture is increased from the initial value of 10, 12 and 15 mg/g, respectively, to as much as 45 mg/g. With the addition of other gases such as N2,the selectivity of the extraction can be increased. 5.6.7.2 Process and plants for high pressure extraction. Critical fluid extraction follows a relatively simple processing pattern. Because of the extreme pressure, however, it is technically sophisticated (Fig. 5.77). For the extraction of coffee and hops, only discontinuous plants are used. In these plants, high pressure can be managed easily because the extraction goods are not fed to or released from the extraction chamber via valves. Plants for batch extraction of oilseeds would be similarly designed. In principle, such plants need two pressure vessels, one for extraction and one to separate the extract. The reduced or pelleted extraction goods are fed to vessel I and the air in the plant is replaced by carbon dioxide. Carbon dioxide then flows from the high pressure storage vessel into the plant until pressure and temperature are equilibrated between them. The desired C 0 2 pressure is then reached by a pump, and the extraction temperature is maintained by heat exchangers that are able to cool or heat. Before the operation begins, the separator is also filled with C 0 2 and the pressure there is adjusted. For the extraction, the extraction solvent (supercritical CO,) is pumped through the heat exchanger. In the extraction vessel, it is loaded with extract that precipitates from the solution after pressure reduction in the separator. The then
Extraction of Vegetable Oils
I
.1
Expeller-Cake
+
-+
c
435
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It
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+ e
>>>CCh>>>
+
1
1
e
gaseous CO, is sucked off, liquefied by a compressor and fed back into the system by a high-pressure pump. In the heat exchanger, it is brought back to the processing temperature. After the extraction is completed, C 0 2 is pumped back into the storage vessel, and the extracted good and the extract are removed from the extraction and the separation vessel, respectively. The pressures allowing for satisfactory solubility of oil in CO, (-600 bar) are much higher than those applied in coffee extraction. The reason is that caffeine is a trace component in coffee, whereas oiYfat are main components in oilseeds. Also, the mass flow in oil mills is much larger than in specialty coffee roasting and hop extraction. At present, feeding and emptying times are prohibitively high in oil extraction. Therefore, the process can succeed only if it can be run continuously. A possible plant layout would combine pressing and C 0 2 extraction (Fig. 5.78). The seed is fed (1) and press-extracted in a screw press. The press oil leaves at (3). The expelling pressure of the press must be higher than the pressure in the extraction vessel (4).The fully extracted meal is then removed with a second screw press. 5.2.6.7.3 Examples for supercritical fluid extraction of fats. To date, only oils and fats that are marketed in small quantities and serve special purposes, mainly in the cosmetics and the pharmaceutical industry, are considered for supercritical fluid extraction. Quirin et al. (1987) gave some examples. Figure 5.79 shows the efficiency of C 0 2 extraction of corn oil. It is expressed as the percentage of C 0 2 -
Fats and Oils Handbook
436
I
6 1
3
-
-
I
Fig. 5.78. Plant for expelling and critical CO, extraction of oilseed (courtesy of Krupp Maschinentechnik GmbH, Hamburg).
Extraction yield 100
1% of hexme extract]
0.9% saturatlon-
0 ~ 0
~ 10
+
~ 20
~
~ 30
~ 40
~ 50
Time [min]
Fig. 5.79. Extraction yield of supercritical CO, extraction of corn.
"
~
Extraction of Vegetable Oils
43 7
extractable oil compared with solvent-extractable oil. The curve first rises steadily and then, close to 90%, asymptotically approaches the value for solvent extraction. The quicker increase of I compared with I1 is due to the saturation adsorption which is only half as large. The corn oil extracted by Quirin was lighter than hexane-extracted oil; the phospholipid content was only 1% of the amount analyzed in hexane-extracted oil. Currently, the best examples of C 0 2 extraction come from the specialties industry. Linseed, sold as a laxative, is extracted because it swells better without oil (Stahl et al. 1986). If it is hexane extracted, the meal is subject to more stress and thus loses a substantial part of its desired properties. Evening primrose oil is C02-extracted because it is the sole source for ylinolenic acid (all-cis-6,9,12-linolenic acid). The oil does not withstand the thermal stress of refining. Supercritical extraction delivers an oil that does not require refining. The extraction is carried out at 300-800 bar. The first 90% of the batches are light yellow, the latter, darker and turbid from waxes. Jojoba oil also needs no refining if it is C 0 2 extracted. In general, extraction with supercritical COz offers the extraction of seeds without carryover of undesirable lipids and other components. Usually, such oils have a light color and do not need refining. These advantages might compensate for the lower yield compared with hexane extraction. Since the 1980s, trials have been conducted with all common oilseeds. Goodrum and Kligo (1987), for example, described the extraction of peanuts. A detailed description of the process was given by Stahl ef al. (1986). 5.2.6.1.4 Comparison with traditional processes. CQ extraction is superior to conventional technologies because it does not require solvents, at least no solvents regarded as unnatural. Considering the rising environmental consciousness, there may be considerable psychological advantages from expending the additional investment. If supercritical carbon dioxide extraction were to make refining obsolete, the total investment would be less. Today one cannot yet estimate whether the running cost would be acceptable. 5.2.6.2 Liquid Propane Extraction. In the 1940s, liquid propane extraction was med as an alternative to hexane. These trials were not successful because propane had no competitive advantages compared with hexane. On the contrary, w o w under high pressure required great technical effort. From these trials, however, patents for crude oil purification were derived. 5.2.6.3 Two-Phase Extraction with Polar and Nonpolar Solvents. Two-phase extraction has the advantage of lowering the glucosinolate content in rape meal. Because all plant-breeding efforts were headed in the same direction, this method was interesting only for a transition period. It may be valid, however, for other oilseeds that contain undesirable components. The process is described in Figwe 5.80.
Fats and Oils Handbook
438
Rapeseed MethanoUAmmonia >>>
-+
I Hexane >>>
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2 min, 2000 min-l
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15 min
I
-+
2 min, 2000 min
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I
I
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-+
+ -+ 11
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-+
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+
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I Methanohi phase Solvent evaporation
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'n' tA/CondensatlonIt -
5.2.7 Energy Consumption The energy consumption for oil and fat extraction depends on the seed species. For seed oils, it is on a comparable order of magnitude. Energy consumption depends on the processing route chosen more than on the seed. Weber (1978) gives a comparison between combined press and solvent extraction and direct solvent extraction. The trials were conducted with dehulled sunflower seed (8% hull content). The sunflower flakes were agglomerated for better percolation (Table 5.29). If one compares direct solvent extraction with prepressing and subsequent extraction, the simpler factory layout must be considered. This goes hand in hand with lower investment costs, i.e., lower depreciation and lower cost for repair and maintenance.
439
Extraction of Vegetable Oils
TABLE 5.29 Comparison of Sunflower Oil Extraction via Different Processing Routesa and Consumptionsb Extractor for MT/d
Extraction Press solvent Direct solvent Electrical energy
(kWh)
Steam Cooling water Solvent Personnel Maintenance
(k@ (m3) (kg) (h)
(US.$)
Estimate based on:
62 2 70 12 2 0.4 . 10
45 41 0 15 2.5 0.2 6
1978 figures
200
600
18 -270 18 1.3
12 -260 18 1.2
1500
2400
9
8 -250 -240 18 18 1.1 1.0
1995 figures
aSource: Weber (1978). bSource: Lurgi (1 995).
Weber (1973) analyzed the energy flow in an oil mill with an annexed refinery. The calculations were for soybean extraction and refining, based on beans with 18% oil content and 12%humidity. Approximately half of the steam was consumed for seed pretreatment and extraction, one third for full refining and one sixth for meal desolventizing. The rest was used for miscellaneous activities. The bulk, i.e., two thirds of the electrical energy was also used for seed pretreatment and extraction. One sixth each is for refining and drying the oil. The same applies for water consumption, where -60% was consumed in seed pretreatment and extraction. Today, this figure is lower because an increasing number of plants with water circulation have since been built. 5.2.8 Turnkey Factory
Weber (1987) gave the following investment for a direct extraction soybean oil mill (corrected by the author to 1997 by an average of 3% inflation per year): total (without land) 35.0 million U.S. $ silos 15.5 million U.S. $ buildings, utilities 9.0 million U.S. $ Such a plant has a throughput of loo0 todd of soybeans (12% water content, 18% oil content and 15% broken beans). The running costs are as follows: total 26.0 U.S. $ N T energy 16.3 U.S. $/MT water 1.O U.S. $ N T hexane 0.4 U.S. $/MT labor 5.0 U.S. $ N T As a comparison, it should be mentioned that this is a medium-sized plant because large plants today are able to process 4OOO MT/d. Weber estimated the area required to be 40,OOO m2 of which 2500 m2 are needed for the extraction plant itself.
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Fats and Oils Handbook
5.3 References Beal, L. (1987)Valorisation du Tournesol par le Dkjcorticage de la Graine, Rev. Fr. Corps Gras 34, 139-40. Bernardini, E.,(1985) Oilseeds, Oils and Fats, Publishing House B.E.Oi1, Rome. Beutler, H.J., Lenhard, U., and Llejrken, F., (1988) Erfahrungen mit der C02Hochdruckextraktion auf dem Gebiet der Fettextraktion, Fette, Seifen, Anstrichmittel 90,550-553. Bollmann, H., (1919) Deutsche Patente 322 446; (1920) 303 846. Boucher, D.F., Brier, J.C., and Osburn, J.O., (1942) Extraction of Oil from Porous Solid, Trans. Am. Inst. Chem. Eng. 38, 967-993. Bredeson D.K., (1983) Mechanical Oil Extraction, J. Am. Oil Chem. SOC.60, 163A. Brunner, G., (1983) Selectivity of Supercritical Compounds and Entrainers with Respect to Model Substances, Fluid Phase Equilibria 10, 289-298. Buhr N., (1990) Mechanical Pressing, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 43-48, American Oil Chemists’ Society, Champaign, IL. Coats, H.B., and Wingard, M.R., (1950) Solvent Extraction 111, The Effect of Particle Size on Extraction Rate, J. Am. Oil Chem. SOC.27, 93-96. Deublein D., (1988) Zerkleinerungsmaschinen f i r die Olsaatenaufbereitung, Fette, Seifen, Anstrichmittel 90, 554-560. DFG, Mitteilung I1 der Fremdstoffkommission der Deutschen Forschungsgemeinschaft vom 10. August 1964. DFG, Gewinnung von Fetten und Olen aus pflanzlichen Rohstoffen durch Extraktion, Gemeinschaftsarbeit der, Fette Seifen Anstrichmittel 77, 373, (1975); 78, 217, (1976); 78,415, (1976). Eggers, R., (1985) High Pressure Extraction of Oil Seeds, J. Am. Oil Chem. SOC.62, 1222-1230. Eggers, R., Hagen R., and Sievers U., (1986) Zum Stand der kontinuierlichen Extraktion von Feststoffen mit uberkritischen Gasen, Fette, Seifen, Anstrichmittel 88, 344-35 1. Eggers, R., and Stein, W., (1984a) Moglichkeiten der Bearbeitung von Olsaaten n i t uberkritischen Gasen, Tech. Mitt. Krupp, Werksberichte I , 42. Eggers, R., and Stein, W., (1984b) Hochdruck-Extraktion von Olsaaten, Fette, Seifen, Anstrichmittel 10, 86. EX-Technik, Extraktionstechnik-Gesellschaft f u r Anlagenbau mbH, Hamburg, Verfahrenstechnik-Olsaatenverarbeitung. EX-Technik, (1968) Ein neues Verfahren zur Entbenzinierung von Schroten unter Erhaltung der Wasserloslichkeit des Proteins, Vorttrag DGF-Tagung, Munster. EX-Technik, Fest-Fliissig-Extraktionrnit dern Karussell Extrakteur, W. Kehse aus Chemiker Zeitung. EX-Technik, Lieferprogramm Olsaatenverarbeitung. EX-Technik, Technical information. EX-Technik, Verfahren und Vorrichtung zur Gewinnung von Olsaatenschroten mit differenziertem Anteil an wasserloslichen Proteinen, K. Weber, Vortrag DGF-Tagung. EX-Technik, (1982) Vorentbenzinierung von Extraktionsschrot, K . Weber, Vortrag DGFTagung, Wiesbaden.
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441
Fan, H.P., Morris, J.C., and Wakeham, H., (1948) Diffusion Phenomena in Solvent Extraction of Peanut Oil: Effect of Cellular Structure, Ind. Eng. Chem. 40, 195-199. Farnsworth, J.T., Johnson, J.P., Wagner, L.R., Watkins, L.R., and Lusas, E.W., (1986) Enhancing Direct Solvent Extraction of Oilseeds by Extrusion Preparation, Oil Mill Gazetteer 91, 30. Fehrenfeld B., (1977) Versuche im Technikum d e r Fa. Krupp, Information der Krupp Maschinentechnik GmbH. di Giovacchino, L., (1989) Olive Processing Systems. Separation of the Oil from the Must, Olivae 4,21. di Giovacchino, L., (1996) Olive Harvesting and Olive Oil Extraction, in Olive Oil, Chemistry and Technology, (Boskou, D., ed.), pp. 12-52, AOCS Press, Champaign, IL. Goodrum, J.W., and Kilgo, M.B., (1987) Peanut Extraction Using Compressed C02, Energy in Agriculture 6, 265-27 1 , Hammond, E.G., Johnson, L.A., and Murphy, P.A., (1993) Soya Beans, Properties and Analysis, in Encyclopaedia of Food Science, Food Technology and Nutrition, Academic Press, London. Hirsinger, F., and Knaut, J., (1994) okobilanzierung von nachwachsenden Rohstoffen am Beispiel Palmol, Fat Sci. Technol. 96, 333-340. Hudson, B.J.F., (1984) Evening Primrose Oil and Seed, J. Am. Oil Chem. SOC.61,540. Homann, T., Knuth, M., Miksche, K.D., and Stein, W., (1978) Die mechanische FestFliissig-Trennung mittels Seiherschneckenpressen in der Speiseolindustrie, Fette, Seifen, Anstrichmittel 80, 146-149. Hvolby, A,, (1971) Removal of Nonhydratable Phospholipids from Soybean Oil, J. Am. Oil Chem. SOC.48,503. Karnofksy, G., (1949) The Theory of Solvent Extraction, J. Amer. Oil Chem. SOC.51, 564. Kehse, W., (1986) Fest-Fliissig-Extraktion mit dem Karussell-Extrakteur, Khemiker&itung/Chemische ApparaturNerfahrenstechnik 2000. Kemper, T.G., Benefits in Oilseed Processing Using the Extruder, Speech delivered at the AOCS Conference, May 5, 1989, Cincinnati, OH; Technical Information of French Oil Machinery Co., Piqua, OH. King, C.O., Katz, D.L., and Brier, J.C., (1944) The Solvent Extraction of Soybean Flakes, Trans. Am. Inst. Chem. Engrs. 40,533. Knuth, M., Miksche, K.D., and Stein, W., (1977) Speiseolgewinnung aus pflanzlichen Rohstoffen durch Abpressen, Seife, Ole, Fette, Wachse 103, 385-388. Kock, M., (1981) Practical Experience with a Process f o r Entyme Deactivation of Soybean Flakes Before Extraction and Its Influence on the Oil Quality, American Soybean Association Congress, Antwerp. Krupp, Plant and Machinery f o r the Oil Milling Industry, Technical information, Krupp Maschinentechnik GmbH, Hamburg. Krupp, Krupp Maschinentechnik, Technical information, Hamburg. Krupp, Eisenabscheider Typ MT, Technical information, Hamburg. Krupp, Hochdruck-Extraktionsanlagen,Technical information, Hamburg. Krupp, Konditionierapparat Typ TK, Technical information, Hamburg. Krupp, Kopraschneider Typ MR, Technical information, Hamburg. Krupp, Liisungsmittel-Extraktionsanlagen,Hamburg. Krupp, Metallabscheider Typ IMA, Technical information, Hamburg.
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Fats and Oils Handbook
Krupp, Oltrubscheider Typ SK, Typ V, Technical information, Hamburg. Krupp, Plant and Machinery for the Oil Milling Industry, Hamburg. Krupp, Quetschwalzwerk Typ Q600, Technical information, Hamburg. Krupp, Riffelwalnverk Typ R300, Technical information, Hamburg. Krupp, Riihnverksautoklav Typ E, Technical information, Hamburg. Krupp, Schilferbrecher Typ SZR 300, Technical information, Hamburg. Krupp, Schneckenpressen Typ EP, Technical information, Hamburg. Lajara, J., (1990) Solvent Extraction of Oil from Oilseeds: The Real Basics, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 49-55, American Oil Chemists’ Society, Champaign, IL. Lester, B., (1987) New Aspects of Delinting and Decorticating Technology, Oil Mill Gazetteer 92, 18-19. Lurgi, Lurgi Umwelt-und Chemotechnik GmbH, Frankfurt, Technical information. Lurgi, Schnellinformation Kontinuierliche Losungsmittel-Extraktion von Olsaaten. Lurgi, ALCON, Akzo-Lurgi-Conditioning,Second ASA Symposium on Soybean Processing, Antwerp, June 1981. Lurgi, ALCON, Akzo-Lurgi-Conditioning, 36. DGF-Vorttragstagung, Kiel, September 1980. Lusas, E.W., and Wathuis, L.R., (1988) Oilseeds: Extrusion for Solvent Extraction, J. Am. Oil Chem. SOC.65,1109-1 114. Lusas, E.W., (1990) Separation of Fats and Oils by Solvent Extraction: Non-Traditional Methods, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practises, (Erickson, D.R., ed.), pp. 56-78, American Oil Chemists’ Society, Champaign, IL. Martinez Moreno, J.M., Gomez Herrera, A.C., and Jner del Valle, C., (1957) Estudios Fisico Quimicos sobre las Pastas de Aceitunas Molidas IV.Las Gotas de Aceite, Grasas y Aceites 8, 1. Mendoza, J., Gomez, M., and Casado, F., (1990) Technical Evolution of the Different Processes for Olive Oil Extraction, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 341-348, American Oil Chemists’ Society, Champaign, IL. Merat, Editorial No 2, (1955) J. Am. Oil Chem. SOC.78,7. Miller, R.E., Edwards, E.H., and Kohler, G.O., (1979) Pilot Plant Grinding and Pressing of Jojoba Seed, J. Am. Oil Chem. SOC.56,556-558. Montedro, G., and Petruccioli, G., (1974) Trattamenti con Additivi Enzimatici e Detannizzanti alle Paste di Olive Sottoposte a Processi di Estrazione per Pressione Unica e Percalamento: I Effetti sui Redimenti in Olio e su Alconi Parametri Operativi, Riv. Ital. Sost. Grasse 51,378. Naczk, M., Shahidi, F., and Rubin, L., (1988) A New Extraction Process for Rapeseed: A Review, Rev. Fr. Corps Gras 35, 3. van Nieuwenhuyzen, W., (1976) Lecithin Production and Properties, J. Am. Oil Chem. SOC. 53,425427. Ohlson, J.S.R. (1976), Processing Effects on Oil Quality; J. Am. Oil Chem. SOC.53, 299-301. Ohlson, R., and Svensson C., (1976) Comparison of Oxalic Acid and Phosphoric Acid as Degumming Agents for Vegetable Oils, J. Am. Oil Chem. SOC.53,8-11. Ohlson, R., (1992) Modem Processing of Rapeseed, J. Am. Oil Chem. SOC.69, 195-198.
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443
Othmer, D.F., and Agarwal, J.C., (1955) Chem. Eng. Prog. 51,372. Othmer, D.F., and Agraval, J.C., (1955) Extraction of Soybeans, I d . Eng. Chem. 47,372. Othmer, D.F., and Jaatinen, W.A., (1959) Extraction of Soybeans, Ind. Eng. Chem. 51, 543-546. Pardun, H., (1979a) Die Entsliuerung von Pflanzenolen mit Ammoniak, eine umweltfreundliche Raffinationsmethode,Fette, Seifen Anstrichmittel 8,297-302. Pardun, H., (1979b) Die Bedeutung der Pflanzenlecithine fur die Lebensmittelindustrie, Zeitschrijifur Lebensm. 249-255. Paul, (1968) Nahrung 12,429, quoted from Pardun, H.; see above. Paulitz, H., European Patent 122727. Penninger, J.M.L. (ed.) ( 1 9 8 3 , Supercritical Fluid Technology, Elsevier-Verlag, Amsterdam. Penk, G., (1980) Conditioning of Soybean Flakes. Process Technique and Economical Aspects, p. 36, DGF-Vortragstagung, Kiel. Penk, G.,(1985) Praktische Erfahrungen mit dem ALCON-Prozep, Fette, Seifen, Anstrichmittel 87, 499-505. Peter, S., (1983) Stofftrennung mit ijberkritschen Fluiden, Fette, Seifen Anstrichmittel 85, 135-142. Petruccioli, G., (1965) Prove Tecnologiche sul Complesso ‘Sinolea-Pressa’ e sulla Centrifuga Chiarifiatrice Westfalia, Industrie Rarie 7,347. Pollard, E.F., Vix, H.L.E., and Gastrock, E.A., (1945) Solvent Extraction of Cottonseed and Peanut Oils: Boiling Point-Vapor Pressure-Composition Relations for Miscellas of Oil in Hexane, Ind. Eng. Chem. 37, 1022-1026. Quirin, K.W., (1982) Loslichkeitsverhalten von fetten dlen in komprimiertem Kohlendioxid im Druckbereich bis 2600 bar, Fette, Seifen, Anstrichmittel 84, 460-468. Quirin, K.W., Gerard D., and Kraus, J., (1987) Hochdruckextraktion mit Kohlendioxid; Ein schonendes Verfahren zur Gewinnung hochwertiger fetter Ole, Fette, Seifen, Anstrichmittel 89, 139-142. Quirin, K.W., Gerard D., and Kraus, J., (1987) Verdichtete Case zur Extraktion und Ruffination,Springer Verlag, Berlin. Quirin, K.W., Gerard D., and Kraus, J., (1987) Hochdruckextraktion mit KohlendioxidEin schonendes Verfahren zur Gewinnung hochwertiger fetter Ole, Fett Wissenschji Technologie 89, 139-142. Rac, M., (1967) Influence de la Structurecellulaire sur Quelques Proprietes Technologiques de Certaines Matitres Premieres OlCaginuses, Rev. Fr. Corps Gras 14,223. de Ramecourt, B., (1976) Continuous Processing of Palm Fruit, J. Am. Oil Chem. SOC.53, 256258. Reusch, M., ( 1989) Untersuchungen einiger den Besatzanteil einer Olsaat beeinflussender Faktoren sowie des Einflusses des Besatzanteils auf den Raffinationsaufwand und die Olqualitat, Ph.D. Thesis, Technische Universitat, Berlin. Rice, P., and Hamm, W., (1988) Densities of Soybean OiUSolvent Mixtures, J. Am. Oil Chem. SOC.65, 1177. Rubin, L.J., Diosady, L.L., Naczk, M., and Halfani, M., The ALkanol-Ammonia-Treatment of Canola, Can. Inst. Food. Sci. Technol. J. 57, 19. Schepkina, O., Maslob.-Zhir. Delo. 10 (1934) quoted from Norris, G. F.A., (1982) Extraction of Fats and Oils, in Bailey’s Industrial Fats and Oils Products, (Swern, D., ed.), John Wiley & Sons, New York.
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Fats and Oils Handbook
Schneider, F.H., (1979a) Schalung von Rapssaat durch definierte Verformung; Teil I: Untersuchung der Saatanatomie, Fette, Seifen, Anstrichmittel 81, 11-16. Schneider, F.H., (1979b) Schalung von Rapssaat durch definierte Verformung; Teil 11: Untersuchung zum Schalverhalten, Fette, Seijen, Anstrichmittel 81,53-59. Schneider, F.H., and Rass, M., (1997) Trennpressen von geschdter Rapssaat-Zielsetzung und verfahrenstechnische Probleme, F e t a i p i d 99,91-98. Schneider, F.H., and Hutte, U., (1991) Resthexan in Rapsschtroten-zur Entstehung einer Intrazellularen Miscella; Fat Sci. Technol. 93,319. Schoenemann, K., and Voeste, T., (1952) Zur Berechnung von Feststoff-Extraktionsanlagen, Fette und Seijen 7,385-393. Seghers, J.C., (1990) Degurnming-Theory and Practice, World Conference Proceedings, Edible Fats and Oils Processing, pp. 88-93, American Oil Chemists’ Society, Champaign, IL. Sievers, U., Stoffeigenschaften von Kohlendioxid als Losungsmittel fur die HochdruckExtraktion; Chemie-Technik, 54-56, 14 (1985) Sievers, U., (1986) Thermodynamische Eigenschaften von Kohlendioxid-Stoffdaten fur die Hochdruck-Extraktion, Chem. Ing. Tech. 58,220-222. Sievers, U., and Eggers, R., (1990) Energetischer Vergleich einer konventionellen Festmussig-Extraktion mit der Hochdruckextraktion, Chem. Ing. Tech. 62,64-65. Signoret, A., (1988) Le Dtpelliculage des Grains de Colza: Premiers Rtsultats Industriels, Rev. Fr. Corps Gras 35,391-396. SKET, VEB Schwermaschinenbau-Kombinat ‘Emst Thalmann’ Magdeburg, Technische Informationen, Hochleistungsschneckenpressen. de Smet, Extraction de Smet SA, Edegem Belgien, Technische Informationen Solvent Extraction. Smith, AS., and Wechter, F.J., (1950) Vapor Pressure of Hexane Soybean Oil Solution at Low Solvent Concentrations, J. Am. Oil Chem. SOC.27,381-383. Stahl, E., and Quirin, K.-W., (1983) Solubilities of Soybean Oil, Jojoba Oil and Cuticular Wax in Dense Carbon Dioxide, Fette, Seijen, Anstrichmittel 85,458. Stahl, E., Quirin, K.-W., and Carius, W., (1986) Aufschliepn und Aufblaen von pflanzlichem Material; I. Mitteilung: Leinsamen und Hibiscusbluten, Zeitschr. kbensmittelunters. Forsch 182,33-35. Tindale, L.H., and Hill-Haas, S.R., (1976) Current Equipment for Mechanical Oil Extraction, J. Am. Oil Chem. SOC.53, 265-270. Vadke, V.S., and Sosulski, F.W., (1988) Mechanics of Oil Expression from Canola, J. Am. Oil Chem. SOC.65, 1169-1 176. Weber, K., (1972) Ruckgewinnung von Losungsmitteln aus der Abluft, Fette, Seifen, Anstrichmittel 74, 605-608. Weber, K., (1973) Produkt-und Energiestrome in einer Olmuhle und deren Einflup auf die Planung, die Em&hrungsindustrie, pp. 113-1 16. Weber, K., (1974) Entwicklungsstand und Tendenzen in der Fest-Flussig-Extraktion, Maschinenmarkt Heft 80, 88. Weber, K., Betrachtung zur Zweistufen- und Einstufen-Olgewinnung aus Sonnenblumensaat, Vortrag auf der Konferenz Tolbuchin, Bulgaria, October 1978. Weber, K., (1981) Besondere Aspekte bei der Konstruktion von Grop-Extrakteuren, vt >>Velfahrenstechnik<< 15,623-625. Weber, K., (1987) Soybean Oil Extraction Plant, Chapter 34, in Food Factories, (Bartholomai, A., ed.), Verlag Chemie, Weinheim.
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Welsh, W.A., and Bogdanor, J. M., Phosphorus and Trace Metal Removal with a Novel Refining Material, Trisyl, Vortrag, American Oil Chemist’s Society Meeting, Honolulu, May 1986. Westfalia, Westfalia Separator AG, Oelde, Separatoren und Dekanter fur die OlivenolIndustrie, Technical information. Williams, M., and Baer, S., (1965) The Expansion and Extraction of Rice Bran, J. Am. Oil Chem. SOC.42, 151. Wingard, M.R., and Phillips, R.C., (1949) The Determination of the Rate of Extraction of Crude Lipids from Oil Seeds with Solvents, J. Am. Oil Chem. SOC. 26,422426. Wolff, J.P., (1983) Residual Hexane in Meals, J. Am. Oil Chem. SOC. 60, 172.
Chapter 6
Modification of Fats and Oils
As natural products, fats and oils do not always have the properties required for specialized purposes. On the other hand, there may be raw materials that do have the ideal properties required, but are too expensive or exist in limited quantity. Modification of oils and fats offers an adequate solution. The techniques used to modify fats and oils change mainly their physical properties to meet the needs of the specified purpose. These techniques are summarized under the term modification (Fig. 6.1). Modification offers the possibility of changing the properties of oils and fats within wide ranges, thus making them suitable for many uses or for making oils and fats with desirable properties available in sufficient quantities. The following processes (all of which have models existing in nature) offer the possibility of modifying fats and oils: fractionation, winterization, interesterification and hardening. Fractionation and winterization are purely physical processes. Interesterifkation is a physical-chemical process and hardening is a chemical one. In the frst two cases, the fat molecules remain untouched. Only fractions of fats are separated as a result of different melting points or solubility. In interesterification, the building blocks of the fats themselves remain unchanged. However, the fats are recomposed from these identical building blocks. In hardening, hydrogen is added to the double bond(s) of the unsaturated fatty acids. The double bonds are reduced to saturated bonds, whereas the structure of the triglycerides remains unchanged. Most of the modification processes used today would be replaced immediately, if it were possible to economically imitate the enzymatic processes found in nature.
Hardening
Interesteriftcation
OiMat
Fractionation
OiMst
Fat
I
1
Working Up I Hardrd fsffoll
Working up internsto&
Fig. 6.1.
ravoii
Modification processes flow chart. 446
obin
&rin
447
Modification of Fats and Oils,
6.1 Application and Combination of Modification Processes As with most modem technologies, all modification processes of fats and oils were developed following an urgent need. After they had proven their commercial viability, they were then developed further. An example for such a need was the scarcity of fats and oils that occurred at the turn of the last century when the population accumulated in the cities as a consequence of the industrial revolution. Major fats and oils in those days were marine oils with very bad keepability and very bad taste. This problem was solved by the development of the hardening process (6.5). The high cost of cocoa butter triggered the search for a substitute. Here, fractionation (6.2)offered some possibilities. Interesterification (6.4) can ensure uniform finished properties of fats and oils even if the composition of the starting material is subject to wide variations. Winterization (6.3) has had only a limited commercial effect because, in principle, it is a cosmetic process, ensuring that oils stay clear even if stored at refrigerator temperature. Based on this process, other applications were developed, for example, the reduction of the linolenic acid content in soybean oil by slight hardening and winterization to improve stability. Often, modification techniques are combined to yield special fats. Paulicka (1976) gives some examples of such fats. The combination of hardening and interesterification of palm kernel oil, for example, yields a fat with low melting point and quick melting behavior that can be used in dairy-like products provided local legislation permits. If palm kernel oil, palm oil or cottonseed oil are hardened and the mixture is interesterified, high-melting fats are produced that can be used as cocoa butter substitutes, coatings for cookies and fillings for chocolate bars. Table 6.1 shows the solid content of interesterification mixtures of hardened fats. Such TABLE 6.1 Triglyceride Classes of Palm Oil; Variations of Native Oil a n d after Modificationa Share of triglyceride class (YO) Palm oil Native Randomly interesterified Directedly interesterified Dry fractionated olein Dry fractionated stearin Wet fractionated olein Wet fractionated stearin Native Malaysia Native Zaire Native Sumatra a50urces: Klein (1 979)and Duns (1985).
8.1 12.3 31 .O
2 19 1 61
7.9 6.6 10.5
45.8 37.1 17.6 52 45 33 35 49.4 50.1 48.6
42.8 44.9 42.6 40 32 60 2 35.7 37.8 34.0
3.3 5.7 8.8 6 4 6 2 6.8 5.5 6.6
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interesterified hardened fats give better mouth-feel and are therefore more suitable for the above purposes than fats that are only hardened. The combination of hardening and wet fractionation is used to obtain products that are usually derived from shea butter or Borneo tallow. Both fats, at times, are not available in required quantities. Cocoa butter equivalents, for example, can be produced from fractionated hardened soybean or cottonseed oil (Fig. 6.2). Further examples are given later in this chapter. 6.1.1 Summary and Process Overview
Modification techniques offer the possibility of changing the physical and chemical characteristics of oils and fats, thus improving their functional properties. The melting point can be increased by hardening. The benefits of applying this process include the possibility of stabilizing highly unsaturated oils (such as fish oil) that can degrade easily as a result of oxidation. Rearrangement of fatty acids on their glycerol backbone (interesterification)offers the possibility of changing the physical characteristics, especially the crystallization properties of fats and oils. Their building blocks, the fatty acids themselves, remain untouched. Fractionation allows the separation of triglycerides of different melting points or solubility and the gain of one or more stearin or olein fractions from a fat and oil. The three processes can be used isolated or combined processes (Fig. 6.3).
A = Palm kernel oil C = Palm kernel oil, hardened
6 = Palm kernel oil, interesterified D = Paim kernel oil, hardened, interesterified
Fig. 6.2. Solids content of interesterified hardened palm kernel oil.
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Modification of Fats and Oils
CB = Cocoa butter, R = Replacer A = CBR (I.V. = 60.0; M.P. = 39.5”C)
9o
Solids content [%I
21 Fatty acid
27
33
39
Temperature [“C]
Fig. 6.3. Cocoa butter replacers from wet fractionation of hardened soybean and cottonseed oil (after Paulicka 1976).
6.2 Fractionation Oils and fats are a mixture of triacylglycerols, i.e., triple esters of glycerol with different fatty acids. Therefore, fats and oils are not chemically homogenous substances but a mixture of different triglycerides; however, each of these triglycerides has a defined melting point, influencing the physical properties of the others. As a mixture of substances, therefore, oils and fats have no sharp melting point but a melting range. One distinguishes between oils that are liquid at ambient temperature, at least to the eye, and fats that are solid at room temperature. However, even when appearing liquid, oils may contain high amounts of solid compounds with melting points significantly above ambient temperature (Fig. 6.4). Fractionation uses this property of fats, i.e., being a mixture of different substances of the same class. This enables one to separate a fat into fractions that are products of different melting ranges. Theoretically, these ranges can be made very narrow, assuming extremely good separation. In practice, this is usually not necessary. Fractionation is used mainly to improve functionality and/or improve the commercial value, and to produce special products. The oil that is predominantly fractionated is palm oil. Palm oil is especially suitable for this technique because of its composition, i.e, two almost equal parts of saturated and unsaturated fatty acids
Fats and Oils Handbook
450
Solids content
[%I
100 Oil/Fat
80
A Coconut
6 Palm kernel
60
C Rapeseed
D Premier Jus E Lard
F Butter
40
20 0 -20 -10
0
10
20
30
40
50
Temperature [“GI Fig. 6.4.
Solids content of some fats and oils at different temperature.
and even more importantly, higher- and lower-melting triglycerides (see Fig. 4.29) that can very easily be separated into an olein and a stearin fraction. In the tropical home countries of palm oil, -8 million MT were fractionated in 1995. To produce special products such as cocoa butter substitutes, fractionation offers the possibility of obtaining triglycerides of certain melting ranges that exhibit a melting behavior very similar to that of cocoa butter. It is, for example, possible to “cut out” special fractions from raw materials that are much lower in price or are available in large quantities. However, to achieve the properties desired, this can often be achieved only after an earlier hardening or interesterification step. Fractionation is also performed on animal fats. In the U.S. especially, fractionation of lard is popular. After a slight interesterification, shortenings can be obtained that differ very much from the crude material. The same holds true for beef tallow; the olein can be used as soft shortening. Modification of butter fat is not allowed in all countries. It is, for instance, prohibited by law in Germany. In 1987, (Deffense) 200,000 ton of butter fat were fractionated in France, Belgium and Japan, making use of the Tirtiaux-process. Those fractions could then be used for purposes for which butter fat itself is not suitable. As mentioned before, fractionation is a purely physical process. The building blocks of the fats themselves as well as the triglycerides in their configuration remain untouched. Sepmtion is done exclusively by making use of the different melting points of fats or, in wet fractionation, using their different solubilities in suitable solvents. 6.2.0.7 The History of Fractionation. Separating fats into their different triglycerides caused enormous problems for early fat researchers. The technique most
Modification of fats and Oils
45 1
suitable for separating organic substances from each other at that time, fractional distillation, could not be applied. Other methods, such as fractional crystallization also failed because the melting points of the individual compounds are too close to each other and because fats are soluble in oils to a certain degree (see Chapter 2.3.2.6). The curve of the melting points of different mixtures of oils and fats plotted vs. their proportion in a mixture gives a straight line if plotted logarithmically (Fig. 6.5). The simplest fractionation method, described very early in history, is to squeeze out the liquid portion of a fat, which forms droplets embedded in the fat crystals. This method offers a relatively good olein quality; however, larger quantities of olein remain in the stearin, and its separation sharpness is low. To obtain the liquid oil, the fat was wrapped in a woven cloth (e.g., jute bag) and the olein was pressed out. The second method used was to carefully melt out the oil. Fractionation of coconut oil was sometimes the unwanted effect of the commonly practiced old way of transporting coconut oil from Ceylon to Europe. This was also how the possibility and value of fractionation were detected. In those days, the oil was transported in long wooden drums, “Ceylon Pipes,” in liquid form. During very slow cooling while traveling into more moderate, i.e., colder climate and supported by the rolling of the ship, the stearin fraction crystallized and separated. At the time of anival, the stearin was separated and used for covertures (Rossell 1985). Once the scientific investigation of the composition of fats began, it proved to be extremely difficult to separate the mixture of triglyceride that comprised a natural fat into its components. To split the oil into components pure enough to enable
100
10
1
30
40
50
60
40
50
60
70
Temperature (“C) A = Cocoa butterlsoybean oil C = Cottonseed oil, nativelhardened
Fig. 6.5.
B = Soybean oil, nativelhardened D = Peanut oil, nativelhardened
Dependency of the melting point of fat blends on their share (after Oliver and Bailey 1945).
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Fats and Oils Handbook
analysis and determination of the physical data was impossible. This was the prerequisite, however, for the development of a suitable technology for fractionation and for checking the results that were delivered by this technology. Chevreuil(1823), who began to research the composition of fats at the beginning of the 19th century, managed to isolate relatively pure stearic acid. As far as the first pure triglyceride is concerned (tristearin), it took until the time of Duffy (1854), who obtained a tristearin with the melting point 69.7"C after 32 crystallization steps (mutton tallow, solvent ether). This was a great improvement compared with the tristearins that had been isolated earlier with melting points of 6243°C maximum. Today, the commonly accepted melting point for synthetically produced tristearin lies between 72.5 and 73°C. Hilditch (1936) compiled the melting points of triglycerides that could be isolated from natural and hardened fats. The analytical problems, however, lie not only in the separation of the mixture fat but also in the purification of the fractions obtained, which usually contain mono- and diglycerides. The natural product fat has an ever-changing composition and is very difficult to separate into its constituents. This explains why almost all attempts to explain the reaction mechanisms have been done with model substances of oils and fats. 6.2.0.2 The Process and Its Application. The separation sharpness required in fractionation for food production is far lower than that needed for analytical purposes. Therefore, most of the difficulties described above can be ignored. Additionally, today's technologies offer far better possibilities than those available at the time of the first investigations of fats and oils. Following the pattern of refining (see Chapter 7), fractionation can be done with crude oils as well as with neutralized and bleached or with bleached oils. Oleins and stearins that are obtained using fractionation retain the same untreated or pretreated status as the fats that have been used for fractionation. This means that, if crude oils are fractionated, the refining steps have to be performed separately at a later time on both the olein and stearin fractions. Regardless of the apparatus used, the fractionation process can be split into the following four basic steps: melting or dissolution, conditioning, crystallization and separation of olein from stearin. The number of fractionation steps determines the width of the melting ranges that are obtained in the separated fractions. This also allows the separation of triglyceride classes from each other. If palm oil is fractionated (single stage, Klein 1979), a stearin is obtained that is composed of GS3 and GS2U in which S means saturated and U means unsaturated fatty acids (Fig. 6.6). If the fractionation is conducted twice (double stage), the first stage will be at a higher temperature compared with the single-stage example shown in Figure 6.6 (T, > TI). GS3, as the first stearin to crystallize, is then separated exclusively at TII. Then, at TIII(T, > TI,,), an additional second stearin, which is GS2U, can be obtained (Fig. 6.7), leaving behind GSU2 and GU3 in the second olein. If different methods of modification are combined, better results can often be achieved. Random or directed interesterification of palm oil before the fractionation step leads to new triglyceride classes so that subsequent fractionation yields
=
Modification of Fats and Oils
453
Palmoil I
Fractionation
GS,, I GSzU
GSU2, I GU3
Fatty acids: S = saturated, U = unsaturated
Fig. 6.6. Distribution of glyceride types in single-stage fractionation of palm oil.
totally different proportions of the fractions (Table 6.1). The very different relative amounts of GS, and GSzU after interesterification compared with native palm oil lead to very different stearins in two-stage fractionation, which allows the separation of these two stearins from each other. Similar results are possible when hardened fats are used. 6.2.1 The Theory of Fractionation
The above introduction shows that even carefully performed multistage fractionation does not allow sharp separation of fat fractions from each other because interactions in the oil/fat mixtures are extremely complex and effects during crystallization become superimposed. 6.2. I. 7 Phase Diagrams for the Solid and Liquid State. For the most part, the influences can be shown only by using model substances, in this case, model mixtures. To study interactions that triglycerides exert on each other, a hypothetical binary mixture of triglycerides that form a eutectic mixture is used. This model system clearly shows the properties and theoretical processes of fractionation. If a binary system of these substances (triglycerides) A and B is cooled down, mixed crystals MC appear (Fig. 6.8). The upper line representing the saturated solution of A in B, and vice versa, is supplemented by a second lower line. These two enclose the area of supersaturated solutions of A in B and respectively, B in A. Because they are unstable, they separate immediately into mixed crystals and saturated solution. The eutectic point separates two other areas from each other, namely, the mixtures of mixed crystals with Palmoil I
GSiU I
I 0u3 osu2,
Fatty acids: S = saturated, U = urwturated
Fig. 6.7. Distribution of glyceride types in double-stage fractionation of palm oil.
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Fats and Oils Handbook
Fig. 6.8. Phase diagram of a binary mixture.
either the solid phase A or B. The lines between all adjacent areas represent the equilibrium between these areas, i.e., the adjacent phases they represent and the mixtures of these phases. Apart from three definite points t, (melting point of component A), t, (melting point of component B) and tE (eutectic point), the liquid mixtures have a different composition than the mixed crystals that are formed at the same temperature. Depending on the temperature t, the following crystal mixes are obtained: crystals A and mixed crystals MC (te > t >tx, M < E) crystals B and mixed crystals MC (t, > t > tx, M < E) mixed crystals MC ( t = rx, M = E) crystals A and mixed crystals E ( t < tx, M > E) crystals B and mixed crystals E ( t < rx, M > E) In many cases, the components A and B are not able to form a continuous range of mixed crystals. In such cases, a miscibility gap exists in which no mixed crystals of the eutectic type are formed in M, but a mixture of crystals of composition I and I1 (Fig. 6.9). In practice, fats more or less follow the above patterns with some deviation from the theoretical ideal. Nontriglyceride additions that cause an impurity of the system have great influence on the crystallization behavior. They diminish the speed of crystallization and influence the formation of crystal nuclei as well as crystal growth. Mixtures of two such substances A and B cannot be separated into the pure components by single-stage (cooling) crystallization. A sequence or cascade of
Modification of Fats and Oils
Fig. 6.9.
455
Phase diagram of a binary mixture with miscibility gap.
cooling (crystallization) and heating (melting) steps is necessary. One hundred percent purity can be achieved only by an infinite number of such steps. The principle of such a separation is represented in Figure 6.10, which illustrates a hypothetical two-component diagram. Following the diagram, the first step Temperature T (“K) Tx
cx
T2
r
53
100
Fig. 6.10.
Phase diagram of two triglycerides with eutectic point (after Bailey 1950).
Fats and Oils Handbook
456
is the crystallization of stearin S , crystals in the olein 0, liquid at the temperature T, from an initial melt of A and B (composition C,). The crystals S1 still contain some portion of A (as represented in the diagram). If stearin S , with the composition C2 is melted and brought to temperature T2, a second olein O2 and stearin S 2 are obtained. Point S , is closer to B, which implies that the purity of S2 is higher than that of S , . If continued via T2 with stearin S2, composition C3, and so forth to Tx,the pure component B can be obtained in an infinite number of steps. Figure 6.11 shows two binary systems that are formed from mixtures of two single-acid triglycerides. It can be seen that a eutectic point exists for the system tristearate/tripalmitate (-----), whereas the system tripalmitate/trilaureate (-) possesses a miscibility gap. If palm oil and palm kernel oil are mixed, instead of model pure substances, a system of natural oils is created that has a minimum of solids at room temperature for a palm oil concentration of 60%. At a palm oil concentration of 20%, this system has its lowest melting point (Fig. 6.12).
6.2.7.1 The Fractionation Tree. To separate mixtures of different substances, the scheme of the fractionation tree can be applied theoretically (Fig. 6.13). The process works by the repeated fractionation of the oleins (0)and stearins ( S ) of the parent generation of fractions. The neighboring stearins and oleins are combined (OS, SO) and also fractionated again. This process is repeated. For the separation into x fractions x - 1 stages are needed and i=x-1
C i fractionations have to be canied out
i=l
Temperature ["C]
i
75
. . . . . . . . . .
. . . . . . . . .
- - A = Stearate
B = Palmitate -A
= Palmitate
B = Laureate
0/100 20180 40160 60140 80120 Ratio in mtxture (NB)
10010
Fig. 6.1 1. Binary systems of single acid triglycerides.
Modification of Fats and Oils
Solids content [%I
457
Melting point ["C] 36
60
Solids at
4s-
-33
10'C v
30
-30
-
-27
-A-
.
15 -
....*-.._. * - ......... ....
A
20'C
30'C
3S'C ..@..
..-*-.-
This scheme enables good separation and yields high-purity end products. However, following this process is far too costly for the fractionation of edible fats. The aim here is not to produce pure fractions but to obtain end products with a specified functionality. Therefore, the method of limited separation is used as shown in Figure 6.14. This figure also shows a theoretical model because fractionaFat to be fractionated
I
S = Stemfin
0 = Obin
*?, S2
X
01
SY
03
X
#! y! F! $! f2y so + 0s
sso + S(SoC0s)
S7 I
O
S
'
qsoos)+ 00s
010
I
Fig. 6.13. Fractionation scheme for fractionation with high selectivity.
Fats and Oils Handbook
458
Fat to be fractionated
I*
11
SI
-,,
S = Stearin 0 = Olein
01
I Fig. 6.14.
Fractionation scheme for fats and oils.
tion is conducted in this way only in case relatively pure specialties have to be produced. The olein 0, of a previous stage is always combined with the Olein Ox+lthat originates from fractionating S,. This mix is again fractionated. The temperatures of fractionations 1 and 2, of 3 and 4 and so forth are equal. Products A, B, C, . . . are obtained and, at the end, a product that comprises the combined olein of the last and next to last fractionation stage. Fractionation is normally conducted in single or double stage only. This is reflected in Figures 6.13 and 6.14 by the limiting line x------x. For typical standard applications, only stearin I and olein I are separated. Then, in a second stage, without recombination, one of these fractions (rarely both) is fractionated again (Fig. 6.15). These principles do not change if dry or Lanza fractionation from the melt or wet fractionation from a solution is performed.
6.2.7.3 influencing Crystallization. Fractionation from a melt requires the following steps: complete melting, cooling for nucleus formation (Chapter 6.2.1.2.l) , transition into the area of crystal growth (Chapter 6.2.1.2.2)and separation of olein and stearin (Chapter 6.2.2). There are different ways of influencing mass crystallization (Fig. 6.16). The crystallization method can be chosen (either from the melt or from the solution), and the individual stages of the crystallization can be influ-
459
Modification of Fats and Oils
-
Fat to be fractionated
,
tn
Ftadiation S T I II
,
Frndknation O b y l 111
Obin O l S m
Stearin Si-Sn
,
t,
Olein OI-Om
Seatin S A i
Fig. 6.15. Scheme of fats fractionation.
enced. The separation operation itself follows the usual processing and influences the end products by the amount of olein that remains in the stearin. To judge the separation sharpness, the separation curve can be determined. This separation curve is a graph that shows the olein yield actually achieved vs. the olein yield that is theoretically possible. The theoretical amount of olein in such graphs is usually represented by a characteristic parameter of the oil, e.g., the iodine value. If the Liquid singb phase system Solution
I
Starting material
M ~ M
I
supersaturated or s u p e m b d system
Unstable (crystellking)
system
Stable (qstalliied) system
First transition prcdud
second transition produd
End prcduds
Separation
~ i6.1~ 6. .M~~~ of oils and fats (after Sattler 1977).
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Fats and Oils Handbook
iodine value is plotted against the olein yield, the amount of olein obtained (represented by the iodine value) can be compared with the theoretical value. The graph for palm oil starts with an iodine value IV = 53, which is an average value for palm oil. The unprocessed oil is represented by a 100% olein yield. Increasing iodine values in the olein fraction are caused by separation of an increasing amount of saturated or partly saturated triglycerides and thus stearins so that the obtainable olein yield decreases. Curve (A) represents the theoretical olein fraction. which can be calculated from the iodine values obtained. Area (B) represents the yield that can be obtained by single-stage dry fractionation (6.2.2.1). The areas for Lanza (6.2.2.2) and wet fractionation (6.2.2.3) lie between A and B (Fig. 6.17). The fractionation success can be determined by calculating the ratio of the olein yield obtained and the theoretical maximal yield. This is the so-called separation factor. The most important conditions for optimal crystallization are: Stable crystal formation that can be influenced, Crystal growth that can be influenced, Heat transfer that occurs as quickly as possible. Fulfilling these requirements leads to crystals that combine filterability with minimum olein entrapment. 6.2.7.4 Crystallization. Crystallization is a process that is considerably more complex than melting in terms of the possibilities of influencing it and its course. Crystallization begins when a melt or a solution reaches an unstable condition. This unstable condition can be reached by supercooling or by partial removal of the solvent. The driving force for crystallization is that the system is beyond its equilibrium, and there is a strong irresistible drive to regain the equilibrium, which
Fig. 6.1 7. Separation curve for palm oil fractionation (after Stover et al. 1983).
46 1
Modification of Fats and Oils
is the nature of all processes. Thus, components crystallize as long as the equilibrium is out of balance. Crystal growth (see Chapter 6.2.1.4.2) begins with particles and crystallization nuclei; these may consist of the crystallization substance itself or of foreign material, When crystallization nuclei are seeded into the solution, crystallization takes place more quickly. If the melt is subcooled, i.e., if it is far outside its equilibrium, crystallization can occur like an explosion. Tammann (1932) was the first to research the relationship between crystal formation and crystal growth (see Chapter 6.2.1.4.1 and Fig. 6.18). It is important to steer nucleation in such a way that not too many nuclei are built because this would lead to too small crystals. If the temperature is regulated in an optimal fashion, crystal nuclei of high-melting triglycerides of the fat that build the seeds for crystal growth of the lower triglycerides are formed. To activate this process, moderate cooling rates are necessary and the mixture must be well stirred. Because the heat of crystallization is released, the solution must be sufficiently agitated to avoid local overheating and subsequent melting of the crystals. Optimal agitation is also important to ensure effective heat transfer on the cooled surfaces of the crystallization vessel. Mixing also ensures that, given the relatively high viscosity of the melt, enough material that can crystallize is transferred to crystals or crystal seeds. In the following, the basics of crystallization are summarized briefly. Detailed information on crystallization can be found in Tamman (1903), Matz (1969), McCabe and Stevens (195 1) and in Ullmann’s Encyclopedia of Technical Chemistry as well as in Perry and Chilton (1973) and Lysjanski et al. (1983).
6.2.7.4.7Nucleation. The formation of crystal nuclei in supersaturated solutions has been investigated mainly by Tammann (1903), who described it for different
’
- Viscosity
- Nucleation - - Crystallization
T-150
T- 100
T-50
T
Temperature [K]
Fig. 6.18. Dependency of nucleation rate, crystallization rate and viscosity on the temperature (after Organikum 1974).
Fats and Oils Handbook
462
I
Nucki fom\rtlon
Fig. 6.19.
I
Means of nucleation.
substances. Crystal nuclei can be formed just by themselves (primary nucleus formation) or by external influences (secondary nucleus formation, see Fig. 6.19). There is a maximum nucleus formation rate that is specific for every compound. This maximum is dependent on temperature (Fig. 6.20a). Following Tammann’s rule, the maximum nucleus formation lies -100 K and the maximal crystallization speed 20-50 K below the melting temperature. Similar curves can be obtained for the rate of nucleus formation of triglycerides, e.g., for trilaurin. The two curves for the p- and P’-modification (Fig. 6.20b) were experimentally determined. That for the a-form was obtained theoretically. As could be expected, the sequence in which crystals from the melt are built moves from the thermodynamically most unstable to the most stable form (Fig. 6.21a). Becker and Doring (1935) found an exponential dependency on the degree of supersaturation of the solution. Excessive rates of nucleus formation can thus be avoided by keeping supercooling and, consequently, supersaturation low. Ravich et al. (1946) showed nucleus formation in its relative course (Fig. 6.21b), because it could not be measured absolutely. Nucleus formation is superimposed by the transition of crystals from a more unstable to a more stable modification. The p+P’ transformation rate RT is represented by the dotted line. Crystal nuclei are intermediate structures on their way from an amorphous (unorganized) state to a crystallized (organized) one (Fischer et al. 1948, Frenkel 1947); the entropy of the system decreases. Crystal growth, however, is not a step toward a more organized state; it is the addition of molecules to an already wellorganized crystal surface (Ubbelohde 1937). Nuclei are spontaneously formed and can also disappear spontaneously. For a nucleus to grow to the size of a crystal, it must reach the size of a “critical nucleus.” Its size is determined by the temperature and the deviation of the state of the meltholution state from equilibrium. If a nucleus does not reach that size, it disappears again. Critical nuclei have a size between 0.1 and 1.0 pm (Mullin 1972). Bailey estimated that critical nuclei of triglycerides consist of as few as four to eight molecules. Van Putte and Bakker (1987) studied the nucleus formation of v-crystals of a palm oil fraction that consisted of only fully saturated triglycerides (8.8% of the initial oil). Figure 6.21 shows that a strong temperature dependency exists that is expressed not only in the induction period but also in the formation time of the
463
Modification of Fats and Oils
Number of nuclei / cm3
A
350 300
250
.................................................
200
..................................................
150
..................................................
100
.....................................
Glycerol
Piperine
50 0 -80
0
-40
Temperature
60
40
[“C]
Nucleation [nuclei/time]
B
.....................
* D’-Crystals
.....................
.....
.....................
.....
13 -Crystals
* a -Crystals +.RT = D --> 8’ RT = Rate of transformation
40
50
30
20
10
Temperature [“C]
Nucleation rate of glycerol and piperine depending on the temperature (after Tammann 1903) and nucleation rate of trilaurin (after Ravich eta/. 1946).
Fig. 6.20.
nuclei. The authors also proposed an equation that expresses the dependency on the degree of supersaturation defined as
a=- ‘ A
-S‘
L6.11
CS
where 6 is the degree of supersaturation, C, is the actual concentration, and Cs is the saturation concentration.
fats and Oils Handbook
464
The primary rate of nucleus formation Fp is a function of the degree of supersaturation as follows:
or
where k and A are individual constants. Starting from the nuclei, the crystals grow very rapidly until they have reached a size ten to a hundred times that of their nucleus (Matz 1970). In larger crystals. A
10” Nuclei /
I
d
Nuclei I s. IT? ,-I
og
1108 o7 -1 6 -1 d‘ 1102 Id
-I
1 30 60 90 Time [min]
B
120
,
10.2
0.4
0.6
Supersaturation
Crystal growth bm/h]
1000
I
I
I.. 8-Crystals ....................
-
0
0 20
30 40 Temperature rC]
0
30 Supersaturation
Fig. 6.21. Nucleation rate of fully saturated triglycerides of palm oil depending on temperature and supersaturation (above) and crystal growth of fully saturated triglycerides of palm oil depending on temperature and supersaturation (after van Putte and Bakker 1987)
Modification of Fats and Oils
465
slower mass transfer and restricted dissipation of heat of crystallization hinder rapid growth. This situation can be improved by agitation. Additionally, agitation decreases the initial time between the point at which supersaturation is reached and the initiation of crystal nucleus formation (Fig. 6.22). If the melt is inoculated with crystal nuclei, it must be noted that these can p r e mote crystal growth only if they consist of triglycerides that are also present in the oil to be crystallized. Additionally, they must have the same crystal modifcation that can crystallize at the temperature chosen. Reinders et al. (1932) found that cocoa butter does not crystallize if it is inoculated with tristearin crystals. Tristearin does not occw in cocoa butter. On the contrary, cocoa butter crystallizes spontaneously if oleostearin or palm kernel oil crystals, also present naturally in cocoa butter, are used. The explanation for p-crystals not being formed if inoculation is done with acrystals lies in their different crystal structure (see Chapter 2.3.1). A triclinic crystal cannot grow on the surface of a hexagonal crystal. To initiate growth, the same crystal modifications have to come together. As evidence, Nicolet (1920) showed that tristearin below 56°C crystallizes only in the a-form (m.p. 55"C), even if p-crystals (m.p. 72.5"C)are used for inoculation. In addition to the appropriate choice of inoculation crystals, the complete melting of crystal nuclei, the so-called resistant nuclei, has to be ensured by heating the system above its melting point and holding for an adequate time. Otherwise, these resistant nuclei would become effective during cooling and would prevent controlled crystallization of the melt from a virgin state.
6.2.7.4.2 Crystal growth. Crystal growth depends on many factors such as the temperature of the meltholution, relative to the AT of the solidification point of a Rate of crystal growth bm/min] 2.5 ..........................................
'Asymptote for R
= 00
2-
1 ' : System
/ Water at 27-28°C
CuS04 x 5 HO ,
Crystal growth rate without stirring
............................................
0
1
2
3
4
Stirrer speed R
Fig. 6.22. Dependency of crystal growth on the relative speed between crystal and solution (after McCabe and Stevens 1951).
Fats and Oils Handbook
466
melt and the actual temperature, the degree of supersaturation, the particle size of the crystals and the relative speed between meltholution and the crystal. Usually, one goal of a technical crystallization is to combine a low rate of nucleus formation with a high rate of crystal growth. McCabe and Stevens (195 1) showed the dependency on the relative speed between crystal and solution (Fig. 6.22). This relative speed, U, is of importance because mass transfer to the crystal surface has to be ensured. In addition, the heat of crystallization leads to local warming, which prevents further crystallization and has to be dissipated. The crystal growth curve runs asymp totically, with ro, rl and /3 the constants for each individual system. From the curve, it can be seen that the effect of stirring is limited (in this case to U = 2). This is less important because excessive agitation during crystallization shears the crystals. The fractions of these crystals have the same effect as that of nuclei, i.e., the rate of nuclei formation is unintentionally increased (secondary nucleus formation). Temperature has a much greater influence on crystal growth than supersaturation. Doubling supersaturation doubles the rate of crystal growth; halving temperature increases it a 100-fold (Fig. 6.22). Figure 6.23 shows the increase of viscosity and solids content of palm oil over the time of crystallization. The temperature of the cooling water is given as well as the stirrer speed. 6.2.2 Fractionation Techniques
At present, the following three main processing techniques are applied for fractionation: dry fractionation (without processing aids), Lanza fractionation (with wet100
1
100
Palm oil
.E 2o
8
55
0 0
2
4
8 8 1 Time [hours]
0
1
2
Fig. 6.23. Crystallization conditions of palm oil dependent on cooling and stirrer speed (courtesy of De Smet, Edegem).
Modification of Fats and Oils
467
ting agent), and wet fractionation (with solvents). Each process can be conducted in a very simple or in a highly sophisticated manner, thereby heavily influencing the yield, i.e., the sharpness of separation. Dry fractionation has the advantage that no processing aids are useqthat later have to be removed from the product. This is also environmentally more-friendly because there are no effluents or vapors. For the consumer, at least in countries with high awareness of such issues, there is a psychological advantage that the product has had no contact with processing aids (usually chemicals). Lanza and wet fractionation have the advantage of improved olein yields and superior separation sharpness. The price of this advantage is higher energy consumption (four times higher in the case of wet fractionation). Fractionation, as the total process is incorrectly referred to, can be split into the following two main steps: crystallization and the fractionation itself, i.e., separation of the olein from the stearin. All fractionation techniques consist of these two steps, allowing the combination of different methods of crystallization with different methods of separation. In the following, the three methods of fractionation are described followed by discussions of crystallization and separation of fractions. 6.2.2.1 Dry Fractionation 6.2.2.7.1 The principle of dry fractionation. Dry fractionation is based on the principles described in Chapter 6.2.1. Separation becomes possible because of the different melting points of the components forming the oil/fat. Olein and stearin are exclusively separated by filtration. 6.2.2.1.2 The process. The principle of dry fractionation is very simple. The oil/fat to be fractionated is heated above its melting point. Then it is cooled to the separation (fractionation)temperature and the fractions are separated from each other. The easiest way to do this is to heat the oil, cool it down in the same vessel and decant it. This method is applied, for example, to satisfy local demand in the poorer regions of Africa. There palm oil is heated to 75-90°C and allowed to cool down at ambient temperature to -32°C. Cooling takes a long time because ambient temperatures are between 20 and 30°C and AT is therefore low. Crystallized stearins sediment to the bottom of the vessel and the oil is decanted. Applying this method, the olein yield is -60%. This separation is not very sharp but satisfies local needs. Often the stearin from this operation is processed further by melting it at 80°C and, within 4-6 h, cooling it down in vessels with cooling jackets initially to 35°C and later to 22°C. The second olein, which is obtained in this manner, is pourable to 15°C and is used for cooking. The basic principle of fractionation as described above is also applied in all industrial processes. Only the technological expenditure is higher to achieve better separation via optimized temperature control and filtration techniques. Here also, simple and more sophisticated processes compete, depending mainly on the further use of the fractions (Fig. 6.24).
Fats and Oils Handbook
468
Fat
I
-
t > Fpb + 1OK (Fpb melting point of highest meking triglycsrldes)
Heating up
I I
I I
Cooling
stinlng slowly ( I W m i n ) during nuckation
Resting
at br(crystal-growth); cooling continued to conduct heat of crystallization
L
Filtration
+
-+
t
J
+
+ 4
vacuum-belt or dNm filter, p < p-30 hPa (p= ambknt pressure)
! c
L
c
1
Nz, 510min
1
1 t
t
F
R
cl -+
-+
F = Fittrate R = Solid residue b r = Fradination temperaturn
darin
0 !in Fig. 6.24.
Flow chart of dry fractionation.
In simplest form, crystallization is conducted in a vessel that is equipped with a slow stirrer and heating/cooling coils or jackets. The fat is heated to above its melting point so that it is completely melted and then cooled down. Temperature and cooling rate depend on the end products desired. The crystal mass suspended in the oil is separated into an olein and a stearin fraction. Separation has to be carried out quickly to avoid partial remelting of the crystals. Large plants are designed in such a way that crystal nuclei are formed in a precooling step in a large vessel that feeds several small crystallization vessels in which the crystals are allowed to grow. Thus, one achieves higher efficiency by separating the sensitive step of nucleus formation from the time-consuming step of crystal growth. 6.2.2.7.3Coolingprocesses. Commercial plants are run according to different modified processes that are usually connected with the name of the supplier of the equipment. The processes differ in the way the cooling step is carried out. Cooling influences the kind of crystallization, i.e., whether more or less olein is trapped in the stearin crystals, and also filterability. This in turn influences the fractionation yield,
Modification of Fats and Oils
469
meaning the amount of olein that could be separated in relation to the total. Deffense (1987), for example, managed to obtain 50% more olein in butter fat fractionation by slow cooling than with fast cooling (olein yield: fast cooling 50%, medium 65%, slow 75%). These figures may differ from oil to oil and may even be reversed. The processes recommended by C.M.B. and de Smet follow the principle of fast cooling. The oil is precooled for sufficient crystal nuclei formation. Then it is run via an intense cooler to quickly decrease the temperature. The surface of this cooler is large compared with its volume. This allows for quick cooling even if the temperature difference between the oil and the cooling medium is low. Cooling in the C.M.B. process is performed in three stages (see Chapter 6.2.2.5). Tirtiaux has patented a slow-cooling process usually carried out in vessels with slow stimng. These vessels are equipped with heatingkooling jackets and additional coils. The fat is first melted and then cooled following a special cooling pattern according to a cooling curve that has been elaborated for the individual fractionation operation. The amount of heat removed is varied according to the actual temperature. Heat of crystallization can thus be taken into account and quickly removed. Figure 6.25 shows cooling curves for different oils and fats. All curves show the expected shape, i.e., a temperature increase in the area of crystallization, caused by the heat of crystallization. It also becomes clear that a connection exists between the temperature at which this effect is observed and the duration of cooling.
6.2.2.1.4 Plants for dry fractionation. As noted above, Tirtiaux plants follow the route of slow cooling. The first cooling step with the formation of crystal nuclei takes place in special buffer tanks. From there, the oil is pumped into crystallizers Temperature [“C] Samples -A
= Soybean oil hardened I.V. Q6
. . . B = Fish oil hardened I.V. 103 - - C = Butter fat solidific. p. 28°C
50 40
30
20
- D = Palm oil I.V.
= 53
10
E = Edible tallow solidlfic. p. 46%
0 Fig. 6.25. Cooling curves for fractionation using the Tirtiaux process (after Tirtiaux).
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Fats and Oils Handbook
in which the cooling is done under automatic control. A schematic of that process is shown in Figure 6.26. The crystallizers are vessels of up to 40 MT, equipped with cooling jackets and cooiing tube coils. Usually the crystallizers feed a vacuum belt filter (Florentine type, see Fig. 6.36). Of course, any other filter type can be used.
Fig. 6.26. Semicontinuous fractionation plant (above) and crystallizers (below; Kellens 1993).
Modification of Fats and Oils
471
The filters allow a throughput of up to 260 MT/d, depending on the type of stearin. To obtain such capacities, each filter has to be fed by several crystallizers. To equip a fractionation plant for 200 MT of palm oil, for example, six to eight crystallizers have to feed two filters. Unlike the process recommended by Tirtiaux, the de Smet process uses rapid cooling. A typical plant consists of four crystallizers feeding one filter (see Chapter 6.2.2.2.3). The oil is pumped from a buffer vessel (A) via a cooler (B) that is cooled by cold water into one of the four crystallizers (C). Once a crystallizer is filled, the cooling program is started. During the whole cooling period, the content of the vessels is kept permanently in motion by means of stirrer blades. The normal cooling time is -4 h, and it is claimed that the process produces medium- sized crystals that can be filtered off easily. The crystallizers feed a continuous rotating vacuum filter (E) where the olein is filtered off through a nylon cloth. Tanks are for hot (H), cold (W) and refrigerated (R) water. The olein is collected in the olein tank (F) and the stearin is melted in tank G (Fig. 6.26). To fractionate 1 MT of product, an indication of energy and water consumption is given by the following figures: Steam (6 bar) Electricity Cooling water (closed circuit, 32°C) Cooling water (used up)
70 kg 30 kwh 20 m3 1 m3
There is practically no product loss. For double-stage fractionation, these figures would be -20% higher. 6.2.2.2. Lanza Fractionation
6.2.2.2.1 The principle o f Lanza fractionation. The so-called "Lanza"-fractionation is based on a patent that was granted to Fratelli Lanza in 1905. It differs from the dry fractionation process by the way in which the olein is separated from the stearin. Separation is not carried out by means of a purely mechanical treatment such as pressing or sucking through a filter; rather, the crystal surface is wetted with a detergent solution or a wetting agent. This solution may contain salts as an additive to prevent emulsion formation. The wetting agent wets the surface of the fat crystals that have been precipitated from the melt. The wetted crystals become hydrophilic and sediment to the aqueous phase. The oil has thus, so to speak, been washed free of fat. Big oil droplets that are totally free of crystals are formed; these droplets coalesce to form even bigger droplets, and, at the end, they form an almost continuous oil phase (Fig. 6.27). The two phases (olein and aqueous phase with the stearin) can be separated via centrifuges as a result of the difference in specific density. Only in the 1970s has the process been picked up and revitalized by Alfa Lava1 who market it as the Lipofrac process. An example of a suitable wetting agent is sodium lauryl sulphate.
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Fats and Oils Handbook
C: Formation of oil droplets without fat crystals
D: Feeding to separator
Fig. 6.27. Photomicrographs of crystal wetting in Lanza fractionation (courtesy of Tetra Lava1 AB, Tumba). 6.2.2.2.2 The process. The wetting agent is added in different portions. It is essential to stir vigorously during the addition of the first portion of sodium lauryl sulphate. Thus crystal agglomerates are crushed and the trapped oil is set free. Additionally, vigorous stirring is the only way to ensure complete wetting of the crystals. After the addition of the second portion, slow stirring is continued for a time. The oil droplets then coalesce, easing separation by centrifugation. The light (olein) phase is washed to remove all residues of detergent. If a multistage fractionation is conducted, it is not necessary to wash out the detergent completely because more is added again in the next stage. The heavy (crystavwater) phase is heated above the melting temperature of the stearin. The two resulting phases, namely, liquefied stearin and aqueous detergent solution are separated again by centrifugation. With the Lanza process, much smaller crystals can easily be separated from the olein than in the dry fractionation process. In general, this allows for much shorter crystallization times. The Lanza process can be applied to crude as well as
473
Modification of Fats and Oils Fat
t > Fpb+lOK (Fp= mMng point of h i g k t m M r g triglywride) to b, stinlng ( 1 W m l n )
to br (br fndknation-temprature) b = twd (b- tempraturn of detergent solution)
to crush agglomerates and to set fme trapped olein b = tsuoll
R
(twtemperature of Wetpent solution)
F
>>> Effluent
Stearin
Fig. 6.28.
Olein Processingflow chart of the Lama fractionation process.
refined oils and fats. Melting of the fat and crystallization follow the processing routes described before; only the separation step is different. (Fig. 6.28). The separation of the olein and the melted stearin from the detergent solution follows the principle of centrifugation described in Chapter 7. 6.2.2.2.3 Plants for Lanza fractionation. Several configurations of plants exist that all follow the same principle (Fig. 6.29). The oil is crystallized in crystallizers and is conveyed into a premix tank (A). There the wetting agent (sodium lauryl sulphate) is added, which may also contain an electrolyte (magnesium sulphate or sodium sulphate) to facilitate the agglomeration of the oil droplets and prevent emulsion formation. Initial mixing is done vigorously with a knife stirrer to destroy crystal agglomerates and ensure good wetting. Then, in a second tank (B) the mixture is gently stirred with paddle mixers while the oil droplets coalesce. In these two tanks, the lauryl sulphate solution, which is prepared in (C) and stored in (D), is added in portions. The crystal suspension and detergent solution must have the
Fats and Oils Handbook
474
Fig. 6.29.
Lanza fractionation plant (courtesy of Tetra Laval, Tumba).
same temperature to guarantee good results. After -2 min holding time, the mixture is separated via a centrifuge (E). The separated olein is carefully washed with water, and the water is then separated in a washing centrifuge. The steariddetergents solution mixture is melted (F) in a plate heat exchanger, stored ( G ) and also separated by centrifugation (H). The lauryl sulfate solution that has been separated is cooled countercurrently (6) and pumped into storage (4)to be reused. The melted stearin is also carefully washed and pumped into a storage tank. Table 6.2 lists consumption of energy and processing aids as well as the oil losses for a plant for the fractionation of 100 MT/d palm oil or lard. The consumption of electrical energy for palm oil fractionation is higher than for lard fractionation because lard can be cooled with water to 30-35°C; for the cooling of palm oil to 20°C however, electrical energy is required to dissipate the heat.
475
Modification o f Fats and Oils
TABLE 6.2 Energy Consumption for Fractionation Processes Consumption per ton for Lanza fractionation
Palm oil
Lard
Steam (4 bar)
150 30 0.2 0.24.6 0.2-0.7
150 18 0.2 0.2-0.6 0.2-0.7
Dry fractionation
Solvent fractionation
Electrical energy Cooling water Na-laurylsulfate Electrolyte, MgSO,,
(kg) (kWh) (m3)
Na2SO4
(kg) (kg)
Consumption for double-stage fractionation of palm oil Steam (6 bar) Electrical energy Water Solvent Yield: Olein Stearin I Stearin II
(kg)
(Oh)
85 36 1.2 60
(Oh)
40
18
40
12
(kWh) (m3)
(kg)
400 35 1
a 70
6.2.2.3 Wet Fractionation 6.2.2.3.7 The principle of wet fractionation. Wet fractionation is not based on the principle of different melting points but on different solubility of the oiYfat fractions in a solvent at a certain temperature. Although the melting points for POP (37"C), PPO (40°C) and PPP (65.772) differ by only 3 and -28"C, respectively, there is a greater difference in solubility, namely, POPPPOPPP is -1:3.5:0.002. Solvent fractionation leads to much higher separation sharpness, because crystallization can be influenced not only by changing the temperature but also by varying the amount of solvent. Beyond that, if there is olein entrained in the crystals, it is less pure olein because the entrained olein is diluted with solvent. The same holds true for the olein that wets the crystals. Additionally, the crystals may be washed olein free with the solvent if high-purity stearin is needed. Many specialty fats can be produced in the desired purity only by wet fractionation. It is the preferred method, for example, for the fractionation of triglycerides composed of two long-chain and one medium-chain fatty acids. The crystallized and the separated amount is dependent, of course, on the fractionation temperature and time (see Fig. 6.30). 6.2.2.3.2 The wet fractionation process. The main processing step in wet fractionation is the cooling step because this determines the separation and, with that, the final properties of the fractions. Like all other fractionation process, wet fractionation can also be conducted as a double-stage process (Fig. 6.31). The process for separation of solvent and oil is same as described in Chapter 5.2.3 for solvent extraction.
Fats and Oils Handbook
476
Removed solids
I
14
[%I
1
8-
JI
6-
"
1:
-8°C
t
-11°C
I
4-
- 6,5"C
20 0
2
4
6
8 10 12 14 16 18 20 22 24
Time [h] Fig. 6.30. Cooling curve for wet fractionation of palm oil (after C.M.B.). 6.2.2.3.3 Plants for wet fractionation. In principle, a wet fractionation plant consists of a mixing vessel (A) in which fat is dissolved in the solvent that is fed from a buffer. From there, the solution is pumped into a crystallizer (Ba or Bb) where it is cooled to the fractionation temperature. The cooled walls of the crystallizer are permanently scraped to ensure good heat transfer. The crystals precipitated from the solvent are separated by means of a hermetically closed filter (C) (otherwise the solvent would evaporate). Therefore, the whole plant must be constructed to be explosion proof. The stearin is separated, melted and the liquefied stearin is desolventized. The miscella (olein + solvent), intermediately stored in (D), is pumped to the second crystallization stage (E), where it is further cooled and then separated 0again. Stearin II is processed in the same way as stearin I. The solvent is distilled off from the miscella, leaving the olein behind. The solvent is pumped back into the buffer for reuse. Table 6.3 shows a comparison between energy and processing aids consump tion for the double-stage dry and the wet fractionation processes, assuming a plant capacity of 200 MTId. .The different fractionation techniques are compared in Chapter 6.2.2.7. 6.2.2.4 Other Processes. Again and again, attempts have been made to improve the traditional fractionation techniques. Hahn (1978), for example, conducted trials to selectively crystallize stearin on a chilled surface. The melt was kept at melting temperature while the higher melting fractions were crystallized on the chilled surface and the lower melting fractions were enriched in the liquid. To remove the crystallized stearin, the chilled walls were scraped. The trials were conducted with palm oil. The temperature of the chilled surface had to be adjusted in a way that prevented any part of the desired olein to precipitate (-20°C c tF c +20"C). To
Modification of Fats and Oils
477
Fat
I
SObbnt wapmtion I
I Solvent evaporstion I
I
I"
oldin II
Stairin 11
3 Dittlllstion Sbadn I
Fig. 6.31. Double-stage wet fractionation flow chart (above) and plant (below; after Bernardini 1985, courtesy of C.M.B. Pomezia).
measure success, a separation factorf, was defined as the quotient of the areas under the melting curves of the fractionated fat f, and the native fat fo: f, = f J f o
[6.31
Stirring was necessary to compensate for the depletion of the higher melting portion of the melt in the vicinity of the chilled surface and to prevent olein from being trapped in
Fats and Oils Handbook
478
TABLE 6.3 Triglyceride Classes of Dry Fractionated Palm O i l with Rapid or Slow Cooling and Lanza Fractionated Palm Oila ~~~
~
~
~
~~
~
~
~
Olein Fractionation
~~~
~~~~~~~~~~~~
Stearin
Dry, rapid
Dry, slow
Lanza
Dry, rapid
Dry, slow
Lanza
58.4 23.3 60
57.2 22.2 68
57.8 21.7 83
40.7 45.9 40
28.6 50.7 32
28.0 55.3 17
0.7 47.9 44.1 7.3
0.4 40.1 44.7 6.8
0.3 50.2 43.2 6.3
13.8 46.2 34.6 5.4
21.9 47.0 27.1 4.0
42.0 41.4 14.2 2.4
~~~
Iodine value Slip melting point ("C) Yield (%) Triglyceride class (%) s3
u
s2 su2
u3
aSource:Deffense (1 985).
the crystals. It was remarkable that the yield for refined palm oil was higher than for crude palm oil. Until now, this process has not been applied on a large scale. Its advantage would be that it could be used continuously with little effort for automation.
6.2.2.5 Crystallization. Crystallizers usually consist of a batch vessel that is equipped with a stirrer and can be cooled. Because crystal growth heavily influences filterability, separation sharpness and yield, crystallizers have been subject to a constant drive for improvement. A complete overview is given by Mersmann (1982). The simple vessels described in Chapter 6.2.2.1.1 have evolved into devices that are equipped with specially shaped low-speed stirrers. The walls are polished and can be cooled to best dissipate the heat of crystallization. Considerable effort has been made to shorten the crystallization time, to develop the process from a batchwise mode into a continuous one as well as to save energy. The main effort was to maintain the temperature as closely as possible according to the desired cooling pattern. To solve this problem, it was proposed, for example, to cool via external coolers. This allows the use of simple vessels and keeps the temperature difference narrow. With such a vessel (e.g., the Tetra Lava1 system), the oil is cooled in two stages via 35°C to 25-27°C. If the Lipofrac process is used, some detergent solution is added after stage one. The mixture is then pumped into crystallizer I in which it is kept for -30 min. It is then pumped into crystallizer I1 while passing through a plate heat exchanger (PHE) in which the total mixture is cooled down by 3-5°C.After holding in crystallizer 11, it is pumped into crystallizer I11 passing again through a PHE. A plant with this configuration has a capacity of 300 MT/d. This can be increased by adding further coolers/crystallizers. Because of a higher ratio of cooling surface and volume, the use of PHE ensures more uniform cooling compared with cooling in batch vessels. Additionally, the heat of crystallization can be dissipated more quickly and the cooling rate can be adjusted individually to
Modification of Fats and Oils
479
the oil. Alfa Lava1 claims that this form of cooling combined with the Lipofrac process allows for yields as high as 85%. C.M.B recommends three-stage crystallizers. The oil is first cooled with water of 32"C, then again with water of 12°C and, in the last stage, with water of 6°C. The water used is circulated via a chilling unit. The crystallization time of an oil fed at -58°C is reported to be -120 min. The temperature decreases by -20°C. In the second stage, an additional 150 min is needed to cool the oil another 15°C. After another 150 min in stage three, the final temperature of -8°C is reached. In typical plants, every filter is generally fed by several crystallizers. 6.2.2.6 Separation of Olein and Stearin. The separation of olein and stearin is usually done by filtration. Separation sharpness, on the one hand, is influenced by good crystallization, i.e., no entrainment of olein in the stearin crystals and sufficient crystal size. On the other hand, it very much depends on the efficiency of the filtration step. However, one must bear in mind that filtration is able to remove only solids from liquids. Stearin that is dissolved in the olein cannot be separated. Van Putte and Bakker (1987) showed the dependency of dissolved stearin for the case of tristearin in palm oil. There is an almost logarithmic dependency on the temperature. For P-crystals, 0.1% tristearin is soluble at 33°C (fY at 20°C) and 100% at 62°C (56°C). The dissolved part cannot be separated by any means. Figure 6.32 demonstrates the influence of the polymorphic form of the crystal on the separation. Separation by means of filtration is important not only for fractionation but also for bleaching in the course of refining (see Chapter 7.4). In other applications, the aim is simply to separate a processing aid from liquid oil, whereas in fractionation, the goal is the separation of two aggregation states of the same class of substance. The filters are therefore of different construction depending on the need. In this book, therefore, different types of filters are described in the context of their main usage. In fractionation, these are mainly membrane filter presses, vacuum belt filters and rotary drum filters. The construction and working principle of these types are dealt with in the following. The crystayoil suspension can be separated by means of normal filter presses. The filter cloth is typically made from natural fabrics ( e g , cotton) or synthetics (e.g., nylon). The filtration capacity depends on the surface and properties of the cloth, on the filtration pressure and, of course, on the amount, the type and the size of the crystals. One possibile way to increase the yield involves blowing for 5-10 min with nitrogen to blow as much olein from the stearin as possible. Although in this case, the olein is blown through the filter cloth, most of the common plants are designed to suck it through. Two types of filters are used for this purpose, those that use a drum and those with a belt. In a certain sense, the belt is a squeezed, stretched drum, so that the two techniques do not differ in principle. Figure 6.33 shows some membrane filter tests conducted with palm oil.
6.2.2.6.1 Membrane filter presses. Membrane filter presses resemble ordinary filter presses in their construction (see Chapter 7.4, bleaching). However, they are
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Fats and Oils Handbook
Fig. 6.32. Electron photomicrographs of the polymorphic forms of palm oil SSS crystals; A, p (non-stirred); B, p’ (non-stirred); C, p’ (agglomerated) (after van Putte and Bakker 1987).
also equipped with an elastic membrane ( l ) , usually made from rubber or polypropylene. The filter is filled in the common way (2) with the suspension of stearin crystals and olein. The crystals are filtered off by the cloth. The olein is collected in the drains (3) and leaves the filter via the pipe (4)that is formed by the row of holes in the individual filter plates that are tightly pressed together. When the filter cake has reached a certain thickness, the membrane is blown with compressed air (5). In this way, the membrane is pressed onto the filter cake, squeezing out the residual olein. An almost olein-free stearin can be obtained. Hard and equal-sized crystals are a prerequisite for this filtration method (Fig. 6.34). Because such filters are basically constructed by coupling a number of segments (i.e., a number of filter plates), their capacity depends mainly on the number of filter plates that form the filter. For the fractionation of palm oil, 0.1 MT per hour and per filter plate can be expected. A press with 50 plates thus roughly equals the capacity of a vacuum belt filter (see Chapter 6.2.2.6.2).It must be mentioned that membrane filter presses can be operated only discontinuously because the stearin has to be removed once the cake has reached a certain thickness. For this purpose, the press is opened and the cake is removed mechanically.
Modification of Fats and Oils
481
n
-2
0
5
10 15 Filtration time [min]
20
25
Fig. 6.33. Membrane press filtration tests with palm oil fractions (Kellens 1993).
Brought into the perspective of a plant, the crystal/oil suspension (A) is pumped through the membrane filter press (1). The olein is collected in an intermediate storage vessel (2) from which it is pumped if needed. After the filter cake is thick enough, compressed air (3) is allowed to enter the membrane section. After the olein is squeezed out, the air is released (4) and the stearin is collected ( 5 ) . There it is melted with the use of steam and pumped off (Fig. 6.35). 6.2.2.6.2 Vacuum belt filters. Vacuum belt filters are widely known and used in the industry. They can be adjusted easily to varying needs and can be maintained and cleaned without great effort. The main characteristic of this type of filter is a horizontal filter belt that is stretched between two driving drums. This belt, usually made of stainless steel (but types with rubber belts also exist), passes over a horizontal opening in a.tank that is kept under vacuum. There are also some new versions that use sliding cells instead of the belt. These cells are tight against each other when passing the horizontal section. In the area of the drum, the vacuum is broken so that the filter cake falls off or can be scraped off. Today’s belt filters are housed in a climatized chamber. The belt itself is also kept at fractionation temperature. One of the most common filters is Tirtiaux’s Florentine filter. The suspension (A) is fed by a pump to the feeder (l), which feeds it to the belt. The first section (I) is variable and ensures that no stearin sucked through the filter belt is entering the olein tank. The suspension passing through the filter in this area is collected in (2) and fed to the filter again, jointly with fresh suspension coming from (A). In the next section (11), the filtrate (F) is
Fats and Oils Handbook
Fig. 6.34. Membrane filter press (above) and plant with membrane filter presses (below); courtesy of Tirtiaux S.A., Fleurus.
sucked through the filter into (3). The cake is thick enough in this section to ensure good separation sharpness. Sections I and II can be adjusted easily to individual runs md individual raw materials. In the first part of section II, the suspension is filtered; in &e second part it is “dried,” i.e., the stearin filter cake is sucked dry from the rest of he olein. At the turning point of the belt on the right drum, a scraper (4)removes the
Modification of Fats and Oils
483
Fig. 6.35. Simplified process flow sheet of filtration with membrane filter presses (above, courtesy of Tirtiaux S.A., Fleurus) and high-pressure hydrofilter press (below; courtesy of Krupp Maschinentechnik CmbH, Hamburg).
stearin cake from the belt. The stearin falls into a container (5). The belt, returning to the left drum, is heated by infrared lamps and its holes are blown free of melted stearin. The olein from (3) is pumped off. The stearin is also pumped off after it has been melted in (8) by hot water or steam (Fig. 6.36). The throughput of such filters very much depends on the materials being filtered. Typical throughputs are 4-6 MT/h for palm oil, butter oil and hardened oils and 9-1 1 MTih for beef tallow.
484
Fats and Oils Handbook
Fig. 6.36. Vacuum belt filter Florentine type (right) and plant with vacuum belt filter (left); courtesy of Tirtiaux S.A., Fleurus.
6.2.2.6.3 Rotary drum filters. Vacuum drum filters (Fig. 6.37) consist of a drum that is divided into sections. Its outer wall is perforated and covered with a filter cloth. Drums exist with a diameter of up to 5 m; as an addition to the vacuum system, they may be equipped with outer rolls that squeeze out the filter cake. The cake itself is separated from the cloth by means of scrapers, rolls, chains or strings. The suspension is pumped into the filter trough (F). The filling level is controlled
Modification of Fats and Oils
485
Fig. 6.37. Vacuum drum filter (courtesy of Amafilter b.v., Alkmaar).
by an overflow or sensors. The trough is equipped with a swing stirrer (S), which rotates with a frequency of 20 timedmin to prevent the sedimentation of solids from the suspension. The vacuum filter drum (T) is immersed to the depth of 25-33% of its diameter (1) into the trough, which holds the stearin suspended in the olein. The drum rotates through the trough. The rotational speed RS is variable (0.1 c RS c 1.0 turndmin) and is adjusted to the needs of different products. An adjustable vacuum is effective on different segments of the drum as long as it dips into the suspension (1). The olein is then sucked to the inside and the stearin is collected on the cloth. To prevent the filter cake from coming off and to suck in the olein completely, the vacuum is maintained until the filter cloth is tangentially guided away from the drum (+2 + 3). In the upper part of the drum, it is possibile to wash the stearin by means of a spray head or to squeeze out residual olein by means of a pressure roll (not included in the drawing) and to compress the cake (in area 3). Thorough separation of the cake from the cloth (4) is a prerequisite for good filter performance (Fig. 6.38). The figure shows loosening the cake with the aid of strings that are stretched around the drum together with the cloth. Diverting the strings around the scraping roll, the filter cake bursts off and falls into the collecting vessel. The strings are
486
Fats and Oi/s Handbook
Fig. 6.38. Vacuum drum filter, principal drawing and cake removal (courtesy of Amafilter b.v., Alkmaar).
adjusted to the appropriate distance from each other, passing through a comb. This construction minimizes wear on the filter cloth and allows the use of fine cloths because the stress applied to the cloth is low. Rotary drum filters are available in different sizes, i.e., different filter areas. AMA offers filter areas of up to 80 m3. The filtration capacity for palm oil with
Modification of Fats and Oils
* ;
487
Palm oil fractions Viscosity
Olein yield
SFC cake
3
5
7 9 Sampling time [hours]
11
Fig. 6.39. Vacuum filtration tests with palm oil fractions (Kellens 1993).
