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1 Introduction to coffee
1.1 Origin and history of coffee Coffee is native to Ethiopia and introduced to India during 1600 AD. Over the centuries, numerous legends have been accumulated about the discovery of coffee. Possibly, the earliest references to the use of coffee are to be seen in the Old Testament. Coffee cultivation had begun as early as the 16th century. The most well-known story – the discovery of the coffee plant is concerned with a goatherd tending his flock in the hills around a monastery on the banks of the Red Sea. He noticed that his goats, after chewing berries from the bushes growing there, started prancing excitedly. A monk from the monastery observed this behaviour, took some of the berries, roasted them, and brewed them. When he served, the brew kept his people more alert during the long prayers at night and this shows the birth of the world’s most stimulating beverage [1]. The word coffee is derived from the Arabic word “quahweh”, which is a poetic term for “wine”. Since wine is forbidden to devout Muslims, the name was changed to coffee. The wild coffee plant is indigenous to Ethiopia, from which it is spread to Arabia and nearby countries. The transport of coffee from the countries near Arabia to other parts of the world was limited; the raw beans were not allowed out of the country without steeping in boiling water or heating to destroy their germinating power. Strangers were not allowed to visit the plantations; it was Baba Budan, a pilgrim from India, who smuggled out a few seeds capable of germination. He planted the seeds in the Western Ghats of Coorg in South India during 1600 AD. The cultivation was expanded during British rule. In Brazil, coffee entered through a Brazilian officer who, while on visit to French Guyana in 1727, received a plant hidden in a bouquet of flowers as a token of affection from the governor’s wife. This was the start of coffee plantations in Brazil, which now holds supremacy in the world.
1.2 Coffee production scenario Coffee is one of the most important agricultural products traded worldwide. It is grown and exported by over 70 developing countries 3
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in the tropical and subtropical belt and developed countries import and consume most of it. Out of these, 51 countries, including Brazil, Colombia, Guatemala, India and Mexico are responsible for more than 99% of world output and are exporting members of the international coffee agreement. The coffee production statistics are given in Tables 1.1 (2005–06) and 1.2. The export details of coffee from India are given in Tables 1.3 and 1.4. India exports maximum amount of coffee to the countries viz., Italy, Russia, Germany, Spain, Finland, Greece, etc. Table 1.1 List of coffee-producing countries
No.
Country
Type of coffee
Production (Bags in million, 1 bag =60 kg)
1
Brazil
Arabica and Robusta
35.00
2
Cameroon
Arabica and Robusta
1.00
3
Colombia
Arabica
11.0
4
Costa Rica
Arabica and Robusta
0.60
5
Cuba
Arabica
0.28
6
Dominican Republic
Arabica
0.50
7
Ecuador
Arabica and Robusta
0.70
8
El-Salvador
Arabica
1.30
9
Ethiopia
Arabica
4.50
10
Guatemala
Arabica and Robusta
3.70
11
Guinea
Arabica
4.50
12
Haiti
Arabica
0.37
13
Honduras
Arabica
3.00
14
India
Arabica and Robusta
4.60
15
Indonesia
Arabica and Robusta
6.70
16
Ivory Coast
Robusta
2.50
17
Kenya
Arabica
1.00
18
Madagascar
Arabica and Robusta
0.70
19
Mexico
Arabica
4.20
20
Nicaragua
Arabica
1.40
21
Uganda
Arabica and Robusta
2.70
22
Peru
Arabica
2.70
23
Philippines
Arabica and Robusta
0.50
24
Venezuela
Arabica
0.80
25
Vietnam
Robusta
11.00
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Introduction to coffee Table 1.2 India – Coffee area, production and productivity [2]
Season
Area (ha)
Production (MT)
Arabica Robusta
Total
Productivity (kg/ha)
Arabica Robusta Arabica Robusta
Average
2000–01
146502
167342
313934
104400
19680
713
1175
950
2001–02
149056
171681
320737
121050 179550
812
1046
937
2002–03
146780
173835
320615
102125 173150
696
996
859
2003–04
148389
176735
325124
101950 168550
687
954
832
2004–05
153280
180058
333338
103400 172100
675
956
826
2005–06
151547
189804
341351
94000
180000
620
948
803
2006–07
151861
191179
343040
99700
188300
657
985
840
2007–08
148354
193959
342313
92500
169500
624
874
765
Table 1.3 Earnings from export of coffee from India (2008) [2]
S. no.
Destination
1
Quantity
Unit value (Rs/MT)
Total value (Rs in crores)
MT
%
Italy
53804
24.57
88567
477
2
Russian Federation
25183
11.50
100657
253
3
Germany
14236
6.50
101695
145
4
Belgium
10615
4.85
94201
100
5
Spain
8802
4.02
81100
71
6
Finland
7914
3.16
92434
73
7
Greece
5470
2.50
80084
44
8
Slovenia
5400
2.47
77728
42
9
Croatia
5011
2.29
83261
42
10
Ukraine
4916
2.25
106524
52
11
Others
77588
35.89
104503
811
Total
218939
100
93741
2110
Table 1.4 Export of speciality and value-added coffee from India*
Grade
2000
2001
2002
2003
2004
2005
2006
2007
2008
Speciality coffee Mysore Nuggets 710 AB Monsoon Malabar 1156 AA
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465
760
1037
998
828
1207
1088
838
1204
1827
1832
2528
2180
2462
3425
1516
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6 Monsoon Robusta AA Monsoon Arabica TR Monsoon Robusta TR Monsoon Malabar Basanally Robusta Tapi Royale
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861
669
822
824
18
13
13
12
1119
1205
1601
1082
529
9
72
27
8
60
15
3 27
Total
50
52
145
152
289
227
415
411
2541
3059
3957
4160
4259
3828
3809
2680
49522
6540
7807
8947
8769
9457
9860
5981
Value-added coffee Instant
41820
43233
44978
43691
53916
54315
54830
64830
29511
Ground
7
18
17
50
111
51
98
316
57
Roasted seed
147
36
0.4
27
41
20
83
54
51
Total
41974
43287
44995
43767
54068
54386
55012
65246
29619
*quantity in MT [2]
1.3 Botany, agricultural practices and propagation The coffee plant belongs to Rubiaceae family (Table 1.5), which has over 70 species of coffee. But only seven of them have significant economic importance. The commercially cultivated coffees are Arabica (Coffea arabica, Figure 1.1) and Robusta (Coffea canephora, Figure 1.2). Coffea libera, another species, was devastated during the 1940s by an epidemic of trachemycosis due to infection by Fusarium xylaroides and the commercial growth of this species has effectively ceased since then. C. roubusta is noted for resistance to disease and contains more caffeine than C. arabica, and is thus more economical in the manufacture of instant coffee [3].
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Figure 1.1 Coffee arabica
Figure 1.2 Coffee Robusta Table 1.5 Systematic taxonomical position of coffee
Division
Angiosperm
Class
Dicotyledonous
Family
Rubiaceae
Genus
Coffea
Species
Arabica, Robusta, etc.
The coffee plant is a small tree and can grow up to 25 ft (7.6 m) in the wild state. C. arabica and C. Robusta are maintained at 5 ft (150 cm) and 5.5–6.0 ft (170–185 cm), respectively. These trees are pruned for two reasons – to facilitate harvesting and maintain optimum tree shape. The primary branches are opposed and horizontally drooping, and the leaves grow in pair on short stalks. They are about 15 cm of length in C. arabica and longer in C. canephora – oval and fairly dark green in colour. Various methods of propagation are being used, including cuttings, grafting and layering. The use of cuttings is the normal commercial practice. The coffee plants start yielding fruits within 3–5 years and last up to 30–40 years. An altitude of 2000–4000 ft (600–1200 m) is ideal for coffee, but it can be grown at
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6000 ft (1800 m). The higher the altitude, the better is the quality of coffee. The limiting factor is that coffee cannot withstand frost. The ideal climatic condition of coffee is 30–40°C and rainfall 60–80 in. (150–200 cm). The yield of coffee is totally dependent on the flowers produced by the plants and more importantly, on the percentage of fruit set from flowers. The blossoming largely depends on timely rainfall, which induces the flower bud to open within 7–10 days. In recent years, sprinkler spraying is widely used for opening flower buds. Insects carry out pollination of flower. The normal development from flower to fruit requires 5–8 months in C. arabica and 9–10 months in C. Robusta. The fruits are borne in clusters at each leaf axil. In the case of C. arabica, each cluster carries 15–20 fruits per node whereas there are 40–80 fruits in C. Robusta. The berry (Figure 1.3) consists of an outer skin, over a fleshy pulp, in which two seeds are embedded. Seeds are flat on one side and convex on the other side. Occasionally, one seed rounded on both sides (peaberry) may be found. The seed is covered by a thin silver skin as well as by a thick layer called parchment [1]. Red berry skin (epicarp) Pulp mesocarp Mucilage Parchement (endocarp) Silver skin (spermoderm) Endosperm
Figure 1.3 Coffee berry – cross-section
1.4 Processing 1.4.1 Green bean processing The processing of green coffee is carried out by two methods namely, wet method and dry method (Figure 1.4). In the wet method (Figure 1.5), only ripe fruits having a reddish brown colour are picked, graded and fed to a pulper to remove the outer skin and mucilage. The parchment (Figure 1.6) is washed thoroughly and dried. The coffee prepared by this method is called parchment coffee, and is practiced in Columbia, Kenya and most of the South and Central American Countries. India also processes arabica coffee by this method. In
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the dry method (Figure 1.7), ripe, green and under-ripe fruits are sorted out and then dried separately. The coffee obtained by this method is called cherry coffee. Consumers favour parchment coffee from the wet method [4]. Fresh cherries Wet processing
Dry processing
Biochemical Mechanical
Mucilage removal
Drying
Chemical Washing
Hulling
Drying
Sorting and grading
Polishing
Packing
Sorting and grading
Shipping
Packing Shipping Figure 1.4 Cofee processing - wet and dry methods
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Figure 1.5 Wet processing
Figure 1.6 Parchment coffee
Figure 1.7 Dry processing
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Introduction to coffee
11
1.4.2 Roasting of coffee Roasting is the first step in the preparation of any consumable product from green coffee. The characteristic aroma is developed during roasting. Coffee received at the roasting plant should be free of extraneous matter, but in practice, it is usually contaminated with chaff, strings, wood splinters, stones, pebbles, coins, nails etc., and therefore these must be cleaned well. Large particles are removed using screens and light particles are blown off through air blasting. Nails and other materials are removed using magnetic separators.
Roasting process Roasting of coffee is a process of exposing the coffee beans to a warming process that is sufficient to drive off the free and bound moisture; dry beans are heated to a temperature of 200–250°C. The time required for roasting is 5–10 min in a continuous roaster and more than 20 min in non-continuous roaster [4]. The degree of roasting is critical for the development of flavour in the bean and determines many of the flavour characteristics of the brewed coffee. The relationships between different roasting temperatures, weight loss and cup quality are summarized in Table 1.6. The degree of roast is usually assessed from external colour, a final quantitative assessment made using colour reflectance meters [5, 6]. The conventional roasting equipment consists of a metal container in which green coffee is heated while it is continuously rotated (Figure 1.8). Heat may be supplied by conduction from hot air or more frequently by a mixture of both the methods of heat transfer together. It is necessary that during the roasting process, heat may be supplied quickly, uniformly and the beans are continuously stirred.