20% stearin, for example, is 200-300 L/(m2 ' h). Figure 6.39 gives the result of some vacuum filtration tests carried out by de Smet. 6.2.2.6.4 Comparison of filtration techniques. The different separation techniques result in different costs for investment or for operating the plant and also offer different sharpness of separation. Figure 6.40 shows the separation factors for
Fig. 6.40.
Separation sharpness in of palm oil fractionation (after Stover e t a / . 1983).
488
Fats and Oils Handbook
a dry-fractionated refined palm oil that has been separated by different means. As a comparison, some points reflecting the separation factor of the wet and the Lanza process are given. The higher separation factor with membrane filter presses must be paid for with a 10-15% higher investment. Automation that would lead to lower running cost is much more difficult to achieve than with continuously running belt or drum filters. The different separation sharpness is caused by the different pressures that can be applied. Suction filtration is promoted by a vacuum of 200 Wa (maximum), whereas the pressure in membrane presses is much higher. Trials with Krupp presses allowed for pressures on the membrane of up to 8 bar without the crystals being pressed through the filter cloths (Stover et al. 1983). In summary, it can be said that the advantage of rotary drum filters is their low investment cost combined with sturdy construction and easy handling, including easy cake discharge. Membrane filter presses allow for a sharper separation, i.e., higher olein yields with better quality. They have lower energy consumption with easy filtration and drying, combined with high-speed filtration. The fatty matter is protected from contact with oxygen from air. 6.2.2.7 Comparison of the Fractionation Techniques. Kreulen (1976) and Deffense (1985) gave a comparison of palm oil fractions that were produced with different fractionation methods (Fig. 6.41). The figure shows that the end products differ considerably. The solids content of Lanza-fractionated palm oil is approximately twice that of the dry-fractionated stearins. However, these also differ from
Fig. 6.41. Solids content of palm stearin depending on the fractionation process applied (after Deffense 1982).
489
Modification of Fats and Oils
TABLE 6.4 Olein Entrainment in Stearin Cake of Different Fatty Matters (Standard 6-bar Membrane Filter)a Solid fats content, SFC ( O h ) Origin of fattv matter Palm oil IV 52
Palm oil in mid-fraction IV 49
Soybean oil Hydrogenated 1V 75 Milk fat Tallow Lard
Slurry
Cake
14 20 29 15 24 31 31 33 11 16 13 12
58 55 51 73 61 55 64 74 54 42 44 41
Olein entrainment (YO)
42 45 49 27 39 45 31 26 46 58 56 59
aSource: Kellens (19941, courtesy of de Smet, Edegem.
each other because the slowly cooled product contains only 50% more solids than the rapidly cooled one. Therefore, the fractionation technique chosen heavily influences the end products. Because one cannot usually switch between these processing varieties inside a given plant, the decision how to build the plant must always be based on the desired properties of the end products. The different fractionation techniques also deliver different triglyceride composition in the olein and stearin. Duns (1985, Table 6.4) compared products obtained from dry and Lanza fractionation of palm oil. The results reported in the following originate from trials that were conducted on the equipment of Tirtiaux (dry fractionation), Alfa Laval (Lanza fractionation, Lipofrac) and C.M.B. (Bernardini, wet fractionation). Table 6.5 shows the processing conditions that have led to the results represented in Figures 6.42 and 6.43. In the figure, 0 refers to crude olein and S to crude stearin. Wet fractionation has been conducted as a two-stage process (indexed I and 11). TABLE 6.5 Process Conditions for Palm Oil Fractionation Trialsa Wet Process conditions Starting temperature Cooled down to Cooled down to
("C) ("C) ("C)
aSources: Tirtiaux. Alfa Laval and Bernardini.
DW
Double
Triple
70 40 20
45 30-33 20+10
7+4+2
490
Fats and Oils Handbook
TABLE 6.6 Data of Palm Olein from Different Fractionation and of Tallow from Different Separation Technique9 Olein characteristics Yield Palm oil (fractionation techniques) Dry fractionation Fast cooling during crystallization Slow cooling during crystallization Lanza fractionation Wet fractionation"
Iodine value
Solidification point ("C)
58.0
24.0
57.8 57.6
22.2 24.2
(Old
Iodine value
Solidification point ("C)
77-82 43-48 67-72 37-42
50.0 55.5 50.0 55.1
39.0 20.5 39.5 22.2
(Old
6C-63 67-72 77-83 60-63 Yield
Tallow (dry fractionation separation techniques) Membrane filter press (olein D.P. 37-38°C) (olein D.P. 20-22°C) Rotary drum filter (olein D.P. 37-38OC) (olein D.P. 20-22°C) aSource: Deffense (1 985) and Kokken (1 990).
Product characteristics changes during fractionation:
Fig. 6.42. influence of different fractionation processes on the fatty acid composition of the fractions and on the olein properties.
Modification of Fats and Oils
49 1
Fig. 6.43. Influence of different fractionation processes on the triglyceride classes of the fractions.
6.2.3 The Properties of Fractionated Oils and Fats
As mentioned in the introduction to this chapter, fats and oils are being modified to obtain products that are not available in sufficient quantity or to replace products that have a very high price. This also holds true for fractionation. Particular efforts have been made to find a substitute for cocoa butter. Attempts have been made to improve the use of palm oil (solidification point 2 7 4 3 ° C ) at lower temperatures, i.e., to enable its use as salad oil. Today, more than 50% of the palm oil production is fractionated. Taking the absolute tonnage, cocoa butter replacers are a nonplayer in comparison; however, this part of the process has great economic importance due to the high price of the CBE. There is a trend to produce tailor-made fats from “common” raw materials, without using processing aids. There is also a tendency to open new applications for traditional raw materials such as butter. However, the main focus clearly lies on palm oil. Many new fractionation plants have been built in the countries of origin, reflecting the dramatic increase in palm oil production. Because one of the aims was to supply the local markets with the olein, the amount of palm stearin offered in the world market has increased significantly as a consequence. Often modification techniques are combined, because this is the only way to achieve’thedesired results. In the trials described in the following, S, and 0, stand for the stearin or olein that result from a fractionation at temperature x. Saturated fatty acids are always represented by the letter S , whereas U refers to unsaturated ones. The opportunities in fractionation are almost endless, taking into account different fractionation temperatures and single to multistage processes. The deliberately chosen examples in the following can give only a rough impression of the range of
492
Fats and Oils Handbook
Fig. 6.44.
Properties of tallow fractions depending on the fractionation temperature (after Deffense).
products that can be obtained. The different ways of influencing the end products are illustrated for different raw materials. Figure 6.44 offers a view of the wide possibilities of changing the properties of Argentinean beef tallow, depending on the fractionation temperature. As can be expected, the iodine value of the olein is inversely proportional to this temperature. Olein yield and melting points must change proportionally. Naturally, the trend for stearins is the reverse of that for the oleins. 6.2.3.1 Lard. As described in Chapter 6.4, lard is often interesterified to improve its crystallization behavior. Improving these properties also increases its yield in fractional crystallization. Table 6.7 and Figure 6.45 show an example (Deffense 1987) of a double-stage fractionation and the properties of the resulting end products. Of course, the interesterification step before fractionation does not lead to a change in iodine value, but to a significant change in the way fatty acids are distributed over the glycerol backbone. The main shift is a decrease of the types POS and SPO by -40% and an increase of SOO, SLS and OLA by -60%. To give a clearer picture of the effect of these modification techniques, only four global triglyceride types are shown in Figure 6.46, namely, S3, S,U, SU, and U3.A dramatic change in the proportion of these types can be seen, making clear the influence of these processes. If the olein 03*is further fractionated, a whole range of secondary products can be obtained. If the second fractionation temperature is kept below 22'C, fully saturated triglycerides disappear from the product almost completely and S3
Modification of Fats and Oils
493
TABLE 6.7 Data of Lard and Its Fractions from Double-Stage Fractionationa Melting point
Iodine value (IV) Lard, native Lard, interesterified Stearin S32
63.9 63.4 50.4 67.3 55.9 58.7 59.6 69.2 70.6 73.2
Olein 03, 032-s22 032-s1
8
032-s14 O32-%2 O32-Ol8 032-01 4
Yield
("C)
(%F)
37.7 34.7 47.3
99.9 94.5 117.1 85.1 101.7 98.1 93.9 72.0 64.4 59.2
29.5 38.7 36.7 34.4 22.2 18.0 15.1
(O/o)
(% of initial)
20.2 79.8 18.3 31.4 43.1 80.7 68.6 56.9
Code N
U 20.2 79.8 15.4 25.0 34.4 64.4 54.9 45.4
H
A B C D E
F C
aSource: Deffense.
increases heavily in the stearin (Fig. 6.47). The properties of the different fractions become even clearer when their solids content is plotted against the fractionation temperature (Fig. 6.48).
6.2.3.2 Beef Tallow. Apart from lard, beef tallow is the most fractionated animal fat. The differences in the physical properties of the fractions are much greater than in lard. This becomes apparent in Figure 6.49, which shows the proportion of some fractions depending on the fractionation temperature. If a three-stage separation is conducted according to the fractionation tree principle, Argentinean beef tallow Lard
(m.p. = 38'~; I.V. = 63.9) Interesterlficstion
I.V. = Iodine value m.p. = Melting point i.a. = of initial amount
Intelustrrifkd lard (m.p. = 35'C; I.V. = 63.9) Fractionation32'C
(m.p. = 48%; I.V.
= 50.4)
(m.p. = W C i I.V. = 67.3)
I
Fradbwtlon 18%
I 31% (25% La.) Stearin @zSi:
-
(m.p. 36%;
I.V. = 58.7)
I
i
69% (55% La.) Olein 031-0011 (m.p. = 18'C; I.V. = 70.5)
Fig. 6.45. lnteresterification and double-stage fractionation of lard (after Ricci Rossi and Deffense 1984).
Fats and Oils Handbook
494
Fig. 6.46.
Proportion of triglyceride classes of lard (trials from Table 6.7).
can be separated into four products of considerably different properties (Fig. 6.50). Fractions obtained at different temperatures are shown in Figure 6.51, reflected by their fatty acid composition. Table 6.8 gives the fractionation results for doublestage fractionation of tallow at a constant first temperature and various second temperatures. The solids content of part of these fractions is given in Figures 6.52,
Fig. 6.47. Proportion of.triglyceride classes of lard and its double stage fractions (trials from Table 6.7).
495
Modification of Fats and Oils
Solids content
Lard
[%I
vv
Fraction. = interest.
-I
+ A = 032 = S32
-H
+ B = O32-S22
*D
= O32-S14
+E *G
= 032-022 = 032-014
5
10 15 20 25 30 35 40 45 50 Temperature
[“C]
Fig. 6.48. Fatty acid composition of lard and its double stage fractions (trials from Table 6.7). 6.53, and 6.54. With the use of this technique, products can be obtained that contain very different portions of solids at equal temperature. 00-fractions can be used as liquid shortenings, 0s and SO fractions as shortenings. The SS part is usually used up in the soap industry. Its melting temperature lies significantly above body temperature making it unsuitable for human consumption.
6.2.3.3 Butter Fat. The only fractionation process suitable for butter fat fractionation, provided that the butter flavors have to be retained, is dry fractionation. Edible tallow
PerCBntaws based on M P I amount
224% StaannV
Fig. 6.49. Multistage fractionation of edible tallow (after Gander 1969)
Fats and Oils Handbook
496
-
EdiMe tallow (AfgenUnian) (m.p. = 45.1%; I.v. = 51.2)
68%Obin 0 1 6 (m.p. = 38.2'C; I.V. = 49.0)
(m.p. = 41.9.C:
34% SteatInSw (m.p. 50.8.C I.V. = X.0)
I.V. = 42.2)
63% (42% 1,s.) Obln C k d h (m.p. = 22.3.C: I.V. = 54.2)
Fig. 6.50.
I.V. lOdhmVdue m.p. =Melting point 1.a. = of I n W amount
(m.p. = u.9.C;
I.V.
= 42.0)
59% (20%I.&) Stearin Swslr (m.p. = 0.2'c;
I.V. = 30.6)
Three-stage fractionation of edible tallow (after Deffense 1984).
Often, this is conducted as a double-stage process (Fig. 6.55 and Table 6.9). Unlike most vegetable fats, the properties of butter fat can vary greatly, depending on the season as a result of a different fatty acid composition (see Fig. 3.3). The stearin fraction can be one third higher in winter, with a predictable effect on the olein. Deffense (1987) described the olein yield as a function of the fractionation temperature and the cooling method. Figures 6.56 and 6.57 show the proportions of important fatty acids and the solids content for different fractionation temperatures. The cooling rate (At/t) also influences the olein yield and thereby the composition. The above examples reflect processing conditions using a medium cooling rate. With the application of rapid cooling techniques, the olein yield decreases by -10%; with slow cooling, it increases by the same amount.
Fig. 6.51,
Fatty acid composition of different fractions of Argentinean tallow.
497
Modification of Fats and Oils
TABLE 6.8
Characteristics of Tallow and Its Fractions from Double-Stage Fractionationa Melting point
Yield
Iodine value, IV
("C)
("F)
Tallow
45.0
45.1
113.2
Olein 03,
49.0
36.2 40.8
31.6 24.6 20.0 16.7 12.5 9.8 34.4 41.4 46.0 49.3 53.5 56.2
(% of initial)
Code
-
-
n
66.0 47.9 37.4 30.4 25.3 19.0 14.8 52.1 62.6 69.6 74.7 80.9 85.2
-
a Aa Ab Ac Ad Ae Af Ag Ah Ai Aj Ak Al
036-s22
42.2
41.9
036-s24
41.7 41.3 39.6 38.3 55.2 54.2 53.8 52.4 51.8 51.4
42.7 43.4 44.2 44.7 10.5 T 22.3 24.5 26.6 29.0 30.4
97.2 105.4 107.4 108.9 110.1 111.6 112.5 50.9 T 72.1 76.1 79.9 84.2 86.7
36.1 30.6 30.6 29.4 27.1 42 .O 42.0 40.9 40.0
50.8 53.2 53.3 54.0 54.7 44.9 45.4
123.4 127.8 127.9 129.2 130.5 112.8 113.7
34.0 58.8 57.1 47.6 32.6 41.2 42.9
20.0 19.4 16.2 11.1 14.0 14.6
Hb Hc Hd He Hf
46.4 47.5
115.5 117.5
52.4 67.4
17.8 22.9
Hg Hh
O 3 6-s2 0
036-s26 036-s28 O 3 6-s2 9 O36-O20 O36-O22 O36-O24 O 3 6 -O 2 6 O 3 6 -O 2 8 O36-O29
Stearin s 3 6 s36-s45 s36-s46 s36-s47 s36-s48 s36445 s36446 s36-047 s36-048
-
-
H Ha
aSource: Deffense.
The stearin fraction of butter oil can be used in bakery products such as puff pastry and croissants; its plasticity is high. The olein fractions can be used in cake and (legislation permitting) cheese making. Use as the oil portion in melanges is also possible as well as applications in cream fillings for cakes and sweets.
6.2.3.4 Palm Oil. The fractionation of palm oil has increased in line with its greater availability in recent years (see Chapter 4.2.1). Worldwide, -5 MMT are fractionated. Palm oil offers fractionation opportunity because it contains approximately equal proportions of low- and of high-melting triglycerides. It can be separated into an olein, which can serve as a salad oil, and a stearin. In addition to this separation, cocoa butter-like fractions can be produced. Depending on the fractionation technique, different oleins and stearins are obtained. Some typical end products are listed and discussed in the following (Fig. 6.58). Interesterification before fractionation yields an even larger number of different products because of the change in triglyceride composition during interesterification (Table 6.10).
Fats and Oils Handbook
498
Edible tallow
Solids content [%]
100
Fraction 'A- Ha
= s36-s45
*H
= s36
+N
= Native
'A
=Os
80
.
..
A..
.*H*
~
-.:'.
.. Ha
:
,
.
. ..
.
.
.
."Ag = 036-020
5
10
15
20
25
30
35
40
Temperature ["C] Fig. 6.52. Solids content of tallow olein 0 3 6 and its double-stage fractions (trials from Table 6.8).
In many applications, slightly hardened palm oil is preferred because hydrogenation is much cheaper than fractionation. However, hydrogenated products have some practical drawbacks. Combining hardening and fractionation, the advantages of both processes can be merged, and interesterification can also be
Solids content [%] I
5
10
15
20
25
30
35
40
Temperature ["C] Fig. 6.53.
Solids content of tallow and its double-stage fractions (trials from Table 6.8).
Modification of Fats and Oils
499
-Solids content
[%I
100
2nd stearins
60 -
40 -
20 -
0
I 15 5
20
10
25
30
35
40
Temperature ["C]
Fig. 6.54. Solids content of tallow stearin s36 and its double-stage fractions (trials from Table 6.8). Butter oil
(m.p. = 32'C;
I.V. = 37.8)
I.V. = Iodine value m.p.= Mfflng point i.a. =of infflal amount
FraCtiOnstion 2O'C
40% Stearin S20
60% Obin 0x0 (m.p. = 1vci 1.V. = 42.5)
(m.p. = 40'C; I.V. = 31.3)
Fractlonatlon 1O'C
39Oh (23% i a ) ' Stearin 02oS10
61% (37% i.8.j Olein Ozc-010 (m.p. = 1o'C; I.V. = 47.8)
(m.p. = 24'C; 1.V. = 37.5)
Fig. 6.55.
Double-stage fractionation of butter oil (after Deffense 1987).
TABLE 6.9 Characteristics of Butter Oil and Its Fractions from Double-Stage Fractionationa Iodine value (IV)
Melting point ("C)
(OF)
Yield (%)
(% of initial)
-
N
23 77
A B
Butter oil
37.8
32
90
-
Olein 02,
42.5 37.5 47.8 31.3
18
64 75
60 39 61 40
020-s20 020-s20
Stearin S,, aSource: Deffense (1987).
24 10
50
40
104
-
Code
C H
Fats and Oils Handbook
500
Proportion [%]
Fig. 6.56. Table 6.9).
Fatty acids content of butter oil and its double-stage fractions (trials from
conducted. The stearin Sz0 of interesterified palm oil is 225% of its proportion in native palm oil. Melting point and cloud point of the olein are decreased, whereas the iodine value increases (Fig. 6.59 and Table 6.1 1). Figure 6.60 demonstrates the influence of fractionation on the melting point. This is caused by the change in the proportion of the triglyceride classes. In the olein fraction, the S3 triglycerides disappear for the most part (Fig. 6.61). The super olein has by far the highest proportion of triglycerides with two or three Butter oil
-N =
Native
- - H = S20
Solids content
ou
[%I
7
50 -
‘\
H
30 20 ,
,
100
5
\\
‘. 10
15
20
25
30
35
40
Temperature [“C]
Fig. 6.57.
Solids content butter oil and its double-stage fractions (trials from Table 6.9).
Modification of Fats and Oils
Palm OH (nrtive) (m.p. = 3O.S’C I.V. = 55.7) Fndknrtkn 3O’C
501 I.V. = lodim V d U m.p.= W n g point c.p. 8 ckud point 1.r. =dfn#*lunamt
20% Stearin Sm
801(Oblnom
(m.p. = 51.5’C; I.V. = 38)
(C.P. E 5’c;, 1.v.= 80.5)
irc
I
~ndbnrtfon I
-
wdll -17 (rn.p. = 2 T C ; I.V. 53)
30% (24% I.. )
Fig. 6.58.
(md&‘)
-
-17
(ap. 5’C: I.V. e3)
Double-stagefractionation of palm oil (after Haraldsson 1987).
unsaturated fatty acids. The solids content of the fractions listed in Table 6.11 is shown in Figure 6.62. For the mid-fraction of palm oil, PORIM demands an iodine value of 32-55, a melting point of 2340°C and triglyceride compositions as follows: C5d(C48+ C54) > 4 and C5*< 43. Naturally, these figure are valid only far Malaysian products. To serve as a starting material for cocoa butter replacers (see Chapter 6.2.3.5), these mid-fractions also require further modification. The fractionation trials shown previously start with equal fractions from stage I and reflect the influence of stage II. Table 6.12 shows the influence of different stage I temperatures with constant \ stage I1 separation temperature.
6.2.3.5 Cocoa Butter Replacers (Cocoa Butter Equivalents). The paramount property of cocoa butter is its melting behavior, which results from its triglyceride composition (see Fig. 4.122). CBE (cocoa butter equivalent) or CBS (cocoa butter substitute) offer choices in substituting for cocoa butter. A cocoa butter equivalent is defined as a fat that can be used in any proportion to replace cocoa butter in any recipe. Its physical and chemical properties are identical to those of cocoa butter. A cocoa butter replacer is a fat that must be used to replace at least 75% of cocoa butter in “chocolate” recipes. Its chemical and physical properties differ from those of TABLE 6.1 0 Palm Oil Triglyceride Classes Before and After Directed lnteresterification Proportion (mol YO)
s3
s2
u
su2 u3
Native
lnteresterified
7 49
32 13
38
31
6
24
Fats and Oils Handbook
5 02
Palm oil (native) (m.p. = 30.5'C; I.V. = 55.7)
lnteresterified palm oil (m.p. = 52°C; I.V. = 55.7)
I.V. = Iodine value m.p.= Melting point c.p. = Cloud point i.a. = of initial amount
Fractionation 20°C I
45% Stearin szo (m.p. = 58'C; I.V. = 34.4)
55% oiein 020 (c.P. = 2.7'C; I.V. = 76) I Fractionation0'C 73% (40% iaj Olein O2o-08 (C.P. = 4 ' C ; I.V. = 81.7)
27% (15% i.a.j Stearin Ozo-Sa (m.p. = 35'C; I.V. = 62.3)
Fig. 6.59.
Fractionation of interesterified palm oil (after Haraldsson 1987).
cocoa butter. Loders Croklaan company have listed the following requirements for CBE: a melting range equivalent to that of cocoa butter a fatty acid and triglyceride composition close to that of cocoa butter compatibility with cocoa butter processing of chocolate products is identical to that for cocoa butter-based products a polymorphic behavior that does not hinder tempering. It should therefore crystallize in the same polymorphic form as cocoa butter, i.e., in the P-modification the appearance and bloom-free shelf-life of chocolate products containing CBE should at least be identical to products based on cocoa butter alone adequate color and good flavor stability TABLE 6.1 1 Characteristics of Palm Oil and Its Fractions from Double-Stage Fractionationa Iodine value, IV
Melting point ("C)
Palm oil Olein O,, 020-S17 mid fraction O,,-S,, mid olein
55.7 60.5 53 63
30.5 5T 27 3T
Stearin S,,
38
51.5
aSource: Haraidsson (1 9871, T = thaw point.
Yield (%)
( % of initial)
Code
-
-
25 25
I\: A
37
80 31 69
125
20
-
(OF)
87 41T 81
B C H
Modification of Fats arid Oils
Solids content
503
[%I
80 60 40
-
20 -
,
0 0
10
20
30 40 50 Ternperatu re ["C]
I
60
70
Fig. 6.60. Solids content of the triglyceride classes of palm oil depending on the temperature (after Klein 1979).
To make a fat suitable as a starting material for CBE or CBS production, the fatty acid distribution on the glycerol is as important as the fatty acid composition itself. Because fractionation is a physical process that does not allow change in the triglyceride structure, only those fats that contain such structured triglycerides native in the starting material are suitable as raw materials for CBE production. These are primarily shea fat, Illi@ butter (borne0 tallow) and palm oil. All of them contain a relatively high portion of symmetrical SUS-type triglycerides. For very high quality CBE, wet fractionation is the method of choice because the products exhibit no tailing in melting
: r-----I Proportion [%]
:~u 50
20
10 0
Palm oil Fractions:
c Super olein A
Olein 0 2 0
N = Native
0 H = Stearin S20
s 3
Triglyceride class
Fig. 6.61.
Triglyceride classes of palm oil and its fractions (trials from Table 6.1 1).
Fats and Oils Handbook
504
Palm oil
Solids content
[%I
100
Fraction
-C = Super olein
80
- - A = Olein 020
- N = Native
60
- - B = Mid fraction - H = Stearin S20
40
20 0
5 10 15 20 25 30 35 40 45 50 55 Temperature
["C]
Fig. 6.62. Solids content of palm oil and its double-stage fractions (trials from Table 6.1 1).
TABLE 6.12 Characteristics of Palm Oil and Its Fractions from Double Fractionation
Fraction Palm oil s35 s33 s3 1 s29 s23
sl 9 035-s18 033-s18 031-s18
029-s18 035-s14 033-s18 031-s18 029-slS
O23 0 19
aSource: Deffense (1985).
Iodine value
53 59-6 1 59-6 1 59-6 1 59-61 60-62 60-62 60-62 60-62 58 59
Melting Point
Yield
("C)
('/OF)
(%)
(%of initial)
55 54 53 52 49 48 44 43 42 41 36 33 30 27
131 129 127 126 120 118 111 109 108 106 97 91 86 81
14 17 20 22 33 36 32 32 32 32 59 59 59 59
-
67 64
-
-
27.5 26.5 25.5 25 51 49 47 46
Modification of Fats and Oils
Liquid / solid content
505
[%I
100 80 60
Cocoa butter 40 20 0 0
5
10
15
20
25
30
35
Temperature [“C]
Fig. 6.63. Solids and liquid content of cocoa butter at different temperature (after Steiner 19551.
behavior. Today, improved processing may also makes such products available from dry fractionation (Willner et al. 1989). From the compositions shown in Table 6.13, it becomes clear that palm oil is suitable for CBE production because it has a relatively large content of SUS-type triglycerides. Its mid-fraction is used. This fraction contains mainly triglycerides with palmitic acid as the saturated component. From the table, it can also be seen that shea fat is much more suitable because its SUS triglyceride composition is much closer to that of cocoa butter. The search for fats that could be used in CBE production is commercially very interesting and has resulted in many patents. Table 6.14 lists some of these patents to make clear that a wide variety of raw materials have been studied and found useful for CBE production. The cooling curves obtained from dry fractionated palm oil mid-fractions and cocoa butter are quite similar (Fig. 6.64). If the solids curves of such fractions are compared with those of wet fractionated cocoa butter equivalents, it becomes clear that dry fractionation is scarcely able to achieve adequate products. Wet fractionation is superior. At present, the main solvents used in wet fractionation are hexane, acetone and 2-nitro-propane (Walkden 1988). The best separation sharpness can be achieved with acetone. The most unsaturated triglycerides are separated as olein at 0°C. The stearin is dissolved in acetone, recrystallized between 18 and 20°C or washed with acetone until the desired iodine value has been reached. Thus three fractions can be obtained, -60% of an oleic acid-rich fraction (IV 62-64), slightly more than 10% of a stearin (IV 12-14) and a mid-fraction. This mid-fraction (IV 32-36) contains >70% of symmetrical SUS triglycerides of which 60% is POP. A typical CBE does not exist; the composition varies depending on the desired use and the raw material chosen. Two examples are given in Table 6.13.
Fats and Oils Handbook
506
TABLE 6.1 3 Triglyceride Composition and Distribution of Cocoa Butter, Shea Butter, Palm Oil, Illipe Butter and Some Cocoa Butter Equivalents (CBE) Cocoa butter
Shea butter
Palm oil
lllip6 butter
CBE I
CBE II
32 28 36 2
39 22 35 2
Proportion (YO)
Fatty acid
C16:O palmitic C18:O stearic C18:l oleic C18:2 linoleic C2O:O arachic
25 37 34 3 1
7 39 50 4
2 81 <1 15
1 45 1 40 <1 11
-
45 5 40 10
-
28 14 50 8
-
-
-
82
80
Proportion (YO)
Trig1yceride types
s-s-s
s-u-s s-s-u
s-u-u S-U-S (U = linoleic) u-u-u
1
8 35 9 37 2
3 86 <1
8
1 10
<1
Composition of S-U-S-type triglycerides (Yo) Stearic-U-Saturated Stearic-U-Palmitic Palmitic- U-Pal mitic
27 40 14
35 7 <1
1 7 27
45 34 7
28 19 35
21 14 45
S = saturated fatty acid; U = unsaturated fatty acid.
CBE in chocolate only partially replace cocoa butter. The higher their proportion of POSt and StOSt, the better their miscibility with milk fat and their physical stability at higher temperature. CBE are tailor-made by the manufacturers following the application desired by the customer. Walkden (1988) gives examples for TABLE 6.14 Examples of Old Patents Proposing Different Source Materials for the Production of Cocoa Butter Substitutes Source fat Phulawara tallow Mohwrah fat Dumori fat Baku fat Palm oil Shea fat Lard Tallow Mutton tallow
Patent
U.S. Patent 3,084,049 U.S. Patent 3,084,049 U.S. Patent 3,084,049 U.S. Patent 3,084,049 British Patent 925,805 British Patent 893,337 German Patent 1,030,159 German Patent 1,030,159 German Patent 1,030,159
Modification of Fats and Oils
507
Temperature ["C]
30
25 Cocoa butter
20
15
Fig. 6.64. Cooling curve of a dry fractionated palm
10
1
0
2
Time [h]
oil mid-fraction and of cocoa butter (after Banks e t a / . 1985).
CBE that are standardized in such a way that no unintended crystallization occurs and a sharp melting point exists. The use of CBE is still not allowed in some European countries if the product is to be called chocolate. The opening of legislation on new product declarations will offer new potential for CBE.
25
Difference to solids content of cocoa butter [%-points] * . ,. :. .... VI
20 -
CBEs
15 -
10 -
.......................
5
0
-5 1 20
I
I
25
35
40
Temperature ["C]
Fig. 6.65. Difference in solids content at different temperatures of cocoa butter and cocoa butter replacers (after Walkden 1988).
508
Fats and Oils Handbook
6.3 Winterization Winterization is a simplified form of fractionation-simplified because it is not the separation of two fractions of similar amount, but the removal of minor parts of the oil only. These minor parts are high-melting triglycerides and/or waxes. In contrast with the other modification processes that are designed to improve the functionality of fats and oils, winterization is a process that serves mainly cosmetic purposes and offers better handling. If oils are stored at low temperatures (refrigerator), waxes, hgh-melting triglycerides and certain gums may separate as solids from the oil. On the one hand, this leads to an undesirable cloudy appearance, and many consumers may mistakenly think the oil is spoiled; on the other hand, it is less pourable if it contains too many of theses substances. Salad oils that contain larger amounts of waxes or high-melting triglycerides are therefore usually subject to winterization. In the production of mayonnaise, too high an amount of waxes may destroy the emulsion when the waxes crystallize. In margarine making, this is also possible but much less likely. Another kind of winterization is necessary if slightly hardened soybean oil is to be used as salad oil. Soybean oil (IV 130-140) can contain up to 11% linolenic acid. To remove this acid that negatively influences keepability, the linolenic acid and part of the linoleic acid are hydrogenated (see Chapters 6.4 and 8.4).For use as refrigerator stable, pourable salad ’oils, the higher melting part is separated by winterization. Depending on the iodine value, an olein yield of 80-90% is typically achieved. 6.3.0 The History of Winterization
The term winterization comes from the United States; in the old days, cottonseed oil was stored in large tanks outdoors. During the cold winters, the higher melting part flocculated and settled and the liquid oil was decanted. This decanted oil, the “winter-oil” was bottled and sold as salad oil. Such oil stayed clear in the refrigerator. 6.3.1 Separation by Cooling and Filtration
To imitate the above process in a controlled way on a technical scale, the neutralized bleached oil is cooled to 5-15°C and allowed to rest for up to 36 h. At that temperature, unwanted gums, waxes and high-melting triglycerides separate as crystals from the oil and are filtered off. If only waxes and gums are separated (e.g., in sunflower oil), the filtration of the oil may be very difficult due to the properties of the materials and their small amount. The addition of traces of bleaching earth may improve the behavior because the particles act as a crystallization aid in the beginning and as a filter aid at the end. After a first filtration, the oil usually passes a polishing filter to remove residual solids. Winterization temperature and time depend on the future use of the oil. All substances that would precipitate later at the storage temperature are removed. Naturally only oils that are still liquid at refrigerator temperatures are suitable for winterization. Usually, oils that are used in margarine, fats or similar products are not winterized.
Modification of Fats and Oils
509
6.3.1.1 The Process. Winterization can be conducted batchwise or continuously. In the continuous process, the oil is precooled countercurrently with the cold oil leaving the plant. It is then allowed to very slowly pass through some vessels with a flow rate that allows a total holding time of 8-16 h. Filter aids may have to be added before the precipitate is filtered off. The batch process differs only in that the oil does not pass through a holding vessel but stays in one batch instead. After crystallization, filtration is conducted batchwise (see Fig. 6.66). 6.3.1.2 Continuous Winterization Plant. The set-up of winterization plants is relatively simple (Fig. 6.67). They resemble fractionation plants. In continuous winterization, the oil is fed to the plant from an intermediate tank (A). The oil is precooled in a plate heat exchanger (B) countercurrently with cold winterized oil that leaves the plant and in turn is heated. Then it is slowly pumped through a cooler (C) (cooled with brine; usually necessary only for the start-up phase) and an intermediate vessel (E). For certain oils that do not crystallize well, a crystallizing aid may be added from a buffer (D) by means of a variable speed conveying worm. The flow rate must be adjusted in such a way that 4-8 h residence time in the vessel, maintaining cooling, are guaranteed. Then the mixture is pumped through two compartment tanks (Fa) and (Fb) equipped with slowly turning stirrers. At least the Oil hv= Winterization temperature t
t
t
Heat exchange, 25-3O'C
+
1
I I I
t
I Cooling
Batch, tw < t < tw+GK, 4-8 h
Cooling
I Settling t
LAddition of filter aid
I
Heat exchange (brine), 1520'C
+
Filtration
I
011
Batch, tw, 4-8h
I
t
<<< Filter aid
+
>>> Stearins, waxes
free of stearins and waxes
Fig. 6.66. Processing flow chart of winterization.
Fats and Oils Handbook
510
1 -1 I I
I I
I I
I I I
I
I
I I I I I I
I
SI =Steam in SO = Steam out
G
I
I I
8- _ _ _ _ _ _ _ _ _ _ _ _ J
Fig. 6.67. Plant for continuous winterization (redrawn courtesy of de Smet, Edegem).
first one of these is equipped with a tube coil that allows indirect cooling with brine to improve crystallization. Tank (Fb) retains the oil long enough to ensure proper crystal growth. A pump (G) then alternately feeds the two filters Ha and Hb. From there, the winterized oil is pumped into the storage vessel (J), passing through the plate heat exchanger (B). During winterization of sunflower and grape seed oil, the losses are low because the amount of waxes is small. When high-melting triglycerides have to be separated, such as in the case of cottonseed and olive oil, the situation is different. For these cases, the oil that is retained in the stearin may be as much as three fourths of the stearin. Table 6.15 gives some figures on the energy consumption of winterization. 6.3.2 Miscella Winterization
Oil losses during winterization may be minimized if solvent winterization is applied. To do so, the oil is dissolved in a solvent and subsequently cooled down. As a result of the dissolution with solvent, the stearin filtered off contains only one third of the oil retained in dry winterization. The increased yield has to be paid for with higher energy consumption mainly as a result of solvent removal. This can
51 1
Modification of Fats and Oils
TABLE 6.1 5 Comparison Between Parameters of the Dry and Wet Winterization Processes Winterization
Dry Consumption per ton of oil Steam Electrical energy Water Solvent Losses Cottonseed oil Crapeseed oil Olive husk oil Sunflower oil Process parameters CrystalIization time Filter area
(kg) (kWh) (m3) (kg) (Oh) (Oh) (Old
(YO)
(h) (m2)
100 15 20
0.4 0.4 0.9 0.2
30 400
Wet 3 00 15 30 7
0.1 0.1 0.3 0.1 8 40
clearly be seen in Table 6.15. The cloud point of miscella winterized oils lies -3°C below that of conventionally winterized oils. 6.3.2.7 Processing. As in conventional winterization, the miscella winterization process is similar in design to the equivalent fractionation technique (Fig. 6.68). Using continuous filtration, the process can be fully automated and runs continuously. Solvent removal is performed with the same process as applied in solvent extraction (see Chapter 5.2.3). 6.3.2.2 Plant for Miscella Winterization. Plants for miscella winterization resemble those for wet fractionation (Fig. 6.69). The oiYsolvent mixture is fed to the plant from an intermediate tank (A). It is precooled in a plate heat exchanger (B) countercurrently with the cold miscella that leaves the plant and is in turn heated up. It is then slowly pumped through a cooler (C) (cooled with brine). In miscella winterization, maturation time for the crystals is much shorter than in dry winterization. Therefore, one compartment tank (F) is sufficient to ensure complete crystallization. A pump (G) then feeds a filter H (for large plants, two filters, alternately). The oil miscella leaves the filter, is collected in (I) and passes through the heat exchanger (B) again. The wet stearin is collected (K) and subsequently heated (L) to evaporate the solvent in the stearin finishing evaporator (M). The desolventized stearin is pumped to a storage tank. The solvent is prepared for reuse (N). 6.3.3 Membrane Dewaxing
Typically, oils are dewaxed by means of winterization. A new process, membrane dewaxing, was developed -10 years ago and several plants have been built. Membrane
Fats and Oils Handbook
512
Oil
I
<<< Solvent
4I,
I
t
t I
Heat exchange (with winterized miscella) Heat exchanger (brine) <<< Crystalkation aid (for certain oils only)
t
Batch
Misblla
~~
s
// t
S = solid residue
qI+ ~~
I
Stearin, Waxes
Oil (free of stearin and waxes) Fig. 6.68. Processingflow chart of rniscella winterization.
techniques have been applied for a long time in the food industry, mainly in the dairy industry. However, it proved to be difficult to find membrane materials suitable for dewaxing because the waxes tend to block the pores. Patents for this new method were first granted to ASAHI Chemicals Ltd., and other companies have followed.
6.3.3.7The Membrane. To be suitable for dewaxing, membranes must meet the following requirements (Chayamichi and Kukuchi 1989): have sufficiently small pores to hold back the waxes, be chemically inactive against triglycerides, be physically passive against oil, no swelling, be pressure resistant from the inside and the outside, and enable reverse filtration or air back-blowing. Some membrane data published by ASAHI in the late 1980s are given in Table 6.16. The bundle membranes mentioned were held in a housing -1 100 mm in length and 100 mm in diameter. 6.3.3.2 Device for Membrane Dewaxing. The apparatus consists of a bundle of spaghetti-like membranes that are open on both ends (Fig. 6.70). The bundle is fixed in a stainless steel housing. The membrane tubes themselves are glued tightly
Modification of Fats and Oils
51 3
J
SI = Steam in SO = Steam out
1
w
Fig. 6.69. Plant for rniscella winterization (courtesy of de Smet, Edegem). together and to the inner wall of the housing (epoxy resin). This construction forms a hermetically tight inner chamber in the middle of the housing surrounding the tubes. This chamber (i.e., the outer side of the tubes) is flooded with the oil to be dewaxed. The oil permeates the tubes through the pores and flows off. The membranes hold back the wax, which is collected at their outer surface. 6.3.3.3 The Processing. The oil has to be cooled to allow for crystallization as in ordinary dewaxing [intermediate storage (A), coolers (B), crystallization vessel ( C ) ] .However, it is then not filtered but pumped through the membrane chamber (D). With increasing process time, the wax layer blocks the pores of the membranes and gradually decreases the flux rate. Once the oil flow becomes too low, the feed is stopped and air is fed to the center of the membrane, thus blowing off
Fats and Oils Handbook
514
TABLE 6.1 6 Technical Data of Microza Membrane Tubes Used for Membrane Dewaxing in the Microwin Processa Inner diameter Outer diameter Membrane effective area Pore diameter Maximum feeding pressure Maximum back washing pressure Maximum temperature
(mm) (mm) (m2) (m) (bar) (bar)
("0
2.0 1.1 6.3 0.2 3.0 3.0 80.0
aSource: de Smet, Edegem.
the wax layer from the outer surface of the membrane. After air back-blowing and flushing out the wax that has fallen down from the membrane, the oil feed is started again. The oil used to flush out the wax has a very high wax content and is filtered in a standard filter (E) (for total mass balance of a sunflower oil with 700 ppm wax, see Fig. 6.74). Filtration is easy because the wax content is high (Fig. 6.71). After a certain number of these cycles, air back-blowing and flushing out of the wax are no longer sufficient to ensure adequate throughput. In these cases, the wax is removed from the membranes by flushing with hot oil from the inside. The washing oil containing the wax is then recycled, i.e., united with the oil in (A) to participate in the dewaxing process again (Fig. 6.72).
(sealing the membrane against the chamber for the nondewaxed oil)I Fig. 6.70. Membrane filtration unit for oil dewaxing.
51 5
Modification of Fats and Oils
9
Fig. 6.71. Plant for membrane dewaxing. Oil to be dewaxed <<< oil from filtration with low wax content <<<
t
-
Membrane filtration
4-
1
5th
Oiltwax
I+ ll
Wax (with oil)
I
oil (with some wax) >>>
-+
d oil
+
+
Oiltwax in membrane
1 oil (with some wax) >>>
Fig. 6.72. Processing flow chart of membrane dewaxing.
+
Fats and Oils Handbook
51 6
Fig. 6.73. Flux rate of membrane dewaxing depending on time and number of cycles (after Chayamichi and Kituchi 1989).
Figure 6.73 shows the flux rate and the cycles of membrane dewaxing. The shaded area represents the location of measured points from many trials. The line represents the dependency of the flux rate on the mean value of these trials. The capacity of the plant continuously drops in the course of the cycles and regains the initial throughput only after cleaning of the membrane by back-purging with hot oil. At present, the cycles are longer.
6.4 Interesterification Interesterification allows the modification of the properties of oils and fats by redistrib ution of the fatty acids on the triglyceride without altering the fatty acids themselves. oil Wax content 700 ppm t
Membrane filtration
I
I/
Oil (99.3% of total) wax content < 20 ppm (cold test O'C > 48 h)
<<< Oil, wax content 500 m m <<< 0.63% of total
t
Oil
/It
Waxy oil (0.07% of total) wax content -10% (melting point -65'C)
Fig. 6.74. Mass balance of membrane filtration (after de Smet).
Modification of Fats and Oils
51 7
6.4.0. The History of lnteresterification
Interesterification offers the possibility of composing tailor-made fats that best serve the purposes of use (Baltes 1961). The process has its roots in the early 1920s, triggered by a shortage of consistent fats needed primarily for margarine making, Simple blending of vegetable oils with fats such as coconut or palm kernel oil was not successful because these triglycerides keep their characteristic physical properties, i.e., their melting points as well. Although the fat is (partly) soluble in the oil, these mixtures were not very homogenous. In contrast to blending, interesterification allowed the creation of homogeneous mixtures of triglycerides by incorporating the more saturated fatty acids of the fats into the oil triglycerides and vice versa. However, it became a real success only after suitable catalysts were found. This made possible the composition of a really new fat from two or more components, a fat with tailor-made properties. 6.4. I Principles and Effects 6.4.7.7 The Principle of Interesterification. Interesterification offers the possibility of modifying the properties of fats and oils by splitting them for a very short period of time into their components and rearranging them afterwards in a new order. This means that the pfocess of interesterification leaves the building blocks of the fats chemically untouched. Therefore, it has to be classified between fractionation, which is a purely physical process, and the hardening process, which is based on chemical principles. 6.4.7.2 Effects of Interesterification. Even interesterifying a single fat, i.e., interesterification with itself, may change its melting point in a substantial way. The graph (Fig. 6.75) gives some examples for this effect. It shows that the melting points of oils may increase considerably. However, the above example serves only to demonstrate the effect of interesterification because the process is not meant to simply increase the melting point of single oils. This is better done by hardening (see Chapter 6.5). Fats are not interesterified because of the relatively low increase of their melting points. As a matter of principle, interesterification of vegetable fats and oils increases their melting point, whereas the process leads to a decreased melting point of animal fats (Figs. 6.75 and 6.76). Along with the increase in melting point, there is an increase in the solids content at temperatures slightly below the melting point of the native fat. This causes a decreased solids content at low temperatures (Fig. 6.75). Thus, the properties over the whole temperature range are significantly changed, which is made clear in the figure. At times, interesterification is chosen to change the properties of oils and fats before further modification. A good example is the interesterification of lard (see Chapter 6.4.5), which is used either interesterified or fractionated additionally. The true potential and main application of interesterification, however, is the possibility of combining different fats and oils to yield end products that differ substantially
518
Fats and Oils Handbook
Fig. 6.75. Influence of interesterification on the melting point of oils and fats
from the blend of starting materials. The raw materials for interesterification mixtures are carefully selected according to their specific fatty acid composition (see Chapter 2.1). As mentioned before, interesterification of a single fat with itself already yields significant differences in its properties. However, the scope of variation is limited because the fatty acid spectrum is fixed. Using the variety of fatty acid sources in natural fats and blending them carefully, products can be tailor-
Fig. 6.76. Influence of interesterification on the solids content of oils and fats.
Modification of Fats and Oils
a4
t 10°C
519
at 20°C
32
80
"1
i" a
34
282
72
26
68
InteresterMed 24
64
0:lW
w:20
4o:w 20:w
m:40
0:lW 4o:w w:20 1W:O 20:w w:4o 1oo:o
Ratlo palm kernel 011 : coconut 011
Fig. 6.77. Solids content of palm kernel oil and coconut oil and their interesterified blends.
made with relatively low restrictions, somewhat similar to the possibilities offered by a construction kit. To make this clear, an example of the effect of interesterification of only two fats is given in Figure 6.77. It shows the solids contents of two oils, namely, palm kernel and coconut oil, and of their interesterification mixtures. It is only a very simple example, demonstrating the effects that can be obtained. Despite similar solids contents of the starting materials, the solids contents of the interesterified samples differ considerably. Carefully selecting the raw materials allows the production of end products with well-defined properties. After the reaction mechanism was fully understood, the commercial importance of interesterification grew, mainly in Germany where 200,000-250,000 MT/y are interesterified at present. The figure worldwide is estimated to be >1.5 MMT. 6.4.1.3 The Mechanism of Interesterification. Random interesterification allows the distribution to closely approach the statistical distribution of the fatty acids on the glycerol as described in Chapter 2.2. Influencing the equilibrium (directed interesterification) permits significant deviations from that statistical distribution. Because of the large number of different fatty acids in natural fats, the number of combinations, i.e., the number of different triglycerides that could be formed randomly, becomes infinite. Baltes (1975) offered calculation methods and examples. To illustrate the mechanism of interesterification, models are used with two or three fatty acids only. As in the explanation of the distribution theory in Chapter 2, these models are sufficient to explain the principles. Generally speaking, in a mixture of two esters, a dynamic equilibrium is created automatically as follows: RIOC-CORA + R,OC-COR,
t)RIOC-COR,
+ R,OC-COR,
[6.4]
520
Fats and Oils Handbook
The reactions within this equilibrium, i.e., the breaking of the ester bond and reesterification, are proceeding very slowly. Of course, as with all esters, the same type of reaction also runs within fats, the ester of the triple alcohol glycerol with three fatty acids. Here, however, each triglyceride molecule itself underlies an equilibrium because the three ester bonds within a molecule can have different fatty acids. Even with only two fatty acids bonded to the glycerol, the number of possible combinations is quite large Interesterifying two single-acid triglycerides with the fatty acid residues A and B all possible combinations are shown in Scheme 6.1.
Scheme 6.1.
Increasing the number of different fatty acids residues X to three, more than 20 combinations are already possible. Then, taking the number of fatty acids that occur in a natural fat, the number of possible combinations becomes vast. As noted above, the reaction rate is very slow. To obtain rates suitable for technical application, the reaction mixture would have to be heated to >300"C.This is not possible, however, because mglycerides begin to decompose at these temperatures. Therefore, the reaction rate has to be increased by a catalyst. The catalyst has the task of forming strong anions that attack the carbonyl carbon atom at the ester bond. This is facilitated by the different electronegativity of the carbon and the oxygen atoms, which leads to a partially positive charged carbon atom. This is amplified by the catalyst anion (see Schemes 6.2-6.4). The ester exchanges the OR,-group with the catalyst anion, which, in the end, equals an exchange of R,. The reaction with the ester fat proceeds in the same way. Within the dynamic equilibrium, there is a possibility for a back-reaction (Scheme 6.4B) to (Scheme 6.4A) or for the desired reaction path (Scheme 6.4C). In the case of fatty acids (Scheme 6.4C), an anion that is able to react with another triglyceride molecule is formed, thus continuing the chain reaction. Very shortly after the catalyst has been added at the appropriate reaction conditions, the dynamic equilibrium is reached; with triglycerides, this occurs after -1 min. The only difference between Scheme 6.4 and the reaction of triglycerides (Scheme 6.5) is that there are three ester bonds in a fat.
521
Modification of Fats and Oils
Scheme 6.2.
Scheme 6.3.
@ORb
+ Q R-C-O-Ra
93
ORb R-C-0-Ra
ORb @ R-CQ + 0-Ra
Scheme 6.4.
Na@
R~-c-o-CH,
8
R~-c-o-CH,
h-C-O-CH,
8
8
Scheme 6.5.
Usually substances that possess strong anions or form strong anions serve as a catalyst. These include sodium (metal), sodium hydroxide and sodium alcoholates (methylate and ethylate). Although sodium hydroxide and sodium alcoholates work according to the above principles, sodium and potassium as metallic catalysts require an additional reaction step before the reaction they catalyze. In this step, they react forming anions. There are always enough compounds present in an oil to serve as reaction partners, so that no special measures have to be taken to initiate the anion formation. The equilibrium can be influenced by separating reaction partners from the liquid phase so that they can no longer take part in the reaction (see Chapter 6.4.1.4). Once the catalyst is deactivated, the reaction equilibrium position is, in effect, frozen and the end products reflect the state of the equilibrium at that moment. 2 RCOOCH,
+ 2 Na + R-CO-CO-R + 2 NaOCH,
R-CO-CO-R + 2 Na
+ R-C = C-R
I
NaO
I
ONa
w.51
Fats and Oils Handbook
522
6.4.1.4 Directed Interesterification. In multiphase interesterification (liquidsolid), the interesterification mixture is held at a temperature at which certain higher melting glycerides crystallize and can no longer take part in the reaction because they a n separated from the liquid phase. The reaction continues to form these crystallized reaction partners in order to re-establish the equilibrium. This process continues until the mixture has become so poor in one of the components that the high-melting triglyceride can no longer be formed. This method of producing special end products is called directed interesterification and was proposed by Eckey (1948). During random interesterifkation, the products shown in Scheme 6.1 are formed from the starting material GA, and GB,. In directed interesterification, two fractions are formed from GAB,, which has a medium melting point because of its fatty acid composition. The first is GB,, which precipitates from the reaction mixture because of its high melting point as soon as it has been formed. Constantly, new GB, is formed to re-establish the equilibrium; this second GB,, however, constantly crystallizes because of the low temperature and precipitates from the reaction mixture. Thus it is no longer a reaction partner in the equilibrium; to maintain the equilibrium, GB, is again formed until there is no component B left in the mixture. As a result of this mechanism, first all GAB, and then all GA,B disappear and only GA,, which is liquid at the reaction
Random interesterification
I E-E%-E~-E~-E~ 50%
+ 12.5%
50%
each +
Scheme 6.6.
Directed interesterification
A high melting B = low melting fatty acid
Ef - E + E!
100%
33.3%
Scheme 6.7.
66.7%
523
Modification of Fats and Oils
TABLE 6.1 7 Triglyceride Classes of Native and lnteresterified Oils and Fat9 and of Noninteresterified and lnteresterified Blendsb (1:1) of Fully Hydrogenated Soybean Oil with Vegetable O i l s c 1:l Blends with hardened soybean oil
Single oils
Palm oil
n I
Soybeanoil Cottonseed oil
n i n I
Sunflower oil
n
Peanut oil
n i n i n
I
Rapeseed oil Palm oil
s3
s,u
su,
u3
s3
s,u
su,
u3
6 13 0 1 <1 3 0 <0.2 0 1 0 0
50 39 6 8 18 18 1 4 11 10
1
38 37 38 36 51 44 24 27 40 38 16 17
6 11 56 55 30 35 75 69 49 51 83 82
57 41 50 13 51 25 51 11 53 16 51 10 57 41
13 43 2 47 9 34 0.3 47 3 47 1 44 13 43
20 14 17 32 24 31 11 34 15 31 9 37 20 14
10 2 31 9 16 10 38 8 29 6 39 9 10 2
81 74 76 53 2 24 8 10 22 13
12 24 15 37 85 43 30 32 60 38
7 2 9 9 12 27 50 40 18 37
0 <0.1 0 0.7 1 5 12 18 0 12
1
1
Coconut oil Palm kernel oil Cocoa butter Lard Beef tallow
n i n i n i n i n i
aSource: Wieske (1969). bn = native, i = interesterified; figures are rounded. CSource: Zeitoun e t a / . (1993).
temperature, remains. Of course, this is more complex for natural oils and fats with their wider fatty acid spectrum, but the process follows the same principle. It is important to note that, above O"C, only triglycerides with at least two saturated fatty acids can precipitate from the fadoil mixture. This temperature has limiting importance because no catalyst that is sufficiently active at lower temperatures is yet available. 6.4.2 The Catalysts
Many catalysts are suitable for interesterification. A shared characteristic is that they have to able to form strong anions or that they must undergo a reaction them-
524
Fats and Oils Handbook
TABLE 6.1 8 lnteresterification Catalysts from Old Patents and Technical Data of Common Catalysts Reaction
Catalyst Alkali
Amount
Hydroxides
0.5-2.0
250
90
Hydroxides +glycerol Stearates Metals and alloys
0.05-0.20
6G160
30-45
0.2-1.0 0.1-1 .O
250 25-270
60 3-120
Alcoholates
0.2-2.0
5C-120
,5-120
Hydrides Amides
0.2-2.0 0.1-1.2
170 8C-120
3-120 10-60
(YO)
Temp. ("C) Time (min) ReferencdPatent Dominick, Nelson, Matil, U.S. 2,625,484 (1953); Holrnan, Going, U.S. 2,875,066 (1 959) Burgers, Mott, Seiden, US. 3,170,798 (1 965) Brockaw, U.S. 2879281, 1959 Dominick, Nelson, Matil, US. 2,625,484 (1953); Hawley, Dobson, U.S. 2,875,066 (1959); Holman, Going, U S . 2,875,066 (1959) Eckey, U.S. 2,558,548 (1951 ); Vandenval, Akkeren, U.S. 2,571,315 (1951); Mattil, Nelson, U.S. 2,625,483 (1953) Nelson, Mattil, U.S. 2,625,486 (1953) Nelson, Mattil, U.S. 2,625,486 (1953)
Technical data of common interesterification catalysts Metallically shiny, when gray oxide layer is removed, heavy reaction Sodium, Na with water to sodium hydroxide and hydrogen oxyhydrogen gas; easily oxidized, therefore stored under petroleum ,d, = 0.79 gkm3 Fp. = 97.8"C Atomic weight 22.99 White solid, usually as platelets or flakes; very hygroscopic, soluble in water Sodium hydroxide, NaOH to caustic soda solution d,, =2.13 g/cm3 Fp. = 318.4'C Molecular weight 40.00 White, usually heavily dusty powder; tendency to self-ignition, heavy Sodium ethylate, NaOC2H, reaction with water Fp. = 250°C (d); molecular weight 68.05; bulk density 0 . 2 4 3 kg/L; average particle size 0.01-0.3 mm White powder, heavy reaction with water, melts under decomposition and Sodium methylate, NaOCH, 2CH,OH release of methanol molecular weight 118.1 1 (incl. 2 methanol); bulk density 0.45-0).6kg/L; average particle size 0.07 m m
selves before interesterification to build anions that are then able to sufficiently polarize the C=O double bond. Because the choice of the appropriate catalyst heavily influences the success and also the cost of interesterifkation, most of the catalysts that have been developed are protected by patents. In 1978, Sreenivasan gave an overview of interesterifkation catalysts that are known mainly through patents (Table 6.18). It is important during interesterification that temperature is as low as possible and that reaction time is short. This is especially important if edible oils and fats are processed. From the large number of possible catalysts, the most common include alkali metals (mainly sodium), alkali hydroxides (mainly sodium hydroxide) and alkali alcoholates (mainly sodium alcoholate). These catalysts are described in the following.
Modification of Fats and Oils
525
There are no special requirements for the catalysts. The purity of the commonly traded chemicals is sufficient. The amount of catalyst required for the reaction varies between 0.1 and 0.01% wdwt. This differs substantially from the amounts that are given in Table 6.18 and reflects the progress of this technology during the past 30 years compared with the time when the patents were granted. The use of alkali metals as catalysts is still declining. Indeed they have the advantage that during deactivation (usually with water) fatty acids are formed in addition to alkali hydroxides or soaps, whereas during deactivation of alkali, alcoholate catalyzed reaction fatty acids monoesters are left. However, alkali metals are more difficult to handle and there is a risk of formation of unwanted by-products; this is not the case with caustic soda or alcoholates. The extra caution in handling the metals results mainly from the fact that the metal easily oxidizes and reacts with water to form hydrogen that is highly explosive in combination with the surrounding air. Alkali alcoholates can be handled without difficulty as long as they are stored under suitable conditions, i.e., air- and water-tight packaging; usually they are supplied in sealed plastic bags. Otherwise, alkali alcoholates react heavily with water; above 70"C, there is a strong tendency for self-ignition. Alcoholates form very fine dust, which is very aggressive. These alcoholates immediately react with humidity of the skin or mucous membranes to form alcohol and alkali lyes. These are very biting. Minimum handling and extreme caution are necessary when using alkali hydroxides. Although they are also very biting, they are easy to handle compared with the others catalysts; their only disadvantage is that they are very hygroscopic. Usually they are supplied in the form of flakes or platelets. Because of the lower temperatures that are applied in directed interesterification to allow the crystallization of certain fractions, this reaction runs much more slowly than higher-temperature single-phase interesterification. Therefore, to achieve an acceptable reaction rate there are special demands on the catalyst. Potassiudsodium alloys have proven especially active (Fig. 6.78). Potassium is a much better catalyst than sodium. The alloy can also be brought into the reaction mixture and dispersed there more easily because the eutectic of the alloy is liquid in the temperature range normally required for directed interesterification. 6.4.3 Choice and Preparation of Ra w Materials
hteresterification is conducted to produce fats that serve special purposes. To achieve these properties, adequate fatty acids must be present in the right quantity. The raw materials must be chosen according to the desired fatty acid composition and adequately blended (Table 6.19). Apart from their composition, there are some additional quality requirements that have to be met, primarily to avoid deactivation of the catalyst. Therefore, refined oils are usually used for interesterification, in this case, oils that are degummed and neutralized. Bleaching can be done before or after interesterification; however, because the oils usually darken during the process, it is recommended that they be bleached after interesterification. Deodorization is always done
Fats and Oils Handbook
526
Fig. 6.78. Phase diagram of Na/K alloy.
last. The main quality requirements, apart from being free of impurities such as gums, are given in Table 6.20. 6.4.3.1 Lost Catalyst with insufficiently Pretreated Oils. If the requirements given in Table 6.20 are not fulfilled, interesterifcation can still be done if the deactivated TABLE 6.19
Solids Content Before and After lnteresterificationd Solids content (%) Before interesterification
After interesterification
FaVoil
10°C
20°C
3OoC
10°C
20°C
30°C
Cocoa butter
84.8 54.0
0 7.5 8.0 15.4 2.5 26.7
52.0 52.5
74.2 26.7 58.0
80.0 32.0 38.2 67.0 19.8 51.6
65.0 24.8 57.1
6.0 39.0 27.2 49.7 11.8 50.0
35.5 21.5 1 .o 1.4 4.8 26.7
30.0 33.2 37.0
9.0 7.5 6.1
4.7 2.8 2.4
33.2 34.4 35.5
13.1 12.0 10.7
0.6 0 0
24.4
20.8
12.3
21.2
12.2
1.5
Palm oil Palm kernel oil Hardened Lard Tallow Palm oilkoconut oil 60:40 50:50 4050 Palm stearin/slightly hardened vegetable oil 20:80
-
-
aSources: Sreenivasan (1975), Coenen eta/. (1 974), Devlin and Walker (19601, Luddy eta/. (19551, Teasdale and Helmel (1965), Going (19671, Hustedt (19761, and Rossel (1975).
Modification of Fats and Oils
527
TABLE 6.20 Quality Required for Oils and Fats to Be lnteresterified Water Free fatty acids (FFA) Mineral acids Alcohol Hydroperoxides
<0.01 Yo <0.01 Yo Absent Absent POZ c 1
amount of catalyst is taken into account. This amount can be enormous as can be seen from the following examples. Alkali metal catalysts (Me) are deactivated following Equation [6.7]. In the calculations the molecular weight (M) for sodium is used: 2 Me + 2 H,O
+ 2 MeOH + H,
~6.71
One mole of water (18 g) therefore deactivates 1 mol of alkali metal (or 1 mol = 23 g of sodium), although a very reduced activity is retained due to the MeOH formed. In general, water deactivates (Mcatalyst metal/Mwater) . W = %wt/wt of deactivated catalyst (Mcataiyst ,dl 8) . W . l o = kg deactivated catalyst/MT oil with water content W (23/18) . 10 = 12.78 kg deactivated sodium/MT oil and per percentage of water content W If one assumes the usual amount of catalyst added, i.e., 0.01-0.1%, which is 100-1000 g/ton of oil, the amount of water shown in Table 6.21 would be sufficient to inactivate almost all the catalyst foreseen to speed up the reaction, unless an excessive amount was added. Similar calculations can be made for free fatty acids (Equation [6.8]) and hydroperoxides (Equation [6.9]) as follows: 2 Me + 2 RCOOH + 2 RCOOMe + H,
[6.81
2 Me + 2 ROOH + 2 ROOMe + H,
r6.91
TABLE 6.21 Amount of Inactivated Catalyst Using OilsFats at the Required Quality Limit Inactivated catalyst (kg)
Water content = 0.01YO Acid value = 0.01 Peroxide value = 1 Total
Usual amount for the reaction: O.O1-O).lo/o
Sodium
Sodium ethylate
0.127 0.091
0.377 0.241
Q921
Q L m
0.241
0.686 0.1 00-1.000
528
Fats and Oils Handbook
Assuming the molecular weight of oleic acid (282.5) as a reference, a fat with free fatty acids (FFA = %) and the acid value A deactivates the following: (Mcatalyst metal/Mfatty acid) . FFA = %wt/wt of deactivated catalyst (Mcatalyst ,,,/282) . FFA . 10 = kg deactivated catalyst per MT oil and FFA (Mcatalyst meta1/282) A = kg deactivated catalyst per MT oil and per unit acid number A 23/282 = 0.0816 kg deactivated sodium per MT oil and per unit acid number A (FFA = free fatty acids %wt/wt of the fat; A = acid number = 10 FFA; see Chapter 9.1). For hydroperoxides (POV = peroxide value) the relationship is as follows: Mcatalyst metal . POV 1 V = %wt/wt of deactivated catalyst Mcatalyst metal . POV . 10-3 = kg deactivated catalyst per MT oil and unit of PON MsodiumPOV . 10-3 = 0.023 kg deactivated catalyst per MT oil and unit of PON For calculations of other alkali metals and alkali alcoholates, the respective molecular weight has to be substituted for M. Because the effects noted above do not occur alternately but cumulatively, there is a total effect that is shown in Table 6.21 based on the minimum requirements of Table 6.20. It becomes clear that exceeding the limits may have considerable negative commercial effects or may cause deficiencies in the product. Either the amount of catalyst is insufficient to ensure proper reaction or the excess amount of catalyst needed leads to overconsumption. 6.4.4 The lnteresterification Process
The oils and fats to be interesterified have to be degummed, neutralized and properly dried to avoid catalyst deactivation as much as possible (see Chapter 6.4.3). The process (Fig. 6.79) itself is independent of the neutralization process, be it physical or chemical, continuous or batchwise. 6.4.4.7 Random Interesterification. Random interesterification is conducted under vacuum or in nitrogen atmosphere at 70-100°C. After addition of the catalyst, the reaction proceeds spontaneously, indicated by the development of a brownish color. The color is generated by oxidation products, formed with the traces of oxygen that always remain present; it has nothing to do with the interesterified or intermediate products. These colored substances are removed during bleaching. There are several methods that allow supervision of the process and should indicate whether the process is following the intended route. One usual measurement is the time required during controlled cooling for the oil to develop enough higher melting particles that it becomes cloudy. This time is compared with an empirically determined desired value. A second possibility is measuring the drop point as proposed by Kauffmann (1960; Table 6.22). Other methods were
Modification of Fats and Oils
529
Degummed, neutrallred
OillFat
Rarely done utualiy after interestenficalton
I
> 1 w ' C , > l h , <30hPa
Drying
I
70-1 OO'C Agltntion hadivation of c<< Water
Aqueous phase
>>> Effluent
I
Crude interesterhied fatloil
3
Refining
Fig. 6.79. Processing flow chart of interesterification.
described by Pardun (1976) among others. However, these are too complicated or too time-consuming to be applied for process control. When the reaction is finished, the catalyst has to be deactivated. In the case of alkali alcoholates (e.g., sodium methylate), water or diluted mineral acid is added while stimng takes place or steam is blown in. An aqueous phase is formed, which is separated from the oil. With the use of steam, the reaction mixture passes TABLE 6.22 Dripping Point of Fats/Oils Before and After lnteresterificationa Dripping Point ("C)
Tallow Coconut oil Cocoa butter Cottonseed oil Peanut oil Soybean oil Sunflower seed oil Tallow/coconut oil (50:50) Tallow/cottonseed oil (50:50) Tallowirapeseed oil (50:50) Tallow/peanut oil (5050) ~~
~
aSource: Kauffmann and Croethus (1 960)
Before
After
48.2 24.9 32.0 8.5 8.5 4.4 < -20.0 41.4 43.0 43.6 43.1
46.2 27.0 26.7 16.6 13.8 7.8 -1 0.0 34.5 27.5 30.0 37.3
Fats and Oils Handbook
530
through a stripper where the water is evaporated. The small portions of hydrogen that are formed during catalyst deactivation are sucked off with the steam. Alkali metals may be deactivated by steam that is blown in countercunently. The reaction with potassium is much more vigorous than that with sodium. Therefore, some trials were done to inactivate sodiudpotassium alloys with a mixture of carbon dioxide and water. Hawley and Holmann (1956) found that this led to a better yield because no soaps are formed under those conditions. The reaction mixture is worked up immediately after interesterification; this usually includes a bleaching step (see Chapter 7.3). These main steps should be viewed as the sum of a series of single steps that require repetition. Figure 6.80 shows a practical example, including the neutralization and bleaching steps, as the three processes are conducted one after the other in the same batch vessel. In can be seen that the interesterification step requires only little time compared with the entire sequence. 6.4.4.2 Directed hteresterification. If interesterification temperature is controlled in such a way that certain high-melting triglycerides crystallize and thus precipitate from the melt, these separated triglycerides can no longer take part in the reaction. They can no longer be part of the reaction equilibrium because they are not in the same phase. In the attempt to re-establish equilibrium, this separated fraction of triglycerides is produced again and again and separates again and again until the supply of one of the components needed is depleted in the reaction mixture. If the solids are removed, the process can be repeated at a lower temperature, yielding another fraction of higher-melting triglycerides.
I
Batch FilUng
1
30 min 10 min
45 min
10 min
10 min
I
45 min
Weterrpraying
1
10 min
10 min
I Heating up lo 1 W C
35 min
I
45 mln
W
10 min
I
Total cycb
10 min
amin 435 mkt
Fig. 6.80. Processing cycle of batch neutralization, interesterification, and bleaching.
Modification of Fats and Oils
531
Like the precipitate, the liquid fraction also has a characteristic composition so that directed interesterification can be used to produce both characteristic stearins and oleins. Because of the low working temperature (below the melting point of the separated stearin fraction), highly active catalysts must be used. These are finely dispersed alcoholates and sodium but especially sodiudpotassium alloys (see Chapter 6.4.2).The processing flow chart (Fig. 6.81) is generic but shows processing conditions that have been applied for directed interesterification of lard.
6.4.5 Plants for lnteresterification Interesterification can be conducted batchwise but also continuously. The classic process is batchwise random interesterification (randomization). A large batch vessel connected to a vacuum plant is normally used. In the case of alkali alcoholate, the vessel has an opening to feed in the catalyst. Generally, it has a stirrer, heatingkooling coils and, of course, an oil inlet and outlet. It must also be possible to fill the head space with nitrogen.
6.5.4.7 Plants for Randomization. The sketch of an interesterification batch vessel is given in Figure 6.82. The mixture is pumped into the vessel (up to 70 m3 content), evacuated (<25 hPa) and heated to >1OO"C. The temperature is held for at least 1 h to evaporate all water and to degas. After drying, the oil is cooled to 70°C and the vacuum is broken by nitrogen addition. Then the catalyst is dosed. In the
* Fatloil
I
Figurea for lard (continuous process)
Reaction Cooling
Crystallization
21'C, 30 SeC 27-28%. 150 soc
<<< cf& <*< H20
Catalyst inactivation ~
directed intbesterified FatlOil
LO,,~
Fig. 6.81. Processing flow chart of directed interesterification (data for lard from Sonntag 1982).
532
Fats and Oils Handbook
Fig. 6.82. Batch vessel for interesterification. case of sodium methylate, this is preferably done by means of a funnel with its outlet reaching deep into the oil. To avoid dust formation, the vessel is under vacuum and the catalyst is sucked in. To avoid oxygen entering the vessel, the funnel may be two chambered, one chamber acting as a lock. To be on the safe side, the funnel can be flooded with nitrogen. However, there is the question whether that adds value because working in a totally oxygen-free environment is not possible and any traces of oxygen are removed by the vacuum applied. In any case, protective glasses, gloves and a mask must be worn. If metallic sodium is used, the interesterification blend is pumped into an intermediate storage vessel. From there, it is pumped into the working vessel passing through a sodium press, which consists of a perforated plate. Its holes work as a bundle of nozzles through which sodium is pressed with 70-80 bar into the passing oil. Because this oil has a temperature of -13OoC, the sodium (m.p. = 973°C) is melted and dispersed into the oil. To keep the pipes sodium free, the metal is dosed only into the middle running. This means that the pipes are flushed with oil, sodium is then added and there is an afterwash with pure oil. The sodium is then dispersed into the oil in the form of droplets that must be fine enough to enable catalysis. To better distribute these droplets and to shear them down further, the mixture is run through a gyro-mixer. One can also pump through a series of perforated or slotted plates. In the sequence, every second plate would rotate at 1400 timeshin; the others are fixed. To ensure optimal effect, the sodium droplet size should be - 5 0 pm (Baltes 1975). 6.5.4.2 Plants for Continuous Interesterification. More and more plants for continuous interesterification are being built. The vessel is replaced by a reaction chamber (usually a reaction pipe) that is coiled or loop-shaped to require less space
533
Modification of Fats and Oils
n
NaOH 50%ig
Y&--=
Reaction Tube
/
rnin. 160°C
Oil/
Heater
Refining Centrifuge
Fig. 6.83. Schematic plant for continuous interesterification. and allow easier insulation. The pipe must have the right diameter and length to ensure the reaction time required while the reaction mixture is passing through. Outer heating must be possible to maintain the reaction temperature (Fig. 6.83). Usually caustic soda solution or sodium ethylate is used; it is mixed with the oil and reacts while being pumped through the pipe. This process is protected by patents that have been granted to Unilever. If caustic soda is used, neutralization and interesterification can be done together as an integrated process. 6.4.5.3 Plants for Directed Interesterification. The above plants were constructed for randomization. For directed interesterification, the reaction equilibrium must be intentionally disturbed in order to precipitate the desired products. Therefore, plants for directed interesterification must contain means for cooling. Because of the heat of crystallization, stimng and so forth, the chamber must be continuously cooled to keep the reaction temperature constant (Fig. 6.84). The interesterification mixture is dried and then mixed with the catalyst. It passes a mixer and after a certain reaction time enters a series of coolers/crystallizers. The catalyst is deactivated and the mixture is passed on to further processing. 6.4.6 Properties of lnteresterified Fats and Oils
Interesterification changes the melting and crystallization behavior of fats and oils. In interesterification of vegetable oils, the melting point is increased and that of animal fats is decreased (see Fig. 6.75), because the unsaturated fatty acids in vegetable fats are bound mainly to the 2-position, whereas the distribution after interesterification is random (see Chapter 6.4.1).Interesterification may so heavily change the properties of
Fats and O ils Handbook
534
Vacuum-dryer
Catalyst storage
Preheater
MlAWl
Coolers/Crystailizers Degassing
*aQ Crystaiiizers
I
Mixer
Heater
Refining
Fig. 6.84. Schematic plant for directed interesterification.
a fat that the end product no longer has anything in common with the starting material. An example of such behavior is seen in cocoa butter. Its melting behavior is dramatic d y changed by interesterification so that it is no longer suitable for the usual applications. Interesterifid cocoa butter does not melt in the mouth and even above 50°C still possesses some solids. It has lost the unique characteristics that make it infinitely pre ferred for some purposes (Fig. 6.85). This is a striking example only, of course, Solids content
[%I
native
Cocoa butter 60
20
25
30
35
Temperature
40
45
50
["C]
Fig. 6.85. Solids content of cocoa butter at different temperature (after Sreenivasan 1978).
Modification of Fats and Oils
535
because nobody would interesterify the high-priced raw material cocoa butter. Rather, sophisticated techniques are applied to other fats to make them cocoa butter replacers. In the case of lard, opposite effects, i.e., a real improvement of a fat’s properties can be demonstrated. In the U.S., lard is used in high quantities as a shortening. Interesterification changes its properties, thus improving the structure and volume of the baked goods. The main reason for this is a decrease in the share of palmitic acid bound to the 2-position (Fig. 6.86). The changes shown result in a different crystallization behavior. Native lard crystallizes mainly in the p-form, whereas interesterified lard forms P’-crystals. Changes in the properties are reflected in the cooling curves shown in Fig. 6.87. As mentioned above, interesterification of a single oil or’fat is rare; usually blends are interesterified because the effect is greater. Often two modification techniques are combined and oils are interesterified with hardened or semihardened triglycerides. Table 6.23 shows an example, namely, the properties of palm kernel oil, hardened palm kernel oil and their interesterified blends. The table clearly indicates that interesterification of hardened palm kernel oil ( h ) decreases its melting point, lowering it to the melting point of cocoa butter. Therefore it becomes a potential substitute for cocoa butter. Even if parts of the hardened palm kernel oil ( h ) are replaced by the hardened and interesterified component ( h J ,there still is an effect. A much higher proportion of (hi)than of native palm kernel oil is liquid in the mouth. The product is often used as a fat component in coffee whiteners but also for toppings and nondairy whipping creams (Going 1967). An example that clearly illustrates the changes of two different oildfats during interesterification is given by Lo and Handel (1983). They described interesterification of a blend consisting of 60% soybean oil and 40% beef tallow. This blend is
Fig. 6.86. Fatty acids bound to the 2-position of native and interesterified lard (after Filer e t a / . 1969).
Fats and Oils Handbook
536 0
60
5
e40
f
EN
t
20
10
Fig. 6.87. Cooling curve of native and interesterified lard (after Luddy 1955) and sunflower seed oil (blend of native and hardened; after Husted 1976).
proposed as an unhardened alternative fat blend for margarine. It becomes clear that the fatty acids are almost evenly distributed among the glycerol bonds, which means that approximatelyone third are bound to the 2-position. The solids content resembles the profile of two marketed U.S.margarines. Especially in the temperature range >20"C, this comes very close to common blends (Fig. 6.88). In Europe, interesterifkation blends are usually made from vegetable oils, fats and hardened vegetable oils and fats because of the demand for higher contents of unsaturated fatty acids. 6.4.6.1 Directed Interesterification. Directed interesterification allows special end products to be obtained by influencing the reaction equilibrium. A stearin-rich and an olein-rich fraction are being produced if the mixture would be split. Native lard has a low solids content at high temperatures. Interesterification allows the TABLE 6.23 Solids Content of Hardened Palm Kernel Oil, Hardened lnteresterified Palm Kernel Oil and the lnteresterification Products of Their Blend9
Palm kernel oil Hardened (h) Hardened and interesterified (hi) h/hi 50:50 interesterified h/hi 65:35 interesterified h/hi 80:20 interesterified aSource: Sreenivasan (1978).
Solids content (YO) at
Melting point ("C)
10°C
20°C
35°C
38°C
46.8 35.0 41.7 44.2 46.0
74.2 65.0 70.0 71.0 72.4
67.0 49.9 57.4 59.7 62.6
15.4 1.4 8.7 10.2 12.4
11.7 1.1 5.2 6.7 8.5
Modification of Fats and Oils
537
Proportion of fatty acid in 2-position [%]
40
30
20 10
Fig. 6.88. Changes in fatty acid distribution dependent on interesterification time (after
Lo and Handel 1983).
crystallization behavior to be improved, but does not improve temperature stability. To achieve this, tristearin would have to be formed. As shown in Figure 6.89, directed interesterification allows for such improvevent, i.e., end products with high temperature stability without introduction of foreign stearin. The plasticity is improved, thereby improving the baking performance. Both effects in one cannot be achieved by randomization. Solids content I%)
0
10
20
30
40
Temperature ["Cl
Fig. 6.89. Solids content of lard, native, randomized and directedly interesterified (after Sreenivasan 1978).
Fats and Oils Handbook
538
Chabanov and Topalova (1979) conducted some laboratory trials with lard. These practical results illustrate what has been theoretically described in Chapter 6.4.1. An extract of these results is demonstrated here. The reactions conducted were directed interesterification starting at 70-8OoC, followed by cooling and then maintaining the temperature. In addition to the composition and properties of the end products, the course of the reaction is interesting. The following figures show trials IV,VI,and VILl of Table 6.24. The reaction pathway starts with the left point on the abscissa always being native lard and is continued with the second point being the intermediate state of random interesterification (before cooling). The graph shows that the proportion of S3, i.e., the triglyceride with three saturated fatty acids, which crystallizes from the reaction mixture, rapidly increases after cooling from the reaction temperature of 70°C down to 28°C (Fig. 6.90). Then it asymptotically approaches a value of -24%. The proportion of the other components must change constantly because the mixture permanently becomes poorer in S and equilibrium must be re-established. If the final proportion of S3 is reached, a new dynamic equilibrium is in place, lasting as long as the boundary conditions remain unchanged. Table 6.24 shows that the amount of S3 is smaller for cooling to 20°C. This is due mainly to the reduced catalyst activity at such low temperatures. Also, at that temperature S,M-triglycerides already crystallize, thus participating in the highest melting fatty acids S (Fig. 6.91) that then cannot be used up exclusively by S3. If cooling is done in three steps, the highest S3 yield can be obtained. First, the main portion of S, triglyceride crystallizes at 28°C without the rival S2M being formed and competing for the same source of fatty acids S . The temperature of the following step to 20°C affects a further shift of the equilibrium. The rest of the S3 crystallizes (Fig. 6.92). Working at 0°C leaves the proportion of S3 almost equal to random interesterification. Instead of only S,, more mixed triglycerides are formed because these also crystallize at that low temperature. These results are summarized in Figure 6.93. TABLE 6.24 End Products of Lard lnteresterification with NdK-Alloy in Xylene at 70-80°C and Following lsotherrnical Reaction Timed Triglyceride types (relative %wt/wt)* Trial
I I1 111 IV V VI VII Vlll
Native lnteresterified (random) 30°C; 5 d 28OC; 3 d 2OoC;3 d 2OOC; 24 h 38°C -+ 28%C 10°C;5 d OOC; 12 d
+
aSource: Chabanov and Topalova (1979). *Low amounts of linoleic acid not included. S = saturated; M = manoenic; D = dienic acid.
M,D
SMD
M3
SM2
S2M
S3
6.8 7.9 7.5 10.1 8.3 9.7 12.7 11.4
15.9 13.0 9.4 7.4 9.2 6.7 5.9 8.0
16.8 12.6 17.5 16.3 16.3 19.5 19.4 19.7
30.8 29.0 21.0 19.0 19.8 14.9 14.0 18.4
23.5 26.0 19.0 18.1 21.4 15.0 27.0 32.8
3.7 8.0 18.5 24.1 19.8 27.0 16.0 7.6
Modification of Fats and Oils
539
Triglyceride classes [%]
35 I 304
q2
35
I
Lard 1-30
25 -
25
20 -
20
15 -
15
10 -
10
5-
5 ,
0
l
#
16
l
,
,
l
,
,
48
~
,
,
,
#
' 0
72
Reaction time [h]
Fig. 6.90. Change of triglyceride classes during directed interesterification of lard (trial IV from Table 6.24).
Using fractional crystallization techniques (see Chapter 6.2), an olein can be separated from palm oil, which remains liquid until 5°C. The temperature can even be decreased to 2.7"C if palm oil from directed interesterification is used. The shift in solids content that causes the effect is shown in Figure 6.94. Thus, it becomes possible to use palm olein as a salad oil, even if stored in the refrigerator. The comTriglyceride classes [%]
35
I
I
35
lnteresterified
Fig. 6.91. Change of triglyceride classes during directed interesterification of lard (trial VI from Table 6.24).
Fats and Oils Handbook
540
Triglyceride classes 35
[%I I
I
35
20 - 15 - 10
-5 I
1
3 Native
6
9
12
Reaction time [d]
lnteresterified
Fig. 6.92. Change of triglyceride classes during directed interesterification of lard (trial Vlll from Table 6.24).
bination of all three modification methods, in particular, still offers room for improvement of products and technologies.
6.4.7 Enzymic Rearrangement Enzymic interesterification is one of the main targets for many companies in the oils and fats business. Until today, nobody has managed to replace the convention-
Fig. 6.93. Triglyceride classes in interesterified lard (after Chabanov and Topalova 1979).
Modification of Fats and Oils
Solids content [%] 60 ..... ..,
541
lnteresterification of
50 40
30 20 -
.. . . .... ....
. ..
.
10
0
0
10
20
30
40
50
60
Temperature [“C] Fig. 6.94. Solids content of palm oil, native, randomized and directedly interesterified (after Sreenivasan 1978).
al interesterification processes. But enzymic rearrangement has been successfully applied on laboratory and pilot-plant scale and for some specialty products. Products can be obtained that cannot be produced with today’s means. The state of the art in the mid-80s is discussed by MacRae (1983), a discussion that is still up to date in terms of the potential offered by this process. Thousands of lipases exist and screening is ongoing. As an example, a publication by Hou and Johnston (1992) offers an overview on the lipase activity of more than 1200 cultures from the Agricultural Service Culture Collection. 6.4.7.1 The Principle of Enzymic Rearrangement. Lipases, which usually split triglycerides into glycerol, fatty acids, mono- and diglycerides, are used for enzymic interesterifkation.This reaction is reversible because the lipases are acting as catalysts in the reaction. Under certain circumstances, the synthesis of triglycerides from their building blocks can be effected; this potential, however, has not yet been used. The reverse reaction leads to interesterifcation because the fatty acids that were split off react again with glycerol. The reaction is carried out on the interfacial layer between the fat and the aqueous solution, the hydrated environment that stabilizes the enzymes. A water activity -0.3 enables the highest reaction rate (Touraine and h p r o n 1988). To keep the proportion of water small and to allow for the highest possible contact area with the fat, supports that are able to bind water are used. Kieselguhr, which is also used as support for metal catalysts in hardening, is an example. The enzymes are categorized as unspecific (Scheme 6.8), 1,3-specific (Scheme 6.9) and fatty acid specific (Scheme 6.10) lipases. The fvst group hydrolyzes the
Fats and Oils Handbook
542
Scheme 6.8.
E~
+--9
A-OH
[i -
A-OH
+
C-OH
+ EZ +
tr;
Scheme 6.9.
Scheme 6.1 0.
triglyceride totally (unspecifically), whereas the second leaves the 2-position untouched. Fatty acid-specific lipases preferably split certain fatty acids off the triglycerides. In the case of the mold Geotrichum candidum, for example, these fatty acids are long chained with a cis-double bond in the 9-position (Jensen 1974, Jensen and Pitas 1976, MacRae 1983, fatty acid A in Scheme 6.10). 6.4.7.2 Properties of Enzymically Rearranged Fats and Oils. Interesterification with unspecific lipases leads to end products similar to those of chemical interesterification, because the ester bonds are split unspecifically and the triglycerides are randomly resynthesized. MacRae (1983) showed this for the example of a mixture of coconut oil and olive oil. The total number of C-atoms per triglyceride was chosen as a characteristic to demonstrate the effect because these are very different in the two starting materials (Fig. 6.95). 1,3-Specific lipases preferentially attack the outer fatty acids because, for steric reasons, they cannot reach the 2-position. To date, no enzymes are known that specifically react with the 2-position. Bringing stearic acid together with olive oil for such a reaction (Fig. 6.96) shows that, as expected, the 2-position stays untouched, whereas the fatty acids in the 1- and 3-position are changed. Positional specific interesterification is of great interest because products that cannot be produced by means of classic interesterification can be obtained. Rearranging a mixture of 1,3-di-palmito-olein with stearic acid, for example, leads to an end product in which palmitic acid is replaced by stearic acid. By combining this method with fractional crystallization, however, inexpensive raw materials can be used for the production of cocoa butter replacers. To date, enzymic interesterification is carried out either discontinuously with the enzyme fixed to a support being suspended in the oil or continuously by pumping the oil over a fixed bed catalyst. Enzymes can be produced by precipitation on the support with the aid of a solvent (Coleman and MacRae 1980) or by drying an enzyme/support mixture (Matsuo et al. 1981). Immobilized enzymes can be stored if dried. They also can be used in the dried
Modification of Fats and Oils
Proportion + N = Native -x-
-
A = Alkali-catalyzed rearrangement E=Enzymic rearrangement
543
[%I
35 I
30
1
Coconut oil / olive oil (1:l) native and interesterified
251
h N
20
1510-
5t
25
30
35
40
45
50
55
Number of C-atoms in triglyceride
Fig. 6.95. Alkali and enzymic (Candida cylindricae) interesterification of a blend of coconut oil and olive oil (50:50; after MacRae 1984).
state; however, their activity increases if prepared by the addition of lO%wt/wt water (Coleman and MacRae 1980). Other patents recommend polyvalent alcohols such as glycerol (Tanacka et al. 1980). Usually the reaction is carried out with fat dissolved in a solvent (petrol ether) with the catalyst fixed to the hydrated support. Because of the temperature sensi-
Fig. 6.96. Enzymic interesterification of a blend of olive oil and stearic acid ( 5 : l ) with Rhizopas delemar (after MacRae 1984).
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544
Proportion [%] -T
= Trigiyceride
8o f l
* F = Free fatty acid *D = Diglyceride + M = Monoglyceride
* C = C18:O Triglyceride
20 0
0
2
4
6
8
10
12
14
16
Reaction time [hours]
Fig. 6.97. Enzymic interesterification of a blend of a palm oil mid-fraction and stearic acid with Aspergillus niger (after MacRae 1984). tivity of the enzymes, the reaction is carried out at t < 40°C. The catalyst can be reused. The effect is shown in Figure 6.97 with a mixture of a palm oil mid-fraction and stearic acid. Investigations with rapeseed oil were described by Thomas et al. (1988). They researched the incorporation of lauric acid into the triglycerides and the temperature dependency of the reaction. The starting materials were canola rapeseed oil and 5% trilaurin or lauric acid and pancreatic lipases (from pigs) that were fixed on diatomaceous earth. Other lipases such as Candida cylindracae and Rhizopus arrhizus had proven ineffective. The interesterification reaction runs stereospecifically so that lauric acid is exclusively incorporated into positions 1 and 3. During a reaction time of 72 h at 25”C, 10.4% of the fatty acids in these positions was replaced by lauric acid. Interesterification with lauric acid decreases the,oil’s cloud point from -8 to -13°C. With trilaurin, it decreases to -16°C. Reaction conditions for the stereospecific interesterification of palm oil are given by Muderhwa et al. (1989). Interesterifying palm oil with soybean oil (70%), rice bran oil (60%)and rapeseed oil (a%), products were obtained with very low solids content at 10°C (2.09, 4.80, and 2.57%, respectively). Even using palm stearin and soybean oil reduced the solids content down to 4%. In comparison with palm oil and its solids content of 40% at lO’C, this technique offers new possibilities for the use of this oil and particularly its stearin. The reusability of the enzyme is important for commercial application. A rough idea of the dependency of product cost on the reuse of the enzyme is given in Figure 6.98.
Modification of Fats and Oils
545
Cost [U.S. $/Moll
I
7 . ~ 6-
Enzyme cost
54-.
3-. 21- .
0 1 0
I
,
!
I
50
100 150 200 250 300 350 400 450 500
Re-usability [mol/kg] Fig. 6.98. The influence of reusability of enzymes on the production cost (after Kloostermann eta/. 1987).
6.5 Hardening At the end of the last century, only lard, tallow and marine oils were available in large quantities in Europe. These quantities of edible fats, however, were insufficient to satisfy the need of the population that had concentrated in the fast-growing cities during the industrial revolution. Tropical oils were relatively scarce and expensive. In the US.,the situation was similar but less critical because of the relatively large amounts of cottonseed oil available locally. Marine oils in the market had very bad keepability; they were not oils in today’s sense but train-oils with all of the negative properties associated with this word today. To produce bakery fats and especially the high quantities of margarine needed (margarine was beginning to boom), consistent fats were urgently needed in high tonnages at acceptable prices. Supply in those days came mainly from domestic sources; these delivered mainly oils not fats. Apart from that, a quality was required that allowed for long keepability without significant loss in quality. This was a demand resulting from increased industrial food production and the greater distances for shipping. It was during this time that the method of catalyzed hydrogen addition to the double bond(s) of the esterified unsaturated fatty acids of fats and oils was invented and quickly developed tu become one the important processes in food technology. This process allowed the adjustment of available sources of fats and oils to meet demands and drastically improved the keepability and taste stability of marine oils. In addition to fractionation and interesterification, hardening is the third process that enables the modification of the physical properties of oils and fats. With a yearly production of -4 MMT, it is the most important of the three.
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546
loo 80 60
40 20
80
60
40 20
0 1ooc
20°C
30°C
1O'C
20'C
30°C
Fig. 6.99. Solids content of some hardened oils.
Apart from edible fats and oils, technical triglycerides and fatty acids are also hydrogenated. A very detailed application-oriented review of today's state of technology is given by Patterson (1994); this review includes detailed information on processing for single oils. Figure 6.99 shows the scope of change in physical characteristics during hardening of common oils. 6.5.1 History of Hardening
In 1897, at Toulouse University in France, P. Sabatier and J.B. Senderens (1901) discovered that C-C-double bonds of organic molecules can be saturated by the addition of hydrogen. They proposed diverse metals such as copper, iron, cobalt and nickel as catalysts. Their first experimental procedure was to pass the evaporated organic compound over the catalyst together with hydrogen. This is a twophase reaction of a homogenous gaseous phase consisting of the two reactants carried out on a solid catalyst. The German W. Normann, working in Leprince & Sieveke's machine and oil factory in Herford, realized the potential of this new method. He developed the process further, especially postulating that oils and fats could be hardened without transferring them into the gaseous phase, which at the end would not have been possible, at least not in a commercially acceptable way. After sticking firmly to his idea against all objections, Normann managed to complete his trials successfully in 1901. A year later he asked for approval of a patent, which was granted in 1903. The spread of this patent has been compiled by DGF (Deutsche Gesellschaft fiu Fettwissenschaft 1978 to 1980; German Society for Fat Research), based primarily on
Modification of Fats and Oils
547
an article by Normann himself (1938). Some major steps are cited here as follows: 1905 1906 1908 1909 1910-1 1
Process introduced to England by Crosfields First trials in trials-plant at Crosfields First hardening of whale oil in Herford by Normann; large-scale trials at Crosfields First shipment of hardened cottonseed oil from Herford to edible fat manufacturers Process taken over by Procter & Gamble, Schicht in Aussig (Austrian Empire), Van den Bergh in Zwijndrecht (Holland) and Olwerke Germania in Emmerich (Germany)
By 1920, the new technology became well established after it had been proven that it could be used to modify edible oils and fats harmlessly. New markets opened to oils that had not been well used earlier. The soap industry also adopted the new method to harden industrial oils and fats as well as to produce certain fatty acids and their derivatives on a large scale. In successive years until about 1940, the producers learned how to influence the characteristics of the end products by varying the main reaction parameters, in particular, temperature, as well as pressure and kind and properties of the catalyst. In recent years, efforts have been directed mainly toward avoiding unwanted side reactions, such as trans fatty acid formation, by further improvement of the catalyst as well as the reaction conditions. The predominant target for the future is to develop enzymatic hardening for large-scale technical use, a process carried out by nature in the cow’s rumen. 6.5.2 Chemical and Physical Basis of Hydrogenation 6.5.2. I Reaction Mechanism. The trivalent alcohol glycerol, which is the basis of all triglycerides, is completely saturated at all its C-C-bonds and therefore does not react with hydrogen. Hydrogen is added only to the unsaturated bonds of the fatty acid chains. The mechanism is a type of electrophilic addition of hydrogen to the CC-double bond. The reaction proceeds in several steps according to (Scheme 6.1 1).
Scheme 6.1 1.
The knowledge of these steps is important to understand possible side reactions. These can largely be avoided by intelligent processing. The triglyceride molecules migrate through the oil. If unsaturated (Scheme 6.12), they are absorbed at the surface of the catalyst with their double bond.
548
Fats and Oils Handbook
Scheme 6.1 2. The complex formed enables hydrogen to bind to the double bond establishing a xcomplex (Scheme 6.13).
H Scheme 6.1 3.
This complex reacts further by addition of a second hydrogen atom (Scheme 6.14), saturating the former double bond.
Scheme 6.14.
However, as an unwanted side reaction, they can also react backwards to the old form by splitting off the added H-atom (Scheme 6.15).
Scheme 6.1 5.
The catalyst functions by lowering the activation energy, i.e., by splitting the reaction into steps, each having a much lower activation energy than the entire noncatalyzed reaction. In the fust step (Scheme 6.12), the formed complex is on a lower energy level than both of its components. The second step is hydrogenation itself. Because the sum of the activation energies of the catalyzed and noncatalyzed reaction has to be equal, it is important that one of the reaction steps proceed very quickly. The difference in the reaction rate of the noncatalyzed and the catalyzed reaction then results from the ratio of the reaction rate of the noncatalyzed reaction and the slowest step of the catalyzed reaction. The energy balance of the reaction is not changed by catalysis.
Modification of Fats and Oils
549
In addition to the desired main reaction, some side reactions are possible (Schemes 6.16 and 6.17). One such side reaction occurs if double bonds in polyunsaturated fatty acids are shifted when the second hydrogen atom is not added to the neigh boring C-atom but to the other end of a chain of conjugated bonds (positional isomerization). These reactions are very rare because conjugated double bonds are rare.
Scheme 6.1 6.
R),:...,p m” .....
- H + H-
H’
k
d
k
Scheme 6.1 7.
Although the molecule exists as a sc-complex (Scheme 6.13), the C-C double bond no longer exists, and the molecule can freely rotate around the temporary C-C single bond of the complex. If the reaction does not proceed by adding a second hydrogen atom and the double bond is rebuilt by splitting off the first hydrogen, the original cis double bond can be re-established or a trans double bond can be formed (Scheme 6.18). R
R
R
R
trans
Scheme 6.18.
Furthermore there is a slight chance that, viu back-reaction of the sc-complex, isolated double bonds are transformed into conjugated double bonds (Scheme 6.19) that are on a lower energy level.
Fats and Oils Handbook
550
H
&
&
.
-
R
H
H
Scheme 6.1 9.
In highly unsaturated marine oils, cyclization reactions can occasionally be observed (Coenen et al. 1967). Conjugated polyenic fatty acids form double unsaturated six-membered rings with one isolated double bond of another fatty acid. These are saturated after hardening. Good processing completely avoids this kind of side reaction. After the reaction is completed, the fat molecule desorbs and diffuses back into the oil (see Chapter 6.5.5.4). The nature and frequency of side reactions depend on processing conditions (see Chapter 6.5.6.2), type of catalyst and the oil/fat. 6.5.2.2 Reaction Kinetics. To characterize the progress of a reaction and in particular the degree of hydrogenation of fatty acids with different numbers of double bonds, one usually speaks of selectivity. This term was introduced by Richardson et al. (1924) to characterize the ratio of two reactions that proceed simultaneously.
linoleic acid + H, + oleic acid oleic acid + H,+ stearic acid The model has been extended by Bailey (1949) to linolenic acid
+ linoleic acid + oleic acid + stearic acid
and Albright (1965) generalized it to the sequence k3
trienic acid + dienic acid
k?
3
monoenic acid
kl
+ saturated acid
In this model, trienic acid stands for all acids with three or more double bonds. Selectivity takes into account that the single steps in this sequence proceed more slowly the more saturated is the oil/fat. Selectivity is the ratio of the velocity constants K, of the single reactions. The selectivity of single steps is marked by indices as follows:
Selectivities with reaction rate constants higher than k, have not yet been defined because they are of no practical use. If needed, they could be determined at any time. The composition of most oils and fats is very complex and the selectivity very difficult to determine. Even for simple systems, it can be calculated only with com-
Modification of Fats and Oils
551
puters. Therefore calculations are carried out very rarely. Allen (1982) described the calculations performed by Butterfield and Dutton in 1967 and gave an example for S21of soybean oil hydrogenation. Schmidt developed a graphical tool in 1968 to calculate selectivity. The relationship between linolenic and linoleic content therefore depends on the selectivity S3,. This allows (Fig. 6.100) the fatty acid composition that will (given a certain selectivity) result from hydrogenation to be read from a graph. As expected at high selectivity, i.e., high reaction rate constant k, (linolenic acid + linoleic acid), the linoleic content is much higher than at low selectivity. In a different format for soybean oil, Albright (1965) gave the ratio of linoleic and oleic acid, thus selectivity S,, (Fig. 6.101). As a measure of the progression of the reaction, the decrease in iodine value was chosen. The graph shows the linoleic oleic acid ratio for different selectivities. The greater the decrease in the IV, the more oleic acid has been formed; the curves thus have to be read from right to left. The higher S,, (= k,/k,, k, = linoleic acid + oleic acid), the greater the amount of oleic acid has to exceed the amount of linoleic acid. The consequences of different selectivities Szl = k,/kl can be described as follows: S,, = 0:
All molecules react immediately through to stearic acid, because k , >> k,. This reaction is possible at low pressure and using platinum catalysts.
Szl = 1:
Equal reaction rate for the reaction of linoleic acid to oleic acid and the reaction of oleic acid to stearic acid. 100
I
0
10
20 30 40 Linolenic acid [YO]
50
Fig. 6.100. Linolenic and linoleic acid content of hardened soybean oil dependent on the selectivity S,, (after Schmidt 1968).
Fats and Oils Handbook
552
S2, = 2:
Double reaction rate for the reaction of linoleic acid to oleic acid is twice that for the reaction of oleic acid to stearic acid.
SZ1= 50: A good nickel catalyst enables a fifty times higher formation of
linoleic acid than stearic acid. SP1>> 50: Practically all linoleic acid is hydrogenated to oleic acid before this is
transformed into stearic acid. The selectivity has a great influence on the end product (Fig. 6.102). With the same iodine value products can be obtained that behave totally differently. The solid content of the reaction product with S21 = 4 is distinctly greater above 20°C than for the SZl= 50 product; above 30°C it is many times greater. This corresponds well with the descriptions above. For the hydrogenation of soybean oil, Allen (1982) showed how the fatty acid composition changes in the course of hardening (Fig. 103). The rate constants in this case were k , = 0.367, k2 = 0.159,and k3 = 0.013. The amount of linolenic acid disappeared quickly (low k3, S,, = 12). The drop in linoleic acid concentration is also quite fast and is reflected in the increase of oleic acid. Stearic acid (SZl= 2.5) is formed only slowly. There have been many attempts to calculate decrease and increase of the different fatty acid concentrations during hardening. Kirschner and Lowrey (1970), working with the hardening of soybean oil, showed how exact such simulation techniques are today. They proved that predictions for simple systems can be made with satis-
A I.V. unite 15
10
5
0.20 0.30 0.40 Linoldc add / mnoenic acid [% m/m]
0.10
0.50
Fig 6.101. Oleic and linoleic acid content of hardened soybean oil dependent on the selectivity S2, (after Albright 1961).
553
Modification of Fats and Oils
Solids content [%]
0
20
10
30
40
Temperature ["C]
Fig. 6.1 02. Solids content of hardened soybean oil (IV 95) dependent on temperature and selectivity Szl (after Coenen 1976).
factory accuracy. The deviations of the calculated data from reality are very small (4%) and are constant over the whole range in their absolute difference. '
6.5.3 The Catalyst A catalyst is a substance that increases the reaction rate without influencing the energy content of the reaction and without being used up. No reaction that does not "" I
KI KI
0.169 0.367
-.
.
..
I
Llnd.nlc acid
100
1
200 Ructlon tlme [mln]
300
Soybean oil; 1 bar hydrogen pressure; 175'C; W h n i n - ' ; 0.02% Nickel catalyst
I
Fig. 6.103. Change of CI8 fatty acids during hydrogenation of soybean oil (after Allen 1962).
Fats and Oils Handbook
554
occur without a catalyst can be forced to run by a catalyst. However, reactions with a reaction rate close to zero can be stimulated to proceed at at least considerable speed. Hydrogenation of fats and oils is such a reaction. Contrary to the expectation from the above definition, the catalyst loses its activity during use because the circumstances in real-life processing differ from theory. It loses quality not only because of involvement in side reactions but, in particular, from mechanical stress, changes in physical structure and poisoning. In theory, all elements with a low atomic volume are suitable as catalysts. Such elements possess empty d-orbitals in the outer shell and thus a high affinity for electrons, caused by the short distance to the atomic nucleus. This leads to interaction with the n-electrons of the double bonds in unsaturated fatty acids. Of the chemical elements listed as suitable in Figure 6.104, i.e., those close to the bottom line, some have to be excluded for practical reasons; especially qualified are those of subgroup VIII of the periodic system. At present, nickel is used mainly in an amount of one hundredth of the weight percent of the triglycerides to be hardened. Other catalysts are the other members of the iron group, i.e., iron and cobalt as well as the platinum metals and copper. In addition to their function as catalysts, some of the platinum metals have the ability to dissolve immense quantities of hydrogen, which can have a positive influence. Colloidal palladium, for example, is able to absorb 3000 times its volume in hydrogen. The hydrogenation of fats and oils (always melted of course) is a heterogeneous catalysis, whose mechanism is described in Chapter 6.5.2. It implies that the reaction partners exist and react in three phases, namely, the gaseous hydrogen in liquid oil on a solid catalyst. Atomic volume of the solid elements 100 [cm3/grarnatom] 80 -
60 -
I
8)
40 -
20 0
1
1
,
I
I
11
21
31
41
I
51
61
71
81
Element [atomic number] Fig. 6.104. Atomic volume of the solid elements (after Hollemann-Wiberg 1971).
Modification of Fats and Oils
555
6.5.3.7 Catalyst Production. Primarily in use today are supported catalysts in which the catalyst is brought onto an inactive carrier (support). This allows one to control the mechanical stability and even distribution of the catalyst as well as to influence the reaction by changing the surface of the support. It has to be kept in mind that only part of the catalyst metal is available for its true purpose. To increase this part as much as possible, the surface of the support plays an important role; usually this surface is very porous to yield a high surface area supporting a finely dispersed catalyst. The catalyst metal is usually located in the pores, which have greatly varying diameters. Assuming a typical triglyceride molecule to have a spherical form, its diameter would be -1.5 nm. Only that part of a pore that has around twice the diameter of the triglyceride molecule would then be operative, e.g., those pores with a diameter of -3 nm. It is therefore of major importance to find a good compromise between large surface and pores of adequate diameter. Different opinions exist concerning the condition and kind of the catalyst metal itself. In his theory of the “active points,” Taylor (1925) postulated that those nickel atoms that protrude farthest from the metal surface have a higher degree of “unsaturation” and are thus best suited to forming a complex with the C-C-double bond. More recent theories (Morgantini ,1982) assume that the complex is formed by something like an absorption of each of the two C-atoms in the double bond to one nickel atom. The distance between the C-atoms then is 0.273 nm, approximately that between two Ni-atoms, 0.247 nm. In the application of new production processes, an attempt is therefore made to adjust the distance between Ni-atoms to 0.273 nm. This is easier to achieve with supported catalysts than with carrier-free catalysts. 6.5.3.7.7Support-free catalysts (wet reduction). To produce a catalyst via wet reduction, a nickel salt that is suspended in melted fat has to be reduced. The temperature of reduction has to be so low that the fat neither starts to boil nor decomposes. Additionally, no substances must be formed that cannot be removed from the melt or removed only with difficulties. Nickel salts meeting these demands are organic salts such as nickel formiate, nickel acetate or nickel oxalate. When heated, they decompose into water, carbon dioxide and hydrogen, all compounds that can be removed easily. As a common process, the decomposition of nickel formiate is mainly applied. Ni(OOCH), . 2 H20 4 Ni + 2 CO,
+ 2 H,O + H,
[6.10]
Nickel bound in nickel formiate is reduced, undergoing decomposition. During p r e cessing, nickel formiate is mixed in a vessel that contains two to four times its weight in fat or semihardened oil. The mixture is heated up to melt the fat and to expel crystal water at 180°C.The temperature is then increased and kept at 250°C for -2 h to complete the reaction. The endpoint is determined via activity measurement of the catalyst produced. To sweep out carbon dioxide, water, and hydrogen, nitrogen is passed
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556
through the reaction mixture while it is stirred slowly. Sucking off the volatile reaction products by vacuum has also been applied (Huge1 1937) but has not proven successful. The fat, a partially hardened oil, is completely hardened during this process by the hydrogen generated and the hydrogen passing through the mixture. The exothermic reaction delivers part of the energy required to decomposethe nickel formiate. In case the temperature is not controlled carefully and kept in a narrow range, the reaction is too vigorous, and the nickel particles formed are too small as a result. These are very difficult to filter off and have negative influence on the quality of the catalyst. Usually, kieselguhr is added as a filtration aid after cooling to -1OO'C (Fig. 6.105). To prevent oxidation by air, the catalyst is embedded in fat. The fat that was used as a solvent during nickel formiate decomposition is used for this purpose until its quality has suffered too much during processing. At that point, it is filtered off and replaced by fresh fat. The catalyst is sold in blocks, flakes or granulate whereby filter aid may be added. The precursors of fat-free catalysts that are reduced at 300-500'C with hydrogen in a countercurrent process are sold with 65-85% purity. During their first use, they are completely reduced by the hydrogen formed in the reaction. These catalysts are no longer common. One of the reasons is that nickel from this process often turns into a colloidal state, thus heavily reducing filterability. In this case, huge amounts of filter aid have to be added increasing cost, decreasing throughput and lowering yield. Fat or slightly hardened dl I
+ L
I
Fig. 6.105. Production of a support-free catalyst (wet reduction).
Modification of Fats and Oils
557
6.5.3.1.2 Nickel carrier catalysts (dry reduction). For the production of nickel support catalysts, a soluble nickel salt is brought onto the support or a nickel salt is precipitated onto it. This mixture is dried, reduced to the desired particle size, and the catalyst is activated by reduction with hydrogen. In practice, there exist several methods of dry reduction as well as several starting materials. As a carrier, mainly purified diatomaceous earth such as kieselguhr is used. These are supporting skeletons of marine algae from the tertiary period that allow nickel to be finely spread over a large surface (Fig. 6.106). The diatomaceous earth is dried and washed. After washing, it is dried again and all organic compounds are removed by calcination (Table 6.25). The distribution of guhr particle size is important to influence the end product (Fig. 6.107). Particles that are sintered by the high calcination temperature are removed by air separation. The calcination process should not exceed 880°C; otherwise, the amount of sintered material becomes too high. The choice and preparation of the guhr heavily influences the quality of the catalyst. The simplest way is to impregnate the carrier with a nickel salt solution that is as concentrated as possible. However, even by applying such a solution, the nickel concentration on the surface is very low after drying and reduction so that the operation has to be repeated many times. As a consequence, however, the surface structure of the carrier is negatively influenced. It is much more common to precipitate the nickel from a solution on the carrier as a hydroxide and filter them off together. The cheapest available nickel salt for this operation is nickel sulfate. It has the disadvantage that catalysts produced from nickel sulfate promote side reactions to iso-oleic acid if not washed completely sulfate free. Therefore, nickel nitrate is mainly used at present. Adding caustic soda or
Fig. 6.106. Nickel support catalyst (courtesyof Unichema International, Emmerich).
Fats and Oils Handbook
558
TABLE 6.25 Typical Composition of Kieselguhra Si02 Cr itabolites
(%) (%)
Fe203
(Oh)
A1203
( OO/
CaO MgO S Organic residue Particle size Sutface area Pore diameter Absorptive capacity
(%)
1
(YO)
(%)
(Yo) (pm) (m2/g) (pm) (%)
70-90 2-25 2-8 0.5-8 0-1 0 0.1-1 0-1.3 0-5 540 2C-50 2-5 -200
dependent on oven temperature
dependent on oven type and duration of calcination dependent on oven temperature (average22) (average 40) (average 3.5)
aSource: Klauenberg (19861, courtesy of Unichema International.
preferably a sodium carbonate solution, which also has an alkaline reaction, nickel hydroxide is precipitated and filtered off together with the carrier. It is not important in which sequence the reactants are added. From the kieselguhr, soluble silicates that also form nickel silicates are present. The configuration of the precipitate can be influenced by the concentration of the solutions and the pH. The residue from filtration (nickel hydroxide and carrier) is resuspended several times in water, filtered off and, at the end, dried and reduced at 350-5OO'C (Fig. 6.108). The nickel silicate that is formed during the process works as a kind of glue (adhesive) between kieselguhr and the nickel salt and improves the adherence of the catalyst
Guhr partlcle size clam
Fig. 6.107. Typical particle size distribution of a kieselguhr (after Klauenberg).
Modification of Fats and Oils
559
Kieselguhr c
<<< Base (NaOH. NaHCO, or NaEO,) <<< Nickel nitrate-solutiorr
c Ni(0Hh Precipitation
I
t < 800'C
Q Air classification
support
Filtration
I
I
Washing
I
Cooking, 60-90 min
I 1
I Drying
120-180°C
I
Support catalyst
Fig. 6.108.
Production of a nickel support catalyst.
metal to the carrier. Because the nickel catalyst is pyrophorous, it has to be covered with a coating of fat. The properties of the finished catalyst depend mainly on the geometry of its surface, i.e., of the surface of the carrier. To obtain the highest possible share of optimal catalyst particles, attempts are presently being made to introduce synthetic carriers that already possess the optimal geometric layout or that develop it during production. These catalysts have especially uniform particles. Such developments, however, are not yet ready for the marketplace. X-ray analysis showed that nickel in good catalysts exists in the form of cubic crystals that contain not more than 10 atoms. They are attached to particles of 2-10 pm. Without a carrier, such a good distribution, which enables the highest catalyst efficiency, would not be possible.
6.5.3.1.3 Other catalysts. Other less common catalysts include Raney nickel, copper and the precious metals. Raney nickel is produced by dissolving the aluminum with caustic soda from a nickel aluminum alloy (50/50 to 80/20) as an aluminate. Amorphous nickel with a high surface area results. Raney nickel as a catalyst, however, is more common in organic chemistry because it bears no advantage over common nickel catalysts in the hardening of oils and fats. This is also true for all other Raney-type catalysts, which were described by Mukherjee et al. (1973, who tested mainly granulated aluminum alloys of chromium, nickel, copper and palladium that were activated by alkali. Their only remarkable characteristic was their reaction rate, leading to a reduction of 40-60 IV units within only 2-4 min. Despite some interesting effects, copper has not found its place as a catalyst to date. Okkerse er al. (1967) were able to prove that, during hydrogenation of soybean
Fats and Oils Handbook
560
Lindeic acid I%]
Fig. 6.109. Linolenic and linoleic acid content in soybean oil hardened with Ni and Cu catalyst (after Okkerse eta/. 1967).
oil (relatively rich in linolenic acid), the linolenic acid content could be reduced to only 2% leaving 49% of the linoleic acid in place. In contrast, nickel catalysts reduced linoleic acid to 28%. This advantage, however, could not make up for disadvantages such as increased efforts to punfy the end products (Fig. 6.109). Copper indeed is a catalyst with higher S32 selectivity than nickel. From Figure 6.100, S32for copper can be estimated to be -11, whereas S,, for nickel is -3.5. It is important to consider that with today’s catalysts an increase of selectivity goes hand in hand with an increase in trans fatty acid content. The use of precious metal catalysts fails in mass production such as hardening because of their price, as long as almost total recovery cannot be ensured. Despite an activity that is up to a hundred times higher than that of nickel, their use is worthwhile only for special applications in which the usual catalysts fail. These catalysts are well investigated and will have a chance in the future only if they allow the manufacture of products with dramatically improved properties. Cecchi et al. (1979 and 1980) reported the hierarchy of activity of different catalysts on different carriers. At 180°C on alumina as a carrier, they detected the following sequence for rape oil: Pd > Pt > Rh > Ni > Ru with the activity of palladium eight times higher than that of nickel. Other authors have reported an 80 to 120 times higher activity for that pair of catalysts (Zajcew 1965). Other carriers showed similar ratios. For the resistance against poisoning, Cecchi et al. (1980) noted the following sequence: Pd > Rh > NiFe > Ni >> Cu-Cr. Caceres et al. (1985) investigated gold as a catalyst for canola rape hydrogenation. The reaction rate was only one thirtieth that of nickel, and the trans by-production higher. The only advantage that gold offered was to reduce linolenic acid totally with much lower trans fatty acid formation than observed with nickel. The search for better catalysts is ongoing. In the foreground is the further improvement of selectivity for higher quality fats.
*
Modification of Fats and Oils
561
Copper chromite has been investigated frequently during the recent past. Johannsson and Lundin (1979) investigated the influence of time and hydrogen pressure. Gargano (1982) explored the reaction mechanism and Kalska (1982), the influence of the erucic acid content in HEAR rape oil. Even more intensive work has been conducted for copper. Rozendaal (1979, preferred elimination of linolenic acid), Mounts et al. (1978, influence of H,-pressure), Johansson et al. (1980) (production of a catalyst fixed to silica gel), Koritala et al. (1981, trialkinsilane-activated Cu catalysts), Chou and Cheng (1981, selectivity compared with nickel), Moulton and Kwolek (1982, hardening of soybean oil with stationary Cu-catalyst), Heldal and Mork (1982, poisoning with chlorine-containing substances), and Snyder and Scholfield (1982, reuse) all contributed. As noted above, palladium has been known as a catalyst for a long time. To date, no advantages could be shown that would justify its use even disregarding its enormous price. This has been confirmed by Ray (1985). The use of different solvents has not brought a breakthrough; however, the trans fatty acid content could be lowered (Hsu et al. 1986). Research in this area is more and more directed toward complexes that either work as a catalyst or, after decomposition, enable very fine distribution of the catalyst metal. Berglund and Anderson (1984) researched rhodium phosphin complexes, and Koritala et al. (1985) determined the selectivity of palladium-acetonylacetonid complexes; neither study influenced today’s technology. The same holds for the work of Anderson and Larsson (1981), which found that palladium-phosphin and palladium-pyridine complexes account for speedy hydrogenation of polyenes but only slow hardening of monoenes. The complexes with a single ligand that are best researched are the carbonyls. Ucciani et al. (1982) ascribed unique partial hydrogenation properties to cobalt that originates from thermal decomposition of the cobalt pentacarbonyl complex. Diosady et al. (1984) compared chromium pentacarbonyl to nickel and stated that fewer rrans isomers develo@d using the complex. Possible reaction mechanisms of carbonyl complexes (with iron, cobalt and chromium) were given by Frankel (1979). The study of very unusual catalysts such as trialkyl-aluminium-copperstearate, synthesized by letting copper stearate react with triethylaluminum (a soluble catalyst) did not bring tangible advantages except a better selectivity in the sense that linolenic acid in soybean oil was predominantly hydrogenated. All results of catalyst research have one thing in common, namely, that all of the various catalysts may be advantageous in one or the other case, i.e., one or the other property of the hardened oil or fat. However, in the sum of all advantageous properties and especially in economic terms, none can match today’s most common catalyst, nickel. Therefore, there is no reason at this date to replace this reliable, proven catalyst. In addition, nickel itself is the subject of ongoing research, with the target of finding new methods of catalyst production that would lead to improved quality and properties. An example of such alternative production methods is a patent of
-
Fats and Oils Handbook
562
Me(N03), X 8 HZO
Na,C03
AYNO3)3 X 9 H20
- + c I
I
4-
Dissolving (Zmolar)
Dissolving (Zmolar) 4-1
4-
Precipitatingmix& salt
Washing
110%
350.C. 20 h
400-470'c
Catalyst
Fig. 6.110. Production of a novel
(USpatont 3896.053.1975)
nickel catalyst (after Broeker 1975).
Broeker (1975) (Fig. 6.110), which claims a new way of precipitating the catalyst metal together with a precursor of the carrier.
6.5.3.2 Recycling of Catalyst. Apart from the technically unavoidable losses, catalysts are not depleted during use, but remain almost completely present even when their loss of activity indicates that they can no longer be used. Reprocessing is required to recover the metal part of the catalyst, and almost complete recycling of the metal is possible. After filtration, spent catalyst contains -50% of its weight in fat. This is usually recovered by solvent extraction (hexane) and used for technical purposes. The extract-
>>> Misceila >>> R=Soiiiresldue F = Filtrate
I
I
R
R
<<< Mineral acid or a m n i a c<<
c
I
Technical fat
I ~ i s s o ~ n p n i d c e1i I Filtration
I
Catalyst production e
R
I
Spent support
3
Waste
Fig. 6.1 11. Recycling of spent nickel catalyst.
Nickel salt
Modification of Fats and Oils
563
TABLE 6.26 Data on Structure and Texture of a Nickel-Support Catalysta Support material (kieselguhr) Particle size Surface area Bulk density Catalyst (Pricat) Particle size Surface area Specific nickel surface area Nickel crystallite size Mean pore diameter**
5-1 0 10-20 100-1 30
(m)
(rn2/kg) (gA.1
5-1 0 100-1 90 90-1 50 2.5-5 2-1 0
(nrn)
(m21g)
( d i g Ni) (nm) (nm)
"<5 nm = optimal activity; >5 nm = optimal selectivity T y p e Pricat, Unicherna International, Ernmerich.
ed residue contains 25-30% of the carrier (and filter aid) and 15-20% nickel. Nickel is dissolved from this matrix with mineral acids or ammonium complexes; it is purified and reused for catalyst production (Fig. 6.111). More than 97% of the nickel is recovered. In current practice, suppliers take back spent catalyst for recycling. 6.5.3.3 Examples of Catalysts in the Marketplace. To give an impression of catalysts in the marketplace, physical data and characteristics of use are given for a typical catalyst. A detailed survey of catalysts was made by Patterson (1994). Table 6.26 shows textural and structural data of Pricat. Besides the catalyst itself, the form in which it is traded may also be of interest (Table 6.27). TABLE 6.27 Technical Data of a Typical Nickel-Catalysts Size (mm) Pellet thickness Pellet diameter Flake thickness Bulk density (kg/m3) Pellets Flakes Composition (O/O wVwt) Nickel content (average) Solid fat content Carrier content Consumption (kg NiIMT oil) (average for fresh catalyst) Vegetable oils Fish oils Fatty acids
2.5-3.0 6-7 1-1.2 850 500 22 f 0.5 -65 -1 3
0.05-0.3 0.3 -1.0 0.3 -1.5
aType Pricat, Unicherna International, Emrnerich.
Fak and Oils Handbook
5 64
By way of the catalyst, -60% of its weight is dragged into the oil/fat to be hardened as hard vegetable fat of -60°C melting point. Compared with the usual batches to be hydrogenated, this amount is so small that it can be neglected. In this context, it is important to use a vegetable fat so that the catalyst can also be used in locations where consumption of animal fat is not allowed for ideological or religious reasons. Table 6.28 gives some examples for fats hardened with the above described Pricat. 6.5.4 Hydrogen Raising
Hydrogen raising plays an important role for hardening plants. On the one hand, its price substantially influences the commercial bottom line result of the operation; on the other hand, its purity sets the limits of quality. The technology of hydrogen raising has changed greatly compared with times past. In addition, progress has been made (especially influenced by fuel technology for rocket engines) in the safe transportation of hydrogen, which can now be shipped anywhere without real risk. This gives the opportunity of purchasing hydrogen in the desired quantity instead of producing it. For high-capacity plants, purchasing hydrogen is not commercially viable at the moment. However, their hydrogen-raising plants can be adjusted to base-load production, purchasing only to cover peaks. This enables TABLE 6.28 Hardening of Different Oils with a Typical Nickel-Catalyst Catalyst conc.
Reaction Temp. ("C)
Press. (bar)
Time (mid
0.09 0.09 0.20 0.09 0.09 0.09 0.45
180 180 180 180 180 180 150 180
3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5
40 150 40 45 100 40 55 90
Recent type catalyst"
Nit
("Ci
(kPa)
(mini
Soybean oil
440 440 65 440 440 110 65
120 120 180 120 120 180 180
400 400 150 400 400 400 300
25 25 40 18 18 11 12
Former type catalyst' Sunflower seed oil Coconut oil Rapeseed oil Cottonseed oil Palm oil Soybean oil Fish oil I Two-stage II
Rapeseed oil
Cottonseed oil
(O/O)
'Pricat 9900, 9906, 9908; "Pricat 9910, 9920; 'wppm. aType Pricat, Unichema International, Emmerich.
Melting point ("Ci
Solids (% at) 20°C
30°C
IV
31 54 25 17 97 23 25 40
15 8 10 5 95 13 12 27
70
74 75 65
("C)
20°C
30°C
IV
42 37 40 43 34 43 38.5
35 30 53 27 24 47 38
15 10 22 13 9 28 16
70 70 70 70 70 70 70
34 34 34 31 56 36 34 38
1
75
ao 11
Modification of Fats and Oils
565
TABLE 6.29 Approximate Price per Nm3 of Hydrogen (US. $1 Assuming Different Economies of Scale and Price Scenariosa
Processpricefor
Price scenario U.S. $ per
100 Nm3h
300 Nm3h
800 Nm3h
~~
1500 Nm3h
3000 Nm3h
~~~~
Methanol cracking methanol
Steam reforming natural gas
Electrolysis electrical energy
10 15 20
kg kg kg
0.39 0.42 0.47
0.2 1 0.24 0.27
0.14 0.1 7 0.20
0.12 0.15 0.18
0.10 0.13 0.16
6 16 26
Nm3 Nm3 Nm3
0.50 0.57 0.62
0.2 1 0.27 0.32
0.12 0.1 7 0.23
0.09 0.14 0.20
0.07 0.12 0.17
6 9 12
kWh kWh kWh
0.43 0.58 0.72
0.40 0.55 0.67
0.38 0.53 0.66
0.37 0.52 0.65
0.37 0.51 0.65
a5ource: D a m (1993).
one to run these plants very economically. The method for raising hydrogen depends largely on the local circumstance, e.g., the price of electrical energy. Table 6.29 gives the prices depending on capacity and technology applied. Hydrogen is a colorless, tasteless and odorless gas (Table 6.30). It forms oxyhydrogen gas with oxygen (from the air); the gas @acts explosively to water, so that extreme caution is necessary when working with Ha, Aa a result of its very low density, it gathers under domes and in headspaces that have no ventilation. Therefore all hardening plants have an open dormer-window in the upper part of the building. Because of its low density hydrogen immediately escapes through these windows and consequently the risk of explosion is very small compared with extraction plants, for example, in which solvent vapors of high density gather on the floor. To estimate hydrogen consumption for hardening, Patterson (1994) gave as a rule of thumb that 1 Nm3 of hydrogen is required to lower the iodine value of 1 MT of oiYfat by one unit; this is equivalent to 0.88 NmVton H2 per IV unit. To TABLE 6.30 Physical Data of Hydrogen Atomic weight Density gaseous liquid Condensation point Solidification point Critical pressure (P,) Critical temperature (Tc)
1.0079 0.0899 0.070 -252.87 -259.14 12.8 -239.9
gR gcm3 OC
"C bar OC
Fats and Oils Handbook
566
TABLE 6.31 Minimum Quality Requirements for Hydrogen Used for Hardening > 99.5
Purity Common: Inert gases (N2,CH,, etc.) Water Carbon monoxide Better: Sulfur
Yo
99.9 a/a < 0.5% < 0.1 Yo vol/vol
< 0.05% VOl/VOl < 0.03% VOl/VOl <250 ppm
aSource: Patterson (1 994).
ensure good quality and economical processing, hydrogen purity has to meet a number of quality requirements, given in Table 6.3 1. 6.5.4.1Steam lron Hydrogen. Formerly, the steam iron process was the common method for hydrogen raising. The process runs in a two-part reaction cycle consisting of oxidation of iron and simultaneous reduction of the hydrogen of water in its first step (Equation [6.13]). Iron is reduced by carbon monoxide in the second step. Starting the reaction from iron oxide instead of iron it begins with the second step (Equation [6.16]). The reduction of hydrogen is, in fact, done by reaction of water with carbon monoxide regarding the overall reaction (Equation [6.17]); the detour via irodiron oxide facilitates the process similar to a catalyst. The reaction (Equation [6.17]) also proceeds directly to a certain small amount. The mixture of water and carbon monoxide is called water gas because it is an intermediate of hydrogen production via the reaction of water and coke (see texts on inorganic chemistry).
Oxidation 3Fe+3H20 3FeO+H,O
+ +
3FeO+3H2 Fe304+H,
3 Fe + 4 H,O
+
Fe30,
+ 4 H,
[6.13] = [6.11]+[6.12]
Fe,O,+CO 3FeO+3CO
+
3FeO+COz 3Fe+3COz
[6.14] t6.151
Fe30, + 4 CO + 3 Fe + 4 CO,
[6.16] = [6.14]+[6.15]
[6.11] [6.12]
Reduction
+
Total reaction 3 Fe + 4 H,O Fe30, + 4 CO 4 H,O
+
+
+ 4 CO +
Fe30, + 4 H, 3 Fe + 4 CO,
[6.13] [6.16]
+ 4 CO,
[6.17] = [6.13+6.16]
4 H,
Modification of Fats and Oils
567
For this process, iron or iron ore cannot be adequately purified to avoid by-products that have to be removed. The DGF indicates that the purity of crude hydrogen from this process is -90-95%, whereas Allen (1982) gave much higher figures. Sulfur and hydrogen sulfide, in particular, have to be removed because they are catalyst poisons and negatively influence the hardening reaction. CO is oxidized to C 0 2 in a converter; the crude gas then has to pass through caustic lime to bind C 0 2 and is desulfurized by passing through a bed of iron hydroxide (Fig. 6.112). Modern plants allow for a purity of 99.5% with no possibility of eliminating nitrogen, which is of no harm to the hydrogenation process, but does dilute the hydrogen somewhat. 6.5.4.2 Electrolytic Hydrogen. Electrolytic hydrogen raising was of greater importance as long as it was difficult to adequately purify hydrogen raised differently. The process is advantageous for regions in which electrical energy is cheap or natural gas is not available. The advantage of very high purity of the crude electrolytic hydrogen (>98.5%) is balanced by high investment and high space requirement. Still, electrolysis distinguishes itself by the flexibility it allows to easily adjust production to the demand by running a higher or lower number of electrolytic cells. Starting or stopping the plant is much easier than for any other hydrogen raising process.
1015 min
Fig. 6.112. Steam-iron process for hydrogen production and steam iron hydrogen generator (after Allen 1982).
568
Fats and Oils Handbook
Hydrogen is produced from water, which is alkalized for better conductivity, following the reaction equation with hydrogen formed on the cathode and oxygen on the node: 2HzO + 2Hz + 0
2
[6.18]
The theoretically required voltage for this electrolysis is 1.23 V; in practice, it is 2-3 V higher due to losses from overstraining and electrical resistance of the electrodes, the electrolytes and the diaphragm. High-efficiency cells require voltages just below 2.0 V. In pressureless working plants, one can most likely manage to come down just below 2.0 V. In plants working under pressure (at 30 bar), part of the overstraining is not applicable and, in practice, voltages of 1.85 V are reached there. In the plant the components for the electrodes are separated from each other by a diaphragm that allows current to pass. Both parts are gas-tight to the environment. Electrolysis can be conducted at low pressure (-1 bar) and high pressure (-30 bar). In the latter case, more hydrogen is dissolved in the electrolyte-solution, and the size of the hydrogen bubbles formed at the cathode is reduced. Consequently, overstraining and energy consumption are reduced (Fig. 6.1 13).
-
Fig. 6.113. Electrolytic hydrogen production plant (after DGF 1977).
Modification of Fats and Oils
569
Water quality must be carefully monitored because ions can promote corrosion of the electrodes. Patterson (.1974) defined a conductivity >6.67 10-6 L2 3-1 and < 10 mg/Ldry matter as the minimal requirements for conducting a smooth reaction and avoiding corrosion. Energy consumption for electrolytic hydrogen is immense: 2400 Ah are needed at 0°C to produce 1 Nm3 of hydrogen; at 20°C only 2180 Ah/Nm3 are required. Plants with medium efficiency or high-pressure plants with high efficiency therefore consume, respectively, for the production of 1 Nm3 hydrogen (water saturated):
2.60 V x 2180 Ahlm = 5.68 kWh/Nm3 1.85 V x 2180 Ah/m = 4.04 kWh/Nm3 They produce roughly 0.2 Nm3 hydrogen per kilowatt-hour. Regarding cost, it must be considered that electrolytic hydrogen is very pure and requires almost no postpurification. In addition, electrolytic oxygen can be sold. The cost of electrical energy is also important. Taking Europe as an example. such costs in Norway and Sweden, for example, are 50% of the cost in Germany; in the Netherlands it is 115% of the German cost (Haraldson 1985). In other parts of the world, the costs may be only a fraction of that. 6.5.4.3 Steam Reforming Process (Hydrocarbon Refining). Hydrocarbons can be reformed with water to produce carbon dioxide and hydrogen. Although the reaction has been known since the turn of the century, sufficient progress was made to use it efficiently for industrial purposes only in the 1950s. The reaction has to be accelerated by a catalyst and is described by Equation [6.19], which represents the sum of the two successive equations.
CnHZn+,+ 2n H 2 0 + n CO,
+ (3n + 1) H,
[6.19]
It consists of two steps and includes large-scale purification. These steps are as follows: CnH2n+2+ 12 H,O.
+
n CO + (2n + 1) H2
[6.20]
nCO+nH20
+
nC02+nH2
[6.21]
In the first step, the alkane, usually natural gas, reacts with excess water at high temperature (850°C). The endothermic reaction is catalyzed by nickel. The second (exothermic) step is conducted initially at 450°C and then at 200°C; water gas is converted into the end products hydrogen and carbon dioxide (Fig. 6.114). In total, the process is much more complicated because purification has to be included. The most important catalyst poison in hardening is sulfur. Almost all hydrocarbons are suitable for reforming. They occur in mineral oil and natural gas and are always accompanied by sulfur and sulfur compounds. These have to be
Fats and Oils Handbook
570
Hydrocarbons e.g. natural gar Hydrogen >>>
3 w c , CahlystcaMO
+ 15 kcPVMol I
W ' C , FdCr catalyrt, cooling
ROfOfming
I
L
2 W C , Culzn catalyst, cooling (counter c u with~madion water)
Shining
1
I
WC, Ethanol amine solution
250'C, Nbtalyst (Hydrogenation of COand COz-rests)
I
Hydrogen
Fig. 6.1 14. Hydrogen production via steam hydrocarbon reforming.
removed before the reaction because they not only poison the catalyst but also hamper later hydrogen purification. Because hydrogen sulfide can be much more easily removed than organic sulfur compounds, the hydrocarbon used for refining is hydre genated at -350°C over catalysts (e.g., cobalt-molybdenum). The resulting hydrogen sulfide can be separated by absorption on zinc oxide or washed out. Only then does the reforming process start. Crude hydrogen from the refining process must then be purified further. It is washed with a solution of ethanol amine to remove Cq.The CO and
571
Modification of Fats and Oils
TABLE 6.32 Composition of Crude Hydrogen from the Iron Carbon and from the Hydrocarbon Reforming Process Iron carbon process Hydrogen Carbon dioxide Carbon monoxide Oxygen Hydrogen sulfide Nitrogen
98 -99% 0.5 -1.0% 0.2 -0.4% 0.0 -0.1% 0.05-0.2% 0.25-1 .O%
Hydrocarbon reforming process Hydrogen Carbon dioxide Carbon monoxide Oxygen Methane Nitrogen
99.968% 0.001 Yo 0.001%
0.005%
w0
0.01 0.007%
remaining traces of CO, are hydrogenated to methane. C02 is evaporated from the ethanol amine solution and reused. If this process is conducted carefully, hydrogen purities of almost 99.97% can be reached (Table 6.32). Other methods allow for even higher quality. Molecular sieves partly combined with active carbon treatment yield 99.99% purity. Using palladium silver membranes, which allow only the small hydrogen molecules to penetrate, makes possible purification to 99.9999%. However, such qualities do not add any advantage to the hydrogenation process, its yield or the quality of the end products (Charlesworth and Schmidt 1965, Hack and Hall 1965, Serfass and Silman 1965). The Proximo1 process (Lurgi Apparatebau) uses methanol as a buffer substance for hydrogen production. In the Proximol process, methanol is formed from water and carbon monoxide. This can be split and converted under copper catalysis at moderate temperatures (compared with steam reforming) in one step (Fig. 6.116). 6.5.4.4 Other Sources of Hydrogen. As mentioned earlier, hydrogen can also be purchased; if the producer is nearby, it can be delivered under pressure and liquefied via pipelines. Storage under pressure is at -200 bar in steel cylinders that are usually bundled. Delivery is done mainly via trailers that are left on the premises of the hydrogenation plant. Hydrogen is liquefied at a temperature of about -253°C. Hydrogen technology will quickly develop further when pressure increases to develop cars whose motors bum hydrogen. Should this succeed, technologies for hydrogen production and purchasing possibilities would further improve. 6.5.5 Influence of Processing Conditions
Hydrogenation of oils and fats is influenced mainly by six parameters. The task is to find the optimal combination for each end product and to adequately control the
572
Fats and Oils Handbook
Fig. 6.1 15. H2 production plant for the methanol cracking process (750 Nm3/h), principle and photo. Source: J.P. Daurn, 1993.
process. These six parameters are time, temperature, hydrogen pressure (and thus solubility), mass transfer, catalyst (kind, state and concentration) and substrate (i.e., oil and fat). They all flow into a seventh parameter, namely, processing, the sum of all possible influences. Time as a process parameter can easily be understood because any reaction needs a certain reaction time. However, its main influence is the different products that can be obtained by incomplete (i.e., time-dependent) hardening. Figures 6.117 and 6.1 18 show the dependence of the characteristics of end products (solids content and fatty acid composition) on the reaction time. It becomes evident from these figures that, as expected, the solid content rises with time. C,,-fatty acid composition is characterized by a decrease in linolenic acid first, followed by a quick increase in oleic acid parallel to a decrease in linoleic acid. Only after 40 min does the fraction of oleic acid, which is always fed from saturation of linoleic acid, decrease in favor of stearic acid. The course of the reaction becomes clearer in Figures 6.119 and 6.120. The influence of all other parameters on the reaction and the end products is effective over the entire reaction time (Table 6.33). These influences are described in the following sections. Influences of temperature, hydrogen pressure, amount of catalyst and concentration of catalyst poison (sulfur) are shown for the example of canola rapeseed oil hardening. The trials
Modification of Fats and Oils
5i3
Fig. 6.1 16. H, production plant for the steam reforming process (300 Nm3/h), principle and photo. Source: J.P. Daum, 1993.
have been conducted with an identical oil sample under laboratory conditions to keep the selected conditions as equal as possible (Table 6.34). 6.5.5.1 Temperature. Hydrogenation is an exothermic process with a little more than 30 kcal being set free per mole of double bond. This is equivalent to a temperature increase of 1.6-1.7 K per lowering of each IV unit. The heat of reaction on the one hand makes heating unnecessary after the activation energy has been introduced. On the other hand it makes it necessary to cool quickly and in a well-controlled manner so that the reaction does not “run away” and follows the temperature pattern foreseen. Like any other chemical reaction, hydrogenation is temperature dependent and the reaction rate increases in direct proportion to temperature. The temperature dependence of the reaction rate is true not only for the reaction itself but also for all side reactions, including such effects as an increase in reaction rate so that a considerable amount of by-products are formed, or a temperature higher than that at which they start running. Besides this direct influence on the reaction, an increase in temperature manifests itself in higher solubility of hydrogen (see Chapter 6.5.5.2) and a decrease in viscosity, which improves mass transfer (see Chapter 6.5.5.3).
5 74
Fats and Oils Handbook
Fig. 6.117. Solids content of hydrogenated soybean oil dependent on the time (after Unichema International, Emrnerich). Below an excerpt of a table is reproduced in which Patterson (1994; courtesy of AOCS) showed the temperature influence on hydrogenation. 100-1 10°C Partial hydrogenation of vegetable oil to reduce the majority of linoleic acid; minimum formation of trans-isomers. The first of two stages in a hydrogenation that seeks minimum solids 120°C content with flavor stability. (a) Not to be exceeded until a certain IV drop has been attained for oils 150°C containing substantial amounts of linolenic acid and even more unsaturated groups so as to avoid cyclization of hydrocarbon chain. (b) The popular level at which to conduct hardening of the all-hydrogenated vegetable shortening with prolonged melting range. (a) Above this temperature nickel carbonyl is completely unstable; 160°C hence, the poisoning effect of CO on Ni ceases. (b) Above this temperature, migration of double bonds and formation of trans-isomers are encouraged to reach their equilibrium level. The usual level for edible oil hydrogenation, which may follow a set 180°C amount at a lower temperature for reasons given above. If a relatively quick melting range is needed, this temperature should be used as much as possible after any other control requirements have been met. At this level, polyunsaturates diminish markedly. Should not be exceeded for edible product hardening. Above this, the 200°C risk of worsening color and increase in free fatty acids grows.
-
575
Modification of Fats and Oils
70
-{
g 60 5
EM, 8 P 2 30 LL
10
0 0
30 40 20 Resctlon tlme [mln]
10
60
Soybean oil; 3 bar hydrogen pressure; 180°C; 0.03% PRICAT 9910
Fig. 6.118. Fatty acid composition of hydrogenated soybean oil dependent on the time (after Unichema International, Emmerich). 210°C 240°C
Maximum for the most technical or nonedible hydrogenations; above this temperature, hardening rate may even be increasingly retarded. Acceptable maximum for hydrogenation of dimer and trimer fatty acids.
The various processing parameters mutually influence each other. Therefore the influence of temperature is always also dealt with in the following chapters. As a Solids content [%I
at
60 -
1ooc
60 -
15OC
40
20°C 25OC
30
30°C 20 3s0c 10
40°C
0 0
16
45 30 Hardeningtlme [mln]
60
Fig. 6.119. Solids content of hardened soybean oil depending on the hardening time.
Fats and Oils Handbook
576
Palm kernel oil Iodine value
Iodine value
160
120 PRICAT 9920,150-200"C, 3 bar hydr press.
80
40
0 0
20
40
60
80
100
120
140
160
Reaction time [min] Fig. 6.120. Decrease in iodine value during hardening, depending on the reaction time (after Unichema International).
model reaction, the hydrogenation of rapeseed oil at 140 and 200°C is given in Figures 6.121 and 6.122, respectively. The solid fat content of the end product from trial I (200°C) is lower at temperatures below 3 0 T , but higher at temperatures above 30°C as a result of the increased stearine formation at low hydrogenation temperature. Coenen (1976) gave the starting point for the temperature increase dependent on the iodine value (RID = refractive index drop): R*D(start for temperature increase)
= Oeoo2
'
(I'unhardened
triglyceride)*
[6.22]
6.5.5.2 Hydrogen Pressure and Solubility. The higher the solubility of hydrogen, the higher the probability that it is available at the point of reaction, i.e., the TABLE 6.33 Influence of Different Process Parameters on the Reaction and the Hardened Products Increase in Temperature Pressure Agitation Amount of catalyst
Reaction rate
Selectivity
lsomerization
++
t++
+++
+ ++
++ +
++ +
+t+
tt
+
+influence ++great influence +++very great influence.
Modification of fats and Oils
577
TABLE 6.34 Process Conditions of Trials to Illustrate Influences of Different Process Parameters on the Hydrogenation Reaction and on the Hardened Products Trial
Catalyst concentration ("C)
Temperature ("C)
0.1 0.2 0.1 0.1 0.1
200
Hydrogen pressure (bar1
-
I II 111 IV V
200 140 2 00 2 00
Catalyst: PRICAT 9906; Unichema International. Stirring: (R) = 750/min.
contact surface of catalyst and oil. Because hydrogen solubility is directly proportional to temperature, an increase in temperature must be positive in this sense. The solubility of hydrogen in oil can be described by the following equation (Anderson et al. 1974):
where S is the amount of dissolved hydrogen (NmVMT of fat), t is the temperature ("C), p is the pressure (bar; 1 c p < lo), afat= 40.06, bf,, = 0.334, soil = 47.04 and boil= 0.249.
Melting point ['C] 66
-
Reaction time R [min] Trans f.a. content ph]
*----* H
60 50 60 45 40 40
30 35
20 30
10 26
90
80 70 Hardening progress [I.V.]
90
80 70 Hardening progress [I.V.]
Rapeseed oil; 2 bar hydrogen pressure; 0.1% wlw PRICAT 9906
Fig. 6.121. Reaction time, melting point and trans content of hardened rapeseed oil dependent on the reaction temperature.
5 78
fats and Oils Handbook
Rapeseed oil; 2 bar hydrogen pressure; 0.1% whv PRICAT 9906
Fig. 6.122. Solids content of hardened rapeseed oil dependent on reaction temperature. The equation shows that the influence of pressure predominates over the above-mentioned influence of temperature. Pressures >10 bar, however, do not seem to make sense on the basis of current knowledge. Hydrogenation is usually carried out between 2 and 5 bar. The benefits of increased pressure were investigated by Mounts et al. (1978) and Koritala et al. (1980), who conducted the reaction at 210 bar in autoclaves resistant to pressure up to 350 bar. They showed that hydrogenation was twice as fast at 70 bar as at 35 bar; at 210 bar, it took only 10% of the time necessary at 35 bar. The extrapolated graph for hydrogen solubility in oil for three temperatures shows that doubling of the temperature results in 20% higher solubility, whereas doubling of the pressure accounts for 60% higher solubility (Fig. 6.123). The effect of the theoretical considerations from Figure 6.123 was investigated by Ray (1985). He worked out graphs that show the speed of reaction (IV unitdmin) of soybean hardening dependent on pressure and temperature. In contrast to theory, practice proved that the solubility of hydrogen is not the predominant factor for the reaction rate. At low pressure, increasing temperature by 50% results in a reaction rate that is 2.5 times higher. An increase in pressure does not remarkably accelerate the reaction at low temperature (T < 150°C); at 2OO'C, it is almost 10 times faster. Generally, there is a shortage of hydrogen compared with what would be required for a fast reaction. Assuming a vegetable oil with an iodine value of 135 (soybean oil, for instance), the concentration of double bonds is a little higher than 5000 mol/m3 of oil. Hardening of this oil at 3 bar hydrogen pressure at 180°C(see Fig. 6.1 18, for instance) allows for a hydrogen concentration only slightly less than 10 m0l/m3 of oil, which is only a small fraction of the double bond concentration..
5 79
Modification of Fats and Oils
-
-
CoUonreed 011
I.4-
Cotton seed oil
natlve
hardened
I-
0.12
1.2
I.o
0.10
9.7 bar 0.8-
1.0 bar
0.08
4.8 bar 0.6
0.4
I
loo
I
I60
l
l
’
loo
b.os I60
200
Fig. 6.123. Solubility of hydrogen in cottonseed oil (after Anderson 1974).
It should be noted that the higher availability of hydrogen caused by temperature or pressure increases is not desired in all cases. The selectivity S,,, for example, decreases with increasing hydrogen concentration in the reaction mixture because excess hydrogen is then always available to enable further reaction to stearins. Increasing the hydrogen pressure increases the melting point, the hydrogenation time and the cram content. The solids content is also higher at most temperatures (Figs. 6.124 and 6.125).
6.5.5.3 Mass Transfer. Hardening takes place in the three-phase system gas/liquidsolid. The gadliquid reaction partners hydrogen and oil have to be brought together on the solid catalyst surface for reaction. The reaction products have to be removed as quickly as possible to enable new reactions, and consumed hydrogen in the reaction has to be replaced. This is particularly important because the concentration of double bonds in the oil is always very much higher than the concentration of hydre gen (see Chapter 6.5.5.2).Mass transfer therefore plays an important role: 1. H, is brought into the oil. 2. H, is dissolved in the oil. 3. H, travels to the catalyst surface surrounded by an oil film. 4. Oil molecules and H2 travel into the catalyst’s pores toward the nickel surface. 5 . H, is absorbed onto the active portion of the Ni catalyst. 6. H, dissociates to hydrogen atoms capable of reaction. 7. Oil molecules are absorbed at their double bonds by the catalyst. 8. H, is added to the double bond of the oil molecule.
580
Fats and Oils Handbook
Hardening progress [I.V.]
Hardening progress [I.V.]
Rapeseed oil; 200°C reaction temperature; 0.1% whv PRiCAT 9908
Fig. 6.124. Reaction time, melting point and trans content of hardened rapeseed oil dependent on the hydrogen pressure.
9. Desorption of the (partially) hardened oil molecule. 10. Diffusion from the catalyst’s pores. 11. Return to the bulk oil through the oil film surrounding the catalyst particle. In the immediate vicinity of the catalyst, diffusion plays the most important role. Similar to the equation for hydrogen solubility, Anderson (1974) has developed a representation for this process as follows: N = A DH.c/L
[6.24]
where N is the rate of transported hydrogen, A is the surface of pores, L is the length of pores, DH is the diffusion coefficient for hydrogen in oil (cmVs) and c is the concentration of hydrogen in the oil (L H2/kg oil). The diffusion rate is only very weakly correlated to the iodine value; therefore it changes during reaction, but only slightly and without any practical consequence (Fig. 6.126). Contrary to mass transfer on a small scale by diffusion at or close to the catalyst surface, mass transfer on a large scale has to be supported by stirring and permanent circulation. In addition to increasing mass transfer, stirring also helps to keep the temperature in the reaction mixture as homogeneous as possible to avoid local overheating. It also helps thermoregulation by transfemng the heatingkooling effect quickly through the mixture. Usually stimng helps for a good intermixing. New processes also use pump circulation with permanent injection of the reaction partners into the reaction chamber (see Chapter 5.56). Design and arrangement of the stirrer are of great
Modification of Fats and Oils ""
581
I
10%
so
2O0C
3OoC
4OoC
90
ao
70
Hardening progress [I.V.]
1 Fig. 6.125. pressure.
Rapeseed oil; 200°C reaction temperature; 0.1% w/w PRICAT 9906
I
Solids content of hardened rapeseed oil dependent on the hydrogen
importance for an effective distribution of hydrogen and an even temperature in the reaction chamber. Care has to be taken to avoid damage to the catalyst by mechanical stress as a result of poor design of the stirrer or excessive stirrer speed, which can drastically lower the efficiency.
Fig. 6.126. Diffusion of hydrogen in cottonseed oil (after Anderson e t a / . 1974).
Fats and Oils Handbook
5a2
Higher temperatures as well as increased stirrer speed thus improve diffusion and speed up the reaction. Both effects add up but not in a linear fashion; increasing the stirrer speed at high temperatures accelerates the reaction more than at low temperatures. The same is true in reverse; at a high stirrer speed, a temperature increase is more effective than at a low stirrer speed. The choice of these two parameters depends on the end products wanted because those are influenced by both (Fig. 6.127 and 6.128). By keeping the catalyst concentration constant, the selectivity c& be increased by lowering the stirrer speed. The less hydrogen that is available at the point of reaction, the lower the formation of stearic acid. Increasing the amount of catalyst logically works the other way around. This influence is described in Chapter 6.5.4. 6.5.5.4 Kind, Condition, and Concentration of Catalyst. The kind of catalyst has already been discussed in Chapter 6.5.3. The previous figure showed that there is an optimum catalyst concentration that is influenced by the other reaction processing parameters (here stirrer speed); this is also true for selectivity. Similar considerations can be made for the reaction rate (Fig. 6.129). As could be expected, increased stirrer speed improved mass transfer with the effect of a higher reduction rate of IV (decrease of IV units per time). For a given catalyst concentration, however, an optimum that is dependent on stirrer speed can be observed.
Stirrer speed [min
-’ 10001 3
1950
1450
450
Decreas of I.V. units Der minute
160
180
200
220
240
Temperature [“C] Soybean oil; 3 bar hydrogen pressure; 0.08% Ni-catalyst
Fig. 6.127. The influence of stirrer speed and temperature on the hardening of soybean oil (after Allen 1982).
Modification of Fats and Oils
Stirrer speed [min
583
-' 10001 *
2000
1500
1000
500
0 0.01
0.05
0.13
0.09
Catalyst concentration [% Nil Soybean oil; 185°C; 2.4 bar hydrogen pressure Fig. 6.128. The influence of stirrer speed and catalyst concentration on the selectivity in hardening of soybean oil (after Allen 1982). Reaction rate [Decrease in I.V. units/min]
5 4-
321-
0.02
R = Stirrer speed (min - l )
0.04
0.06
0.08
0.10
0.12
0.14
Catalyst concentration [% Nil Soybean oil; 192°C; 3 bar hydrogen pressure
Fig. 6.129. Reaction rate of soybean oil hardening dependent on stirrer speed and catalyst concentration (after Allen 1982).
Fats and Oils Handbook
584
The influence of different catalyst concentrations with all other process parameters kept constant is shown in Figures 6.130 and 6.13 1 . As noted earlier (see Chapter 6.5.3), the structure of the catalyst is of great importance. Too narrow pores can be blocked by oil molecules and render adsorption and desorption more difficult. Too large pores reduce the total catalyst surface. The same can be said for the particle size of the catalyst as such; too large particles reduce the surface area, too small particles make filtration more difficult (Table 6.35). The structure of the catalyst also influences the trans fatty acid formation as shown for the reaction of a nontriglyceride model substance (Fig. 6.132). Apart from the physical properties that the catalyst carries by nature of its production, there is also an influence from the number of reuses. In addition to the cost-saving effect of multiple use, reuse of catalyst usually leads to more stable (uniform) quality of the end products. The catalyst condition is stabilized at a constant performance level after some reaction cycles, a level that can deviate substantially from the initial one. With a catalyst that has already been used two or three times before, products with constant quality are obtained, i.e., equal level of trans fatty acids, iodine value and solid fat content at different temperatures. In addition to the amount applied, the kind of catalyst plays an important role (as can be expected). Different catalysts for different applications are being produced, three of which are compared below in their influence on the reaction products (Table 6.36). All three are nickel catalysts and have been used under laboratory conditions to ensure constant processing conditions. Table 6.36 gives these conditions, and the results of the trials are illustrated in Figures 6.133 and 6.134.
I
Rapeseed oil; 200°C reaction temperature; 2 bar hydrogen pressure
Fig. 6.130. Reaction time, melting point, and trans content dependent on the catalyst concentration.
I
of hardened rapeseed is
583
Modification of Fats and Oils
Hardening progress [I.V.] Rapeseed oil; 200°C reaction temperature; 2 bar hydrogen pressure
Fig. 6.131. Solids content of hardened rapeseed o i l dependent on the catalyst concentration.
Catalyst XI (Pricat 9900) is a very active catalyst for universal use; catalyst XII (Pricat 9906) is highly selective and is applied when the amount of trienes and saturated triglycerides in the end product must be kept low; catalyst Xm is used when a steep dilatation curve is desired. More examples for the characteristics of products hardened with different catalysts are given in Chapter 6.5.7. At present, these catalysts have been replaced by new types exhibiting better activity and sensitivity, lower sensitivity toward catalyst poison and an improved filtration rate. In the table, results of trials with Pricat 9910 and Pricat 9920 are shown. The former is a multipurpose, sulfur-resistant, medium-pore catalyst with a high nickel surface area; the latter is a very selective, wide-pored catalyst, especially developed for vegetable oil hardening. TABLE 6.35 Influence of Structural Parameters of the Catalyst on the Hardening Processa ~~
Structural Parameter Total surface area Nickel surface area Pore structure Particle size Poisoning
Activity
Influence on Selectivity
** *
* **
* **
* **
*,**influence proven; (*) influence assumed aSource: Klauenberg( 1 986).
Consumption
(*I
** * *
Fats and Oils Handbook
586
Fig. 6.132. Amount of trans isomers in methyl oleate hydrogenation depending on the pore size of the catalyst (after Linsen 19711.
Finally, the effect of catalyst poisoning is shown in Figures 6.135 and 6.136. They represent the effect on soybean oil hardening with catalysts that were poisoned intentionally with 2 and 4 ppm sulfur, respectively.
6.5.5.5 The Substrate. The influence of by-products or impurities will not be discussed in this section but rather the influence of the oiYfat itself. The most prominent characteristic for an oiYfat to be hardened is its degree of unsaturation, i.e., the number of double bonds represented by its iodine value. The IV is a measure for the amount of hydrogen that is consumed during reaction (Fig. 6.137). Fats and oils are natural products that undergo certain fluctuations in their composition. These fluctuations are caused either by their genetic blueprint (different cultivation) or by environmental influences such as climate, weather or location TABLE 6.36 Process Conditions for Soybean Oil Hardening, Comparing Three Catalyst9
Temperature Hydrogen pressure Catalyst concentration
Pricat trial
9900 A
9906 B
9908 C
(“C) (bar)
180 3.5 0.09
140 3.0 0.09
180 2.0 0.45
(Old
aCourtesy of Unichema International, Emmerich.
587
Modification of Fats and Oils
Share C18:O [%I 80
Share C18:l [%]
I
I
I
120
80
100
25
0 60
Iodine Value
Fig. 6.133. Influence of catalyst and reaction conditions on the c18:o and acids (catalysts from Table 6.36).
c1&1fatty
of cultivation, and harvest and postharvest conditions. Therefore, to obtain optimal results, hardening conditions have to be adjusted to the raw materials. The composition of poultry fat is very much dependent on the feed; the more grains in the diet, the more unsaturation. Milk fat differs in composition when
50
-b
Soybean oil
\,.\18:2
120
100
80
60
Iodine Value
Fig. 6.134. Influence of catalyst and reaction conditions on the acids (catalysts from Table 6.36).
c1&2 and
c,&3 fatty
Fats and Oils Handbook
5aa
1
Rapeseed oil; 200°C react. temp.: 2 bar hydr. press.; 0.1% w/w PRICAT 9906
1
Fig. 6.135. Reaction time, melting point, and trans content of hardened rapeseed oil dependent on the sulfur content of the oil.
cows are grazed on pastures compared with winter feed inside. However, these two fats are rarely hardened. Fish oil is more highly unsaturated when produced from fish that are about to spawn or starting on their way to the spawning grounds. The IV value of fish oil increases with the coldness of the water in which the fish are caught.
1
Rapeseed oil, 200°C react. temp.; 2 bar hydr. press.; 0.1% wiw PRICAT 9906
1
Fig. 6.136. Solids content of hardened rapeseed oil dependent on the sulfur content of the oil.
Modification o f Fats and Oils
5 8'1
Soybean oil Sunflower seed oil Cottonseed oil Rapeseed oil Groundnut oil
Fig. 6.137. Melting point of hardened oils and hydrogen consumption (after Rudischer 1959).
Vegetable oils and fats also exhibit such influences. The linoleic acid content of sunflower oil depends on the difference between day and night temperatures in the area of cultivation; it can range from 30 to 70% (Morrison et ul. 1978). Similar differences are found for Argentinean (IV 103-105) and Nigerian (IV87-95) peanut oil. The many areas of origin, the many different kinds of stress during harvesting, crushing, storage and transport and the variety of end products desired lead to a variety of processing conditions adapted to the specific case; many of these are described in detail by Patterson (1994). 6.5.5.6 Influence on Isomerization. Isomerization reactions that occur during hardening (see Chapter 6.5.2.1) have been explicitly researched. Although all isomerization products from hardening of vegetable and mammal fats also occur naturally in fats and oils and are harmless according to today's knowledge, much attention and publicity have been paid to them in some parts of the world (see Chapter 6.5.7.1). It must be said that hardened fats, as such, cannot be equated with rruns fatty acids. The amount of TFA can be kept low by special hardening techniques. Generally the TFA content increases with increasing S, selectivity. Ray (1985) researched the influence of some processing parameters on trans fatty acid content on a laboratory scale (Table 6.37). 6.5.6 Hardening Techniques
Hardening is influenced mainly by the parameters described in Chapter 6.5.5. A great variety of end products can be obtained from the same starting material by varying the reaction parameters. Besides these variations, the quality of the oiVfat plays an important role.
Fats and Oils Handbook
590
TABLE 6.37 Influence of Process Conditions on the Trans Fatty Acids Content of Hardened Fats and Oils Trans content increasing with
Keeping constant ~~~
~
~
Lowering stirrer speed, increasing temperature Falling pressure, increasing catalyst concentration Fa1Iing pressure
Pressure Stirrer speed Temperature
6.5.6.1 Preparation of Fats and Oils (Purification). To ensure efficient hydrogenation and good quality fats, the oildfats to be hardened have to be prepared carefully. Usually they are prerefined (see Chapter 7, refining). Recently, however, processes have been developed for direct hardening, i.e., without prerefining. Different authors articulate different opinions on what the quality of a well-pretreated fat/oil for hardening (Table 6.38) must be. An excessively high water content contributes to deactivation of nickel and to fat splitting (hydrolysis). Too high FFA content favors the formation of nickel soaps and negatively influences filtration. Soap, as a surface active substance, covers the catalyst’s surface and disables it. All other impurities are usually removed during bleaching (see Chapter 7.4 bleaching). These include seed (chlorophyll), blood pigments from the crude oils and fats that can block the catalyst’s surface. The really important catalyst poisons, however, are nitrogen, phosphorous, sulfur and chlorine compounds. Table 6.39 gives typical ranges for such compounds in crude oils as well as in oils pretreated for hardening. Obviously, the complete removal of such catalyst poisons is not possible for cost reasons. However, they have to be brought to levels that represent the commercial compromise between cost for removal and benefit for hydrogenation. Different catalysts (catalyst metals), of course, differ in their sensitivity toward catalyst poisons. The most damaging of these poisons, sulfur, which is present in some form in all oils and fats, heavily deactivates almost all catalysts. A possible explanation for the negative influence of sulfur on different catalysts is given by Coenen (1976). Sulfur poisoning also indirectly shows the advantage of support catalysts over nonsupport catalysts. Assuming a surface of 0.15 m2/g of catalyst, 5 ppm of sulfur block about 13 m2 of catalyst surface area in the oil. This means that the equivalent of TABLE 6.38 M i n i m u m Quality Requirements for Oils/Fats to Be Hardened Free fatty acids Soap Water Sulfur Source
<0.05% <0.05% <0.05% co.01Yo Patterson (1995)
<0.05% <0.0025% <0.005%
Ong (1979); for bean oil
Modification of Fats and Oils
591
TABLE 6.39 Concentration of Catalyst Poison i n Source Materials and Aimed at for Hardening
Element N P S
CI
Source material (PPm)
Prepared for hardening (PPm)
50-300 20-500 5-20 Fish up to 100
5-50 2-1 0 5
Remarks: P: ppm x 25.5 = lecithin content S: crude rape up to 200, crude fish up to 100
87 kg/MT nonsupported nickel catalyst (particle size -5 pm) would be deactivated. The surface of the support catalyst is 3CO-600 times larger so that only -0.2 kg/MT of catalyst would be lost by the reaction. In addition to the deactivation of nickel, poisoning with sulfur has the disadvantage that nickel sulfide is formed, which promotes the formation of rruns fatty acids. The poisons for the most common catalyst nickel are all well known. A very detailed investigation was conducted by Ueno as early as 1918, a year when hardening was still in its infancy. He identified 50 substances as poisons. Poisoning can also have a beneficial influence when it is used to modify the catalyst and to change its characteristics. A slight covering of the catalyst with sulfur, for example, can lead to a higher selectivity S21(less stearic acid more oleic acid). To obtain such a catalyst, it is first used to harden an oil rich in sulfur compounds. 6.5.6.2 The Hardening Process. The best combination of all process parameters described in Chapter 6.5.5 is brought together to run the hydrogenation process, dependent on the source material and the end product to be obtained. Source material and particularly the catalyst and processing conditions can be varied relatively easy, whereas the plant itself is fixed or can be changed only in the long term. Here, it is important either to build a plant that is especially designed for a certain purpose or to choose flexible equipment that can be adjusted to all needs. As in all other processes in oil and fats technology, there is a trend away from discontinuous toward continuous plants. For the time being, however, the vast majority of hardening is done in batch autoclaves that are equipped as described in the following. The equipment is relatively simple. The batch autoclave (Fig. 6.138) holds up to 30 tons; it has to withstand a temperature of up to 250°C and usually 4 bar of pressure. The oil is pumped into the reaction vessel ( l ) , which is evacuated to avoid oxidation processes in the oil and oxyhydrogen reaction. The oil is then heated to the gassing temperature. In the meantime, a slurry of catalyst in oil that was prepared in a mix tank (3) is pumped into the reaction vessel (1). After the reaction mixture is homogeneous, hydrogen is pumped in. The reaction starts, and the mixture is heated up by the exothermic process (965 kJ per ton of oil and per decrease of IV unit). In the beginning, this energy is used to further heat up the oil (specific heat -300 kJ/MT); as soon as the desired reaction tern perature is reached, heavy cooling is necessary. After the reaction has ended (progress
Fats and Oils Handbook
592
......... . 7.......... ...... /.\
:..........,,......-,:
l
P
8
Fig. 6.138. Batch hardening Plant with plate filter press (after DGF 1977).
monitored by measurement of refractive index), hydrogen is sucked off from the head space. The mixture of oil and catalyst is cooled down to-90"C and filtered (2) at that temperature. Spent catalyst is reused (see Fig. 6.144) or recycled (see Chapter 6.5.3.2). The crude hard fat is pumped via (M) into a buffer vessel and then cleaned (see Chapter 6.5.6.3). The loss of catalyst per reaction cycle is 10-20 g/MT of vegetable oil/fat and 100400 g/MT of animal oil/fat (Fig. 6.139). There are two principal batch processes, the "dead end" process with internal hydrogen circulation (stirrer) and the process with external hydrogen circulation. The dead end process is characterized by hydrogen, which is in the head space of the hydrogenation vessel and is brought into the reaction mixture and distributed by intensive stirring. To accomplish this task, the stirrer has to run at high speed, with the risk that the catalyst will be physically damaged and lose part of its hardening activity and also filterability. In addition, volatile hydrogenation by-products that may negatively influence smell and taste remain in the head space of the reaction vessel. Although the majority of these by-products are usually drawn off with excess hydrogen, a sufficient amount may remain in the product so that more efforts for postcleaning are necessary (Fig. 6.140).
Modification of Fats and Oils
593
Oil
reaction vessel, evacuated to gasing temperature, -150'C
Heating up
I/: preparation
i.
t
t
+=Catalyst
.1
Catalyst addition
2008OOg per ton of oil t
t
t
I
I I
<<< Hydrogen (2-4 bar, 0.2mVI.V.unit) t
to reaction temperature, 2W'C
I Cooling
I
I Recycling (6.5.3.2)
c
Crude hardened oilffat
Fig. 6.139.
Processing flow chart of hardening
*Vacuum generation Catalyst I I
O i l t o b d hardene Cooling water
I
U
6.. f-
dened duct
Fig. 6.140. Schematic plant for the dead end process with external hydrogen circulation (after DGF 1977).
Fats and Oils Handbook
594
TABLE 6.40 Cycle Times for Hardening with and Without Heat Recuperationa Process step Heat recovery
Cycle time (min) Yes No
Filling Heatinqdrying Hydrogenation Cooling Emptying Total cycle = cycledd
15 30 100 30 15 190 7-8
10
100
10 120 11-12
aSource: Duveen and Steinhauer (1984).
The disadvantages of the dead end process can be avoided when external hydrogen circulation is applied. Here, hydrogen is drawn off from the head space, circulated with circulation compressors or jet pumps and pressed back into the reaction vessel from the bottom. Thus it passes through the reaction mixture so that stirring can be slow and just sufficient to circulate the mixture and keep the catalyst suspended. Volatile by-products are continuously carried out of the reaction vessel via the hydrogen flow and condensed outside. Consumed hydrogen is continuously replaced by fresh hydrogen that is injected before the compressor. A considerable improvement can be achieved by installing a heat recovery system. Energy consumption as well as the duration of reaction cycles can be drastically reduced. Duveen and Steinhauer (1984) showed the effect of using a BUSSreactor as an example (Table 6.40). Within a period of 5 mo, the authors observed savings of 116 kg steam per ton of oil, 80% of water, 35% of electrical energy and an improvement of 40% in productivity. The savings are particularly high when the plant is running without product change. An additional opportunity exists when the energy from the exothermic reaction is used to generate steam. By using it for low-pressure steam production, which can also be used elsewhere in the plant, up to 200 kg steam per ton of oil can be saved (Table 6.41). TABLE 6.41 Energy and Auxiliary Material Consumption for Hardening (per Ton of Product or per Unit Decrease in IV) Energy or material
Conventional
Optimum energy recovery
Electrical energy Steam Cooling water (At = 20°C) Catalyst, vegetable oils marine oils Hydrogen
12-1 5 kwh/t 100-200 kdton 3-4 mVton
9-1 0 kWh/ton For starting up only 0.3-0.5 m3/ton 10-20 @on 100400 qton 1G1.2 Nm3/1V
Modification of Fats and Oils
59s
Hydrogen consumption depends, of course, on the number of double bonds to be saturated, expressed by the decrease in iodine value and the corresponding increase in melting point (examples, see Fig. 6.137). In addition to the eternal effort to improve cost efficiency, it is always a goal to achieve better control of the process to generate end products of better quality. One of the most important parameters is thermoregulation. After the heating to gas temperature,the start of the reaction and the temperature rise to reaction temperature, the heat produced by the reaction has to be withdrawn. The quicker this can be done, the sooner thermoregulation is achieved and the more defined are the end products. In large hardening vessels with standard equipment, i.e., conventional heating and cooling coils, the response time to temperature changes is not always sufficiently short. This situation can be considerably improved if heat exchange is done outside the reaction vessel (autoclave, a). A plant allowing such processing is the so-called loop reactor (Fig. 6.141). The reaction mixture is continuously circulated (pump b), leading to very good intermixing and allowing for very short reaction toward temperature changes. This allows for almost isothermal reaction with temperature fluctuations of only 1 K (Duveen and Leukritz 1982).A very positive side effect originates from reinjection of the reaction mixture into the head space via an injector nozzle (d). Hydrogen from the head space is dragged along and absorbed. The combination of these two effects gives very reproducible results and also allows for low tram content.
Fig. 6.141. Loop reactor (courtesy of Buss AG, Basel).
Fats and Oils Handbook
596
All processes described above are carried out discontinuously. Despite the trend toward continuous processing, almost no continuous plants are in operation even though these have been used for fatty acids for a long time. Figure 6.142 shows such a plant design (Lurgi) that could be used for oils and fats hardening. The oil is preheated and mixed with catalyst in a vessel. After heat exchange with the hot oil coming from the reactor, the oil to be hardened is further heated and continuously pumped from the bottom through the reaction vessel at a speed that allows for the necessary reaction time. The hardened oil is cooled and filtered, and the catalyst is reused.
Hydrogen
$re- warmingf
Heater Coolei I
Fig. 6.1 42. Continuous hardening plant (courtesy of Lurgi, Frankfurt)
Modification of Fats and Oils
597
6.5.6.3 The Catalyst. The catalyst's influence on the reaction mechanism (Chapter 6.5.2.1) and the process (Chapter 6.5.5.4) as well as on the end products has already been discussed. The catalyst is added as a processing aid to the oil and has to be removed after the reaction. This is another factor that has to be considered. With the use of nonsupport catalysts, filter aids have to be added, causing additional costs (Fig. 6.143), whereas support catalysts can easily be filtered off. Usually hardening is not done with fresh catalyst; rather used catalyst is reused and topped up by fresh one. As an example for the mass flow of catalyst (fresh and reused), Figure 6.144 shows the hardening of 20-ton batches of rape oil.
6.5.6.4 Other Processes (Methods). Besides conventional hardening, experimental plants exist to test new methods of hydrogenation, including continuous ultrasonic hardening (Moulton et al. 1983 and 1987). The oil is preheated and part of the activation energy is introduced by ultrasound. During the trials, ultrasound of 20 kHz and 550 W were applied. To prevent damage, the oilkatalyst mix has to be filtered via a 10-pm mask filter. Increase of hydrogen pressure and ultrasonic energy as well as increase in the amount of catalyst accelerated the reaction. The authors considered ultrasonic hardening to be a future technology because the reaction rate could be increased 100 times while still allowing for good and constant product quality. They believe that the improvement is due to better hydrogen dispersion, better contact between hydrogen and catalyst as well as higher local temperature and pressure. In the trials, soybean oil was hardened using nickel and copperkhromium catalysts. Output of oil was between 0.5 and 2.0 L/h with a hydrogen pressure of 8 bar and a reaction time of only 9 s.
1SO
-
ul
Y
3 100 $
E c
c
a
f
U
50-
Y
o ' ? 0
Hardened fish oil (I.V. 7580) 4 bar filtration pressure; 0.04% catalyst I ,
"
10
20
30
'
40
, ' I
I
'
SO
Filtrationtime [min]
Fig. 6.143. Filtration of hardened fish oil dependent on the kind of amount of filter aid added.
catalyst and the
598
C W
f
=a
u = t.5
I I
f
-
0.2
U.t8 I
Tol.1 censump!m up to Bth cycb
176 kg of utstfsl I480 I rapmeed MI
Fig. 6.144. Production cycles of hardened rapeseed oil reusing the catalyst (after Klauenberg 1984).
6.5.7 Properties of Hardened Fats and Oils
6.5.7.7 Physical Properties and Properties of Use. As noted at the beginning of this chapter, the reason for hardening is to change the physical characteristics, to improve keepability or to make the oildfats suitable for special use (Table 6.42). Between nonhardened and fully hardened oil and fat, there is theoretically a continuum of infinite stages of hardening. By selecting the right catalyst and processing conditions, a large range of melting points can be reached in the end product. For different oils, common stages of hardening have been developed in the marketplace and are standard for all hardening plants. In addition, specialties are
Modification
of Fats and Oils
599
TABLE 6.42 Melting Points of Fully Hardened Fats/Oils Hardened Coconut oil Palm kernel oil Palm oil Cottonseed oil Peanut oil Rapeseed oil (HEAR) Rapeseed oil (LEAR) Soyabean oil Sunflower oil Fish oil Whale oil
Iodine value
Melting point ("C)
<1 <1 <1 <2 <1 <2 <2 <1 <1 <3 <3
33-35 37-39 58-59 67-70 65-67 70-72 68-70 68-70 69-72 52-57 52-56
produced. The DGF working group (1978) tried to group hardened fats and oils that are used in the food industry (Table 6.43). The main application for semiliquid and soft fats is in the area of industrial baking. This development began in the US.where lard is also slightly hardened. This process, which for the time being is not allowed in parts of Europe, significantly improves the baking properties. Some of these products are produced as branded products for artisanal bakers; others are specialized, confectionated products for large industrial bakeries. These products are produced to meet special demands for particular processes and may contain added ingredients. These are typically emulsifiers such as mono- and diglycerides. Special treatment of such fats is described in Chapter 8. Soft fats can be used for industrial deep frying and could replace peanut oil which was common but is now very expensive. In addition to its influence on the melting point, hardening can have additional positive effects. Slight hardening can improve soybean oil for instance. For a long time (Durkee 1944), it has been known that the seed taste in soybean oil can be avoided if it is slightly hardened. In addition, if hardened to an IV of -90, linolenic acid completely disappears, leading to much better keepability as well as oxidation and heat stability. The increase in TABLE 6.43 Attempt to Group Hardened Fats Used in the Food lndustrya Solids content at
Trans FA
20°C
30°C
content
1
Melting point ("C)
(%)
( O/O 1
30 50 65 00
<2 0 24-36 42-44 30-70
0- 5 40- 60 50- 80 90-100
Degree of hardening Group I II 111 IV
Fat type Semiliquid soft Hard Fully hardened
%ource: DCF (1978)
15302090-1
0 5-20 30-60 5-90
( O M
10-30 30-65 1 0-50 1-10
600
Fats and Oils Handbook
melting point during hardening is dependent on the selectivity because it is determined mainly by the amount of saturated fatty acids formed. As noted in Chapter 6.5.5, these widely influence the end products (Table 6.44). Hardening, profiting from today’s technological possibilities, allows the characteristics of an oil to be changed over a wide range (Fig. 6.145). The darker area shows the characteristics of commonly used products; above the straight line, any selectivity is missing. It can be seen that a wide range of properties can be covered in the case of soybean oil, which is represented in the figure. However, it also becomes evident that a limit is set by the fatty acid composition that makes it impossible, for example, to reach cocoa-butter characteristics (dot) by soybean oil hardening. This can be achieved only with other source material and combining modification techniques (see Chapter 6.2). 6.5.7.2 Nutritional Characteristics. Hardening of fats and oils is a technique that allows better use of oils; oils are the dominant portion of the triglycerides. Although hardening offers a much higher potential to the agricultural community to market their products, on a whole, it is seen as narrowing the market for other products, such as milk fat. Aside from scientific research, which has dealt with hardening in an unbiased manner, attempts have been made to condemn the process globally on grounds that it is “doubtful.”Until now, all suspicions have always proven groundless. The first attacks were aimed at the nutritional value of hardened oils and fats. Deuel (1954) demonstrated that the digestibility of vegetable oils lies between 94 and 98% and, for tallow, it is between 82 and 93%.Hardened cottonseed and hardened peanut oil also fall within these ranges. Generally, digestibility depends on the melting point. Fat melting below 45°C is resorbed at 95-99%; there is no difference between native and hardened oils. Lang (1970) also rejected any nutritional reproaches against hardened oils. Minor lipid components such as tocopherols (Olcott 1934) and sterols (Parodi 1975) are not hydrogenated even under drastic process conditions and thus remaining totally untouched. In addition to the physical properties, hardening also partly changes the configuration of the fatty acids, i.e., tram fatty acids are formed. According to research done to date, there are no indications at all that these fatty acids are unnatural and therefore can be harmful for humans, as was suspected in the 1970s. It has been confirmed repeatedly that there is no connection between atherosclerosis and trans fatty acid intake. To avoid any feeling of uncertainty, a consensus report has recently been agreed upon. Seher (1985) compiled findings on many aspects of trans fatty acids and could find no harmful aspect. Modem analytical techniques have proven that all t r m fatty acids formed during vegetable oiyfat hardening are also found in native fats, mainly ruminant fats such as milk fat. Mammals contain up to 20%of these trans fatty acids in their body fat, and in kangaroos, even more. Ruminants form TFA in their stomachs during bacterial hydrogenation. They are transferred into the fat of their milk and comprise up to 7%(sometimes more) of its fatty acid content (Fig. 6.146).