Figure 1.8 Coffee roaster
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Table 1.6 Roasting parameters and cup quality
Temperature (°C)
Roast
Weight loss %
Cup quality
180–200
Very light
10–12
Acidic taste, poor aroma
200–220
Light
12–15
Better aroma, acidic cup
220–230
Medium
15–20
Best aroma, optimal quality,
230–240
Dark
20–23
Dark colour, (aroma preferred by Europe)
240–250
Very dark
23–25
Very dark colour, (good taste for Italians)
Different types of roasters are available. Continuous roasters are used in large scale processing plants because these have greater efficiency, and ensure better uniformity than batch-type roasters. Continuous roasters consist of either a perforated drum or a cylinder for roasting and subsequent cooling of the beans. The rotating drum principle is used in the commercial roasters. Fluidised bed roasters are used for large scale roasting of the coffee beans. Both heating and cooling are achieved in the same vessel by a fluidised solid contact technique. Fluidised roasters have better control parameters and deliver the product with uniform roasting. The spouted bed roaster is a variant of the fluidised bed roaster that has an advantage in large scale roasting and tends to develop unstable fluidisation [7, 8, 9 ]. The special feature of the spouted bed roaster is that it has no moving parts or vibratory units, which may damage the final product. The roasting chamber is transparent so that the colour of the roasting beans can be easily controlled visually [10].
Changes during roasting Many types of physical and chemical changes occur during roasting, including changes in colour, size and shape of the bean. The important changes that take place during roasting are loss of moisture, loss of organic matter and production of CO2; swelling of bean and consequent changes in density of the bean; decrease in the breaking strength of the bean, caramelisation of sugar and other constituents, with consequent changes in colour and formation of typical aroma compounds; decrease in the tannin like constituents and sugars increase in water soluble matter and formation of niacin, and increase in its content during roasting. The chemical composition of green, roasted and brewed solids is presented in Fig.1.9 [11]. Roasting results in loss of weight of the bean. Roasting produces a large amount of CO2 inside the bean, which under high pressure bloats the bean
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Introduction to coffee
with the corresponding reduction in the specific gravity from 1.2–1.3 to 0.6–0.8. This results in porous structure and reduction in the breaking strength of the roasted bean. The colour of the bean changes from grey green to light brown, dark brown or almost black depending on the type of roast. The pH of the roasted coffee brew falls down to 5.5–5.0 from the pH of 6.0 of green beans. This is mainly due to the formation of organic acids (Figure 1.10). In general, light roasts give more acid cup than dark roasts. The pH of brew cup from medium roast is 5.0, while that of dark roast is up to 5.3. Roasted coffee beans
Green coffee beans starches and pectins 13%
starches and pectins 14%
cellulose (Hyd) 13%
soluble carbohydrates 9%
non volatile acids 7%
trigonelline 1%
non volatile acids 7% caffeine 1%
protein 12%
ash 3%
cellulose (Hyd) 15%
soluble carbohydrate 10%
cellulose (non Hyd) 18%
water 12%
CO2 2%
cellulose (non Hyd) 18%
water 2%
trigonelline 1%
caffeine 1%
oil 11%
protein 13%
ash 4%
oil 13%
Brewed solids non volatile acids 33%
soluble carbohydrates 38%
caffeine 5% ash 17%
oil 1%
protein 6%
Figure 1.9 Chemical composition of green, roasted and brewed solids
Sugars and proteins break down to aldehydes, alcohols and acids. Sucrose is the major sugar, which suffers heavy loss during roasting. Proteins are denatured and are broken down to amino acids. The most significant change occurring during roasting is the formation of aroma compounds. Roasted whole beans retain the characteristic aroma for about a week under normal atmospheric condition. This is mainly due to the carbon dioxide built-up inside the bean providing an inert atmosphere. The volatile compounds of coffee are largely responsible for the aroma. The green bean does not possess any appealing flavour and its infusion is
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unpalatable. Roasted coffee contains more than 1000 volatile compounds [12]. The chemical composition of green and roasted coffee, and the important precursors for the formation of volatiles are given in Tables 1.7–1.9 [13]. O
O CH
CH
OH
O
C
CH
CH
COOH
C
HO OH
OH
O
HO
HO
HO
COOH
Quinic acid
Caffeic acid
Caffeoylquinic acid
OH
HO
+
OH
OH
H
O CH
CH
C
OH CH
+
Degradation rapid OH
HO
HO
OH HO
OH
OH
HO
Catechol
Free caffeic acid
OH
HO
4- vinylcatechol
O
+
+
Degradation slow
HO HO
COOH
Quinic acid
CH 2
O
OH Pyrogallol
Catechol
Hydroquinone
OH
HO OH
+ HO COOH
HO HO Gallic acid
Figure 1.10 Formation of organic acids during roasting Table 1.7 Chemical composition of green coffee
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Constituent
Arabica (%)
Robusta (%)
Caffeine
0.9–1.2
1.6–2.5
Trigonelline
1.0–1.2
0.7–1.0
Ash
3.0–4.2
4.0–4.4
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5.5–8.0
7.0–10.0
Organic acids
1.5–2.0
1.5–2.0
Sucrose
6.0–8.0
5.0–7.0
Reducing sugars
0.1–1.0
0.4–1.0
Total polysaccharides
44.0–55.0
37.0–47.0
Lignin
2.0–3.0
2.0–3.0
Protein
11.0–13.0
11.0–13.0
Lipids
14.0–16.0
9.0–13.0
Table 1.8 Chemical composition of roasted coffee
Constituent
Arabica (%)
Robusta (%)
Caffeine
1.0–1.3
1.7–2.4
Trigonelline
0.5–1.0
0.3–0.7
Ash
3.0–4.5
4.0–6.0
Chlorogenic acids
2.2–4.5
3.8–4.6
Organic acids
1.0–2.4
1.0–2.6
Sucrose
Nil
Nil
Reducing sugars
0.2–0.3
0.2–0.3
Polysaccharides
24.0–39.0
25.0–37.0
Protein
~ 12
~ 12
Lipids
~ 13
~ 10
Water solubles
26.0–30.0
28.0–32.0
Table 1.9 Generation of coffee volatiles during roasting
Green coffee Lipids Fatty acid
Roast coffee Aliphatic hydrocarbons
Higher terpenoids
Monoterpenoids
Lignin
Phenolic compounds
Starch Sugars
Acids and aldehydes, Ketones
Peptides , amino acids
Nitrogenous and sulfurous compounds
Trigonelline
Nitrogenous compounds
1.4.3 Subsequent operations After developing the coffee flavour by roasting, efficient extraction of the roasted coffee solubles and volatiles that contribute to the coffee flavour and aroma is essential. The solubles could be extracted from the whole roasted
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beans, but the yield would be low and flavour would be poor. Extraction may be made to give a higher yield of solubles by breaking down the whole bean to smaller pieces. Grinding is essential to obtain maximum extraction of solubles including aroma and flavour. Various types of grinders based on the principles of cutting, shearing and crushing are available for the purpose of size reduction during large scale grinding of coffee beans. After grinding, the coffee is suitably packed and stored [14].
1.5 Chemical composition The chemical composition of green coffee depends mainly on the variety of coffee, agricultural practices, processing and storage conditions. Green coffee is especially characterized by its content of caffeine, trigonelline and chlorogenic acids, otherwise its composition is similar to other vegetable substances with their protein, carbohydrates, vegetable oil and mineral content. However, the carbohydrate portion consists mainly of polysaccharides, and the physical hardness of the same is due to mannan (low-degree polymerization). The two main species of coffee, viz., arabica and Robusta differ in composition (Table 1.7) with respect to parameters such as caffeine, chlorogenic acid, and lipids.
1.5.1 Moisture Moisture affects the quality and storage of coffee. It is generally recognized that green coffee should not be allowed to reach moisture content in excess of 12% corresponding to a relative humidity of 70%. Higher moisture content will result in loss of green colour, favour mould growth, flavour deterioration and possibility of mould toxin formation [15]. Deterioration is also markedly accelerated by temperature (low temperature is preferred for retaining the colour and flavour quality). Moisture content of 10.5% for plantation coffee and 11% for cherry coffee is generally recommended. The moisture content in green, roast and instant coffees is determined by air oven, vacuum oven or Karl Fischer method. Moisture meters are now available for quick measurement of moisture content in green coffee. The most commonly used Kappa moisture meter works on the principle of dielectric constant. The instrument needs calibration using a reference method, i.e. oven method [16].
1.5.2 Caffeine This is perhaps the most important chemical component studied in coffee due to its reported physiological effects. Caffeine (Figure 1.11), 1,3,7trimethylxanthine, is an alkaloid with a substituted purine ring system. The
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Introduction to coffee
main physiological effect of caffeine appears to be as a stimulant to the central nervous system. It has an effect on the cardiovascular system with slight increase in blood pressure and heart output. Caffeine also increases the gastric acid secretion. It undergoes bio transformation in the human body to form methylated derivatives of uric acid. Caffeine is definitely not lethal to the system when ingested in the form of beverages, unless one consumes 75 cups of coffee, 125 cups of tea or 200 cola beverages within 30 minutes [17]. O H3C O
N
N N
CH 3
N
CH 3 Figure 1.11 1,3,7- trimethylxanthine
The caffeine content of green coffee bean varies according to the species; Robusta coffee contains about 2.2%, arabica about 1.20% and the hybrid ‚arabusta‘ about 1.72%. Environmental and agricultural factors appear to have minimal effect on the caffeine content. During roasting, there is no significant loss in terms of caffeine. A typical cup of regular coffee contains 70–140 mg of caffeine depending on preparation, blend and cup size [15]. The structure of caffeine is that of purine derivative xanthine, with methyl substituents attached at positions 1, 3 and 7. Reports on the bio-synthesis and degradation of caffeine in coffee are limited. Both processes occur more rapidly in immature than mature fruit. The main biosynthesis route utilises the purine nucleotide for the formation of caffeine is well documented [18]. In coffee plants caffeine is synthesised from xanthosine via 7-methylanthosine, 7-methylxanthine and theobromine. S-adenosylmethionine (SAM) is the actual source of the methyl groups. The caffeine is degraded relatively slowly and involving demethylation steps to yield theobromine and theophylline. Theophylline is catabolised to xanthine via 3-methylxanthine. But it is unclear whether 3-methylxanthine and/or 7-methylxanthine are intermediates in the conversion of theobromine to xanthine. Xanthine is metabolised to urea [18]. On roasting, caffeine is unchanged though some loss occurs due to sublimation. Caffeine is the most important compound in the analytical parameters of coffee and in the standards and specifications of coffee and
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coffee products. There are several analytical procedures for the determination of caffeine in coffee such as Baily Andrew, Levin’s and HPLC methods [13].
1.5.3 Organic acids Chlorogenic acid is one of the important components along with the other organic acids (Figure1.12) present in green and roasted coffee beans. Chlorogenic acids contribute to acidic and astringent tastes. Chlorogenic acid comprises of caffeoylquinic acid ester of caffeic and quinic acids, deiaffeoylquinic acid, feruloylquinic acid, coumaroylquinic acid, caffeoylferuloylquinc acid and feruloylcaffeoylquinic acid. These isomers suffer heavy losses during roasting and the degree of loss depends on the type of roasting. Robusta coffee contains high amounts of chlorogenic acid compared to arabica coffee. High astringency of Robusta coffee is attributed to dicaffeoylquinic acids and the feruloylquinic acids. Further, the higher content of 4, 5-dicaffeoylquinic acid in Robusta appears to contribute to a peculiar lingering metallic taste, which is a negative sensory effect [19]. Chlorogenic acid is determined by spectrometric and chromatographic methods, which allow separation and quantification of individual isomers. During roasting, polysaccharides undergo degradation resulting in several organic acids which contribute to the acidity of coffee brew, and this is an important sensory quality. The acids reported are citric, malic, lactic, quinic, pyruvic, acetic, oxalic, tartaric, propionic, butyric, valeric, etc.
1.5.4 Trigonelline and nicotinic acid Trigonelline (Figure 1.13) present in green coffee (about 1%) degrades rapidly on roasting, yielding nicotinic acid, nicotinamide and a range of aroma volatiles, which includes pyridines and pyrroles. Roast coffee contains 10–40 mg of nicotinic acid per 100 g depending on the degree of roasting [16].