TABLE 6.44 Characteristicsof Fats and Oils Hardened under Different Process Conditions= ~
Process conditions catalyst Oillfat Soybean oil
Sunflower seed oil
Cottonseed oil Coconut oil Rapeseed oil Palm oil Fish oil (IV = 160) =I, II and 111 as in Table 6.43.
Type
Conctr. (Yo)
Temp. ("C)
Press. 3.5 3.0 3.0 2.0 2.0 2 .o 2 .o 3.5 3.0 3 .O 3.5 2.0 3.5 3.5 3.5 3.5 3 .O
I II II 111 111 111 111 I
0.09 0.09 0.09 0.45 0.45 0.9 0.9 0.09
II
0.09
I1 I 111
I I II
0.09 0.09 0.45 0.09 0.2 0.09 0.45
180 140 180 180 180 180 180 180 140 140 180 180 180 180 180 1501180
II
0.45
150118 0
I
(bar)
Time (min) 40 80 35 80 150 90 40 40 80 100 45 90 100 40 100 55 90 45
~~
~~~~
Solids at
Melting point
20°C
30°C
("C)
IV
(YO)
(YO)
36 28 36
74 79 73
23 12 25
13 4
30 36 30 36 34 28 33 31 31 34 34 56 34 38 34
90
20 45
79 89 77 70 88 80 80 82 1 75 8 75 65 72
30 55 31 10 17 17 30 54 25 97 25 40 24
ga3
15
n
4 25 7 30 15 3 5 5 10 8 10 95 12 27 11
h
6. 3 $
6 fi
:
3
0
z-
Fats and Oils Handbook
602
Fig. 6.145. Solids ranges for hardened soybean oil (after Coenen 1976).
Untreated oilseeds themselves contain virtually no trans fatty acids. In the late 1970s, Heckers et al. (1979) found for Germany (FR) that 4% of the total fatty acids were trans fatty acids of which 5 5 4 0 % came from partially hardened oil and 3 5 4 5 % from animal fat. Recent media coverage, starting in the US., has again triggered a discussion on trans fatty acids. A publication of Willett et al. (1993), who evaluated an epidemiologic study carried out on nurses over the past 20 years, received major media attention all over the world. The main conclusion that Willett drew from this study was that
Fig. 6.146. Trans fatty acid positional isomers in milk fat and in hardened vegetable oil (after Linsen 1971).
603
Modification of Fats and Oils
TABLE 6.45 Trans Fatty Acids in Vegetable Fats and Oils Depending on Processing Steps ~~~
~
1995 CMP, European Standards Oilseeds Crude oil Refined oil Fats, partially hydrogenated Fats, fu IIy hydrogenated
traces <0.7% <2.5% Depending on degree of hardening and processing conditions
<0.2%
1997 GMP, European Standards traces
<0.5% < 1.0% Depending on degree of hardening and processing conditions <0.1%
trans fatty acids increase the risk of coronary heart disease. From several further studies with trans fatty acids, it now indeed appears that at relative high intakes, replacing cis fatty acids by their trans counterparts leads to an increase of LDL (“bad”) cholesterol and a small decrease of HDL (“good”) cholesterol. On the basis of these trials, including well-designed studies employing realistic levels of trans fatty acid intake (Katan et al. 1995), it is now generally accepted (see, for example, The Report of the British Nutrition Foundation on Trans Fatty Acids, 1995) that trans fatty acids could be grouped together with saturated fatty acids from a cardiac health point of view. Consequently, many margarine producers changed the fat compositions of their products to reduce trans content. This trans came mainly from hardening but also from oil refining (Korver and Zevenberger 1995) as well as in very low amounts from oil extraction (Table 6.45). Therefore, the processing conditions of these processes had to be adjusted and, more importantly, the fat compositions of most fat products have been changed. The latter is also leading to a change in the choice of raw materials in margarine and shortening making. In Europe, margarines now contain only very low levels of trans fatty acids; Table 6.46 presents the situation in Austria as an example. Only in single-oil margarine and some products serving special purposes is more research still required to achieve contents below their present values of 5%. Summarizing, it can be said TABLE 6.46 Trans Fatty Acids Content of Austrian Household Fat Productsd Trans fatty acids content Product Vegetable oil Shortening Sot7 shortening Margarine Half-fat margarine Lard Butter aSource: Bockisch (1 996).
(YOof fat phase)
(% of product)
<1
<1
-0
-0
<5 <1 <1 <1 3.5-8
<5 <1 <0.5 <1 3-7
604
Fats and Oils Handbook
TABLE 6.47 Trans Fatty Acids (TFA) intake in Austriaa
Appr. share in total fat intake Product Butter Lard Invisible animal fat Margarine Vegetable fats Vegetable oils Total
Before 1994 0.32 0.01 0.90 0.81 1.20 0.04 3.28
1996 0.32 0.01 0.90
0.06 0.24 0.04 1.57
Appr. share in total TFA intake Before 1994 10.3 0.3 27 25 37 0.1
1996 20 0.6 57
4 15 3
aSource: Bockisch (1996).
that there is a drive for lower trans in vegetable oil and far products that has led to much lower intake of trans fatty acids and a shift in intake of the main TFA source from margarine and vegetable fat to animal fat and butter (Table 6.47). From time to time, nickel residues in hardened fat have also become a subject of discussion. Nickel is ubiquitous in many foods as a trace element in which it can be more or less enriched. Here also Seher (1985) compiled all evidence and discovered the following. Vegetable foods (not oils and fats) contain up to 3 ppm of nickel; some contain more such as legumes, which have up to 5 ppm, and spinach with up to 15 ppm. After a hardened oiYfat has been fully refined (see Chapter 7), its nickel content is on the order of 0.1 ppm. This was also confirmed by Schroder et al. (1962), who analyzed margarine. Currently, these values are even lower, usually ~ 0 . 0 3ppm. The average daily human intake of nickel from mainly animal food is -3-10 mg/d, and from mainly vegetable food, -700-900 mg/d. This is very far from any amount that could be taken in via hardened fat (300 mg/d would require 10 ton of fat as a source). A comprehensive overview of research to date concerning the nutritional aspects of hardening is given by the DGF (German society for fat research). This overview proves that no impairment can be expected from hardened fat, nickel traces from hardening or trans fatty acid formation. 6.6 References Albright, L.F., (1%5) Quantitative Measure of Selectivity of Hydrogenation of Triglycerides, J. Am. Oil Chem. Soc.42,250-253. Allen, R.R., (1982) Hydrogenation, in Bailey's Industrial Oil and Fat Products, (Swern, D., ed.),John Wiley & Sons, New York. Alfa Laval, Alfa Laval, Technical Information, Turnba, Sweden. Alfa Laval, Kombinierte Umesterung und Fraktionierung zur Herstellung spezieller Fettprodukte. Alfa Laval, Semicontinuous Hydrogenation Systems.
Modification of Fats and Oils
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Alfa Laval, Development in Crystallization and Fractionation for Palmoil and Palmkernel Oil Products, Bauren, L. (1987) Vortrag Seminar on Investment Opportunities in the Oils and Fats Industry, Kimia, Malaysia. Alfa Laval, Lipofrac, Fractionation of Fatty Oils and Fatty Acids. AMA, h a Filter b.v., see Chapter 7. Andersson, C., and Larsson, R., (1981) Investigations on the Condition for Hydrogenation of Fatty Oils with Polymer Anchored Pd-Phosphine Complexes, J. Am Oil Chem SOC. 58, 675-580. Andersson, K., quoted from DGF Die Hydrierung von Fetten. Andersson, K., Hell, M., Liiwendahl, L., and Schon, N.H., (1974) Diffusion of Hydrogen and Glycerol Trioleate in Cottonseed Oil at Elevated Temperature, J. Am. Oil Chem SOC. 51, 171-177. Asahi Chemicals,Technical Information. Baltes, J., (1975) Gewinnung und Verarbeitung von Nahrungsfetten, Paul Parey Verlag, Berlin. Banks, W., Clapperton, J.I., and Girdler, A.K., (1985) On the Fractional Melting of Milk Fat and the Properties of the Fractions,J. Sci. Food Agric. 36,421-432. Bailey, A.E., (1949) Theory and Mechanisms of the Hydrogenation of Edible Fats, J. Am Oil Chem. SOC. 26,596-601. Bailey, A.E., (1950) Practical Melting and Solidification Processes, in Melting and Solid&ation of Fats, pp. 328-333, IntersciencePublishers, New York. Becker, R.R., and Doring, W., (1935) Kinetische Behandlung der Keimbildung in iibersattigten DZimpfen, Ann. Physik 24,719-752. Berglund, M., and Andersson, C., (1984) Hydrogenation of Soybean Oil with Cationic Rh(i)Phosphine Complexes as Catalysts-Paratoluene Sulfonate and Sulfonted Styrene Resins as Counterions,J. Am. Oil Chem SOC. 61, 1351-1353. Bemardini, E., (1985) Oilseeds, Oils a d Fats, Publishing House BEOil, Rome. Bhattacharyya,S., Bhattacharyya,D.K., Chakraborty,A.R., and Sengupta,R., (1989) Enzymatic Deacidification of Oils, Fat Sci. Technol. 91,27-30. Bockisch, M., (1996) Speech delivered at the Austrian Food Chemists’ Annual Convention, Graz.
Brockaw, G.Y., U.S. Patent 2,879,281(1959). Broeker, U.S.Patent 3,896,053 (1975). Burgers, J., Mott, C.W., and Seiden, P., US.Patent 3,170,798 (1965). Butterfield,R.O., and Dutton, H.J., (1967) Digital Computer Program for Calculating Selectivity of Hydrogen Catalyses,J. Am. Oil Chem. SOC.44,549-550. Caceres, L., Diosady, L.L., Graydon, W.F., and Rubin, L.J., (1985) Supported Gold Catalysis in the Hydrogenation of Canola Oil, J. A m Oil Chem. SOC.62,906-910. Cecchi, G., Castano, J., and Vaciani, E., (1979) Catalyse par les Mttaux M i e u x en liphimie, I. Hydrogenation de 1’Huile de Soya Catalys& par les MCtaux M i e u x Support6s,Rev. Fr. Corps Gras 26,391-396. Cecchi, G., Castano, J., and Vaciani, E., (1980) 11. Hydrogenation de la Nouvelle Colza Catalyske par les MCtaux M i e u x Suppartks, Rev. Fr. Corps Gras 27,387-392. Cecchi, G., Castano, J., and Vaciani, E., (1984) 111. Catalyse par Palladium sur Chrbon B Temp5rature Ambiente, et Effet de Solvanf Rev. Fr. Corps Gras 31,243-248. Cecchi, G., Castano, J., and Vaciani, E., (1980) Comparaison de Quelques Catalysateurs pour 1’HydrogCnation Stlective de la Nouvelle Huile de Colza, Rev. Fr. Corps Gras 27, 44347.
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Chabanov, D.G., and Topalova, M.R., (1979) Alterations in Glyceride Composition During Directed Interseterifcation of Lard, J. Am. Oil Chem. SOC. 56,581-584. Charlesworth, P.L., and Schmidt, G., (1965) The Production of Hydrogen to Satisfy Small Industry Demands, The Chemical Engineer, 259. Chayamichi, H., and Kikuchi, H., (1989) Asahi Chemical Industry Co. Tokio 100 and Nisshin Oil Mills Ltd 235, Yokohama, Dewaxing of Sunflower Oil by MicrozaTP-313, Informationsschrift. Chevreuil, M.E., (1823) Recherches sur les Corps Gras. Chou, T.S., Cheng, A.M., (1981) Research Report, Food Industry Research and Development Insitute of Taiwan, Hsinchu, Taiwan. Coenen, J.W.E., Wieske, T., Cross, R.S., and Rinke, H., (1967) Occurrence, Detection and Prevention of Cyclization During Hydrogenation of Fatty Oils, J. Am. Oil Chem. SOC.44, 344-349. Coenen, J.W.E., (1974) Fractionnement et Interesttrification des Corps Gras: dans la Perspective du March6 Mondial des Matikres Premikres et des Produits Fins; 11. Interesttrefication, Rev. Fr. Corps Gras 21,403. Coenen, J.W.E., (1976) Hydrogenation of Edible Oils, J. Am. Oil Chem. SOC.53,382. Coleman, M.H., and MacRae, A.R., (1980) British Patent 1,577,933. Daum, J.P., (1993) Determining the Costs of Hydrogen, INFORM4, 1394 and 1399. Deffense, E., (1985) Fractionation of Palm Oil, J. Am. Oil Chem. SOC. 62,376384. Deffense, E., (1987) Multi-step butteroil fractionation and spreadable butter, Fett WissenschaB Technologie 89. Deffense, E., Technical Information of Tirtiaux S.A. Deuel, H.J., (1954) in Progress in the Chemistry ofFats and Other Lipids, Vol. 2, (Holman and Lundberg, eds.), Pergamon Press, London. Devlin, J.J., and Walker, A.P., British Patent 832,377 (1960). DGF, Die Hydrierung von Fetten, Gemeinschaftsarbeit der Deutschen Gesellschaft fur Fettwissenschaft e.V., Fette, Seifen, Anstrichmittel 78, 385, (1976); 79, 181, 465, (1977); 80, l(1980). DGF, (1973) Die Umesterung von Speisefetten, Fette Seqen Anstrichmittel 75, 467474, 587-593,663-666. Diosady, L.L., Graydon, W.F., Koseoglu, S.S., and Rubin, L.J., (1984) Hydrogenation of Canola Oil in the Presence of Arene Chrome Carbonyl Complexes, Can. Inst. Food Sci. Technol. J. 17,218-223. Dominick, W.E., Nelson, D., and Mattil, K.F., U.S. Patent 2,625484 (1953). Duffy, P., J., (1854) Chem. SOC. 5, 197-210, quoted from Hilditch T.P., and Williams P.N., (1964) The Chemical Constitution of Natural Fats, Chapman & Hall, London. Duns, M.L., (1985) Palm Oil in Margarines and Shortenings, J. Am. Oil Chem. SOC.62, 408-4 10. Durkee, M.M., U S . Patent 2,353,229 (1944). Duveen, R.F., and Leuteritz, G., (1982) Der BUSS-Schleifenreaktor in der 0 1 - und Fetthiktungsinduste, Fette, Seifen, Anstrichmittel 8 4 , 5 11-515. Duveen, R.F., and Steinhauer R., (1984) Ergebnisse aus industriellen BUSSWihnerikkgewinnungs-S ystemen, Fette, Seifen, Anstrichmittel 86,522-525. Eckey, E.W., (1948) Directed Interesterificationin Glycerides, Ind. Eng. Chem. 40, 1183. Eckey, E.W., US.patent 2,558,548 (1951).
Modification of Fats and Oils
607
Filer, L.J., Mattson, F.H., Foman, S.J., (1969) Triglyceride Configuration and Fat Absorption by the Human Infant, J. Nutr. 99,293-298. Fischer, J.C., Holloman, J.H., andTumbul1, D., (1948) Nucleation, J. AppLPhys.19, 775-784. Frankel, E.N., (1979) Homogeneous Hydrogenation of Unsaturated Fats. Applications and Implication, Proceedings of the 13th World Congress, Symposium I, 1-15. Frenkel, J., (1947) Kinetic Theoly of Liquids, Oxford University Press, Oxford. Gander, K.F., (1969) Technologie der Speisefette und Fettprodukte, D. Fraktionierte Fette, in Handbuch der Lebensmittelchemie W ,p. 243, Springer-Verlag, Berlin. Gargan, M., and Rossi, M., (1982) Catalytic Hydrogenation of Vegetable Oils. II: The Quality of the Prereduced Copper Chromite Catalyst, J. Am. Oil Chem. SOC.59, 1159. Going, L.H., (1967) Interesterification, Products and Processes, J. Am. Oil Chem. Soc. 44, A414-422, A454-456. Hack, K.M., and Hall, B.B., (1965) The Production of High Purity Hydrogen from Butane with Special Reference to Materials of Construction and Operating Problems, The Chemical Engineer, CE282. Hahn, G., (1978) Fraktionierung von Palm01 durch selektive Kristallisation an einer gektihlten Flache, Fette, Seifen, Anstrichmittel 80,337-342. Haraldson, G., (1985) Energy considerations, J. Am. Oil Chem. SOC.62,3 11. Haraldson, G., (1987) Kombinierte Umesterung und Fraktionierung zur Herstellung spezieller Fettprodukte, Technische Information a Alfa Laval3045OT. Hawley, H.K., and Dobson, R.D., US.Patent 2,875,066 (1959). Hawley, H.K., and Holmann, G.W., (1956) Directed Interesterification as a New Processing T ~ ofor l Lard, J. Am. Oil Chem. SOC.33,29-35. Heckers, H., Melchers, F.W., and Dittmar, K., (1979) Zum taglichen Verzehr trans-isomerer Fettsauren. Eine Kalkulation unter Zugrundelegung der Zusammensetzung handelsiiblicher Fette und verschiedener menschlicher Depotfette, Fette, Seifen, Anstrichmittel 81,217-226. Heldal, J.A., and Mork, P.C., (1982) Chlorine Containing Compounds as Copper Catalyst Poisons, J. A m Oil Chem. SOC.59,396-398. Hilditch T.P., (1936) in Chemie und Technologie der Fette und Fettprodukte I, Chemie und Gewinnung der Fette, (Schonfeld, H., ed.), Verlag von Julius Springer, Vienna. Hollemann-Wiberg, (1971) Lehrbuch der anorganischen Chemie, Walter de Gruyter Co., Berlin. Holmann, G.W., and Going, L.H., U.S. Patent 2,875,066 (1959). Hou, C.T., and Johnston, T.M., (1992) Screening of Lipase Activities with Cultures from the Agricultural Research Service Culture Collection, J. Am. Oil Chem. SOC.69, 1088-1096. Hsu, N., Diosady, L.L., Graydon, W.F., and Rubin, L.J., (1986) Heterogeneous Catalytic Hydrogenation of Canola Oil Using Palladium, J. Am. Oil Chem. SOC.63,1036-1042. Hugel, E., (1937), Chemie der Fette und Fenprodukte, Vol. II,(Schonfield, H., ed.), Springer, Vienna. Hustedt, H.H., (1976) Interesterificationof Edible Oils, J. Am. Oil Chem. SOC.53, 390. Jensen, R.G., (1974) Characteristics of the Lipase from Mold Geotrichum candidum: A Review, Lipids 9,149. Jensen, R.G., and Pitas, R.E., (1976) Specifity of the Lipase from Geotrichum candidum, in Lipids, (Paolette, Porcellati, and Jacini, eds.), vol. 1, p. 141, Raven Press, New York. Johansson, L.E., and Lundin, S.T., (1980) Copper Catalysts in the Selective Hydrogenation of Soybean and Rapeseed Oils: IV. Copper on Silica Gel, Phase Composition and Preparation, J. Am. Oil Chem. Soc. 57, 16-22.
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Kaufmann, H.P., and Grothues, B., (1958) Umestemgen auf dem Fettgebiet; h e r den E M & verschiedener IV.Tropfpunktstindemng bei Ein- und Mehrfett-Umestemg, Fette, Seifen, Ansm‘chmittel62,489. Kellens, M., Fractional Crystallization of Fats, Society of Chemical Industry, London, 9 Much 1994,Technical Information of de Smef =gem. Kellens, M., New Developments in the Fractionation of Palm Oil, Speech delivered at the 1993 PIPOC PORIM International Palm Oil Congress, Kuala Lumpur, Technical Information of de Smet, Edegem. Kirschner, E., and Lowrey, E.R., (1970) Positioning and Geometrical Isomerhtion During Partial Hydrogenation of Triolein: A Comparison of Copper and Nickel Catalysts, J. A m Oil Chem SOC.47,237. Klauenberg, G., (1984) Hydrierung von Riibol-EinfluB von ProzeBbedingungen und Produktqualitiiten auf Verlauf und ERgebnis der Hydriemg, Fette, Seifen, Anstrichmittel 86,5 13-520. Klauenberg, G., (1986) Personal Communication. Klauenberg, G., (1987) The Hydrogenation of Rapeseed Oil, Technical Information of UNICHEMA International,Emmerich. Klauenberg, G., The Hydrogenation of Edible Oils: The Influence of Prmss Conditions and Feedstock Qualities on the Course and Result of the Hydrogenation, Technische Information der UNICHEMA International,Emmerich. Klein, J.M., (1979) Etude sur le Fractionnement de 1’Huile de Palme; Obtention d’Huiie Fluide d’hdice d‘Iode Supt5rior B 75 et Characteristiquesdes Produits R6sultanf Oleagineux 34, 531-536. Kloosterman, J., van Wassenaar, P.D., and Bel, W.J., (1987) Membrane Bioreactors, Fat Sci. Technol. 89,592-597. Kokken. M.J., Production of Fractionated Fatty Matters and Their Uses, Speech delivered at Joum6e du Printemps,Association Francaise pour 1’Etude des Corps Gras, May 16,1990. Koritala, S., Friedrich, J.P., and Mounts, T.L., (1980) Selective Hydrogenation of Soybean Oil: X. Ultra High Pressure and Low Pressure, J. A m Oil Chem. Soc. 57, 1. Koritala, S., Friedrich, J.P., and Mounts, T.L., (1981) Selective Hydrogenation of Soybean oil: XI. TrialkylsilaneActivated Copper Catalysts,J. Am. Oil Chem.SOC.58,701-702. Koritala, S., Friedrich, J.P., and Mounts, T.L., (1985) Homogeneous Catalytic Hydrogenation of Soybean Oil: Palladium Acetylacetonate,J. A m Oil Chem. SOC. 62,517-520. Korver, O., and Zevenbergen, J.L., (1995) Nutritional Consequences of Oil Refining Processes, in Oil, Fats, Lipidr, Proceedings of the 21st WorM Congress of the International Society for Fat Research, pp. 573-575, The Hague. Kreulen, H.P., (1976) Fractionation and Winterization of Edible Fats and Oils, J. Am. Oil Chem SOC.53,393-396. Lang, K., (1970) Biochemie der Emiihrung, Dr. D. Steinkopff-Verlag,Darmstadt. Linsen, G.B., (1971) Selektivitat der Fetthydrierung, friiher und heute. 11, Fette, Seifen, Anstrichmittel 71,753. Lo, Y.C., and Handel, A.P., (1983) Physical and Chemical Properties of Randomly Interesterified Blends of Soybean Oil and Tallow for Use as Margarine Oils, J. A m Oil Chem SOC. 60,815-818. Loders Croklaan; Facts about Fats, Fat Systems in Chocolate, Technical Information, Loders Croklaan B.V. Hogeweg 1, NL-1520 AA Wormerveer,The Netherlands.
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609
Luddy, F.E., Moms, S.C., Magidman, P., and Riemenschneider, R.W., (1955) Effect of Catalpc Treatment with Sodium Methylate on Glyceride Composition and Properties of Tallow and Lard, J. Am. Oil Chem SOC.32,522. Lysjanski, V.M., Popov, W.D., Redko, F.A., and Stabnikov, W.N., (1983) Velfahrenstechnische Grundlagen a’er Lebensmitteltechnik. MacRae, A.R., (1983) in Microbial Enzymes and Biotechnology, (Fogarty, ed.),p. 225, Applied Science Publishers, London. MacRae, A.R., (1984) Microbial Lipases as Catalysts for the Intersterification of Oils and Fats, in Biotechnologyfor the Oils and Fats Industry, (Ratledge, Dawson, and Ratfny, eds.), pp. 189-198, American Oil Chemists’ Society, Champaign, IL. Matsuo, T., Sawamura, N., Hashimoto, Y., and Hashida, W., British Patent 2,035,359A (1981). Mattil, K.F., and Nelson, D., U.S. Patent 2,625,483 (1953). Matz, G., (1969) Kristallisation, Grundlagen und Technik, Springer Verlag, Berlin. Matz, G., (1970) Mittlere Kristallwachstumsgeschwindigkeit des Einzelkorns, Chem. Zng. Technol. 42, 11341141. McCabe, W.L., and Stevens, R.P., (1951) Rate of Growth of Crystals in Aqueous Solutions, Chem.Eng. Prog. 47,168-174. Mersmann, A., (1982) Auslegung und MaBstabsvergroOemg von Kristallisatoren, Chem.Zng.Technol. 54,631-643. Momsson, W., and Robertson, J.A., (1978) Effect of Drying on Sunflower Seed Quality and Germination,Sun. News 4,17-19. Moulton, K.J., and Kwolek, W.F., (1982) Continuous Hydrogenation of Soybean Oil in a Tricle and Reactor with Copper Catalyst, J. Am Oil Chem SOC.59,333-337. Moulton, K.J., Kwolek, W.F., Koritala, S., and Frankel, E.N., (1983) Ultrasonic Hydrogenation of Soybean Oil, J. Am Oil Chem.SOC.60, 1257. Moulton, K.J., Kwolek, W.F., Koritala, S., Warner, K., and Frankel, E.N., (1987) Continuous Ultrasonic Hydrogenation of Soybean Oil II. Operating Conditions and Oil Quality, J. Am. Oil Chem. SOC.64,542-547. Mounts, T.L., Koritala, S., Friedrich, J.P., and Dutton, H.J., (1978) Selective Hydrogenation of Soybean Oil: IX,Effect of Pressure and Copper Catalyst, J. Am Oil Chem SOC.55,402. Muderhwa, J.M., Pina, M., and Graille, J., (1989) Intefisterification Cataly& par les Lipases RkgiosBlectives 1,3 en Milieu Fondu: Applications h 1’Huile de Palme et h Sa Fraction Concrkte, Rev. Fr. Corps Gras 36,ll-16. Mukherjee, K.D., Kiewitt, I., and Kiewitt, M., (1975) Stationary Catalysts for the Continuous Hydrogenation of Fats, J. Am. Oil Chem.SOC.52,282. Mullin, J.W., (1972) Crystallization,Butterworth, London. Nelson, D., and Mattil, K.F., U.S. Patents 2,625,486 and 2,625,487 (1953). Nicolet, B.H., (1920) Some Anomalies in the Solidifation Point of Tristearin, J. Znd. Chem. Eng.Pard 12,741-742. Nomann, W., (1938) Die Hiirhmg von Walol und die Verwendung von g e h w t e m Walol in der Margarine-Herstellung, Fene und Seifen 45,73-76. Okkerse, C., de Jonge, A., Coenen, J.W.E., and Rozendaal, A., (1%7) Selective Hydrogenation of Soybean Oil in the Presence of Nickel Catalysts, J. Am. Oil Chem SOC.44,152. Olcott, H.S., (1934) Some Chemical Properties of Vitamin E, J. Biol. Chem 105,65. Oliver, G.D., and Bailey, A.E., (1945) Thermal Properties of Fats and Oils V. The Heat Capacity and Heat of Fusion of Highly Hydrogenated Cottonseed Oil, Oil & Soap 22, 3941.
61 0
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Ong, T.L., (1979) Proceedings of a Quality Control Seminar in Soybean Crushing Plants and Soybean Processing Plants, American Soybean Association, Brussels. Organikum, (1974) Autorenkollektiv,VEB Verlag der Wissenschaften, Berlin. Pardun, H., (1969) Analyse der Fette und Fettbegleitstoffe, in Handbuch der Lebensmittelchemie,Vol. IV,p. 481, Springer Verlag, New York. Pardun, H., (1976) Analyse der Nahrungsfette, Paul Parey Verlag, Berlin. Parodi, P.W., (1975) Fate of Dietary Sterols in Hydrogenated Fats and Oils, J. Am. Oil Chem. SOC.52,345. Patterson, H.B.W., (1974) The Hydrogenation of Vegetable Oils and the Production of Vegetable Ghee, UNIDO Publication 1D/124, New York. Patterson, H.B.W., (1983) Hydrogenation of Fats and Oils, Applied Science Publishers, London. Patterson, H.B.W., (1994) Hydrogenation of Fats and Oils: Theory and Practise, AOCS Press, Champaign, IL. Paulicka, F.R., (1976) Speciality Fats, J. Am. Oil Chem. SOC.53,421424. Perry, R.H., and Chilton, C.H., (1973) Chemical Engineers Handbook, McGraw Hill, Tokyo. van Putte, K.P.A.M., and Bakker, B.H., (1987) Crystallization Kinetics of Palm Oil, J. Am. Chem. SOC.64,1138-1 143. Ray, J.D., (1985) Behavior of Hydrogenation Catalysts: I. Hydrogenation of Soybean Oil with Palladium, J. Am. Oil Chem. SOC.62, 1213-1217. Ravich, G.B., Tsurinov, G.G., Volnova, V.A., and Petrov, N.P., (1946) Acta Physiochirn URSS 21, 101-108. Reinders, W., Doppler, C.L., and Oberg, E.L., (1932) h e r das Schmelzen und Erstarren von Kakaobutter (niederl.), Rec. Trav. Chirn Pays-Bas 51,917-937. Ricci Rossi, G., and Deffense, E., (1984) Erfahrungen mit der Fraktionierung von Fetten nach dem TIRTIAUX-Verfahren, Fette, Seifen, Anstrichmittel 86,500-504. Richardson, AS., Knuth, C.A., and Milligan, C.H., (1924) Heterogeneous Catalysis, Znd. Eng. Chem. 16,519-522. Rossell, J.B., (1975) Differential Scanning Calorimetriy of Palm Kernel Oil Products, J. Am. Oil Chem. SOC.52,505-5 11. Rossell, J.B., (1985) Fractionation of Lauric Oils, J. Am. Oil Chem. SOC.62,385-390. Rozendaal, A., (1979) New Trends in Heterogeneously Catalized Hydrogenation of Oils and Fats, Proceedings of the 13th World Congress, Symposium I, pp. 43-70. Rozendaal, A., (1990) Interesterification of Fats, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 152-157, American Oil Chemists' Society, Champaign, IL. Rudischer, S., (1959) Fachbuch der Margarineindustrie,Fachbuchverlag, Leipzig. Sabatier, P., and Senderens, J.B., (1901) Comptes rendues 210, 132 quoted from Hilditch, T.P., and Williams, P.N., (1964) The Chemical Constitution of Natural Fats, Chapman & Hall, London. Sattler, R. (1977) Thenische Trennverfahren,Vogel Verlag, Wiirzburg. Schmidt, H.J., (1968) Hydrogenation of Triglycerides Containing Linolenic Acid I: Calculation of Selectivity, J. Am. Oil Chem. SOC.45,520. Schroder, H.A., Balassa, J.J., and Tipton, I.H., (1962) Abnormal Trace Metals in Man-Nickel, J. Chron. Dis. 15,5145. Seher, A., and Zippel, G., (1969) Dekontamination von Olen, Olsaaten und -friichten von Casium 137, Fette, Seifen, Anstrichmittel 71,948-95 1.
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61 1
Seher, A,, and Zippel, G., (1985) Biologische Wirkung hydrierter und umgeesterter Fette, Bibliotheca Nitritio et Dieta 34,96109. Serfass, E.J., and Silman, H., (1965) Hydrogen Production and Purification by the Diffusion Process, The Chemical Engineer, CE266. de Smet, Extraction de Smet S.A., Edegem, Belgium, Technical Information: Oil and Fat Fractionation, the De Smet Winterizing Process, the De Smet Miscella Winterizing Process de Smet, Extraction de Smet S.A., Edegem, Belgium, Techincal Information: Oil and Fat Fractionation, Winterization Continued. Snyder, J.M., and Scholfield, C.R., (1982) Reuse of Copper Catalyst in Continuous Hydrogenation, J. Am. Oil Chem. SOC.59,420-421. Sreenivasan, B., (1978) Interesterificationof Fats, J.Am. Oil Chem. SOC.55,796805. Sreenivasan, B., U.S. Patent 3,859,447 (1975). Steiner, R., (1955) Die Kristallisation der Kakaobutter und anderer Fette I: Ein adiabatisches Kalorimeter und seine Verwendung zur thermischen Analyse von Kakaobutter, J. Sci. Food Agric. 6,777. Stover, H.M., Eggers, R., and Stein, W. (1983) Speiseolfraktionierung, Fette, Seifen, Anstrichmittel 85,534-538. Szukalska, E., and Drozdowski, B., (1982) Selective Hydrogenation of Pareoils with Copper Chromite Catalysts: Influence of Erucic Acid, J. Am. Oil Chem. SOC.59, 134-139. Tammann G., (1903) Kristallisieren und Schmelzen, Bart-Verlag, Leipzig. Tammann G., (1932) Aggregatzustunde,Leipzig. Tanaka, T., Ono, E., and Takinami, K., British Patent 2,042,579A (1980). Taylor, H.S., (1925) Proc. R. SOC.(Lond.)A108, 105-1 11, quoted from Allen. Teasdale, B.F., and Helmel, G.A., U S . Patent 31,174,868 (1965). Thomas, K.C., Magnuson, B., McCurdy, A.R., and GrootWassink, J.W.D., (1988) Enzymatic Interesterificationof Canola Oil, Can. Inst. Food Sci. Technol. J. 21, 167-173. Tirtiaux, Tirtiaux Fractionnement S.A., Fleurus, Belgium, Technical Information. Tirtiaux, A., Theory and Practice of Fractionation, Deffense, E., (1985) Speech delivered at ‘Teachin’ on Fat Modi@cation,Chester. Tirtiaux, A., and Deffense, E., Industrial Application and Analytical Data, Speech delivered at American Oil Chemists’ Society World Conference,The Hague, 1982. Tirtiaux, A., and Deffense, A,, Winterization of Hydrogenated Soybean Oil, American Oil Chemists ’ Society 75th Conference,Dallas, 1984. Tirtiaux, A., and Deffense, E., Fractionation, a Fast Growing Technique, Speech delivered at the 80th American Oil Chemists’ Society Conference, Cincinnati, 1989. Tirtiaux, A., Progrks Rkcents dans le Fractionnement de 1’Huilede Palme, Rev. Fr. Corps Gras, Mai 1989. Tirtiaux, A., (1990) Dry Fractionation: A Technique and an Art, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 136-141, American Oil Chemists’ Society, Champaign, IL. Touraine, F., and Drapron, R., (1988) Influence of Water Activity on Glyceride and Glycol Esters; Synthesis by Lipase from Rhizopus arrhizus, Can. Inst. Food Sci. Technol. J. 21, 255-259. Ubbelohde, A.R., (1937) Thermodynamics and the Velocity of Irreversible Processes, Part II. Chemical Reaction Velocity, Trans. Faraday SOC.33, 1198-1212. Ucciani, E., Cecchi ,G., and Bonfand, A., (1982) Prkparation d’un Nouveau Catalysateur au Cobalt et Etude de Ses Proprietds en Lipochimie, Rev. Fr. Corps Gras, 29,219-225.
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Ueno, S., (1918) Regarding Catalyst Poisons in Fats and O i l s Hydrogenation, J. Soc. Chem. Id.Jpn. 21,898-939. UNICHEMA, Unichema International, Emmerich, Technical Information. Unichema, Osinga, T.J., and Balemans, A.C.F., Re-Use of Catalyst in Fish61 Hydrogenation. Unichema, Informationen iiber die Anwendung von PRICAT Nickel-Katalysatmn. Unichema, Application Information on Pricat Nickel Catalysts. Unichema, 70 Jahre Katalysator-Herstellung in Emmerich. Unichema, SupportedNickel Catalyst. Unichema, Klauenberg,G., The Hydrogenation of Edible Oils, Influence of Process Conditions. Unichema, PRICAT 9900. Unichema, PRICAT 9906. Unichema, Herstellung von Nickel-Katalysatoren. Unichema, The Hydrogenation of Rapeseed Oil. Unichema, The Hydrogenation of Edible Oils and Fats. Vanderwal,R.J.,andvanAkke~n,L.A.,U.S. Patent2,571,315(1951). Voeste, T., (1973) iibeT ein neues Verfahren zur Herstellung von Wasserstoff aus Methanol, Fette, Seijen, Anstrichmittel 75,360-362. Walkden, R.A.B., (1988) AlternativeFats to Cocoa Butter, Food T e c h l . In?.,21 1-214. Wieske, T., (1%9) Personal Communication. Willett, W.C., Stampfer,M.J., and Manson, J.E., (1993) Lancet 341,581-585. Williams, K.A., (1927) Melting Point of Hydrogenated Cotton-SeedOil, J. Soc. Chem. I d . 46, 448-449. Willner, T., Sitzmann, W., and Miinch, E.-W., (1989) Herstellung von Kakaobutterersatzdurch fraktionierteSpeiseijllvistallisation,Fat Sci. T e c h l . 91,586592, Willner, T., Sitzmann, W., and Miinch, E.-W., (1990) Production of Cocoa Butter Replacers by Fractionation of Edible O i l s and Fats, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 239-244, American Oil Chemists’ Society, Champaign,L. Young, F.V.K., (1985) Interchangeability of Fats and Oils, J. Am Oil Chm Soc.62,372-376. Zajcew, M., (1%5) Palladium Catalyst for Hydrogenation in the Fats Industry, Engelhard Id, Tech. Bull. 4, 121-124. Zeitoun, M.A.M., Neff ,W.E., List, G.R., and Mounts, T.L., (1993) Physical Properties of Intersterified Fat Blends, J. Am. Oil Chem Soc. 70,467-47 1.
Chapter 7
Oil Purification
Fats and oils contain undesired by-products or impurities. These depend on the kind of oil, the seed treatment, the extraction process and the storage conditions. They must be removed. Impurities can negatively influence the taste and smell of the oil as well as its appearance, thus reducing consumer acceptance and marketability. They can also limit the use and further processing of the oil. In addition, there are some impurities that may be unhealthy or at least be regarded as such by the public, even if this view is objectively not justified. To the latter group belong all of the environmental contaminants that are ubiquitous today, such as pesticides, herbicides and heavy metals. The same holds true for aflatoxins, which are metabolic products of certain fungi. Undesired substances in animal fats include blood colorants and their decomposition products and colorants from plants in vegetable oils. Metals promote fat oxidation. In some countries, refining of animal fat is not generally allowed. In Germany, for example, it can be done only with a special permission if the refined fats are to be used in margarine. Because refmed animal fats can be produced for export., this regulation must be viewed as a protectionist measure that has nothing to do with consumer protection. Refining is usually done in four steps (Fig. 7.1). It can be done by conventional processes, which include chemical refining or, following more recent techniques, by using physical refining (Fig. 7.2). The physical process is technically more costly. However, it quires only two processing steps, whereas the conventional process may need up to six. The main advantage of physical refining is its environmental fiiendliness. The effluent is drastically reduced, the fatty acid is recovered as such without soap splitting and there is a lower refining loss. The disadvantage is that some oils crude cil sactkn
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Fats and Oils Handbook
614
Crude oil
I
I
Bleaching (earth)
Bleaching (heal)
L
+
t
I
Refining fatty acids
I
Distillative nevtralization Decdonzation
Decdonzalion
-+
-
+
t
t
I Fully refined oil
Fig. 7.2. Process steps of chemical and physical refining.
must be more carefully degummed than for the conventional process. Not all oils can yet be physically refined (see Chapter 7.5). Most of the refineries in operation today are composed of the equipment described in the following. The types described stand for certain construction or processing principles. This equipment is offered by more manufactures than mentioned in the examples. The equipment is especially chosen to best serve the purposes needed or the plants have simply grown over time. Batch vessels for neutralization have an almost unlimited lifetime, so that their replacement by more modern equipment is often not economical in smaller factories. There is a significant difference in the design of refineries depending on their purpose. Refineries attached to oil mills, for example, are usually run continuously because they have to process large quantities of the same oil over relatively long periods. Refineries feeding margarine factories have to run small batches of changing composition; therefore they are usually discontinuous or semicontinuous. Special treatment is needed for palm oil because of its higher free fatty acid (FFA) and high concentration of carotenes (see Chapter 4.2.1). Refining processes have improved significantly over the past 40 years. This becomes apparent if capacities, energy consumption, effluent and oil losses are compared over a time span of 30 years (Fig. 7.3). This development will continue in the years to come and will also be driven in part by environmental preservation, a process that is often enhanced by increasing taxes or payments for emission.
7.1 Economic Importance of Refining Practically the entire amount of vegetable oils and fats produced worldwide and sold in the industrially developed regions is refined. Only olive oil is sold unrefined as virgin oil. Among the animal fats, all fish oil is refined, typically after hardening. Slaughter fats often remain unrefined, mainly because of legal regulations. Milk fats are rarely refined. Without refining, most of the oils and fats could not be used for
Oil Purification
61 5
Fig. 7.3. Achievements in the refining process at the end of the 1980s compared with 30 years before (after Thomas and Lau 1988).
nutritional purposes. In the following paragraphs, refining is described without the degumming step. Although degumming is part of the refining process, it is usually performed in the oil mills; therefore it is described in Chapter 5.
7.2 Neutralization Directly after harvesting (during ripening for pulp oils), lipolytic processes start in the oilseeds. These may cause enzymatic or microbial hydrolysis of the fat. All processes are enzymatic with the enzyme stemming from the seed or the pulp or being produced by the microorganisms. Additionally, chemical hydrolytic and oxidative processes start that cause the formation of FFA. These fatty acids have to be removed because they limit the use of the fat. Traded crude seed oils or fats contain 1-3% FFA, good batches 50.5%. In some batches of palm, olive or fish oil, up to 20% FFA may be found. Well-refined oils have a maximum of 0.1% FFA (depending on further usage). There are several methods of neutralization that have all been tested for large-scale use. Most processes that have been developed, however, are not suitable for industrial production or have not succeeded in the market. Principally, one can distinguish between physical and chemical processes. Physical processes include distillative removal of FFA, steam distillation, selective adsorption of the FFA and selective extraction of the FFA. Chemical processes include re-esterification of the FFA with glycerol, neutralization of the FFA with alkali lye and neutralization of the FFA with ammonia. All methods cause different neutral oil losses, which add up in the total refining loss.
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61 6
7.2.1 Physical Methods
7.2.1.1 Distillative Removal of FFA. Distillative removal of FFA is part of a process that as a whole is called physical refining. It is described in Chapter 7.5. 7.2.1.2 Selective Adsorption of FFA. Adsorption of FFA on silica gel or aluminum oxide has been proposed and tested with moderate success. Only adsorption on ion exchangers has delivered good results. The application of strong basic quartemary ammonium salts yielded very good test results in the laboratory, but could not be extended into practice. 7.2.1.3 Selective Extraction of FFA. If oils have a very high concentration of FFA, these can be selectively separated with solvents. Several attempts to introduce such processes have been proposed. Some of them are listed below. If olive oil with an FFA > 20% is extracted with ethanol, it is possible to bring down the FFA to values 4%(Gander 1%9). Anoaher solvent that proved to selectively dissolve FFA and highly unsaturated triglycerides at suitable temperams is furfurol. Liquid p r o p , which is used countercurrently(Solexol process), selectively dissolves saturated neutral oil, whereas fatty acids, oxidation products, unsaponifiable matter and the higher unsaturated glycerides are almost untouched. This process is usually applied to the extraction of fish and fish liver oils (see Chapter 3.3). Hofelmann and Steiner (1993) used supercritical propane for the extraction of rapeseed oil, but the investment cost remains too high to allow its use for ordinary products. On an industrial scale, the process of selective extraction is applied only for fats with very high FFA content, such as cccoa fat from the hulls, olive oil from the press cake and poor qualities of rice bran and cottonseed oil (processing scheme: see Fig. 7.4). Isopropanol may also serve in this process as the alcohol component. To neutralize 1 ton of oil, Bemardini (1985) gave the following consumptions of energy and processing aids: steam (3 bar), 800 kg; electrical energy, 14 kwh; hexane, 15 kg; and isopropanol, 18 kg. Such oil is not used as edible oil. 7.2.2 Chemical Processes
7.2.2.1 Re-esterification with Glycerol. The reaction equation of fatty acids and glycerol to yield fat is as follows:
glycerol + fatty acids + fat + water
f7.11
Following that reaction, from the right to the left (fat splitting), FFA are formed. This fat splitting can also be enforced by applying a pressurep > 3 MN/m2 (30 kg/cm2) in the presence of water. In refined oils and fats, fat splitting is usually caused by enzymatic processes. Going from the left to the right, re-esmification takes place if an excess of glycerol is present under reduced pressure and at high temperature ( t > 250°C).The pressure should not be higher than 5-6 hPa If catalysts (for example,
Oil Purification
61 7
Neutralzed oil
Fig. 7.4. Neutralization with alcohol and hexane (after Bernardini 1985). zinc powder or zinc chloride) are used, the reaction temperature can be reduced to -220°C. Neutralization by re-esterification is not allowed in most countries for edible oils and fats. It is applied only for technical purposes. The extent to which this process is economical depends on the price of the oil. Bernardini (1985) quoted 205 U.S. $/MT as the cost for re-esterification. Depending on the cost of crude oil, this may be very close to the price for technical oils. 7.2.2.2 Neutralization with Alkali. Today, the most common method for neutralization of fats and oils is neutralization with caustic soda solution. In the course of the reaction, soaps and water are formed from the free fatty acids as follows:
R-COOH + NaOH + R-COONa + H,O
[7.21
Fats and Oils Handbook
61 8
At normal pressure, this reaction proceeds completely from the left to the right at temperatures of 6045°C. The soaps formed could be split working from the right to the left at a pressure >30 bar. Soap splitting with mineral acids (see Chapter 7.2.7) is more common. Neutralization can be done batchwise, semicontinuously or continuously. In all cases, the heated oil is brought into contact with the caustic soda solution. The aqueous soap solution is separated, and the oil is washed and dried. Pardun (1979) reported on neutralization trials with ammonia. The process, however, did not succeed in practise. The amount of alkali lye that is necessary for neutralization-almost exclusively caustic soda solution-is determined by titration of the oil immediately before neutralization. This is usually not done in the laboratory but on the factory floor. From the titration result, plant operators can read the required amount of caustic soda from tables. Depending on the lye strength (often in Baume units, abbr. Be), an excess of 5-25% is applied to ensure complete neutralization (Fig. 7.5). In the US., some old plants still exist in which the oil is neutralized at 20-30°C (cold neutralization). However, this process is disappearing gradually. Because of the different composition of fats from fatty acids of different molecular weight, the amount of caustic soda required for neutralization is also different (Table 7.1). The amount L (in liters) of N-normal lye solution needed to neutralize 1 MT of oil can be calculated as follows: 0d . FFA , l o ,000 L = d . FFA ~ 1 0 0 0 ~ 1 0 0100.M . N M,N
P.31
If the amount C (kg) of caustic soda, NaOH, has to be calculated, 40 N has to be added in the numerator and 1000 in the denominator, resulting in the following: 0~ N d , FFA ,400 C = d , FFA. 1 0 0 0 ~ 1 0 0 40. 100, M . N ,1000 M
V.41
CNde 011 60-85'C, in batch or via plate heat exchanger Saponification of fatty acids Soap decantation or centrifugation
+
>>>Aqueous soaD solution >>> I
Soap decantation or centrifugation
Washing Soap free
1
+
>>>Aqueous soap solution >>w
+ I
I
' i Dlyw
Neutralized oil
2040 hPa
Soap splming
1:
Separation
1
-I
t
-TI++ x.> heavihl diluted Fatty acids
aqueous soiution of NaJSO,
Fig. 7.5. Processing flow chart of neutralization with alkali lye.
Oil Purification
61 9
TABLE 7.1 Factors Influencing the A m o u n t of Lye Needed for Neutralization Influencing factor Proportion of free fatty acids before neutralization Specific density of the oil Average molecular weight of the oil's fatty acids Lye strength
influence
+ + -
+ = proportional; - = inversely proportional
In this formula, an average molecular weight is used for practical purposes. Because of the different average molecular weights of different oils and fats and their different specific densities (see Chapter 2.3.2.3), which enter the formula via the percentage of FFA, different amounts of caustic soda are calculated for the neutralization of different fats (Table 7.2). Baumt is an old measure for density (0' BaumC is equivalent to the density of a 10% solution of sodium chloride and 60" B t corresponds to a density of 0.745; see also Fig. 7.6). It can be seen that the amounts of lye needed to neutralize the common vegetable oils are all of the same order of magnitude and that only palm fats (laurics) and rape oil with high erucic acid content (not common any more) differ substantially. Thus it becomes possible to cover the whole spectrum with two lump numbers. To ensure complete neutralization, an excess of lye has to be used. Table 7.3 shows the factors influencing this excess. Application of excess lye is limited because some effects are positive but can easily become negative. For example, intense contact of the lye with the oil is positive on the one hand to keep the excess of lye small; on the other hand, the danger of emulsion formation rises with increased stirring speed. Because emulsions are difficult to break and cause trouble TABLE 7.2 A m o u n t of Lye Necessary for Neutralization of Different O i l s a n d Fats
Oilfat Lard Tallow Palm oil Soybean oil Cottonseed oil Sunflower seed oil Peanut oil Rapeseed oil (LEAR) (HEAR) Coconut oil Palm kernel oil
Amount of lye needed per % of FFA to neutralize one MT of oil with caustic soda
Density at 15%C (g/cm3)
Average molecular weight
(kg NaOH)
(L 4n-NaOH)
(L NaOH, 14 Be)
0.920 0.945 0.935 0.928 0.925 0.923 0.91 8 0.915 0.913 0.923 0.930
2 73 2 70 2 70 280 2 75 280 2 78 2 85 308 215 225
1.35 1.40 1.39 1.33 1.35 1.32 1.32 1.28 1.19 1.72 1.65
8.4 8.8 8.7 8.3 8.4 8.2 8.3 8.0 7.4 10.7 10.3
12.3 12.7 12.6 12.1 12.3 12.0 12.0 11.6 10.8 15.6 15.0
Fats and Oils Handbook
620
Amount of lye needed for neutralization [%I
Lye strength [W
I
lo
30 27 24 21 I8
16 12
9 8 3
0
1 1
2
3
4
5
Oil’s FFA [%I
0 1
1
2
3
4
5
8
Lye normality
Fig. 7.6. Amount of caustic soda needed for neutralization (after Brimberg 1981).
in production, it is more efficient in the end to increase the amount of lye. Less excess lye is needed for unsaturated fatty acids because the soaps from unsaturated fatty acids are liquid and do not entrain lye (Rudischer 1959). After soap separation, the oil is washed with water until soap free and dried under vacuum. Neutralization is then followed by (interesterification, if needed) bleaching and deodorization. In the old days, it was also quite common to neutralize oil using unslaked lime instead of caustic soda. It is considered fraudulent to add unslaked lime to crude oils with an FFA above the specification in order to reduce the FFA content, thus bringing it back within the limits of the specification. In addition, this process harms the client who receives the oil because sludge sediments, which TABLE 7.3 Several Factors Influencing the Excess of Lye Needed in Alkali Neutralization ~
Factor Free fatty acids (FFA) after neutralization Neutralization temperature Share of short-chain FFA Share of unsaturated FA Proportion of gums Portion of FFA (i.e., FFA < 1%) Intensity of contact between oil and lye (distribution) Color (brightness as an indication for impurities) Lye strength
+ proportional; - inversely proportional.
Influence
Oil Purification
62 1
are difficult to remove, are deposited in oil storage tanks. If oils are difficult to refine with common neutralization techniques, a soda water glass boiling step can be included. The silicates that precipitate bind undesired particles. S o d a water glass boiling is conducted at temperatures of 1W105"C and takes -15-30 min. The approximate amounts of energy required for common neutralization processes per ton of oil are as follows: discontinuous process, 150 kg steam and 4 kwh electrical energy; centrifugal process, 85 kg steam and 13 kwh electrical energy.
7.2.2.2.7 Discontinuous neutralization. A neutralizer for discontinuous neutralization is a vertical cylindrical vessel of up to 75-ton content; it is conical in its lower part. It is equipped with an outer heating mantle and an inner heating coil to ensure proper heating. Also, there is a stirrer for good agitation and some shower heads to dose finely dispersed caustic soda solution onto the oil. In the lower part, there is a view glass. Figure 7.7 shows a neutralizer with heating mantle, stirrer, inlet for steam and outlet for the condensate. After being heated to -6o"C, the lye is finely sprayed onto the oil. It is then heated to 70430°C. Because of its higher specific weight, the caustic soda solution percolates through the oil, thereby neutralizing the FFA on its way. Stirring supports this process. The aqueous soap solution collects in the lower cone and is decanted. The completeness of soap separa-
Fats and Oils Handbook
622
tion is optically controlled using the view glass (manually) or by ultrasonic or conductivity measurements (automatically). The soap is collected and the oil is washed soap free. Then the oil is dried in the neutralization vessel. Discontinuous neutralization has advantages if small batches of different oils have to be neutralized or if the daily throughput does not exceed 10 MT. The investment for such a plant is low. On the other hand, it cannot be automated easily, thus incurring higher labor costs. This makes discontinuous neutralization of particular interest for countries with low wages even for higher throughput. In addition, such plants can be manufactured and maintained locally, which is very important in countries with high import duties or with no reserves of foreign currency. Compared with these advantages, in special situations, the high energy costs usually do not matter. Cycle times of a batch neutralizer are given in Figure 7.8.
7.2.2.2.2 Semicontinuous neutralization. If neutralization in batch vessels (discontinuous) is combined with soap separation via centrifuges (see Chapter 5.2.5.3), a semicontinuous process is born. If the centrifuge is sufficiently large, several neutralizers can feed one machine. Because no settling time is needed for the soap cycle, times can be reduced. To break the emulsion, an electrolyte must sometimes be added. The Zenith process is another semicontinuous process that is not common in Europe (Bergmann and Johnsson 1964, Cavanagh 1990, Hoffmann 1973 and 1974). In this process, the degummed oil is fed dropwise from the bottom to a vertical cylindrical vessel that is filled with weak lye. The oil percolates through the lye (from the bottom to the top) and is neutralized along its way. It then drains off on top. The entire Zenith process includes semicontinuous degumming and bleaching with the described neutralization step in between the two ( B r h 1976). 7.2.2.2.3 Continuous neutralization. Using centrifuges for separation, a fully continuous neutralization plant can be designed. These plants require a high Crude oil Batch filling
30 rnin
I
I
t
Cooking @
20min
I
10 min
60 rnin
30 rnin
Soap separation I
I
I Neutralized oil
10 rnin
225 rnin (e255 rnin)
@ for soda waterglau cooking
Fig. 7.8. Cycle times for batch neutralization
Oil Purification
62 3
investment but can be run at very low cost. Plants of this type were fxst erected in 1948 by Alfa Laval, although the idea as such was already quite old (Hefter 1906). The processing steps given in Figure 7.5 are not actually performed in the same vessel one step after the other as described in Chapter 7.2.2.2.1, but in specialized equipment that is subsequently passed through. A processing flow chart is given in Figure 7.9, w h l e Figure 7.10 shows continuous neutralization plants for both the short and the long mix process. The plant is fed from a storage tank.The oil passes through an oil meter and a plate heat exchanger where it is indirectly heated to the reaction temperature of 80-9O0C. From there, it is pumped into a mixer where it is dosed with an amount of caustic soda equivalent to the acid value of the oil. This dosing step is coupled with the oil meter to ensure the addition of the correct amount of lye. Then the oillsoap mixture is pumped into a reaction vessel and a second mixer from which it passes through a self-discharging separator. Less than 15 s after addition of the caustic soda the soap is already separated by centrifugation. The bowl rotates at 400-5000 rotations/min and the soap solution is continuously discharged. If needed, water can be added to the bowl to improve soap separation.
Oleometer
Metenng oil
1
optional
<-z< Caustic soda solution
/[
Tfl& contmkd by oleometer)
/
I
1
Separation
Centrifuges, 400C-50W min I
I!
>>>Aqueous soao solution
-9
=.
Soap splitting
1
1
7 c t
e i Wing
>>> Aaueous saao solution
Soap splitting
Vacuum dryer (-20 hPs), thin oil film
Neutralized oil
Fig. 7.9. Flow chart of continuous neutralization with separation centrifuges.
624
fats and Oils Handbook
Fig. 7.10. Continuous neutralization plants for the long-mix (above) and short-mix (below) processes (courtesy of Alfa Lava1 AB, Tumba).
Bad quality oils may require a second treatment (rerefining), following the same principle as the first process. The plate heat exchanger for the second stage is much smaller because the oil leaving the first separator is at a sufficiently high temperature so as to require only postheating. The oil is then heated to washing temperature in a plate heat exchanger and washed with hot water (-10% of the amount of oil). The washing water is also separated by a centrifuge. After separation of the washing water, the oil is dried. It is subsequently fed into a vacuum dryer where it flows in a thin film under reduced pressure (-25 hPa) over a series of cascades. The water easily evaporates from that thin film, and the oil is collected at the bottom of the vessel to be pumped into the neutral oil storage. The soaps are also collected and are worked up or sold as such.
Oil Purification
62 5
Such plants are designed for a capacity of up to 300 todd of crude oil. In modem installations, the plant can be cleaned in place (CIP), which allows for continuous operation for several months without external interference. In addition to the above-mentioned short mix process, which is applied mainly in Europe, there is a long mix process that is preferred in the U.S. This process differs in that the caustic soda is added to the oil at ambient temperature and the mixture is heated to 70-80°C after a long reaction time of 5-15 min. The separation temperatures in the long mix process are between 55 and 90°C (Hendrix 1990). Figure 7.11 shows a model of the neutralization plant with separation centrifuges. Haraldsson (1983) compared the results of refining soybean oil (0.4% FFA, 0.5% nonhydrated phosphatides) for both processes (Table 7.4). 7.2.2.4 The lntegration of Degurnrning. Before the continuous neutralization described above, a degumming step can be carried out (see also Chapter 7.1). To do so, the amount of acid required (typically 75% phosphoric acid) is added to the oil. The acid supports the hydration of phospholipids followed by their precipita-
Fig. 7.11. Model of a plant for continuous neutralization (courtesy of Westfalia Separator AG, Oelde).
Fats and Oils Handbook
626
TABLE 7.4 Results of Soybean O i l Refining Using the Short (s) and the Long (I) M i x Process, W i t h (+) or Without (-) Prior Phosphoric Acid TreatrnenWb ~~
~
Process
Mixing time (5)
Mixing temperature ("C)
Washing water (L)
P (pprn)
90 1 x10 72 -20 1 x10 4 S+ 5 90 1 x10 6 s+r 5 90 2x4 1 Soybean oil: 0.4% FFA, 0Soh nonhydrated phosphatides. Caustic soda 4n, 25% excess; soap analysis according to AOCS method.
S-
I-
5 240
Resulting in Ca (ppm)
Soap (ppm)
a4 2 6 <1
90 50 70
10
ar indicates rerefining.
bource: Haraldson (1 983)
tion from the oil. The excess acid is also neutralized in the subsequent neutralization step. The gums are removed together with the soaps in the separator. If oils with a very high amount of gums are processed, there is the danger that the centrifuge will be blocked and that the soap can no longer be removed adequately. Self- discharging separators may solve this problem. 7.2.2.2.5 The integration of dewaxing. Some oils with an excessive wax content have to be dewaxed (see Chapter 6.3). These are predominantly sunflower, corn and rice bran oil. It is possible to integrate the dewaxing step into a degumming and neutralization plant. Before the washing step, the oil is thus precooled in a plate heat exchanger countercurrently to the incoming crude oil and finally cooled in a vessel for 4-6 h to a temperature of 6 8 ° C . Then water of 4 8 ° C is added and the system is slowly heated to 16-18°C. A water/wax mixture is formed, which is removed together with the washing water. This washing step is repeated. This process requires little additional equipment and is thus very inexpensive compared with dedicated dewaxing plants. Figure 7.12 shows the flow chart of a complete plant, integrating the degumming and the dewaxing steps. 7.2.3 Miscella Refining
zf refining is located in connection with an oil mill, refining of the miscella is possible. To follow this process, the extraction miscella is concentrated to 6 5 8 % oil content (Cavanagh 1976). Caustic soda (7-26 Be) is added to the miscella to hydrate the phosphatides, and the mixture is run over a homogenizer for 15 s. The shear stress generated by milk homogenizers is sufficiently high to ensure the desired effect. The refined miscella is separated via centrifuges and run via a filter, which usually consists of a bleaching earth bed (Fig. 7.13). The miscella can be worked up (see Chapter 5.2.4.l), or further processing steps such as winterization or hydrogenation may follow. Instead of homogenization, intense mixing is also possible; then, however, processing aids have to be added to promote the hydration of the phosphatides.
Oil Purification
62 7
Crude oil
Degurnming
1
Plate heat exdanger
- t +
+
+
1 Heating up
Rerefining
1 1 Dewaxing
&
Piate heat exchanger
t
&a s d m n (-20%)-
<<<-CL !$C
4-
~
I
+
>>> aauwus solution of SOWS
Oil
+ - - * 1
1 44%
t
t
I
I
I
Senling
H h cc<
t
4.8% Water c
t
I'
I
,
c
c
c
1,
___.-
Hesting up
-
1t
I Washing
>>> WaShiM WStW (* SO%)
t
<<<water > <
+--]I
Heating u p
~
I
'L
2 Washing
17. >>z Washlna water (very low in SOED~
_-+_
Oil, degummed. neutralized
Fig. 7.12. Processing flow chart of degumming, refining, dewaxing and rerefining vla centrifuges.
7.2.4 Other Processes
Many other processes have been tested but failed to succeed in the end. For example, Bengen and Schlenk (1940) patented a process using urea, which forms adducts with the fatty acids. Rigamonti and Riccio (1952 and 1953) developed the process further, but the results achieved were not good enough for upscaling. Bhattacharya et al. (1989) proposed a technique for enzymatic neutralization. They demonstrated in detail that the stoichiometric addition of glycerol yielded the best results. With the enzyme, the use of a temperature of 70°C and 10% enzyme addi-
Fats and Oils Handbook
62 8
FUtnUon
Refined rnimtk
F l b r eid (0.g. b*.cMng wfthr) ( F u m pmcedng ma 5.2.4.1)
Fig. 7.1 3. Processing flow chart of miscelI a refin ing .
tion were optimal. There is still a long way to go for such a process to be upscaled because usually oils are also hydrolyzed by the enzyme.
7.2.5 Soap Splitting Soap is usually split with sulfuric acid as follows:
2 R-COONa + H2S04+ 2 R-COOH + Na2S04
V.51
In conventional plants, soap splitting is done batchwise. The soap is then separated by decantation. The separation line is detected visually with a view glass installed in the conical lower part of the vessel. The refining fatty acids or soap stock fatty acids also contain the neutral oil that was entrained during soap formation as well as some impurities. The soap stock fatty acid has to be refined. The losses, which consist of entrained non-fatty acid substances, usually oils and fats, form the refining loss and are calculated in the refining factor. This factor determines the ratio (wt/wt) of the refining fatty acids compared with fatty acids present in the crude oils before neutralization. An ideal neutralization process, which removes only the fatty acids, has a factor of 1.0. A factor of 1.7, for example, means that components that were unintentionally removed from the oil together with the fatty acids account for 70% of the fatty acid weight in the nonneutralized oil. At present, continuous soap splitting is applied. In such plants, sulfuric acid is continuously dosed into the soap stream. The dependency on the pH-value follows the usual rules of neutralization with acids. That means that low amounts of acids or lye close to the equivalence point cause a large pH shift, whereas in the regions of high or low pH higher amounts of acid or lye are necessary. Figure 7.14 shows that the titration curves for soap splitting are very steep between pH 3 and pH 5. Small amounts of acid result in a large pH change. For good results, a pH of 3 is
Oil Purification
62 9
required in soap splitting. After the mixture of soap and sulfuric acid has passed through the reaction chamber, conductivity is measured to decide whether free acid is present. The dosage of sulfuric acid is controlled such that no free acid occurs. Currently, FFA can also be separated from the water via centrifugation mainly because materials have been developed that can stand the aggressive fatty acids and the sulfuric acid (pH 2 to 3) at temperatures of 80- 90°C. 7.2.6 The Principle of Centrifugal Separation
Separation via centrifuges occurs not only in refining but also in oil extraction (see Chapter 3). It enables high throughputs in continuous operation. Separators are also called centrifuges; if they also allow the separation of large amounts of solids, they are called decanters. Diipjohann and Hemfort (1975) have compiled the principles in an article. Brunner (1984) reported new developments. An excellent paper on centrifugation was published by Hemfort as a brochure of Westfalia Separator AG (1984). 7.2.6.7 The Theory of Centrifugal Separation. A separator consists of a set of disks that are stacked and adjusted at an angle cp toward the horizontal axis. The set of disks rotates in a bowl with an angular velocity o around the separator axis. The liquid fed to the separator either contains solids or it consists of two liquids that are insoluble in each other. The liquid is fed via (3) (Fig. 7.15). As a result of their higher density, the solids are driven toward the inner wall of the bowl shell where they collect in the sediment holding space (11). From there, the solids are ejected
'1
-
--- ---_
-,
7
............
11.9%
TFM
Fats and Oils Handbook
630
17
15
" I
14
'I
1
\
\
l6
l3
Fig. 7.1 5 . Drawing of a centrifuge (courtesy of Westfalia Separator AG, Oelde).
(12) via the sediment ejection ports (13), once the sliding piston (12) opens. The heavy liquid phase leaves the separator via (2), the lighter, via (4). They are separated by the centripetal pump (7). Water flushing is possible via (5). Other details include disks (2), rotometer (6) and annular piston (17). The liquid feed is evenly distributed over all separating spaces between the disks. It is thus split into many thin layers that pass through these spaces. To enable this separation, the disks have rising channels (Fig. 7.17), which are vertical passages through the whole set of disks, formed by holes in the disks that are positioned one above the other. In a separator with, for example, z disks, the quantity passing one separating space is Q/z (where Q is the hourly flow of feed stock; Fig. 7.16). The solid particles being introduced with the liquid at E are carried with the liquid phase at a separation velocity v, in the direction of the arrow. They are forced to the outside, in this case the upper disc U with a radial velocity vr, which is also the sedimentation velocity. The solid particles then have the vector velocity vv, resulting from the sum of v, and v,. They are considered to have been removed from the liquid once they have reached the upper conical surface of the individual separating space. They then slide down in a cohesive layer to the bowl's sludge space, because, having reached the wall, the force 1 becomes negligible so that they follow vr The liquid flows with a separation velocity vs in the direction of the arrow, exiting through the center of the bowl. To describe the separation mechanism in a centrifuge, many authors have developed equations (see, e.g., Cowan 1976 and Hemfort 1960 and 1984). Particles
63 1
Oil Purification
F,=rn.b
[7.6a]
F c = r n . w2 . r
[7.6b]
where rn is the mass of the particle, b is the acceleration (in the case of gravity, b = g = 9.8 m/s*), o is the angular velocity, and r is the radial distance (radius of the Disk set with rising channels near the periphery
Disk set with rising channels near the center
Disk set with central rising channels
Fig. 7.17. Position of rising channels in a set of separator disks (redrawn; courtesy of Westfalia Separator AC, Oelde)
632
Fats and Oils Handbook
centrifuge). For immiscible liquids or solid particles in a liquid, the driving force for separation is the difference of the forces applied to either the two liquids or the solid particles and the liquid. This force differs depending on the mass of the liquids and/or the solids. The mass m from Equation [7.6b] then becomes the mass difference.
F , = (mliquid - msolid) . 02 . r or F, = (Am) . 02 . r
P.71
Assuming spherical particles, their mass may be replaced by the product of volume times density and Am may become the difference in density Ap. The volume of a spherical particle is characterized by its diameter (D). Am=--- A P
6 nD3
~7.81
By substituting Equation [7.8] in [7.7],
According to Stoke’s law, exposed to the force Fs, a particle is sedimenting with the sedimentation speed V, (Equation L7.101). This force works opposite to F,:
If Fs and F, are equal, the following result is obtained: [7.11] The sedimentation speed thus becomes:
[7.11a] If the centrifugal acceleration is replaced by gravity, the speed of sedimentation without additional forces is obtained as:
v, = D2 .p2. g
[7.1Ib]
18.77
The sedimentation distance n of a particle (the product of the speed V, and residence time in the bowl) can be calculated when time is expressed as the quotient of the volume V of the liquid and its flow rate Q.
[7.12]
Oil Purification
633
If n is set to s/2, thus assuming that half of the particles with the diameter D are sedimenting during the residence time, Equation [7.12] becomes Q=- D
~ . A PV . 0 2 . r
9.v
[7.13]
S
If the volume V is substituted by a function of the radius and machine specific parameters are brought in, Equation [7.14] is obtained after allowing for some simplifications: [7.14] In this equation, the first part means Stoke's sedimentation speed, the second the equivalent clarification area of the bowl, where q is the dynamic viscosity, D is the particle diameter, g is the acceleration due to gravity, Ap is the density difference and z is the number of disks; see Figure 7.16 for x,rl and r2. Hemfort further developed Equation [7.14] by reintroducing the acceleration due to gravity and the clarification area A (effective rotor area):
[7.14a] Defining 6 = r . w2/g as the centrifugation or acceleration factor, and substituting the first part of the equation by VStokes, Equation [7.14a] becomes
Q = VStokes 6 ' A '
[7.14b]
where VStokesis Stoke's sedimentation speed, 4 is the centrifugation factor, A is the clarification area, and 6 . A is the equivalent clarification factor. The number of disks (z), the angular velocity 0,and the angle x as well as rl, r2 can be influenced by the construction of the centrifuge, whereas q, A, and Ap are dependent on the products to be separated. Within the limits set by the substances to be separated and the technical restrictions for construction, these parameters influence the throughput as shown in Table 7.5. Factors relating to the product may sometimes also be changed, thereby improving centrifugal separation. If, for example, solids have to be removed from oil, the density difference may be increased by a water treatment. If the solids are able to soak, the density difference is usually increased. The viscosity and density of the oil can be reduced by heating it up; because lowering the viscosity of the carrier liquid increases efficiency, this will help. Dilution with a solvent also helps, but is not done because the solvent has to be removed later. Increasing the particle diameter also has
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TABLE 7.5 Influence of Different Parameters on the Throughput of Centrifuges ~~
~~
Dependency on influencing factor Influencing factor
Single
Square
Cubic
+
Particle diameter D Density difference Ap Viscosity q Angular velocity w Tilt angle of disk (tan cp) Number of disks z Effective radii r, and r,
+ t
+ + + ~~
~
+ proportional; - inversely proportional
positive effects. Addition of flocculates or agglomeration of the particles improves the performance. Adjustment of the pH helps with proteins to reach their isoelectric point. In centrifugation of products of Lanza fractionation (see Chapter 6.2.2.2),the addition of surface active detergents and electrolytes helps to reduce surface tension and to avoid electrical charging of fine floating substances. Both measures, initially done for other reasons, help to improve separation. Enlarging design factors can also improve centrifugal separation. Increasing the bowl speed would help. However, there is a limit dictated by the permissible stress. Hemforth (1960) mentioned a 00,2 limit 5 500 N/mm2. Only very few materials fulfill this criterion. The bowl diameter and with it (r13- r23) are determined by the required sediment-holding capacity of the bowl. The tilt angle of the disks, cp, is limited by the slope of the separated solids. It must be smaller than the slope angle. The number of disks in the stack is limited by the bowl as a housing. All factors together must fulfill the equilibrium or better the optimal compromise between the best technical solution and commercial viability. After having separated a solid phase, the remaining two liquids (in our case oil and water) may subsequently be separated. The position of the rising channels is determined by the density difference of the two liquids. The rising channels must always lie within the separating zone. The clarification area determines the separation sharpness. For the system watedoil, this means that in case A (rising channels near the periphery), the larger separation area is on the side of the lighter component, i.e., on the oil side. Consequently, almost complete water separation can be ,achieved. If the larger area is on the side of the heavier (denser) component, water (central rising channels), oil-free water can be obtained. The component with the larger separation area is always more cleanly separated. Equal separation areas yield products without preference for one of the components. The setting of the rising channels cannot be changed if separators are used for different separation work. The exit diameter of the heavier phase is adjusted by a regulating ring such that the separation line is in the area of the rising channels.
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7.2.6.2Separators. Separators are used in the fats and oils industry to achieve the following: (i) separate liquids, for example, soap from oil after neutralization, water from oil after melting emulsion fats or skimming of milk; (ii) to separate small amounts of solids, for example, polishing of palm and olive oil or polishing of fish oil. If the task is to separate very small amounts of solids (Solids = S < 0.1% wdwt), discontinuous small separators are the choice. The solids are then collected on the inner wall of the bowl after being separated from the liquid and after centrifugation. If the sediment holding space is filled, the separator must be opened and the solids removed. Compared with self-discharging centrifuges, the advantages include a simpler construction combined with lower investment costs as well as much lower complexity and handling. The disadvantages are that more handling is needed and the process is run discontinuously. If the amount of solids is higher (0.1%< S < 20%), separators with self-discharging bowls are used. If the solids holding space is filled, the desludging mechanism starts. A piston opens and the solids are removed through the solids’ ejection port by the centrifugal forces of the rotating disks. Opening of the piston is done while working at full rotation speed. For polishing of pulp oils (palm and olive oil), separators with liquid discharge are used. Residual water can easily be removed in this manner. Tables 7.6 through 7.8 give some indication of the technical data for centrifugal separators for different applications and with different capacities. For the extraction of oils and fats in the fat industry, separators that enable the separation of the solids as well as the separation of oil and water phase in one go are usually used. In this application, the solids content is much higher than for polishing (Fig. 7.18) and thus other types must be used (Fig. 7.19). Centrifuges that are usually used for the extraction of slaughter fats have dimensions and capacities shown in Table 7.6. In addition to oil extraction and polishing of oils, separators are also used for refining (see Chapter 7.2) and for degumming (see Chapter 7.1). Special separators that have a capacity of up to 25 ton/h and are suitable for CIP are built for these purposes. Small amounts of solids are collected in the sediment holding TABLE 7.6 Capacities of Edible Oil Refining Centrifuges in Different Processesa Capacity (ton/d) for sepatator type Process Water degurnrning Acid degurnrning Neutralization (FFAc3%) Washing Winterization Cold refining Miscella refining (50% oil) aSource: Westfalia Separator AC, Oelde
RTA40
RTA60
RTA 140
75 75 75 100 50 50 60
150 120 150 150 60 60 100
240 240 240 42 0 150 150 200
RSE 100 RSE2OO
300 300 300 300 150 150 200
600 600 600 600 300 300 300
RSE250 1000 800 1000 1000 420 420 360
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63 6
TABLE 7.7 Technical Data of Refining-Separatorsa ~~
~~
Type
RSA40
- 10,000
Rated capacity Bowl content Solids space Bowl speed, max. Motor Length Height Weight
20 5 6540 15 1645 1730 1420
RSA60
RSE 100
RSE2OO
RSE250
-1 5,000 20 5 6500 15 1645 1730 1430
-25,000 60 15 4050 30
-35,000 60 15 4550 37
-,60,000
2050
2050
2110
2350 1920
2350 2280
2080 3200
60 15 4800 60
aSource: Westfalia Separator.
space and are periodically discharged. The aqueous soap solution and the oil are separated under pressure with the aid of regulating rings (Table 7.7). 7.2.6.3 Decanters. If the solids content is >20%, decanters are used instead of the separators described above. They allow the separation of suspensions with a solids content 260%.In principle, they are solids-oriented separators. They are used mainly to separate fish oil from stick water and solids (see Chapter 3) and slaughter fats from greaves and water (see Chapter 3). As indicated earlier in the case of separators, the feed of the decanter and the discharge of liquid and solid are continuous. In addition, it is possible to split a liquid into a lighter and a heavier phase (3-phase decanter). In principle, a decanter is a horizontally fixed centrifuge. The separated solids are transported by a screw to the outlet (Fig. 7.20). Clarification of the feed liquid is performed in a separation zone where the solids (dark shaded) are separated on the bowl wall after they have been centrifuged. The liquid (light shaded) leaves the decanter in the right part, and the solids are conveyed off by a scroll, which is rotating slightly faster or slower than the bowl shell. That part of the bowl in which liquid is no longer found is called the drying zone. The separation line can be adjusted by means of regulating rings, comparable to those in separators. The drying zone is also called the “beach TABLE 7.8 Technical Data of Decanters (Type CA)a Maximum throughput
(Uh)
Bowl diameter Bowl speed, max. Energy requ. drive Length Width Height Weight (without drive)
(mm) (min-1) (kWh) (mm) (mm) (mm) (kg)
Westfalia Separator AC.
10,000
25,000
65,000
90,000
220 4500 11 1925 1180 600 700
354 4000 22-30 2275 1520 895 1680
650 2950 45-1 10 3 700 2645 1400 7500
650 2950 75-1 10 4300 2645 1400 8500
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1 Feed 2 Discharge 3 Turbidity meter 4 Disks 5 Sediment holding space 6 Sediment discharge 7 Operating-water valve 8 Drain hole 9 Opening chamber 10 Closing chamber 11 Annular piston 12 Timing unit 13 Discharge pump
Fig. 7.18. Clarifier (courtesy of Westfalia Separator AG, Oelde).
zone,” and the separating zone the “pool zone.” Decanter types with flat and steep angles can be distinguished (Fig. 7.21). Flat cone decanters have a larger drying zone ensuring a higher drying rate. In contrast, the polishing rate is higher for steep cone decanters. The slope of the scroll is determined by the kind of solids to be removedthe smaller the slope, the less the danger of stirring up sedimented solids. The same holds true for too high a differential speed between the scroll and the bowl shell. This difference is usually on the order of 20-80 rotations/min, depending on the product (-30/min for the preclarification of slaughter fats). Clarification decanters that polish only liquids have a throughput of up to 90,000 L/h (Table 7.8).
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1 Feed, product 2 Fine tuner 3 Vapor seal 4 Hydrohermetic feed 5 Special disk S
W
6 Hydraulic ejection mechanism 7 Noise reduction 8 Gabtight frame 9 Three phase AC motor 10 Discharge, heavy phase product 11 Bowl flush 12 Discharge, light phase product
Fig. 7.19. Refining separator type RSE (courtesy of Westfalia Separator AG, Oeide).
7.3 Bleaching Oils and fats are bleached to remove undesired colorants in part because these colorants would negatively influence the taste of the oil and in part because the color would disturb the consumer. Therefore, on the whole, these colorants limit use and marketability. In addition, some of the p d c l e s that are removed during bleaching promote deteriora-
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Fig. 7.20. Decanter (courtesy of Westfalia Separator AC, Oelde).
Fig. 7.21. Schematic drawing of separator and clarifier bowls and of flat and steep angle decanters (courtesy of Westfalia Separator AC, Oelde).
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tion of the oil mainly via their prooxidative properties. During bleachmg, the oil is brought into contact with a surface-active substance that adsorbs the undesired particles. The adsorbent and the adsorbed particles are filtered off, and the oil leaves the plant with the desired color. With the naked eye, the success of bleaching can be checked only via the color of the oil. This color is often measured to evaluate the success of bleaching (for example, Lovibond color, see Chapter 9.8). For more detailed investigations, the extinction of light of certain wavelengths is used. Rudischer (1959) described the course of bleaching, dependent on different parameters (Fig. 7.22). 7.3.1 The Theory of Bleaching
The colored particles (or substances) that should be removed during bleaching are present in the oil either dissolved or in a colloidal form. In addition to being a physical process, i.e., adsorption, bleaching is also a chemical process by the interaction of the colorants and the chemically active centers of the bleaching earths. In both cases, the process is conducted on the surface of the bleaching agent. In no case is the bleaching used for edible oils and fats similar to the usual bleaching with chemicals (for instance hypochlorite). The colored particles are bound only adsorptively (chemisorption or physical adsorption) and are removed by filtration together with the bleaching agent. This mechanism is also supported by the fact that the colorants can easily be removed from the bleaching earth if they do not partly decompose (observed with chlorophyll and carotenes). Mathematically, the bleaching process follows the Freundlich adsorp tion isotherm, which is an extension of the Langmuir equation. These equations are
Bleaching
................
A: time [min]
.....
B: temperature PC] C: earth p! ]..................
0
40 20 0.4
80
40 0.8
120 60 1.2
160 80 1.6
200 100 2.0
Fig. 7.22. Bleaching effect of an oil dependent on different processing parameters (after Rudischer 1959).
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64 1
valid for constant temperature and describe the dependency of the adsorbed amount of a substance ( k ) on its residual amount (c) in the solvent (in this case in the oil).
-=+)
b
k
[7.15]
k0
In simplified form, k, = a .c,b
[7.15a]
or, log k, = log a + log b log cr where the indices 0 and 1 indicate initial and relative amount, respectively, k , is the ratio of the adsorbed components, c is the amount of nonadsorbed component, and b are system-specific constants. If Equation [7.15] is plotted logarithmically, a straight line with slope b is obtained. However, in reality, the isotherms of Freundlich (1930) and Langmuir describe only the beginning of the adsorption process satisfactorily. If an amount rn of adsorbent (bleaching agent) is included, Equation [7.16] results: k = rn or
,
a . cb
[7.16]
log k - log rn = log a + b . log c
[7.16a]
If these bleaching trials are conducted with different bleaching earths, a is a measure of the (relative) amount of bleaching earth that has to be used to achieve the same bleaching result. To keep the product of rn and a constant, at a = 0.25. for example, the amount of bleaching earth must be four times as-high as at a = 1.0. Different researchers have determined the system constants a and b for different bleaching agents and oils (see, for example, Bailey 1951). For all of these trials, a was between 0.1 and 7.6. The numbers found for b were between 0.33 and 4.0. The difference in these numbers is caused in part by different methods to determine the bleaching success. Brimberg (1981) described the bleaching process using a formula developed by Berg and Ohlsson (1982) on the basis of experiments of Alfa Laval. [7..17] c
log-=10gk+0.5
log t
[7.17]
CO
In this equation, c is the concentration of the pigments, i.e., the components to be removed at the time t (index 0 is the start); t is the time passed since the addition of the bleaching agent, and k is a system-specific constant. The equation has been tested for chlorophyll and carotene.
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7.3.1.1 The influence of Time. Brimberg (1982) published trials on the kinetics of bleaching. In the following, the influence of different process parameters on extinction values of the bleached oil is shown. The trials were conducted with rapeseed oil. The bleaching temperature was 80°C, and bleaching was performed with 1% bleaching earth, Tonsil Standard FF (Fig. 7.23). Both curves follow the findings indicated in Equation [7.17]. It can be seen that the negative slopes of the curves become flatter after a very steep decrease of the chlorophyll or carotene content; after 30 min, no further lightening can be achieved. The graph can be divided into three areas with very different slopes. According to recent theories, in the first phase, the stability of the colloid is broken when bleaching earth is added and the substances stabilizing the colloid are adsorbed. In the second phase, the colloidal particles form aggregates, which are also adsorbed; such particles could be made visible under a microscope. 7.3.1.2 The influence of the Amount of Bleaching Earth. According to Equation E7.161, apart from the dependency on time, there must also be a dependency on the amount of bleaching earth (Fig. 7.24). It can be shown that increasing the amount of bleaching earth improves the bleaching result for all bleaching times shown. However, these results, provided that a sufficient amount of bleaching earth is present, can also be achieved by increasing bleaching time. Here the commercial equilibrium balance between lower cycle times and higher cost for bleaching earth must be evaluated. 2.4
1% Bleaching earth, TONSIL Standard
2.0
5 E w
1.6
1.2
0.8
0
I
2 3 Bleaching time
4
[a, min]
5
6
Fig. 7.23. Bleaching result depending on the time (after Brimberg 1982).
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14
at 480nm (chlorophyll:
t 480nm (carotene)
2.0
2.0
-
Bleaching time [min]
1.5
1.5
1.o
1.o
0.5
Bleaching time [min] 1
0
2
3
0
0.5
2
1
Bleaching earth [% wtlwtof the oil]
Fig. 7.24.
Bleaching result depending on the amount of bleaching earth (after Brimberg 1981, Tollenaar and Hockmann 1964).
7.3.1.3 The lnfhence of Temperature. Bleaching temperatures are usually between 90 and 110°C (Fig. 7.25). Temperatures higher than 150°C must be avoided because changes in the structure of the fatty acids,may occur; isomerization reactions also might start. This does not hold true for the heat bleaching of palm oil (see Chapter 7.3.7).
-
Lovibond Color
ao
a
60
6
B
=40
4 8
%
2
20
0
0 0
20
40
60 80 100 I20 Bleaching temperature pC]
140
160
Fig. 7.25. Bleaching result depending on the temperature (after Bernardini 1985).
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7 . 3 . 7 . 4 The lnfluence of Humidity. The amount of water in the oils to be bleached must not be too high or the oil would be hydrolyzed, catalyzed by the bleaching earth. However, a certain amount of humidity is required to optimize the activity of the earth. Undried bleaching earth can contain up to 10% water. Figure 7.26 shows the dependency of the reaction constant k from Equation [7.17] on the water content based on data determined by Brimberg using rape oil. It becomes clear that the speed of reaction increases with increasing humidity. The water comes from the oil (-0.2%) and also from the earth.
7.3.2 The Bleaching Agent As noted above, bleaching with bleaching earth is not bleaching in the original sense of the word, that is, by destruction of the colored particles; rather, it is removal of the colorants by adsorption on an adsorbent with a large surface area such as bleaching earth. As bleaching agents, natural bleaching earths can be used such as diatomic earth or Fuller’s earth. In addition, activated or synthetic bleaching earths as well as active carbon may be used.
7.3.2.7 Natural Bleaching Earth. The best known natural bleaching earth is Fuller’s earth. The name comes from a former use in wool processing (scarring or fulling). Fuller’s earth is an aluminum hydrosilicate that can be used without activation. Its mineralogical properties were described in detail by Kerr (1932) and Nutting (1933). Diatomic earth is also suitable for bleaching. Nonactivated earths play only a minor role and are not described further.
Fig. 7.26. Velocity constant for rapeseed oil bleaching (after Brimberg 19811.
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7.3.2.2 Activated Bleaching Earth. Activated bleaching earths are of natural origin. They are different from the nonactivated in that they have enhanced properties caused by an acid treatment. Bleaching earth used in Europe is mainly montmorillonite, an aluminum hydrosilicate (Si02:A120,, -4: 1). The aluminum in this earth can be partly substituted by magnesium or by iron. Zschau (1985) and Mag (1990) described the structure of bleaching earths (Fig. 7.27).
OH OH
Water and exchangeable cations
4
1 0
H2O
1 ‘ 1 Fig. 7.27. Structure of Montmorillonite (redrawn; after Zschau 1985).
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The individual layers are negatively charged because Si atoms are partly replaced by A1 or Fe atoms. The A1 atoms may then be partly replaced by Mg atoms. Interlayer cations create the electrical charge, making that mineral a natural ion exchanger. To be used as bleaching earth, the earth must be pretreated. First, the raw mineral is cleansed of impurities. Second, the surface of the bleaching earth is increased by an acid treatment to enable better properties for the bleaching process. For this activation, the earth is suspended in water and treated with a mineral acid. The acid attacks the octahedral layer of the montmorillonite, thereby increasing surface area. From in between the layers, cations are released and replaced by protons, thus creating acidic exchange sites. In addition, a part of the metal ions from the layer structure is dissolved and the surface is thus increased. The acid is removed from the solid suspension via filter presses and the filter cake is washed almost acid free with water. Then the filter cake (water content -40%) is dried to a humidity of 6-10% and then ground. In this process, water that is chemically bound has to be retained in the earth, whereas water that is adsorptively bound has to be removed. During the drying process, particles smaller than 1 pm agglomerate to larger particles (Fig. 7 . 2 8 ) . A typical bleaching earth (Tonsil, Siidchemie AG, Miinchen) has the following approximate composition: 70% as Montmorillonit
(Aluminum hydrosilite)
U Blending Standardizing
Clays ofdifferent origin
HCI or HaSG (-30%). ca. 105'C
Washing
to acid level < 0.1% (calculated as HCI) Water content -40%
Burning
350400'C in gas current to 5 8 . 5 % humidity
I Airclarification I Actiiated bleaching earth
Fig. 7.28. Flow chart of bleaching earth production and activation and 30,OOOX rnicrophotograph of bleaching earth before (above) and after (below) activation (photos: courtesy of Sudchernie AG, Munchen).
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SiO,, 2% MgO, 15% A1,0,, 1% CaO, 4% Fe,O, and -7% calcination loss. By activation, the surface area of the bleaching earth can be increased from 10-20 to 200-300 mYg. 7.3.2.3 Synthetic Bleaching Earth. Natural bleaching earths have a given structure that can be changed only within certain limits. For example, activation can increase their surface area but the pore size and pore size distribution remain unchanged. For the bleaching process, an optimum pore size deviating only within narrow limits would be very advantageous. However, this can be achieved only if bleaching earths are synthesized. In addition, recycling of naturally activated bleaching earth for repetitive use is a problem because this process is very costly and the active surface decreases considerably. Disposal of bleaching earth becomes increasingly expensive; therefore, interest is rising in synthetic bleaching earth, which can be recycled. Such bleaching earths have been developed but with no real breakthrough as yet because either they are not very convincing in their properties or their application is commercially nonviable. However, it is obvious that in the near future synthetic bleaching earths that combine good bleaching properties with acceptable cost will be available. The synthetic bleaching agents that have continuously been developed further include TriSyl (Grace Davison) and SorbSyl (Crosfields). These are amorphous silica adsorbents with an average particle size of -19 Fm and are claimed to achieve a bleaching effect equivalent to that of clay at a much lower dosage; phospholipids are much better removed with silica than with clay. 7.3.2.4 Active Carbon. Active carbon is very rarely used alone as an adsorbent. In oils and fats that are very difficult to bleach, active carbon is used in combination with bleaching earth (carbon:earth, 1:9). Using this combination of adsorbents, polycyclic aromatic hydrocarbons (PAH) can almost completely be removed from the oil even if present in higher quantities. Many qualities of active carbon are available commercially. If used for edible oils, it is very important to check these qualities thoroughly to avoid the adsorbent itself containing aromatic hydrocarbons.
-
7.3.2.5 Silicates. Some manufacturers have launched amorphous silicates for which good bleaching properties are claimed. Such silicates have an average particle size of -20 p m and 99% of their dry matter consists of S O 2 . If blended with bleaching earth, it is claimed that they reduce the amount of bleaching earth needed to -50% of current needs. The other 50% can be replaced by 15-20% silicates. Up to now, there is an insufficient number of large-scale trials to determine if silicates are an alternative. 7.3.2.6 Comparing the Bleaching Agents. Natural bleaching earth can adsorb up to
15% of its own weight in colorants (Siddiqui and Hasnuddin 1968). It binds up to 30% of its own weight in oil. Because of its increased surface area, activated bleaching earth adsorbs 70-100% of its own weight. Using active carbon it can be up to 170%.
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Fats and Oils Handbook
As a result of the higher activity, activated bleaching earth can split soaps (ion exchanger effect), thus increasing the FFA. This is one of the reasons why the oil should be soapfree for bleaching. The other reason is that all bleaching agents adsorb soap, which can clog their surface and thus inactivate a considerable part of the earth. Above 150°C, there is a danger with all types of activated earth that isomerization of the fatty acids will occur (Patterson 1976). This temperature, however, is so far above the common processing temperatures that structural changes cannot occur provided processing is done properly. Table 7.9 gives properties of typical bleaching agents. 7.3.3 The Bleaching Process and Bleaching Plants
As for aLl processing steps in refining, discontinuous and continuous bleaching operations exist. There is a development toward continuous processing provided frequent changeovers can be avoided. Figure 7.29 shows the bleaching process schematically. The oil requires careful pretreatment (see Chapter 7.3.4) to achieve optimal results with a minimum of bleaching earth. It has to be taken into consideration that not only the earth itself is a cost factor, but also the loss of the oil that is bound to it. The amount of bleaching earths used is between 0.5 and 2.0% (wt/wt of the oil/fat) with a typical value of -1%. For the processing of oils of poor quality or high concentrations of environmental contaminants, active carbon can be added. The carbon then accounts for 10% of the total bleaching agent. If raw materials have been dried over an open fire (copra at times, see Chapter 4.3.6), the fat may contain fiveringed polycyclic components. These can be removed satisfactorily from the fat with the help of active carbon (0.4%; Biernoth and Rost 1968, see Chapter 7.5.7.). Bleaching earth flows easily; thus, it can be dosed under vacuum without difficulties. Plants also exist in which an ofileaching earth slurry is produced, which is then TABLE 7.9 Properties of Bleaching Agents, Typical Value9 Bleaching earth Property p H in aqueous suspension Bulk density (g/L) Surface area (rnVg) Particle size (pn) >80 (%) (Yo) 4C-80 20-40 (Yo) >20 (O/O) <10 (Yo) 1C-50 (%) >50 (Yo) aSource: Patterson (1976).
Native
Activated
Active carbon
8 0.684.90 68
2.8-6.0 0.32-0.68 165-310
6.0-1 0.0 0.384.43 500-900
19 20 19 42
10-15 20-25 25-30 30-40 30-40 40-50
30-1 0
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Neutralized Oil
I
Heatiy Up
1 7MIO.C Vacuum (-XI hPa), humidm < 0 2%
w t b i of bleaching earth)
Plate-, cartndge-, dirk- filters
Polishing filter
(removal of finest bbaching earth pskkts)
Bleached oil
Disposal
(Filter oil)
Fig. 7.29. Processing flow chart of bleaching.
pumped into the bleaching vessel. For batchwise processing, this process is too complicated and not necessary. In continuous bleaching, however, it is necessary because only in this way can the exact dosing of bleaching earth be ensured. Oxygen from the air must be absent during bleaching or the oil may be oxidized. Activated bleaching earth can thus act as a catalyst; for that reason, bleaching is normally conducted under vacuum. Typical temperatures applied for bleaching are between 90 and 110°C. Temperatures exceeding 150°C must be avoided because they are sufficiently high to change the structure of the fatty acids by isomerization reactions. For heat bleaching of palm oil, this does not hold true. After bleaching, the oil is filtered to remove the bleaching earth (see Chapter 7.3.5.), which is then discarded after the adsorbed oil has been extracted. Sometimes this extraction is not worthwhile and the spent earth is disposed of (see Chapter 7.3.6)To remove the finest bleaching earth particles, the oil has to pass through polishing filters before being pumped to storage.
7.3.3.7Plants for Discontinuous Bleaching. Plants for discontinuous bleaching are the same as those for discontinuous neutralization. Most often, these processing steps are carried out one after the other in the same batch vessel after the neutral-
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Fats and Oils Handbook
Fig. 7.30. Plant for discontinuous bleaching.
ized oil has been prepared for bleaching (see Chapter 7.3.4.). The vessels themselves are therefore often called neutralizershleachers. If the oil is additionally interesterified, this can also be done discontinuously in the same vessel after neutralization but before bleaching. Figure 7.30 shows a plant for discontinuous batchwise bleaching of oils and fats. The plant shown has different vessels for neutralization (1) and bleaching (3). The oil is pumped from the neutralizer into the bleacher after the soap has been separated and pumped into storage (2). After the oil is dried, the bleaching agent is sucked into the bleaching vessel (3) by means of a vacuum. After being stirred for some time, the mixture is pumped with a pump (4) into the filter presses ( 5 ) where the bleaching agent is removed. The oil is collected in the filter oil vessel and intermediately stored before deodorization. The sizes of bleachers are between 10 and 40 ton. As an example, Figure 7.31 shows the processing cycles for bleaching of an oil in a neutralizerhixer. 7.3.3.2 Plants for Semicontinuous Bleaching. As shown in Figure 7.31, the process consists of four major steps, namely, heating and drying, settling and stirring, cooling and filtration. If these four steps are carried out one after the other in four stacked trays housed in a vertical vessel, a semicontinuous process can be performed (Fig. 7.32). The neutralized oil is pumped into the upper tray of the bleacher and is steam-heated to bleaching temperature. The tray is evacuated during this operation. After the oil has been dried and heated up, it flows into the second tray where the bleaching earth/oil slurry is dosed. Here it is held for the reaction period
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65 1
Stirring, -40min”
dependkg on
Filter oil
(Z5@500 L/rr+h)
(nwimbd,bbschKl)
Fig. 7.31. Processing flow chart of batch bleaching.
while being stirred. After that, the oil falls into tray three where it is cooled to filtration temperature. The lowest tray is used as a buffer for filtration. Athanassiadis ( 1980) gave the average energy consumptions for bleaching including neutralization using 1% bleaching earth and hermetic filters (Table 7.10). If hermetic filters are steamed before discharge of the bleaching earth, the amount of steam has to be increased by 15 kg/ton of oil. The figures in the table do not include the part of the energy that is required to extract the adsorbed oil from the bleaching earth.
7.3.’3.3Plants for Continuous Bleaching. Continuous bleaching plants are commercially viable if long runs of one and the same oil must be bleached. Their work-
Fig. 7.32. Semicontinuous bleaching plant (courtesy of Lurgi GmbH, Frankfurt).
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TABLE 7.1 0 Energy Consumption for Neutralization and Bleaching, Inclusive of Washing and Dryinga Heat recovery Energy consumption (kg steamlton of oil) for Heating of crude oil (20°C Hot water production Vacuum production Total
+ 110°C)
Without
With
88 30 50 168
38 18 35
91
aSource: Athanassiadis (1980).
ing principle is based on the fact that the oil to be bleached is blended with an oiybleaching earth slurry and passes through the reaction vessel under predetermined conditions. During this passage, the four steps of bleaching outlined above are carried out consecutively. Like all continuous processes, this process can also be easily automated and, as a matter of routine, can be run by one person. However, this is also possible with semicontinuous or discontinuous plants if they are well designed. Figure 7.33 shows the configuration of a continuous bleaching plant. The oil is pumped from a vacuum dryer (not shown) into the bleaching vessel while passing through a heat exchanger on its way. An aliquot of the oil is pumped into a vessel where bleaching earth is dosed from the bleaching earth storage. A vacuum is applied to degas the oiybleaching earth slurry, which is pumped into the bleaching vessel. The slurry falls on a rotating disk or passes through stirred compartments in order to be well agitated, thereby ensuring intense contact. The bleaching vessel is separated by a vertical wall to force a zig-zag flow, thus increasing the time required to pass through it. Afterwards the oil passes through the plate heat exchanger in a countercurrent manner to the incoming oil for heat transfer, in this case for cooling. It is pumped to a pair of filters that are operated alternately to avoid standstill during the time of earth discharge. Different types of filters (see Chapter 7.3.5) can be used. After passing through a polishing filter, the oil is stored (filter oil storage). The earth is collected and discharged or the adsorbed oil is extracted. 7.3.4 Pretreatment of the Oils to Be Bleached
To ensure an optimum effect of the bleaching earth, it is necessary to avoid reducing its activity as a result of impurities in the oil or inadequate processing conditions. This is especially important because it is the only way to minimize the consumption of bleaching earth. High amounts of bleaching earth-in addition to the cost of the earth itself-always cause high oil losses. This adsorbed oil suffers quality deterioration even if recycled via extraction; it is therefore often no longer considered as food grade. In addition, extracting the oil is very cost intensive. One of the factors that negatively influence the activity of the earth is the oil’s soap content. The acid groups of the activated montmorillonite are able to promote
653
Oil Purification
BLEACHER
Fig. 7.33. Continuous bleaching plant (left; redrawn; courtesy of Lurgi CmbH, Frankfurt) and continuous bleacher (redrawn; courtesy of De Smet S.A., Edegem).
soap splitting. On the one hand, FFA are formed, which adversely affect the value of the oil and reduce the activity of the earth by blocking the active centers of the earth. On the other hand, the acid groups are inactivated by a neutralization via ion exchange of H+vs. Na+. The soap content should therefore be as low as possible, meaning that the oil has to be washed carefully. Careful neutralization is indeed a prerequisite for successful bleaching. The water content of the oils also plays a role because fats can be hydrolyzed under bleaching conditions (90-1 10°C, bleaching earth catalysis). However, a certain humidity is necessary to increase the activity of the earth. It should not exceed 0.1%. Because bleaching earth is also a good oxidation catalyst (Zschau 1985), the working atmosphere should be oxygen free. It is therefore preferred to work under vacuum. This is the only way to ensure that conjugated dienes and polyenes are not formed. If present, they are formed by decomposition of hydroperoxides. Most bleaching plants are run under a vacuum of 30-40 hPa. 7.3.5 The Filtration of the Bleaching Agent
Filtration through a porous medium depends on the filtration area (F),the filtration time (0,the pressure difference (Ap), the viscosity of the filtrate (E), the thickness
654
Fats and Oils Handbook
(T) of the porous medium, and its permeability (P).Bringing all of these parameters together in one equation results in the following (Darcy’s Law):
[7.18]
The quotient of AV and At is the specific flow rate, which is volume per time and per area. Multiplied by the area F, this leads to the flux rate of the filter as follows: [7.19]
If the quotient of permeability and thickness of the filter medium PIT is replaced by the sum of the resistance of the apparatus and the cake RA + RK, Equation [7.20] results:
[7.20] Assuming a homogeneous distribution of the liquid, Equation [7.20] can further be developed by introducing it into Equation [7.21] V RK = r . m F
[7.21]
where r is the specific resistance of the filter cake and m is the proportion of solids per volume of filtered suspension. The equation is valid under the assumption that the filter cake is incompressible. Equation [7.20] becomes AV -F . At
-
Ap (RA+ r . mV/F) . &
[7.22]
From this equation, the parameters of filtration and their influence can be read. An overview of recent developments of filtration techniques was given by Esser et al. (1985) and Gosele (1987); a special review on filtration techniques in the bleaching process was given by DGF (1996). Figure 7.34 shows the formation of the cake with and without filter aid. The filter has to be precoated (“black run”); then particles smaller than the cloth’s mesh size are retained by the bridges of larger particles sticking together, holding back the smaller ones.
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655
Cake forrnation (precoating:
.Bleachingeiaith partidea 'I
Cake formation with filter aid
Fig. 7.34. Cake formation with
and without filter aid (after DCF 1996).
7.3.5.7 Plate Filter Presses. In many factories, bleaching earth is still filtered via plate filter presses. Plate filter presses consist of a horizontal stack of hollow plates equipped with filter cloths. The surface of the plates is porous so that the oil can be pressed into the inside of the plate and the filter cloth holds back the bleaching agent. With old plates, which are usually manufactured from cast iron, every single plate has a side exit that enables the oil to drain off. The oil leaves the plate via a tap and flows into an open drain that runs along the whole side of the press (Fig. 7.35). More recent plates are constructed with a central hole, which forms a pipe when many plates are tightly pressed together. The oil then drains off via that pipe without coming into contact with the oxygen of the air. After the filter plates are fully loaded with bleachtng earth so that it has to be removed, the plates from the stack are separated from each other. At one time, this was done manually; today, the plates are separated via a motor-driven chain. This chain saves the hard manual labor and ensures that the plates are an equal distance from each other. Underneath the plates is a large container into which the bleaching agent falls. This container can be opened on the lower side, and the bleaching agent can thus be discharged, falting from the plate press via the container into small carts, or it is removed by means of a screw. If the bleaching agent does not loosen from the plates, it is manually removed by means of a knife-like device. To ensure good functionality, it is essential to use a suitable filter cloth. This cloth must have the following properties: high mechanical resistance, suitable pore size, low tendency to becoming stuck and long standing time.
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Fats and Oils Handbook
Fig. 7.35. Plate filter press (schematic)and traditional filtration plant with open outlet. Mechanical resistance is necessary because, on the one hand, the cloth has to withstand the forces imposed on it by filtration; these are not too high because the plate acts as a support. On the other hand, however, it has to withstand the mechanical drawing off of the earth and repetitive cleaning. If monofile filter cloths are used, it is easily possible to achieve mesh sizes as small as 30pm.Such cloths can withstand pressure up to 500 bar (Hermann 1988). Such high pressures, of course, are not necessary for the filtration of bleaching earth or hardening catalyst; however, they are a measure of the stability of the fabric. A suitable pore size reflects a compromise between high filtration capacity (large pore size) and short black run (small pore size). In the phase of filter cake formation via bridge building of the solid particles, many of these solid particles pass through the filter. This is the so-called black run because the bleaching earth is dark colored due to the adsorbed color particles. If active carbon is added, it is really black. Every filter must allow recirculation until the black run phase is completed and those parts that lie behind the filter cloth are washed clear again. The actual filtration is made possible by solid particle bridges that are formed in the course of the black run. As a rule of thumb it can be said that the pores of a filter cloth should be two to four times larger than the average size of the solid particles to be filtered off. If they are smaller than that, the pores easily become blocked and the filtration capacity is decreased. If pores are larger, the black run is prolonged and sudden increases in pressure will lead to a breakthrough of the filter cake and additional black run during filtration. Clogging of the filter cloths can be minimized if fibrous fabrics are not used; such materials have a tendency to trap solid particles, leading to stuck filters. Materials that are well dited for a filter cloth are linen as well as nylon and perlon,
657
Oil Purification
Filtration capacity [kg/m2.h]
1200
I
800-
1 \ -- -. \ 2.6 ba;-
600 -
- -\
I
400 -
5.2 bar
6.1 bar
which have mainly replaced linen today. Figure 7.36 shows the filtration capacity of an earth I which contains almost 50% solid particles with a size 4 y m and an earth I1 having only 10% solids of that size. In the beginning, earth I has a high filtration capacity that quickly decreases as the pores become stuck; at a cake thickness of 10 mm, no further satisfactory results can be obtained. Earth I1 can be filtered to a cake thickness almost twice that. High standing time has double importance. On the one hand, this means that the filter cloth can withstand many cycles of filtration and cleaning. On the other hand, the number of cycles before the cloth has to be removed for cleaning is high because the plant stands idle during changing of the cloths. Generally, working with plate presses has the disadvantage that it is very labor intensive and cannot be automated. However, these filters can be operated by less skilled personnel and have relatively low investment costs. 7.3.5.2 Continuous Filters. The filters that are called continuous are not actually continuous in reality because the bleaching agent has to be discharged when the filter is filled. This means that, in this case also, filtration has to be intermpted to discharge the solids. Compared with the filters described above, this needs only a little time to be completely automated. This represents not only great commercial progress but also a substantial improvement in the working conditions because working with the old filter presses normally took place under difficult circumstances, i.e., hard labor at high temperatures. As noted above, the continuous filters also need discharging time and, after restarting, there is a black running time. Figure 7.37 shows the cycle times of filters. To bridge the time span required for filtration, two filters can be fed by one bleacher. They then work alternately, which means that while one filter is emptied and restarted, filtration is done via the other one and vice versa.
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658
Mixture of
Duration of prcceoa rhpa [min] Cartridget.
I
Fibrprassl
Dirk filter
Filter filling
5 1
Dhcha~ingcake
3 14-1s
Oil
~
12
6
2-3
36
27-33
TOM q ~ kna k excluding kitration mtf
Fig. 7.37. Cycle time of different filter types for bleaching earth'filtration.
7.3.5.2.7 Candle filters. Candle filters consist of a number of porous tubes that are closed on their lower end and hang vertically in a hermetically closed vessel. The upper end of all of these tubes is open and connected to a piping system, which allows the liquid inside the tubes to drain off, but is closed toward the vessel. As an example, the Fundabac filter (see Fig. 7.38 and Table 7.11) consists of a number of bags stiffened by multitube elements that are systematically build into a pressure vessel. A single bag support system consists of seven tubes of equal dimensions. Six of these tubes (C) are arranged concentrically around one central tube (B). The six tubes are provided with horizontal draining slots (D). The tube bundles are covered with a suitable highpressure weave @), which fits snugly around the curved surfaces during filtration. The filter cake is built up on this weave (G).During the back wash, cycle gas is blown through the central tube (Aa) into the outer tubes (H) and through their slots (Da). Thus the weave is lifted off (Ea) the tubes, and this movement causes the cake residue to be thrown off (Fa). The filter medium is of circular weave, i.e., the medium forms a seamless hose which withstands a back wash pressure of several bar and can thus be thoroughly cleaned. The yarn is either monofile and/or multifile and meets all process conditions. The bag is clamp-futed to the tube assembly at both ends. The filtrate exits via the central tube, which also serves as the feed line for the back wash medium. The filtrate flows vertically down the external surface of the concentric tubes (H) toward the central tube through which the filtrate exits upwards (A) into the register pipe system. As a filter cloth surrounding the tubes, Fundabac, for example, uses a wire of 100-pm mesh size for the filtration of crude oil and 2 0 0 - p mesh for the filtration of bleaching earth. Amafiiter uses a cotton cloth with filter channels of l-lOqLm; however, the smaller mesh sizes serve other purposes than the filtration of bleaching earth. For filtration, the vessel is filled with the oil/bleaching earth slurry and the filter is thus precoated. After a thin filter cake has formed on the cloth, filtration can be started. The oil passes through the cloth and enters the central tube via the porous tubes. It is col-
Oil Purification
659
Fig. 7.38. Candle filter Fundabac type (courtesy of DrM, Dr. Muller AG, Mannedorf).
lected in the central tube from where it flows through the register and drains off. Lf increasing back pressure indicates that the filter cake is thick enough to require discharge, feeding of the oil/bleaching earth slurry to the filtration chamber is stopped and the chamber is emptied. Back washing is usually done with pulsed blows of nitrogen. Pulsing significantly amplifies the washing effect on the hose weave. The pulsating
0
0 0
TABLE 7.1 1 Technical Data of Candle Filter& Filtration area
(m2)
12
15
23
23
31
Total height Volume Weight Diameter Number of candles Number of registers Candle length
(mm)
2641 2342 975 1200 36 6 1250
3041 2794 1070 1200 36 6 1650
3891 3755 1271 1200 36 6 2500
3068 4520 1717 1600 72 10 1250
3568 5324 1874 1600 72 10 1650
(L)
(k@ (mm)
36 6 (mm)
46 4318 7032 2210 1600 72 10 2500
48
63
95
3636 9305 3298 2200 148 14 1250
4036 10,759 3553 2200 148 14 1650
4886 13,841 4093 2200 148 14 2500
2 i:
T a k e thickness, 2&30 mm; throughput 40&500 Um2; filter type Fundabac.
Iu
9
TABLE 7.1 2
9 z
Technical Data of Plate Filter&
1: Vertical: maximum capacity (Uh)
2.5 Filter area Tank diameter Tank capacity Number of plates Length Width Height Weight (no drive) aSoybeanoil with 1% of bleaching earth. bNiagara type filter, courtesy of Amafilter b.v., Alkmaar.
Horizontal: maximum capacity (Uh)
5.0
7.5
12.5
2.5
7.5
15.0
25.0
20 1070 1.6 13 2 700 1900 3280 1400
30 1220 2.4 15 3000 2150 3540 2200
50 1500 4.3 17 2500 2600 3850 2650
10 914 1.1 15 3730 1650 2135 1300
30 1220 2.6 22 5590 2200 2650 21 50
60 1220 4.5 44 8890 2220 2650 2780
100 1530 8.0 49 10,010 2500 3050 4000
8 0 2.
Oil Purification
661
effect is brought about by a motor-driven rotating ball valve in the air feed line. The washing effect results from flutter of the hose caused by pulsating the gas stream. Instead of nitrogen, steam can also be used. Air is strictly forbidden because back washing with air could lead to immediate ignition of the hot oil that is finely dispersed over the large surface area of the bleaching agent. This kind of filtration can be repeated, fully automated, as often as desired and therefore constitutes in effect a continuous process. One of the advantages of that kind of filter and the vertical Niagara filter (see Chapter 7.3.5.2.2.)is that the candle filter has no movable or motor-driven parts. 7.3.5.2.2 Tank filters (leaf filters). Tank filters follow similar construction principles as those applied for candle filters. Equivalent to the so-called candles, filter leaves hang in the tank. The best known filter of that type is the Niagara filter of Amafilter (Fig. 7.39). This type of filter is operated in the same way as described for the candle filters. The difference is in the cake discharge, which is achieved by means of a pneumatically operated leaf vibrator. In the horizontal types, discharge is achieved via a manual cake door, which may also be operated by a hydraulic drive. The cover of the tank is closed by eyebolts and hand wheels and can be fully opened, ensuring easy access to its interior. Tank filters are delivered with filtration areas of up to 50 m2, Normal working pressure is 4.5 bar with a maximum of up to 10 bar. Under suitable processing conditions, the filters can be operated for up to 2.5 h without bleaching earth discharge. The separated cake contains up to 25% oil. If such filters are used for crude oil filtration, the solids content should not exceed 7% and the operation temperature should be 4 0 ° C . If nickel hardening catalysts are filtered, a cake can be formed if the oil contains 9 . 3 % solids (ten Hage 1986). Such filter cakes hold 40% oil. Applying winterization filtration, the standing time of the filter can be up to 8 h between two cake discharges. Niagara filters are also available as horizontal filters in which case the bleaching earth is mechanically separated from the filter leaves. As a result of the lighter construction made possible by the horizontal design, the filtration area can be up to 100 m* (Fig. 7.39). For discharge, the filter is opened at the side and the stack of leaves is driven out of the tank. Technical data of vertical and horizontal tank filters are summarized in Table 7.12 (p. 660). 7.3.5.2.3 Centrifugal discharge filter. Centrifugal discharge filters are also called disk-filters. The filter consists of a pressure tank with a central hollow shaft on which a series of disk-filter elements are arranged at specific intervals. The tank is usually pressure tight to 5 bar (special make to 30 bar) and can be used up to 110°C (Fig. 7.40). The filter stack, comprising the hollow shaft and the elements, is located so that it can rotate within the tank. The filter elements are fitted with woven wire, textile material, sintered metal or perforated plates, depending on the requirements. The drive of the filter stack is either mechanical, using hydraulic coupling and reduction gear box, or a steplessly variable hydrostatic drive.
662
Fats and Oils Handbook
Fig. 7.39. Vertical and horizontal tank filters with filter leaves (type Niagara; courtesy of Amafilter b.v., Alkrnaar).
As with candle filters, the filter chamber is filled with the oivbleaching earth slurry until the filter-disks are precoated. If the filter cake is thick enough to be discharged, the oiyearth slurry not yet filtered is pumped off the filter chamber. Then the whole stack is spun by means of a drive system. The cake is then thrown off by the centrifugal forces and crashes against the wall of the tank where it cracks and falls to its bottom. Emptying the filter takes. 1-2 min. Then, the filtration chamber is filled again and
Oil Purification
663
Fig. 7.40. Centrifugal discharge filters (disk filters); types Funda (upper right) and Schenk; A = hydrodrive or electromotor; 6 = shaft suspension; C = upper bearing and seal; D = filter plates; E = lower bearing and seal; F = filtrate nozzle; G = slurry discharge; (courtesy of Schenk GmbH, Schwabisch Cmund and Dr. Muller AG, MannedorD.
Fats and Oils Handbook
664
TABLE 7.1 3 Technical Data of Schenk Disk Filtersa Filter area
(-m*)
5
10
15
30
40
50
Total height with drive Vessel volume Weight with drive Drive Vessel diameter Disk diameter Number of disks Turbid volume
(mm) (L) (k!4
1735 350 1200 7.5 900 805 10 0.15
2100 700 1600 11
2510 1000 2000 15 900
2850 1800 4700 37 1350 1200 28 0.9
3230 2200 5050 37 1350 1200 37 1.2
3580 2900 5350 37 1350 1200 47 1.5
(kw) (mm) (mm) (m3)
900
805 21 0.3
805
32 0.45
aCourtesy of Schenk GmbH, Schwabisch Gmund.
filtration is continued. The thickness of the filter cake is at most 30 mm with a spacing between the disks of roughly 40 mm. This is equivalent to -20 kg of bleaching earth per square meter of filter area. Mesh size of the filter is 5CL130"m. This leads to a filtration capacity depending on the earth and thickness of the cake of 300-600 U(h . m2) of filtration area if run continuously. Approximately twice that flow rate is needed to ensure good precoating (duration -5 min). If individual batches of oil have to be filtered, the filtration capacity is much lower. The technical data of such filters are summarized in Table 7.13. 7.3.6 Recovery of Oil from Spent Bleaching Earth
Assuming that the average amount of bleaching earth applied is 1% (wt/wt of the oil) and that bleaching earth adsorbs approximately its own weight in oil, 1% of the bleached oil would be lost if not recovered. There are two principal ways to recover the oil, namely, to extract the earth or to drive out the oil from the earth with water (steam) and a surface-active agent. To ensure that the extracted oil is edible grade, extraction must be carried out immediately after bleaching. Otherwise, the oil quality worsens because of the large surface exposed of the adsorbed oil to the oxygen of the ambient air (Table 7.14). After recovery of the oil, the bleaching earth is mainly deposited (special waste). Following recent developments, it can also be used as a raw material for the cement and brick industry. These industries, however, are interested in the earth only if it still contains the oil that then serves as a fuel to heat up the ovens, Recently, it has also been found that if bleaching earth is composted, it serves well to loosen the compost. 7.3.6.1 Water Treatment. If the oil is driven out of the earth with hot water, oils of restricted quality are obtained because this process extracts not only the oil but also adsorbed polar substances such as oxidation products. The advantage of this processes is that, contrary to solvent extraction, explosive solvents are avoided. To achieve good results, a processing aid, usually a detergent, has to be added to the hot water. A second advantage of this process is that the solid earth that is obtained can easily be
Oil Purification
665
TABLE 7.14
Influence of Storage Time on Quality and Quantity of Extracted OilaTb Storage time of bleaching earth (d) Soybean oil extracted from bleaching earth with 30% oil content
0 1 2
Extraction yield (YO) 95 92 83
5
50
10
25
Comparison: fresh oil, neutralized, bleached
Color
FFA (%I
1 .O d 4.2 d 13 i 23 i 100 i
6.01 13.9
2.2 d
0.09
0.11 0.54 3.14
ad,dichromate;
i, iodine color; FFA, free fatty acids. bSource:Gander (1 969).
deposited, but this advantage has to be paid for by a high effluent load that requires purification. In this process, residual oil in the bleaching earth lies between 5 and 50% (wt/wt of the earth). 7.3.6.2 Extraction. Like oilseeds, bleaching earth can also be extracted with solvents. If bleaching is done in the oil mill, bleaching earth is often combined with the crude seed and extracted again. In stand-alone refineries, the earth is extracted as such. In principle, the process follows the same pattern as that for the extraction of seeds (see Chapter 5 ) . Because of the much smaller amount, discontinuous batch extractors are used almost exclusively. If solvent extraction is done in a refinery, usually the building for that process is detached and erected at some distance to the rest of the plant. Not only would damage be minimized if the plant were to explode, but also the complete refinery plant would otherwise have to be built explosion-proof and would have to be run under difficult circumstances. Another possibility is to extract the earth directly in the filter after the oil has been filtered off. To do so, the oil-free filter is filled with hexane, extracted, the miscella is pumped off and the filter is steam blown to evaporate the residual hexane. The extracted earth should be removed under inert gas atmosphere. 7.3.6.3 Other Processes. Weber (1980) reported a new process, offered under the name of Contiblex by Extechnic (now Krupp Maschinentechnik). This process is a combination of extraction and hot water treatment. The aim is to combine the advantages of both systems without their disadvantages. The process is run in a combined extraction separation column. The bleaching earth is suspended in a solvent (usually hexane) and fed to the column in a finely dispersed form. The column is half filled with water and covered with the same volume of hexane (Fig. 7.41).The suspension of finely dispersed bleaching earth is dosed under the hexane surface. The bleaching earth sediments and is extracted on its way downward. From the bottom, fresh hexane is fed and, at the top, the miscella is drained off. In
Fats and Oils Handbook
666
Oily bleaching earth
Fig. 7.41. Plant for bleaching earth recovery with the Contiblex process (courtesy of Ex Technik, now Krupp).
countercurrent extraction. During sedimentation of the extracted bleaching earth through the water layer, the solvent is dnven out of the earth. The sedimented layer, once it has reached a certain thickness, is impermeable to water and can be removed with a screw. The miscella is stripped, and the water vapor condensate formed is used to refill the water reservoir in the column because part of the water is carried out together with the bleaching earth. The separation of hexane and oil follows the principles described in Chapter 5. The above-described plant delivers a miscella with 1&15% oil and extracted bleaching earth with a residual oil content of 0.1% (optimum). The working temperature lies between 40 and 50°C. The manufacturers claim a consumption of 800 kg of steam, 30 m3 of cooling water and 30 k W h of electrical energy to process loo0 kg of bleaching earth. The advantage of that process is that good oil quality is combined with a bleaching earth that can easily be deposited without creating effluent problems. 7.3.7 Heat Bleaching
The deodorization step carried out at 250-260°C during physical refining of palm oil (see Chapter 7.5.3.) is called heat bleaching.
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667
7.3.7.7 Theory of Heat Bleaching. At high temperature, carotenes are thermally decomposed. According to Young (1978), temperatures of 260°C are required for this process. Carotenes are present in palm oil in substantial amounts (500-600 ppm) and are responsible for the orange red color of crude palm oil. 7.3.7.2 Pretreatment of Palm Oil for Heat Bleaching. Heat bleaching of palm oil requires some pretreatment. Although the amount of phosphatides in palm oil is very small, the oil should be degummed to ensure good refining results. Because of the low amount of gums, no filterable precipitate can be formed. Therefore, some bleaching earth is added to make the phosphatides filterable after an excess of phosphoric acid has been neutralized. As a second effect, the bleaching earth prebleaches the oil. At 1 1O-12O0C, part of the carotenoids is adsorbed. The process conditions of palm oil heat treatment are described in more detail in Chapter 7.5 because bleaching is carried out simultaneously with physical refining. The flow chart (Fig. 7.42) shows mainly the pretreatment steps. In some Asian countries, a combined process for palm oil bleaching is applied. In this process, a first bleaching is carried out at 150-160°C with 3-5% bleaching earth. Then the oil is deodorized batchwise at 190-200°C. As can be expected, the bleaching result depends on time and bleaching temperature. High temperature ensures good success even within 5 min (Fig. 7.43).
7.4 Deodorization Oils and fats contain undesired odor and flavor components that have to be removed. These are minor natural components or components that have formed
Preheating Drying, Degassing
150'C, Zmin, 2hPa
I Heat bleaching Deodorization
25C-260°C, 30-45 min, 3-8 hPa
Fats and Oils Handbook
668
100
Palm oil Bleaching temperature ["C]:
9)
5 g 0
20
0
0
10
20 30 40 Bleaching time [min]
50
60
Fig. 7.43. Bleaching result depending on time and temperature (after Loncin 1970).
during storage or transport. The main representatives of this group of components are the hydrocarbons, aldehydes, ketones, lactones, and FFA. Grosch (1987) gave an overview of the enzymic formation of such flavor and odor substances from lipids. Eichner (1986) reported on carbonyl components with low threshold values for odor or taste. The substances he researched were oxidation products of lipids. Dependent on the concentration these substances have an unpleasant repellent character. The number of substances that are responsible for offtaste is very large. Smouse and Chang (1967) and Chang er al. (1967) found the following volatile components in aged soybean oil. All of these components added to an off-taste: 22 acid components, 18 aldehydes, 8 ketones, 8 alcohols, 2 esters, 6 hydrocarbons, 3 lactones and 4 other components. It must be noted that hydrocarbons add to taste or smell only if they are unsaturated. Their proportion is very, very small. Marcelet (1936) identified 70 ppm in olive oil and 20 ppm in peanut oil of unsaturated hydrocarbons that were responsible for a repulsive taste. Aldehydes and ketones have a much larger influence than unsaturated hydrocarbons. The threshold values (i.e., the concentration at which 50% of the members of a test group recognize the substance) of these substances in oils is far below 1 ppm (Table 7.15). As Table 7.16 indicates, there is quite a difference between taste and smell and the matrix from which these components arise. The taste impression of fatty acids is rancid for C4-C6, above which it is dull and soapy. Aldehydes and ketones are formed mainly autocatalytically from hydroperoxides (see Chapter 2.4.3) that decompose to form them after a certain time. Table 7.17 shows some aldehydes and ketones with the off-taste they create. As a total, odoriferous components generally add up to not more than 200 ppm. This is very low compared
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669
TABLE 7.1 5 Threshold Values for Some Substances Causing Off-Taste in Oils and Fatsa Dissolved in Caprylic acid Capric acid Octanal Dodecanal Hexenal
Nonenal Nonadienal
Threshold value (DDrn)
Vegetable oil
(trans-Z-) (cis-2-) (trans-3-) (cis-34 (trans-6-) (cis-64 (cis-24 (cis-2-)
350 200 0.9 0.9 2.5 0.15 1.2 0.1 1 0.0003 0.002 0.01 8 0.002 0.65 0.1 9
Paraffinic oil
Water
2-Heptanone 2-Nonanone aSource: DGF (1981).
with the fatty acids that may be present on the order of some percentages. However, the effect on the quality is just the reverse. 7.4.1 The History of Deodorization
The first application of deodorization for edible fats and oils occurred in the middle of the 19th century by Cassgrand (1854) long after it had been known for the purification of organic compounds. In 1855, the first patent was granted to Bardies. Detailed overviews of the beginnings of deodorization are given by Markley (1961), Lude (1962), Swern (1964) and the DGF (1981). In the year 1893, the first German patent to be actually applied in practice was granted. It describes the deodorization of coconut oil. A product produced according to a similar process since 1921 remains on TABLE 7.1 6 Threshold Values for the Taste of Short-Chain Fatty Acid9 ~~
Coconut oil
Dairy cream Fatty acid (pprn) in Butyric Caproic Caprylic Capric Lauric Myristic
C40 C, C, C, C,, C14
Smell
Taste
Sweet cream butter
Smell
Taste
50 85 2 00 >400 >400 >400
60 105 120 90 130 >400
40 15 455 250 200 5000
35 25 >loo0 >loo0 >loo0 21 000
160 50 25 15 35 75
aSources: Crosch (1987), Halsbeck eta/. (1986), and Pfannhauser (1994).
670
Fats and Oils Handbook
TABLE 7.1 7 Components Causing Off-Taste in Fats and Oils ~
~
Component
Taste imDression
Reference
cis-3-Heptenal 2,4-Heptadienal 2,4-Decadienal Vinylamylketon trans-2-, cis-6-Nonadienol Diacetyl 2 -Penty lfuran cis-4-Heptenal trans-2-, cis-4-, cis-7-Decatrienal
Green taste of soybean oil Green taste of soybean oil Aged soybean oil Aged soybean oil Aged soybean oil Buttery Green beans Fishy Fishy
Hoffmann (1961) Hoffmann (1961) Hoffmann (1961) Hill and Harnrnond (1965) Hill and Harnmond (1965) Seals and Hamrnond 11 966) Chang eta/. (1 967) Meijboom and Stroink (1972) Badings (1973)
the market. Later, better materials such as special steels were found, the deodorization temperature was increased and better plants allowed the working pressure to be reduced, thus making the plants much more effective. 7.4.2 The Theory of Deodorization
The vapor pressure of a liquid is described by Clausius-Clapeyron's equation: [7.23] where p is the vapor pressure, R is the universal gas constant, AHvapis the molar heat of evaporation, and T is the temperature (K). If In P is plotted against 1/T, a straight line is obtained from which the boiling point of the components (at the boiling point: vapor pressure = ambient pressure) can be read. The vapor pressure of some relevant components is given in Chapter 2.3.2.4. Dalton's Law describes the vapor pressure of a mixture as the sum of the partial pressures of its single components: [7.24] The partial pressure of the single components can be calculated following Raoult's law: [7.25] where pci is the vapor pressure of the pure component i and x is the mole fraction of the component in the total system { 1, 2, 3, ... ,n}. Because the total vapor pressure of a system (ideal, nonaceotropic system) according to Equation [7.24] must always be greater than the partial pressure of each single component, the boiling point of every system must be lower than the boiling point of its highest boiling component. Despite that, of course, a higher vapor pressure caused by a higher
Oil Purification
671
temperature speeds up the distillation. From Equation [7.26], it can be concluded that the ratio of the vapor pressure of the single components of the system equals the mole fraction of these components in the system: nA
nB
-PA
[7.26]
P B
where n is the number of moles. From the above equations, one can calculate to what extent the vapor pressure of different fatty acids and minor components contributes to the vapor pressure of the total system (Figs. 7.44 and 7.45). It becomes clear that in an oil with FFA and some aldehydes and ketones, the FFA contribute predominantly to the vapor pressure of the system, even more so than do the aldehydes and ketones. Assuming 0.1% ( d m ) of FFA, equivalent to 0.3% (wdwt), the vapor pressure of the triglycerides accounts only for <3% if only 0.01% of aldehydesketones are present. The distillate contains the components in the molar ratio of the share they have in the total system’s vapor pressure. Therefore, the amount of triglycerides in the distillate is low even if one takes the low molecular weight of aldehydes and ketones into account (most of the vapor phase is actually water). However, it can also be seen that the share of triglycerides in the total vapor pressure increases considerably if FFA <0.01% (wdwt) 0.03% ( d m ) must be achieved. At the same time, this means that its share in the distillate also increases, leading to higher neutral oil losses during deodorization. It can also be seen that during deodorization of laurics, higher amounts of triglycerides end up in the dis-
-
Components [% mlm, triglycerides to 1001
Fig. 7.44. Share of free fatty acids, aldehydes and ketones in the vapor pressure of their mixture with triglycerides.
Fats and Oils Handbook
672
Share in total vapor pressure at 250°C 100 6-
[%I
..-- - -
100
,' Stearic acid 10
80 60
1 40
0.1
20
Tristearin 0.01 0.
'l 0.01
0.001
o!o,
0:1
l.o I
.
0
Proportion of stearic acid [% m/m] in the stearic acidbristearin mixture
Fig. 7.45. Share of stearic acid and tristearin in the vapor pressure of its mixture. tillate. This is due to the higher vapor pressure of the lauric triglycerides. On the other hand, this facilitates the deodorization. In addition, it can be seen from the graph how low the pressure of a plant must be to enable a certain minimum FFA concentration in the deodorized oil. At the temperatures considered for deodorization,the vapor pressures of FFA are so low that pressures (vacuum) would have to be applied that are too low to be realized in the plant. Therefore, steam as an additional component is used to reduce temperatures to an acceptable level and produce achievable pressures. Steam with its vapor pressure is thus compensating for the gap between achievable and manageable pressure in the plant. In addition, its low molecular weight is favorable because the c o m p nents to be separated and the entrainer are distilled in the molar ratio of their relative vapor pressures. Consequently, with a low (weight) amount of water, a large amount of aldehydes and ketones can be removed. For water in steam distillation with the component A, Equation 17.261becomes
[7.27] in which A may also represent the total system with all components 1 to i of the oil to be deodorized. The boiling point temperature of the mixture is then below that of water, i.e., c100"C. These theoretical equations can be adjusted to practical deodorization (DGF 1988). The vapor pressure of water pHZO can be replaced by the mean distillation
Oil Purification
673
pressure pD, which also takes into account the height of the oil layer (especially important for batch plants):
[7.28] where p D = p + p . g . h/2, h is the height of the oil layer, g is the acceleration due to gravity, p is the density of the oil, and p is the vapor pressure of the system. At 250°C the thickness of the oil layer adds -0.6 mm Hg (1.33 hPa) to the total pressure for each centimeter of oil height. According to Bailey (1941), an evaporation factor E can be introduced, which may also be called the efficiency of deodorization (it reflects the ratio between actual and theoretical partial pressure); the equation is integrated after introducing some assumptions and Equation [7.29] (DGF 1988) is obtained:
[7.29] where x1 and x2 are the initial and the end mole fractions, respectively, of the volatile component i. The equation gives the amount of steam necessary at a given initial concentration x1 to achieve the desired end concentration x2. This equation is theoretical and can describe reality satisfactorily only if an empirical factor that must be determined experimentally is added. Szabo Sarkadi (1958) added this factor Ai (which is related to mass transfer properties of the system) to the numerator of Equation [7.29]. This factor can be found in standard tables. 7.4.3 The Process Conditions
Apart from the fact that certain processing conditions are necessary to conduct the process, they also have a large influence on the quality of the products and the processing costs. The influence of the different variables on processing is shown in Table 7.18. Most important are, of course, the vapor pressures of the individual TABLE 7.1 8
Processing Parameters influencing Deodorization Influencing Influencing factor: Pressure Deodorization time FiIIing height Temperature (+ = directly proportional,
Pressure
[-I [-I I-]
Temperature needed
Steam consumption
+
+ +
[+I
+
- = indirectly proportional, [I = indirect influence.
+ -
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Fats and Oils Handbook
components and the means to influence them. Fortunately, the vapor pressure of the triglycerides themselves is very low so that they can be retained without too high losses. More recently, increased attention has been given to the minor components that are present in the oil and their removal or the possibilities of recovering them in the distillate. As a very rough indication for the order of magnitude, rounded values for the relative vapor pressures at 240°C of some components present in the oils are given: Triglycerides (tristearin) Sterol esters Sterols Tocopherol
1 -400 -6500 -9500
Squalene Fatty acids (stearic acid) AldehydedKetones (hexanal)
-12,000 100,000 -50,000,000
-
7.4.3.7 Deodorization Time. The time necessary to separate a certain amount of undesired components from the oil depends mainly on the speed with which the necessary amount of stripping steam can be introduced. Due to the principle of steam distillation, steam makes up the major part of the vapors. Because it has to be brought into the system and be removed from it, it is significantly important. It is assumed that the oil and the steam blown in have sufficiently high temperatures. The deodorization time is between 20 and 120 min (usually it is -90 min) without time for heating and cooling the oil. In batch deodorization, cycle times are between 180 and 480 min. In semicontinuous plants, deodorization is done in muItiple steps in trays. In this case, the total deodorization time is the sum of the individual steps. Deodorization time also increases with the height of the oil in the deodorizer, i.e., with the thickness of the oil layer that the stripping stream has to penetrate. Because all side reactions are also time dependent, deodorization time is kept as low as possible. In Europe, longer deodorization time and lower temperatures are preferred. In the U.S., the reverse is true. 7.4.3.2 Deodorization Temperature. Temperaturt has its influence on deodorization because the vapor pressure is directly proportional to it. Therefore, a temperature increase raises the volatility of odoriferous substances, thus easing their removal. However, temperature increase is limited as a result of two factors. One is the economy and the other one is the insufficient thermal stability of the oil. Primarily because of the thermal instability of the oil above -28OoC, many years ago the industry in Germany voluntarily agreed to limit deodorization temperature to 250°C (distillative neutralization 270°C). Above this temperature, a heatinduced formation of degradation products is possible. Higher temperature would not be in accordance with good manufacturing practice. A commission of Deutsche Forschungsgemeinschaft (DFG 1967) decided on processing limits that were updated in 1973. These limits are based on research done by Lang et al. (1966). Eder (1982) analyzed different samples of oil that had been processed in the oils and fats industry and could not find any artifacts. The proportion of dimers and polymers was significantly below the level found after deep frying, for example.
Oil Purification
675
Increasing the temperature by 17K approximately halves the deodorization time needed. Every further increase by that amount halves it again, which means that an increase of n . 17K decreases deodorization time by the factor 2". The value of 17K can be theoretically deduced and was c o n f i i e d empirically by Mattil (1964), who measured deodorization time depending on temperature. The actual temperatures, however, depend on the individual equipment (deodorizer system). 7.4.3.3 Deodorization Pressure. If the pressure is decreased, the temperature required also decreases because a lower vapor pressure is then sufficient to ensure evaporation. At equal temperature, the vapor pressure of the components to be distilled off increases relative to the vapor pressure of the system. This pressure has to be achieved to ensure evaporation. In addition, reduced pressure helps to protect the oil from oxidation because oxygen from the air is reduced almost to zero. The amount of distillation steam required is also directly proportional to the pressure. If the pressure is halved steam consumption also halves. 7.4.3.4 Stripping Steam. The amount of live steam necessary is directly linked to its volume. Therefore, the lower the pressure, the less steam (wt/wt %) is needed. The height of the oil in the vessel also influences the consumption of steam because the steam has to work against the hydrostatic pressure to be able to penetrate the oil before being sucked off or distilling off from its surface. Here, especially, plants for batch deodorization are disadvantageous because the thick oil layer causes a higher steam consumption. Equation [7.29] shows that the amount of steam required is directly proportional to the vapor pressure of the volatile components such as aldehydes, ketones and fatty acids. In Equation [7.23], the natural logarithm of the vapor pressure is proportional to the temperature. T o ensure good deodorization, live steam must uniformly disperse throughout the oil as it rises to the surface. After being blown in by various means, it is expanded under the effect of vacuum, thereby increasing its surface area. On the surface of the steam bubbles, the oiYsteani contact must be maximized; there the sparge steam has its lowest specific volume, equivalent to the highest relative surface area. Athanassiadis (199 1) postulated that 300,000 m3 was a minimum contact area of oiYsteam for every kilogram of steam injected to ensure good deodorization efficiency. He also regarded a minimum of 40 recirculations of the oil during one deodorization cycle as necessary to ensure proper contact. 7.4.4 Deodorization Plants
As stated before in the case of all other steps of oil processing, there is a development from batchwise via semicontinuous to continuous plants for deodorization. During deodorization, the oil has to pass through the processing steps shown in Figure 7.46. Depending on the processing equipment, these steps are passed through one after the other in a single apparatus (discontinuous processing) or in
Fats and Oils Handbook
676
s; Filteroil I
(bbachsd OH)
Pumping in
I
Cooling
1
I Emptyins
Deodorized Oil
Fig. 7.46. Deodorization processing steps.
separated steps, thus reflecting these processing steps (semicontinuous process). The processing steps are then carried out in so-called trays, which are compartments of a vessel with some trays dedicated to heating and cooling and some to deodorization itself. Heating can be carried out in two steps; in the first, the oil is heated countercurrently by the hot oil, which is leaving the plant. In continuous plants, all of these steps are carried out in one large vessel, and the oil is usually preheated externally. Good deodorization processing aims at very close contact between the oil and the steam to promote distillation of the undesired substances. In the traditional process, steam is blown into a vessel from its bottom, passing through the oil layer. The disadvantage of this process is the thickness of the oil layer, which causes higher steam consumption. With the transition to semicontinuous processes, the height of this oil layer can be reduced as a result of splitting the entire process into a series of partial processes. Chapter 7.4.4.3 shows some alternative methods to ensure close contact between steam and oil flowing in thin films. 7.4.4.1 Discontinuous Deodorization. Batch deodorization is carried out in a vessel that can withstand a vacuum of 2 hPa (Fig. 7.47). The oil to be deodorized is pumped in via an oil inlet (1) and is heated with heating coils. This is usually done with steam (2, steam entry; 3, condensate exit). The vapors leave the vessel via ( 5 ) , the deodorized oil is pumped off via (9). The steam required for the carrier distillation is blown in via (10). As noted above, batch vessels require more steam because the oil layer that has to be penetrated is higher than in other processing units. This excess in steam may make up to 10% of the steam required for the deodorization process itself. Deodorization time in batch deodorization is usually between 3 and 5 h and the temperatures lie between 180 and 240°C. Deodorization starts at around 160°C. The advantages of batch deodorization are its high flexibility and the very low investment costs. It is therefore best suited for small plants and those that have to cope with small batches of different compositions.
677
O i l Purification
7
' I
9'
Fig. 7.47. Batch deodorizer.
Batch vessels can hold up to 40 ton of oil. Usually this amount is 10-20 ton. For large vessels, the heating time may be up to 2 h, depending on the amount of steam passing through the heating coil and on the heating area. Heating times of 1 h are typical. Because cooling takes approximately the same amount of time, a cycle in these plants can last up to 8 h. The deodorization pressure is usually -10-28 hPa. The carrying steam is blown in via star-, spiral- or screw-formed perforated pipes that are fixed on the bottom. Figure 7.48 shows the processing flow chart of batchwise deodorization of fats and oils. 7.4.4.2 Semicontinuous Deodorization. Deodorization plants used outside oil mills today are usually semicontinuous. The processing vessel may have different forms but is always divided into compartments. The processing steps of deodorization are carried out one after the other in these compartments, which are called trays in case they are stacked (Lurgi SCD, for example). After each processing step has been completed, the oil is drained from the upper tray to the next lower tray. The main processing steps are shown in Figure 7.48.
Fats and Oils Handbook
678
B.D. Oil
(-40-c)
Fat (molten, 6o-WC)
+
1
t
-20 min
Pumping in I
to 190.240'C. (Duration 1-2 h) <<< Steam
I
190-240'C, 3-5 h, 10-20 hPa
Deodorizing I
1 I
>>> vapors Cooling externally, usually plate heat exchanger
Oil / Fat
(deodorized)
S.C.D
Fat (molten,60-90'C)
Oil (-4o'c) Tray
I
+
t I
170-180'C, 2550 hPa Drying
220.240% 5-10 hPa
3
(max 270%)
4
Deodorizing
225240'C, 5-10 hPa (max 270'C)
I
Deodorizing
220.240'C, 5-10 hPa (max 270'C) optional (with 2. tray)
Cooling 5'6
80-110'c
Oil / Fat (deodorized)
Fig. 7.48. Processing steps in batch deodorization (B.D.) and in semicontinuous deodorization (S.C.D.). Deodorizers of the Lurgi design consist of a stack of six trays. In principle, semicontinuous deodorization is an automatically controlled batchwise process. If the retention time of tray 1 is elapsed, tray 1 will be drained off into tray 2 by the automatic opening of its bottom valve. A special interlocking system is provided to assure that tray 2 is completely empty before tray 1 is drained. The circulation of
Oil Purification
679
the oil in the individual trays is done by a special mammoth pump. This is to ensure high efficiency of the injected steam and good heat transfer. The oil is heated to -170°C in tray 1 after the oil has passed through a heat transfer tray. After heating up to 240°C (normally), the deodorization is started. Deodorization requires -2.5 cycle times. Consequently, at least 3 trays are needed for deodorization. In the last tray, the oil is cooled to 110-120°C. The trays themselves usually hold 2-7 ton. Figure 7.49 shows a semicontinuous deodorizer with six trays and the peripheral equipment for vacuum generation. Because the equipment design makes it inevitable that the residence times in all trays are equal (if volume is the same), the cycle time of one cycle must be as long as the residence time required for the longest process step for which only one tray is foreseen (cycle times in Fig. 7.50). All other residence times are equal or a multiple of that one. Part of the total time of all cycles is used up for draining the trays in the order tray 6 + tray 5 + ... tray 1. For each tray, this requires -6 min, i.e., one seventh of the total cycle time of - 4 0 4 4 min. Such plants require a square space of -25 m* for the deodorizer itself and auxiliary equipment. The deodorizer is 20 m high, the auxiliary equipment 10 m. A Lurgi plant is shown in Figure 7.51. Other manufactures offer different designs; however, the principle of a continuous process imitated by batch processes split into the processing steps remains untouched. In the de Smet deodorizer, the trays are not vertically stacked, but horizontally arranged in groups of six (Fig. 7.52) with one central cell and five to surround it symmetrically. All six compartments are equally equipped with sparge steam distributors at the bottom, steam jets and lifting pumps for good agitation. They also have the same capacity. The plant capacity is up to 200 t o d d or double
Fully refined oil Cooling
c3
Fig. 7.49. Semicontinuous deodorizer (redrawn; courtesy of Lurgi CmbH, Frankfurt).
Fats Oil andPurification Oils Handbook
680
673
pressure pD, which also takes into account the height of the oil layer (especially important for batch plants): Deodor. Deodor. Wing Heating
z:.
400.
E
L
5-10 hPa
3550_ hPa
[7.28]
c
em
where p D = p + p . g . h/2, h is the height of the oil layer, g is the acceleration due to gravity, p is the density of the oil, and p is the vapor pressure of the system. At 250°C the thickness of the oil layer adds -0.6 mm Hg (1.33 hPa) to the total pressure for each centimeter of oil height. According to Bailey (1941), an evaporation factor E can be introduced, which may also be called the efficiency of deodorization (it reflects the ratio between I ' 1 , actual and 0theoretical partial pressure); the equation ,is integrated after introducing 0 20 40 80 80 loo 120 140 180 180 200 220 some assumptions and Equation [7.29] is obtained: P m(DGF t n g 1988) time [mln] I
i
'
,
I
I
I
Fig. 7.50. Cycle times and temperature profile of a five-tray semicontinuous deodorizer.
[7.29] that if two units are stacked. Stacks of three are also available. Figure 7.53 shows a plant one x2 group vessels. Theend oil enters the plant via A after being wherewith x1 and are of thethree initial and the mole fractions, respectively, ofprethe heated the hot oil, which leaves the the plant (D). In the upper part ofat A, it is volatileby component i. The equation gives amount of steam necessary a given degassed and furtherx1heated up. Itthecollects theconcentration bottom and is heated to initial concentration to achieve desiredatend x2.further This equation is deodorization From timesatisfactorily to time, the bottom of A opens andthat the theoretical andtemperature. can describe reality only if valve an empirical factor oil is be drained off into one of the deodorizing chambers B. After is must determined experimentally is added. Szabo Sarkadi (1958)deodorization added this faccompleted, theischamber the oil flows into tanksystem) C, which is kept at the tor Ai (which related toopens massand transfer properties of the to the numerator same vacuum as B.This After the oil through the cooler D countercurrently to of Equation [7.29]. factor canpasses be found in standard tables. the feed oil, it is finally cooled in E. Vapors are condensed in F. of plant is suitable for small batches of different oils or blends, for 7.4.3This Thekind Process Conditions example, those attached to margarine halls. Table 7.19 gives the average consumpApart theand factauxiliary that certain processing conditions aredeodorization. necessary to conduct the tion offrom energy material for semicontinuous process, they also have a large influence on the quality of the products and the processing The influence of the different variables processing shownoil in As stated above,on good contact is between 7.4.4.3 costs. Continuous Deodorization. Table 7.18. Most important are, of course, the vapor pressures of the individual and steam is essential for effective deodorization. In this context, continuous processing offers more opportunities than noncontinuous working. At fxst, much shallower TABLEoil 7.1 8layers can be acliieved than in noncontinuous plants because a steady managed.influencing Thus better contact can be ensured between the oil and the flow can beParameters Processing Deodorization sparge steam. The steam may be injected by means of different systems (Fig. packed columns and falling films. In 7.53). The finest films can be achieved withInfluencing addition the thin filmPressure produced, the liquid that passes packed column Influencingtofactor: Temperature neededthrough aSteam consumption is forced by the packing material to continuously change its direction of flow. + Pressure + It is thus well agitated. of falling film vessels, turbulence is created, + which Deodorization time On the walls [-I [+I + droplets, thereby ensuring + good FiIIing height effects. A rotating [-I disk creates fine oil has similar Temperature Intermixing inI-] the three other cases is achieved by allowing the - oil to intermixing. (+ = directly proportional, - = indirectly proportional, = indirect flow around or through obstacles such as[Iholes of influence. sieve plates or over steps. It can
Oil Purification
Fig. 7.51. Model photo of a semicontinuous deodorization plant.
681
682
Fats and Oils Handbook
TopvlrwdthOCblb 01 tha r h o dwdorku
Fig. 7.52. Semicontinuous deodorizer with heat recovery by direct oil-oil heat exchange (redrawn; courtesy of De Srnet S.A., Edegern). also be achieved by the injection of steam. If the oil film is sufficiently thin, enough degassing takes place automatically soon after the oil is exposed to reduced pressure. Figure 7.54 shows some details of a horizontal continuous deodorizers. The deodorization step itself follows the same principles as semicontinuous deodorization. The difference is that the discrete processing steps in the latter are spread over the entire length of the continuous deodorizer without sharp boundaries. Plant designs exist with integrated heat transfer and with external heat exchangers. Figure 7.55 shows a Lurgi plant with integrated heat transfer. The neutralized bleached oil is warmed up (W) and dried (A) before it passes a second heat exchanger for preheating. Then it passes the bottom part of the deodorizer (H) to be heated up by the deodorized hot oil, which leaves the apparatus. Indirect highpressure steam serves to reach the processing temperature. The oil then passes the different deodorizer (D) stages, which each contain direct steam-operated oil circulators. It is then cooled in the heat exchange section and some citric acid may be added if required (detail omitted in the drawing). A fine filter (F) is passed through to polish the oil before it leaves the plant to be stored. A vacuum is generated in V.
Oil Purification
B Trays
633
+ Bubble heads
Sieve plate
4
Steam, Vapors
1 Oil, Fat
Packed bed
Falling film
Rotating disk
Fig. 7.53. Technical means to ensure contact between oil and steam (redrawn from Sjoberg 1987).
Figure 7.56 shows a photo of a model of a complete plant; Table 7.20 gives average consumption. The de Smet deodorizer shown in Figure 7.57 is of similar design. The oil is fed via (1) and then consequently passes ring-shaped trays. The trays can overflow TABLE 7.19 Consumptions for Semicontinuous Deodorizationa Consumption per MT of oil De Smet, heat recovery Lurgi Steam for deodorization for vacuum generation Heating energy (gas, oil, ...) Cooling water for product cooling for vacuum generation Electrical energy Steering air (7 bar)
(kg)
20-30
(kg)
70-1 00
(MI)
2 94 5-6 12-1 6 2
(m3) (m3)
(kWh) (Nm3)
1
At 25-50 hPa working pressure in stage 1, 4-7 hPa in stages 2-6; deodorization temperature 240-270'C. Tourtesy of Lurgi CmbH, Frankfurt and De Srnet, Edegern
Without
125 500 25 13
With
17 125 150 2.8 13
684
Fats and Oils Handbook
Fig. 7.54. Details of deodorizers (UL integrated heat exchanger; UR heating tray; LL view of a heat exchanger tray through the inspection glass during fabrication; LR heating chamber; courtesy of Krupp Maschinentechnik CmbH, Hamburg).
via (3) and can be emptied via (7). Steam is injected (8) and vapors are sucked off (6,9). Shell oil can drain off via valve (1 1). Most of the deodorizers in the world follow a vertical design. The continuous KirchfeldiTirtiaux deodorizer, however, consists of horizontal cylinders. The manufacturers claim some advantages, including the great oil surface that allows for a large contact area with the steam and also the shallow layer. Figure 7.58 shows one cylinder of such a plant and a sectional drawing. The cylinders have a diameter of 95 cm and a length of 4.5-12.5 m. Double-pass cylinders may also be ordered, which are horizontally separated into two trays internally. In the lower part of the cylinder, a bank of heating tubes compensates for the heat losses during evaporation. Heating steam is fed via C and the condensate leaves via B. Sparge steam, which enters via D, is finely distributed by means of a sieve plate. The sparging gas also constantly renews the top oil layer. The product is fed via (A) and drains off via (E). The vapors are collected until they are removed through the vapor drain pipe. Splash oil is reduced by the design of that pipe. The large space over the oil ensures a large oil surface exposed to the vacuum. The complete set of pipes
Oil Purification
685
Neutralized
v Stea
I 4 Shell oil
Fig. 7.55. Continuous deodorization plant (redrawn; courtesy of Lurgi CrnbH, Frankfurt).
can be drawn off the cylinder for repair and maintenance (see upper part of Fig. 7.58). Because one cylinder is insufficient, several can be arranged sequentially to form a deodorizer. Such plants, which differ significantly in design, can be set up for capacities between 100 and 600 MT/d; two to eight cylinders are required, depending on the capacity (Fig. 7.59). 7.4.4.4 Thin-film Deodorization. The first plant for large scale (250 MT/d) thinfilm seed oil deodorization was started in 1996. It had been known for some time that thin-film stripping theoretically had considerable advantages over tray stripping. Because the steam passes over a very thin oil film in a true countercurrent operation, the contact between steam and oil is optimized. The surface area of the oil can be further increased by a special design of the packed column. Other means to enhance mass transfer are eddy currents caused by wall heat transfer in the falling film design or centrifugal action if rotating disks are used. However, there are still some major drawbacks, one of which is the increased trans fatty acid ("FA) level (Stenberg 1996). A second is the removal of antioxidants and vitamins as a result of the very high effectiveness of the operation. A third is that the heat bleaching effect may be reduced
686
Fats and Oils Handbook
Fig. 7.56. Continuous deodorization plant (courtesy of Lurgi, Frankfurt) Oelde).
68 7
Oil Purification
TABLE 7.20 Consumptions for Continuous Deodorizationa Consumption per MT of oil
(kg) (kg)
Steam for deodorization (4 bar) for vacuum generation (1 1 bar) Heating energy (gas, oil, ...)* Cooling water for product cooling for vacuum generation
ikJ) (m3) (m3)
(kWh) (Nm3)
Electrical energy Steering air (7 bar)
15-20 50-70 105,000 2-3 10-12 3-5 3
Working pressure 4-7 hPa, deodorization at 240-270OC; *indicates heat recovery aCourtesy of Lurgi CmbH, Frankfurt.
---3
7
t .
11
9
Fig. 7.57. Continuous deodorizer (courtesy of de Smet).
688
Fats and Oils Handbook
Fig. 7.58. Horizontal deodorizer model photo with drawn cylinder, sectional drawing, principle design (redrawn; courtesy of Kirchfeld GmbH & Co KG, Dusseldorf and Tirtiaux s.a., Fleurus).
Oil Purification
689
Fig. 7.59. Horizontal deodorization plant type DEOTEST, model photo (courtesy of Kirchfeld CmbH & Co KG, DusseldorD.
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Fats and Oils Handbook
because of lower temperatures. In the case of TFA increase, pilot plant data showed promising results. Hence, there is more to do to enhance the advantages of the process. 7.4.5 Auxiliary Equipment 7.4.5.7 Heating the Oil. Deodorization is conducted at relatively high temperatures. Therefore it is important to have equipment available that allows these temperatures to be reached reliably and quickly to keep cycle times short. Because the oil has to be cooled after deodorization, heat integration is essential to save energy and keep the cost low. 7.4.5. 7 . 1 Steam heating. The most common way of heating is by indirect steam. To heat deodorizers, which are run at -260"C, steam of 50-70 bar is necessary (264-285°C). The boilers normally used in factories are not able to supply such pressures. Therefore, high-pressure boilers that supply the pressure needed are required. The advantage of steam is its high heat transfer, caused by the large heat of e v a p ration that is set free again during condensation. The heat transfer is about four times that of thermal oils. The second advantage, which is important in the case of a leakage, lies in the fact that the product can come into contact only with water, not with a chemical. To avoid any unacceptable risk for the consumer, responsible food producers therefore have changed their plants to run with steam only. Saturated steam of -50 bar is required to heat the oil to 240-260°C. Usually there is a preheating step to 180-200°C using steam of 15-18 bar so that high-pressure steam boilers can be kept small. 7.4.5.7.2. Heating with thermal oil. Using thermal heating oil, the investment in the plant is considerably lower. Zehnder (1976) estimated the savings at around 50%. For this reason, thermal heating oil systems have been installed in many plants. Usually, the systems use eutectic mixtures of 27% biphenyl and 73% biphenyl oxide (e.g., Dowthenn). The liquid (vapor pressure at 30O0C, -2.5 bar) can be evaporated at considerably lower pressure than water. It is nonflammable at 115°C and is flammable from 138°C upward. In 1973, Japan reported illness and fatalities that were said to be caused by the consumption of rapeseed oil containing thermal heating oil (Brekke 1980). In addition, the thermal heating oil was said to be heavily polluted. As a consequence, such plants were forbidden in Japan. Imai (1974), however, assumed that thermal heating oil that contaminates the product through a leak is removed in the deodorization process together with the undesired components. This can be the case only if the leakage does not affect the processing conditions so that they are maintained long enough after the contamination to ensure complete purification of the oil. Generally, avoiding thermal heating oil is the only completely safe way to circumvent this risk. 7.5.4.7.3 Direct heating. Kuroda and Young (1989) showed that it is also possible to heat the oil directly. Up to now, this approach has always been excluded
Oil Purification
691
because it was assumed that local superheating could not be avoided. In Asia in 1989, at least ten deodorization plants with direct heating were in operation. These plants obviously produced oil that was in no way inferior to conventionally heated oil. A special construction of the burner avoids superheating. 7.4.5.2 Vacuum Generation. Jet ejectors produce a vacuum by passing a motive fluid successively through a motive nozzle and a diffuser (Fig. 7.60). The static
Fig. 7.60. Drawing of a steam jet vacuum ejector and plant with ejector vacuum system (courtesy of Korting Hannover AG).
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Fats and Oils Handbook
pressure energy of the motive flow is converted into kinetic energy. This energy is transferred to the suction flow, thus sucking off gaseous particles. In the case of deodorizers, the motive flow usually consists of steam, i.e., the equipment used is a steam jet ejector. The main functional parts of the pump are the motive nozzle and the diffuser. Because of the design of the motive nozzle (2), i.e., decreasing throat diameter, the pressure decreases as the velocity of the fluid rises. Conversely, in the diffuser section (4,5), the flow is retarded and the pressure increases to reach discharge (atmospheric) pressure again. Pressure and speed are displayed in Figure 7.61. The lowest static pressure p s exists between motive nozzle and diffuser. The supersonic motive flow (steam) possesses high kinetic energy, which can be released to the suction flow by impulse transfer where the two flows mingle. Reaching the diffuser throat, the velocity is reduced to sonic. In its diverging section, it further decreases to reach discharge pressure pd at the end. The ratio of these two pressures p i p , is called the compression ratio of a jet ejector. Assuming the atmospheric pressure at sea level to be lo00 hPa and the working pressure at present to be between 2.5 and 4.0 hPa (sometimes lower), a compression ratio between 400 and 250 is required. This cannot be achieved by a single ejector and thus requires multistage equipment. E
I
P
Fig. 7.61. Velocities and pressures in a steam jet vacuum ejector (courtesy of Korting Hannover AC).
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7.4.5.3 Vapor Condensation. All vapors from the plant, whether steam, fatty acids or other lipids, have to be condensed. Usually condensation is done with injected water so that the condensate consists of 8690% water. To save water, the vapors can be precooled by passing through cooled surfaces. Figure 7.62 shows a multistage steam jet vacuum pump. The possibility of condensing the water vapors and the motive steam depends on the coolant (water in most cases) temperature. This means a dependency on ambient temperature and the influence of the seasons. Condensation efficiency may be improved in the following sequence of technical development: surface condensation; direct contact condensation, alkaline loop at normal cooling water temperature 20°C; direct contact condensation, alkaline loop at low cooling water temperature 4 4 ° C ; direct contact condensation, brine loop 20°C; ice condensation <-20°C. If water
Fig. 7.62. Multistage jet vacuum pump system (courtesy of Korting Hannover AG).
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hydroxide solutions added to the circulation fluid, which is cooled by normal cooling water in a plate heat exchanger. The pressure in the condensor is 50-70 hPa. Condensing systems with low cooling water temperature cool the cooling water in refrigerators to about 4 4 ° C . It is then warmed by 3 4 ° C during condensation by the heat of evaporation. The pressure in the condenser then drops to 11-15 hPa. It is even more efficient to condense the vapors at the working pressure of the deodorization column. To achieve that, an even lower temperature is required. An evaporating refrigerant such as liquid ammonia with temperatures below -20°C is needed because condensation occurs between -13 and -2°C. The advantages of such systems include energy savings and lower environmental load. It pays only if emission costs are high. It was said to be impossible to condense deodorization vapors on cold surfaces because they contain emulsions that are very stable. In a patent (Kroll and Schreckenberger 1988) it was proven that these emulsions are stable only in the temperature range from 0 to 45°C and very stable between 7 and 42°C. If this temperature range is avoided during condensation, the water can be separated from the lipids without adding separating agents. To maintain a condensation temperature above 40"C, the vapors have to be compressed above 7.3 hPa. 7.4.6 Comparison of the Processes
All three ways to deodorize oil, namely, batch deodorization, semicontinuous deodorization and the continuous process have their strengths and weaknesses. 7.4.6.1 Batch Processing. The main advantage of the batch process is the very low investment required. This is conveniently combined with an extremely long service life and very low maintenance cost. It is .suitable for processing an everchanging palette of products in different lot sizes and under different process conditions. Any specialty can be run individually. The batches have a comparably low capacity also caused by the long residence time in the vessel. External preheating and cooling help to reduce this time; however, that requires high effort and therefore it is rarely done. The energy consumption of batch deodorizers is unfavorably high, because energy recovery is difficult. The simple design and the possibility for local manufacturing make such plants attractive for countries with restricted infrastructure and little foreign currency available. 7.4.6.2 Semicontinuous Processing. Semicontinuous processing is the choice for deodorization of frequently changing batches of different oils. For best use of the plant, the lot sizes should be equal or a multiple of the tray size of the apparatus. Semicontinuous processing is used mainly to deodorize standard compositions, for example, in or for margarine factories. In principle, the deodorization temperature can be chosen differently for every tray, thus allowing for individual treatment of every batch that passes through the
Oil Purification
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deodorizer. However, this would be a misuse of the system, leading to inadequate utilization and much longer cycle times. Heat recovery is possible at every point in time so that the plant can be run at lower cost than batch plants. Contamination between the different lots passing the trays is very limited. In extreme cases, a tray that must not be contaminated between two batches should be left empty. Usually, such problems can be overcome by careful planning. This means that a less critical oil is processed as a kind of buffer between two sensitive ones. Residence times in the semicontinuous deodorizer are much shorter than in batch processing. It is important to keep the discharge and dripping times short. Because of the construction of the deodorizer as a stack of individual trays that follow the processing cycle sequentially, the effort for control is high but can be easily automated with today’s means.
7.4.6.3 Continuous Processing. Continuous plants are best suited for processing large volumes of one and the same oil. Therefore, they are used mainly in oil mills that also operate a refinery where the same oil is usually processed over a period of weeks before it is changed. The design of the apparatus is much simpler than that of semicontinuous deodorizers. Combined with the fact that there are no individual batches of different oils that have to be kept apart, there is also much less control effort. Because the processing chambers are not separated from each other, the conditions are equal for the passing oil everywhere in the deodorizer. Changing the kind of oil without intermixing is possible only by emptying the entire plant. Therefore, as stated before, it is best used for very long runs of identical oils.
7.5 Physical Refining From a technical point of view, physical refining is nothing else than extending the processing conditions of deodorization to neutralization. Stage (1979 and 1982) and Young (1980) gave the deeper mathematical and theoretical background and reported on the state of the art.
7.5.1 The Theory of Physical Refining Physical refining follows the same principal rules that also hold true for deodorization (see Chapter 7.4.2).Taking into account the vapor pressure of fatty acids (see Chapter 2.3.2.4),it becomes clear that either temperature must be increased or pressure must be decreased to remove them by distillation. Their vapor pressures are significantly lower those that of aldehydes and ketones; however, they also lie significantly above those of triglycerides (fats and oils) as shown in Figure 7.63. Improved means of vacuum generation and improved construction of plants allow the maintenance of pressures <4 hPa, making physical refining feasible. At high pressures, the temperatures required to remove fatty acids would be too high for the product. In addition to deodorization plants, a condensation chamber for the fatty acids becomes necessary.
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Fig. 7.63. Vapor pressure of aldehydes and ketones, fatty acids and their system with
steam. 7.5.2 Requirements on Oils to Be Physically Refined
The relatively high thermal stress combined with a prolonged process time compared with deodorization makes necessary a pretreatment of most oils. Following the traditional route, most of the components that interfere with the processing conditions of deodorization have already been removed in the processing steps leading up to it. Should oils be physically refined without pretreatment, the following difficulties could arise: (i) phosphatides (mainly in soybean oil), which decompose under the processing conditions forming decomposition products which cannot be removed; (ii) gossypol from cottonseed oil which thermally decomposes to black substances; (iii) proteins, which decompose under formation of colored components and form odoriferous and bad-tasting substances, mainly in conjunction with carbohydrates; and (iv) (heavy) metals, which promote oxidation. In addition to these components, which are removed during earlier processing steps in conventional processing, the oil has to be free of oxygen and water. Their presence at physical refining temperatures would lead to oxidation and hydrolysis, respectively, of the mglycerides. However, this is not specific for physical refining but a general danger. Figure 7.64 shows the processing steps that have to be carried out to prepare oils and fats for physical refining. To date, cottonseed oil and fish oil cannot be physically refined because gossypol cannot be removed properly from the cottonseed oil and the highly polyunsaturated fish oil fatty acids would polymerize. Phosphatides should be reduced to c5 ppm (expressed as P). Kheok and Lim (1982) give the following process for oil pretreatment: after hydration of the phosphatides, bleaching earth is added and the mixture is heated to 90-120°C. This
Oil Purification Babasclu oil Coconut oil Palm kernel oil Sunflower oil Palm oil Lard Edible tallow Hardened oilslfats
Peanut oil S e s a m oil
Corn oil Soybean oil Rapeseed oil
Cocoa butter Olive oil Butter oil
I J
J
t
I
697
P<Swm
Degummlng
I Bleaching
I 90.120'C
I
I
I
I
I
-
Bleaching I
Physical mflnim ~~~
~~
i
2-3 hPa
~
Not sultable for fish oil and cottonseed oil
oil (neutralized, bleached, deodorized)
Fig. 7.64. Pretreatment of oils for physical refining
ensures adsorptive removal of colorants and also of metal traces. Most oxidation products decompose and in case they are volatile are removed together with the bleaching earth. The bleaching earth used should be highly efficient because it a190 has to perform that part of the bleaching process that is usually done as a side effect during alkali neutralization:
7.5.3 The Processing Conditions The most important processing parameters in physical refining are pressure and temperature. The lower the vacuum that can be achieved, the lower the temperature can be. Temperatures >270"C must be avoided in any case because the oil would be damaged. During the entire process cycle, the oil reaches a maximum of 60°C during degumming, 110°C during bleaching and 260°C during deodorization. 7.5.4 Plants for Physical Refining
Plants for physical refining are the same as those for deodorization but with a more effective vacuum generation system and with a fatty acid condenser attached. Figure 7.65 shows an apparatus for physical refining. The oil enters the stainless steel column at the upper-left corner after having been degassed and preheated. Stripping steam is blown in under vacuum while the oil passes through tray one with a holding time ensured by horizontal sheets that force a zig-zag flow. Uniform distribution of the live steam is achieved by a microbubble system. Each tray is a combined hold up and stripping tray. Straight
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Fats and Oils Handbook
Fig. 7.65. Physical refining column (courtesy of Krupp Maschinentechnik, Hamburg).
O i l Purification
699
mammoth pumps circulate the oil at least 50 times during tray residence time and at the same time ensure intense contact with the stripping steam. The tray's multichambered design provides a cascade flow. The three distillation trays are constructed almost equally. They appear different in the drawing only because attention is given to different details in each tray. These details are highlighted, the others omitted. The vapor duct is arranged in the center of the column, i.e., in its hottest part, to prevent any undesired distillate condensation; a central chimney provides almost equal vacuum to all trays. All heating of the oil above -90°C is done under vacuum. In the cooling step (tray 4), the vacuum is maintained until a temperature of -140°C is reached while steam is also blown in. Table 7.21 gives the consumption of such an apparatus. 7.5.4.1 Physical Refining in Packed Columns. Analogous to processing in chenucal plants, packed columns can also be used for physical refining. The advantage of such systems is at first that the oils are distributed over a large surface area, which facilitates contact with the steam. Second, the oil layer is very thin, eliminating resistance to the steam, which therefore does not have to be blown through. The steam is blown from the bottom against the flow direction of the oil, which is fed into the upper part and rinses down. In a packed bed deodorizer, the oil is forced to frequently change its direction of flow. Such plants are offered by Tetra Laval, for example, (Fig. 7.66). The manufacturers claim a lower steam consumption and lower cost for vacuum generation compared with traditional physical refining plants. 7.5.4.2 Condensation of Fatty Acids. The vapors leave the deodorizer column at a temperature of 130-140°C and at a pressure of -8 hPa. Additional injected steam compresses them further (vapor scrubber). The temperature remains as it was but pressure increases to -45 hPa. The vapors are condensed with water in an atmospheric condenser (see also Chapter 7.4.5.3). Solidification of the system is prevented by using tempered water.
TABLE 7.21 Consumptions for Physical Refininga Consumption per MT of oil Steam for deodorization (4 bar) for vacuum generation (11 bar) Heating energy (gas, oil, ...) Cooling water for product cooling for vacuum generation Electrical energy Steering air (7 bar)
(kg) (kg) (kl) (m3) (m3) (kwh) (Nm3)
Working pressure 4-7 hPa, deodorization at 24Ck270"C aCourtesy of Lurgi CmbH, Frankfurt.
15-20 7C-125 150,000 2-25 10-16 3 4 3
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fats and Oils Handbook
Fig. 7.66. Drawing of a packed column deodorizer (courtesy of Tetra Laval, Tumba).
7.5.5 Physical Refining of Palm Oil
Physical refining of palm oil does not differ substantially from the physical refining of other oils. However, a heat bleaching step may be integrated. Figures 7.67 and 7.68 show the processing flow chart and a continuous plant, respectively, for physical refining of palm oil. The incoming oil is dried at (A), and a bleaching earth/oil slurry is dosed (B). The slurry then passes through a vessel (C), which is well stirred and guarantees sufficient reaction time. This is needed to ensure complete adsorption. The bleaching earth is then filtered off (D) (here: disk filters) and the oil is cooled (E). In the distillation tray, the oil is dried (F)and countercunently heated (G). The oil then continuously passes through several trays of the deodorizer (H) and is steam treated under vacuum. Then it is cooled and the vapors are condensed (J). Vacuum is raised in (K). Such plants have a capacity of 50-500 todd. For a medium-sized plant of -150 todd, energy consumption and consumption of auxiliary material are given in Table 7.22. Figure 7.69 shows the model photo of such a plant. 7.5.6 Comparison of Chemical and Physical Refining
Today, physical refining seems more attractive than ever before because the major part of the effluent in refineries can be avoided. The water for neutralization with alkali lye (>0.1 m%on of oil) is not needed nor is the effluent from soap splitting
701
O i l Purification
*
Mineral aud
o
Cwling
water
Vacuum t
-
0
Fully refined oil
Fig. 7.67. Plant for physical refining of palm oil (redrawn; courtesy of Lurgi, Frankfurt).
obtained. These considerations play an increasingly important role. In addition to environmental considerations, effluent indirectly also always means cost. For a cost comparison, estimates are given in Table 7.23. One must keep in mind, however, that such comparisons can be only qualitative because the real costs always vary greatly, depending on the plants that are compared. By comparing the costs of the two processes, the break-even point can be calculated. Below this point, chemical refining is less costly and above it, physical refining. This break-even point also includes the FFA content of the oil. Opinions about this break-even point differ considerably. Tirtiaux gives a range of 0.4-0.7 FFA. This means that below 0.4%,the chemical process is less costly and above 0.7%,the physical refining process. Other authors see this limit at an FFA of 1%. These purely com-
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702
-1wc 25&280'C 250-260'C, 5-8 Wn, -2 h
Fig. 7.68. Flow chart of palm oil physical refining.
Fully refined palm oil
mercial figures can be overmled, of course, by other motives such as environmental care. These motives may also derive from the philosophy of the company.
7.6. Energy Consumption and Investment Neumunz (1987) gave the investment costs for a turnkey refinery of relatively small size. Plants of that size may be suitable for small countries. The complete TABLE 7.22
Consumptions for Physical Refining of Palm Oila (Plant with a capacity of 150 Mud) Steam for deodorization (4 bar) for vacuum generation (1 1 bar) Heating energy (gas, oil, ...) Cooling water for product cooling for vacuum generation Electrical energy Steering air (7 bar)
Consumption per MT of oil (kg) (kg) (kl) (m3)
(m3)
(kWh) (Nm3)
20-30 70-1 00 2-3 2 16 3 3
Oil entry at 8 0 T , leaving at 50°C; working pressure 6 hPa; deodorization temperature 260°C aCourtesyof Lurgi CmbH, Frankfurt.
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Fig. 7.69. Model photo of a plant for physical refining of palm oil (courtesy of Lurgi, Frankfurt).
plant encompasses the processing steps of neutralization, bleaching and deodorization. The plant is designed for a capacity of 2 M T h and requires an investment of -4 million U.S. $, which includes an oil bottling plant. It must be stated that semicontinuous deodorizers (for example, the Lurgi plant) have many times this capacity with a throughput of more than 20 to&. Investment cost for such plants cannot
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TABLE 7.23 Comparison of Chemical and Physical Refininga
Energy consumption Steam for deodorization Electrical energy Heating energy Process chemicals Phosphoric acid Alkali hydroxide Bleaching agent Sulfuric acid Chemicals for effluent treatment Processing Neutral oil in fatty acid Oil in bleaching agent Hot washing Maintenance cost Personnel cost
+ = higher, - = lower,
Chemical
Physical
(+I
(-j
+ -
(+I needed
-
+ (4 not needed
-
+
needed needed
not needed not needed
+ -
+
needed
not needed
(+I
(-I
+
-
-
( j = equal or with a tendency only.
aSource:Tirtiaux
be compared with the plant described by Neumunz. An indication may be given, however, by the cost per ton of oil, which must be lower in the case of a larger plant. For the plant Neumunz describes, he gives U.S. $75.30/ton (1987 prices), part of which is broken down as follows: caustic soda bleaching earth filter aid chemicals water energy labor
2.00 12.00 2.00 1.oo 1.70 2 1.90 28.00
As stated, these are costs of the late 1980s and are based on the figures given in Table 7.24 for the consumption.
7.7 The Importance of Refining for the Removal of Environmental Contaminants The different steps of refining contribute considerably to the purification of the oil from environmental contaminants. As in all other agricultural products, oilseeds and oil fruit also contain various such components. A part of them is carried from the seed to the oil. Such components include pesticides, fungicides and herbicides,
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TABLE 7.24
Utilities per MT for a Very Small Vegetable Oil Refinerya Water 30°C im3)
Neutralizing (caustic soda) Bleaching (batch) Deodorization (batch) Oil bottling Auxiliary equipment Total
5 3.5 18 0 0
26.5
Fuel energy (MJ)
18 28 115
2.5 0 163.5
Compressed air (m3)
Electrical energy (kWh)
0 2.5 0.5 0 0 3.0
10 6 4 4 11 35
Plant capacity -50 MT/d of crude vegetable oil ~
aSource:Neumunz (1987).
polycyclic hydrocarbons, polychlorinated cyclical hydrocarbons, trace metals and others, which are ubiquitous in today’s environment. Although ubiquitous and present in quantities that do not endanger the consumer, in principle, they should not be present in food and have to be removed if technically possible. In any case, they have to be reduced to the technologically feasible minimum. This is a claim that must be valid, of course, for all food, although total removal cannot always be reached. The possibilities to achieve this goal, however, are increasing (see, for example, Ocker and Briiggemann 1988). Total freedom from such components will most likely remain an elusive goal; however, that does not mean that there should not be ongoing attempts to reach it. The different refining steps offer good opportunities (see, for example, Billek 1982 and 1985). It has to be stressed that especially foods that are regarded as particularly natural, usually do not pass through all of these refining or purification steps. This is the case for cold-pressed oil and butter, for example. Such products sometimes exceed the limits (see Pfannhauser et al. 1980). Refining comprises several processing steps that each contribute to the purification of the oil. During degumming, contaminants are carried along with the gums; during neutralization, they are precipitated together with the soap; during bleaching, they are adsorbed, especially by active carbon and are removed with the bleaching agent as well as separated during deodorization. Several investigations for different groups of contaminants exist. These investigations reflect their behavior during refining. In the following, the effects of such groups of undesired components will be discussed in some detail. These remain only examples that are representative for a number of similar results. In addition to the slight contamination of crude oils with environmental contaminants, food that contains high amounts of fat can also be contaminated with chemicals that come, for example, from dry cleaning premises that are situated too close to supermarkets and emit high amounts of cleaning solvents (usually perchloroethylene PCE). Such contamination cannot be influenced, of course, by the producers nor by the choice of the raw materials or improvement of the processes because they do not influence postpro-
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706
duction processes. This kind of contamination has to be avoided by other measures. In 1988 in Europe, some cases of Contamination of high fat content food with PCE were reported, which led to increased attention of the public. The amounts found in food exceeded the limits in single cases; however, they never constituted a health hazard. Vieths et al. (1988 and 1989) carried out some trials, artificially exposing food to PCE vapor to collect data for preventive measures. 7.7.1 A f7a toxins
Aflatoxins are metabolic products of molds (see also Chapter 4.3.4.3) that are formed under specific ambient conditions. Usually they are caused by poor storage; in oilseeds, they are found mainly in peanuts. It is very difficult to remove aflatoxins from food because they are difficult to separate nor can they be destroyed easily because of their considerable heat stability. However, even if the beans are infected, aflatoxins are present in the oil only in very small quantities because they are relatively insoluble in the oil. During neutralization with caustic soda, 90-98% of the aflatoxins is already decomposing as the lactone-bond is broken (Prevot 1985, Fig. 7.70). The residual 2% of the initial amount is almost completely removed during bleaching. This is achieved even if their concentration is especially high. Therefore, aflatoxins are not found in refined oils and occur only in unrefined oils. Basappa and Sreenivasa Murthy (1979) proposed their removal
Aflatoxin [ppb] ction limit 50 ppb) ......................