1.5.5 Proteins Proteins and amino acids have received relatively little attention. Considerable research [16] has been carried out to correlate the initial protein content in green coffee to the aroma and taste of the coffee brew obtained from the roasted and ground powder, but with limited success. In green coffee, proteins exist in unbound form predominantly in the cytoplasm or are bound to cell wall polysaccharides. Proteins are denatured during roasting and broken down to amino acids. The sulphur amino acids like cystein, cysteine and methionine degrade alone or react with maillard intermediates. Hydroxyl amino acids like
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serine and threonine react with sugars during roasting to yield pyrazine and their derivates, and pyridines and their derivatives. Free amino acids occur only in traces in roasted coffee [20]. O CH
CH
C
OH
OH HO HO
HO
OH
C OH
O HO
Quinic acid
Caffeic acid
O CH
CH
C
O OH
CH
CH
C
OH
OH
HO o-coumaric acid
p-coumaric acid
O CH
CH
C
O OH
CH
CH
C
OH
O
C O
HO OCH 3 HO Ferulic acid
HO
OH
HO HO
Chlorogenic acid
Figure 1.12 Organic acids present in coffee
1.5.6 Carbohydrates Green coffee contains sucrose and a wide range of pol3ysaccharides (arabinogalactan, galactomannan and cellulose). Sucrose is the major sugar which suffers heavy loss during roasting due to caramelisation and other reactions. Because of the severe conditions employed for extraction in instant coffee manufacture, hydrolysis of insoluble polysaccharides takes
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place yielding soluble oligosaccharides mainly, polymers of mannose and galactose, arabinose and mannose monomers [21]. The sugar analysis involves determination of free sugar in green coffee, oligosaccharides in instant coffee and monosaccharides (after hydrolysis of polysaccharides) in all coffee products. O C
O
COOH
+ N
N
CH3
Trigonelline
Nicotinic acid
Figure 1.13 Trigonelline and nicotinic acid
1.5.7 Melanoidins Proteins and carbohydrates react during roasting, forming melanoidins. Melanoidins are derived from Maillard reactions or from carbohydrate caramelization. The melanoidins are the caramelized substances consisting of complicated structures involving fragments of phenols, carbocycles, N-hetero-cycles, benzenoids and furanoids. Attempts to isolate browning substance in roasted coffee have remained unsuccessful. Melanoidins appear to have a stimulating effect on the stomach intestinal tract causing irritation in some persons. This irritation is reported to reduce substantially by treating the coffee beans with steam prior to roasting [22].
1.5.8 Minerals The ash content of green coffee is about 4% (dry matter basis) of which 40% is potassium (dry ashing at 580C and estimation by flame photometry or atomic absorption spectrometery). In addition to potassium, 30 more elements were quantified in coffee products by atomic absorption or neutron activation analysis and these include magnesium, calcium, rubidium and iron. Manganese content is higher in arabica (25–60 ppm) and lower in Robusta coffees (10– 33 ppm). The other trace elements reported in green coffee include zinc, molybdenum, cobalt, copper, strontium and others. There can be considerable contribution of trace elements to the instant coffee from the processing water and this varies with the source of water employed [23].
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1.5.9 Lipids Lipids constitute one of the major components of green coffee (arabica 14–16% and Robusta 9–13%). Coffee beans are coated with a polar wax (0.2–0.3%), which consists largely of fatty acid esters of 5-hydroxytryptamine, which are known to act as mucosal irritants [12]. The lipids content in boiled coffee, espresso and filter coffee are reported as 2.2%, 0.4% and 0.2% respectively on ground coffee basis. Instant coffee contains very little lipid materials, apart from coffee oil that may be added for aromatization at the end of the process.
1.5.10 Volatile compounds The green coffee is devoid of any appealing taste or aroma. The pleasant flavour of coffee is formed during roasting involving a wide range of complex chemical reactions like oxidation, reduction, hydrolysis, polymerization and decarboxylation. Roasting alters the colour, size and shape of the bean. The degree of roast is based on flavour preference, which varies from place to place. The most important change occurring in coffee during roasting is the formation of aroma compounds. The important aroma precursors are amino acids, sugars and chlorogenic acids. Some minor compounds are formed from other compounds such as terpenes, trigonelline, sterols and lipids. The most significant reaction in coffee aroma formation is interaction between amino acids and reducing sugars (browning reaction), and also the direct caramelisation [24, 25, 5]. The study of flavour compounds includes total volatiles analysis including headspace compounds. Recently, there has been a remarkable progress in the isolation and recovery of the flavour volatiles. Initially, the flavour analysis met with several problems such as (a) the number of volatile substances was extremely large, (b) the compounds varied in physical and chemical properties and in the levels of concentration and (c) isolation and identification procedures could alter the nature of several sensitive compounds resulting in artefacts. In spite of these inherent difficulties, the flavour chemistry of coffee has received maximum attention world over and about 800 flavour components have so far been identified though relatively small number of compounds make a significant contribution to overall flavour. Volatile compounds are being considered desirable at low concentrations while undesirable at higher concentrations. Studies on flavour formation also have received some attention in recent years. The origin of various volatiles [5, 26] in roast coffee is correlated to aroma precursors such as amino acids, proteins and sugars (Table 1.10). The complete mechanism of flavour formation in coffee from the precursors is not well understood. The search for key flavour compounds responsible for the characteristic aroma of coffee has not yielded good results. However, some of the important
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aroma compounds and their contribution to overall flavour are presented in Table 1. 11 [27, 28, 29]. Table 1.10 Formation of aroma volatiles in coffee
Type of volatile compound
Possible precursor
Mechanism of formation
Saturated hydrocarbons, dicarboxylic amino acids Glucose, aromatic amino acids Sugars, fatty acids, amino acids
Pyrolysis, oxidative, decarboxylation
Alcohols
Carbonyl compounds
Reduction
Olefinic hydrocarbons Aromatic hydrocarbons Carbonyl compounds
Pyrolysis Pyrolysis
Phenols
Tannins, chlorogenic acid
Pyrolytic degradation
Mercaptans, sulphides, thiophenes
Sulphur amino acids
Pyrolysis
Thiazoles
Cysteine
Pyrolysis
Furan compounds
Carbohydrates
Cyclisation
Pyrazines
Carbohydrates – Amino acid/ ammonia
-
Pyrroles
Prolines
-
Pyridines
Trigonelline
-
Table 1.11 Possible aroma impact compounds
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Aroma compound
Flavour effect
Furyl-2-methanethiol
Fresh coffee aroma (10–500 mg/kg/) Stale note (1–10 mg/kg)
Kahweofuran
Slight coffee note (10–100 mg/kg)
n-furyl-2-methylpyrrole
Stale coffee odour
2-ethyl furan
Burnt, sweet, coffee-like aroma
n-ethyl-2-formyl pyrrole
Burnt, roast coffee
Thiobutyrolactone
Burnt coffee odour
2-methyl-2-acetyl thiophene
Coffee-like aroma
2-methyl isoborneol
Earthy, musty
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1.5.11 Amines Amines are organic bases formed during metabolic processes in all living organisms, thus present in most food products. The predominant amines in green coffee were serotonin and putrescine, followed by spermidine and spermine [30]. Total amine levels in green coffee ranged from 3.03 mg to 4.44 mg per 100 g. During roasting, there was a total loss of putrescine and spermine but less loss of spermidine and serotonin.
1.5.12 Foreign compounds At every stage of processing of coffee beans, there may be deliberate or accidental introduction of some foreign compounds. Additives and contaminants found in some coffee samples are discussed below.
Mycotoxins Fungal attack following coffee borer beetle damage, leads to the formation of viridic acid. The viridic acid test (a colour reaction) has been used to estimate the extent of pre-harvest damage by the coffee borer beetle. Fungal damage to coffee beans can also occur during fermentation processes used to separate the coffee bean from the coffee berry pulp. However, green coffee beans are highly susceptible to fungal attack if they are stored in warm humid conditions. Ochratoxin A can be produced in green coffee beans stored in warm humid conditions, due to Aspergillus ochraceous growth. Improperly stored coffee was found to contain aflatoxin. It is very interesting to note that decaffeinated green coffee beans are much more susceptible to fungal attack, than untreated green coffee. Caffeine has an antifungal effect at or above 2 mg/g. In addition, decaffeinated beans have lost their protective surface wax covering. Roasting does reduce the levels of several mycotoxins, if these are present in green coffee beans. For example, ochratoxin A is reduced by 80–90% on roasting the contaminated coffee beans. Ochratoxin A in coffee beans is estimated by solid-phase micro extraction and liquid chromatography with fluorescence detection [31].
1.6 Additives in coffee Many types of additives or substitutes are used in coffee in order to increase the brew strength. Cyclodextrins used as an additive couples with undesirable taste components and imparts smoothness to the flavour of the beverage. Cyclodextrins are heat stable and addition of cyclodextrin in the concentrated extract does not alter the characteristics of coffee [32]. Chelating agents
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like phytic acid and its alkali metal salts are used to prevent foam and scum formation in the reconstituted instant coffee beverage. Substitutes like chicory, barley, malt and rye are used to increase the brew strength.
1.6.1 Chicory: the adjunct and the extender Chicory is a permitted additive to coffee powder and very safe to the human system. Chicory (Cichorium intybus Linn.) is a tuberous plant of which the root is used for coffee adjunct. The cut pieces of these roots are dried, roasted and ground for mixing with coffee powder. It is cultivated in Gujarat (Jamanagar, Mehsana and Kaira) and Tamil Nadu (Coimbatore and Nilgiris). As per the Indian standard (IS 3802:1992) the coffee content in the coffee-chicory blend shall not be less than 51%. As per the Prevention of Food Adultration Act (PFA), the maximum percentage level of chicory that could be mixed with the roasted and ground coffee is governed by the following two requirements:
(i) C affeine content of the coffee-chicory mixture shall not be less than 0.6%, and (ii) The aqueous extract shall not be more than 50% [33].
The Bureau of Indian Standards in collaboration with the Coffee Board of India and CFTRI screened various commercial samples of chicory (Cichorium intybus) powder for chemical composition. All samples conformed to ISI specifications in respect of contents of total ash (3.5–8.0%), acid insoluble ash (max. 1.5%) and water-soluble matter (60% min.). Moisture content of 2 samples marginally exceeded the prescribed limit of 10% [34].
1.7 Tasting of coffee Coffee products are evaluated by trained and experienced tasters who have an extensive vocabulary to describe desirable and undesirable attributes of the beverages such as sweet, salty, acidic, sour, bitter, balanced, flat, stale, rancid, astringent, metallic, burnt, etc. Often flavours are described by several less well-defined terms such as brisky, cereal, chemical, earthy, grassy, green, onion, oxidized, peppery, unclean, wood, etc. Some of the important terms are discussed in the following sections [26].
1.7.1 Acidity and sourness Acidity is a desirable attribute where as sourness is undesirable, although the layman considers it synonymous. The sourness is associated with a mixture of acids, alcohols, and esters produced by microbial fermentation. Acidity is associated with protons. Wet processed, high grown C. arabica produces the
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most acid beverage; dry processed C. Robusta – the least, and dry processed C. arabica – intermediate, for a given roast and colour. Acidity is considered an important characteristic of medium roast. High acidity provides better colour and intense aroma to the beverage. It is generally agreed that pH 4.9–5.2 is the ideal range for beverage. Under ideal roasting conditions, roasted C. arabica yields a brew of the beverage in the pH range and C. Robusta yields a less acid brew of pH 5.0–5.8 [26].
1.7.2 Bitterness An element of bitterness is desirable in coffee. Bitterness has been attributed to caffeine, but even decaffeinated have been found to possess profound bitterness. It appears that other heterocyclic compounds contribute to bitterness [26].
1.7.3 Astringency Astringency is not a primary taste. Many astringent molecules are bitter, and these sensations may be confused; these are distinguished by expert tasters. Caffeoyl quinic acids, dicaffeoyl quinic acid and caffeic acid are the likely astringent components of the coffee [26].