-----
nonactivated
.......................
- activated .....................
. . ..
................................
*--.
0
0.2
0.4
I
I
0.6
0.8
Amount of earth
-*-*
1.0
[%I
Fig. 7.70. Reduction of aflatoxin during vegetable oil refining, depending on the amount of bleaching earth applied (after Prevot 1985).
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via special filtration techniques that are not yet applied because normal refining sufficiently reduces the amounts. 7.7.2 Polycyclic Aromatic Hydrocarbons (PAH)
In all investigations, the concentration of polycyclic aromatic hydrocarbons (PAH) was found to be c 2 pgkg. It is assumed that coconut oil becomes contaminated during drying of copra over an open fire (burning the hulls and the fibrous material). But contamination with soil as well (soybeans and peanuts) may be a reason. In all other oils, PAH concentration is many times lower. Figure 7.71 shows the reduction of different PAH levels in vegetable oil during neutralization, bleaching and in fully refined oil. If active carbon is added during bleaching, the amount can be reduced substantially. During deodorization, the removal of PAH,among others, is dependent on the temperature. At 180°C,a remarkable reduction is achieved after only several hours; at temperatures that are commonly applied, they are almost completely removed (Fig. 7.72). In addition to temperature, deodorization time also plays a role. Depending on the component, their reduction can be very rapid or may require some time (Fig. 7.73). For oils that contain higher amounts, active carbon is added in some cases during the bleaching process. Active carbon is able to remove mainly the heavy PAH, whereas the light PAH are removed during deodorization.
7:
1200
Sunflower seed oil
Coconut oll lo00 -
z
B
8oo-
800
00
.
800
soo-
400
d
c
.o r
B
.200
0 rNeutralized
-0
Bbached
DeOdOrhOd
A = Phenanthrene C = Pyrene E = 3,4-Benzpyrene, l12-Bempymne
rude
Fully reflned
B = Anthrscene D = 1,?-Benzanthrene F = Anthranthrene, Coronene -
\
Fats and Oils Handbook
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[
Type of polycyclic hydrocarbon in sunflower seed oil
1
Fig. 7.72. Removal of polycyclic hydrocarbons during deodorization of sunflower oil depending on the temperature (after Biernoth and Rost 1968).
I
Tvw of Dolvcvclic hvdrocarbon in coconut oil
I
Fig. 7.73. Removal of polycyclic hydrocarbons during deodorization of coconut oil depending on the time (after Biernoth and Rost 1968).
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7.7.3 Chlorinated Polycyclic Hydrocarbons and Pesticides
In France, for example, 300 different approved substances of this class are registered, including -170 herbicides, 100 fungicides and 30 insecticides. This can be seen as representative for Europe. Currently, the detection limit of these components is -5 ppb. Many of these components decompose very quickly, whereas others have a longer lifetime and can be found in crude oils and fats. In the countries of origin of some crude oils, more substances are often legal than in the countries of their destination. In general, the number and the amount of pesticides have been significantly reduced since the 1970s because they are less used now. Figures 7.74 and 7.75 show the removal of pesticides during refining and during deodorization. If the process is carried out at the appropriate temperature and pressure, >90% of these components may be removed (see, for example, Thomas 1982, Uhnak et al. 1983 and Bednarek-Karbul et al. 1980). For pesticides. the same basic rules are valid as for all other substances that are removed during deodorization. This means that the temperature is much more important than the deodorization time. At common deodorization temperatures, most pesticides are reduced to levels below their detection limits, the others to some percentage of their initial value. Hardening also contributes to the removal of PCB. During this modification step, 50-95% of the PCB are destroyed. The amount of PCB that is removed from the fat was found to increase with the degree of hardening. Most likely, the reason for that is that PCB are hydrogenated, thereby becoming more volatile; they are then removed as
Fig. 7.74. Removal of pesticides from cottonseed oil during refining (after Gooding 1966).
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Fats and Oils Handbook
Fig. 7.75. Influence of the deodorization temperature on the removal of pesticides from soybean oil (after Brarnmer 1973).
substances that evaporate easily. They could not be found on the surface of the catalyst after filtration. In the late 1970s (Kroll 1977), many German food products that contained fat or were fat products were screened; none of them contained representatives of that class of components above the legal limit. Addison (1983) reported on the removal of PCB from marine oils. 7.7.4 Trace Metals
Trace metals are very carefully removed because they promote oxidation, thus negatively influencing the oil quality. During degumming, some of them are carried out together with the precipitating gums (Shaw 1983). The same holds true for the soaps that are formed during neutralization. The trace metals are carried into the aqueous soap solution. The addition of citric acid allows them to be bound as a complex so that they can be washed out with the washing water. In chemical refining, many trace metals form hydroxides, which precipitate during neutralization (Fig. 7.76). Some of these even precipitate in neutral or acidic environments and are thus already removed during degumming. The hydroxides are removed together with phosphatides and also with the soaps. Otherwise, they are adsorbed by the bleaching earth. Figure 7.77 shows some reduction rates for metals during conventional refining of fats and oils. The initial amounts are not given in absolute values but as relative figures because the load with trace metals can differ greatly,
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Fig. 7.76. pH of metal hydroxide formation and precipitation.
depending on the origin of the oil and on the individual batch. An overview was given by Thomas (1975). Rakmi et al. (1984) described the removal of heavy metals especially from palm oil. The situation here differs very much from that of the other oils because palm oil is predominantly physically refined. However, refining provides a drastic reduction of metals here as well.
Fig. 7.77. Reduction rates of heavy metals in oils and fats during refining.
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7.8. References Addison, R.F., (1983) Organochlorine Compounds and Marine Lipids, Prog. Lipid Res. 21, 47-7 1. Alfa Laval, Alfa Laval AB, Tumba, Sweden. Alfa Laval, Degumming and Neutralizing Methods for Vegetable and Animal Oils and Fats, Technical Information PB 40981E2. Alfa Laval, Oil Refining Separator SRPX, Technical Information. Alfa Laval, (1987) New Developments in the Deodorizing Process, Proc. Am. Oil Chem. Soc. Conf. AMA, AMA Filter b.b. Alkmaar, Netherlands, Technical Information. AMA, Speiseol-Filtration. A M A (1986) General Information, Niagara Filtersfor the Oil and Fats Industq, F. Ten Hage. Athanassiadis, A., (1978a) Refining and Segregation of Palm Oil, Proc. Am. Oil Chem. SOC. Congress, St. Louis. Athanassiadis, A,, (1978b) Refining and Segregation of Palm Oil, Proc. Am. Oil Chem. Soc. Congress, St. Louis, May 1978. Athanassiadis, A., (1988) The Deacidification of Vegetable Oils by Distillation During Deodorization; Fat Sci. Technol. 90,522-526. Athanassiadis, A., (1980) Considerations on Energy Saving in Vegetable Oil Refining; Proc. ISFAm. Oil Chem. Soc. Congress, New York, April 1980. Athanassiadis, A., Technical Information of de Smet, 1988. Athanassiadis, A., (1989) Refining of Palm Oil, Proc. Int. Con$ NIFOR, Benin City, Nigeria, November 1989. Athanassiadis, A., (1990) Considerations on DegummingPretreatment in Refining, Proc. 45th Ann. Conv. OTA, New Dehli, February 1990. Athanassiadis, A., (1991) Features of the de Smet Deodorizing System, Fat Sci. Technnl. 93, 144-150. Badings, H.T., (1973) Fishy Off-Flavors in Autoxidized Oils, J. Am. Oil Chem Soc. 50, 334. Bailey, A.O., (1941) Steam Deodorization of Edible Fats and Oils, Ind. Eng. Chem. 33,404. Bailey, A.O., (1951) Industrial Oil and Fats, Interscience Publishers, New York. Bardies, MoutiC, Decoudun, French Patent 15394 (1855). Basappa, S.C., and Sreenivasa Murthy, V., (1979) Decontamination of Groundnut Oil from Aflatoxin by Adsorption-Cum-Fitration, Ind. J. Technol. 17,440-441. Bednarek-Karbul, W., Lipowska, T., and Kubacki, S.J., (1980) The Influence of Technical Processes on the Content of Organochloric Pesticides in Vegetable Oils, Przemysl s p o ~ w c z y3 4 , 3 1. Bengen, F., and Schlenk, W., Deutsches Patent 12 438 (1940); Experentia 5, 200 (1949). Berg, T.G.O., and Ohlsson, A., citation from Brimberg (1982). Bergmann, L.O., and Johnsson, A., (1964) Eine neue Raffinationsmethode fiir Speiseole und Speisefette - Das Zenith-Verfahren, Fette Seifen Anstrichmittel 66, 203-206. Bernardini, E., (1985) Oilseeds, Oils and Fats, Publishing House BEOil, Rome. Bhattacharyya, S., Bhattacharyya, D.H., Chakraborty, A.R., and Sengupta, R., (1989) Enzymatic Deacidification of Vegetable Oils, Fat Sci. Technol. 91,27-30. Biernoth, G., and Rost, H.E., (1968a) Occurrence of Polycyclic, Aromatic Hydrocarbons in Edible Oils and Their Removal, Arch. H y g . Bakt. 152,238-250. Biernoth, G., and Rost, H.E., (1968b) Removal of Polycyclic Aromatic Hydrocarbons from Edible Oils, Proc. ISF IX Congress, Rotterdam.
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Biemoth, G., and Rost, H.E., (1968~)Qualitative and Quantitative Determination of Polycyclic Aromatic Hydrocarbons in Fats and Oils, Proc. ISF IX Congress, Rotterdam. Billek, G., (1982) Einfluss technologischer Verfahren auf Fette, Fette, Seifen, Anstrichmitrel 2 (Suppl.), 575. Billek, G., (1985) Einfluss der industriellen Verarbeitung und der haushaltsmassigen Zubereitung auf die Nahrungsfette, Bibliotheka Nutritio et Dieta 34, 82-85. Braa, B., (1976) Degumming and Refining Practices in Europe, J. Am. Oil Chem. SOC.53, 353-357. Brammer, K.R., (1973) Industrielle Verarbeitung von Speisefetten im Lichte von Umweltfragen, Fette, Seifen, Anstrichmittel 75, 252-256. Brdicka, R., (1973) Grundhgen der physikalischen Chemie, VEB Verlag der Wissenschaften, Berlin. Brekke, O.L., (1980) Deodorization, in Handbook ofsoy-Processing and Utilisation, p. 168. Brimberg, U.I., (1981) Untersuchungen uber die Kinetik des Bleichens mit Bleicherden, Fette, Seifen, Anstrichmittel 83, 184. Brimberg, U.I., (1982) Kinetics of Bleaching Vegetable Oils, J. Am. Oil Chem SOC.59,74. Brunner, K.-H., (1984)Neue Verfahrensentwicklungen auf dem Gebiet der Speiseijlraffination mit Zentrifugalseparatoren,Fette, Seifen, Anstrichmittel 86,529-537. Cassgrand, (1854) Chemical Gazette 1854, no. 283, quoted from DGF, (1981) Fette, Seifen, Anstrichmittel 83, 89. Cavanagh, G.C., (1976) Miscella Refining, J. Am. Oil Chem. SOC.53, 361-363. Cavanagh, G.C., (19%) Neutralization 11. Theory and Practice of Non-Conventional Caustic Refining and by the Zenith Process, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 101-106, American Oil Chemists’ Society, Champaign, IL. Chang, S.S., Krishnamurty, R.G., and Reddy, B.R.,( 1967) The Relationship Between AlkylFurans and the Reversion of Soybean Oil, J. Am. Oil Chem SOC.44, 159. Cowan, J.C., (1976) Degumming, Refining, Bleaching, and Deodorization Theory, J. Am. Oil Chem. SOC.53,344-346. DFG, Fremdstoffkommission, Mitteilung 111, Beschluss 2 und 3 vom 1.1 1.1967. DFG, Fremdstoffkommission 21, Beschluss vom 30.1 1.1973. DGF Gemeinschaftsarbeit, Die Dampfung von Speisefetten und -olen zur Desodorierung und Entsauerung, Part I, Fette, Seifen, Anstrichmittel 83, 89-97 (1981); Part 11, 90, 207-210, (1988); Part 111, 91,7-14 (1989); Part IV, 91, 253-260 (1989); Part V, 91,452-456, (1989). DGF Gemeinschaftsarbeit, Die Bleichung von Speisefetten und -olen, Fefte, Seifen, Anstrichmittel, Part I, Fat Sci. Technol. 95, 123-126 (1993); Part 11, Fat Sci. Technol. 95, 321-325 (1993); Part III, Fat Sci. Technol. 97, 177-182 (1995); Part IV, FettLipid 9 8 , 9 4 1 0 3 (1996). Duff, A.J., (1976) Automation in Vegetable Refineries, J. Am. Oil Chem SOC.53,377-381. Dupjohann, J., and Hemfort, H., (1975) Verfahren zur Verarbeitung von tierischen Rohfetten unter besonderer Beriicksichtigung zentrifugaler KlL- und Trennvorgange, Fette Seifen Anstrichmittel 77, 81-93. Eder, S.R., (1982) ijber die Bildung von Artefakten bei der DPmpfung von Speiseolen und fetten; Fette, Seifen, Anstrichmittel 84, 136-141. Eichner, K., (1986) Chemische Vertinderungen von Lebensmitteln bei der Verarbeitung und Lagerung, Lebensmittelchem. Gerichtl.Chem. 40, 75-83.
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Eicke, H., Fette, Seifen, Anstrichmittel, Der gegenwartige Stand der Bleichung im Raffinationsprozess pflanzlicher o l e und tierischer Fette. Esser, U, Mrotzek, D, and Steiner, K.H., (1985) Filterapparate, Chem. Ing. Technol. 57, 1035-1 045. EX-Technik, Extraktionstechnik, Gesellschaft fur den An lagenbau GmbH, Technische Information. EX-Technik, Edible Oils and Fats Processing, Technical Information. EX-Technik, Ole und Fette kontinuierlich bleichen, Technische Information. EX-Technik, (1967) Ve8ahrenstechnische Probleme der kontinuierlichen Bleichung, W. Kehse, DGF-Tagung. EX-Technik, Abwasserreinhaltung und Venvertung von Desodorierdestillaten, W. Kehse. EX-Technik, Verschiedene Moglichkeiten der Warmeriickgewinnung bei Semi-kontinuierlichen Desodoriseuren, K. Weber. EX-Technik, (1980) Kontinuierliche Extraktion olhaltiger Bleicherdekuchen, K. Weber, Vortrag DGF-Tagung, Gel. Freundlich, H., Kapillarchemie, Vol. I/II, Leipzig, 1930/32. Fundabac, Dr.Miiller AG. Mhnedorf, Schweiz, Fundabac-Filter, Technical Information. Funda, Former Chemap AG, Mannedorf, Schweiz, Funda The Filter, Technical Information. Gander K.F., (1969) Personal Communication. Gehring, H., (1980) Dampfstrahl-Vakuumpumpen zur Vakuumerzeugung in der SpeiseolIndustrie, speech during DGF annual convention, Kiel, 8. Sept. 1980. Gosele, W., (1987) Entwicklungstendenzen in der Filtertechnik, Chem. Ing. Technol. 59, A494-500. Gooding, C.M.B., (1966) Fate of Chlorinated Organic Pesticide Residues in the Production of Edible Vegetable Oils, Chem. Ind., 344. Grosch W., (1987) Enzymatische Bildung von Aromastoffen aus Lipiden, Lebensminelchem. Gerichtl. Chem 4 1 , 4 0 4 6 . Hage, F. ten, (1986) General Information, Niagara Filters for the Oil and Fat Industry; Amafilter b.v., Alkmaar, Holland. Haraldsson, G., (1972) Verhiitung von Wasserverunreinigung in Fett- und Olraffinerien. speech during Unilever Symposium, Rotterdam. Haraldsson, G., (1983) Recent Development in the Refining of Fany Oils, Information der Fa. Alfa Laval. Haraldsson, G., (1983) Degumming, Dewaxing, Refining, J. Am. Oil Chem Soc.60,251-256. Haraldsson, G., (1985) Energy Considerations, J. Am. Oil Chem. SOC.62,310-316. Haslbeck, F., Wieser, H., Stempfl, W., and Grosch, W., (1986)Untersuchungen zum lipolytischen Fettverderb 11: Gexuch und Geschmack von Fettsauren in S h e und Kokosfett, Z. Lebensm. Unters. Forsch.l83,93-96. Hefter, G., (1906) Technologie der Ole und Fette, Springer Verlag, Berlin. Hendrix, B., (1990) Neutralization I. Theory and Practice of Conventional Caustic (NaOH) Refining, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 94-100, American Oil Chemists’ Society, Champaign, IL. Hexnnann, (1988) Trials of Krupp. Hill, F.D., and Hammond, E.G., (1965) Studies on the Flavor of Autoxidized Soybean Oil, J. Am. Oil Chem. SOC.42, 1148-1150.
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Hofehann, K., and Steiner, R., (1993) Extraktive Raffination von Rapsol mit iiberlaitischen Ltisungsmitteln, Chem I g . Technol. 65, 1510-1514. Hoffmann, G., (1961) 3-cis-Hexanal, the ‘Green’ Reversion Flavor of Soybean Oil, J. Am. Oil Chem. SOC.38, 1-3. Hoffmann, G., (1961) Isolation of Two Pairs of Isomeric 2,4-Alkadiens from Soybean Oil Reversion Flavor Concentrate, J. Am. Oil Chem SOC.38,3 1-32. Hoffmann Y., (1973) Experiences in Refining Rapeseed Oil by the Zenith Process, J. Am. Oil Chem. Soc. 50,260A-264A. Hoffmann Y., (1974) Le ProcCdC Zenith et le Raffinage de 1’Huile de Palme, Ole‘agindu 29, 259-262. Imai, C., Watanabe, H., and Haga, I.T., (1974) Detection of Heat Transfer Media in Edible Oils, J. Am. Oil Chem Soc. 51,495. Kerr, P.F., (1932) Montmorillonite or smectite as constituents of Fuller’s earth and bentonite, Am. Mineralogist 17, 192-198. Kheok, S.C.,and Lim, E.E., (1982) Mechanism of Palm Oil Bleaching by Montmorillonite Clay Activated at Various Acid Concentrations, J. Am. Oil Chem SOC.59, 129-131. Kirchfeld, Franz Kirchfeld GmbH, Diisseldorf, Technical Information. Kirchfeld, Entwicklung der Raffinationstechnik, vom Chargen-Verfahren zum Non Caustic/ Deotest System. Kirchfeld, Edible Oil Refining Equipment. Korting AG, Hannover, Technical Information. Korting AG, Dampfstrahlverdichter und Vakuumpumpen. Korting AG, Dampfstrahl-Vakuumpumpen. Korting AG, Arbeitsblatter fiir die Strahlpumpen-Anwendung und die Vakuumtechnik. Kroll, S., (1977) Vorkommen und Kontaminanten in pflanzlichen Olen und Fetten und Moglichkeiten ihrer Entfernung, Lebensm. u. gerichtl. Chemie 31,68. Kroll, S., and Schreckenberger, H., Oberflachenkondensation von Briidenfetten, DB Patent 29 38 805 (1988). Krupp, Krupp Industrietechnik GmbH, Hamburg. Krupp, Kontinuierliche Desodorieraniagen fiir Ole und Fette. Krupp, Semikontinuierlich arbeitende Desodorieranlagen f i r Ole und Fette. Kuroda, Z., and Young, C., (1989) An Edible Oil Deodorizer with a Direct-Fired Heater, J. Am. Oil Chem. Soc. 66, 1781. Lang, K., Henschel, J., Kieckebusch, W., and Griem, W., (1966) Untersuchung iiber die Vertraglichkeit von thennisch behandelten Palmelen an Ratten, Z. Emiihnmgswiss. 7 . 109-127. Loft, S., (1990) Deodorization-Theory and Practice, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 117-123, American Oil Chemists’ Society, Champaign, IL. Loncin, M., in Palmoil-A Major Tropical Product, Congopalm, Kinshasa, October 1970. Liide, R., (1962) Die Rafination von Fetten und Olen, Theodor Steinkopff Verlag, Leipzig. Lurgi, Umwelt und Chemotechnik GmbH, Bereich Thermische Verfahrenstechnik, Frankfurt Lurgi, Physikalische Raflnation von Palmol, Technische Information T 1200111.81. Lurgi, Desodorierung von &en und Fetten, Technische Information T 107M.82. Lurgi, Speiseol u. Speisefett-Raflnation,Technische Information T 14251482. Mag, T., (1990) Bleaching-Theory and Practice, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 107-1 10, American Oil Chemists’ Society, Champaign, IL.
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Marcelet H., (1936) Study on Products Which Give to Vegetable Oils Their Characteristic Taste and Odor; the Presence of Saturated and Nonsaturated Hydrocarbons (in Olive and Peanut Oil), J. Pharm. Chim. 24,213. Marcelet, H., (1936) CR Acad. Sci. 202, 867, quoted from DGF, see above. Markley, K.S., (1961) Soybean and Soybean Products, vol. 11, Interscience Publishers, New York. Mattil, K.F., (1964) Deodorization, in Bailey’s Industrial Oil and Fat Products, 3rd ed., p. 897, John Wiley & Sons, New York. McCabe, W.L., and Smith, J.C., (1956) Unit Operations of Chemical Engineering, McGraw Hill, New York. Meijboom, P.W., and Stroink, J.B.A., (1972) 2-trans, 4-cis, 7-cis-Decatrienal, the Fishy Off-Flavor Occurring in Strongly Autoxidized Oils Containing Linolenic Acid or w-3, 6 ,9, etc. Fatty Acids, J. Am. Oil Chem SOC.49, 555-558. Morgan, D.A., Shaw, D.B., Sidebottom, M.J., Soon, T.C., and Taylor, R.S., (1985) The Function of Bleching Earth in the Processing of Palm, Palm Kernel and Coconut Oils, J. Am. Oil Chem. SOC.62,292-299. Neumunz, G.M., (1987) Vegetable Oil Refinery, in Food Factories, (Bartholomai, A,, ed.), ch. 35, Verlag Chemie, Weinheim. Norris, F.A.. (1982) Refining and Bleaching, in Bailey’s Industrial Oil and Fats Products, (Swern, D., ed.) John Wiley & Sons, New York. Nutting, P.G., (1933) U.S. Geol. Sur. Circ. 3, 11, 17, 20, quoted from Norris, F.A., Refining and Bleaching, in Bailey’s Industrial Oil and Fats Products, (Swern, D., ed.) John Wiley & Sons, New York. Ocker, H.D., and Brtiggemann, J., (1988) Technologische Moglichkeiten zur Verminderung der Schadstoffbelastung in Grundnahrungsmitteln, Lebensmitteltechnik, 230. Pardun, H., (1979) Die Entsauerung von Pflanzenolen mit Ammoniak - Eine umweltfreundliche Raffinationsmethode, Fette, Seifen Anstriclzm. 81, 297-302. Patterson, H.B.W., (1976) Bleaching Practices in Europe, J. Am. Oil Chem SOC.53, 339-341. Pfannhauser, W., Scheidl, I . , and Woidich, H., (1980) Untersuchungen uber den Pestizidgehalt in Nahrungsfetten und -olen, Fette, Seifen, Anstrichmittel 82, 232. Prevot, A,, (1985) Contaminants ‘a I’Etat de Trace dans les Corps Gras, Rev. Fr. Corps Grus 19. Prevot, A,, Perrin, J.L., Laclaverie, G., Auge, Ph., and Coustille, J.L., (1990) A New Variety of Low-Linolenic Rapeseed Oil; Characteristics and Room-Odor Tests, J. Am. Oil Chem. SOC. 67, 161-164. Rakmi, A.R., Kalm, M., and Wan Hor, W.M., (1984) Reduction of Palm Oil Heavy Metal Content in the Refining Process, PORIM Bull. 9, 16-21. Rigamonti, R., and Riccio, V., (1952) Trennung von Fettsauren und Triglyceriden mit Hilfe der Hamstoff- Additionsverbindungen, Fette, Seifen, Anstrichmittel, 193-1 97. Rigamonti, R., and Riccio, V., (1953) Uber die Anwendung von Hamstoff-Additionsprodukten auf dem Gebiet der Ole und Fette, Fette, Seifen, Anstrichmittel, 162-165. Rudischer, S., (1959) Fuchbuch der Margarineindustrie, p. 176, Fachbuchverlag, Leipzig. Schlinck & Co., Deutsche Patente 315 222 and 334 659 (1921). Seals, R.G., and Hammond, E.G., (1966) Diacetyl as the Buttery Flavor Component in Soybean Oil, J. Am. Oil Chem SOC.43,401-403. Seals, R.G., and Hammond, E.G., (1970) Some Carbonyl Flavor Compounds of Oxidized Soybean and Linseed Oil, J. Am. Oil Chem SOC.47,278-280.
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Segers, J., and van de Sande, R., (1990) Degumming-Theory and Practice, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.),pp. 88-93, American Oil Chemists’ Society, Champaign, Shaw, D.B., and Tribe, G.K., (1983) Palm Oil Research Institute of Malaysia Symposium, 115. Sidiqui, and Hasnuddin, M. K., (1968) Bleaching Earths, Pergamon Press, New York. Sjoberg, P., New Developments in the Deodorization Process, Proc. Am. Oil Chem. Soc. Con$, May 1987. de Smet, Extraction de Smet SA, Edegem, Belgien. de Smet, Pretreatment + Bleaching, Technical Information. de Smet, Continuous Bleaching, Technical Information. de Smet, Continuous Deodorization, Technical Information. de Smet, Oil and Fat Deodorizing, Technical Information. de Smet, Production of Fractionated Fatty Matters and Their Uses, Kokken J., Fa. de Smet, Proc. Association Francaise pour 1’Etude des Corps Gras, Technical Information de Smet, Features of the de Smet Deodorizing System, Athanassiadis, A,, Technical Information. de Smet, Die de Smet Raflnationsverfahrenfur Fette und Ole. Smouse, T.H., and Chang, S.S., (1967) A Systematic Characterization of the Reversion of Soybean Oil, J. Am. Oil Chem. SOC.44,509-514. Stage, H., (1979) Heutiger Entwicklungsstand der Anlagen zur physikalischen Raftination pflanzlicher, Ole, Seifen, Ole, Fette Wachse 105, 395-401. Stage, H., (1982) Moglichkeiten des Umweltschutzes bei der physikalischen Raffination und Fettsauredestillation, Fette, Seifen, Anstrichmittel 84, 333-338. Stenberg, O., and Sjoberg, P., (1996) Thin-Film Deodorization of Edible Oils, INFORM 7, 1296-1 304. Siidchemie AG, Miinchen, Technical Information. Siidchemie AG, Miinchen, Tonsil, hochaktive Bleicherden Siidchemie AG, Miinchen, Bleaching, An Optimization, Zschau,W., Proc. Am. Oil Chem. SOC.Conf., New Orleans, 1987. Swern, D., (1964) Bailey’s Industrial Oil and Fat Products, Interscience Publishers, New York. Szabo Sarkadi, D., (1958) Laboratory Deodorizer with a Vaporization Efficiency Unit, J. Am. Oil Chem Soc. 35,472-475. Thomas, A., Der Einfluss der Raffination auf die Konzentration von Spurenmetallen in Olen und Fetten, Proc. DGF-Tagung, Hamburg, October 1975. Thomas, A., (1982) Uber die Entfernung von Schadstoffen bei der Dampfung von Speiseolen und -fetten, Fette, Seifen, Anstrichmittel 84, 133-1 36. Thomas, A., and Lau, J., (1988) Olgewinnung und Olveredelung, Fortschrittsglauben Fortschrittswirklichkeit,Fat Sci. Technol. 90,564-567. Tirtiaux Fractionnement S.A., Technische Informationsschrift, Fleurus, Belgium. Tirtiaux Fractionnement S.A., (1987) The Tirtiaux Physical Refining Process. Tirtiaux Fractionnement S.A., Modular Physical Refining Plants. Tirtiaux Fractionnement S.A., Fractionation Process. Tollenaar, F.D., and Hockmann, H., (1964) Die Bleichung von Olen und Fetten mittels Bleicherden mit besonderer Beriicksichtigung von Palmol, Fette, Seifen, Anstrichmittel 66,430438.
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Tonsil, see Siid-Chemie. Uhnak, J., Veningerova, M., and Horvatova, I., (1983) Chlorinated Pesticides Residues in the Production of Edible Oils, Lebensmittelwissenschaji u. Technologie 16, 323. Vieths, S., Blaas, W., Fischer, M., Klee, T., Krause, C., Matissek, R., Ullrich, D., and Weber, R., (1988) Modellversuche zum Ubergang von Tetrachlorethen aus der Raumluft in Lebensmittel, Deutsche Lebensmittel-Rundschu 84,381-388. Vieths, S., Blaas, W., Fischer, M., Klee ,T., Krause, C., Matissek, R., Ullrich, D., and Weber, R., (1989) Belastung von Lebensmitteln mit Tetrachlorethen im Emissionsbereich Chemischer Reinigungen, Lebensrnittelchem.Gerichtl. Chern.43,107-108. Weber, K., (1980) Kontinuierliche Extraktion olhaltiger Bleicherdekuchen, Proc. Tagung der DGF, Kiel. Westfalia Separator AG, Oelde, Technische Informationen. Westfalia Separator AG, Separatoren mit selbstentleerender Trommelfiir die Industrie. Westfalia Separator AG, Dekanter. Westfalia Separator AG, Kontinuierliche Neutralisationslinie fur Speiseole und Ifette. Westfalia Separator AG, Kontinuierliche Neutralisationsanlage OER. Westfalia Separator AG, Kontinuierliche Neutralisationsanlage OERS 3T. Westfalia Separator AG, Kontinuierliche Wasserentschleirnungsanlage OE IT. Westfalia Separator AG, Maschinen fir die Mechanische Trenntechnik. Westfalia Separator AG, Spezial- Trenn-Separatoren. Young, F., (1990) Physical Refining, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 124-135, American Oil Chemists’ Society, Champaign, IL. Young, V., (1978) Processing of Oils and Fats, Chem. Znd., 692. Zehnder, C.T., (1976) Deodorization 1975, J. Am. Oil Chem. SOC.53,364-369. Zschau, W., (1985) Was ist Bleicherde? Fette, Seifen, Anstrichmittel 87, 506.
Chapter 8
Fat as or in Food Chapter 1.2 presents a compilation of the fat content of different foods or food source materials. Apart from pure oils and fats, emulsion fats such as margarine, butter and mayonnaise have the highest fat content. However, high amounts of fat can also be found in cheese and sausages, for example, and a significant amount of fat is also found in chocolate. The issue of the physiological value of visible and invisible fats and the role that these play in nutrition are discussed elsewhere in this book (Chapter 1.4). Traditionally, butter making is seen as part of dairy technology. For the sake of completeness, however, butter is dealt with briefly in this chapter. In addition, because the historically strict legal limitations on the blending of butter or butterfat with vegetable oil or fat have been lifted recently in some countries, these products will increasingly be mixed, and the processing of the one will be applied to the other and vice versa. Other high-fat, milk-based products such as cheese and curd clearly belong to dairy technology and are therefore not dealt with here. The same applies to sausages with a fat content that can approach >50% of the product weight and up to 70% of the dry matter---clearly a case for meat technology. It is very difficult to make a choice of fat-rich food to be described here, apart from the following: fats and oils themselves, butter, margarine and mayonnaise, which contain 280% fatdoils. Dairy products and meat products are excluded as explained above because they do not employ any of the underlying processes used in oil and fat products. A large percentage of fat is present in ice cream; however, ice cream technology is also very specialized. The products chosen as examples must therefore be somewhat arbitrary and it is not the intention to give a complete picture.
8.1 Butter 8.1.1 The History of Butter
Butter is an ancient food, although not as old as might be expected. Similar to cheese, the other milk product obviously known in many cultures, butter was long unknown (Hanssen and Wendt 1965). It is first mentioned in the Old Testament: “Surely the churning of milk bringeth forth butter.” (Proverbs 30:33). This part of the Bible originates from -1000 BC; even earlier in Genesis 18:8: “Abraham took butter and milk and the calf which he had dressed.” In the past, butter was produced on farms by separating cream from the surface of milk left to stand overnight. This milk was left for souring by the ubiquitous milk bacteria. Buttering itself was carried out in special drums, called chums. The cylindrical churns were equipped with a beater to beat the cream. The fat globules of the cream, which are surrounded by a lipoprotein membrane in the milk, were partially 71 9
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broken and their fat united in larger droplets or grains. After phase inversion induced by the beating, the butter grains were separated, washed and pressed. At the end of the 19th century, the process was immensely improved by the invention of mechanical cream separation, pasteurization and the introduction of special species of milk bacteria as well as buttering machines. After the concentration of population in the cities, the local small dairies, via mergers and acquisitions, were replaced by large “milk factories” in the large new metropolitan areas. 8.1.2 The Economic Importance of Butter
Butter is a food of significant importance in Europe and the U.S. Butter production worldwide exceeds 8 million tons. Table 8.1 shows production for some selected countries. In Europe especially, around the mid- 1980s, there was heavy overproduction that could be stopped only by strong measures, in this case freezing of subsidies at a certain level. The overproduction was caused by the intervention price guarantee of the EU-market system, which sets minimum price levels above the world market price for milk and milk products. In 1985, the so-called butter mountain in the European Union accounted for more than 1.2 million tons. By the application of these strong measures, it was reduced to almost zero within 3 years. The share of butter in the consumption of yellow fat differs greatly among European countries, mainly as a result of historical influence. In the Netherlands, usually seen as a typical dairy country, it is only -lo%, whereas in Ireland, another typical dairy country, it is 90%; in Germany it is -50%. Table 8.1 gives production and consumption figures. Generally, the European market for yellow fat spreads (butter and margarine) has been shrinking by some 2-3% per year for many years. This is due mainly to a change in eating habits in northern Europe. 8.1.3 Legislation Concerning Butter
Legislation concerning butter was national in Europe until 1994, when the European Community issued a directive that transferred control to the national level in every member state of the Europear Union (Table 8.2). For most countries, this directive brought tremendous liberalization into a market segment that had been characterized by protectionism for the last 100 years. In the U.S., the Department of Agriculture (USDA) defines butter in paragraph 32 1 a: “For the purposes of this chapter, ‘butter’ shall be understood to mean the food product usually known as butter, and which is exclusively from milk or cream, or both, with or without common salt, and with or without additional coloring matter, and containing not less than 80 per centum by weight of milk fat, all tolerances having been allowed for.” The FA0 codex allows for a maximum water content of 16% and not more than 2% of nonfat-milk constituents. The standard also approves annatto, p-carotene or curcumine in unlimited amount as colorants. Salts to adjust pH may be added to a maximum of 0.2%;these are Na3P0,, Na,C03, NaHCO,, NaOH and Ca(OH),.
Fat as Food
72 1
TABLE 8.1 Butter Production and per Capita Consumption in the World and Selected Countries Production (1000 MT)
1950
1960
1970
1980
1990
1995
Total world
4990 62 7 285 84 164 74 99 292 15
5240 630 405 83 166 100 87 350 39 46
6110 51 6 494 42 131 121 92 506 64 70
i‘009
7920 591 648 49 93 178 55 445 140 148 45 13 98
6610 572 486 27 54 132 34 373 116 143 25 19 93
us. Germany Sweden Denmark Netherlands Belgium France Great Britain Ireland Spain Portugal Italy Per capita consumption (kg/y)
U.S. Germany Sweden Denmark Netherlands Belgium France Great Britain Ireland Spain Portugal Italy
65
69
68
520 576 41 114 181 69 536 167 111 26 6 72
1950
1960
1970
1980
1990
1995
3.4 8.7 9.4 10.6 5.0 8.8 7.7 8.9 15.9
2.4 8.6 6.0 9.1 2.8 10.6 9.0 8.8 11.8 -
1.5
-
2.0 7.1 5.1 8.9 3.6 8.5 9.5 6.1 11.8 0.5 0.7 2.1
2.0 7.3 2.4 5.8 3.4 7.5 8.8 3.5 3.4 0.5 1.5 2.4
2.0 7.0 2.1 2.1 3.5 6.1 8.4 3.0 3.4 0.5 2.1 2.2
-
2.0
8.1.4 Composition and Properties of Butter Butter is produced by concentrating cream separated from milk (Table 8.3). To produce 1 kg of butter -25 L of milk are required. The fatty acid composition of milk fat differs depending on the fodder (usually equivalent to the season; see Chapter 3.1). The same accounts for the vitamin content that is much higher in summer butter or with improved non-silo feeding. During fermentation with butter cultures, flavors are formed, with diacetyl (up to 3ppm) predominating. Traces of butyric acid also occur, which in higher amounts is mainly responsible for the off-taste of old rancid butter. The formation of acidity and flavors during bacteriological souring of milk is time dependent (Fig. 8.1). The microstructure of butter is shown in Figure 8.15. The fat globules that typically make up its structure can clearly be seen. Water droplet distribution is coarse, giving
Fats and Oils Handbook
722
TABLE 8.2
Council Regulation 2991/94 of the European Community Concerning Milk Fats Fat group Definition
Sales description
Product categories Additional description of the category with an indication of the O/O fat content by weight
A. Milk fats Products in the form of a solid malleable emulsion principally of the water-in-oil type, derived exclusively from milk and/or certain milk products for which the fat is the essential constituent of value. However, other substances necessary for their manufacture may be added, provided those substances are used for the purpose of replacing either in whole or in part, any milk constituents.
1. Butter
The product with a milk-fat content of not <80 O/O but <90 %, a maximum water content of 16% and a maximum dry non-fat milk material content of 2%
2. Three-quarterfat butter*
The product with a milk-fat content of not <60 Yobut <62 O h .
3. Half-fat butter** The product with a not not milk-fat content of not <39 Yo but <41 %. 4. Dairy spread The product with the following milk-fat X% contents: <39% >41% but <6O% >62% but <8O%
Exceptions for Denmark: 'sm~r60 and "smm 40.
a fresh taste sensation. The average composition of European butter as given by the German Ministry of Agriculture is shown in Table 8.4. More detailed compositions of different butter types are given by Renner and Renz-Schauer (1986). Paralleling the fatty acid composition, the physical properties of butter are different in summer and winter. Table 8.5 shows these differences expressed by the solids content at different temperatures as well as the C-values. The latter reflect the firmness of the product and are a measure of its spreadibility. The figures show that spreadability of butter is very poor when taken directly from the refrigerator. TABLE 8.3
Average Composition of Milk, Cream and Butter
Water Proteins Fat Sugar Minerals Cholesterol Vitamin A Vitamin D Vitamin E
(Oh)
(Old (Oh)
(YO)
(YO)
(%)
IU IU IU
Milk
Cream
Butter
88.5 3.2 3.8 4.6 0.8 0.01 -140 0.5-4.0 0.08-0.2
60.0 1.9 35.0 2.5 0.3 0.12
17.4 0.6 81 .O 0.7 0.1 3 0.28 20-25,000 250-750 12-30
Fat as Food
40 10.20
723
20
. . .......
#.----------d
Acidity
,#'
/
I
30/0.15 -
-15
I I
Citric': acid
II
I
,
, I
2010.10 -
1010.05-
0
8
- 10
/
-5
_--,
,
,
I
,
,
,
~
~
~
Z
The chemistry and physical properties of milk and milk products are discussed in detail by a number of authors, including Alais (1961), Kiermeier and Lechner (1973), Veisseyre (1975), Tope1 (1976), Walstra and Jeuness (1984) and Wong (1989); butter making is described by Mohr and Koenen (1958) and McDowell(1953), among others. TABLE 8.4 Average Composition of European Buttera Compound
("Id
Water Protein Fat Carbohydrates Minerals Sodium Potassium Magnesium Calcium Nickel Phosphorous Vitamin A Carotine Vitamin E Cholesterol Lecithin
15.3 0.67 83.2 0.72 0.1 1
(ppm)
(ppb)
Range 14.1-16.0 0.50-0.82 82.0-83.7 0.10-0.1 3 31-80 1CO-2400 1842 110-190
51 160 30 130 100 210 5.9 3.8
aSource: German Ministry of the Agriculture.
13 2.4 2
1 80-2 70 5.2-6.7 3.0-4.6 3.0-25.0 2.2-2.7 1.6-2.0
Compound Fatty acids ButyricCapronicCaprylicCapricLauricMyristicPalmiticStearicMyristoleic PalmitoleicOleicLinoleicLinolenic-
(%)
2.6 1.5 0.9 2.0 2.0 8.1 21.1 9.7 1.2 1.8 30.1 1.8 1.2
,
Fats and Oils Handbook
724
TABLE 8.5 Solids Content and C-Values of Butter Dependent on Temperature and Season Solids Content Measured at 5 "C 10°C 15°C 20°C 25°C 30°C 35°C 40°C
(41'F) (5OOF) (59°F) (68OF) (77OF) (86°F) (95°F) (104OF)
Winter
Summer
52-58
44-48 30-34 14-1 7 7-1 0 3-5 0-1
34-40
1 7-21 9-1 3
4-6 0-1 c0.2
C-value Winter
Summer
2000-3500 1500-2200 900-1 500 200-300
3500-5000 2000-4000 1500-2500 400-800
Winter butter = stable feeding: summer butter = grassing.
8.1.5 Butter Making
Butter is produced according to different processes all starting with the concentration of the cream. An overview is given in Figure 8.2.
8.7.5.7Milk Treatment. The milk supplied is pasteurized by heating it and holding it at 71-74°Cfor 30-40 s. Under these conditions, most bacteria are killed. Only some thermophilic bacteria may survive; however, these are not pathogenic. Raw,milk
butter fmm la& cnarn. only
&l O'C, aysUIHzPtionof the fat globuba
Breakkg the fat g b b u b
Separation dNm, perfonfedMar
Kneading
Fig. 8.2. Flow chart of butter production.
Fat as Food
725
Usually this pasteurization is done via plate heat exchangers. Temperatures applied may be higher for technological reasons. 8.7.5.2 Cream Separation and Heat Treatment. If milk is left alone, it creams up; the cream, which can be separated by decantation, has a fat content of 15-20%. This method, however, was used only on the farms in the old days. A specific density of 0.931 gkm3 for milk fat and 1.034 gkm3 for skim milk creates sufficient difference for centrifugal separation. Therefore cream today is separated via cream-centrifuges (see Chapter 7.2.6, centrifuges) and then pumped into a buffer. There it is adjusted to the right fat content by the addition of skim milk. Today’s centrifuges have a throughput of -20 to& with a revolution speed of 6500/min. To increase storage stability of butter and to improve ripening of sour cream butter, the cream is heated to at least 95°C. At this temperature, those microorganisms that survived pasteurization are also killed. Additionally, all lipolytic enzymes are inactivated. Protein is slightly denatured so that the souring microorganisms have a better opportunity to attack. Some producers degas after heating with the aid of a vacuum. The intended benefit of this treatment is to separate unwanted flavor, but this remains a debatable practice.
8.7.5.3 Souring (Sour Cream Butter). Souring of cream when producing sour cream butter is usually done with cultures of Streprococcus diacetilacris, Streptococcus cremoris and Leuconostoc citrovorum. Cultures can be used deep frozen, freeze dried or multiplied in a mother culture. The optimal temperature to multiply mother cultures for buttering lies between 25 and 30°C. The maximum acidity achievable is 1%. The base material for such mother cultures is skim milk, which is heat-treated, cooled, inoculated with the original culture and subsequently fermented. Ripening of the culture is stopped by cooling. Soured milk for buttering is prepared by inoculation from this stock (Fig. 8.3). The amount of souring culture as well as the cooling temperature, the souring temperature and the ripening temperature depend on the hardness of the milk fat, which is proportional to the iodine value (see Chapter 3.1.1 and Fig. 8.4). During souring, flavors develop, with diacetyl (butane-2,3-dione) as the most prominent. It develops from acetoin, which itself has no influence on the taste. The precursor acetoin is built by decarboxylation of acetyl lactic acid and is present in a quantity 10- to 20-fold that of the diacetyl itself (Timmen 1960). The presence of oxygen is essential for the formation of diacetyl from acetoin. The reaction can be promoted by the addition of citric acid.
-
8.1.5.4 Cream Ripening. During the preceding processing steps, cream was heated to a temperature at which all fat in the fat globules has melted. To ensure efficient buttering, the fat has to be partially recrystallized (see Fig. 8.2). This is done in vessels called cream ripeners; sizes are up to 20 ton. The cream is held in these cream ripeners for 4-20 h at 6-10°C. At this temperature, part of the milk fat solid-
Fats and Oils Handbook
72 6
Raw mMk WS5*C, l(F15mln
t.actic.cream
(ripsnsd MU^
Fig. 8.3. Flow chart of lactic culture production and cream souring.
ifies along the hulls of the globules, thus stabilizing them. Details concerning the influence of the cream ripening conditions on the structure of butter are given by Skakaly and Schiiffer (1988); the influence of heat treating the cream on the physical properties of butter is described by Danmark and Bagger (1989).
Fig. 8.4. Processing parameters for cream souring, depending on the iodine value of the milk fat (after Herrmann eta/., courtesy of Alfa Laval).
72 7
Fat as Food
PhosDhatide molecules Protein molecules
Fig. 8.5. Structure of a fat droplet in cream,(adapted from Mohr and Koenen 1958).
8.7.5.5 Buttering (Churning). Milk fat appears in both milk and cream in droplets that consist of a hull of phosphatide and protein molecules filled with fat and oil (Fig. 8.5); these phosphatides stabilize the emulsion milk, i.e., the emulsion oil in water. At buttering temperature, the fat in these globules is fractionated into a fat layer that precipitates along the phosphatide/protein hull, reinforcing that hull, and a liquid kernel. For buttering, the globules have to be broken up so that liquid fat from these globules can float together to form larger globules (Fig. 8.6). As a prerequisite, there must be a certain minimal distance between the fat globules in the cream, which depends on the concentration stage of the cream (Fig. 8.7).
Fig. 8.6. Distribution of oil droplet sizes in milk and cream (after Rahn and Sharp 1928).
72 a
Fats and Oils Handbook
0
20% Change in volume and pack density of the fat globules
1 40% I n
0
72%
80%
0 Milk
Cream
Cream
Cream
Cream
Fig. 8.7. Distance of oil droplets in creams of different concentrations (after Mulder and Walstra 1974).
Once the fat globules are concentrated enough, mechanical stress (beating) can destroy the phosphatide and fat hull so that the liquid portions can coalesce and the empty hulls can agglomerate to butter grains. If the process is continued by washing the butter grains, small grains further agglomerate to form larger ones. Kneading these larger grains leads to phase inversion (oil in water -+ water in oil) and smooth consistency. From the partial emulsion of cream in milk, an emulsion of butter serum in butter oil can be produced (Fig. 8.8).
Sopardon drum, p.r(ont.dfibr
Butter
Fig. 8.8. Flow chart of continuous butter making starting from soured (ripened) cream.
Fat as
Food
729
Butter can be made in a batch operation (with older machinery) or continuously, according to different processes. Using the discontinuous old process, butter is made in batches of up to 12 ton. The vessels called chums are equipped with rotational asymmetric beating mills with vwiable revolution speed. After they have been filled with cream to 4 0 4 5 % of their capacity, they are cooled (winter 12-14"C, summer 8-10°C) and then the cream is beaten. By the rolling, falling and foaming of the cream, butter grains are separated after 40-60 min, then washed, pressed and churned. It is important not to cool down the cream too far because this results in too many of the fat globules becoming crystallized. These globules are not able to release oil and to agglomerate to butter grains. If the temperature is too high, a non-grainy, oily product is produced with not enough fm particles to give consistency. If the revolutionary speed of the beater is too high, a creamy product is obtained that is reminiscent of whipped cream. Modem buttering machines work continuously (Fig. 8.9). The cream enters the machine via (E) and is overworked in the churning cylinder (1) with a highspeed rotatory beater (up to 1500/min). From there, the butter grain is conveyed into the postchuming cylinder (2) where it is washed with cooled butter milk. In (3), the butter grains are squeezed dry and the residual butter milk removed. For salted butter, brine is injected ( 5 ) under high pressure, or water may be added to correct the water content. After a final working station (kneading, 7), butter leaves the machine as a line. A probe to continuously monitor water content (8) allows the machine to run automatically. Butter can then be directly packed or stored. In many European countries, butter packs do not carry the production date but the date of packaging even if frozen in between. The main processing parameter that has to be observed carefully during buttering is the water content. For the so-called Fritz-process, Mohr and Koenen (1958) found the following equation: WE= Fc - 28.5 where WEis the water content of the butter produced and Fc is the fat content of the cream used (43 c F, c 52). The water content of the butter produced increases with the amount of butter milk that is emulsified into the fat phase. Usually that amount rises proportionally with the following: the temperature of the cream, the fat content of the cream, the revolutionary speed of the beater and the revolutionary speed of the squeeze-drying screw; it is inversely propor-
Fig. 8.9. Butter-making machine (after Herrmann eta/., courtesy of Alfa Laval).
Fats and Oils Handbook
730
tional to the throughput (amount of cream fed per time). Figure 8.10 shows the parameters that Mohr and Koenen (1958) found to be important for buttering and for control of the water content. There are more recent butter processes, e.g., the NIZO-process, in which lactic culture concentrates are added to the already buttered sweet cream butter. These culture concentrates contain very high levels of diacetyl. The advantage of this process is a higher pH and the production of sweet butter milk as a byproduct; the process is very commonly applied in France (Cabarat and Veisseyre 1983). In the U.S., some processes are allowed that are not legal in Europe. In these, the fat globules of cream are destroyed at 10-14"C, and free butter oil is produced. The butter oil, with a fat content of -93%, is separated. Skim milk in the appropriate amount is added to this oil, and it is cooled similarly to margarine emulsions (see Chapter 8.2.7). 8.7.6 Reconstituted Buffer
In most European countries, recombining butter fat and milk to produce butter is not allowed. Butter produced according to this process differs from normal butter because butter serum that was separated when the butter fat was produced is replaced by skim milk (soured skim milk to imitate sour cream butter). Usually emulsifiers and flavors have to be added to produce butter from that process. Its water phase can contain up to 2% of skim milk powder or milk solids. Production is done via scraped surface heat exchangers and crystallizers (see margarine production, Chapter 8.2.7.3.2). Water content of butter
[%I
22 21 20 19 18 17 16 15 300 6
8 c lo00 D 40
10 1200 50
12 1400 00
kath "C mid mid
Fig. 8.10. Influence of some processing parameters on the water content of butter (after Mohr and Koenen 1958).
Fat as Food
73 1
8.1.7 Half-Fat Buffer
Following changes in consumer behavior and attempts to create new markets, halffat butters entered the market in the mid-1980s. In many countries, their introduction was hindered by protectionistic laws. In Germany, for example, a product of this type may not be called “half-fat butter” but must be called “spreadable milk half-fat.” The composition was also strictly controlled. These restrictions have been overcome with the latest European Union legislation. Gerstenberg (1988; Fig. 8.11) describes a line configuration to produce halffat butter that is similar to those used for margarine makmg. Other processes start from melted butter, which is emulsified with different ingredients (water, milk solids, emulsifiers, thickening agents or stabilizers). In principle, the production process of half-fat butter follows that of half-fat margarine. 8.1.8 Other Butter Products
There have been many attempts to increase butter consumption, mainly in periods of excess production as described above. In Europe, butter from subsidized stocks is used for these purposes so that the price of the end-product may be lower than the market price of the source material, which is artificially kept above the world market price. The production of butterfat from butter is described in Chapter 3.1.1. Butter-based products are also offered as bakery fats. The flavor that develops during baking gives a special note to such cakes. However, margarine is usually better suited for baking because its fat blend can be tailor-made to the special demand of baking fats (puff pastry, for example). This is valid at least for those countries in which any modification of butter or butterfat is forbidden. Using fractionation (see Chapter 6.2.3.3), butterfat stearines that could even replace traditional puff pastry fats can be separated (Pedersen 1988). Such products have not yet penetrated the market. Additional butter-based products include butter preparations. Butter is blended with garlic, herbs, pepper, salmon or anchovy. Such products are usually sold in small packs. Now that most countries have lifted the ban on mixtures of butter and vegetable fatdoils, blends are being used for all purposes that were traditionally reserved for butter, margarine or shortenings. However, their market potential is Oil phase
(Butterfat) Water phase
Preparation 4-
I I
Premix
I[
P n p d k q 4
-
Mixing and emulsifying
I Cooling
I
Half-fat butter
Scraped surface heat exchangers (see 8.2.5) Crystallization of fat part
(Low-calorb butter)
~ i8.1~1. .~l~~
of
half-fat butter production (after Gerstenberg 1988).
732
Fats and Oils Handbook
still limited because they have no clear advantage over the traditional products. In Asia, high quantities of ghee, a buffalo-butter fat, are produced.
8.2 Margarine At present, excluding China, -9 million tons of margarine are being produced per year. Margarine therefore plays a significant role in nutrition. Margarine accounts for -25% of the fat intake of the northern hemisphere’s population, approximately equal to the consumption of butter. 8.2.1 History of Margarine
In the middle of the 19th century, a dramatic development arose in food production methods that led to new products and industrial production of food. Among others in Europe, Nestle for the first time produced milk powder and condensed milk, and Oetker company invented and launched baking powder. At the same time, margarine was invented. The invention was triggered by the desire of the French emperor, Napoleon 111, to have a fat similar to butter but available in higher quantities at a lower price. He would need this fat to nourish his army in the forthcoming war with Germany. He asked the chemist MBge-Mourii?s to do this development work at the state farm Saint-Cloud close to Paris. MBge-MouriBs tried to emulsify milk with so-called olio margarine, a fraction of beef tallow. He followed this idea because he was convinced that milk fat was built from the storage fat of the cattle, even if they were not fed. Therefore, his basic idea was to leave out the intermediate step via udder and milk and produce milk fat directly from tallow. In the year 1867, Mi?ge-Mourii?s succeeded in producing a product that was considered acceptable. On July 15, 1869, he asked for approval of a patent that was granted on October 2 of the same year. The patented process starts with slow cooling of melted beef tallow (see Chapter 6.2, fractionation). The recipe read as follows: “The stearin fraction melting above 30°C is separated and the oil that accounts for two thirds of the beef tallow is amalgamated with the same amount of skim milk and 0.1-0.2% of freshly cut cow udder. The emulsion is shock-cooled with ice water and kneaded to achieve plasticity.” The name used for the new product “margarine” is derived from the Greek word for pearl “margarites,” describing the pearly gloom of the beef tallow fraction used. At the beginning of the German-French war, a margarine factory was erected very quickly in Passy not far from Paris, but soon after had to be closed following the complete defeat of the French army. The patent for margarine making was then bought by the two Dutch butter dealers, Simon van den Bergh and Anton Jurgens. Those two in particular ensured that production locations were set up all over Europe in the following years and that margarine gained great distribution. In many European states, the launch of margarine was not appreciated by the butter producers, the wealthy landed aristocracy who did whatever they could to close off their home markets from the imita-
Fat as Food
733
tion product. The situation is well illustrated by the events accompanying the introduction of margarine in Germany. At the beginning of 1886,the imperial government became active and proposed a law concerning the traffic in the so-called artificial butter. One of the main aims was to make margarine easily distinguishable from butter. First, plans to color margarine blue were rejected by the social democrats who feared that the difference between children of rich butter-eaters and those of poor margarine-eaters would become apparent in the school yards. Other discriminating restrictions such as the limitation to special packaging formats (cubes and truncated cones) remained in place in Germany until the end of 1985.An overview of the historical developments between 1887 and 1897 is given by Schmitz and Pape (1977). After the first detailed scientific discussion of margarine by Soxhlet in 1895,another famous chemist, Volhard, spoke about margarine in 1896 in a speech delivered to the annual meeting of the Society of Natural Science of Halle. He explained its composition and ingredients and tried to explain that it was not a imitation of butter but a product of its own. He said: “Margarine has nothing to do with the falsification of butter.” Margarine making obviously had already reached a high standard, because he continues: “In good margarine halls . . . you find a surprising degree of hygiene that impresses the visitor.” The history of margarine was compiled by Stuyvenberg
(1969). 8.2.2 Economic Importance
From the above beginnings, margarine has developed into a tailor-made fat product. Its properties can be adjusted to the very different demands of catering, bakery and the kitchen. This is impressively reflected in the tonnage that is produced each year (Table 8.6). In Europe, the tonnage in individual countries follows the eating habits of the country. In the so-called “oil countries” of Southern Europe, the consumption of oil is traditionally high and emulsion fats play a subordinate role. Thus, the consumption in Italy and Spain is <1.5 kg per person per year. In some of the countries perceived as “milk countries” such as the Netherlands (margarine:butter ratio of 9:l)and Denmark, a lot of margarine is consumed. The latter has the highest per capita consumption in Europe (just under 20 kg/y). Of the Northern European countries, the country with the lowest consumption is Ireland with 4.5 kg. In comparison, North Americans eat 5.5 kg per person per year. Singapore is the world champion in this field with a per capita consumption in 1995 of almost 45 kg. Production figures in 1990 for important countries not listed in Table 8.6 were 320,000 ton (2.1kg per capita) in Brazil, 481,000ton (8.5)in Turkey, 880,OOO ton (1.1)in India, and 1,025,000 ton (9.1)in Pakistan. As a result of the immense success of margarine, the amount of beef tallow needed exceeded even the enormous potential of the main exporting countries, the U.S. and Argentina. Coconut oil as an alternative was not available in sufficient quantities and was also very expensive. The supply problem could be solved only when W. Normann invented the hardening process (see Chapter 6.4,hardening),
Fats and Oils Handbook
734
TABLE 8.6 Margarine Production and per Capita Consumption in the World and Selected Countries Production(1000MT) Total world
us. Germany Sweden Denmark Netherlands Belgium France Great Britain Ireland Spain Portugal Italy
1895
1910
300
450
1938
1950
1960
1970
1980
1990 1995
140 2360 175 425 25 50 140 432 61 79 81 61 72 176 64 65 35 54 211 380 5 6 1 2 <1 1 forbidden to 1954
4200 769 793 112 88 239 115 116 374 10 7 5 46
5480 1012 730 135 88 237 136 160 314 13 25 24 43
7400 1176 710 159 98 243 159 165 383 15 47 38 69
9100 9350 1254 1130 680 600 129 120 101 82 233 278 189 265 158 135 346 465 20 19 82 86 60 52 77 85
Per capita consumption (kg/yr)
1938
1950
1960
1970
1980
1990 1995
U.S.
1.3 6.1 12.5 7.1 6.7 0.8 4.5 1.1
2.8 8.0 2.7 14.1 17.0 7.4 1.4 7.7 1.1
-
-
4.3 11.0 10.3 19.0 20.1 11.8 2.4 7.0 3.5 0.3 0.7 0.9
5.0 8.8 11.0 18.2 18 12.8 3.2 5.6 4.9 0.7 2.3 0.8
5.3 8.4 10.1 19.2 17.2 15.4 3.1 6.9 4.4 1.3 3.8 1.2
5.0 8.9 15.1 19.6 15.6 19.0 2.8 6.0 5.7 2.1 5.7 1.3
Germany Sweden Denmark Netherlands Belgium France Great Britain Ireland Spain Portugal Italy
-
0.1 forbidden to 1954
4.3 7.3 13.6 15.7 17.9 26.2 2.3 8.0 5.2 2.2 5.3 1.5
i.e., the possibility of converting oils into fats. Today, margarine is produced mainly from vegetable oils and fats. Comparisons with other fats are given in Chapter 1.
8.2.3Legislation Legislation differs greatly from country to country. As examples, the directive of the European community (Table 8.7) and the relevant U.S. law are given here. The U.S. law states in subpart B, requirements for Specific Standardized Margarine, 0 166.110: (a) Description Margarine (or oleo-margarine) is the food in plastic form or liquid emulsion, containing not less than 80 percent fat determined by the method prescribed in OfJicial Methods of Analysis of the Association of Oficial Analytical Chemists, . . . It is produced from one or more of the optional ingredients in paragraph (a)( 1) of this section, and one or more of the optional ingredients in paragraph (a)(2) of this section, to which may be added one or more of the
73 5
Fat as Food
TABLE 8.7 Council Regulation 2991/94 of the European Community Concerning Fats
Fat group
Product categories Additional description of the category with an indication of the O/O fat content by weight
Definition
Sales description
B. Fats
1. Margarine
Products in the form of a solid malleable emulsion principally of the water-in-oil type, derived from solid and/or liquid vegetable and/or animal fats suitable for human consumption, with a milk-fat content of not >3% of the fat content.
The product obtained from vegetable and/or animal fats with a fat content of not <80% but
2. Three-quarterfat margarine*
The product obtained from vegetable and/or animal fats with a fat content of not ~ 6 0 %but <62%.
3. Half-fat margarine**
The product obtained fromvegetable and/or animal fats with a fat content of not<39% but <41%.
4. Fat spread X%
The product obtained from vegetable and/or animal fats with the following fat contents: <39% >41 YObut <6O% >62% but <80%
Exceptions for Denmark 'margarine 60 or **margarine 40. Note: The milk-fat component of the products listed in the Annex may be modified only by physical processes.
optional ingredients in paragraph (b) of this section. Margarine contains vitamin A as provided for in paragraph (a)(3) of this section. 1. Edible fats and/or oils, or mixtures of these, whose origin is vegetable or rendered animal carcass fats, or any form of oil from a marine species that has been affirmed as GRAS or listed as a food additive for this use, any or all of which may have been subjected to an accepted process of physico-chemical modification. They may contain small amounts of other lipids, such as phosphatides or unsaponifiable constituents, and of free fatty acids naturally present in the fat or oil. 2. One or more of the following aqueous phase ingredients: (i) Water and/or milk and/or milk products. (ii) Suitable edible protein including, but not limited to, the liquid, condensed, or dry form of whey, whey modified by the reduction of lactose and/or minerals, nonlactose containing whey components, albumin, casein, caseinate, vegetable proteins, or soy protein isolate, in amounts not greater than reasonably required to accomplish the desired effect. (iii) Any mixture of two or more of the articles named under paragraphs (a)(2) (i) and (ii) of this section.
736
3. (b)
(c) (d)
Fats and Oils Handbook
(iv) The ingredients in paragraphs (a)(2) (i), (ii), and (iii) of this section shall be pasteurized and then may be subjected to the action of harmless bacterial starters. One or more of the articles designated in paragraphs (a)(2) (l), (ii), and (iii) of this section is intimately mixed with the edible fat andor ingredients to form a solidified or liquid emulsion. Vitamin A in such quantity that the finished margarine contains not less than 15,000 international units per pound. Optional ingredients. (1) Vitamin D in such quantity that the finished oleomargarine contains not less than 1,500 international units of vitamin D per pound. (2) Salt (sodium chloride); potassium chloride for dietary margarine or oleomargarine. (3) Nutritive carbohydrate sweeteners. (4)Emulsifiers. ( 5 ) Preservatives including but not limited to the following within these maximum amounts in percent by weight of the finished food: Sorbic acid, benzoic acid and their sodium, potassium, and calcium salts, individually, 0.1 percent, or in combination, 0.2 percent, expressed as the acids; calcium &sodium EDTA, 0.0075 percent; propyl, octyl, and dodecyl gallates, BHT,BHA, ascorbyl palmitate, ascorbyl stearate, all individually or in combination, 0.02 percent; stearyl citrate, 0.15 percent; isopropyl citrate mixture, 0.02 percent. (6) Color additives. For the purpose of this subparagraph, provitamin A (betacarotene) shall be deemed to be a color additive. (7) Flavoring substances. If the flavoring ingrdents impart to the food a flavor other than in semblance of butter, the characterizing flavor shall be declared as part of the name of the food in accordance with 0 101.22 of this chapter. (8) Acidulants. (9) Alkalizers. Nomenclature. The name of the food for which a definition and standard of identity are prescribed in this section is “margarine” or “oleomargarine.” Label declaration. Each of the ingredients used in the food shall be declared on the label as required by the applicable sections of parts 101 and 130 of this chapter. For the purposes of this section the use of the term “milk“ unqualified means milk from cows. If any milk other than cow’s milk is used in whole or in part, the animal source shall be identified in conjunction with the word milk in the ingredient statement. Colored margarine shall be subject to the provisions of section 407 of the Federal Food, Drug, and Cosmetic Act as amended.
8.2.4 The Structure of Margarine
Margarine is an emulsion of the type water in oil, consisting of 80% fats and oils and 20% of an aqueous phase, which like the oil phase contains soluted ingredients. About 20% (minimal -12%) of the triglycerides of the fat blend are solid at room temperature, the remainder is liquid.
Fat as Food
73 7
During processing, a phase inversion takes place in the emulsion so that, in margarine, water is the dispersant; oils and fats constitute the continuous phase. That means that water is dispersed in droplets in a continuous oil matrix. The oil phase of a margarine as well as the structure of processed shortening is not homogeneous, but consists of a network of fat crystals and of agglomerates of fat crystals with liquid oil distributed in between. These agglomerates usually have a size of 15-20 pm. The structure becomes clear in a picture that shows the crystal network of a shortening that remains after removal of the liquid phase, i.e., the oil (Fig. 8.12). Margarine draws its mechanical stability from the crystal network as well as from the stability of the emulsion. The bonds of the finely dispersed water droplets contribute to the stabilization of the emulsion; the surface of these droplets can constitute up to 750 m2kg of margarine. The disadvantage of this fine water droplet distribution is the very slow release of flavors and salt during its melting in the mouth. A comer droplet distribution would result in a fresher (less fatty) impression when in contact with the tongue. The enormous advantage of such fine droplet distribution is the microbiological stability of the emulsion. Therefore, water droplets with a size <5 pm are the objective; such droplets are smaller than bacteria so that any bacteria (should they be present or brought in during open shelf life) cannot multiply. Therefore, provided storage conditions are adequate, the emulsion is microbiologically relatively stable. Haighton (1963) calculated the following data per milliliter of fat phase for a margarine with 20% solids, an average crystal size of 1 pm in length, 0.5 pm in width, and 0.25 pm in strength (data per milliliter fat phase): number of crystals medium distance from each other total surface area
1.6 x 1012 0.32 pm 2700 m2
To achieve a certain consistency, the crystal networks built often have to be destroyed intentionally by overworking. By agglomeration of crystals (secondary
Fig. 8.12. Network of fat crystals in a de-oiled shortening (courtesy of Unilever; see also juriaanse and Heertje 1988).
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Fats and Oils Handbook
Fig. 8.13. Network of fat crystals in de-oiled dehydrated margarine (courtesy of Unilever; see also Heertje et a/ . 1987).
bond), stability is regained. Crystal growth continues after the product has been processed and wrapped or filled into tubs; the margarine matures and stiffens up. The following scanning electron microscope pictures show typical crystal structures of margarine. When the aqueous and the oil phase are removed, the remaining crystal network ( f ) can clearly be seen. The same is shown for a shortening (Fig. 8.12). Figure 8.13 demonstrates the structures that are left behind by the water droplets (w). Around those water droplets, a hull consisting of crystallized highermelting emulsifier as well as a crystallized fat has built up. After the water droplets have been removed, this structure remains and becomes clearly visible (Fig. 8.14). Unlike margarine, butter has a discontinuous structure. In butter samples, the broken globules described in Chapter 8.1.5.5 can easily be seen (Fig. 8.15). They consist of a hull of high-melting fat particles into which oil is wrapped (Buchheim 1970, Bucheim and Precht 1979). The hull of these globules of crystallized fat is 0.1-0.5 pm thick; the diameter averages 3 km. In cream, these globules are completely intact, whereas most of them are broken up in butter. The figure shows these broken globules from which butter oil has leaked. This structure is caused by
Fig. 8.14. Structure left from water droplets in margarine (courtesy of Unilever; see also Heertje et a / . 1987).
Fat as Food
739
Fig. 8.15. Fat globules of butter (courtesy of Unilever; see also Heertje e t a / . 1987).
the churning process (see Chapter 8.1) for which the concentrated cream is prepared by physical ripening at low temperature.
8.2.5 Composition of margarine Margarine is an emulsion fat with a water in oil emulsion. In most countries, margarine contains 80% fadoil (see Chapter 8.2.3),with 40% in the half-fat margarines or minarines that were first introduced in 1964. In some countries, this amount can be chosen deliberately. The fadoil phase contains the fat-soluble ingredients. These are usually fatsoluble flavors, vitamins as well as emulsifiers and carotenes. The aqueous phase holds the water-soluble ingredients, which are generally water-soluble flavors, salt, milk or milk solids, and in special cases, preservatives. Margarines with lower-fat content also contain stabilizers, e.g., gelatin, and ingredients to increase the dry matter content, e.g., milk powder (Table 8.8). According to the local taste in the different countries or following special legislation, the amount of individual ingredients may exceed (even heavily) the numbers given in the table. In some countries, vitamins, for example, are added in much higher amounts than shown to fight malnutrition, because margarine is the only source of fat-soluble vitamins in the diet. In some countries, the use of hardened fats is or was not allowed until recently. In others, the use of flavors and coloring agents is forbidden. As an example of the margarine consumption of European households, the average use of German products is given in Table 8.9 as published by the Ministry of the Agriculture. For countries in which the trade keeps margarine in the cool cabinet, the fat composition can be slightly softer. For tropical countries, the content of consistent fats must be considerably higher. 8.2.5.7 f a t Blend. The choice of the fat blend of the margarine follows three criteria, namely, the achievement of certain physical properties, the presence of claims or declaration on the pack and nutritional physiological considerations.
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Fats and Oils Handbook
TABLE 8.8 Average Composition of European Type Margarines Component OildFats Emulsifiers Milk Components Acids Salt Flavors Preservatives
Water Vitamins
Stabilizers Colorants
Amount
Examples
Soybean oil, rapeseed oil, sunflower oil, palm oil, >80 coconut oil, partially hardened Lecithin, monoglycerides, moncdiglycerides 0.2-0.6 Soured milk, butter milk, sour whey, sweet whey <6 Citric acid, lactic acid 0.1-0.3 0.1-0.3 Oil and water soluble Traces Sorbic acid, benzoic acid (rarely in margarines, <0.12 usually in half-fat margarines to protect during Open shelf life) Potable water to 100 Vitamin A 1500 Vitamin D 100 Vitamin E 100-300 In half-fat and low-fat margarines Carotene
Taking those criteria into account, a fat blend can vary within relatively wide limits, because oils and fats are themselves refined to be mainly neutral in taste and have equal or at least similar physical properties and chemical composition. Bearing in mind the above criteria, the fat blend composition can be optimized to give the lowest cost. Such optimized fat blends with certain properties can be calculated via computer programs (see, for example, Williams 1967). All required restrictions are considered by these programs. The blend composition for margarine has changed dramatically over the last century of its development in the market. For example, in 1917, >60% of the U.S. margarine fat blend was of animal origin (-one third lard, two thirds tallow; Bailey 1951); in 1948, this was down to <2%. In Europe in the 1930s, whale oil accounted for >40% of the raw material. In Germany, it was even >50%, with a further 25% or more being lauric oils. Today, animal fat has almost completely disappeared, and vegetable oils and fats are dominant in almost all countries (Table 8.10). Other raw materials such as sesame oil also no longer play a role. Anderson (1960) describes an old American formulation that sounds very strange today-60% whale oil, 20% cottonseed oil, and 10% each sesame oil and peanut oil. Slover et al. (1985) and Chrysam (1985) give detailed compositions of American margarines. Comparing American and European margarines, it becomes clear that, in the U.S., cottonseed oil is a common raw material, whereas in Europe this is quite rare because of its relatively high cost. It is used mainly in those countries in which cottonseed is cultivated. Comparing German compositions of the same brands over a period of about 1 y (Fig. 8.16), one can clearly read from the figure the periodically different prices of the raw materials for those oils that can
741
Fat as Food
TABLE 8.9 Average Composition of German Household Margarine9 Content (per 100 g product) Water Protein Fat Carbohydrates Minerals Sodium Chloride Vitamin A Carotene Vitamin D Vitamin E Fatty acids C8:O Cl0:O c12:o c14:0
c16:0
C18:O c2o:o c22:o c16:1
Cl8l c201
C22:l C18:2 c1 8:3
Sterols total Brassicasterol Campesterol Cholesterol Misterol Stigmasterol Caloric value DigestibiIity
Standard*
Margarine Vegetable
19.15 0.2 80 0.4 0.25 101 158 0.53 0.65 2.5 10
19.1 0.2 80 0.4 0.26 101 158 0.5 0.65 2.5 16
0.08 0.08 0.46 2.0 12.2 7.8 0.76 0.3 2.7 26.8 1.5 1.5 17.6 1.9 320
0.3 1 0.38 3.4 1.8 10.7 4.9 0.23
8
(kJ) (YO)
51 115 118 13 3123 95
27.5 0.46 23.1 2.4 310 14 74 7.4 173 26 3123 95
Half-fat 57.9 1.6 40 0.4
1.15 390 615 0.5 0.5 2.5 6 0.04 0.04 0.8 0.42 5.6 3.2 0.19 0.1 5 10.1
15.3 2.2 140 1 27 4.2 78 18 1593 95
*May contain animal fat. aSource: German Ministry of the Agriculture.
be substituted for each other. It becomes clear that certain crude oils appear in the composition for a certain time and disappear again. The period of 1984 is especially interesting, because the price for linseed oil was exceptionally low during some months. Therefore, hardened linseed oil was used-a good but rare raw material. In addition, the f r s t use of palm stearin offered from Malaysia (not specifically shown here) falls into this period of time.
U
N P
TABLE 8.10 Historical (I-V) and Recent (VI-XIV) Margarine Oil/Fat Compositions (% of Fat Blend) Oil/Fat
I
II
111
IV
V
Lard Oleomargarine Fish oil, hardened Coconut oil Palm oil Palm oil, hardened Palm stearin Palm kernel oil Soybean oil Soybean oil, hardened Rapeseed oil Rapeseed oil, hardened Cottonseed oil Cottonseed, hardened Sunflower oil Peanut oil Sesame oil Linseed oil, hardened I. II. 111. IV. V. VI. VII. VIII-XIII. XIV.
Simple composition from the 1950s British animal fat margarine composition-1 950 (after Anderson 1954) British vegetable fat margarine composition -1 950 (after Anderson 1954) American cornpositionof the 1950s. German household margarine composition -1 955 (after Rudischer 1959). Tub margarine with high palmoil content (after Berger and Teah 1988). Wrapper margarine with high palmoil content (after Berger and Teah 1988) German tub margarines 1982/1983 (after Schleenvoigt 1989). Modern European tub margarine (1 995).
VI
VII
Vlll
IX
x
XI
XI1
Xlll
XIV
Fat as Food
743
Fig. 8.16. Fat/oil composition of German tub margarines between 1982 and 1986 (after Schleenvoigt 1989).
The fat blends are composed in such a way as to yield a certain consistency at a given temperature; the solids content at that temperature is the measure. Figure 8.19 shows the relation of solids vs. temperature for the common types of margarine. Only when margarines are used for very special purposes such as puff pastry, or if a special oil, e.g., sunflower margarine, is declared on the pack does the possibility of substituting one raw material for another become very limited. 8.2.5.2 Emulsifiers. Emulsifiers stabilize the emulsion. After the introduction of the process of cooling in scraped surface heat exchangers, they are less important for margarine production than before when the churn-drum process was used. However, they are still one of the most important ingredients. The main emulsifiers used are lecithin and monodiglycerides (see Chapter 8.9). The tension between fat and water is about 21 mN/m. Adding monoglycerides (0.3%), it decreases to 80%, adding monoglycerides and lecithin it falls to 1-5%. Using citric acid esters, it can virtually disappear. 8.2.5.2. I Lecithin. Lecithin is explicitly described in a monograph by Pardun (1989). The surface tension of the system soybean oiVwater is -25 mN/m. The addition of tiny amounts of soy lecithin (0.002%) decreases this to 10% (Table 8.11). Even with the addition of as little as 0.01% lecithin, the maximum effect is reached (with respect to surface tension) and no further improvement is possible. However, lecithin also fulfills other tasks; therefore, usually -0.5% is added. Lecithin replaces the egg yolk that was the only emulsifier in margarine in the old days. For that use, it was necessary to produce specially purified lecithins. By using the alcohol fractionation process, it is possible to achieve a ratio of choline-1ecithin:cephaline of >5:1
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744
TABLE 8.1 1 Surface Tension of a WaterILecithin Mixture Surface tension (mN/rn)
Soy lecithin (%) ~
~
~~
25.0 19.0 2.5 1.8 1.5 1.5 1.5 1.5
0 0.001 0.002 0.005 0.01 0.05 0.1 0.2 ~Soorce:Pardun (1979).
(van Nieuwenhuysen 1976). Such lecithin fractions work as antispatterhg agents when margarine is used for frying. In additon, workability in puff pastry margarines is improved. Carried over from the margarine to the dough, it also improves the baking properties and the synergies between protein and starch with which it forms a complex. 8.2.5.2.2 Monodiglycerides. Monoglycerides and monodiglycerides are naturally associated with oils and fats. They can be produced by the reaction of fats and oils with glycerol (see Chapter 8.9 for their composition and properties). Their surface active properties that stabilize the emulsion are due to the hydrophilic properties of the glycerol-OH residue and the lipophilic properties of the fatty acid chains of the ester. These reduce the surface tension of the system oiYwater (Fig. 8.17). Surface tension [mNlm]
measured at 60 "C
(14ooF) ...........................
...........................
........................
.......................
----- - _ _ _ _ _ _-._ - t
0
1
2
3
4
5
6
7
8
Monodiglyceride [% wt/wtl
Fig. 8.17. Surface tension of the system soybean oiVwater (after Schuster and Adams 1979).
Fat as Fmd
745
TABLE 8.1 2 Hydrophilic Lipophilic Balance (HLB) of Different Types of Emulsionsa Emulsion type
HLB
Emulsion water in oil Wetting of an oil or wax surface Emulsion oil in water Detergent
3-8 7-9
a18 13-1 5
aSource: Lynch and Griffin (1974).
In addition to their ability to influence consistency by stabilizing the emulsion, there is a second effect. Monodiglycerides have a melting point that lies 10-20°C above the melting point of fats and oils that are composed of the same fatty acids. Therefore, during cooling, they crystallize early on in their position around the water droplets between the water and the oil or fat phase. This creates additional stability. Monodiglycerides crystallize in the same different crystal modifications as do fats. Because they are part of the natural metabolic chain during digestion of triglycerides, there is no limitation on daily intake (Kayden et al. 1967). The suitability of the emulsifiers for certain types of emulsions can be described by the HLB-value (hydrophilic lipophilic balance; see also Chapter 8.9). For each type of emulsion, a certain HLB-value is necessary (Table 8.12).
8.2.5.3 Milk Components. In some countries, milk components are prescribed as ingredients. Most margarines contain milk solids. On the one hand, this can be understood historically from the attempt to imitate butter. During shallow frying, a sediment is built that is responsible for the browning (Maillard reaction; proteinlactose interaction). This property is wanted by most consumers. In addition, the finely dispersed proteins and lactose bind boiling nuclei when the water is evaporated from the melted emulsion. This decreases spattering. In addition, all milk components that have passed a souring step carry flavors, traces of butyric acid, ketones, lactones as well as diacetyl and its precursors. These substances work as flavors on the one hand, and at the same time, they mask off-flavors that arise during long storage of the margarine. Milk proteins also reduce the tendency of the fat to oxidize during frying. 8.2.5.4Acids. Acids have to fulfill several tasks. On the one hand, they lower the pH value, improving bacteriological stability. In addition, they create a better, fresh taste. The use of lactic acid gives a peaked, fresh taste. Citric acid is a milder acid with the additional benefit of binding metals such as iron in a complex, which tremendously reduces the sensitivity of the oil to autoxidation.
8.2.5.5Salt. Salt has two functions. One is to decrease the microbiological sensitivity; the other is to act as a flavorer. Salt content differs greatly from country to
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Fats and Oils Handbook
country. In Middle Europe, it is -0.2%; in the UK, it is much higher and in some overseas countries it can go up to 3%. One explanation lies in different eating habits. People in different countries are used to different salt levels of the initial prototype product butter; this ranges from the mild, unsalted Danish type to the heavily salted New Zealand type. The other role for salt results from its bacteriostatic behavior. In an aqueous solution of more than 10% salt, the activity of microorganisms is completely stopped (Ney 1988). In margarines with salt contents >2% product weight, this value is reached in the aqueous phase because the water content of margarine is 20% at maximum. In addition to these properties, salt levels ~ 0 . 2 % work as an antispattering agent during shallow frying. 8.2.5.6 Flavors. The flavor cocktails used in margarine making work as flavors and flavor enhancers; they also mask off-flavors. The flavors used depend on the geographical region, i.e., the local taste, and can range from bland to over-buttery to cheesy. If butter is normally slightly rancid in the respective country, this can also be reflected by the flavor notes used. Dosage also is done according to local preference.
8.2.5.7 Preservatives. Preservatives are rarely used in 80% fat margarines in countries with moderate climate, households equipped with refrigerators and welldeveloped logistic chains. In reduced-fat margarines, they are not necessary for production, but are needed to protect the product during open shelf life. Detailed information on preservatives is given by Luck (1984). 8.2.5.7.1 Benzoic acid. Benzoic acid works as a preservative in the undissociated form only. A minimum acidity is necessary therefore to block dissociation and to dissolve the acid from its salts when benzoates are used. The dissociation constant is 6.46 x 10-5 (Bosund 1960 and 1962), which means that the pH that is reached applying lactic acid is already sufficient. However, the pH of common margarine is only a little lower than that needed to ensure the efficacy of benzoic acid. Above that, the distribution coefficient between the fat and water phase is very unfavorable. The working mechanism of benzoic acid is based on the inhibition of enzymes belonging to the acetic acid cycle. It also inhibits oxidative phosphorylation as well as the citric acid cycle and has a negative influence on cell walls. In butter, benzoic acid (cO.OOl%, Rudischer 1959) can be found naturally, stemming from the fodder. This amount, however, is not sufficient for preservation. Benzoic acid is not allowed in all countries. When it is used, the amount is usually 10.1%.
8.2.5.7.2Sorbic acid. Sorbic acid usually is allowed up to 0.12%, but the amount used is normally lower. Sorbic acid is -50% more effective than benzoic acid and is used mainly in reduced fat margarines. The distribution coefficient between the oil and water phase is favorable. In the human body, it decomposes into water and carbon dioxide.
Fat as F o o d
747
The working mechanism of sorbic acid is based on the inhibition of enzymes of the carbohydrate cycles and the citric acid cycles (Azukas 1962, Rehm and Wallhofer 1964 and 1967, York and Vaughn 1964). Sorbic acid forms covalent bonds with SH-groups of the enzymes (Marsoadiprawito and Whitaker 1963), thus inactivating them. In addition, it has negative influence on the cell walls (Eklund 1980 and 1985). Furthermore, undissociated acid infiltrates the cell, and 40% of the enzymes are undissociated at a pH of 3.15. Because the dissociation constant is 1.73 x 10-5, sorbic acid also operates in ranges of low acidity. Detailed information on its mechanism to preserve margarine is given by Becker and Roeder (1957). 8.2.5.8 Thickening Agents, Stabilizers. In half-fat margarines or margarines with an even lower amount of fat, the emulsion on its own is no longer able to stabilize the product. Therefore, thickening agents or stabilizers, (for example, gelatin), are used to stabilize the water phase. A good overview of possible thickening agents is given by Trudso (1988). An overview of thickeners or stabilizers that are allowed for half-fat margarines in some countries is given in Chapter 8.2.10.
8.2.5.9 Colorants. In Europe, margarines usually are not colored with artificial colors. Often, however, P-carotene is added; it dissolves in the oil to give a reddish color. In many countries, Bixin and Annatto are allowed in margarines. The addition of p-carotene is also allowed for butter and is used to color winter butter. If unbleached palm oil is used in the blends, a natural yellow-reddish color can be obtained by the carotenes without later addition. 8.2.5.70 Vitamins. Vitamins are added to almost all household margarines. In some countries, the addition at the level that is usually present in butter is mandatory. Usually, fat-soluble vitamins A, D and E are used. In geographical regions with deficiencies in water-soluble vitamins, vitamination with vitamins B and C is also common.
8.2.5.77 Water. Water usually stems from wells on the margarine factory sites or is taken from the municipal net. Water quality must be monitored constantly. 8.2.5.12 Air, Nitrogen. Some margarines and fats are whipped with nitrogen or air to soften the products (so-called soft margarines). In most countries, the gas used for whipping has to be declared on the ingredients list.
8.2.5.13Starch. Until some years ago, in some European countries, starch had to be added to margarine to enable adulteration of butter with margarine to be detected. This legal requirement stems from the last century, because current modem analytical techniques allow easy detection of adulteration without the addition of marker substances such as starch or sesamol. Starch has no function at all in margarine. On the contrary, it negatively influences its spattering behavior.
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8.2.6 Physical Properties
Margarine is plastic, which means that its internal repulsive forces are not sufficient to bring it back to its original shape when it is deformed under outer pressure. Kroll (1978) gives models for explaining the viscosity of plastic fats compared with a Newton liquid (Fig. 8.18). Because the inner structure of margarine can be softened under mechanical influence (e.g., kneading), the structural bonds are then destroyed so that only the molecular bonds between the crystals stay in place. Hardness and flow limit of margarine are closely connected. Hardness is expressed by the following equation:
where w is the weight of the cone of a penetrometer including the falling stick suspension, p is the depth of penetration (l/lO mm), and n is a constant (1.6 for butter, margarine and bakery fats.) The factor k depends on the angle of the cone. This dependency can be derived with a very high correlation coefficient in exponential regression from the given values. If it is double logarithmically plotted against k, a straight line results.
k = u . ab'
(U
= 6.2 . 106 and b' = -1.906)
[8.21
or
k = d a b (U = 6.2 . lo6 and b = 1.906)
[8.2a]
10 8 6 4
2
0 0
1
2
3
4
5
6
7
8
91011121314
Shear stress [N/m2] Fig. 8.18. Viscosity of a Newton fluid and two plastic fats (after Kroll 1978).
Fat as Food
749
The complete formula to calculate firmness then reads as follows:
where a = 6.2 . 106, b = 1.906 and n = 1.6 for butter, margarine and bakery fats. Given a penetrometer, only one variable @) is then left in the equation, i.e., the depth of penetration itself; all other variables can be reduced to a constant that is specific for this penetrometer. C-values are measured because of their importance for the functionality of some plastic fats (Table 8.13). To reach the above requirements, i.e., specific C-values that ensure the desired functionality of the margarine, special processing conditions have to be maintained that allow for controlled crystallization. If margarine is warmed up too much after p r e duction so that the fats crystals are partly or completely melted, uncontrolled crystallization can occur during cooling. The C-value of such margarine can deviate enormously from the one that has been manufactured by the producer under these special processing conditions. Another reason for totally different C-values after recrystallization is that the amount of mixed crystals can change, and pure triglycerides may crystallize. Usually this leads to a deterioration in melting behavior. The crystal modification can also change. During production, the aim is to obtain p' crystals (-1 pm long and 0.25 pm thick). At a certain temperature, there is a transition to p crystals, which have a much higher melting point (see Chapter 2.3.1) and are larger (20-30 pm). The coarse crystals give a sandy impression on the tongue. To retard p-crystal formation, crystal inhibitors can be used (Krog 1977); an example is sorbitan tristearate, which is legal in Canada. However, careful blend composition, processing and good logistics make their use unnecessary. The physical properties of margarine are also determined by the amount of solid triglycerides that margarine has at a certain temperature. These values can deviate from the typical values that are shown in Figure 8.19. Heart health margarines with a guaranteed high amount of polyunsaturated fatty acids (e.g., in Europe, Becel) are much softer that other margarines due to their fatty acid composition. Hardness of margarine is determined by many factors. If it crystallizes in the pack, i.e., after production, this results in a much harder product TABLE 8.13 Importance of C-Values for the Plasticity of Fat Emulsions C-value (dcm2) 1500
Properties Not spreadable because too soft ; flows away Very soft, just spreadable Very spreadable, good plasticity; also spreadable at refrigerator temperatures Hard, but still spreadable Very hard, barely spreadable; not spreadable at refrigerator temperatures Too hard, no longer spreadable
Fats and Oils Handbook
750
Solids content
80
[%I
1
0
5
10
15
20
25
Temperature
30
35
40
45
[“C]
Fig. 8.19. Solids content of typical margarines.
because the margarine can no longer be overworked mechanically. Compositions that are slowly crystallizing or those that are not sufficiently cooled have a special tendency toward postcrystallization. This is shown in Figure 8.20 for a fat that is completely crystallized in the scraped surface heat exchanger and a fat that has a high rate of postcrystallization. The share of fat (m.p. 58°C) in the fat/oil mixture Stress [
/kPa]
(a) fully crystallized in cooler 25
(b) with high postcrystallizationi
--f
5
01 0
I
I
I
1
2
I
,
I
3
4
5
5
6
Strain [ 10. ?In(ho/h)]
Fig. 8.20. Stress-strain curve of a fully crystallized fat and a fat with high postcrystallization (courtesy of Unilever, see also Heertje e t a / . 1988).