1.7.4 Staling Staling refers to the deterioration of taste and odour on storage of coffee powder. The roasted and ground coffee preserves aroma up to 6 months under inert conditions and low temperatures. The entrapped carbon dioxide is instrumental in achieving this storage life. During storage, many volatiles decline in concentration as a result of volatility. Similarly, many new compounds are formed as a result of oxidation and other interactions [26].
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2 Health benefits
2.1 Introduction Coffee is a complex chemical mixture composed of several chemicals. It is responsible for a number of bioactivities and a number of compounds accounting for these effects. Few of the significant bioactivities documented are antioxidant activity, anticarcinogenic activity, antimutagenic activity etc. Various compounds responsible for the chemoprotective effects of coffee are mainly polyphenols, including chlorogenic acids and their degradation products. Others include caffeine, kahweol, cafestol, and other phenolics. Coffee also shows adverse effects on various systems like the skeletal (bone) system, the reproductive system, the nervous system, the cardiovascular system, the homocysteine levels, the cholesterol levels, etc. Harmful effects of coffee are associated with people who are sensitive to stimulants.
2.2 Antioxidant activity The antioxidant activity of coffee brews, using different methods of preparation was studied by Sanchez-gonaza. I, et al [35]. They observed that the antioxidant activity of coffee brews increased significantly when the brews were kept hot (80°C). The cause of this increase may be the formation of Maillard reaction in products during the heat process. These antioxidant properties are due to scavenging action of molecule for the free radical (Figure 2.1). The common antioxidant compounds in coffee are caffeine, chlorogenic acids etc. Higher antioxidant capacity was observed in Colombian conventional roasted coffee blends due to the presence of more Robusta coffee beans that contained more chlorogenic acids [36].
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Figure 2.1 Mechanism of scavenging of free radicals by caffeine
2.3 Anticarcinogenic activity Cavin.C, et al [37] studied the anticacinogenic properties coffee. The anticarcinogenic properties due to Cafestol, Kahweol, Caffeine and polyphenols including chlorogenic acids, and their degradation products were considered potentially responsible for the chemo-protective effects of coffee [38]. The chemo-preventive function of coffee for the anticacinogenic properties is mediated by the induction of transcription factor Nrf2. This factor is due to the coffee specific diterpenes cafestol and kahweol [39].
2.4 Central Nervous System (CNS) Coffee is an enjoyable beverage containing the alkaloid caffeine with psychotropic effects. A usual cup of coffee contains about 100 mg of caffeine. Caffeine is a strong stimulating agent of the brain cortex, respiratory and circulatory centres. Higher doses of caffeine (Single dose of 1000–1500 mg) may lead to symptoms such as trembling, anxiety, loss of mental concentration, tachycardia and sleep disorder. Coffee was known to increase alertness as seen with the central nervous system (CNS), improve performance on vigilance tasks and reduce fatigue [40]. It was known to provide a potential preventive influence of caffeine on suicide and depression. A dose dependent study showed that people consuming more than six cups of coffee/day showed a 5 fold lower risk of suicide than non-consumers [41]. Earlier, it was believed that the action of caffeine was related to the inhibition of phosphodiesterase, leading to increased concentrations of cyclic AMP. However, for the inhibition much higher doses of caffeine is required [42].
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2.5 Reproductive system Several reports attempted to determine whether women who consume caffeinecontaining beverages had any adverse effect in their reproductive system or during the developmental stage of the foetus. The results of the studies were conflicting. Since caffeine was shown to be teratogenic in animal models, safety concerns were raised regarding coffee drinking during pregnancy [43]. It is well documented that caffeine metabolism is slower in pregnant women, resulting in longer and possibly higher exposures.
2.6 Bone system The effect of coffee on bone health and calcium metabolism was studied [44]. The potential role of caffeine, mainly through coffee consumption, as a contributing factor of bone loss in humans has received a lot of attention. In recent years, numerous studies have reported a possible risk of osteoporosis on caffeine consumption.
2.7 Cardiovascular system The possible effects of coffee on cardiovascular risk factors are hypertension, elevated blood cholesterol, and, more recently, increased homocysteine levels. In a case control study, neither caffeinated nor decaffeinated coffee was associated with the risk of myocardial infarction, even for those drinking more than four cups a day [45]. There is no clear cut evidence showing any correlation between coffee consumption and myocardial infarction for moderate coffee drinkers, but the risk at the same time cannot be ruled out for high coffee consumers. Caffeine is the most widely used pharmacologic substance in the world, which is found in coffee. The effects of caffeine on cardiovascular diseases, including hypertension, remain controversial, and there is little information on its direct effect on vascular function. It is found that acute administration of caffeine augments endothelium-dependent vasodilation, in healthy young men, through an increase in nitric oxide production.
2.8 Antidiabetes effect for type-2 diabetes The diabetes type-2 is known to be caused by 11 β-hydroxysteroid dehydrogenase type-1 (11b-HSD1) activity. Epidemiological studies demonstrated a beneficial effect of coffee consumption for the prevention of type- 2 diabetes. The coffee extract corresponding to an Italian Espresso,
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inhibits recombinant and endogenous 11b-hydroxysteroid dehydrogenase type-1 (11b-HSD1) activity. Thus, coffee has the antidiabetes effect for type-2 diabetes [46].
2.9 Antimicrobial effect Antimicrobial effect may be due to the mutagenic effect of coffee on the microbes [47]. Roasted coffee was shown to possess antibacterial activity against both gram-positive and gram-negative bacteria, including Streptococcus mutans, which is considered to be a causative agent for dental caries in humans.
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3 Recent trends in value addition
3.1 Introduction Value addition is a process of development of the product from the raw materials so that the resulted product is totally different from the raw materials. The product may be new to market or an improvement of the existing one by changing ingredients (fortification enrichment) or by processing technologies. A new product is one that is unique and puts the company into a new business area, usually, as a result of new technology, innovation or consumer demand. Over the years various value-added products of coffee have been invented. Some of the value-added coffee products have been developed in order to target market segments. For this purpose various new products of coffee have been developed by different innovative ways of processing in order to explore the beneficial properties of the specific chemical components of coffee, and by mixing of compatible ingredients keeping the coffee as a base material. This has been possible due to constant research by the scientist and technologists. Because of this coffee beverage becoming the more popular than ever. The various value-added products have been described below.
3.2 Coffee beverage Beverages are defined as the liquid with some nutritional factor. In coffee beverage, water acts as a liquid medium and coffee solids function as a matrix. During the brewing process coffee solids are extracted into the liquid system. The extraction takes place by means of leaching from coffee roasted and ground powder. The various methods of preparation of coffee beverages are decoction, infusion and pressure methods [48].
3.2.1 Boiled coffee The coffee soluble solid is kept in contact with given amount of water at appropriate temperature for a considerable time period. The extraction takes place by the law of mass action. Higher temperature favours the higher extraction yield and rate.
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Prolonged extraction may cause unfavourable flavour and taste. This is due to the loss of volatiles and hydrolytic changes. Taste of the coffee is much better, if the boiled water is added to the ground coffee. The coarse- ground coffee is put in the water in a pot or jug and allowed to warm up to the boiling point, and then brew is collected as boiled coffee [48]. Boiled coffee consumption increases the blood cholesterol, since it contain considerable amount of suspended solid and is ingested along with the liquid. These contain insoluble diterpene, viz. cafestol which acts as a blood cholesterol up regulator. A simple filtering step through filter paper is enough to remove this fraction [49].
3.2.2 Turkish coffee The coffee is ground into very fine particle to increase surface area. Special equipment, viz. ibrik ( Figure 3.1) is loaded with ground coffee along with sugar. Then, it is filled with cold water and placed on an open flame. After reaching the ebullition temperature, revealed by vigorous foaming, the pot is removed from the flame and allowed to cool down and then replaced on the flame to a second time and there after third boiling. Then, the ibrik’s liquid content is collected. This method is popular in all the Mediterranean countries [48].
Figure 3.1 Turkish coffee
3.2.3 Percolator coffee During the extraction process the coffee brew is recycled several times along with the heating in percolator. Repeated circulation results more enriched
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coffee brew, exploiting the ground coffee completely. The beverage is harsh and unpleasant taste, along with the loss of aroma volatile compounds. Brewing of coffee in the aluminium percolator found to increase the aluminium content in the brew with the time of storage [50].
3.2.4 Vacuum coffee This coffee beverage is prepared in a special type of equipment consisting of two flasks – top flask and bottom flask. The top one is funnel-shaped glass flask with perforated screen. The ground coffee is placed on the perforated screen and water in the bottom flask. The assembly of the two vessels is heated up to boiling. Because of the steam pressure, the hot water forced into the upper vessel and mixes with the ground coffee and results in extraction. After the heat source is removed, the assembly is allowed to cool down until the pressure in the lower flask is reduced. The pressure is low enough to allow the upper liquid to flow down through the same funnel neck. The coffee beverage is served directly from the lower bowl. The commercial model of this equipment is called Cona [48].
3.2.5 Filter coffee The pulverized coffee is boiled in hot water for a short time. The hot water flows through partially soluble coffee bed continuously at a constant temperature between 80°C and 100°C. Due to the shorter contact time, the infused beverages are milder, enhanced acidity and more flavoured than the decocted ones. The typical set up for filter coffee consists of a simple device, where a filter paper is placed in a plastic cone-shaped holder. Medium ground coffee is put into the filter and the holder is placed on the top of a glass jug. Boiled water is then poured into the filter and allowed to steep through. This coffee is also known as drip coffee. Now many automatic or semi-automatic machines are available. The hot water drips at a controlled rate on the ground coffee for proper infusion. The machines are called drip coffee machines [48].
3.2.6 Napoletana coffee The instrument for this type of coffee is called macchinetta napoletana and is also known as flip drip pot. Gravity makes hot water to percolate through a bed of medium-coarse ground coffee. A pot, on top of which a perforated bushel contains the ground coffee, filled with water and heated indirectly by flames. After reaching the boiling point, the macchinetta is removed from the heat and turned upside down, allowing hot water to drip through the coffee into the second-half of the device. The main mechanical difference between drip filter and Napoletana method is that in the latter the ground coffee is immobilized
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between two filtering perforated plates, preventing the movement of the granules in the water. The water is flowing through the coffee and is not swing within the water. During the heating of water, the steam comes in contact with ground coffee and results scalding of coffee and causes bitterness in it [48].
3.2.7 Espresso brewing Espresso in Italian language means prepared at present or at this very moment. The coffee prepared by the espresso method could be immediately consumed soon after preparation relishing all the aroma and flavour of freshly ground and brewed coffee [48,51]. The espresso coffee beverage is a polyphase colloidal system, in which the liquid phase is topped by a wet foam of tiny sphereshaped gas bubbles. Each sphere is surrounded by a liquid film (lamellae) that separates it from its neighbours and hosts biopolymers and natural surfactants. Foaming biopolymers of coffee (proteins/melanoidins fraction and polysaccharides fraction) were extracted from defatted and roasted ground coffee [52]. Espresso coffee beverage is prepared from the roasted and ground coffee beans, by means of hot water pressure applied for a short time to a compact roast and ground cake by a percolation machine. Pressure is applied for the percolation of water through the ground coffee. Due to the driving force of pressure, the micron-sized solid particles and oil droplet goes along with coffee brew. This may change the beverage properties dramatically, enhancing the sensory characters [48]. Quantity of ground coffee and the parameters for a cup of espresso coffee beverage are as follows: • • • •
Ground coffee Water temperature Inlet water pressure Percolation time
- 6.5±1.5 g - 90±5°C - 9±2 bar - 30±5 s
The key role in espresso method is played by pressure. The pressure is transformed into kinetic energy. Some part of kinetic energy is transformed into the surface potential energy and partly into heat energy. This energy substantially modified the behaviour of ground coffee undergoing extraction. The external appearance and organoleptic character of beverage differs from the other methods of preparing coffee beverages. The liquid is crowned with an abundant layer of compact foam. This forms the oil in emulsion [51]. The peculiar organoleptic properties are due to the non-hydro soluble substances which are absent in the other methods of brewing. The emulsion of the liquid droplet imparts espresso its peculiar texture taste and mouth feel. Milk with little cream and sugar are added to taste. Espresso can also be taken with flavours like chocolate, cardamom and clove.
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The use of sophisticated machinery and technology enhances the visual olfactive and gustative characteristics of coffee beverage. In fact, maximum aroma can obtained with the espresso method due to the presence of essential oils, various colloidal substances and other noble components. Another advantage of espresso coffee is the drastic reduction of caffeine in the cup compared to the other methods of coffee brewing due to its short percolating time. It is estimated that the caffeine content of cup of espresso coffee is in between 60 and 120 mg while the content ranges from 150 to 300 mg per cup of coffee brewed employing other traditional method. Four important factors responsible for the preparation of espresso coffee are generally recognized as 4 M factors [51], which are as follows: • • • •
Miscella (blend) Macinino (coffee grinder) Maccihina espresso (espressomachin) Mano (hand of the operator)
Miscella (Blend) A good single variety of coffee may contain some deficiencies, which are to be complimented with a balanced combination of other varieties to even out the deficiencies and at the same time for enhancing the organoleptic qualities. The formulation of the different blends for espresso coffee is usually entrusted with a cup taster. A cup taster looks at the presence and combination of different characteristics like colour, body, sweetness, acidity, bitterness and a very intense aroma in different coffees while preparing blends for espresso machines. In the espresso type of coffee brewing, the colour of the final brew and the thick persistent foam or cream is having commercial importance. The foam acts as an aroma sealing cover and preserves the aroma and volatile oils. If the blends prepared by the cup taster are totally composed of Arabica then the colour of the espresso coffee liquor is deep hazel with reddish shades and with more thick and persistent cream. If the coffee is browner with greyish shades, less compact and less persistent cream, then the blend must be composed totally or dominant of Robusta coffees. These Robusta blends are less aromatic and bitter in taste.
(Macinino) Coffee grinder In the method of espresso coffee preparation, incorrect use of the coffee grinder can strongly affect the quality of coffee. If the hopper of the coffee grinder is kept unclean, the taste of rancid oils can be detected in the cup. Poor cleaning
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of dispenser outlet causes powder to become rancid and interfere with the doser, dispensing the right quantity. To avoid staleness in the espresso cup, minimum amount of coffee powder is kept in the dispenser and in the grinder, just enough for 30 min consumption. It is also important that during grinding the temperature should not exceed 40–50°C. A temperature of more than 50°C will burn the components of the ground coffee and impoverish the cup of espresso coffee, which will become harsher, bitter and certainly less aromatic. In the espresso preparation, the grain size of coffee powder is very important. Generally, fine grind is preferred for espresso coffee preparation. The roasted coffee beans should ground according to the prevailing atmospheric humidity. If the humidity is high, slightly coarser grind is required, and if humidity is low, finer grind is required. If the grain size is coarser, the machine will produce under extracted coffee and when the grain size is over fine the machine will produce over extracted coffee.
Maccihina Espresso ( Espresso machine) The function of espresso machine is to provide energy, i.e. heat and pressure to the water, enabling it to pass through the fine coffee powder swiftly so as to extract its best qualities. The heat around 92°C [53] and the pressure of 9–10 bars are provided by hot water in the boiler and electro magnetic pump respectively. The espresso machine consists of following components. • • • • •
Gas or electricity (source of heat) Exchanger (hot water element) Pump Hot water tap Control instruments
(Mano) Hand of the operator The 4th “M” corresponds to the Mano which is the hand of the operator. Today, with the use of the modern and fully automated espresso machines the word ‘Mano’ can be changed into ‘Mente’, which means the mind of operator. In the most advanced and complicated models of espresso machines, the instruments are provided with functions like measure consumption, checking cleanliness, and wear and tear. Naturally, an operator of these machines is required to use more of his mind than his hand. Perfect application of all the four “M” factors give a perfect espresso coffee which must have a compact, fine grained long lasting cream/foam and a fine button hole. The foam must be persistent, long lasting and 3–4 mm thick.
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Colours vary from deep hazel to dark brown with reddish shades and light hazel streaks. Taste must be sweet with slight acidity, a pinch of bitterness, chocolate like taste, intense aroma and pleasant after taste [51].
3.3 Canned coffee beverages Pre-brewed canned coffee beverage is a convenient product, where right brewing equipment is not available. The pleasure of the canned coffee is not as good as that of the fresh one. Pre-brewed coffee is filled in cans and subjected to sterilization, pasteurization, etc. Prolonged heating of coffee causes taste deterioration due to degradation products of acids [54].
3.4 Ready-mix coffee beverage All the ingredients in this coffee beverage are in the dry form. The soluble coffee, milk powder and sugar are mixed in the proportion 1:5:10. For getting homogeneous mixture, all the ingredients are thoroughly mixed. The particle size of all the ingredients should be uniform. This coffee beverage is highly hygroscopic in nature, so the packaging material possesses barrier properties to both oxygen and moisture. Shelf-life is very short (~10 days). However, shelf- life of the coffee ready mix is enhanced through vacuum packaging or inert gas packaging. About 25 g of the mix are needed for a cup (8 oz) of coffee [55].
3.5 Coffee–milk admixture
In coffee–milk admixture, the milk adjusts or masks the objectionable flavour of the coffee brew. The milk fat emulsions maintain the aroma balance of coffee brew. The milk fat improves the appearance, texture and after-taste persistence of coffee drink. The protein and fat contents in milk are critical to the foam development. Skimmed milk contains the greatest percentage of the protein, and foams better than the low fat or whole milk. The fat content in the milk helps to keep the foam stable [48]. Milk proteins (casein and whey proteins) and milk fat influence the release of flavour compounds from white coffee beverage in the oral cavity. For this reason a retro-nasal headspace technique for measurement of the flavour was adapted. A gas sampler equipped with a mouthpiece was used as an Oral Breath Sampler (OBS). Analyses were performed by gas chromatography with mass spectrometric detection. It was noticed that the sampling at different hours resulted in different standard deviations. The flavour release is more constant in the morning (Variation coefficient from 3% to 28%; median: 10%) than in the afternoon (7–52%; median: 23%). The relationships between flavour release and some salivary
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parameters like salivation rate, buffer capability and protein content were also studied. The Oral Breath Sampling was considered to be a valuable sampling method for the analysis of the retro-nasal aroma release from coffee beverages [56].
3.6 Coffee jelly beverage Coffee jelly beverage (Figure 3.2) is prepared by regulating a solution containing coffee and jellying agent at a pH less than 4.0 using acid. The acidifier may be either of phosphoric acid, gluconic acid or phytic acid. Generally, phosphoric acid is chosen. The amount of sugar required is in the range of 0.1–20% by weight. After preparation of solution, it is subjected to sterilisation process at a temperature of 65–100°C [57].
Figure 3.2 Coffee jelly beverage
3.7 Fortified coffee beverages Iron-fortified soluble coffee is prepared in two steps, viz. precipitation of polyhydroxyphenols and polyhydroxyphenol-polysaccharides from the coffee extract at 2–20°C; addition of an assimilable elemental iron at the rate of 0.01–1% by weight of coffee solids. Liquid coffee extract having a solid concentration of about 10–30% was maintained at a temperature below about 70°F for a period of time sufficient to precipitate the components which interact with elemental iron. Then, the extract was clarified and fortified with nutritive ingredients including a soluble iron compound containing assimilable iron, and then dried by freeze drying [58].
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3.8 Fortified coffee drink A soluble powder that produces a low-fat coffee beverage fortified with vitamins and minerals when reconstituted with water is described. The powder consists of an instant coffee component, a protein component, a vitamin/mineral component which provides greater than or equal to 25% of the United States Recommended Daily Intake (US RDI) per 8 oz serving, and a carbohydrate component which provides approximately 140 cal/8 oz serving [59].
3.9 Honeyed coffee Honey coffee is prepared from dry de-pulped coffee beans. The coffee beans are dried as such along with the parchment and mucilage on a perforated conveyer over a period of 1–20 days. During the process of drying, the sweetness in coffee increases since the coffee beans absorb water, sugars and other constituents from the mucilage by capillary processes. Further processing is done as per the conventional method [60].
3.10 Coffee tablet Kaku and Chandler developed a process for the preparation of coffee tablet [61]. The roasted coffee is compressed in a roller press (briquette press) to form a tablet which is then crushed to provide and agglomerate, and later introduced into a sachet for beverage preparation. In an alternate method, coffee tablet is prepared by mixing ground coffee with hydrophilic substance. The hydrophilic substances absorb water. Then the mixture is compressed into tablet form. The tablet is used in preparation of coffee drink [62]. Coffee tablets with integrated aroma are obtained by combining the dry instant coffee with roast coffee aroma concentrate. The coffee tablet is packaged in retail containers similar to those used for pharmaceutical tablets [63].
3.11 Freeze-dried coffee tablets The freeze-dried coffee tablet is used in beverage preparation. These tablets are prepared through moulding and freeze-drying a solution of coffee solids into a desired shape. It has improved solubility, a smooth surface and porous nature in which most of the pores are interconnected, and are between 10 and 50 µ in size. A coating can also be added to the tablet containing coffee flavourings, colourants or aroma compounds. The coffee tablet is packaged in an aroma-filled environment, leading to a product that exhibits fresh, strong flavour and aroma upon beverage preparation, even after long-term storage [64].
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3.12 Flavoured coffee 3.12.1 Cerelac flavoured with instant coffee Instant coffee is added to the cerelac (nutritious food for health and growth) by physical mixing. Composition, microbiological quality and sensory quality are compared with those of the original product of cerelac. Coffee flavoured with cerelac showed high sensory quality and acceptance; composition and microbiological quality are similar to those of the original type of cerelac [65].
3.12.2 Flavoured coffee paste Flavoured coffee paste is prepared by mixing of the concentrated coffee extract with pulverized coffee bean. The average size of the pulverized coffee grain is about 30–50 µ [66].
3.12.3 Yoghurts flavoured with instant coffee Yoghurts are flavoured with instant coffee at concentration of 0.5%, 0.7% and 0.9%, and sweetened with sugar (4 or 5%). Physicochemical, microbiological and sensory properties of experimental yoghurts are compared with those of control yoghurt (no coffee or sugar). It is found that the added ingredients generally have no effect on the chemical, physical and microbiological quality of yoghurts initially as compared to the control. During 15 days storage at 57°C, pH and lactic acid bacteria counts decreased and titratable acidity increased in all samples. Yoghurts with 0.5% coffee flavouring and 4 or 5% sugar met Turkish Institute Standards for yoghurt sensory quality when evaluated by a trained 10-member panel. Yoghurt flavoured with 0.5% coffee as well as 5% sugar possessed most attributes rated in the 'like' category by 50% or more of consumer panellists [67].
3.12.4 Flavoured coffee beverage Coffee can be flavoured with vanilla nut, Irish cream, chocolate, vanilla, macadamia nut, chocolate almond, coconut, cinnamon and chocolate raspberry cream. The flavouring substances are used either in a liquid form or in a powder form. The key operation is thorough mixing of the liquid additive with whole roasted beans or powder flavouring agent with ground coffee. The flavouring agent is mixed at 2% concentration. The new way of flavouring the coffee beverage is by directly putting the flavour-coated stirrer into the cup. During the agitation, the flavoured ingredients are released from the stirrer to make flavoured coffee [48].
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3.13 Coffee wine Coffee wine is prepared using a wine-making procedure. Brewed wines are manufactured from Cavita coffee beans. Wines are fermented in polycarbonate plastics containers, rather than wooden barrels, in order to avoid methanol formation. Boiling and filtration stages are carried out to ensure high quality wine. Distillation is avoided in order to preserve natural flavour of the raw material. Wines obtained are free from methanol and contain an ethanol content of about 12.5% [68].