Fat as Food
751
of the above trial was 14%. When leaving the processing unit, it was 100% crystallized in case (a) and only 40% in case (b), which means that 60% of the total fat blend postcrystallized. This leads to an inhomogeneous structure with long (p-) crystals. In such a structure, fewer bonds can break under stress than in the case of the fully crystallized blends. Of course the fat composition itself also has a large influence on hardness. The lower the oil content, the harder the product. As noted before, primary bonds between the crystals stay intact even during the mechanical overworking; secondary bonds are broken up. Strong primary bonds therefore contribute greatly to hardness. Figure 8.21 shows typical C-values for German margarines of the composition types shown in Figure 8.16. The higher the shear stress during overworking, the more the continuous structure turns into a grainy structure. This has been proven by Heertje et al. (1988), who recorded scanning electron microscope pictures of the crystal structure. Air or gas, whipped in intentionally or unintentionally, also influences hardness. Proportional to the amount of gas, the number of crystals per volume decreases; margarine becomes softer. By comparison, for butter, churning leads to an air content of -5% (Mulder and Walstra 1974); soft margarines contain 10-20% air or nitrogen. 8.2.7 Margarine Production
Production of margarine consists of some principal steps starting from refined oils and fats. These principal steps are shown in Figure 8.22. Apart from the fat blend, the properties of the finished product are really influenced only by steps C and D.
Fig. 8.21. C-values of typical German margarines (after Schleenvoigt 1989).
Fats and Oils Handbook
752
OivFet blend
I
A B
Mixing
Ingrsdii I Emulsifying
I C @
Cooling
stomge
PortayataHkstknand hardening @ StapaCandDinmany
Margarine
different conRguntknr
Fig. 8.22. Principal steps of margarine production.
The composition of the ingredients has only a minor influence. Posthardening after packaging cannot be influenced and is based on the properties that are inherent from steps C and D.
8.2.7.7 Ingredient Preparation. There are two extreme variations in the way that ingredients are prepared and added. On the one hand, it is possible to prepare single aqueous or oily solutions of single ingredients and then blend them with the fat blend, the water and the milk by means of a multihead proportioning pump (proportioning process); the mixture is then emulsified by static mixers built into the tubes. On the other hand, the complete margarine composition including fat and water phase and all ingredients can be mixed in one batch from which the emulsion is then directly processed through a scraped surface heat exchanger (premix process). In between those two extremes, all intermediates of ingredient and emulsion preparation are possible, and there are examples in the industry for all of these intermediate steps. Using the premix process, the water content of the emulsion is checked only once per batch (continuously good agitation assumed). If proportioning pumps are used, the water content has to be checked at intervals on a statistical basis over the period of production. The aqueous phase should be pasteurized. This can be done with the whole emulsion as well as with single solutions. Soured milk as such cannot be pasteurized because the protein would coagulate and become sandy. This would be possible only after the addition of protection colloid. However, pasteurization is not necessary if the milk has been soured under hygienic conditions and the source sweet milk has been pasteurized. This means that the soured milk has the same bacteriological status as a postpasteurized soured milk except for the souring cultures. These stay alive, but they are no longer active in margarine because the temperature is too low and the size of the water droplets does not allow for it.
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753
8.2.7.1.7Milk souring. As a source for the production of soured milk, pasteurized fresh milk or milk that is reconstituted from milk powder and water is used. The milk is pasteurized and soured with cultures such as Streptococcus lactis or S. cremoris to an acidity of about 40"SH. Souring can be carried out with parts of a mother culture that is inoculated or by using deep-frozen or freeze-dried cultures purchased from a third party. Cultures are reproduced according to the scheme that is shown for butter (see Figure 8.3). Souring itself also follows this pattern. Ripening of the milk takes about 12 h. The soured milk is stored in hygienic, cooled batches and transported via a piping system. Cleaning of this system requires special care. When proportioning pumps are used, milk is dosed via a dosing cylinder. In addition to bacteriological souring, there is also the possibility of chemical souring. For that purpose, citric acid or lactic acid is added to the sweet milk. The influence on the milk protein is similar to bacteriological souring; however, none of the flavors that develop in bacteriologically soured milk will be present. If milk, buttermilk or whey powder is used, it is dissolved in water and stored in a batch. For cleaning, there are the same requirements as for milk. 8.2.7.7.2 Water-soluble ingredients. The water-soluble ingredients are prepared singly or as a mixture. Usually, they are rinsed into the storage batch by circulation over a Venturi-tube or collected from mother solutions. Such solutions can also be purchased as such (e.g., brine). 8.2.7.7.3 Oil-soluble ingredients. Oil-soluble ingredients are dissolved either in a single oil or in the relevant margarine fat blend. In both cases, the amount of fat from the prepared ingredients has to be taken into account when calculating the total composition. If one-oil margarines (e.g., sunflower margarine) are produced, the oil for dissolving the ingredients must be the same oil as for the margarine, unless legislation allows for a certain amount of foreign triglycerides. To avoid crystallization of the emulsifier (monoglycerides and monodiglycerides), the ready-prepared ingredients mixture has to be stored warm (T > 55°C). Depending on the ingredients, it may also be necessary to agitate to avoid sedimentation. 8.2.7.7.4 Oil/fat blend. There are two principal possibilities for preparation of the fat blend. One is to blend fully refined oils and fats (see Chapter 7.4); the other is to compose the blend from crude oils and to refine the complete blend. Of course, it is also possible to combine both alternatives, which means blending fully refined oils and fats with fully refined fat partial blends. The assembly of the oil in a batch is done gravimetrically over a composition weigh scale or volumetrically over a rotary piston meter or a mass flow meter. With today's methods of electronic process control, it is possible to compensate for the volume differences of oils and fats of different temperature so that flow meters can provide the same accuracy as weigh scales if the amounts are not too small.
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754
TABLE 8.14 Hydrophilic Lipophilic Balance (HLB) Necessary to Emulsify Certain Oils and Fat9 Water emulsified with
Oil in water
Water in oil
6
3 5 3 4
Cocoa butter Corn oil Cottonseed oil Palm oil Rapeseed oil Soybean oil Beef tallow
a 6
7 7 6 6
4
3 3
aSource: Griffin (1979).
Bacteria cannot grow in the oiYfat composition. It is therefore not necessary to pasteurize the oil blend. Pipes should be flushed regularly with hot oil to remove the fat sediments on their walls. In fact, it is important to exclude water from these vessels and pipes to maintain quality. 8.2.7.2 €mu/si&ing. To emulsify the oil and water phases, they have to be mixed care fully. Depending on the process chosen, this is done at least partly in the premix batch or later in the proportioning pump. Usually additional static mixers built into the pipes complete the task. Emulslfying is easily accomplished because all margarine compositions contain sufficient emulsifiers that support it. At first, an emulsion of the type oil in water is built; this is converted by phase inversion into an emulsion water in oil. Table 8.14 shows the HLB-values that are necessary for different oils and emulsion types. Lynch and Griffin (1974, Table 8.15) compared the emulsifying properties of different apparatus that can be used. Apart from static mixers that promote emulsification in the pipes, only scraped surface heat exchangers (SSHE) are presently well suited for margarine making. They alone guarantee sufficient heat transfer to ensure cooling down of the emulsion and removal of the heat of crystallization. TABLE 8.1 5 Properties and Performance of Emulsification Devicesa ~
Device Anchor stirrer Paddle stirrer Scraped surface heat exchanger Disk mill Homogenizer Colloid mill
~~
Agitation speed
Carried in mechanical energy
Suitable for . . . viscosities
Heat transfer
low medium medium
low low to medium low to medium
high medium to high high
medium poor very good
high low high
low low low
low to medium low to high low to medium
medium poor
aSource:Lynch and Griffin (1974).
poor
Fat as food
755
Dosing the ingredients before emulsion preparation can be done via low- or high-pressure pumps. If low-pressure pumps are used, the SSHE/crystallizer combination itself has to be fed via a high-pressure pump. 8.2.7.3 Cooling (Crystallization) and Working of the Emulsion. To achieve the desired consistency, the margarine fadoil blend must of course be properly composed to achieve these properties. Within the given limitations of the specific fat blend, the consistency of the margarine can be heavily influenced by processing. In principle, processing is a sequence of cooling steps that start crystallization at different temperature levels, i.e., holding zones that allow for further crystallization without cooling and application of mechanical stress to break up secondary bonds to the degree desired. Heat has to be deducted as well to cool down the emulsion and to remove heat of crystallization. Fats and oils crystallize relatively slowly, some very slowly. If slowly crystallizing fats such as palm oil at 60°C are set in a bath of 0°C and are cooled down, it takes up to 2 h until they are fully crystallized. For quickly crystallizing fats, for example, palm kernel oil, the same process takes only -10 min (see Fig. 8.23). If the cooled mixture is agitated (compare lines A and B in Fig. 8.23), crystallization occurs much more quickly, in this case -10 times more quickly. Except for palm oil compositions, a fat blend that is continuously scraped off (i.e., agitated) in SSHE and crystallizers takes -7 min to fully crystallize given cooling medium temperatures below -10°C and an inlet temperature of -40°C. In the following, two different processes for margarine making that are still applied today are described. The chum-drum process that was the standard method
25
Agitated
,B-
20 -
, f C
A
--
L _ _ _ _ _ - _ - - - - - - - - - - -
Hardened fish oil/ soybean oil (50:50)
I I I
15 -
Palm kernel oillsoybean oil (40:60)
Fats and Oils Handbook
756
TABLE 8.1 6 Weaknesses and Strengths of Scraped Surface Heat Exchangers Compared with Cooling Drum9 Type of product
SSHE
Drum
Normal household margarines Soft household margarines Half-fat margarinedlow-fatspreads Bakery and cream margarines Puff pastry margarines White fatdshortenings Water in oil emulsions (high water content)
+++ +++ +++ +++ ++ +++ +++
+++ + + +++ +++ + +
+++ very good; ++ medium; + poor. aSource: Crindsted.
until the 1950s and a process that was introduced then and is used almost exclusively today, namely, the process via scraped surface heat exchangers. Today, the cooling part of the churn-drum process, i.e., cooling over a drum and working in a complector, is used only for special margarines. The scraped surface heat exchanger is much more universal. It also has its weaknesses for specialized products (Table 8.16); however, these do not play a large role.
8.2.7.3.7 Churn-drum process (discontinuous). Up to -1955, margarine was emulsified in churns and subsequently cooled down in cooling drums. The socalled chum-drum process was applied (Fig. 8.24). Chums are cylindrical vessels with a double housing for cooling. They are equipped with a stirrer or beater. These beaters consist of flat, perforated shafts that are rotating against each other, driven by two motors. The rotational speed lies between 30 and 60 rotationdmin. The vessels, which can hold up to 4OOO L, are used only to a maximum of 70%of their volume. The emulsion is cooled (also by addition of ice water). Then it is brought onto the cooling drum in a layer 0 . 1 4 2 5 mm thick. The cooling drum is cooled from the inside to -12 to -18°C with liquid ammonia or brine. It rotates horizontally and the cooled margarine is scraped off after 300" rotation. Margarine is then stored for further crystallization in open vessels and is subsequently overworked mechanically to improve its structure (breaking of secondary bonds). Later, it is packed. Using the so-called drumcomplector process (complector is a brand name of the Gerstenberg company) (Fig. 8.25), the line starts with the churns (A) and (B) used alternately to make the process semicontinuous. The cooling drum (H) is fed with churned product via the pipe @) and scraped off as flakes with a knife (Qafter having passed through the drum. Via a buffer (K), these extremely thin margarine flakes are conveyed into the convector (L-T) after being allowed to crystallize for some minutes in a buffer (K). The complector itself consists of two screws, (L) and (M),which convey the margarine into a kneader 0 where it is overworked. The apparatus is kept
Fat as Food
757
Fig. 8.24. Churn for margarine production (after Stuyvenberg 1969).
under light vacuum. Complectors have a throughput of up to 4.5 ton/h. Today, only special (mainly bakery) margarines are produced via cooling drums. 8.2.7.3.2 Scraped surface heat exchangers process (continuous). In 1938, margarine production was revolutionized by an invention of the Votator company. It is a process that for the frst time allowed continuous processing of emulsions in a scraped surface heat exchanger. Single-ingredient solutions and the fat blend are combined via a multiproportioning pump, emulsified via static mixers and pumped into the scraped surface heat exchanger where the combination is cooled, crystallized and overworked. In the case of the premix process, a simple pump to convey the emulsion is needed. These SSHE (A-units) in combination with crystallizers (C-units) are well known under different brand names (Votator, Kombinator, Perfector, Unitator). The sequence of coolers and crystallizers in the plant depends on the oil and fat composition and the product properties desired. Figure 8.26 shows an arbitrary example of such a combination, suitable for producing a household margarine, SSHE consist of a tube that is cooled down from the outside to -25°C (liquid ammonia, frigen, brine). This tube has a maximum length of 3 m (10 ft.), and its
Fats and Oils Haihdbook i
758
Fig. 8.25. Margarine line for the drum complectwprocess.
inner diameter is up to 250 mm (10 in.), allowing for good heat transfer. In this tube is a shaft, leaving a space of 7-12 mm (0.3-0.5 in.) between the shaft and the tube's inner wall. The shaft rotates at high speed (up to 800 rotations/min). The margarine emulsion is pumped through this annular space. It is cooled on the inner surface of the tube and solidifies (Fig. 8.27). Emulsion tp
tp = Product temperature -4O'C
Scraped cooler
tp
- 28.c
Scraped cooler
tp
-1O'C, 3OC-600 min-i
- W C , 300-600 min-i
- 18'C
Crystallizer
-
B Unit
Margarine, packed
100-200 min-i
for slowly crystslliiing blends
Fig. 8.26. Margarine production with scraped surface heat exchangers SSHE (number and sequence of the tubes are an example only).
Fat as F o o d
759
Fig. 8.27. Cross section of a scraped surface heat exchanger and a crystallizer. The number of A- and C-units and their sequence depend on the margarine composition and the plant’s throughput. Because the size of the cooling tubes is limited by physical constraints (handling and modular composition of the plant), the cooling area needed has to be achieved by a series of units. Well controlled cooling creates many crystal nuclei of the p’ type, and crystal growth is slow. To ensure overworking of the solidifying emulsion and prevent the tube from being blocked by solidified product, the shaft that rotates in the tube has two to four rows of knives. These knives are flexible so that, driven by the centrifugal force, they touch the inside of the tube when rotating and scrape off the cooled solid margarine emulsion. The cooling tubes of the plants are also called A-units. To enable crystallization of the emulsion, A-units are used in combination with so-called C-units (crystallizers). Coolers and crystallizers are used in different configurations that depend on the fat blend and the product properties intended. Applying blend-specific cooling temperatures on the one hand ensures that the heat of crystallization is removed; on the other, controlled crystallization is guarateed. Wild crystallization must in any case be avoided because it can lead to uncontrolled changes in the product properties. A crystallizer is also a tube, containing an inner rotating shaft. However, in comparison with the diameter of the shafts in A-units and also to the diameter of the tube, its diameter is very small. That means that the opening between shaft and tube is very large (100-200 mm; 4-8 in.). Three rows of pins that are regularly distributed on the tube (stator) jut out from the tube wall interior. The shaft (rotor)
760
fats and Oils Handbook
also carries two rows of pins. These rotate with the shaft through the gaps left by the pins fixed to the tube. The sheer stress from overworking the product ensures the homogeneity of the emulsion and its plasticity. Crystallizersare not cooled (Fig. 8.28). Because of its low volume, the residence time in an A-unit is only 5-10 s. Because a crystallization time of -7 min is needed, the plant has to be supplemented by parts with higher residence times. To pass through a C-unit takes the emulsion -2-3 min. To ensure sufficient crystallization time for slow crystallizing blends, holding tubes (B-units) can be added at the end of the SSWcrystallizer combinations; their length and volumes are adjusted to the blends that are to be processed. An impression of a total plant (Kombinator, trademark of SchrMer company) with scraped surface heat exchangers and crystallizers is given in Figure 8.29. The emulsion is pumped into the plant at -40°C. There is a rule of thumb that 2.0 ton/h of normal household margarines can be produced per square meter (per 10 ft2) of cooling surface. Thus, the number of scraped surface heat exchangers and crystallizers depends not only on the composition and the properties of the product but also on the output of the plant. In addition to the heat of crystallization of the fat (-160 Idkg), the specific heat of the oil, the fat, the water and the ingredients has to be removed. In addition, the problem arises of how to dissipate the heat of friction and the mechanical heat equivalent of the rotational work. The emulsion leaves the plant at 10-20°C. From these figures, configurations for plants from two well-known European manufacturers can be derived (Table 8.17). The volume of a processing unit with a throughput of 3.5 ton/h is -360 L, accounting for a residence time in the unit of -400 s. The internal pressure rises to 35 bar. The most recent Kombinators, for example, allow throughputs of more than 10 ton/h and pressures of up to 120 bar. These plants are also available for sterile processing, allowing sterilization with steam of 140°C. For some special margarines, usually for bakery margarines with high amounts of palm oil, B-units that allow additional residence time are added, thus
Fig. 8.28. Crystallizer with shaft drawn (courtesy of Schrijder, Lubeck).
761
Fat as Food
Fig. 8.29. Schematic view of margarine processing unit (courtesy of Schroder, Lubeck).
ensuring a more complete crystallization. Such tubes can have a length of several meters. Apart from the process described above, it also possible to divert part of the emulsion stream just before it enters the B-unit. This part is then fed into the uncooled emulsion before its entry into the first A-unit (recirculation process). TABLE 8.1 7 Configuration of Processing Lines Consisting of SSHE and Crystallizers (Line Layout from Two Major European Manufacturers)
Number of A-units Number of C-units Cooling area (m*) per A-unit total A-units per t o n h installed per ton/h needed Installed electrical capacity (kWh) A-units C-units Total Size of total unit (mm) length (incl. drive) width (incl. NH,-unit) height
3.6 t o n h
7.2 t o n h
10.5 t o n h
2-3 2
4-5 2
6 2
0.80-1.05 2.1 -2.4 0.55-0.66 0.5
0.80-1.05 4.0-4.2 0.55-0.66 0.5
0.80-1.05 4.8-6.3 0.55-0.66 0.5
50-52 20-22 70-74
95-1 04 20-22 115-126
125-1 50 20-22 145-1 52
3300-3800 1450-2 100 22 OO-3000
3300-3 800 145c-2 100 2900-4700
3300-3800 1450-2 100 35004000
762
Fats and Oils Handbook
When fed into the warm emulsion, it is melted down with some crystal nuclei remaining that inoculate the emulsion to achieve better crystallization. However, this process is applied only rarely today because it has few advantages. In the event of a stoppage in the packaging line with no further product stream, the scraped surface heat exchangers would be immediately blocked by rock-hard solidified emulsion. In this case, it would be necessary to warm it up in order to melt down the solid blocking product. This means that the unit has to be emptied of ammonia, filled with hot water, the water then removed and the unit refilled with liquid amme nia. To avoid this time-consuming procedure, the throughput of the SSHE is drastically reduced in case of a packaging machine breakdown. Via a valve placed between the last SSHE or crystallizer and the packaging machine, the reduced amount of margarine leaves the machine. It is called rework and is either collected in a vessel (if a premix system is applied, this may be the premix vessel), remelted and later dosed again into the stream of warm emulsion or it is continuously reprocessed. If the rework is remelted and dosed into the system just before the entry into the first SSHE (thus circulating), the process is called closed rework. Figure 8.30 shows a Kombinator plant, i.e., a plant consisting of A-units and C-units. Usually the processing plant is set up according to the capacity of the packaging line(s). The largest packaging machines that are common today are six-lane machines with 360 tubs per minute. The equivalent processing units therefore have a throughput of more than 10 ton/h. 8.2.7.3.3 The influence of temperature, residence time and rotational speed. Three parameters, namely, temperature, residence time and rotational speed influence the product properties. In the cooling units (A-units), temperature and residence time are coupled to each other, because higher temperature and longer residence time have the same effect as lower temperature and shorter residence time. The circumstances in the C-units (crystallizers) are somewhat different because they are not cooled; this reduces to two the degrees of freedom that can be influenced. Because the temperature difference between the SSHE-surface and the emulsion is limited as a result of the limited heat transfer that can be achieved, sufficient cooling area is essential. As noted before, a rule of thumb states that 0.5 m* of cooling area is needed to produce 1.O ton/h of household margarine. To ensure good heat transfer, it helps that the scraping knives in the A-units are metal; this improves heat transfer between the knives and the surface of the cooling tube and also between the knives and the emulsion passing through the Aunit. The disadvantage of metal knives is that abrasion is higher than with plastic. The number of scrapings A that happen per minute in the cooler is determined as follows: A=K.R
~3.41
where K is the number of rows of knives of the rotating shaft and R is the rotational speed (min-'). Again, as a rule of thumb, A should be -1OOO. Because A is a
Fat as Food
763
Fig. 8.30. Photo of Schroder Kombinator (Trademark of Schroder Company, Lubeck).
measure for the shear stress that the cooled emulsion is exposed to, it very much influences the properties of the final product. 8.2.7.4 The Whole Process in an Overview. Figure 8.31 shows the complete margarine manufacturing process as it would be carried out with a five-tube combination of A-units and C-units that are arbitrarily composed.
8.2.8 Packing Today, margarine is immediately packed after it has left the processing unit. The packaging material’s task is to give optimal protection to the product during transport, shelf life and use. For household margarine, an appealing design would improve sales promotion. In addition to the mechanical protection that the product needs as it leaves the processing unit in a soft state, protection from light and oxygen is necessary. Beyond that, the packaging should be as water tight as possible to prevent margarine from drying out. Surface water evaporates from the product
Fats and Oils Handbook
764
I,
w
c
Ic.dho.rarm PastwrLing
+
knit
I
-
+
Cryrtrflizing
Gunk
Fig. 8.31. Flow chart of margarine production.
Fat as Food
765
15pm PETG Copolyester lOpm ABS = Acrylbutadienstyrene 250pm HIPS = High Impact Polystyrene
Fig. 8.32. Possible substitutes for PVC in margarine packing.
1Ovm PETG
15pm
until the head space between product and packaging (lid) is saturated. If the pack is tight, drying out is low. If not, water vapor can escape the pack so that it evaporates more and more from the product surface. A dark yellow surface, the characteristic color of the dried out fat phase, remains. Kroll (1978) demonstrated the dependency of drying out on the duration of storage. Polyvinylchloride (PVC), which was used mainly until the late 1980s, has very low water and oxygen permeability (see Chapter 8.4). In addition, it can easily be imprinted and is shape-retaining. Because of its bad environmental image, however, it has been replaced more and more by polypropylene, polyethylene and polyester as well as laminates. The properties of these substitutes (same material strength assumed-) are much worse. A five-layer laminate that was promoted as a substitute for PVC by different companies in the late 1980s (but was not successful) is shown in Figure 8.32. Table 8.18 demonstrates that some materials &e superior to PVC in single properties, but that PVC is paramount in the combination of very low water and oxygen permeability. The search for an equal substitute will have to continue. Preformed tubs or containers that are molded from a foil (form-fill-seal process) can be filled with margarine. The table also shows the forming temperatures. Furthermore, it is common to wrap margarine. The necessary consistency TABLE 8.1 8 Permeability of Different Materials Used for Packaging Permeability for Material strength 275 pm
Working temperature
PVC (polyvinylchloride) Material X Material strength 100 pm Hard PVC HIPS (high-intensitypolystyrole) ABS (acrylbutadienstyrene) LDPE (low-density polypropylene) HDPE (high-density polypropylene) PP (polypropylene) PA (polyacryl)
Oxygen (cmVmz) 32 94
Water vapor Ig/(d pack)] 0.083 0.12
("C)
krnV(n-12bar)]
[g4d crn2)l
70 70-90 95 80 90-1 10 120-1 40 120
30 1200 1000 1600 800 600 9
3 20 20 1 0.4 0.5 13
Fats and Oils Handbook
766
Marg/nnne
Coil of wrapper
(hard)
2Y Filling
c
%-
c
t
Folding dow
Wrapped margarine
a
to casepadtor
Fig. 8.33. Flow chart of margarine wrapping.
depends on the way of packaging. Tubs can be filled semiliquid. The same holds for wrappers if the wrapping foil is folded in the shape of a rectangular or square tub before filling.
8.2.8.7 Wrapper Machines. Parchment remains the wrapper material in some countries, but now paper and/or plastic-coated aluminum are mainly used; plastic laminates are also used. In the past, wrapped margarine was produced exclusively by pressing a hard block of margarine from the packaging machine and wrapping the wrapper around it. The margarine itself then is the forming element (Fig. 8.33). In later machines (Fig. 8.35), the foil enters the machine (A) and is pressed by a piston through a connecting link, thus forming a hollow squared block that is open to the upper side. Over the dosing heads (C), margarine (or shortenings or butter) is filled while the pack is lifted toward those dosing heads. The pack is closed by folding in (D), and the fold stamped flat (E). The product is expelled via F. Different folds are possible (Fig. 8.34). The characteristics of a wrapper machine are given in Table 8.19. If margarine is wrapped, the packaging machine is fed directly by the processing unit. For butter, this is usually collected in a trough from which it is conveyed by a screw into the machine. Such packaging machines exist up to 2 kg per pack; twin machines have been built up to 2 . 250 g. The above-described machine is suitable for all products that can be filled in semiliquid form because the material must be distributed evenly in the preformed pack. 8.2.8.2 Tub-Filling Machines. In Europe, shortenings are usually sold in wrappers, whereas the majority of household margarine is produced in preformed tubs. Principally there are two different types of tub-filling machines, stroked machines
767
Fat as Food
Fig. 8.34. Bottom and side folds in margarine wrapping (courtesy of Benhil, Dusseldorf)
and continuous machines. With stroked machines, the tubs stop under the dosing head for the filling. All other operations (Fig. 8.37) are then also carried out with each stroke. With continuous machines, filling takes place by means of a dosing head that swings with the tub while this is conveyed on the belt. The same is true for all other stations of the machine. Two types of stroked machines exist, rotary fillers and lane fillers. Rotary fillers have all stations mounted on or above a rotating round plate that carries the tub from station to station. In lane fillers, all stations are placed on a straight line one behind the other. The latter has the advantage that the capacity can theoretically be extended to the infinite, whereas rotary fillers consume much less space and are much easier to handle. Because of the high labor cost, there is a strong move toward lane machines in industrialized countries. TABLE 8.19 Technical Data of a Wrapper Packaging Machine (Type Multipack 8362, Trademark of Benhil Company) output (250-g packs) Pack format, minimal maximal Width of pack material roll Machine size (L x W x D) Weight Energy demand Compressed air (8 bar) Main drive Vacuum pump Transport drive
(packs/m in) (ton/h)
12C-240 of 6CL250 g 1.8-3.6 60 x 60 x 21 100 x 75 x 30 1 10-242 (double for twin-machines) 3000 x 1800 x 1950 4600 (net) 10 4.5 0.37 0.25
768
Fats and Oils Handbook
Fig. 8.35. Wrapping machine (Type Multipack 8362, trademark of Benhil Company Dusseldorf; courtesy of Benhil).
The most important part (for the product) is the dosing system. On the one hand, dosing is responsible for accuracy in product weight (underfilling must be avoided, overfilling causes economic damage); on the other hand, the dosing head is the site at which the pasteurized products leaves the hermetic piping system and comes in contact with the environment. Great care has to be taken in the construction of the dosing unit to ensure that back-growing infection is avoided and that the unit is easily cleanable, preferably by cleaning in place (CIP). Filling takes place in the following steps (Fig. 8.36): 1. Starting position after filling of a tub 2. The valve rod closes the outlet, the margarine flow pushes the piston upwards 3. The required quantity of margarine is in the piston chamber 4. The valve rod closes the upper valve seat, the outlet is opened 5 . The margarine flow pushes the piston downwards, the margarine is pressed out of the piston chamber and through the outlet into the tub
Fat as Food
IProduct infeed 3 Piston rod 5 Cutting device 7 Bypass valve
769
2 Valve rod 4 Outlet nozzle 8 Cleaning connection 8 Cleaning pipe
Fig. 8.36. Principal positions of margarine dosing heads (courtesy of Harnba, Neunkirchen)
6 . Position after filling of the tub 7. Margarine filler in cleaning position, outlet nozzles and cutting device are replaced by a cleaning pipe A complete tub filler is shown in Figure 8.38 with the technical data given in Table 8.20. Lids (A) and tubs (B) are conveyed into the machine. If the machine is fed by only one lane of tubs and lids, this one lane has to be split into as many stacks of tubsflids as the machine has lanes. The tubs are denested from the feeding
Fats and Oils Handbook
770 Tub from stack
I Soparati:
I
single tub
lnwrting into cell pkte
tauoff
I
C
Q
I
checking whaher p m n t
heated w i n
I Sealing lid
1
t
Cover lids from st&
=$
to caw packer
Fig. 8.37. Flow chart of tub margarine packing.
stack. The dosing heads are fed with product via a compensator (C). A probe (D) tests whether a tub is inserted and, if so, activates the filler. If required, a lid foil is laid on (E) and pressed on (F), or the tub may be sealed instead. Lids fed via (A) are separated into the respective number of stacks. The tubs are closed with the lids (G) and the finished packs expelled (H). Each dosing head can be adjusted individually via a motor. Thus they can be steered via a check weigher that is integrated into the machine, allowing the tubs of every lane to be filled with the statistically exact weight. For sensitive margarines with high water content, these machines are also built hermetically closed to allow running under sterile con'ditions. Tubs fed are sterilized with hydrogen peroxide, and the clean chamber housing the dosing heads is flushed with sterile air. All new machine types are equipped for CIP. In tropical countries, ambient temperatures may be so high that margarine melts. In these cases, it may be packed in tins. In countries with such low spendable income that only a day's need can be purchased (day-laborer), it is also sold in plastic sachets of 50 g, for instance. 8.2.8.3 Packing of Margarine for Artisanal and Industrial Use. Margarine for industrial or semi-industrial purposes (e.g., feeding centers or bakeries) is also filled into boxes with inserted plastic bags. Semiliquid margarines for feeding centers are also delivered in buckets; puff pastry margarine is produced in sheets that can easily be used.
Fat as
food
771
Fig. 8.38. Four-lane tub filling machine (Hamba Type B K 8004 M, courtesy of Hamba, Neunkirchen).
Machines for packing bakery margarines are therefore constructed differently. On the one hand, their consistency is much firmer; on the other hand, they are packed in bars or sheets of 2-5 kg each. Usually, slowly crystallizing blends require a B-unit (holding tube) between the cooler and the packaging machine, thus allowing for further crystallization time. Figure 8.39 shows a machine to pack 5-kg blocks. In the background, the long Bunit can be seen. The wrapper foil is hung up on a roll (A) and is wrapped around the margarine block that is extruded from the B-unit (rectangular profile) and is then cut off. The machine output is automatically adjusted to the throughput of the processing and the B-unit. The weight accuracy of the wrapped margarine blocks is f 0.1%. The length of such a machine is 1.8 m (without B-unit), compensating cylinder and dosing unit. In total, the length of the filling unit is 4.5 m. The dosing
Fats and Oils Handbook
772
TABLE 8.20 Technical Data of a Tub Packaging Machine (Type Bk 8004 M, Trademark of Hamba Company) output
(500-g packs) Machine length Including tub feeder Energy demand Compressed air (8bar) Main drive Vacuum pump Dosing adjustment Steering
(packs/min) (to&)
25C-5OOg 7.5
(mm) (mm)
4350
(Nm3h)
20
(kW (kW (kW) (kW)
5500
4.0 1.85 0.13
2 .o
heads can be mounted and adjusted respectively for blocks of 1-25 kg with a maximum speed of 25/min. Energy consumption of a machine that weighs 2.3 ton is 5.8 kW electrical energy and 8 bar compressed air for the pneumatic steering. The throughput depends on the weight of the individual packs and is 5.5 tonh (12 ton/h) with 2.5-kg (20-kg) blocks; 2.5 tonh (4.5 ton/h) can be achieved when packing 1.0-kg (2.5-kg) sheets of margarine.
Fig. 8.39. Packaging machine for bakery margarine bars (Type BKS of Bock & Sohn -Company, Norderstedt; courtesy of Bock).
Fat as Food
773
For the last-mentioned, the dosing head is mounted vertically to the machine (Fig. 8.40). Paper is fed from roll A, and the wrapped block leaves the machine to the front of the picture. This machine is 3.3 m in length, 2.4 m in width and weighs 1.6 ton. 8.2.9 Special Margarines
Margarines for special purposes differ in their properties of use, characterized by their C-value and their solids content (Fig. 8.41).
8.2.9.1 Cream Margarine. Usually, cream margarines have low melting points (30-34°C). They are used for cake fillings and decoration and must be whippable, i.e., hold the air whipped in, which is achieved mainly by the enormous number of fine crystals @'-type). In spite of their low melting point, they must have a high fat content. Despite that, a quick melting in the mouth (steep dilatation curve) is required, combined with a cooling effect. Coconut oil is ideal for such products. The good creaminess of such margarines is based on quick crystallization. Therefore, interesterified lard is also a good starting material (see also Chapter 6.4.5). The product must be easily stinable in bakeries at an ambient temperature of -22-26°C. The composition of the fat blend can be as shown in Table 8.21. These compositions guarantee a soft consistency with and without coconut oil. Coconut oil has a very fluctuating price and is usually very expensive. Therefore,
Fig. 8.40. Packaging machine for bakery margarine bars (Type BPM 200 of Bock & Sohn Company, Norderstedt; courtesy of Bock).
Fats and Oils Handbook
774
Solids content [%]
50 40
30 20 10
0 0
-
C Value l
400
'
"
!
'
"
I
800
"
'
,
'
1,200
'
'
1,600
2,000
Fig. 8.41. C-value and solids content of margarines.
it is used mainly for premium-brand cream margarines. In cases in which a firmer consistency is desired, the proportion of hardened oil 41 has to be increased at the expense of oil or hardened oil 34. 8.2.9.2 Bakery Margarine. Bakery margarines have a higher melting point (35-38°C) than those products produced for direct consumption. They do not have to melt in the mouth, but are designed to separate the crumbs as long as possible by breaking the continuity of the protein starch structure. This characteristic and their function as nuclei for boiling (steam formation that puffs the baked goods) ensure tender cake. The composition of bakery margarines resembles that of fm cream margarines. 8.2.9.3 Puff Pastry Margarine. Puff pastry margarine has to meet high demands on its tenacity. In puff pastry, it has to ensure that the many layers of the laminate stay separated. In the lamination process (whether hand or machine made), the thin layer of margarine must not break, but has to adapt to the laminate in smooth, very TABLE 8.21 Typical Formulations for Cream Margarines A(%)
Coconut oil Vegetable oil hardened to 34'C hardened to 41°C Vegetable oil
15-25 40-50 10-15 15-25
B(%) 70-80 2C-30
Fat as F o o d
775
thin layers, i.e., it has to have high plasticity. Its C-value is very high (up to 2600), and its melting point of 40-44"C is considerably higher than that of bakery margarine. Yet even today, puff pastry margarine is sometimes produced on cooling drums (see also Table 8.14). The plasticity of margarines is inversely related to the amount of product that postcrystallizes after having left the processing unit and B-unit. Madsen (1981) compares three puff pastry margarines produced under different processing conditions (Table 8.22). The processing units are Perfectors (trademark of Gerstenberg Company) that consist of A and C-units. All margarines of this series of trials contained 16% water, 0.1% of a distilled monoglyceride (Dimodan PM, trademark of Grindstedt Company) and 0.1% soy lecithin as well as the fat blend. The trials were run on a processing unit of experimental size. Although the results cannot in any case be transferred directly to production-sized units, clear trends can be detected. Only the product run via the cooling drum (trial 5 ) and the one run with low throughput, i.e., high residence and also crystallization time (4), had sufficient plasticity and were not greasy. Apart from the formulations based on tallow (that had P-crystals, as would lard), all blends crystallized in P'-modification. The postcrystallization behavior of the different margarines was also very different. Only cooling with a drum allows the emulsion to be supplied to the cooling surface in such a thin film that heat is immediately carried off. By comparison, the thickness of that film in a scraped surface heat exchanger (A-unit) is 7-12 mm, which is the size of the gap between the wall of the cooling tube and the rotating shaft. Here also the product is overworked during cooling; while on the drum-cooling, it is stress free and kneading is done later. This ensures a more plastic end-product. This is why producing puff pastry margarines on SSHE requires special know-how and many companies remain with the cooling-drum process. Before distribution, puff pastry margarine has to ripen for -4 d in an environment of -15°C. It is also possible to produce puff pastry with shortenings. In that case, however, there must be some water present in the shortening (Hoffmann 1989) to enhance the "puff' in order to obtain a good product. TABLE 8.22 Processing Conditions for Puff Pastry Production Trialsa ~
Sequence of units Throughput Residence time Exit temperature with product base Tallow Palm oil Soybean oil aSource: Madsen (1 981 1.
(kgh) (5)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
A-C-A 50 90
A-A-C
A-A
50 40
A-A 20 1 00
Drum
50 90
9 10 12
13 12 18
7 8 10
1
("C) 10
8 10
0 0 0
Fats and Oils Handbook
776
8.2.10 Half-Fat Margarine
Most margarine laws allow for half-fat margarines with fat contents prescribed -40%. The demand for these products, which were first introduced in 1964, has increased considerably over the past 30 years, because they offer a real opportunity for reduced calorie intake while maintaining good taste. In 1981, in the whole of Europe, only 28 such products were marketed (Madsen 1984), whereas eight years later in the United Kingdom alone, there were more than 200. Table 8.23 gives some details concerning the amount of half-fat margarine, half-fat butter (see also Chapter 8.1.7) and melanges (see Chapter 8.2.12) sold in individual countries in 1988 and 1995. In such reduced-fat products, the water phase has to be stabilized with thickeners, because the emulsion and the c,rystal network alone are not able to guarantee temperature stability and good shelf life properties. In addition, dry matter is increased by the addition of milk proteins as milk powder. Half-fat margarines normally contain preservatives, because the water droplet distribution is much coarser than with normal margarine, and therefore they are much more sensitive toward microorganisms that find ideal conditions in which to grow. The production of sterile half-fat margarines is not a problem, however, because machinery for aseptic filling exists. The only drawback is some expenditure for the sterilization of the packaging material. The crucial point is the period of open shelf life, i.e., the period of use at home. Even if produced and delivered in a sterile condition, a nonpreserved low-fat margarine is exposed during use to ambient conditions that can cause quick spoilage. In such cases, the supplier is made responsible for the damage although the contamination with microorganisms occurred in the home by contact, for example, TABLE 8.23 Half-Fat Margarine, Half-Fat Butter, and Melanges Production in Selected European Countriesa ~
Half-fat margarines
Half-fat butter
~~
Melanges
Production (1 000 MT)
1988
1995
1988
1995
1988
1995
Belgium Denmark Germany Finland France
15.0 13.7 22.5 4.9 26.5 49.0 4.3 34.5 0.5 2.5 28.6 2.4
15.1 2.6 90.0 1.5 23.5 69.0 6.6 40.3 1.2 20.0
5.5 10.0 2.5 4.0 2 .o -
1.7 0 11.0 5.0 0.5 1.4 1.7 0 0 -
7.8 -
0.1 24.2 5 .O 11.5 6.1 45.3 13.9 0.3 0 0.4 37.7 3.0
Great Britain Ireland Netherlands Portugal Spain Sweden Switzerland
aSource: 1988 data after Madsen (1 990).
-
-
28.5 4.5
t
777
Fat as Food
TABLE 8.24 Typical Formulations for Half-Fat Margarines
c (Yo)
B (%)
A (%) _______
~
Water phase (water to 100) Whey powder Butter milk powder Na-Caseinate Gelatine Sorbate Salt Oil phase Emulsifier Monoglycerides Monodigl ycerides Fab‘oil blend Vitamins, carotenes, flavors
1 .o-1.5
2.3 1.4 1.3
7.0 1.5-2.5 0.1
0.1
0.2
pm.
p.m.
39.3-39.8
0.2 39.1
0.2 39.3
p.m.
pm.
p m
p.m.
0.2-0.5
aSources:A, B from Madsen (1 990) and C from Nichols (1 989).
with air, dust, “knives with marmalade” and so on. In that sense, open shelf life represents a factor of uncertainty that can be avoided only by preservation. Typical formulations for half-fat margarines are given in Table 8.24. Legislation in this field has been very illogical. Stabilizers allowed in one country were disallowed in a neighboring country and vice versa. Table 8.25 shows the situation in that field for the year 1989. Meanwhile, at least for the European Community, this seems to have TABLE 8.25 Stabilizers Allowed for Half-Fat Margarine in 1989 in Some Selected European Countries (with Some Limitations)
Monoglycerides Esters of Monoglycerides Acetic acidLactic acidCitric acidTartaric acidPropylene glycol Sorbitol G a r gum Locust bean gum Carragheenans Alginates Pectins Gelatin Xanthan gum Methylcellulose (MC) Carboxymethylcellulose (CMC)
D
DK
NL
S
CH
F
X
X
X
X
X
X
X X X X
X X X X X X X
X X X
X X X X
X X
X
X
X X X X X
X X
X
X X X X X X X X X X X X X
X
X X X X X X
X
X
X
X
Fats and Oils Handbook
778
been overcome. Also, protein concentrates can be used as stabilizers (e.g., Hawley 1977 and Wallgren and Nilsson 1979). The protein content of the aqueous phase can then increase to 25%. 8.2.11 Other Emulsion Fats. With liberalized legislation in many countries, all
fat levels are legal in emulsion fats; however, the name margarine can be used only for some distinct fat levels, i.e., usually 80% fat for the full-fat version and 75, 50 and 25% of it. Six to seven years ago, the limit for stable emulsions was -20%, whereas virtually fat-free products can be produced today; there is still room for taste improvement, however, with such products. The technical requirements for producing reduced-fat spreads are given by Darrington (1988), for example. The formulations are based on those for half-fat margarine. In addition to these products, melanges and others, i.e., blends of butterfat and vegetable fats have entered the market after the recent lifting of strict legal limitations. Usually they are produced from butter with the addition of vegetable oil (Madsen 1990). Because they do not offer real advantages over the pure traditional products (butter and margarine), their success in the market in most countries (except Sweden, for example) is very limited. 8.2.12 Energy and Auxiliary Material Consumption. Energy consumption for margarine differs from type to type; 80% fat margarine accounts for approximately the following energy consumption:
Water Steam, low pressure Electrical energy for liquefying ammonia
0.75495 150-200 . 50-80 15-20
(mVton) (kg/ton) (kWton) (kWton)
For the production of shortenings, similar figures can be expected.
8.3 White Fats, Shortenings White fats and shortenings are used in large amounts as ingredients in the food industry; both are heat transfer media for shallow frying in households and feeding centers. If used for baking and in non-Enghsh speaking countries, they are called shortening. That name has usually been used for lard products that were used in baking and that made the structure of the baked good “shorter” by hulling the m b with a fat film, preventing the gluten from sticking together. Such shortenings have a water content of 0.2%maximum without any water being added. They are composed of animal or vegetable fat blends that may be partially hardened, depending on the declaration. 8.3.1 White Fats in Wrappers or Tubs
Shortenings are suspensions of fat crystals (usually of the stable p-modification) in oil or semiliquid fats. Solid fat is only -1% soluble in semiliquid fat or oil, which
Fat as Food
779
means in fact that they can only exist as a suspension and do not dissolve. Depending on the structure, one speaks of pumpable or plastic shortenings (for the production process, see Fig. 8.42). 8.3.1.1 Pumpable (Liquid) Shortenings. Liquid shortenings are produced by cooling melted fat and destroying crystals that are formed by sheering or beating. The desired crystal size is 5-10 pm. Liquid shortenings contain 5-30% solid triglycerides with high melting points. The liquid state makes it more applicable in industrial baking or the food industry because it is pumpable and much more easily dosed than solid fat. If such shortenings are blended with 3-5% monodiglycerides (see Chapter 8.9), many small crystals are built as a result of their crystallization behavior and melting point. These work as crystal seeds, promoting crystallization. Added to bakery fats, the baking-promoting properties of monodiglycerides are then already incorporated into the shortening. Such shortenings should be liquid above 15°C and keep their properties of use up to 35°C. Pumpable shortenings are also used in feeding centers and the food industry for large-scale shallow and deep frying. They are packed in units ranging from buckets up to whole tank cars.
8.7.3.2Plastic Shortenings. Plastic shortenings are produced according to the margarine making process but without emulsification with a water phase. In the plant, therefore, 25% more heat of crystallization has to be deducted. This is partly compensated for by the fact that water with its high specific heat need not be cooled down. Crystallization is more difficult in shortenings because no water droplets are present on their interface to the fat to promote crystallization. If a shortening is whipped with nitrogen (preferred to air, because oxygen free), its use is improved becuse it is softer and much easier to portion. In addition, its color, which may appear gray in most solidified fats that also contain oil, Fat blend
I I
I
Melting
I anahour to margarine (see Flgm8.24)
plastic: wrappers, tubs, boxes semiliquid: buckets, containen
Fat (Shortening)
Fig. 8.42. Flow chart of shortening production,
Fats and Oils Handbook
780
whitens. There are different opinions concerning the point at which to add nitrogen in the plant. Working models for any injection position between the pump feeding the processing unit and the packing machine can be found. Plastic shortenings can also be blended with monodiglycerides, with a common amount of 510%. 8.3.1.3 Fats in Other Forms. In addition to the above described forms, fats are also delivered in flakes, as a granulate and as fat powder (see Chapter 8.3.3). It is then essential that they be stored below their melting point so as not to bake together. 8.3.1.4 Fat in the Form of Slabs. Today, fat in slabs is almost exclusively coconut based. The liquefied fat is cooled down in a SSHE or other agitated vessel to a point at which -5% is crystallized. It is then still pumpable though already highly viscous. It is poured into forms resembling those of the chocolate industry. These forms are further cooled in a cooling tunnel. Then the fat plates are beaten out of the molds and packed. The forms can be made from metal or plastic material. Metal has the advantage of easier heat transfer; the plastic molds are lighter, less noisy and can be cleaned more easily (for the production process, see Fig. 8.43). Such fats are used to produce confectionq covertures. They are also excellent for deep frying, with the disadvantage of possibly heavy foaming. 8.3.2 Fat Specialties
These fats serve special purposes. Their properties have to be adjusted exactly to the technologically founded specifications of the industrial clients. Such fats include, for example, cocoa butter substitutes (see Chapter 6.2.3.5), coatings for ice cream or fats for coffee whiteners (see Chapter 8.6.2). If these fats are not used
molten until 5% a n crystallized Filling into forms I
I
i cooling in cooling tunnel I
Pouring machine -15 to -20% -20 min
Wrapper or sachet
(Coconut-) Fat in slabs
Fig. 8.43. Flow chart of fat production in slabs.
Fat as Food
781
TABLE 8.26 Council Regulation 2991/94 of the European Community Concerning Fats Composed of Plant and/or Animal Origin
Fat group
Product categories Additional description of the category with an indication of the fat content by weight
Definition
Sales description
C. Fats composed of plant and/or animal products Products in the form of a solid malleable emulsion principally of the water-inoil type, derived from solid and/or liquid vegetable and/or animal fats suitable for human consumption, with a milk-fat content between 10 and 80% of the fat content
1. Blend
The product obtained from a mixture of vegetable and/or animal fats with a fat content of not <8O% but <90%.
2. Three-quarterfat blend
The product obtained from a mixture of vegetable and/or animal fats with a fat content of not <6O% but <62%.
3. Half-fat blend
The product obtained from a mixture of vegetable and/or animal fats with a fat content of not <39% but <41%.
4. Blended spread X%
The product obtained from a mixture of vegetable and/or animal fats with the following fat contents: <39% >41% but <6O% >62% but <80%
Note: The milk-fat component of the products listed in the Annex may be modified only by physical processes
immediately after production, they are usually shipped to the clients in bulk. In contrast to fats for the household customers, their intrinsic value does not lie in properties incorporated by processing (melting behavior, consistency and appeal), but in fulfilling the client’s specifications exactly, thus enabling further processing without defects. 8.3.3 Crystal Fat Powder
For many products such as ready baking mixes, ice cream powders and cream powders, fat powder is needed. The key to this product is how it performs during mixing with other ingredients such as sugar or flour. If it is coated with these materials in the mixing process, it stays powdery and looses its tendency to smear at higher temperatures. The crystal fat powders produced have particle sizes of -50 pm. Therefore, mixing with other ingredients as well as coating is easily accomplished. Figure 8.44 shows the production process and Figure 8.45 shows a plant for powdered fat production and also for mixing with powdered ingredients. The liquefied fat is kept in a buffer vessel (F). From there it is sprayed via the injectors (2) that are fed by a pump (M) into the crystallization chamber (1). The air in that chamber is cooled to a temperature range from -15 to -30°C and recirculated (3-5)
Fats and Oils Handbook
782
Fat blend t=mw+lOK
into very cdd air
(-15 to -3O‘C)
Fig. 8.44. Flow chart of crystal fat powder production.
via a special filter (U) that clears it off from ultrafine fat dust. The shock frosted powder is then conveyed via a belt into the mixing drum, where it is mixed with the previous ingredients. Depending on which ingredients are used, the blend can also be run over a ball mill. The temperature in the mill must be kept very low. Plant such as that described produce -1 ton/h fat powder and up to five times that for mixes.
8.4 Salad and Frying Oils Among the edible oils, salad oils and oils for shallow and deep frying are usually differentiated. The primary difference is that the latter have to be more heat stable. According to the local habits in some countries, the Meditenanean countries, for example, many oils are used instead of fats for deep frying, and special products exist in the market. In middle Europe, universal oils that can be used for both purposes with a stress on salad use are more common. If oils with a high linolenic acid content such as soybean oil are used, stability can be improved immensely by slight hardening (see Chapter 6.5) and removal of the fat created by winterization (see Chapter 6.3). This operation reduces the linolenic acid content that, if left unchanged, would decrease stability as a result of its high degree of unsaturation (see, for example, Neumunz 1978). The proportion of linolenic acid depends on the degree of hardening, which is reflected by the iodine value of the oil (Fig. 8.46). For salad oil consumers, it is essential that the oil not be cloudy or turbid (because of crystallized fats or waxes) when coming from the refrigerator. For this reason, these oils are winterized (see Chapter 6.3).They are then quality checked by the so-called “cold test.” The solids content of edible oils is very low. Table 8.27 gives this content for temperatures of 0 and 5°C. From the table, it can be seen that palm oil, despite its low price, cannot be used as a salad oil. However, the
on
8
Fig. 8.45. Plant for crystal fat powder production (courtesy of Krupp Industrietechnik).
Fats and Oils Handbook
784
[%I
Fatty acids content 60
I
1 Linoleic acid
--- -- -- --- ---
----__-- -- --
30
--.-_ -----
Oleic acid Stearic acid
Linolenic acid
__---------------
----------_--__.
c
110
114
118
122
126
130
134
Degree of hardening [Iodine value] Fig. 8.46. Dependency of linolenic acid content of soybean oil on the degree of hardening (after Evans e t a / . 1973).
fractionated olein (see Chapter 6.2) can well be used. Sunflower oil is fractionated because of the wax stemming from the hulls, not because of stearines. The opposite is true for cottonseed oil, which has a relatively high content of high-melting triglycerides compared with other seed oils. The solids content of slightly hardened soybean oil depends on the degree of hardening. Figure 8.47 shows solids analyzed by different authors and the resulting dependency in the form of a straight line. In some countries, the use of crystal inhibitors is legal. In the U.S., for example, 0.125% oxistearine may be added, a limit set by the FDA. Oxistearine is produced by blowing air through hardened cottonseed oil 35, which leads to oxidized products that decrease the oil’s crystallization tendency. Oils and fats during deep and shallow frying are subjected to great heat and the ensuing degradation that is caused on the one hand by the heat and on the other by TABLE 8.27 Solids Content of Oils at Low Temperatures Oil
0°C
5°C
10°C
Soybean oil Cottonseed oil Sunflower oil Peanut oil Rapeseed oil Sesarneseed oil
<0.5 <0.5 0 <6 <1 d.2
0 0
0
0 0 0
<4
<2
0
0
<0.5
0
Oil
0°C
5°C
10°C
Linseed oil Safflower seed oil Corn oil
<1.5 0
<0.5
<1 0 0
0 0 0
Palm oil Olive kernel oil
-
-
50
<0.5
0
0
Fat as Food
Olein yield
785
[%I
100 I 90 -
A = after Okkerse et al 1967
80 -
B = after Moulton et al 1971
70 -
C = after Gooding et al 1953
60 D = after Evans et al 1964
50
E = after Cowan et al 1965 40
F = &er Vahlteich and Mehck, 1953
30
~
85
88
,
,
,
91
94
97
100
103
,
I
106
109
I
Iodine value
Fig. 8.47. Dependency of olein yield on the degree of hardening in winterized hardened soybean oil (data from Evans et a / . 1964, Okkerse et a/. 1967, Moulton et a/. 1971, Cowan 1965, Vahlteich and Melnick 1953 and Gooding 1953). oxidation. This is more important in deep frying, of course, because the oil is used repeatedly over a longer period. Oxidation begins with the formation of hydroperoxide that is completely tasteless. Only the subsequent reaction products, namely, aldehydes and ketones, are responsible for off-taste and off-flavors. However, the amount of aldehydes formed determines whether it is called a flavor or an off-flavor. 2,4-Decadienal, for example, is the "wanted" flavor of roasted food; the same in higher quantities is a disgusting off-flavor. In some countries antioxidants are allowed to protect the oil against oxidation; these include BHA, butylated hydroxyanisole (almost everywhere), PG, propyl-gallate (almost everywhere), BHT, butylated hydroxytoluene (almost everywhere), ascorbyl-palmitate and TBHQ, tertbutylhydroquinone (e.g., US.,Brazil and Peru). These antioxidants are often dosed to the crude oil and mainly disappear during refining. An overview of the most common antioxidants was given by Sherwin (1976). In middle Europe, these substances are usually not allowed in the final product. Antifoaming agents such as silicones (Kusaka 1984 and 1986) are also common in many countries. Usually, they have to be declared on the ingredients list. To improve oxidative stability, it is also possible to remove catalysts that promote oxidation from the oil, e.g., metals. If citric acid is added, metals are bound in a chelate and their catalytic potential is blocked. The stability of oils has been researched intensely; however, in many cases, the conditions chosen for the trials do not adequately reflect reality. To a certain extent, this approach is necessary because only under strictly controlled laboratory conditions can the model trials that allow reproducible changes in the processing
Fats and Oils Handbook
786
300 350 400 450 500 550 600 650 700 750 800
Wave length [nm]
-colorless - - green
' '
- amber
Fig. 8.48. Transmission of packaging material and absorption of sunflower oil.
parameters and the canying out of reliable analysis be conducted. On the other hand, this is the reason that the trial results are somewhat artificial. Packaging is also an important parameter for oils, because oxygen tightness and light protection are beneficial. Figure 8.48 shows the transmission curve of packaging material compared with the absorption curve of sunflower oil. In can clearly be seen that PVC is best because absorption of the oil ends where transmission of PVC starts. To achieve similar effects with other packaging material, they have to be colored, which consumers dislike because they cannot see the product. Plastic bottle manufacturing can be carried out in close proximity to the filling operation. In the case of PVC bottles, these can easily be blown. In the case of other plastic materials, beginning with the delivered preforms that already included the neck of the bottle was common. More and more machines are entering the market that can conduct the activities of preforming and blowing the preform one right after the other. Filling is done with fillers that are well known from the beverages industry and will not be covered here. In addition to glass and plastic bottles, tins are also used. Simple tins as well as reclosable ones are available. In some overseas countries, unpacked oil is still sold from drums.Others use cheap plastic sachets that are decanted at home into pitchers.
8.5 Mayonnaise Mayonnaise is an emulsion of (usually 80%) oil in water. Some countries also allow 70%;mayonnaise with 50% oil is often called salad mayonnaise.
Fat as Food
I
Emubing
-+ Emulsifying
787
I 4-
<<< Oil
I
Packaging
Mayonnaise
Fig. 8.49. Flow chart of mayonnaise production.
8.5.1 Legal Basis
For mayonnaise a draft standard of the Codex Alimentarius Commission exists (1995). It states (excerpt): 2. Description Mayonnaise is a condiment sauce obtained by emulsifying edible oil(s) in an aqueous phase consisting of vinegar, the oil-in-water emulsion being produced by egg yolk. Mayonnaise may contain optional ingredients in accordance with Section 3.2 and Section 8.1.2. 3. Essential Composition and Quality Factors 3.1 Ingredients 3.1.1 All ingredients shall be of sound quality and fit for human consumption. Water shall be of potable quality. 3.1.2 Ingredients shall comply with the requirements of the relevant Codex Standards and in particular the Codex Standards for Vinegar and Edible Vegetable Oils. 3.1.3 Eggs and egg products shall be hens’ eggs or hens’ egg products unless specified in the labelling. 3.2 Composition Requirements 3.2.1 Total fat content: not less than 65%. 3.2.2 Egg yolk (technically pure) in amounts sufficient to emulsify the product. 3.3 Optional Ingredients The following food ingredients intended to influence significantly and in the desired fashion the physical and organoleptic characteristics of the product may be used subject to Section 8.1.2. (a) egg products including white
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(b) sugars (c) food grade salt (d) condiments, spices, herbs (including mustard) (e) lemon juice (0 water (g) skimmed milk powder In the US.,Subpart B: Requirements for Specific Standardized Food Dressings and Flavorings, mayonnaise is defined as follows:
5 169.140 Mayonnaise. (a) Description. Mayonnaise is the emulsified semisolid food prepared from vegetable oil(s), one or both of the acidifying ingredients specified in paragraph (b) of this section, and one or more of the egg yolk-containing ingredients specified in paragraph (c) of this section. One or more of the ingredients specified in paragraph (d) of this section may also be used. The vegetable oil(s) used may contain an optional crystallization inhibitor as specified in paragraph (d)(7) of this section. All the ingredients from which the food is fabricated shall be safe and suitable. Mayonnaise contains not less than 65 percent by weight of vegetable oil. Mayonnaise may be mixed and packed in an atmosphere in which air is replaced in whole or in part by carbon dioxide or nitrogen. (b) Acidifying ingredients. (1) Any vinegar or any vinegar diluted with water to an acidity, calculated as acetic acid, of not less than 2.5% percent by weight, or any such vinegar or diluted vinegar mixed with an optional acidifying ingredient as specified in paragraph (d)(6) of this section. For the purpose of this paragraph, any blend of two or more vinegars is considered to be a vinegar. (2) Lemon juice andor lime juice in any appropriate form, which may be diluted with water to an acidity, calculated as citric acid, of not less than 2% percent by weight. (c) Egg yolk-containing ingredients. Liquid egg yolks, frozen egg yolks, dried egg yolks, liquid whole eggs, frozen whole eggs, dried whole eggs, or any one or more of the foregoing ingredients listed in this paragraph with liquid egg white or frozen egg white. (d) Other optional ingredients. The following optional ingredients may also be used: (1) salt. (2) Nutritive carbohydrate sweeteners. (3) Any spice (except saffron or turmeric) or natural flavoring, provided it does not impart to the mayonnaise a color simulating the color imparted by egg yolk. (4) Monosodium glutamate. (5) Sequestrant(s), including but not limited to calcium disodium EDTA (calcium disodium ethylenediaminetetraacetate)andor disodium EDTA (disodium ethylenediaminetetraacetate),may be used to preserve color and/or flavor.
Fat as Food
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(6) Citric and/or malic acid in an amount not greater than 25 percent of the weight of the acids of the vinegafor diluted vinegar, calculated as acetic acid. (7) Crystallization inhibitors, including but not limited to oxystearin, lecithin, or polyglycerol esters of fatty acids. (e) Nomenclature. The name of the food is “Mayonnaise.” (f) Label declaration. Each of the ingredients used in the food shall be declared on the label as required by the applicable sections of parts 101 and 130 of this chapter. 8.5.2 Composition and Processing
Mayonnaise usually contains the following ingredients: oil, emulsifier (egg yolk prescribed in some countries), vinegar (as pH regulator and as flavor), spices, flavors (sugar, salt, mustard ...) and stabilizers (thickeners for mayonnaise with <70% oil only). Mayonnaise with 80% oil approaches the limit for stable oil in water emulsions, which are unstable above 85% oil. With more oil, the packaging of oil droplets is too dense to allow for an emulsion. The high viscosity of mayonnaise results from the already high droplet density at 80%. Oshida (1978) showed that it would be possible to stabilize even 90% fat mayonnaise with the aid of a colloid mill (droplets of 2-3 pm); however, such high oil content does not improve the product and is therefore uncommon. There is more of a tendency to lower oil contents to ~ 3 0 %(Jinson 1979); such products are appearing more and more in the market. The taste of mayonnaise is very different in certain countries. In Europe, it has a slightly sour blend taste, and in the Mediterranean area, mainly lemon juice or vinegar and oil. It becomes sweeter and has a more mustard taste when going north and is very sweet in Scandinavia. The total manufacturing of mayonnaise is covered in detail by Philipp (1984), for example. To produce mayonnaise, the egg yolk is mixed with the ingredients, the water and one third of the vinegar, and stirred to high viscosity. The temperature during this process, called “cold process” should not rise above 5°C. Then slowly the rest of the vinegar and the oil are added. The “hot process” uses temperatures of -70°C and warm filling. The typical flavor of mustard in many countries is the allyl-thiocyanate of mustard. Vinegar intensely influences microbiological stability; the lower the pH, the more stable the product. This means that production of mild, i.e., less sour, mayonnaises requires higher hygienic standards in manufacturing. Mayonnaises in the market usually have a pH between 3 and 4. In addition to producing mayonnaise in churn-type machines, it is also possible to use continuous plants such as SSHE (Anonymous 1983, Schroeder 1979). The ingredients are then prepared singly, mixed according to margarine manufacturing and fed to an emulsifying tube that is equipped with a colloid rotor for final fine emulsification. Heuss (1983) compares discontinuous, semicontinuous and continuous processing.
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Fats and Oils Handbook
For the manufacture of delicatessen salads of all kinds, salad mayonnaise (50% oil) or mayonnaises with even less oil are used. With their thickeners, they are able to stabilize the water arising from the syneresis of other salad ingredients such as vegetable or fruit. If such salads are made with 80% mayonnaise, this water gathers at the bottom of the container. 8.5.3 Remoulade (Mayonnaise-Based Dressings)
Mayonnaises with herbs and more spices are called remoulade. They follow mayonnaise making. Their oil content usually is 150%.
8.6 Vegetable Creams, Cream Substitutes 8.6.1 Non-Dairy Creams
Products in which milk fat is replaced by vegetable oiYfat are called vegetable cream or non-dairy cream. These creams are used in bakeries, for example, for the production of cake fillings. They are usually more stable than dairy cream when whipped and allow for much higher overrun. Most of these products cannot be mixed with dairy cream because of the incompatibility of their crystal modifications. The compositions for such non-dairy creams are manifold and depend on the purpose for which they are made. This ranges from toppings on soups to sauces to decoration of cakes. They can be simply whippable to replace dairy cream (A in Table 8.28 by Grindstedt) or paired with freeze stability (B). Or they can also ensure low caloric products (C) combined with the vegetable fat base. Non-dairy TABLE 8.28 Compositions of Vegetable Creams for Different Usesa B (Yo)
c (Yo)
28.0
15.0
2.1
0.5-1 .O
3 .O 3.0 3.0 8.0 0.5
0.6
1.o
0.8 0.3
0.1 0.05
0.1
0.1 0.05 0.1
(Yo)
Ingredient
A
Fat (coconut 34 or palm kernel 34) Skim milk powder** Sugar Dextrose Glucose syrup Sodium caseinate Emulsifiers Lactic acid monoglyceride estera Distilled unsaturated monoglycerideb Diacetyltartaric acid monoglyceride, DATEMC Alginate Hydroxypropyl cellulose, HPMC*
29.2 6.25 >0.05
e.g., aLactodan P22, bDimcdan OT, CPancdan 150 (trademarks of Grindstedt). *Also carboxymethyl cellulose CMC, alginates, carragheenans. "Or equivalents of skim milk. 5ource: Crinstedt.
0.1
0.3
0.25-1 .O
791
Fat as Food
Stabilizer
1-
Mbring
e.g. HM-Cotlukmo
65-75% A
A
145'C, 4 8
I I
I <15'C, plete bat exchanger
Coding
I
m m I
-5'C, 24h
WhippaMe vegetable cream
Substitub for (dk-) m m
Fig. 8.50. Flow chart of vegetable cream production.
creams are whippable at much lower fat levels than dairy cream, which is whippable above -25%. The formulations in the table can also serve as examples because the recipes can vary greatly. To produce freeze-stable creams, their sugar content must be >12% and the amount of fat must also be higher than that in ''ordmiy" non-dauy creams. The same holds for creams with long-time stability in the whipped state. Water-binding properties can be improved by increasing dry matter with sugars (sugar, dextrose, glucose syrup). In addition, these ingredients provide a full-bodied mouth feel. The liquid creams can be filled in bulk or in packages such as Tetra brick and are sold to industrial and artisanal customers. Their advantage, in addition to higher stability and higher overrun, is a price much lower than dairy cream. Small household packs of usually 250 g are also available. Whippable creams in powder form contain >50% fat, -33% sugar to increase dry matter and to bind water (maltodextrine, for example), equal amounts of -643% milk solids (such as caseinate) and emulsifiers. Qi Si (1986) researched the whipping performance of different fats, keeping emulsifiers, sugars and milk solids constant. He obtained the highest overrun with
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TABLE 8.29 Typical Composition of Coffee Whiteners Vegetable fat Glucose syrup Sodium caseinate Disodium phosphate Emulsifiers
3545% 5@-60% 66% 1-2 Yo 0.2-05%
coconut oil and butter fat; the latter needed two and a half times the whipping time of the former. The stiffness of the foam was best with palm oil, which was similar to coconut oil in its whipping performance. Coconut oil, as well as hardened soybean oil and hardened palm oil, showed no syneresis at all 3 h after whipping, whereas this was very strong with butter. Further details on the role of ingredients of such creams are given by Knightly (1968), for example. The phenomenon of whipping behavior correlated to the cream’s microstructure is explained by Buchheim et al. (1985), and Thalheimer (1968) explains the emulsion. 8.6.2 Coffee Whiteners
Coffee whiteners, cream substitutes (mainly powdery) that are used exclusively in coffee, contain considerable amounts of fat. A typical formulation for a powder is given in Table 8.29. It is important to select the fats and the other ingredients in such a way that they quickly dissolve completely in the coffee without flocculating at certain temperatures. In liquid whiteners, fat and glucose syrup content is -10% each. The other ingredients are lowered pro rara from the above figures. Details concerning the functionality of the individual ingredients can be found in Knightly (1967). 8.6.3. Sweet Spreads
A number of sweet spreads exist that are consumed mainly by children. The best known are the chocolate creams of the Nutella-type. These spreads also contain high proportions of fat, which is required mainly to ensure a smooth mouth-feel. The fats are thoroughly mixed with the other ingredients and may also be conched. Their melting point must lie below body temperature to avoid negative sensory sensation, i.e., greasy mouth-feel.
8.7 Peanut Butter Peanut butter is an important product, mainly in the U.S. (-1.4 kg per year per person) and also in countries such as Canada (0.2 kg) and the Netherlands (0.14 kg; Young and Heinis 1989). It is used mainly for spreading and contains -50% fat. U.S. law prescribes that it be made at least 90% from peanuts. Figure 8.51 depicts the manufacturing process and the ingredients used.
793
f a t as food
Peanut kernels Roastlng into two h a h w remaining gems may resuk in bitter off-taste
hulls and germs
Removal of poor quality kernels
Sorting out I
<<< Sugar (-2%), salt (-1%)
t t
<<< Peanut oil, partialiy hardenud
t
ccc ErnuQtfmrs (rnonoaiycerides 1.5-2.5%)
(+ 0.5-0.75% for soft products)
Addition of pieces for 'wnchy' products Cooling
Scraped 8udace heat exchangen
7, mainly into glass jars
Packaging
Fig. 8.51. Flow chart of peanut butter production.
8.8 Margarine and Oils with Medium-Chain Triglycerides People with reduced or without proper fat resorption functionality (lacking lipases), for example, those with chronic pancreatitis, are dependent on fats with medium-chain triglycerides (MCT). These fats can pass the intestinal barrier without being split into fatty acids and 2-monoglycerides by lipases or they can be resorbed directly by the portal vein. Although MCT alone are not ideal because they are lacking essential fatty acids, they sometimes are the only way to resorb fat that also plays its role as carrier for lipoids such as vitamins A, D, and E. Bracco (1974, Table 8.30) gives data for products produced according to the scheme shown in Figure 8.52. Medium-chain triglyceride margarines are produced TABLE 8.30 Data of Fats with Medium-Chain Triglycerides (MCT) FA composition Capronic acid Caprylic acid Capric acid Lauric acid
(%)
C6:o C8:o C,:, c12:o
2 -3 52-65 41-47 1-3
Physical data
at 20°C
Specific weight Refraction index Viscosity
(g/crn3) (CP)
0.91-0.93 1.4498-1.4499 -30
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MCT
Fig. 8.52. Flow chart of mediurnchain triglyceride production.
( Wium-Gtmin ~ r i g t y c a r ~ ~ )
and delivered to patients that have the problems mentioned above. Usually these products are not distributed in stores but ordered individually. Their price does not nearly cover the production cost, but they are subsidized by large margarine manufacturers as a courtesy based on social responsibility to the sick, because only these manufacturers are able to produce such products with acceptable consistency and good taste.
8.9. Monoglycerides and Monodiglycerides Monoglycerides and monodiglycerides are not food in the strict sense. However, they are contained in many foods as emulsifiers and, in many respects, they can be viewed as equal to triglycerides. Therefore, their production and properties are briefly documented here. There are two ways to synthesize monoglycerides and monodiglycerides, i.e., esterification of glycerol with fatty acids and reaction of triglycerides with glycerol. The most common production method is the reaction of fats and oils with glycerol. The glycerides synthesized are assigned to the E-number E 471 and have the composition shown in Table 8.31.
TABLE 8.31 Limits of Monoglyceride and Monodiglyceride Compositiona in Share (YO) Component Monoglycerides Dig1ycerides Triglycerides Glycerol Free fatty aciddalkali stearates %Source: Schuster and Adam (1979).
Monodiglycerides
Monoglycerides
3560 35 6 0
90-96 1-5
1-20 1-10 1-10
<1
Fat as Food
795
TABLE 8.32 Characteristics of Some Traded Monoglycerides and Monodiglycerides Made from Different Source Materials
1
From sunflower oil
From hardened tallow
Composition (%) Type+
Monoglycerides Diglycerides Triglycerides Glycerol Free fatty acids Acid number Iodine value Melting point
,
60
90
60
90
5 7-62 33-38 1-8
9@96 3-8 1-6
57-62 33-38 1-8
90-96 3-8 1-6
67-72
28-33
4.5 <1.2 <2.5 <2.0 6C-65
<2 .o 4.2 <2.5
100-1 2 0 2 9-3 5
Depending on their source material, they have different compositions, with the fatty acids always reflecting the fat that has been used for production. Table 8.32 gives the figures for traded products with 60 and 90% monoglyceride content made from beef tallow and from sunflower oil. Emulsifiers are categorized by their HLB-value (Griffin 1979) that indicates whether they are suitable to stabilize water in oil emulsions such as margarine (low HLB) or oil in water emulsions such as ice cream (high HLB; Table 8.33). In addition to their emulslfying ability, partial glycerides form complexes with starch and interact with proteins. Towards acids, bases and lipolytic enzymes, monoglycerides and monodiglycerides behave like fats. Their melting points lie -10°C above those of their source triglycerides (see also Table 2.12). They are insoluble in cold oil, soluble in oil above 60°C or at least miscible. Their crystal modifications are equivalent to those of the triglycerides. Dietetically, they can be seen as equal to fats. Because they are part of the normal digestion cycle, they can be digested completely and there is no restriction on daily intake. As emulsifiers, modified monoglycerides and monodiglycerides can also be used. The number E 472 stands for their esters with citric acid, acetic acid, lactic acid and TABLE 8.33 Hydrophilic Lipophilic Balance (HLB) Values of Different Emulsifiersa Emulsifier
HLB
Oleic acid Glycerol monooleate GIycerol-monolaureate Soy lecithin Ammonium lauryl sulfate' Na-alkyl sulfate
1 .o 3.4 5.2 8 31 40
aSource: Griffin (1979); 'see also Chapter 6.2.
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TABLE 8.34 Data of Three Types of Citric Acid Esters (Type Acidan, Trademark of Grindstedt Company) Citric acid monoglyceride esters ~
Type Saponification value Acid number Iodine value Melting point ("C)
BC
LC
MC
225-255 2 0-3 5
220-250 2540 -30 53
185-215 10-25 -30 55
Oils
<2 60
Fats e.g. tallow
e.g. palm oil L
230'C
+
60.1 20 hPa
Mono- and monodiglycerides
Fig. 8.53. Flow chart of mono- and monodiglyceride production.
diacetyltartaric acid. Except for the latter (maximum daily intake, 50 mgkg body weight), there is no limit for their intake. These emulsifiers are excellent for all prcducts that are to be whipped. In addition they influence crystal modification. They stabilize the a-modification and build protecting membranes, hulling the fat crystals and thus improving the baking behavior. In margarines, spattering during shallow frying is decreased, especially with esters of citric acid. In these esters, one of the above acids is esterified to the 3-position of the 1-monoglyceride. Monoglycerides are also used as ingredients in baking mixtures. An addition of 1-2% leads to significantly reduced retrogradation of amylopectine via an increase in the amount of amylose/fat complexes. Bread is less likely to grow stale and harden (Rack and Krog 1988). 8.1 0 References
8.10.1 References Generally Covering the Chapter Alais, C., (1981) Science du k i t , Principes des Techniques Lairieres, SEP, Paris. Andersen, A.J.C., (1960)Margarine, Pergamon Press, London. Bohm, W.H., (1960)Margarine, in Ullmanns Enzyyklopudie der Technischen Chemie, vol. 12, pp. 235-257, Verlag Urban und Schwarzenberg, Miinchen.
Fat as Food
797
Brill, E.D., (1970) Margarine Today, Proceedings of a Seminar Held at Dijon, IFMA, Leiden. Chrysam, M.M., (1985) Table Spreads and Shortenings, in Bailey’s Industrial Oil and Fat Products, vol. 3, pp. 41-1 11, John Wiley and Sons, New York. Delforge, A, (1982) Tout Savoir sur la Margarine, UNION Anvers. Duvel, D., Pflanzliche Rohstofle der Margarine, Informationsschrift des Margarine Institut fur gesunde Ernahrung, Hamburg. Gander, K.F., (1976) Margarine, Oils, Shortenings, and Vanaspati, J. Am. Oil Chem. SOC. 53,417-420. Graf, E., (1960) Milch und Milchprodukte, in Ullmanns Enzyklopadie der Technischen Chemie, vol. 12, pp. 475-524, Verlag Urban und Schwarzenberg, Miinchen. Hoffmann, G., (1989) The Chemistry and Technology of Edible Oils and Fats and Their High Fat Products, pp. 279-324, Academic Press, London. Kiermeier, F., and Lecher, E., (1973) Milch und Milcheneugnisse, Paul Parey Verlag, Berlin. Kroll, S., (1978) Margarine und Backfette, in Ullmanns Enzyklopiidie der Technischen Chemie, vol. 16, pp. 481498, Verlag Chemie, Weinheim. McDowell, F.H., (1953) The Buttennaker’s Manual, New Zealand Academic Press, Wellington. Mohr, W., and Koenen, K.,( 1958) Die Butter, Milchwirtschaftlicher Verlag-Th. Mann KG, Hildesheim. Rudischer, S., (1959) Fachbuch der Margarineindustrie, Fachbuchverlag, Leipzig. Stuyvenberg, v. J.H., (1969) Margarine, an Economical, Social and Scientific History, Liverpool University Press, Liverpool. Topel, A., (1976) Chemie und Physik der Milch, VEB Fachbuchverlag, Leipzig. Veisseyre, R., (1975) Technologie du Lait, Verlag La Maison Rustique, Paris. Walstra, P., and Jeuness, R., (1984) Dairy Chemistry and Physics, John Wiley and Sons, New York. Wong, N.P., (ed.), (1988) Fundamentals of Daily Chemistry, Van Nostrand Reinhold Co., New York.
8.70.2 Special Literature Anonymous, (1983) Kontinuierliche Herstellung von Mayonnaise, Mayonnaiseprodukten und Ketchup mit dem Kombinator-Verfahren, Lebensmitteltechnik 15, 238-243, Anonymous, Preservatives, Antioxidants, Food Technol. September, 1986. Azukas, J.J., (1962) Sorbic Acid Inhibition of Enolase from Yeast and Lactic Acid Bacteria, Ph.D. Thesis, Michigan State University, East Lansing. Bailey, A.E., Industrial Oil and Fat Products, 272-291, Interscience Publishers, Inc., New York, 1951. Becker, E., and Roeder, I., (1957) Sorbinsaure als Konservierungsmittel fur Margarine, Fette, Seifen, Anstrichmittel 59, 32 1-328. Benhil, Benz and Hilgers GmbH, Diisseldorf/Germany; Multipack 8362, Vollauromatische Hochleistungsmaschine f u r das Abfiillen und Verpacken von pastosen Produkten, Technical Information. Berger, K., Palm Oil Products: Why and How to Use Them, Food Technol., 72-79, September 1986. Berger, K.G., and Teah, Y.K., Palm Oil, the Margarine Potential, Food Manufact. Int. 20, NovemberlDecember 1988.
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Fats and Oils Handbook
Bock, Chr. Bock & Sohn, Hamburg/Germany, Technical Information. Bock, Chr. Bock & S o h , HamburglGennany, Vollautomatische Verpackungsmaschine DKS 500. Bock, Chr. Bock & Sohn, HamburgIGermany, Vollautomatische Abfiill- und VerpackungsmaschineBPM 200. Bosund, I., (1960) The Bacteriostatic Action of Benzoic and Salicylic Acids, Scand. Acta Chem. 14, 1 1 1-125. Bosund, I. (1962) The Action of Benzoic and Salicylic Acids in the Metabolism of MicroOrganisms, Adv. Food Res. 11,331-353. Bracco, U., (1974) Medium-Chain Triglycendes: Charcteristics and Uses, Forschungs- und Entwicklungsabteilung der Nestle AG, Lausanne. Buchheim, W., (1970)Verteilung hochschmelzender Triglyceride in Fettkiigelchen der Milch, Natunvissenschafien 57. Buchheim, W., Barford, N.M., and Krog, N., (1985) Relation Between Microstructure, Destabilization Phenomena and Rheological Properties of Whippable Emulsions, Food Microstructure 4, 221-23 1 . Buchheim, W., and Precht, D., (1979) Electron Microscopic Studies on the Crystallization Process in Fat Globules During the Ripening of Cream, Milchwissenschaft 34, 657-662. Cabarat, I., and Veisseyre, R., (1983) Revue LaitiPre Francaise 416, 55-60. Chrysam, M.M., (1985) Table Spreads and Shortenings, in Bailey’s Industrial Oil and Fat Products, vol. 3, pp. 41-1 1 1 , John Wiley and Sons, New York. Codex Alimentarius Commission, F A 0 Code of Principles Concerning Milk and Milk Products. Cowan, J.G., (1965) HWSB, Hydrogenated-Winterized Soybean Oil, a New Soybean Oil for Export, Soybean Digest 25, 16-17. Danmark, H., and Bagger, L.H.,( 1989) Effects of Temperature Treatment of Sweet Cream on Physical Properties of Butter. II. Factors Affecting Initial Moisture and Fat Loss, Milchwissenschajl 44, 28 1. Darrington, H., (1988) Double Delight from Van den Berghs, Food Manufacture 63, 29-31. Eklund, T., (1980) Inhibition of Growth and Uptake Processes in Bacteria by Some Chemical Food Preservatives, J. Appl. Bacteriol. 48,423432. Eklund, T., (1985) the Effect of Sorbic Acid and Esters of p-Hydroxybenzoic Acid on the Proton-Motive Force in Echenchia coli Membrane Vesicles, J. Gen. Microbiol. 131, 73-76. Evans, C.D., Beal, R.E., McDonnell, D.G., Black, L.T., and Cowan, J.L., (1964) Partial Hydrogenation and Winterization of Soybean Oil, J. Am. Oil Chem. SOC. 41, 260-263. Evans, C.D., List, G.R., Moser, H.A., and Cowan, J.C., (1973) Long Term Storage of Soybean and Cottonseed Salad Oils, J. Am. OiI Chem. SOC. 50,218-222. Flack, E., and Krog, N., (1988) Influence of Monoglycerides on Staling in Wheat Bread, Food Technol. Int. Eur. 199. Frede, E., Precht, D., Pabst, K., and Philipzcyk, D., (1992) h e r den Einflub der Menge und technischen Behandlung von Rapssaat im Futter der Kuh auf die Hitrteeigenschaften des Milchfetts, Milchwissenschafi 47. Gerstenberg, 0. (1988), Increasing Requirements Concerning Production of Low-FatButter, Danish Dairy di Food Industry Worldwide 6,49. Gerstenberg & Agger Frederiksberg/Danmark, Flexibility, Technical information.
Fat as Food
799
Gooding, U.S. Patent 2,627,467 (1953). Griffin, W.C., (1979) Encyclopedia of Chemical Technology, vol. 8, p. 910, John Wiley & Sons, New York. Grindsted, Emulgatorfabrik, DK8220 Braband Danmark, Technical Memorandum - Emulgatoren und Stabilisatoren f i r Nahrungsmittel - Ingredients for the Margarine Industry - Emulsifiers and Stabilizers for the Food Industry - TM lOl-le, the Consistency of Table Margarine - TM 102-le, Cake and Cream Margarine - TM 103-le, Puff Pastry Margarine - TM 104-le, Production of Low Calorie Spread - TM 105-le, Margarine Frying Properties - TM 106-le, How to Save Fat by Using Emulsifiers in Various Foods - TM 107-le, Basic Principles for Producing a Margarine with Good Keeping Properties - TM 109-le, Margarine Factory Equipment, Requirements, and Recommendations - TM 110-2e, the Melting of Emulsifiers for Blending with Oils and Fats - TM 111-le, DIMODAN, Distilled Monoglycerides for the Margarine Industry - TM 114-le, Shortening - TM 116-le, Recombined Butter - TM 3 12-4e, Imitation Whipping Cream - TM 3 14-3e, Low Calorie Imitation Cream - TM 3 15-2e, Frozen Imitation Whipping Cream - TP lOl-le, Puff Pastry Margarine, a Comparison of the Chilling Drum and Tube Chiller Methods of Production - TP 102-le, Postcrystallization in Puff Pastry Margarine - TP 103-le, Low Calorie Spreads in Europe - TP 104-le, The Use of Vegetable Fats in Dairy Products TP 105-le, Emulsifiers Used in Margarine, Low Calorie Spread, Shortening, Bakery Compound and Filling - TP 107-le, Low Calorie Spread and Melange Production in Europe Haighton A.J., (1963) Die Konsistenz von Margarine und Fetten, Fette, Seifen, Anstrichm. 65,479482. Haighton A.J., (1976) Blending, Chilling and Tempering of Margarines and Shortenings, J. Am. Oil Chem. SOC. 53,397-399. Hamba, Hamba Maschinenfabrik, Neunkirchen/Germany , Technical Information - Funktionsbeschreibung Margarinedoseur - BK-Maschinen - Becherfiiller-Margarine - Rundlaufer - Aseptik-Verpackungslinien nach dem Baukasten-Prinzip Hanssen, E., and Wendt, W., (1965) Geschichte der Lebensmittel in Handbuch der Lebensmittelchemie, Springer Verlag, Berlin. Hawley, R.L., (1977) Soya Protein in Low Fat Margarine, Food Prod. Dev.11,43. Heertje, I., Leunis, M., Zeyl, v.W.J.M., and Berends, E., (1987) Product Morphology of Fatty Products, Food Microstructure 6, 1-8. Heertje, I., von Eendenburg, J., Cornelissen, J.M., and Juriaanse, A.C., (1988) the Effect of Processing on Some Microstructural Characteristics of Fat Spreads, Food Microstructure 7, 189-193.