3.14 Candy from coffee beans The coffee beans are roasted at 200–270°C in a fluidised bed using a mixture of steam and coffee roasting gases. After roasting for 70–200 s, crystalline sugar or sugar solution (2–4 g sugar per gram of water) are finely dispersed onto the fluidised bed. The sugar dries and caramelises on the surface of the coffee beans to form a uniform layer over each coffee bean. The coffee beans, still fluidised, are then cooled to 10–60°C with ambient air over a period of 110–400 s. Cooling may take place in 2 stages. The preliminary cooling to set the candied sugar coating so the coffee beans do not stick together and followed by final cooling [69].
3.15 Torrefacto coffee Torrefacto coffee is prepared by the coating of roasted coffee beans with caramelised sugar. Green coffee beans are roasted, cooled and coated with caramelised sugar (in aqueous solution) to give a caramelised sugar content of 5–15% by weight. The finished product may be marketed as whole or ground coffee beans [59].
3.16 Germinated coffee Germinated coffee contains good balance of nutrients particularly, amino acids and it possesses a mild flavour. It may be used in both beverages and processed foods. Fresh coffee beans are immersed in water at a temperature of 5–50°C until they absorb the water required for germination. Water (20–40°C) is sprayed during germination process to avoid drying. After germination, these are washed with water to remove extraneous matter and dried until their water content is reduced to approximately 11% or below. The germinated coffee beans are stored and distributed like fresh coffee beans [70].
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3.17 Coffee filled packet Coffee bean particles are filled in the water permeable packet. The packet size should fit between the cheek and gum. This packet is directly placed into the mouth. This type of packet is used when an individual is away from civilization or has no access to hot water or a coffee maker [71].
3.18 Cookie formulation with coffee Three varieties of cookie are formulated using coffee as espresso beverage, instant coffee and roasted coffee powder. The average proximate composition (dry basis) of the formulation is 70% carbohydrates, 8% protein, 21% fat and 1% minerals. The average calorific value of each formulation is 499 kcal/100 g products. Both the proximate composition and average calorific value is similar to the values reported for existing commercial brands of cookies. The sensory properties (flavour and texture) of cookies are influenced by the way in which coffee is added to formulation. The formulation employing the espresso beverage is presented in lower values for cracking, crumbling, presence of dark spots and coffee as well as burnt flavour. The product manufactured using the instant coffee powder exhibited higher values for brown colour intensity, shine, coffee as well as burnt flavour along with residual brown sugar flavour and crunchiness, and lower values for concavity. Samples made with roasted coffee powder displayed higher values for the presence of dark spots. All three formulations showed satisfactory acceptance levels when assessed [72].
3.19 Coating of frozen pizza with coffee colorant Microwave processed pizza involved coating of the outer edge of the pizza crust with an aqueous colouring solution, containing an edible dispersion agent and a natural colorant such as coffee [73].
3.20 Carbonated coffee It is sparkling carbonated beverage containing coffee brew, sugar, acid, carbon dioxide and preservatives. Its preparation consists of mixing of sugar syrup, coffee brew, acids, preservatives followed by dilution and carbonation. It is best enjoyed as a chilled beverage. It is possible to replace the coffee brew with soluble coffee powder. Because of coffee aroma, it is called coffee flavoured novel beverage. This beverage is also flavoured with chocolate, cardamom, vanilla for better value addition. It has shelf-life like that of any other soft drink [12].
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3.21 Decaffeinated coffee Caffeine present in coffee is responsible for most of the physiological effects of the beverage. Selected people do not tolerate caffeine. It stimulates the central nervous system, shows toxicity when fed in excess and is even mutagenic in vitro [74, 75]. It can cause excessive influence on the central nervous system and respiratory system. The symptoms are restlessness, excitement and insomnia. Excessive consumption of caffeine through beverages is associated with a number of health problems like adrenal stimulation, irregular muscular activity [76,77), cardiac arrhythmias [78] and increased heart output. Excess caffeine is reported to cause mutation, inhibition of DNA repairs and inhibition of adenosine monophosphodiesterase [79], and during pregnancy causes malformation of foetus and may reduce fertility rates [80]. The various decaffeination processes are presented in Fig. 3.3. Green coffee beans Water
Wet beans
Solvent
Water
Solvent rich Decaffeinated beans in caffeine wet beans Solvent Caffeine
Solvent removal
Caffeine rich extract
Super critical CO2
Decaffeinated wet beans Drying
Decaffeinated wet Drying
Caffeine
Decaffeinated coffee beans Figure 3.3 Various decaffeination processes of coffee
Decaffeination of coffee is reported using organic solvent, water and super critical carbon dioxide, and biological method [81]. The impact of the water decaffeination process on chlorogenic acid (CGA) and chlorogenic gammaquinolactones (CGL) levels of green and roasted arabica coffees was evaluated
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[82]. Decaffeination produced on an average a 16% increase in the levels of total CGA in green coffee. In this process, water is used as the extracting solvent and extraction is carried out at about 90–95°C. Super critical carbon dioxide method of decaffeination of coffee was studied by [83]. Under high pressure, carbon dioxide gas acts like a fluid and can be used as a solvent and decaffeination of coffee beans is done. Studies on the degradation of caffeine were carried out using a strain of Pseudomonas alcaligenes CFR 1708, isolated from coffee plantation soil [84]. Gokulakrishnan et al reported that the different microbial and enzymatic methods of caffeine removal [85]. The literature revealed that major caffeine degrading strains belong to Pseudomonas and Aspergillus.
3.22 Soluble coffee Soluble coffee is ready in an instant. It is transportable and has a long shelflife. Value-added soluble coffee products such as iced coffee and flavoured cappuccinos are popular in convenience stores. Many consumers use it by choice as a quick caffeine fix in the morning [86]. Instant coffee spoils fast if it is not kept dry. Instant coffee differs in make-up and taste to ground coffee. In particular, the percentage of caffeine in instant coffee is less, and bitter flavour components are more evident. Bel-Rhlid describes the method for reduction of the bitterness in soluble coffee [87]. The lowest quality coffee beans are often used in the production of soluble coffee. Silver and Whalen describes enzyme-assisted soluble coffee production [88]. The method for producing the soluble coffee involves combining roast and ground coffee with water, adding hydrolase enzymes, wet-milling to a mean particle size of approximately 10–250 µ,treating the reaction mixture at a temperature of approximately 50–60°C, and circulating the reaction mixture through a crossflow, semi-permeable membrane separation device to yield a soluble coffee extract. Sediments are a major problem in the instant coffee preparation. This problem is due to the galactomanon fraction of polysaccharides. This problem can be solved by enzymatic hydrolysis during the extraction processes of soluble coffee fraction. The highest sediment reduction was obtained using Rophapect and Galactomannanase at concentrations of 0.3 and 0.1 mg protein per gram substrate, respectively [89]. The fundamental steps of soluble coffee preparation are shown in the Fig. 3.4. Boss et al optimised the temperature and time for the freeze drying of soluble concentrate [90]. The biggest problem is the time of drying, since the longer the time, higher are the energy costs. Because of this, the goal function is to minimize the drying time for the soluble concentrate of coffee. However, it is found that the actual industrial processing takes much more time with less
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removal of water compared to the optimised time of processing. Further, it was reported that retention of water in the real industrial data is more than the optimised data against the time. The optimisation of the freeze drying process is a tool of extreme importance which should be used to decrease the processing time as well as to decrease the cost of the process. It is also observed that the process is very sensitive and small alterations in suitable variables may allow the process to be operated with larger efficiency and productivity. Green coffee beans
Roasting
Grinding
Blending
Extraction
Concentration
Drying and agglomeration Aroma Soluble coffee
Figure 3.4 Conversion of green coffee into soluble coffee
3.23 Instant hot cappuccino Dry mix instant hot cappuccino coffees consist of water-soluble coffee, a foam generator, an optional cream and an optional sweetener. The foam-
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generating component comprises gluconolactone and an alkali metal carbonate or bicarbonate. Cappuccino beverages are prepared by mixing a liquid component and the dry mix composition and heating. A good quality cappuccino is produced with either dairy or non-dairy creamer. With dairy creamers, the formation of floating white aggregates on the surface of the beverage is avoided. Cappuccino coffee is prepared from the espresso coffee beverage. For the preparation of the cappuccino dry-mix, foaming creamer composition comprising a particulate protein component in an amount from 1 to 30%, a foam-generating carbohydrate (a bulk density of less than 0.3 g/cc) in an amount of 20–90% and a lipid in an amount of 0–30% are taken [91].
3.24 Monsoon coffee Monsooning of coffee beans is a flavour induction process employed in India, where coffee beans are exposed to moist monsoon winds in open warehouses. Monsooned coffee is prepared in west coast of India during monsoon season. The varieties used in preparation of monsoon coffee are AA and AB grades of arabica and Robusta. The beans are exposed to a humid atmosphere causing them to absorb moisture upto 15–16%. The green coffee is spread in wellventilated brick-floored warehouses to a thickness of 4–6 inches during the monsoon season. The coffee beans are raked periodically and exposed to humid atmosphere for periods ranging from 6 to 8 weeks. These are packed in loosely woven gunny bags, stacked, bulked and re-bagged. This result in swelling to one-and-half times the normal size of cherry beans and a change in colour to pale white or golden/light brown. These swollen beans are then polished through hullers, graded and garbled by sorter. Through monsooning, the dry-processed coffee acquires a special natural mellow flavour. Monsooned Arabica / Monsooned AA and Monsooned Robusta AA are in great demand in the international market. Indian monsooned coffee is mainly exported to Europe [92].
3.24.1 Flavour compounds in monsooned coffee Volatile aroma principles, non-volatile flavour compounds (caffeine, and chlorogenic and caffeic acids), and glycosidically bound aroma compounds of monsooned and non-monsooned raw arabica coffee were analysed using GC-MS and HPLC. The most potent odour-active constituents known to contribute to the aroma of the green beans are 3-isopropyl-2-methoxypyrazine, 3-isobutyl-2-methoxypyrazine, 4-vinylguaiacol, beta-damascenone, (E)-2nonenal, trans-2, 4-decadienal, phenylacetaldehyde and 3-methylbutyric acid. A decrease in content of methoxypyrazines and an increase in 4-vinylguaiacol and isoeugenol resulted in a dominant spicy note of monsooned coffee.
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These phenols exist partly as their glycosides and their release from the bound precursors during monsooning accounted for their higher content in monsooned coffee. A considerable decrease in astringent chlorogenic acid as a consequence of hydrolysis to bitter caffeic acid was noted in monsooned coffee [93].
3.24.2 Impact of gamma irradiation on the monsooning of coffee beans High-moisture content during monsooning process favours the growth of microorganisms on coffee beans, which affects the product quality. Coffee beans (Arabica and Robusta varieties) were subjected to gamma-irradiation at 5 and 10 kGy doses. Both treatment doses reduced populations of natural mycoflora on beans with a greater effect observed at 10 kGy. Prior to monsooning, Aspergillus niger was the predominant fungal species on coffee beans however, A. ochraceus became the dominant species during monsooning. Other Aspergillus spp., Penicillium spp., Absidia spp., Syncephalastrum spp., Mucor spp. and Rhizopus spp. were also identified in samples, in much lower numbers. During monsooning, fungal growth occurred at a lower rate on gammairradiated samples compared with non-irradiated samples. Monsooning time was substantially reduced by gamma-irradiation; completion of monsooning took 5 weeks in non-irradiated samples, compared with 2 weeks for samples subjected to gamma-irradiation [94]. Radiation processing of non-monsooned beans at a dose of 5 kGy resulted in an increased rate of monsooning. At this dose, a quantitative increase in most of the aroma active components could be observed in all samples studied. Hydrolysis of chlorogenic acid to caffeic acid was noted in radiationprocessed monsooned coffee beans irrespective of whether the treatment was carried out before or after monsooning [93].