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Fats and Oils Handbook
Herrmann, M., Bylund, G., Damerow, G., and Plett, E.A., Handbuch der Milch- und Molkereitechnik, Verlag Th. Mann, Gelsenkirchen. Heuss, A., (1983) Moderne Herstellverfahren fur Mayonaisen und emulgierte Saucen, Lebensmitteltechnik 15, 148-150. Jinson, N.B., British Patent 1,538,392 (1979). Juriaanse, A.C., and Heertje, I., (1988) Microstructure of Shortenings, Margarine and Butter-A Review, Food Microstructure 7, 181-188. Kayden, H.J., Senior, J.R., and Mattson, F.H., (1967) Monoglycerides Pastway of Fat Absorption in Man, J. Clin. Invest. 46, 1695. Klimes, J., (1990) Shortening-Europe Formulation and Processes, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 207-213, American Oil Chemists’ Society, Champaign, IL. Knightly, W.H., (1968) The Role of Ingredients in the Formulation of Whipped Toppings, Food Technol. 22,731-744. Knightly, W.H., (1969) The Role of Ingredients in the Formulation of Coffee Whiteners, Food Technol. 23, 171-182. Krog, N., (1977) J. Am. Oil Chem. SOC. 54, 124-131. Krupp Industrietechnik, Hamburg/Germany, Anlage zur Herstellung von Kristall-Fettpulver, Technical Information. Kusaka, H., Katsumasa, H., Tsurumizu, A,, and Otha, S . , (1984) On the Function of Silicone Oil in Frying Oil, 111. Protective Effects of Various Silicone Oils on the Thermal Deterioration of Unsaturated Oils and Preventive Effects of Silicone Oil (DMPS) on the Thermal Deterioration of Various Oils, Yukagaku 33, 349-355. Kusaka, H., Katsumasa, H., Tsurumizu, A., and Otha, S . , (1984) IV. Effects of Silicone Oil on the Thermal Deterioration of Frying Oil, Yukagaku 33, 843-849. Kusaka, H., Katsumasa, H., Tsurumizu, A., and Otha, S . , (1986) VI. Effects of Silicone Oil on Water and Dissolved Gas Content in Frying Oil, Yukagaku 3 5 , 4 6 7 4 7 1. Kusaka, H., Katsumasa, H., Tsurumizu, A., and Otha, S . , (1986)VII. Influence of Silicone Oil on the Dissolution of Iron into Heated Fats and Oils, Yukagaku 35, 1005-1009. Kusaka, H., Katsumasa, H., Tsurumizu, A., and Otha, S . , (1986) VIII. Investigation of the Surface Conditions on the Frying Oil Containing Silicon Oil by Infrared AFR Spectrometry and Photometric Spectrometer, Yukagaku 3 5 , 4 6 7 4 71. Luck, (1984) Chemische Lebensmittel Konservierung, Springer Verlag, Berlin. Lynch, M., and Griffin, W., (1974) Food Emulsions, in Emulsions and Emulsions Technology, vol. I, Marcel Dekker, Inc., New York. Madsen, J., Speech delivered at 11th Scandinavian Symposium on Fats, Bergen, June 1981, Published in a brochure of Grinstedt, BrabandDanmark. Madsen, J., (1984) Low Calorie Spread and Melange Production Europe, Technical Memorandum TP 107- l e der Fa. Grindstedt, Braband, Denmark. Madsen, J., Emulsifiers Used in Margarine, Low Calorie Spread, Shortening, Bakery Compoundand Filling, Technical Paper TP 105-le der Fa. Grindsted, Braband, Denmark. Madsen, J., Low Calorie Spreads in Europe, Technical Paper TP 103-le der Fa. Grindsted, Braband, Denmark. Madsen, J., Postcrystallization in Puff Pastry Margarine, Technical Paper TP 102-le, der Fa. Grindsted, Braband, Denmark. Madsen, J., A Comparison of the Chilling Drum and Tube Chiller Methods of Production, Technical Paper TP 101-le der Fa. Grinstedt, Braband, Denmark.
f a t as
Food
801
Madsen, J., (1984) in Foods for the Future, The Proceedings of the International Conference on Oils, Fats and Waxes, Auckland, New Zealand, 1983, (Brooker, S.G., ed.), p. 68, Duromark Publishing, Auckland. Madsen, J., (1990) Low-Calorie Spread and Melange Production in Europe, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modern Practices, (Erickson, D.R., ed.), pp. 221-227, American Oil Chemists’ Society, Champaign, IL. Madsen, J., and Als, G., (1971) Konsistenz und kristalltechnische Verhaltnisse bei der Herstellung von Ziehmargarine auf Druckkuhlern und Kuhltrommeln, Fette, Seven, Anstrichm. 73,405-410. Marsoadiprawito, W., and Whitaker, J.R., (1963) Potassium Sorbate Inhibition of Yeast Alcohol, Biochim. Biophys. Acta 77, 536-544. Moulton, K.J., Beal, R.E., and Griffin, E.L., (1971) Hydrogenation of Soybean Oil with Commercial Copper Chromite and Nickel Catalysts: Winterization of Low Linolenic Oils, J. Am. Oil Chem. SOC.48,499-503. Moustafa, A,, (1990) Margarines and Spreads in the United States, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson D.R., ed.), pp. 214-220, American Oil Chemists’ Society, Champaign, IL. Mulder, H., and Walstra, P., (1974)The Milk Fat Globule; Emulsion Science as Applied to Milk Products and Comparable Food, Pudoc Wageningen, 246-287. Neumunz, G.M., (1978) Old and New Winterizing, J. Am. Oil Chem. SOC.55, 396A-399A. Ney, K.H., (1988) Konservierungsmittel, Gordian 162, 142. Nichols, B.W., (1989) Manufacture of Margarines and Spreads, Food Technol. Eur., 154. Nieuwenhuyzen, W. van, (1976) Lecithin Production and Properties, J. Am. Oil Chem. SOC. 53,425-427. Okkerse, C., de Jong, A., Coenen, J.W.E., and Rozendaal, A., (1967) Selective Hydrogenation of Soybean Oil in the Presence of Copper Catalysts, J. Am. Oil Chem. SOC.44, 152-156. Oshida, K., (1978) Basic Studies on Mayonnaise Production IV: Influence of Emulsifying Method on Voscosity and Stability of Mayonnaise and Diameter of Dispersed Globules, J. Jpn. SOC.Food Sci. Technol. 25, 66-72. Pardun, H., ( 1979) Die Bedeutung der Pflanzenlecithine fur die Lebensmittelindustrie, Zeitschr. Lebensmittelunters. 30, 249. Pardun, H., (1989) Pflarzenlecithine- wertvolle Hilfs- und Witkstoffe? Fat Sci. Technol. 91, 45. Paulitzka, F., (1990) Shortening Products, in World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, (Erickson, D.R., ed.), pp. 203-206, American Oil Chemists’ Society, Champaign, IL. Pedersen, A., (1988) Puff pastry butter-a new product in the dairy industry, Danish Daily & Food Industry Worldwide 6, 53. Philipp, G.D., (1984) Die Praxis der Herstellung von Mayonnaisen und emulgierten Saucen, Lebensmitteltechnik 16, 397-398. Qi Si, J., The Production of Dairy Analogeous Products by Using Emulsifiers, Stabilizers and Flavours, Speech delivered at the Society of Dairy Technology, London, October 1986, Technical Paper TP 303-le, Fa. Grindsted. Rahn, O., and Sharp, P.T., (1928) Physik der Milchwirtschuft, Paul Parey Verlag, Berlin. Rehm, H.-J., and Wallhofer, P., (1964) Zur Kenntnis der antimikrobiellen Wirkung der Sorbinsaure, Naturwissenschuften 57, 13-14.
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Fats and Oils Handbook
Rehm, H.-J., and Wallhofer, P., (1967) Zur Kenntnis der antimikrobiellen Wirkung der Sorbinsaure; 6. Mitteilung; Die Wirkung der Sorbinsaure auf den Kohlenhydratstoff wechsel von Escherichis coli, Zentralbl. Bakteriol. Parasitenkd. Infektionskr. 121, 492-502. Renner, E., and Renz-Schauer, A., (1986) Nahnventabellen f i r Milch- und Milchprodukte, Verlag B. Renner, Gieben. Schleenvoigt, K., (1989)Analysis of German margarines, Personal Communication. Schmitz, R., and Pappe, O., (1977) Die Auswirkungen der Margarinegesetzgebung des Deutschen Reiches von 1887 und 1897 in Bayern, Pharmazeutische Zeitung 122,947. Schroeder & Co., (1979) British Patent 1,548,490. Schuster, G., and Adams, W., (1979) Emulgatoren als Zusatzstoffe fur Lebensmittel, Zeitschrifjir Lebensmittelrecht 30, 256. Senior, J.R. (ed.), (1967) Medium Chain Triglycerides, Division of Graduate Medicine, University of Pennsylvania, Philadelphia. Sherwin, E.R. (1976), Antioxidants for Vegetable Oils, J. Am. Oil Chem. SOC. 53,430436, Skakaly, S.,and Sch&ffer, B., (1988) Structure of Butter. I. A Method for the Determination of LiquidSolid Ratio in Water-in-Oil Emulsions, Milchwissenschufi 43, 557. Skakaly, S.,and Schaffer, B., (1988) Structure of Butter. 11. Influence of Technological Modification of the LiquidSolid Fat Ratio on Butter Consistency, Milchwissenschaft 43, 561. Slover, H.T., Thompson, R.H., Davis, C.S., and Merola, G.V., (1985) Lipids in Margarine and Margarine like Foods, J. Am. Oil Chem. SOC. 62,775-786. Souci, S.W., (1960) Chemische Lebensmittelkonservierung,in U l l m n n s Enzyklopiidie der Technischen Chemie, vol. 11, pp. 440-462, Verlag Urban und Schwarzenberg, Munchen. Soxhlet, F., (1895) iiber Margarine, Munich. Thalheimer, W.G., (1968) Whipped Topping, a Complex Emulsion, Food Eng., 112-1 13. Timmen, H.,( 1960) Der Diacetylgehalt der Butter, Kieler Milchwirtschafrs Forschungsber. 12, 279. Trudso, J.E., (1988) Hydrocolloids: Selection and Application, Food Technol. Eur., 188. Vahlteich, H.W., and Melnick, D., U S . Patent 2,627,468 (1953). Volhard, J., (1896) Ueber Margarine, Zeitschrift Natunvissenschafren, vol. 69, p. 12. Wallgren, K., and Nilsson, T., British Patent 2,011,942 (1979). Williams, N., (1967) Linear and Non-Linear Programming in Industry, Sir Isaac Pitman & Sons, London. Young, C.T., and Heinis, J.J., (1989) Manufactured Peanut Products and Confections, in Food Uses of Whole Oil and Protein See&, American Oil Chemists' Society, Champaign, IL. York, G.K., and Vaughn, R.H., (1964) Mechanisms in the Inhibition of Micro-Organisms by Dehydrogenase Sorbic Acid, J. Bacteriol. 88,411417.
Chapter 9
Analytical Methods Analytical methods for fats and oils are manifold and important also to understand their technology. To describe them in detail goes far beyond the scope of this book. Because references were made to certain methods in the text, an overview of key methods is included in this chapter. For a more detailed view, see the mcial Methorkr and Recommended Pracrices of the American Oil Chemists’ Society, and other books on the analysis of fats and oils published by AOCS Press. See also the European equivalent of the AOCS methods published by the German Society for Fat Research 0. Both the AOCS and DGF method numbers are referenced.
9.1 Acid Value The acid value determines the amount of free fatty acids in a fat. Usually the sample which is dissolved in a solvent (AOCS method: isopropyl alcoholltoluene; DGF method ethanoYether)is titrated with 0.1 N potassium hydroxide solution against phenolphthalein. In practice, for instance in refinery day-to-day operation, KOH may be replaced by the cheaper NaOH. Acid value =
(S- B ) . N .56.1 W
P.11
where S is the standard alkali used for titration of the sample (mL), B is the standard alkali used for titration of the blank (mL), N is the normality of the standard alkali and W is the weight of sample (g). Methods: AOCS: Cd 3a-63; DGF: C-V-2
9.2 Saponification Value The saponification value is the amount of alkali (in this case mg of potassium hydroxide) required to saponify a definite quantity of fat or oil. As all fatty acids “bind” one molecule of potassium hydroxide, the saponification value also indirectly is a measure for the average molecular weight of the triglycerides of a fat and therefore a characteristic number. The fat is saponified with an excess of alcoholic potassium hydroxide. Titration with HCl indirectly delivers the amount of KOH consumed. Saponification value =
( B - S) . N .56.1 W
~9.21
where S is the 0.5 N HC1 solution required for titration of the sample (mL), B is the 803
Fats and Oils Handbook
804
0.5 N HCl solution required for titration of the blank (mL), N is the normality of HC1 solution, and W is the weight of sample (g). Methods:
AOCS: Cd 3-25, Cd 3b-76; DGF: C-V-3
9.3 Iodine Value (IV) The iodine value is a measure for the average number of double bonds of a fat or oil. Double bonds add halogen, with each double bond consuming 1 mol of halogen. The average number of double bonds can then be concluded from the halogen consumption (here: iodine). The addition of iodine is not quantitatively; thus the results of the analysis depend on the method chosen to allow a comparison of different samples. The traditional method uses chloroformium or carbon tetrachloride (both toxic) as a solvent. The fat sample is dissolved in the solvent; then a fixed amount of iodine solution is added. After a reaction time of around -30 min, the excess iodine is titrated with sodium thiosulfate solution and thus the amount of iodine consumed is indirectly measured. Iodine value =
( S - B ) .N. 12.69
P.31 W where S is the thiosulfate solution for back-titration of sample (mL), B is the thiosulfate solution for back titration of blank (mL), N is the normality of thiosulfate solution, and W is the weight of sample (g). The Wijs-method uses an 0.2 N acetic acidcarbon tetrachloride solution as a solvent. A reaction time of 1 h (high IV) to 2 h (low IV) is then needed. More recently the above method has been replaced by others in order to avoid the usage of toxic solvents.
Methods: AOCS: Cd 1-25, Cd lb-87 and Cd ld-92; DGF: C-V-1 l a and b
9.4 Peroxide Value (POV) The peroxide value of a fat reflects the degree of its oxidation taking place. There usually are legal or quality limits for the POV. All substances that oxidize potassium iodide under the reaction conditions are determined by this method. POV =
(S - B).N.1000 W
P.41
where S is the titration of sample (mL), B is the titration of blank (d) N is, the normality cf thiosulfate solution, and W is the weight of sample (g). Methods: AOCS: Cd 8-53 and Cd 8b-90; DGF: C-VI-6
Analytical Methods
805
9.5 Unsaponifiable Matter Unsaponifiable matter consists of those substances that are found dissolved in fats and oils and cannot be saponified by the usual caustic treatment. These substances are soluble in fats and oils. These components comprises for instance higher aliphatic alcohols, sterols, pigments and hydrocarbons. Unsaponifiable matter =
R - ( B + F).100 W
P.51
where R is the weight of residue (g), F is the weight of fatty acid (g), B is the weight of blank (g), and W is the weight of sample (8). Methods: AOCS: Ca 6a-40 and Ca 6b-53; DGF: C-III-la and C-III-lb
9.6 Water Content Karl Fischer reagent reacts quantitatively with water. The far is dissolved in methanol ( H 2 0 c 0.05% w/w) and titrated with the reagent.
where S is the Karl Fischer reagent titration of sample (mL), B is the Karl Fischer reagent titration of blank (mL), X is the water equivalent of Karl Fischer reagent (mg), W is the weight of sample (mg), and
where mH20 is the amount of water added for calibration of Karl Fischer reagent (mg), V is the Karl Fischer reagent titration of added water (mL), and V, is the Karl Fischer reagent titration of blank (d). Methods: AOCS: Ca 2e-84; DGF: C-III-13a
9.7 Phosphorus Content The sample is ashed in the presence of zinc oxide, followed by spectrophotometric measurement of phosphorus as a blue phosphomolybdic acid complex. Methods: AOCS: Cd 12-55; DGF: C-III-16a
Fats and Oils Handbook
806
9.8 Colorimetric Value Several methods to determine color exist. Most of them are based on a comparison of the oil with permanent color standards. The German methods use differently concentrated solutions of inorganic colored salts as standards. To prepare a dichromate standard solution, 0.736 g of potassium dichromate are dissolved in water to loo0 mL. This solution, by definition, possesses the grade 20”. Diluting it to l/x yields the color grade 20/x. The standard iodine color is prepared by dissolving 10 g of iodine and 100 g of potassium iodide with water to loo0 mL, (iodine color 1ooO). To determine the “Lovibond color,” an oil sample is compared with a reflection body of magnesia that is lighted through filters by two sources of light. The color added from the two light beams has to be equal to the color of the sample. As a result of the measurement the color grades from the two light sources and the thickness of the oil cuvette are obtained. Methods: AOCS: Cc 13a-43, Cc 13b-45 and Cc 13c-50; DGF: C-IV-4
9.9 Hexane in Extraction Meal 9.9.1 Free Hexane
This method determines the sum of volatile residual hydrocarbons in extraction meal by heating the sample to 80°C after addition of an internal standard in a closed vessel. After a calibration curve is developed, the hydrocarbons are then determined by headspace analysis by means of gas chromatography using capillary or packed column. Results are expressed as hexane in ppm. 9.9.2 Total Hexane
This method determines the sum of volatile residual hydrocarbons in extraction meal by heating the sample with water in a closed vessel to 110°C. After a calibration curve is developed, the hydrocarbons are then determined by headspace analysis by means of gas chromatography using capillary or packed column. Results are expressed as hexane in ppm. Methods: AOCS: Ba 14-87; DGF: B-II-8a
9.10
Crude Fiber in Meal
This method determines as crude fiber the loss on incineration of a pretreated sample. The pretreatment is carried out by digestion with dilute sulfuric acid and dilute sodium hydroxide, filtration, washing and, drying.
Analytical Methods
807
where S is the loss in weight from incineration of the sample (g), B is the loss in weight from incineration of the blank (g), and W is the weight of sample (g). Methods: AOCS: Cd 8-53 and Cd 8b-90; DGF: C-V 1-6
9.11 Protein in Meal Protein in the meal is determined as 6.25 times the nitrogen content of the sample. Nitrogen is determined by the Kjeldahl method. The sample is heated with sulfuric acid. The ammonia is released from the ammonium sulfate that is formed by means of caustic soda solution. It is absorbed in excess sulfuric acid which is titrated back with alkali solution. Nitrogen =
(B-S).N.0.014.100 (% wt/wt) W
P.91
where S is the alkali back titration of sample (mL), B is the alkali back titration of blank (mL), N is the normality of alkali solution, and W is the weight of the sample (€9. Methods: AOCS: Ba 4a-38, Ba 4b-37, Ba 4c-87 and Ba 4d-90; DGF: B-11-6
9.12 Ash The ash residue after incineration is determined. Incineration is carried out at 600 k 15°C in the AOCS method and 550 k 15°C in the DGF method. The ash content is given as % wtlwt of the incinerated oillfat. A . loo (% wt/wt) Ash = W
[9.10]
where A is the weight of ash (g) and W is the weight of sample (g). Methods: AOCS: Ba 5a-49; DGF: B-11-5
9.13 Solid Fat Content The quantity of solid glycerides is measured by means of pulsed NMR (van den Eyden 1982). Standardized olive oil samples are used as a reference. The sample is completely melted, brought to measuring temperature, inserted into the NMR and measured at 60°C and at the desired temperature after 30 min of equilibration. The mechanism uses the fact that resonance signals can only be obtained from hydrogen molecules that are in the liquid state. NMR equipment is not the high reso-
Fats and Oils Handbook
808
lution apparatus that is used to solve problems of chemical structure but low resolution. Solid Fat Content (SFC) is then determined by the following calculation: SFC =
Reference oil at 60" Sample at 60"
Sample at T Reference at T
E9.111
where T is the measuring temperature ("C). Methods: AOCS: Cd 16-81; DGF:
9.14 Dilatation; Solid Fat Index (SFI) The solid fat index is an empirical measure of the solid fat content, using dilatomehie of a fatloil. An indicator solution (1% aqueous potassium &chromate) is deaerated, as well as the sample that is heated to 80°C. Indicator solution (2 mL) is weighed into the dilatometer bulb. Then the indicator is carefully overlayed with the sample until it overflows. The contents of the dilatometer are then transferred one after the other into water baths and allowed to equilibrate. The reading from the expansion are recorded.
with SFI,, is the solids fat index at measuring temperature T ("C), Dtis the total dilatation (mwkg between T and 60"C), and E is the thermal expansion.
[9.13] with RT is the dilatometer reading at T, Vm is the volume correction for instrument expansion (read from tables), and W is the weight of sample. Methods: AOCS: Cd 10-57; DGF: C-IV 3
9.1 5 Analysis of lipids For analysis of lipids, see, for example, Hamilton and Rossell (1986), Christie (1982), and Pardun (1976) as well as the relevant AOCS and DGF methods.
Chapter 10
Conversion Tables, Abbreviations
The following chapter gives the conversion table between the metric and the American system for the most important measures. Some conversions can also be read from graphs. A table of abbreviationsis included. TABLE 10.1 Conversions from metric to English and English to metric rneasuresa Linear measure: 1 mm =3.937.10-2 1 cm =3.937.1@1 1 m =3.937.10 = 3.281 = 1.094 = 1.094' 103 1 km = 6.214.10-1
inch inch inch feet yards yards mile
1 inch 1 foot
Square measures: = 1.55.10-1 1 cm2 1 m2 =1.076.10 = 1.196 1 ha =1.196. 105 = 2.471
in2 ftz Yd2 Yd2 acres
1 in2 1 ft2
1 yard 1 mile
1 yd2 1 acre
Cubic measures: 1 cm3 =6.100,10-2 1 dm3 =3.532' 10-2 1 m3 =3.532.10 = 1.309 1 m3 =2.838. 10 Volume flow (English): 1 liter = 2.1 = 1.06
in3
1 in3 1 ft3
ft3
ft3 1 yd3 1 bushel
Yd3
U.S. bushel pints liquid quarts
=2.5400 =3.048.10 =3.048.1CF1 =9.144.10 = 9.144.10-1 = 1.609
cm cm m cm m km
=6.452 10-2 = 9.290 102 = 9.290 10-2 =8.361 ,103 = 8.361 10-1 =4.047.10-'
cm2 cm2 cm2 m2 ha
= 1.638. 10 = 2.832 104 = 2.832 10-2 =7.646.10-1 =3.524' 10-2
cm3 cm3 m3 m3 m3
=4.73. 10-1 = 9.46 10-1
liters liters
=3.785
liters
m2
= 0.26
gallons
1 pint 1 liquid quart 1 gallon
Weight: 1 kg 1 t(MT) 1 kgha
=2.205 =1.102 =8.922' 10-1
pound (Ib) short tons IWacre
= 4.536 10-1 1 Ib 1 short ton = 9.074 10-1 1 Ib/acre = 1.12 kg/ha
kg ton or MT
Density: 1 gcm3 1 gcm3
=4.369.106 =6.243.10
grain@ 1b/ft3
1 graidft3 = 2.2884. 10-3 1 Ib/ft3 = 1.6013 10
kg/m3 kgm3
Continued 809
Fats and Oils Handbook
81 0
TABLE 10.1 Continued Coefficient of expansion: 1 g/cm3 "C = 6.243 10
I blft3 "C
IbIft3 "C
=1.601 .lo-'
dcm3 . 10-"C
Pa s gkrn s Pa s
stoke stoke
Kinematic =1 1 v = 1.000
m2/5 cm215
mbar Pa Pa hPa Pa psi
atm
Viscosity: Dynamic 1 poise = 1.000, 10-1 1 poise = 1.000 1 kp s/m* = 9.8067 Pressure: 1 bar
= 1.000. 103
=i.oo0.105 1 mbar = 1.000.102 = 1.000 1 kg/crn2 = 9.8067 lo4 1 kg/cm2 = 1.4224 10
torr
Ib/inz(psi) psi
Soybean measures: 1 MT beans = 3.674. 10 bushels 1 MTmeal = 4 . 6 3 9 . 10 bushels 1 MToil = 2.060 102 bushels
bushel of beans
.ooo,
=1.0133.105 Pa = 1 .OI 33 '1.03 hPa = 1.3332 1O2 Pa = 1.3332 hPa = 6.8948 . 1O3 Pa = 7.0307 1 e2 kgkm2 = 2.720
MT of beans MT of meal MT of oil
= 2.290
= 4.854
TABLE 10.2 Conversion Table Centigrade H Fahrenheit T-3
"F
OC-3
"F
-30 -29 -2 8 -2 7 -2 6 -2 5 -2 4 -2 3 -2 2 -2 1 -2 0 -1 9 -1 8 -1 7 -1 6 -1 5
-22.0 -20.2 -1 8.4 -1 6.6 -14.8 -1 3.0 -1 1.2 -9.4 -7.6 -5.8
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
86 95 104 113 122 131 140 149 158 167 176 185 194 203 212 22 1
-4.0 -2.2 -0.4 1.4 3.2 5.0
OF-,
-2 0 -1 9 -1 8 -1 7 -1 6 -1 5 -1 4 -1 3 -1 2 -1 1 -1 0 -9 43 -7 -6 -5
"C
-28.9 -28.3 -27.8 -27.2 -26.7 26.1 -25.6 -25.0 -24.4 -23.9 -23.3 -22.8 -22.2 -21.7 21.1 -20.6
OF-)
40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
"C
4.4 10.0 15.6 21.1 26.7 32.2 37.8 43.3 48.9 54.4 60.0 65.6 71.1 76.7 82.2 87.8 Continued
Conversion of Units
81 1
TABLE 10.2 Continued
T+ -1 4 -1 3 -1 2 -1 1 -1 0 -9 -8 -7 -6 -5 4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
"F
6.8 8.6 10.4 12.2 14.0 15.8 17.6 19.4 21.2 23.0 24.8 26.6 28.4 30.2 32.0 33.8 35.6 37.4 39.2 41 .O 42.8 44.6 46.4 48.2 50.0 51.8 53.6 55.4 57.2 59.0 60.8 62.6 64.4 66.2 68.0 69.8 71.6 73.4 75.2 77.0 78.8 80.6 82.4 84.2 86.0
OC+
110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 21 5 220 225 230 235 240 245 250 255 2 60 265 2 70 275 2 80 285 290 295 300 305 310 315 320 325 330
"F
230 239 248 257 266 275 284 293 302 31 1 320 329 338 347 356 365 374 383 392 401 41 0 41 9 42 8 43 7 446 455 464 473 482 491 500 509 51 8 52 7 536 545 554 563 572 581 590 599 608 61 7 62 6
"C
OF+
OF+
"C
-3 -2 -1
-20.0 -1 9.4 -1 8.9 -1 8.3
200 210 220 230
93.3 98.9 104.4 1 10.0
0
-1 7.8
240
115.6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
-1 7.2 -1 6.7 -1 6.1 -1 5.6 -1 5.0 -1 4.4 -1 3.9 -13.3 -12.8 -12.2 -1 1.7 -11.1 -1 0.6 -1 0.0 -9.4 -8.9 -8.3 -7.8 -7.2 -6.7 -6.1 -5.6 -5.0 -4.4 -3.9 -3.3 -2.8 -2.2 -1.7 -1.1 -0.6 0.0 0.6 1.1 1.7 2.2 2.8 3.3 3.9 4.4
250 260 2 70 280 290 300 310 320 330 340 350 360 370 380 390 400 41 0 420 430 440 450 460 470 480 490 500 51 0 520 530 540 550 560 570 580 590 600 61 0 620 630 640
121.1 126.7 132.2 137.8 143.3 148.9 154.4 160.0 165.6 171.1 176.7 182.2 187.8 193.3 198.9 204.4 210.0 215.6 221.1 226.7 232.2 237.8 243.3 248.9 254.4 260.0 265.6 271.1 276.7 282.2 287.8 293.3 298.9 304.4 310.0 315.6 321.1 326.7 332.2
4
337.8
Fats and Oils Handbook
812
TABLE 10.3
Abbreviations M ‘O&I
= Million
=thousands
h a sec=s
min a=y t
MT MMT
vh m mm p = km
= metric ton = metric ton = million metric tons = metric tons per hour = meter
= millimeter = micron 1 0 6 m
= hour = annum = second = minute
= year
kW kWh
= kilowatt = kilowatt hours
Pa hPa
= pascal
= hectopascal
Chapter 11
Acknowledgments
I would like to thank the following companies and organizations that have supported me with information and figures: h a f i l t e r B.V., Kwakelkade 28, NL-1823 CL Allunaar, The Netherlands Manufacturers of filtration equipment Buitril, Benz & Hilgers, Postfach, D-40476 Dusseldorf, Germany Manufacturers of margarine wrapper fillers Bernardini, Dr. Ernest0 S.I.B.E. Via Montagne Rocciose 40,1-00144 Roma, Italy Bock & S o h , An’n Slagboom 43,22848 Norderstedt, Germany Manufacturers of margarine wrapper filling machines Chemap AG, P.O. Box, CH 8708 M;innedorf, Switzerland Manufacturers of Funda Filters De Smet Extraction; 265 Prins Boudewijnlaan, B-2520 Edegem-Antwerpen, Belgium Manufacturers of oil processing equipment DLG Verlag, Frankfurt Publishing Company DrM, Dr. Muller AG, P.O. Box, CH 8708 Mmedorf, Switzerland Manufacturers of Fundabac Filters Gerstenberg & Agger, Freyendalsjej, DK-1809 Frederiksberg C, Denmark Manufacturers of margarine processing equipment Grindstedt Products GmbH, DK-8220 Braband, Denmark Manufacturers of emulsifiers Hamba Maschinenfabrik, Postfach, D-42329 Neunkirchen, Germany Manufacturers of margarine and dairy tub filling machines Karlshamns Sweden AB, Karlshamn, Sweden Manufacturers of oil and fat products Kirchfeld GmbH & Co KG, Postfach, 40470 Diisseldorf, Germany Manufacturers of oil processing equipment Korting Hannover AG, Badenstedter Str.56, D-30453 Hannover, Germany Manufacturers of vacuum generation plants 813
81 4
Fats and Oils Handbook
Krupp Maschinentechnik GmbH and Krupp Extraktionstechnik GmbH, Postfach 900552, D-21045 Hamburg, Germany Manufacturers of oil extraction and processing equipment Lurgi GmbH, Sparte 01- und Fettechnologie, Postfach, D-60295 Frankfurt, Germany Manufacturers of oil processing equipment Margarineinstitut fiir gesunde Erniihrung, Hamburg, Germany Margarine promotion activities Schenk Filterbau, P.O. Box 1830, D-73508 Schwabisch Gmiind, Germany Manufacturers of Schenk Filters Schroder & Co, Falkenstr. 5 1-57, D-23564 Liibeck, Germany Manufacturers of margarine processing equipment SKET Schwermaschinenbau, Marienstr. 20, D-39100 Magdeburg, Germany Manufacturers of oil processing equipment Siid Chemie AG, P.O. Box 202240, D-80001 Miinchen, Germany Manufacturers of Tonsil bleaching earth Tetra Laval Fats and Oils AB, S-14780 Tumba, Sweden Manufacturers of oil processing equipment Tirtiaux S.A., Rue de F l e j o u x 8, B-6220 Flews, Belgium Manufacturers of oil processing equipment Unichema International, Postfach, D-46446 Emmerich, Germany Manufacturers of hardening catalysts Westfalia Separator AG, Werner Habig Str. 1, D-59302 Oelde, Germany Manufacturers of centrifuges and decanters
Chapter 12
Bibliography Other than in the respective paragraphs, this chapter lists general literature on fats and oils.
12.1 Books Andersen, A.J.C., (1954) Margarine, Pergamon Press, London. Andersen, A.J.C., (1962) Refining of Oils and Fats for Edible Purposes, Pergamon Press, London. Anderson, L., (1952) The Component Fatty Acids of Oils and Fats, Research Department, Unilever Ltd. Anonymous, (1980) Oilseeds, Oils and Fats, International Association o f Seed Crushers, London 1980 Applewhite, T., (ed.). (1985) Bailey’s Industrial Oil and Fat Products HI, John Wiley & Sons, New York. Bailey, A.E., (195 1) Melting and Solidijcation of Fats, Interscience Publishers, New York. Bailey, A.E., (1951) Industrial Oil and Fat Products, Interscience Publishers, New York. Baltes, J., (1975) Gewinnung und Verarbeitung von Nahrungsfetten, Paul Parey Verlag, Berlin. Bernardini, E., (1985) Oils and Fats Processing I andII, Publishing House Rome. Deuel, H.J. Jr., (1951-57) The Lipids. Their Chemistry and Biochemistry, Vol. I-III, Interscience Publishers, New York. Blank, H., (1957) Weltmacht Fen, Bruchmann Verlag, Munich. Boekenogen, H.A., (1964 and 1968) Analysis and Characterization of Oils, Fats and Fat Products, I and II, Interscience Publishers, London. Boskou, D., (1996) Olive Oil: Chemistry and Technology, AOCS Press, Champaign,
IL. Coleman, M.H., (1963) The Structural Investigation of Natural Fats, in Advances in Lipid Research I, Paoletti R., and Kritchevsky, D., (eds.), pp. 2-64, Academic Press New York, London. DeLuca, H.F. (ed.) (1978) Handbook of Lipid Research II, The Fat-Soluble Vitamins, Plenum Press, New York. Doss, M.P., (1952) Properties of the Principal Fats, Fatty Oils, Waxes, Fatty Acids and Their Salts, The Texas Company, New York. Earp, D.A., and Newall, W., (eds.) (1976) International Developments in Palm Oil, Proceedings of the Malaysian International Symposium on Palm Oil Processing and Marketing, Kuala Lumpur. Eckey, E.W., (1954) Vegetable Fats and Oils, Reinhold Publishing Co., New York 81 5
81 6
Fats and Oils Handbook
Erickson, D.R. (ed.) (1990) World Conference Proceedings, Edible Fats and Oils Processing: Basic Principles and Modem Practices, American Oil Chemists’ Society, Champaign, IL. Erickson, D.R. (ed.) (1995) Practical Handbook of Soybean Processing and Utilization,AOCS Press, Champaign, IL. Galli, C., and Fedeli, E., (eds.) (1987) Fat Production and Consumption, Plenum Press, New York. Godin, V.J., and Spensley, P.C., (1971) TPZ Crop and Product Digest No.1 Oils and Oil Seeds, The Tropical Products Institue, Foreign Commonwealth Office, London. Gunstone, F.D., (1958) An Introduction to the Chemistry of Fats and Fatty Acids, Chapman & Hall, London. Gunstone, F.D., (1%7) An Introduction to the Chemistry and Biochemistry of F a 0 Acids and Their Glycerides,Chapman & Hall, London. (1%9, 1970 and 1972) Topics in Lipid Chemistry Z, ZZ und ZZZ, Gunstone, F.D., (4.) Gresham Press, Old Woking. Gunstone, F.D., Harwood, J.L., and Padley, F.B., (1986) The Lipid Handbook, Chapman & Hall, London. Hamilton, R.J., and Bhati A,, (1987) Recent Advances in Chemistry and Technology of Oils and Fats, Elsevier Applied Science, London. Heinz H.J., (1960) Fette und Fettsauren, in Ullmanns Enzykloptidie der Technischen Chemie, Vol. 7, pp. 454-52; Verlag Urban und Schwarzenberg, Miinchen. ) Chemical Constitution of Natural Fats, Hilditch, T.P., and Williams P.N., (1W7’he Chapman & Hall, London. Hoffmann, G., (1989) The Chemistry and Technology of Edible Oils and Fats and Their High Fat Products, Academic Press, London. Kanfer, J.N., and Hakomori S., (eds.) (1983) Handbook of Lipid Research ZZZ, Sphingolipid Biochemistry, Plenum Press, New York. Kates M., (ed.) (1990) Handbook of Lipid Research VZ, Glycolipids, Phosphoglycolipids and Sulfoglycolipids,Plenum Press, New Yo&. Kirschenbauer, H.G., (1%0) Fats and Oils, Reinhold Publishing, London. Korp, H., and Lindskoug N., (1984) Matfettslexikon, Bokhuset, Helsingborg. Kuksis, A., (4. (1978) ). Handbook of Lipid Research I, Fatty Acids and Glycerides, Plenum Press, New York. Lennerts, L., (1984) dlschrote, dlkuchen, pflanzliche Fette und Ole, Verlag Alfred Strothe, Hannover. Leonard, E.C., (1984) Short Course on Fatty Acids, American Oil Chemists’ Society Education Program,Champaign, IL. Lusas, E.W., Erickson D.R., and Nip W.-K., (1989) Food Uses of Whole Oil and Protein Seeds, American Oil Chemists’ Society, Champaign, IL. Markley, K.S., (1947) Fatty Acids, Interscience Publishers, New York. Martinengln, G.B., (1971) Physical Refining of Oils and Fats, Corbella, Mailand. Mensier, P.H., (1957) Dictionuire h s Huiles Vegetales,Lechevalier Verlag, Paris.
Bibliography
81 7
Paoletti R., Porcellati G., and Jacini G. (eds.) (1976) Lipids Z und ZZ,Raven Press, New York 1976. Pardun, H., (1976) Anulyse der Nahrungsfette, Paul Parey Verlag Berlin. Patterson, H.B.W., (1994) Hydrogenation of Fats and Oils, AOCS Press, Champaign,
IL. Ratledge, C., Dawson P., and Rattray J., (eds.) (1984) Biotechnologyfor the Oils and Fats Industry, American Oil Chemists’ Society, Champaign, IL. Rattrey, J., (1991) Biotechnology of Plant Fats and Oils, American Oil Chemists’ Society, Champaign, IL. Rudischer, S., (1959) Fachbuch &r Margarineindustne, Fachbuchverlag Leipzig. Salunkhe, D.K., and Desai, B.B., (1986) Postharvest Biotechnology of Oilseeds, CRC Press, Boca Raton, FL. Salunkhe, D.K., Chavan, J.K., Adsule, R.N., and Kadam, S.S. (1992) World Oilseeds, Chemistry, Technology, and Utilization,Van Nostrand Reinhold. Schonfeld, H. (ed.) (1936) Chemie und Technologie der Fette und Fettprodukte Z, Chemie und Gewinnung &r Fette, Verlag von Julius Springer, Wien. Schonfeld, H., (ed.) (1937) Chemie und Technologie der Fette und Fenprodukre ZZ, Verarbeitung und Anwendung der Fette, Verlag von Julius Springer, Wien. Schwitzer, M.K., (1951) Continuous Processing of Fats, Leonhard Hill Ltd., London. Schwitzer, M.K., (1956) Margarine and Other Fats, Leonhard Hill Ltd., London. Sinclair, H.M., (1958) Essential Fatty Acids, Butterworth, London. Small, D., (ed.) (1986) Handbook of Lipid Research N,The Physical Chemistry of Lipids, Plenum Press, New York. Swern, D., (4. (1982) ) Bailey’s Industrial Oil and Fat Products Z and ZZ,John Wiley & Sons, New York. Thomas,A., (1978) Fette und Ole, Ullmunns Enzyklopddie der technischen Chemie, Vol. 11, Verlag Chemie, Weinheim. Vanderwal, R.J., (1964) Triglyceride Structure, in Advances in Lipid Research ZZ, (Paoletti, R., and Kritchevsky, D., eds.), pp. 1-16, Academic Press New York. Wachs, W., (1965) Fette und Lipoide (Lipide), Wachse, Harze, in Die Bestandteile der Lebensmittel, (Schormiiller, J., ed.), Springer-Verlag, Berlin. Waite, M., (ed.) (1987) Handbook of Lipid Research V, The Phospholipases, Plenum Press, New York. Wan, P.J., (1991) Introduction to Fats and Oils Technology,American Oil Chemists’ Society, Champaign, IL. Weiss, E.A., (1983) Oilseed Crops, Longman Verlag, London. Williams, K.A., (1950) Oils, Fats and Fatty Foods, J.A. Churchill Ltd.,London.
12.2 Journals Deutsche Lebensmittel-Runhchau, Wissenschaftliche Verlagsanstalt Stuttgart. Fat, Science, Technology, Deutsche Gesellschaft fiir Fettforschung. Fette, Seifen, Anstrichmittel (now Fat Science Technology).
81 8
Fats and Oils Handbook
Food Engineering International, ABC Publishmg, New York. Food Processing Industry, ABC Publishing, New York. Food Science and Technology,Abstracts. Food Technology,Institute of Food Technologists, Chicago. Gordian, Internationale Zeitschnj?firr Lebensmittel und Lebensmittelchemie. INFORM: International News on Fats, Oils and Related Materials, AOCS Press, Champaign, IL. Journal of the American Oil Chemists’ Society, AOCS Press, Champaign, IL. Journal of Food Science, Institute of Food Technologists, Chicago, IL. Journal of Food Science and Technology, Association of Food Scientists and Technologists, India. Journal of Lipid Research, Lipid Research Inc. Lu Rivista Italiana Delle Sostanze Grasse, Stazione Sperimentale degli Oli e dei Grassi, Milano. Lebensmittelwissenschaji und Techologie,Academic Press Lipids, AOCS Press. Milchwissenschaft, Organ der Deutschen Gesellschaft fur Milchwissenschaft, Volkswirtschaftlicher Verlag Munchen. Olkagineur, Revue mensuelle de 1’Institutde Recherches pour 1’Huile et OlCagineux. Olivue, International Olive Oil Council. Oilseeds, Satsouth Ltd & Cambridge Agricultural Publishing. Oils & Fats International,International Trade Publications Ltd. Revue Francuise des Corps Gras, Organe Officiel de L’Institut des Corps Gras ITERG, 1’Association Francaise pour 1’Etude des Corps Gras, la FCdCration Nationale des Industries de Corps Gras. Zeitschnpfur Lebensmitteluntersuchungund Forschung, Springer Verlag, Berlin.
INDEX
Index Terms
Links
A A-unit, see SSHE ABS
765
Acid degumming process
432
Acid value
803
Active carbon
647
Adernic acid
30
Adsorption isotherm
640
Aflatoxin
249
removal
706
Air classification
363
ALCON oil degumming
430
ALCON process
377
Aldehydes, vapor pressure Algae
88
326
oil content
326
Alginates
777
Alkali alcoholate
525
Alkali metal
525
Alloy K/Na
525
Allyl thiocyanate
112
Almond oil, fatty acid composition
313
Į-modification, transition time
706
671
696
790
791
323
fatty acid composition
properties
664
313 77
Index Terms Animal fats production flow chart
Links 121 122
Animal feed
203
Annatto
747
Antitrypsine factors
225
427
Arachic acid
60
64
Arachidonic acid
30
31
metabolic importance
31
Ascorbyl palmitate
736
Ascorbyl stearate
736
Ash content, analysis
807
Aspergillus flavus
249
Aspergillus niger
102
Atomic volume
574
Autoclave
139
technical data
264
140
140
Autoxidation
100
Avocado kernel oil, fatty acid composition
220
Avocado oil
217
fact file
221
fatty acid composition
220
price
222
production process
222
properties
221
Avocado, botany
217
composition
217
harvest
221
yearly production
221
yield
217
222
220
57
63
65
Index Terms
Links
B B-unit
760
Babassu meal
299
Babassu nuts
296
cracking
373
Babassu oil
294
fact file
300
301
fatty acid composition
299
301
price
301
production process
300
properties
298
Babassu, botany
294
composition
298
economic importance
296
harvest
297
history
294
yearly production
297
Bacteria fats
321
Bakery margarine
774
Baku fat
506
Basket extractor
419
Batch deodorizer
677
Batch extractor
406
Beater machine Beater mills Beef tallow consumption
151 23
definition
152
fact file
155
506
Index Terms
Links
Beef tallow (Cont.) fatty acid composition
154
155
fractionation tree
495
499
price
16
18
triglyceride composition
70
154
yearly production
10
121
Beef tallow fractions, fatty acid composition solid fat content
155
152
496 497
498
Behenic acid
57
60
Belt conveyor
197
Belt extractor
402
Benzoic acid
746
BHA
736
785
BHT
736
785
Binary systems
444
Bixin
747
Black run
654
Bleaching
638
Bleaching agents
643
active carbon
647
amounts necessary
642
comparison of
647
data
648
filtration
653
silicates
647
Bleaching earth
640
amount
642
absorbed oil
664
activation
645
extraction
665
64
Index Terms
Links
Bleaching earth (Cont.) natural
644
oil recovery
664
synthetic
647
Bleaching plants
648
Bleaching, batch
649
continuous
651
energy consumption
652
heat
666
oil humidity
643
oil pretreatment
652
oxidation during
649
processing flow chart
649
processing parameters
642
reaction rate
641
semicontinuous
650
success, temperature dependency
643
644
temperature
640
643
644
theory
640
time
640
642
643
velocity constant
644
water content of oils
643
Boiling point, fatty acids
89
Bollmann extractor
409
Bone oil
147
production
147
Borneo (Illipé) nut
307
composition
307
644
644
668
Index Terms Borneo (Illipé) tallow
Links 303
fact file
309
fatty acid composition
307
price
309
triglyceride composition
308
Braccatura
217
Breast milk
1
Bridge formation
654
Broken beans, during filling
195
Bucket conveyor
200
Buffalo milk
124
Bulk density, oil milling
362
seeds
193
Buss reactor
595
Butter
719
Butter consumption
23
194
721
Butter fat, see butter oil Butter making
727
Butter making machine
728
Butter milk
729
Butter mountain Butter oil fractions, fatty acid composition fractionation tree Butter oil fractions, solid fat content
21 500 499 500
fact file
132
fatty acid composition
133
fractionation
499
fractionation tree
495
from butter
127
from cream
127
499
Index Terms
Links
Butter oil fractions, solid fat content (Cont.) iodine value
125
production flow chart
128
production plant
139
triglyceride composition
131
Butter, C-value
724
composition
721
economic importance
721
fat globules
722
half-fat butter
731
half-fat butter production process
724
legislation
721
price
21
132
reconstituted
730
special products
731
water content
723
729
10
125
yearly production Buttering
730
727
Butylhydroxyanisole, see BHA Butylhydroxytoluene, see BHT Butyric acid
60
64
721
751
774
C C-unit see crystallizer C-value butter
724
C-value margarine
749
Cage length, extraction press
535
Cage, screw extraction press
386
Index Terms Cake composition
Links 386 206
Cake breaker
389
Cake formation in filtration
655
Camel milk
124
Campesterol
109
Candle filter
658
Capric acid
57
60
64
Capronic acid
57
60
64
Caprylic acid
57
60
64
Carbohydrates
177
Carbon dioxide, extraction with
432
614
properties
433
Carban disulfide
395
Carotene
107
109
Carotenoids
107
110
Carousel extractor
410
411
concentration gradient
410
technical data
412
Carragheenans
777
791
Carrier, see support Castor bean oil, annual production Castor beans
12 315
composition
315
harvest
313
hectare yield
313
world production
314
316
640
642
Index Terms Castor oil
Links 311
fatty acid composition
316
price
316
Catalyst, hardening, see hardening catalyst
555
interesterification
523
losses
526
Cattle composition
153
Cattle stock
152
Cattle, slaughtering
133
CBE Cocoa butter equivalents
501
CBR Cocoa butter replacers
501
fatty acid composition
506
solid fat content
506
starting raw materials
505
Cell wheel extractor, see carousel extractor Centrifugal discharge filters
661
Centrifuges
353
neutralization
629
Cerebronic acid
63
65
Cerotic acid
60
64
Cervonic acid
63
65
Ceylon pipes
451
Chlorophyll
640
642
Cholesterol
32
106
in food
28
108
DHL, LDL
32
structure
109
Churn
729
Churn drum process
756
108
109
Index Terms
Links
Churning
727
757
Citric acid
682
723
Citric acid esters
796
Clarification decanter
637
Clarification separator
356
Clarifixator
127
Classification of oils
175
Clausius Clapeyron equation
670
Cleaning seeds
363
Cleaning, exhaust air
421
Cloning, oil palms Closed rework Clupanodonic acid
637
8 762 63
CMC
777
Cocoa beans, composition
289
yearly production
287
yield
287
Cocoa butter
287
equivalents (CBE)
449
replacers (CBR)
449
composition
288
fact file
291
fatty acid composition
289
interesterified
534
price
192
production process
290
properties
288
solid fat content
534
triglyceride composition
290
65
506
291
745
Index Terms Cocoa, botany
Links 287
economic importance
287
fermentation
288
harvesting
288
history
287
Coconut expeller cake
264
Coconut meal
264
Coconut oil
260
fact file
265
266
fatty acid composition
177
263
266
15
17
266
price production process
265
properties
261
triglyceride composition Coconuts
70 260
botany
264
composition
261
cracking
372
economic importance
260
harvesting
264
history
260
yearly production
261
Cod liver oil
170
Coenzyme-A-complex
177
Coffee oil
314
fatty acid composition
263
314
Coffee whitener
792
Colloid mill
789
Color measurement
806
262
267
Index Terms
Links
Colorants, margarine
747
Colorimetric value
806
Column, packed
699
Complector
758
Condensation, miscella
423
vapors
427
Conditioning
379
Contiblex process
665
Cooling curves, cocoa butter
507
fractionation
469
lard
536
oils, fats.
700
693
73
palm oil mid-fraction
507
wet fractionation
476
Cooling drum
758
Copper catalyst
559
Copper sulfate, crystal growth
465
Copra
261
Copra cutter
374
Copra, storage
195
Corn expeller cake
294
Corn oil
291
262
fact file
295
296
fatty acid composition
293
295
price
296
production process
295
properties
292
triglyceride composition
70
293
Index Terms Corn, botany
Links 291
composition
292
economic importance
292
Cotton meal Cottonseed oil annual production
234 9 10
fact file
235
fatty acid composition
233
235
price
235
237
production process
234
235
properties
232
triglyceride composition Cottonseed, botany
70 229
composition
232
dehulling
369
delinting
369
economic importance
230
harvest
234
history
229
yearly production.
231
yield
233
13
Cow’s milk
124
Cracked seed. depending on humidity
195
Cracking, babassu nuts
373
coconuts
372
palm nuts
372
Cracklings
135
Cream
719
composition
722
fat droplet
728
181
142
231
Index Terms
Links
Cream (Cont.) at droplet size
727
fat droplet structure
727
ripening
725
souring
725
Cream margarine
773
Critabolites
558
Critical nucleus
462
Crude fiber
806
Crystal fat powder
781
783
Crystal growth
461
465
71
461
Crystal network
737
738
Crystallization
458
478
Crystal modification of fats
rate
461
heat of
79
stages
459
time
76
Crystallizer
760
Cycle times hardening
594
Cycle times of filters
658
Cycle times, SCD
680
D Darcy’s law Dead-end process Decadienal
654 93 670
755
Index Terms Decanter
Links 354
clarification zone
354
drying zone
354
olive oil production
358
three-phase
354
Decatrienal
670
Degumming
429
silica, bleaching earth
430
via centrifugation
429
Dehulling
636
432
366
machines
367
368
cottonseed
369
370
jojoba seed
373
peanuts
371
rapeseed
371
safflower seed
372
soybeans
368
sunflower seed
371
Delinting
369
Density of miscella
397
Density, specific Deodorization
372
370
81 667
continuous
680
cycle times
680
direct heating
690
discontinuous
676
energy consumption
683
heat exchange
690
heating the oil
690
history of
669
687
Index Terms
Links
Deodorization (Cont.) influencing factors
673
plants
667
pressure
674
process comparison
694
processing conditions
672
processing steps
676
semicontinuous
677
stripping steam
675
temperature
674
theory
670
thermal heating oil
690
time
674
vacuum
691
Deodorizer, continuous
697
684
semicontinuous
679
semicontinuous cycle times
680
semicontinuous temperature profile
680
Desolventizer
425
sizes
427
toaster cooler
426
Desolventizing
424
meal
424
681
682
723
Detergents, see Lanza fractionation Dewaxing, see winterization Dextrose
790
Diacetyl
670
721
Diacetyl formation
721
723
Diacylglycerides, see diglycerides
725
Index Terms
Links
Dienic acid
550
Diffusion
581
Diffusion coefficient
580
581
Diffusion of hydrogen
580
581
Diffusor
691
Digestibility of extraction meal
204
Diglycerides, melting point
78
Dilatation
81
Dilatation curve
81
205
427
82
808
Disk filters, see centrifugal discharge filter Distribution, even of fatty acids
66
minimum of fatty acids
66
restricted statistical of fatty acids
66
statistical of fatty acids
66
Docosaheptanoic acid
30
Dosing head. margarine filling
770
Double Zero Rape
179
Dowtherm process
690
Dressed weight, cattle
153
pigs
183
149
Dripping point, interesterification
529
Droplet size, olive oil
353
Drum complector process
756
758
Drum conditioner
379
381
Drum filter
485
Drum, cooling
756
Dry degumming
431
382
Index Terms Dry fractionation
Links 467
cooling process
468
flow chart
468
principle
467
process
467
Dry rendering
132
plant
135
processing flow chart
136
Drying, seeds
187
Dumori fat
506
E Edible tallow, see beef tallow EDTA
736
Egg yolk
786
Eicosenic acid Elaeidobius kamerunicus
788
65 208
Elaeostearic acid
63
65
Elaidic acid
62
65
Electro separator
369
Electrolytical hydrogen
567
Electrophilic addition
548
Emulsification devices
754
Emulsifiers, HLB value
795
Emulsifying
754
Energy balance, renewable sources Energy content, fats Energy production from palm residues
41 1 349
176
Index Terms Energy requirement. bleaching
Links 652
conveying
197
drying of seeds
192
extraction
417
extraction solvent recovery
424
hardening
594
hydrogen raising
569
Lanza fractionation
473
neutralization
652
oil extraction
417
olive oil extraction
360
palm oil fractionation
475
refining
704
winterization
511
439
Environmental contaminants, removal during refining
704
Enzyme cost, interesterification
545
Enzymes. fatty acid specific
542
non-specific
542
specific
542
Enzymic hydrogenation
541
Enzymic interesterification
540
ENZYMAX degumming
431
Erucic acid
54 179
Eutectic mixture Even distribution, fatty acids
455 66
Expander
377
Expelling
380
62
65
125
178
Index Terms
Links
Extraction curve, hexane
394
Extraction meal. composition
206
digestibility
204
protein composition
204
protein content
204
Extraction of oil
345
Extraction plants
406
Extraction rate
390
flake thickness
404
temperature dependency
401
Extraction solvent
205
427
395
amount needed
402
boiling range
399
carbon disulfide
395
environmental friendliness
395
extraction potential
395
hexane
397
399
physical data
396
397
properties
395
separation
422
temperature
400
Extraction stages, determination of
393
Extraction temperature, CO2 extraction
434
Extraction time
401
Extraction. energy requirment
417
particle size in
404
propane in
437
supercritical gases
430
temperature
400
time
401
401
439
402
399
Index Terms
Links
Extraction. energy requirment (Cont.) two-phase
396
with CO2
430
Extractors
406
Extruder
377
Extrusion
377
extraction yield
437
378
F Fat composition, margarine
739
753
7
34
per capita
7
34
Fat content, feces
1
Fat consumption
human tissues livestock mother’s miIk non oil seeds
28 134 1 223
processed food
6
unprocessed food
5
Fat crystal powder
781
783
Fat crystals, margarine
737
738
737
738
network Fat globules, butter
739
cream
727
size distribution
727
structure
727
Fat melanges
778
Fat metaboliism Fat powder
29 781
783
Index Terms
Links
Fat replacers
44
Fat substitutes
44
Fat tax
24
Fats, hardened medium-chain fatty acids
545 793
world production
6
world production in regions
8
Fatty acid composition, algae fats
7
326
almond oil
313
avocado oil
220
babassu oil
299
301
beef tallow
154
155
beef tallow fractions
496
borneo tallow
307
butter oil
133
butter oil fractions
500
castor bean oil
316
cocoa butter
289
291
coconut oil
177
263
coffee oil
314
corn oil
179
cottonseed oil
233
dependent on fractionation
490
depending on seed ripening
177
different safflower seed species
181
fish liver oil
171
fish oil
162
fulwah tallow
313
235
163
266
Index Terms
Links
Fatty acid composition, algae fats (Cont.) goose fat
158
grape seed oil
302
hazelnut oil
313
hemp seed oil
314
human body fat
305
28
jojoba oil
319
lard
150
lard fractions
495
linseed oil
279
mowrah butter
313
mustard seed oil
314
mutton tallow
156
niger seed oil
306
oat bran oil
313
olive oil
215
218
palm kernel oil
274
277
palm oil
210
212
peach kernel oil
314
peanut oil
179
pecan nut oil
314
poppyseed oil
314
poultry fat
157
pumpkin kernel oil
313
rapeseed oil (HEAR)
281
247
251
179
255
258
rapeseed oil (LEAR)
179
255
258
rice bran oil
311
safflower seed oil
179
284
287
sesame seed oil
269
272
Index Terms
Links
Fatty acid composition, algae fats (Cont.) Shea butter
313
soybean oil
226
229
soybean oil hardened
573
575
soybean oil hardened
574
575
sunflower seed oil
179
240
tea seed oil
314
tung oil
317
walnut oil
309
whale oil
159
wheat germ oil
313
Fatty acid distribution changes, interesterification
537
Fatty acid methyl esters
40
Fatty acid, usage
38
Fatty acids
57
monounsaturated
61
polyunsaturated
61
69
saturated
58
60
body fat
28
chemistry
57
cis-, trans-
59
free (FFA)
615
free, development during storage
134
medium chain
57
melting dilatation, nomenclature occurrence oxidation rate
58 64 102
244
Index Terms
Links
Fatty acids (Cont.) physical data
60
removal
616
specific enzymes
542
structure
56
systematic
58
threshold values odor
668
threshold values taste
668
vapor pressure
87
88
Fatty alcohols
38
39
Fatty amides
38
Fatty amines
38
Fermentation, cocoa beans
39
288
FFA, see fatty acids free Filling process, margarine
766
Filter aid
655
Filter cloth
480
655
Filter press
479
655
Filter trough
485
Filter, cycle times
658
Miscella filtration Filtration, black run
423 654
blade filter, see leaf filters, cake thickness
657
candle filter
658
disk filter, see centrifugal discharge filters hardening catalyst
597
plate filters
656
pore size of filter cloth
656
671
696
Index Terms
Links
Filtration, black run (Cont.) rate in fractionation
487
throughput
657
Fire point Fish liver oil fatty acid composition
95 170 171
Fish meal
167
Fish oil
160
fact file
163
fatty acid composition
162
163
16
18
163
161
price production process
162
yearly production
10
121
404
405
Flake thickness extraction rate
404
Flaking
374
Flaking mill
376
Flash point
95
Flat angle decanter
639
Flavor development in soured milk
723
Fluted breaker rolling mill
375
Flux rate, membrane filtration
516
Folding of wrappers
767
Foreign material in seeds
363
Fractionation
499
377
beef tallow
493
cooling curves
466
469
double stage
493
502
energy requirement
471
history
450
476
Index Terms
Links
Fractionation (Cont.) lard
492
palm oil
497
palm oil glyceride classes
453
palm oil separation curve
487
plants
469
scheme
457
separation sharpness
487
Fractionation techniques
466
fatty acid composition
490
melting point
490
olein composition
490
solid fat content
488
triglyceride classes
491
Fractionation tree
456
Frame belt extractor
413
488
Free fatty acids, see fatty acids free, Freundlich adsorption isotherm
640
Fritz proces
729
Frying oils
782
Fuel esters
41
Fuller’s earth
644
Fulwah tallow
313
641
G Gadoleic acid
62
65
Gassing temperature
591
593
Germination ability
193
Glucose syrup
790
792
Index Terms
Links
Glucosinolates
112
Glycero phospholipids
104
Glycerol
56
Goat milk
124
Gondoic acid Goose fat
fact file
157
fatty acid composition
158 35
234
300
amount available
301
composition
302
Grape seed meal
303
Grape seed oil, fact file
305
fatty acid composition
302
price
305
production process
304
Greaves, see cracklings, Groundnuts, see peanuts, Group extractors
407
Guar gum
777
H Half-fat butter
112
157 156
Grape seed
179
62
definition
Gossypol
114
731
processing
731
production
731
Half-fat margarine
776
emulsifiers
777
formulations
777
305
Index Terms
Links
Half-fat margarine (Cont.) production
776
stabilizers
777
Halibut liver oil
170
Hammer mills
352
372
553
597
Hardening (see also hydrogenation) Hardening catalyst microphoto
557
nickel carrier
557
nickel support production flow chart
558
nickel technical data
563
novel nickel-based
562
poisoning
588
PRICAT
564
production
555
Hardening catalyst, recycling
591
562
Hardening catalyst, structure and texture
563
support-free
555
support-free production flow chart
556
Hardening time, C18 fatty acids
575
iodine value
576
solid fat content
574
Hardening, batch
592
catalyst concentration
583
changes in fatty acid composition
553
changes in solid fat content
553
continuous
596
crude oil pretreatment
590
cycle times
594
575
Index Terms
Links
Hardening, batch (Cont.) energy consumption
594
heat of reaction
573
history
546
hydrogen consumption
589
hydrogen pressure
584
hydrogen quality requirements
566
iodine value
576
577
584
588
580
582
580
584
588
580
584
588
584
586
isomerization
589
kinetics
550
loop reactor
595
mass transfer
579
mechanism
547
melting point
577
pretreatment
667
process
591
processing conditions
572
processing flow chart
593
raw material requirements
590
reaction rate
582
reaction time
577
stirrer speed
582
structural equation
547
techniques
589
temperature
573
theory
547
trans fatty acids
577
580
590
602
588
Index Terms Hazelnut oil, fatty acid composition properties
Links 313 313
HDL
32
HDPE
765
HEAR, see rapeseed, high erucic acid Heat bleaching, palm oil
666
Heat of evaporation
86
89
Heat of fusion
79
81
Heat of transition
76
Heat treatment, seeds Heat, specific Hectare yields, castor seed
379 74 313
cocoa beans
287
cottonseed
13
181
depending on irrigation
184
185
depending on plant density
182
depending on seeding time
182
depending on soil quality
183
depending on variety
183
linseed
279
peanuts
246
rapeseed
12
safflower seed
284
sesame seed
268
soybeans sunflower seed
12
138
Hemp seed oil, fatty acid composition
314
properties
13
252
13
224
284
Helix sterilizer
314
231
139
253
Index Terms
Links
Heptadienal
670
Heptenal
670
Herring oil Hexagonal crystals Hexane
71 395
determination
806
explosion limits
400
free
806
total
806
High oleic seeds
178
High pressure extraction
432
High PUFA
183
Hildebrandt extractor
418
HIPS
765
HLB value
745
754
emulsification
745
754
emulsion type
745
of emulsifiers
795
Horizontal cooker
381
Horizontal tank filters
662
Horse milk
124
Hulls, oil seeds
367
Human milk
124
Hydratation of phospholipids Hydrocarbons (lipids) extraction solvents
105 395
Hydrogen diffusion
581
Hydrogen for hardening
564
Hydrogen pressure, hardening
576
795
Index Terms Hydrogen raising energy consumption
Links 564 569
Hydrogen solubility
579
Hydrogen, composition of crude
571
electrolytic
567
physical data
565
price
565
purity for hardening
566
steam iron
566
steam reforming
569
Hydrogenation, kinetics
550
Hydrogenation, see also hardening Hydrolytic fat splitting Hydronervonic acid
102 63
Hydroperoxides
100
Hydroxypropylcellulose
790
Hygroscopic equilibrium, seeds
189
65
I Illipé butter
70
303
see borneo tallow Illipé nuts, see borneo nuts Immersion
400
IMMEX extractor
416
Interesterification
516
batch
532
catalysts
523
chemical equation
519
continuous
532
cycles
530
419
506
Index Terms
Links
Interesterification (Cont.) directed
522
directed processing flow chart
531
effect of
517
enzymic
541
enzymic, enzyme cost
545
enzymic, olive and coconut oil
543
enzymic, olive oil and stearic acid
543
enzymic, palm oil mid-fraction and stearic acid
544
mechanism
519
melting point
518
Na/K alloy
525
of lard
493
patents
525
plants
531
principle
517
process
528
processing flow chart
529
random
528
raw materials
525
solid fat content
518
stereo specific
542
temperature
529
Iodine value
804
analysis
804
Iron separator Isomerization, geometrical
363 99
hardening
589
positional
99
Isothiocyanic acid
112
530
538
365
366
Index Terms
Links
J Jojoba
317
Jojoba oil
317
fatty acid composition
319
properties
319
Jojoba seed
318
composition
318
dehulling
373
K K/Na alloy Ketones, vapor pressure Kieselguhr
525 88 558
calcinated
558
particle size distribution
558
Killing
671
559
130
Killing fats, see rendered fats Kombinator
760
L Lactlic cream butter
728
Lactic culture
726
Lampante
219
Langmuir
640
Lanza fractionation
471
energy consumption
473
plants
473
principle
471
763
696
Index Terms
Links
Lanza fractionation (Cont.) process
472
processing flow chart
473
Lard consumption
148
506
23
definition
151
act file
151
fatty acid compsition
150
price
16
18
151
triglyceride composition
70
150
yearly production
10
121
149
Lauric acid
54
57
60
Lauroleic acid
62
65
LDL
32
LDPE
765
Leaf filters
661
64
LEAR, see low erucic acid rapeseed Lecithin
103
applications
743
production
429
sludge
429
Lifetime, Į-modification
77
Lignoceric acid
57
Linderic acid
62
Linoleic acid
30
dietary importance Linolenic acid
743
60
64
31
54
63
50
63
65
31 30
Linseed
276
Linseed meal
280
65
Index Terms Linseed oil
Links 9
fact file
281
fatty acid composition
279
price
281
production process
281
propenies
279
triglyceride composition
280
yearly production
11
botany
276
composition
278
economic importance
278
harvest
281
history
276
yearly production
278
yield
279
Linters
369
Lipids
103
analysis
808
Lipochromes
107
Lipolysis
102
Lipovitamins
108
Liprofrac process
471
Liver oil
170
fatty acid composition
170
Long mix process
624
Loop reactor
595
276
281
280
279
Index Terms Loss, harvesting
Links 185
insects, diseases, weeds
186
postharvest
186
preharvest
185
winterization
511
Lovibond color
644
Lye, influence on amount needed
618
influences on excess needed
620
186
806
M Maize see corn Mammalian milk composition Margaric acid Margarine
123 57 732
baking margarine
774
C-value
749
colorants
747
composition
739
consumption
751
774
23
733
734
cream margarine
764
773
economic importance
733
emulsifiers
743
energy consumption
778
fat blends
739
fat crystal structure
738
flavors
746
half-fat margarine
776
history
732
ingredients
743
744
753
Index Terms
Links
Margarine (Cont.) lecithin
743
legislation
734
MCT
793
packing
763
physical properties
748
price
21
processing
752
processing flow chart
764
processing lines configuration
761
processing units
761
production
751
production volume
734
puff pastry margarine
774
solid fat content
750
structure
736
tub filling
766
water
747
water droplets
738
wapping
766
Marine oils
156
Mass crystallization
459
Mass transfer, hardening
579
Mayonnaise
786
Mayonnaise, composition
789
legislation
788
MCT (medium-chain triglycerides) (MCT)
793
Medium-chain triglycerides
793
Melting dilatation
79
82
Index Terms
Links
Melting point difference, isomers
59
Melting point, depending on crystal modification
71
fatty acids
60
fatty acids, cis modification
59
fatty acids, trans modification
59
hardened oilsfats
598
interesterfication
518
mono-diglycerides
77
795
symmetrical triglycerides
71
75
triglycerides, depending on fatty acid
72
triglycerides, depending on structure
72
Membrane dewaxing
511
mass balance
516
plant
513
process
513
processing flow chart
515
Membrane filter presses
479
Membrane filtration
480
flux rate
516
Menhaden oil Metabolism of essential fatty acids
30
Metal detector Methylnonylcarbinole Mège Mouriés
88 732
Microorganisms as fat sources Milk fat, see butter oil Milk fats
122
Milk production volume
125
Milk proteins
123
514
Index Terms
Links
Milk souring
723
753
Milk, composition
124
722
production
126
properties
132
yearly production
123
125
fatty acid composition
124
133
Mimimum distribution of fatty acids
67
Mincer
141
142
144
Mineral white oil
421
427
428
Miscella, boiling point
399
condensation
423
density
397
distillation
423
filtration
420
422
423
oil content immersion
400
418
oil content percolation
400
420
oil recovery
420
refining
626
solvent recovery
422
temperature and phosphatide content
402
vapor pressure
398
winterization, see also solvent winterization working up
422
Miscibility gap
444
Mixed crystal
444
Mixing (olive oil)
352
Modification
446
Moisture, seed storage
188
Index Terms
Links
Mold, fatty acid composition
323
Molds
321
oil content
321
Mono-diglycerides
744
composition
795
Monoacylglycerides, see Monoglycerides Monoenic acid
58
550
Monoglycerides
744
794
composition
794
melting point
795
surface tension
795
Montmorillonite
645
Mother’s milk
124
Mowrah butter
506
fatty acid composition
313
properties
313
Multihead proportioning pump
752
Must, olive must
346
357
346
347
palm must Mustard seed oil
358
314
black
314
white
314
Mutton tallow
153
fact file
156
fatty acid composition
156
506
Myristic acid
54
60
Myristoleic acid
62
65
64
Index Terms
Links
N n-3 fatty acids
30
N-oil
45
Na/K alloy
525
Neat’s foot oil
153
Nervonic acid
63
Neutralization
615
Neutralization, adsorption
616
Neutralization, alkali
615
amount of lye
618
batch cycle times
622
batchwise
621
continuous
622
distillative
616
energy requirement
652
excess amount of lye
620
extraction
616
long mix process
624
reesterification
616
semicontinuous
622
short mix process
624
via centrifugation
622
with alcohol hexane
617
Zenith process
622
Neutralizing vessel, schematic
621
Nickel catalyst, production
555
structure
557
technical data
563
31
34
Index Terms
Links
Nickel formiate
556
Nickel sulfate
557
Niger seed
301
composition Niger seed oil
306 301
fact file
307
fatty acid composition
306
price
307
Nisinic acid
63
Nitrogen
747
Nizo process
730
Non-dairy cream
790
Nonadecene
88
Nonadienol
670
Nonanone
88
Novel seed oils
179
Nucleation
461
Nucleation rate
461
Nucleation, primary
462
secondary
462
fat consumption recommendations
1 30
O Oat bran oil
313
Odorous components, oil
670
Off taste
670
Oil consumption
22
65
22
23
30
Index Terms Oil demand
Links 19
Oil foots separator
387
Oil mills, running cost
440
Oil palm
8
Oil purification
613
Oilseeds, foreign material
363
hull content
367
preparation process
362
reduction
373
Oil/bleaching earth slurry
648
Oils, hardened
545
storage
201
transport
201
Oil-soluble ingredients
753
Oleic acid
54
Olein yield
487
winterizing hardened soybean Oleo chemistry, production
62
785 38
products
38
raw materials
40
Oleohexacosane
88
Oleohcxadecene
88
Oleononadecene
88
Oleopalmitate
475
Oleosins
178
Oleostearate
465
Oleotetracosane
88
Oleotricosene
88
506
506
65
Index Terms
Links
Olcotridecene
88
Olestra
46
Olier extractor
415
Olive crushing
351
Olive husk, processing
359
composition
359
extraction
359
Olive kernel oil fatty acid composition Olive oil Olive oil production, energy consumption yield
294 296 9
346
360 360
Olive oil, definition
219
droplet size
353
fact file
217
fatty acid composition
215
218
price
217
219
production process
216
218
properties
214
solids content
219
triglyceride composition
216
yearly
10
Olives, botany
212
composition
214
economic importance
215
harvest
216
history
212
yearly production
216
yield
216
214
217
350
Index Terms Orthorhombic crystals
Links 71
Oxidation during bleaching
649
Oxidation of fatty acids
102
Oxidation reaction rate
102
Oxidation stability
784
Oxistearin
784
Oxystearin
789
P P/S ratio
32
PA
765
Pack density, oil droplets
728
Packaging material for margarine
765
Packing machine, tubs
771
wrappers
768
Packing material, transmission
786
Packing of tubs
766
Packing of wrappers
766
PAH
707
Palm fruit, botany
206
composition
206
economic importance
209
harvest
211
history
206
Palm kernel meal Palm kernel oil
789
772
275 9
273
fact file
276
277
fatty acid composition
274
277
price
277
773
Index Terms
Links
Palm kernel oil (Cont.) production process
275
properties
273
triglyceride composition
275
Palm kernels, botany
273
composition
273
economic importance
273
harvest
274
yearly production
273
Palm nuts cracking Palm oil
273
348
372 9
206
composition
208
double fractionated
501
fact file
211
213
fatty acid composition
210
212
fractionation tree
501
fractionation, energy consumption
475
fractionation, separation curve
487
fractionation, triglyceride classes
488
70
fractions, properties
497
fractions, solid fat content
504
fractions, triglyceride classes
447
heat bleaching
666
interesterified, fractionation tree
502
microphoto of crystals
480
mid fraction, cooling curve
507
physical refining
695
price
346
14
503
17
213
506
Index Terms
Links
Palm oil (Cont.) production process
212
properties
208
solid fat content
213
triglyceride classes after interesterification
501
triglyceride composition
210
yearly production
347
10
211
Palmitic acid
54
60
Palmitoleic acid
62
65
Partial pressure
670
Peach kernel oil, fatty acid composition
314
properties
314
Peanut butter
792
Peanut meal
248
Peanut oil
9
242
fact file
250
251
fatty acid composition
247
251
15
17
price production process
250
properties
244
triglyceride composition Peanuts, botany
64
70
247
242
composition
246
dehulling
371
economic importance
243
harvest
248
history
242
yearly production
246
yield
246
249
251
252
Index Terms Pecan nut oil, fatty acid composition properties Pectines
Links 314 314 777
Pentadecene
88
Pentylfuran
670
Percolimm plant
417
Perforated belt filter, see vacuum belt filter Perilla oil, fatty acid composition Peroxide value
804
Pesticides
710
PET
786
PETG
765
Petroselenic acid
62
PG
785
Phase diagrams
454
of triglycerides
65
455
Phase inversion
720
728
Phosphatides
103
402
occurrence
104
Phosphatidylcholine
104
Phosphatidylethanolamine
104
Phosphatidylinositol
104
Phosphatidylserine
104
Phospholipids
103
Phosphoric acid
429
Phosphorous content
805
Phulawara tallow
506
737
754
Index Terms
Links
Physical refining
695
column
698
comparison with chemical process
700
energy consumption
699
fatty acid condensation
699
investment
702
model of plant
703
oil pretreatment
696
palm oil
700
processing conditions
697
processing steps
613
theory
695
packed column
699
Phytosterols ɩ-complex Pigs, body composition
697
106 548 134
development of adipose tissue
134
slaughtered
133
stocks
149
Pipe conveyor
196
Piperine
463
Plate filter press
655
Platinum metals, hardening catalyst
560
Polydextrose
45
Polyenic acid
58
Polymerization
99
Pomace oil
704
219
149
Index Terms Poppy seed oil
Links 314
fatty acid composition
314
properties
314
Positional specific interesterification
542
Poultry fat
156
fatty acid composition
157
PP
765
Preform
787
Premier jus
152
Premix process
752
Preservatives
746
Press extraction, oil production
380
residual oil content
384
Pressure, expelling
384
PRICAT catalysts
545
Price difference, soybean oil vs. diesel oil soybean oil vs. ethylene Prices, oils and fats
42 39 14
Processing conditions, hardening
572
Processing flow chart, acid degumming
432
ALCON process
378
animal fat production (lard, tallow)
142
animal fat production overview
122
animal fat production with rendering vessels
145
animal fat solvent extraction
148
avocado oil production
222
babassu oil production
300
batch bleaching
651
batch deodorization
678
Index Terms
Links
Processing flow chart, acid degumming (Cont.) batch neutralization, bleaching and interesterification
530
biochemical processes during seed aging
193
bleaching
649
butter oil production from butter
128
butter oil production from milk
130
butter production
724
chemical and physical refining
614
cleaning of waste air and vapors
421
cocoa butter production
290
coconut oil production
265
continuous butter making
728
continuous neutralization
623
corn oil production
295
cottonseed oil production
235
crystal fat powder production
782
degumming processes
430
degumming, dewaxing, refining
627
dehulling of soybeans
370
delinting and dehulling of cottonseed
370
deodorization
676
directed interesterification
531
double stage wet fractionation
477
dry fractionation
468
dry rendering process
136
fat slab production
780
fish liver oil production
166
431
Index Terms
Links
Processing flow chart, acid degumming (Cont.) fish oil production
166
fish oil production with decanters
169
grape seed oil production
304
half-fat butter production
731
hardening
593
interesterification
529
lactic culture production
726
Lanza fractionation
473
linseed oil production
281
margarine production
752
margarine wrapping
766
mayonnaise production
787
medium-chain triglyceride production
794
membrane dewaxing
515
miscella refining
628
miscella winterization
512
modification processes
446
mono- and monodiglyceride production
796
neutralization with alcohol and hexane
617
neutralization with alkali lye
618
nickel support catalyst production
559
novel nickel catalyst production
562
oleochemicals production
758
764
357
358
38
olive husk extraction
359
olive oil production
218
olive oil production
351
palm kernel oil production
276
palm oil heat bleaching
667
Index Terms
Links
Processing flow chart, acid degumming (Cont.) palm oil physical refining
702
palm oil production
212
palm oil production with presses
347
peanut butter production
793
peanut oil production
250
polysucrose ester production
46
preparation of oil seeds for extraction
362
press extraction
382
pretreatment for physical refining
797
rapeseed oil production
258
recycling of spent nickel catalyst
562
removal of foreign material from oilseeds
365
rice bran oil production
312
safflower seed oil production
286
seed oil extraction
361
semicontinuous deodorization
678
sesame seed oil production
271
shortening production
779
solvent extraction
148
solvent recovery
427
solvent recovery from extraction meal
424
solvent recovery from miscella
422
soybean oil production
228
steam iron process
567
steam reforming process
570
sunflower seed oil production
243
supercritical CO2-extraction
435
support free catalyst production
556
390
Index Terms
Links
Processing flow chart, acid degumming (Cont.) tub margarine packing
769
tung oil production
318
vegetable cream production
791
vegetable oil extraction
346
waste air cleaning
428
whale oil production
160
whole fish process (simplified)
164
whole fish process
168
winterization
509
Propylene glycol
777
Propylgallate (PG)
785
Prostaglandin Protein content, analysis
31 807
meal
807
Provitamin A
107
Puff pastry margarine
774
Pulp oils
206
Pumpkin kernel oil
313
fatty acid composition
313
PVC
765
PVC transmission
786
R Raccattattura
346
217
Randomization, see interesterification Raney nickel
559
Rape meal
257
786
Index Terms
Links
Rapeseed oil
9
251
fact file
257
258
fatty acid composition
255
258
14
17
price production process
257
properties
254
triglyceride composition
256
Rapeseed, botany
258
251
composition
179
dehulling
371
double zero
178
179
economic importance
179
252
harvest
257
255
HEAR
179
255
history
251
LEAR
179
production volume
252
yearly production
10
27
252
yield
12
13
252
Reaction rate, bleaching hardening
259
641 582
Reactivity of fatty acids
101
Recirculation
764
Recycling, catalyst
562
Redler conveyor
202
Reduction of oilseeds
373
Reesterification
616
Refining fatty acid
628
254
253
Index Terms
Links
Refining separator
638
Refining
613
Refining, comparison of processes
614
economic importance
614
environmental contaminants
704
miscella
626
physical see physical refining progress
615
Refractive index
96
Remoulade sauce
790
Rendered fats
130
Residual oil content, depending on power applied
384
depending on seed moisture
384
depending on throughput
384
extraction time
402
press extraction
379
solvent extraction
389
VPEX
384
Rice bran
305
composition
310
economic importance
310
yearly production
310
Rice bran oil
305
fact file
312
fatty acid composition
311
price
311
production process
312
triglyceride composition
311
yearly production
305
404
Index Terms
Links
Ricinoleic acid
63
Rising channels
631
Rotary brush strainer
164
Rotary drum filters
484
Rotational seed dryer
191
Running cost, oil mill
440
65
S Safflower meal
285
Safflower seed oil
282
fact file
285
fatty acid composition
284
price
286
production process
286
properties
283
triglyceride composition Safflower seed, botany
70
287
285
282
composition
283
dehulling
373
economic importance
283
harvest
285
history
282
yearly production
284
yield
284
Safinco degumming
430
Salad mayonnaise
787
Salad oil
783
284
313
Index Terms
Links
Salt
745
Saponification
102
Saponification number
803
SCD
788
678f
Scraped surface heat exchanger
757
Screw conveyor
196
Screw press
137
383
138
387
technical data Scuotitura
217
Seed oil extraction process
361
Seeds, aging
193
cleaning
363
drying
187
harvest
187
pretreatment
362
size reduction
373
storage
188
transport
196
Selectivity
550
Semicontinuous deodorizer (SCD)
678
Separation curve
460
Separation factor
487
Separation of olein and stearin
479
Separation sharpness
487
Separation, centrifuges
623
Separator
355
Separator, olive oil production
355
principal drawing
355
technical data
356
759
386
363
192
636
637
Index Terms
Links
Sesame meal
271
Sesame seed
266
Sesame seed oil
266
fact file
272
fatty acid composition
269
price
272
production process
271
properties
269
triglyceride composition
70
Sesame seed, botany
266
composition
269
economic importance
266
harvest
270
history
262
yearly production yield
10
272
270
272
268
268
Sesamol
112
113
Sesamolin
112
113
Shea butter
506
fatty acid composition triglyceride composition
313 70
Shear stress
748
Sheep milk
124
Sheep slaughtered
133
Short Mix Process
624
Shortening, plasic
779
Shortening production process
779
pumpable
779
308
Index Terms
Links
Shortenings
778
Sieving
364
Silicate degumming
430
Silicates for bleaching
647
Silos, construction
193
content ®
Simplesse
194 45
Sinoles System
356
Sitosterol
109
Size reduction, seeds
373
Skim milk souring
723
acid development
723
Slab fats
780
Slaughtered stocks
133
Slaughtering
132
Sliding cell conveyor
201
Sliding cell extractor
415
Smoke point
95
Soap splitting
617
Soap splitting, titration curves
629
Soaps
628
Sodium
525
Sodium alcoholate
525
Sodium hydroxide
525
Sodium lauryl sulfate
471
Solid fat content
807
628
after interesterification
518
beef tallow
524
526
beef tallow fractions
492
498
Index Terms
Links
Solid fat content (Cont.) butter
724
butter oil fractions
500
cocoa butter
505
cocoa butter interesterified
524
cocoa butter replacers
507
518
526
coconut oil coconut oil, hardened
564
601
corn oil
784
cottonseed oil
784
cottonseed oil, hardened
564
depending on cooling time
755
depending on fractionation technique
488
edible tallow
155
fish oil, hardened
546
564
601
hardened oils
546
564
601
hardening
546
influence of interesterification
518
interesterified blends
448
lard
151
518
526
lard fractions
495
linseed oil
784
margarine
750
native and interesterified oils
526
oils
450
olive kernel oil
784
palm kernel oil
448
palm kernel oil hardened
536
601
784
518
526
534
Index Terms
Links
Solid fat content (Cont.) palm kernel/coconut oil blend
519
526
palm oil
503
518
526
palm oil fractions
504
palm oil hardened
546
564
601
palm oil interesterifed
541
peanut oil
784
randomly and directedly interesterified oils
537
rapeseed oil
784
rapeseed oil hardened
546
578
581
585
588
564
574
575
784
601 safflower seed oil
784
soybean oil
784
soybean oil hardened
546
553
601
602
sunflower seed oil
784
sunflower seed oil hardened
564
601
Solids content, see solid fat content Solubility of gases in oil
92
Solubility of hydrogen in oil
579
Solubility of liquid CO2
433
Solubility of oil in fat
89
Solubility of oil in solvents
89
Solubility of stearins in oleins
95
Solubility of triglycerides
93
Solubility of water in oil
93
Solvent extraction
143
Solvent extraction plant for animal fats
147
434
389
Index Terms
Links
Solvent fractionation,see wet fractionation Solvent recovery
423
Solvent winterization
510
Sorbic acid
746
Sorbitol
777
Souring culture
726
Soybean meal
225
227
Soybean oil
9
223
fact file
227
229
fatty acid composition
226
229
14
15
price
18
230 production process
226
properties
225
triglyceride composition Soybeans, botany
70
228
226
223
composition
225
dehulling
368
economic importance
223
harvest
187
history
223
369
226
227
yearly production
11
27
224
yield
12
13
224
SPE
45
Specific density
80
Specific heat
74
Sperm oil, yearly production
12
Squalene
105
106
19
25
Index Terms SSHE
Links 789
SSHE, Scraped surface heat exchanger Stabilizers
747
Stack cooker
379
Starch
747
Statistical distribution of fatty acids
68
Steam iron hydrogen
566
Steam reforming process
569
Stearic acid
54
Stearyl citrate
736
Steep angle decanter
639
Steepness
60
81
Steran, structure
109
Sterilization, palm fruit
347
Sterols
106
Stick water
165
Stoke's Law
632
Stone mill
351
Storage, capacity of silos
194
moisture
188
of oil
201
of seeds
188
temperature
189
time
189
Stripping steam
380
352
203
675
697
Subsidies for fats
27
41
Sucrose polyester
45
Sulfuric acid
618
64
Index Terms
Links
Sunflower fatty acid composition during ripening
177
Sunflower meal
206
Sunflower plant density and oil yield
182
Sunflower seed oil
242
9
237
fact file
242
244
fatty acid composition
176
240
244
14
17
244
245
181
182
price production process
243
properties
239
triglyceride composition
70
241
176
237
composition
239
240
dehulling
371
economic importance
237
harvest
239
history
237
Sunflower seed, botany
yield
12 239
Supercritical gas
432
Superdegumming
431
Surface tension
744
Surface wetting agent
471
T Tallow, see beef tallow Tamman's rule
462
Tank filter
661
TBHQ
785
241
13
238
Index Terms
Links
Tea seed oil
314
Technical data, agitated autoclaves
140
cake breakers
389
candle filters
660
carousel extractors
412
clarifying decanters
356
clarifying separators
356
copra cutters
374
decanter
636
dehulling machines
368
dewaxing membranes
514
disk filters
664
drum conditioners
382
flaking mills
377
fluted breaker rolling mills
375
interesterification catalysts
525
iron separators
366
margarine processing lines
761
nickel catalyst
563
oil foots separator
387
refining separators
636
screw presses
138
separators for pulp oil separation
356
solvent extractors
413
tank filters
660
tub fillers
772
wrapping machines
767
387
Index Terms
Links
Temperature profile, SCD
680
Temperature, hardening
573
Temperature, interesterification
529
538
TFA, see trans fatty acids Theobromine
288
Thermal expansion
81
Thermal heating oil
690
Thickeners
747
Thioglucosinase
114
Threshold value, flavors
668
Timnodonic acid
63
Tirtiaux procass
469
Toaster
426
Toasting, soy meal
427
Tocol
109
Tocopherol
109
TOP degumming
431
Trace metals
710
Trans fatty acids, proportion after hardening
65
112
113
577
580
584
590
602
Transition temperature, crystal modifications
74
Transition time, ȕ´- to ȕ-modification
77
Transmission, packing material
786
Transport, oils
201
seeds
196
Triacylgylceride,see triglycerides Tricaprinate
71
74
Tricaprylate
71
74
81
586
588
Index Terms
Links
Trichloroethylene
396
Triclinic crystals
71
Tridecanone
88
Trienic acid
550
Triglyceride classes, beef tallow
524
borneo tallow cocoa butter
524
coconut oil
524
cottonseed oil
524
dependent on fractionation technique
478
lard
524
lard fractions
494
lard interesterified
540
linseed oil
280
olive oil
216
palm kernel oil
524
palm oil
447
501
palm oil fractions
447
503
peanut oil
524
rapeseed oil
524
soybean oil
524
sunflower seed oil
524
Triglycerides, distribution
66
melting point Trilaureate
540
503
524
74
81
82
74
81
82
71 71 456
Trilinoleate Trimyristinate
280 71
Index Terms Trioleate Tripalmitate
Tristearate
Links 506 71
74
456
475
71 456
Tub filling machine
771
Tuna fish liver oil
170
Tung oil
315
fatty acid composition
317
production process
318
properties
316
yearly production
81
82
74
81
82
465
506
12
Turkey-X-disease
249
Two-phase extraction
437
U UF degumming Undecanone
431 88
Unidegumming
431
Unsaponifiable matter
805
V V-Pex Press Vaccenic acid
384 62
Vacuum belt filter
481
Vacuum drum filter
484
Vacuum, deodorization
691
65
Index Terms
Links
Vapor condensation
427
Vapor condenser
693
693
Vapor pressure
86
398
670
aldehydes
88
671
696
fatty acids
87
671
696
ketones
88
671
696
miscella
398
stearic acid
671
tristearate
87
Vapor treatment
427
Vegetable cream, formulations
790
Vegetable oils, usage
9
Vegetation water, olives
359
Velocity constant bleaching
644
Vertical filter
662
Vertical seed dryer
191
Vinegar
789
Vinylamylketone
670
Virgin oil
219
Virgine
219
Viscosity
87
90
748
35
36
108
110
111
723
736
741
35
36
109
111
736
741
747
35
36
109
741
747
crystallizing melt
461
filtering fractions
487
Vitamin A
671
747 Vitamin D
Vitamin E
723
Index Terms Vitamins Volume flow, oil mills
Links 35
108
362
W Walnut oil
305
fact file
310
fatty acid composition
322
price
310
Waste air cleaning
428
Water content, determination
805
equilibrium with ambient air
189
influence on press extraction
381
Water degumming
430
Water soluble ingredients
753
Wet fractionation
415
cooling curve
476
energy requirements
475
principle
475
process
475
processing flow chart
477
Wet rendering
140
mass balance
143
operational data
145
production plant
141
Whale
158
Whale body composition
158
Whale oil
158
fatty acid composition Wheat germ oil fatty acid composition
159 313 313
144
146
Index Terms
Links
Wheat germ oil, properties
313
White fats
778
Whole Fish Process
167
Winterization
508
comparison of processes
511
continuous
509
losses
511
miscella
510
miscella processing flow chart
512
plants
510
process
509
processing flow chart
509
solvent
510
World fat production
6
World population
6
Wrapper machines (margarine)
766
Wrappers, folding
767
X Xanthan gum
777
Y Yeasts, fatty acid composition
322
oil content
321
Zenith process
622
Zoomaric acid
62
Z
168
7
768
9