3.25 Coffee paste This is a ready-to-serve coffee beverage in highly concentrated form. The liquid ingredients, milk and coffee brew are separately concentrated, mixed with sugar thoroughly to obtain the product in a paste form. During the extraction of coffee powder, the aroma rich initial extract is collected separately and mixed with the concentrated milk and brew in the end. This product is best canned and stored under refrigerated conditions. Consumer (unit) packs can be made in aluminium-foil-laminated pouches [13].
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4 Value-added by-products
4.1 Introduction The waste products from the coffee industries consist of silver skin, parchment, mucilage, pulp, etc. In the conventional way these are utilised for the production of the manure, compost, fertilizer and live stock feed. However, these applications utilise only a fraction of available quantity and are not technically very efficient. Using the recent technologies, value added products can be obtained from coffee industry waste which is much more economical than the conventional method of utilising the coffee waste. Byproducts from coffee processing are presented in Fig. 4.1. Advances in industrial biotechnology offer potential opportunities for the economic utilisation of agro-industrial residues such as coffee pulp and coffee husk. Coffee pulp or husk is a fibrous mucilaginous material, obtained during the processing of coffee cherries by wet or dry process respectively. Coffee pulp/ husk contain some amount of caffeine and tannins, which makes it toxic in nature, resulting in the disposal problem. However, it is rich in organic compounds, which makes it an ideal substrate for microbial processes for the production of value-added products. Several solutions and alternative uses of the coffee pulp and husk have been attempted. These include fertilizers, livestock feed, compost, etc. However, these applications utilise only a fraction of available quantity and are not technically very efficient. Attempts have been made to detoxify for improved application as feed, and to produce several products such as enzymes, organic acids, flavour and aroma compounds, mushrooms etc, from coffee pulp/husk. Solid-state fermentation has been mostly employed for bio-conversion processes [95].
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Dry process
Washing
Wet process
Drying
De-pulping
Cleaning
Coffee pulp
De-hulling
Mucilage
Fermentation Washing
Selection Hulls
Packing
De-hulling Drying
Quality coffee
Coffee husk
Packing Quality coffee
Figure 4.1 Industrial processing of coffee and coffee by-products
4.2 Source of dietary fibre Coffee is a major food commodity, therefore coffee by-products are amply available. The coffee silver skin (CS) is a tegument of coffee beans that constitutes a by-product of the roasting procedure. The process of obtaining the silver skin from coffee is presented in Fig 4.2. The coffee silver skin can be used as potential source for the dietary fibre, antioxidative activity and prebiotic activity [96].
4.3 Coffee spirit Bodmer and Ruder developed a process for the production of spirit (alcohol ≤ 20%) from the coffee cherries [97]. The flesh of the coffee cherries is separated
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and is subjected to the fermentation process by adding sugar. The fermented material is subjected to distillation processes for separating the alcohol. The distillate can be used for the drinking after dilution. Coffee cherries Mechanical removal
Outer skin and pulp Mucilaginous parchment beans
Fermentation
Remaining mucila ge
Parchment beans Drying dehulling
Parchment hulls Raw beans
Roasting
Coffee silver skin Roasted coffee beans
Figure 4.2 Production of silver skin (CS) from wet processing of coffee
4.4 Charcoal production Charcoal is produced from the dried coffee bean residues using carbonisation process. The carbonisation process is done at higher temperature of 800, 1000 or 1200°C. The prepared charcoal is sieved, washed and dried. Charcoal from waste coffee ground is a very useful source for the removal of acidic dye. The charcoal from the spent coffee can be used for the decolourisation of acidic dye, viz. acid orange 7 [98].
4.5 Mushroom cultivation Industrial coffee wastes such as coffee husk and spent coffee ground are used for the production of Pleurotus ostreatus by the solid-state fermentation (SSF). Coffee pulp is a substrate component for Pleurotus ostreatus production [99]. Using coffee husk and spent coffee ground as substrates without pre-treatment for cultivation of an edible fungus in SSF, provides a better step towards the utilisation [100].
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4.6 Production of citric acid and gibberellic acid Citric acid is produced from the coffee husk by the processes of SSF, using the Aspergillus niger CFTRI 30 strain as the culture. This strain produces 1.3 g citric acid per 10 g of dry coffee husk in 72-h solid-state fermentation. Production is increased by 17% by adding a mixture of iron, copper and zinc to the medium. The sugar conversion rate is 84%. Hence, the coffee husk is the potential source for the production of citric acid [101]. Machado et al reported that the production of gibberellins (plant hormones) in submerged fermentation (SmF) and SSF, utilising coffee husk as the carbon source [102]. Five strains of Gibberella fujikuroi and one of its imperfect state, Fusarium moniliforme, were used for comparison. Results showed the production of gibberellic acid (GA3) in all the fermented samples. SSF appeared superior to SmF.
4.7 Antioxidant compounds Yen et al evaluated the antioxidant activity of roasted coffee spent residues, in different in vitro model systems [103]. The coffee spent residues have excellent potential for use as a natural antioxidant source because the antioxidant compounds remain in roasted coffee residues. The antioxidant activity of spent coffee residues may be due to the presence of phenoloic compounds such as chlorogenic acid and caffeic acid.
4.8 Source of natural food colour The anthocyanin content and profile of fresh coffee husks (outer skin and pulp) were analysed. Cyanidin 3-rutinoside was the major anthocyanin encountered in the extracts, followed by a small amount of cyanidin 3-glycoside. Thus, the fresh coffee husk can be used as potential source of natural food colour [104].
4.9 Production of aroma compounds A novel approach on value addition of coffee husk is to use it as a substrate for the production of aroma compounds for food industry application with yeast and fungi. Soares et al used the yeast Pachysolen tannophilus in SSF for synthesizing aroma compounds, using coffee husk as a medium. The yeast culture produced a strong alcoholic aroma with fruity flavour. Along with ethanol, which was the major compound produced, acetaldehyde, ethyl acetate, isobutanol, isobutyl acetate, ethyl-3-hexanoate and isoamyl acetate
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were also produced by the culture, giving a strong pineapple aroma. When leucine was added to the medium, a strong banana odour was found with increased amounts of isoamyl alcohol and isoamyl acetate [95].
4.10 Biogas production Attempts have been made to use coffee industry residues, mainly coffee pulp and husk for biogas production in anaerobic digestion. According to the estimates, from one ton of coffee pulp, about 131 m3 biogas could be produced by anaerobic digestion which would be equivalent to 100 l of petrol in fuel value. Robusta and arabica coffee solid residues generate about 650 and 730 m3 methane per ton of solids, respectively [95].
4.11 Source of phenolic compounds Agro-industrial by-products are a potential source of value added phenolic acids, with promising applications in the food and pharmaceutical industries. Two purified forms of feruloyl esterases from Aspergillus niger, Feruloyl Esterases A and Feruloyl Esterases B, were tested for their ability to release phenolic acids such as caffeic acid, p-coumaric acid and ferulic acid from the coffee pulp. Feruloyl esterase B is a potential source for releasing of phenolic compound from the coffee pulp [105].
4.12 Summary and conclusion The major coffee-producing countries are Brazil, Vietnam, Columbia, Indonesia, Ethiopia, India, Guatemala, Mexico, etc. Among these, Brazil is first in the production and India is at 6th position in production. India accounts for about 4% of world coffee production. Main importing countries of Indian coffee are Italy, Germany, Russian federation, Spain, Belgium, Slovenia, USA, Japan, Greece, Netherlands and France. The fruit of coffee is called berry. It consists of the two flat-shaped coffee beans. The bean is surrounded by silverskin, pulp and outer skin. The bean is made up of the endosperm, which is the commercial edible part. Coffee fruits are processed for the production of parchment coffee and cherry coffee beans. The parchment coffee is prepared by wet processing method and the cherry coffee is prepared by dry processing method. The green coffee is further subjected to processing for the production of the coffee roast and the coffee ground. Roasting is the most important step in the coffee processing. It provides the unique characteristics of the coffee such as physical and the chemical properties. Utmost care is taken for the production of the good coffee product during the roasting.
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Coffee contains a complex mixture of chemical compounds. Substances that dissolve in water to form the beverage during brewing are classified as nonvolatile components (viz., caffeine, trigonelline, chlorogenic acid, phenolic acids, amino acids, carbohydrates, and minerals) and volatile components. Volatile aroma components include organic acids, aldehydes, ketones, esters, amines, and mercaptans. The aroma related to the aroma chemicals are produced during roasting of the green beans. It is generally accepted that caffeine is responsible for many of its physiological effects. Caffeine influences the central nervous system in a number of ways mainly it enhances alertness, concentration, and mental and physical performance. Coffee has been enjoyed as a drink by millions of people worldwide for over at least one thousand years. The various value-added products that obtained from the coffee are boiled coffee, turkish coffee, vacuum coffee, filter coffee, espresso coffee, canned coffee beverages, ready mix coffee beverage, coffee–milk admixture, coffee jelly beverage, fortified coffee beverages, fortified coffee drink, honeyed coffee, flavoured coffee, coffee wine, candy coffee, torrefacto coffee, germinated coffee, cookie formulation with coffee, carbonated coffee, decaffeinated coffee, instant hot cappuccino, monsoon coffee, Instant coffee etc. Each value-added product has its own speciality in terms of preparation and quality. There are many value added products are available in the market. The consumer acceptance to value added products is ever increasing. The consumer preference changes as the time passes. So continuous research, regarding the value addition to the coffee has to be kept on alert for developing further the new coffee value added products. Lastly, any industry in order to maximize the profits and maintain the environmental policy, they are converting the industrial waste into the suitable value added by-products. Value addition to the coffee waste is done through biotechnological processes. Now many biotechnological processes have been developed for the production of the value added products from the coffee waste. The various value added products that obtained from the coffee waste are dietary fibre, coffee spirit, charcoal, production of mushroom, citric acid, gibberellic acid, antioxidant compounds, natural food colour, aroma compounds, biogas, phenol compounds etc. These compounds are the potential sources for the further utilization in the food industries and pharmaceutical industries. Regarding the value addition to the coffee waste one has to consider the economics of obtaining these by-products.
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References
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[22] Steinhart, H. and Luger, A. (1997). An analytical distinction between untreated and steam treated roasted coffee. Seventeenth International Scientific Colloquium on Coffee, ASIC, Nairobi, pp. 155–160. [23] Sivetz, M. and Desrosier, N. (1979). Coffee Processing Technology, Connecticut: AVI, pp. 1–703. [24] Czerny, M. and Grosch, W. (1999). Potent odorants of roasted coffee and their changes during roasting. Journal of Agricultural and Food chemistry, 48: pp. 868–872. [25] Clement, R. L. and Deatherage, F. E. (1957). A chromatographic study of some of the compounds in roasted coffee. Food Research, 22: pp. 222–232. [26] Abraham, K. O. (1992). Coffee and coffee products, In: Guide on Food Products Vol. 2, Bombay: Spelt Trade, pp. 1–13.
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[39] Higgins, L. G, Cavin, C., Itoh, K., Yamamoto, M., Hayes, J. D. (2007). Induction of cancer chemopreventive enzymes by coffee is mediated by transcription factor Nrf2. Toxicology and Applied Pharmacology, 226: pp. 328–337. [40] Smith, A. (2002). Effects of caffeine on human behaviour. Food Chemical Toxicology, 40: pp. 1243–1255. [41] Klatsky, A. L., Amstrong M. A., and Friedman, G. D. (1993). Coffee, tea and mortality. American Journal of Epidemiol, 3: pp. 375–381. [42] Mandel, H. G. (2002). Update on caffeine: consumption, disposition and action. Food Chemical Toxicology, 40: pp. 1231–1234. [43] Cook, D. G., Peacock, J. L., Feyerabend, C., Carey, I. M., Jarvis, M. J., Anderson, H. R. and Bland, J. M. (1996). Relation of caffeine intake and blood caffeine concentrations during pregnancy to foetal growth: prospective population based study. BMJ, 313: pp. 1358–1362. [44] Sakamoto, W., Nishihira, J., Fujie, K., Iizuka, T., Handa, H., Ozaki, M. and Yukawa, S. (2001). Effect of coffee consumption on bone metabolism. Bone, 28: pp. 332–336. [45] Sesso, H. D., Gaziano, J. M., Buring, J. E. and Hennekens, C. H. (1999). Coffee and tea and the risk of myocardial infarction. American Journal of Epidemiology, 149: pp. 162–167. [46] Atanas, G. A., Anna, A. D., Roberto, A. S., Schweizer, L. G., Nashev, E. M. and Maurer, A. D. (2006). Coffee inhibits the reactivation of glucocorticoids by 11b-hydroxysteroid dehydrogenase type 1: A glucocorticoid connection in the anti-diabetic action of coffee. FEBS Letters, 580: pp. 4081–4085. [47] Alan, H. V. and Jane, P. S. (1994). Coffee. Beverages, 2: pp. 191–236. [48] Petracco, M., (2001). Beverage preparation. In: Coffee Recent Developments, Clarke R. J. and Vitzthum, O. G. (eds.), pp. 140–162. [49] Urgert, R. (1997). Health effect of unfiltered coffee. Thesis, Agricultural University of Wageningen, The Netherlands. [50] Lione, A. A., Allen, P. V. and Crispin Smith, J. (1984). Aluminium coffee percolators as a source of dietary aluminium. Food and Chemical Toxicology, 22(4): pp. 265–268. [51] Basavaraj, K. (1997). Espresso coffee drinking. Indian Coffee, 61(7): pp. 3–5. [52] Piazza, L., Gigli, J. and Bulbarello, A. (2008). Interfacial rheology study of espresso coffee foam structure and properties. Journal of Food Engineering, 84: pp. 420–429.
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[53] Andueza, S., Vila, M. A., de Pena, M. P. and Cid, C. (2007). Influence of coffee/water ratio on the final quality of espresso coffee. Journal of the Science of Food and Agriculture, 87(4): pp. 586–592. [54] Yamada, M., Komatsu, S. and Shirasu, Y. (1997). Changes in components of canned coffee beverage stored at high temperature. In: Proceedings of the 17th ASIC Colloquium (Nairobi), pp. 250–210. [55] Gopalakrishna Rao, Natarajan, C. P. and Balachandran, A. (1970). Ready-mix coffee beverage. Indian Coffee, 34 (1): pp. 12–14. [56] Denker, M., Parat Wilhelms, M., Drichelt, G., Paucke, J., Luger, A., Borcherding, K., Hoffmann, W. and Steinhart, H. (2006). Investigation of the retronasal flavour release during the consumption of coffee with additions of milk constituents by oral breath sampling. Food Chemistry, 98: pp. 201–208. [57] Yamaguchi, T., Tsuchiya, H. and Kawauma, T. (2007). Coffee jelly beverage. JP 189922A. [58] Klug, S., Patrizio, F., Einstman, J., William, J. (1977). Iron-fortified soluble coffee and method for preparing same. US4006263. [59] Atkinson, J. R., Deis, D. A. and Marchio, A. L. (2001). Fortified coffee drink, U S 6207203B1. [60] Ros G. C. (2006). Procedure is for production of sweetened coffee, involves cleansing of impurities from gathered beans, selection by flotation and dry pulp extraction ES 2264375. [61] Kaku, K. and Chandler, K. P. (2004). Preparation of a coffee tablet. GB2394165A. [62] Barani, R. and Avanesions Z. S. (1997). A tablet for preparation of coffee drinks and a process for obtaining the tablet, EP 0813816A1. [63] Falkenstein, K. (1997). Coffee tablets with integrated roast aroma, US 2264375A1. [64] Kessler, U. (2004). Freeze dried coffee tablets. GB 2394163A. [65] Martinez G. G., Espinosa V. B., Valdez F. L. and Garcia U. A. (2003). Flavoured coffee. Alimentaria, 342: pp. 13–14. [66] Koda, M. and Takigawa, T. (2007). Flavoured coffee paste and method for producing the same, JP 289035A. [67] Tan, G. and Korel, F. (2007). Quality of Flavoured yogurt containing added coffee and sugar. Journal of Food Quality, 30(3): pp. 342–356.
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[68] Castaneda, R. R. (2003). Three fermented wines in same formula. Don Roberto’s sweet (yellow) mango wine, (dry) green mango wine and brewed coffee wine, WO 03/010279A1. [69] Winkelmann, M., Roebert, L., Arndt, T., Roesler, M., Moerl, L., Krueger, G. and Heinrich, S. (2000). Process for candying of coffee beans, DE 19902786 C1. [70] Ichikawa, H. (2008). Germinated coffee, WO 029578A1. [71] Gillenwater, R. E. and Gillenwater, L. A. (2008). Coffee filled packet, GE 2394164A. [72] Abreu A. R. M., Silva L. G., Silva F. A. and Motta, S. (2007). Development of cookie formulations containing coffee. Ciencia-eTecnologia-de-Alimentos, 27(1): pp. 162–169. [73] Peleg, Y. (1993). Microwave reconstitution of frozen pizza, US 5260070. [74] Ritchie, J. M. (1975). The xanthines. In: The Pharmacological Basis of Therapeutics. 5th ed., MacMillan, New York, pp. 367–368. [75] Europaisches, A. (1978). Degradation of caffeine by Pseudomonas alcaligenes CFR 1708 In: Coffeinum Theophyllinum, Deutscher Apotheker Verlag, Stuttgart, p. 670 and p. 1213. [76] Essig, D., Costill, D. L. and Van Handel, P. J. (1980). Effects of caffeine ingestion on utilization of muscle glycogen and lipid during leg ergometer cycling. International Journal of Sports Med, 1: pp. 86–90. [77] Spriet, L. L., MacLean, D. A., Dyck, D. J., Hultman, E., Cederblad, G. and Graham, T. E. (1992). Caffeine ingestion and muscle metabolism during prolonged exercise in humans. American Journal Physiology Endocrinology and Metabolism, 262: pp. 891–898. [78] Kalmar, J. M and Cafraelli, E. (1999). Effects of caffeine on neuromuscular function. Journal of Applied Physiology, 87: pp. 801–808. [79] Blecher, R. and Lingens, F. (1997). The metabolism of caffeine by a Pseudomonas putida strain. Hoppe-Seyler’s Z Physiol Chem, 358: pp. 807–817. [80] Srisuphan, W. and Bracken, M. B. (1986). Caffeine consumption during pregnancy and association with late spontaneous abortion. American Journal of Obstetrics Gynaecology, 155: pp. 14–20. [81] Mabbett, T. (2001). Common cause. Coffee and Cocoa-International, 28(6): pp. 27–28.
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[82] Farah, A., de Paulis, T.., Moreira, D. P., Trugo, L. C. and Martin, P. R. (2007). Chlorogenic acids and lactones in regular and waterdecaffeinated arabica coffees. Journal of Agricultural and Food Chemistry, 54(2): pp. 374–381. [83] Geyer, S. and Schulmeyr, J. (2007). Ecological and gentle technology – CO2 extraction and its use in food technology. Innovations-in-FoodTechnology, 34: pp. 44–46. [84] Sarath Babu, V. R., Patra, S., Thakur, M. S., Karanth N, G. and Varadaraj, M. C. (2005). Degradation of caffeine by Pseudomonas alcaligenes CFR 1708. Enzyme and Microbial Technology, 37: pp. 617–624. [85] Gokulakrishnan, S., Chandraraj, K., Sathyanarayana, N. and Gummadi. (2005). Microbial and enzymatic methods for the removal of caffeine. Enzyme and Microbial Technology, 37: pp. 225–232. [86] Sturdivant, S., (2001). Soluble coffee: Over a century of convenience. Tea and Coffee Trade Journal, 173 (4): pp. 25–29. [87] Bel-Rhlid, R., Kraehenbuehl, K., Lerch, K. and Aeschbach, R. (2006). Soluble coffee product, EP 1726213A1. [88] Silver, R.S. and Whalen P. E. (2007). Stabilized enzyme compositions, US 0237857A1. [89] Delgado, P. A., Vignoli, J. A., Siikaaho, M. and Franco, T. T. (2008). Sediments in coffee extracts: Composition and control by enzymatic hydrolysis. Food Chemistry, 110: pp. 168–176. [90] Boss, E. A., Rubens M. F. and Eduardo C. V. T. (2004). Freeze drying process: Real time model and optimization. Chemical Engineering and Processing, 43: pp. 1475–1485. [91] Zeller, B. L. and Kiessling, T. R. (2000). Foaming cappuccino
creamer containing gasified carbohydrate, US6129943, 10/10/2000.
[92] Nagabhushana, R. L. (1989). Speciality Indian golden mansooned coffee. Indian Coffee, 53(3): pp. 7–8. [93] Variyar, P. S., Rasheed A., Rajeev B., Zareena N. and Arun S. (2003). Flavouring components of raw monsooned arabica coffee and their changes during radiation processing. Journal of Agricultural and Food Chemistry, 51(27): pp. 7945–7950. [94] Rasheed A., Babitha T. and Bongirwar, D. R. (2003). Impact of gamma irradiation on the monsooning of coffee beans. Journal of Stored Products Research, 39(2): pp. 149–157.
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[95] Pandey, A., Soccol, C. R. and Larroche , C. (2008). Current Developments in Solid-state Fermentation, New York: Springer, pp. 356–376. [96] Borrelli, R. C., Fabrizio, E., Aurora, N., Alberto, R. and Vincenzo, F. (2004). Characterization of a new potential functional ingredient: Coffee silverskin. Journal of Agriculture and Food Chemistry, 52: pp. 1343–1338. [97] Bodmer, S. D. and Ruder, F. D. (2005). Coffee cherries’ spirit and its process of manufacture, EP 1593735A1. [98] Nakamura, T., Tokimoto, T., Tamura, T., Kawasaki, N. and Tanada, S. (2003). Decolorization of acidic dye by charcoal from coffee grounds. Journal of Health Science, 49(6): pp. 520–523. [99] Hernandez, D., Sanchez, J., Yamasaki, K. (2003). A simple procedure for preparing substrate for Pleurotus ostreatus cultivation. Bioresource Technology, 90: pp.145–150 [100] Fan, L., Pandey, A., Mohan, R. and Soccol, C. R. (2000). Use of various coffee industry residues for the cultivation of Pleurotus ostreatus in solid state fermentation. Acta-Biotechnologica, 20(1): pp. 41–52. [101] Shankaranand, V. S. and Lonsane, B. K., (1994). Coffee husk: An inexpensive substrate for production of citric acid by Aspergillus niger in a solid-state fermentation system. World Journal of Microbiology and Biotechnology, 10(2): pp. 165–168. [102] Machado, C. M. M., Oliveira, B. H., Pandey, A. and Soccol, C. R. (1999). Production of gibberllic acid from coffee byproduct. Proceedings of the Paper Presented at the 3rd International Seminar on Biotechnology in the Coffee Agro-industry, Londrina, Brazil, 39. [103] Yen, W., Wang, B., Chang L., and Duh, P. (2005). Antioxidant properties of coffee residues. Journal of Agriculture and Food Chemistry, 53: pp. 2658–2663. [104] Emille, R. B. A. and Leandro, S. (2007). Fresh coffee husks as potential sources of anthocyanins. LWT, 40: pp. 1555–1560. [105] Benoit, I., Navarro, D., Marnet, N., Rakotomanomana, N., Lesage, L., Sigoillot, J., and Aster, M. 2006. Feruloyl esterase as a tool for the release of phenolic compounds from agro-industrial by-products. Carbohydrate Research 341: pp. 1820–1827.
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5 Introduction to tea
5.1 Introduction Tea is continuing to expand in all of its forms – in grocery stores, convenience stores and on the favourite restaurant menu. Consumers are embracing Camellia sinensis for its health benefits as well as its delicious taste. In addition to increased availability of wide varieties of tea, improved brewing methods and equipments have changed the way people perceive tea [1].
5.2 Origin and history Teas have been cultivated for thousands of years in Asia. Based on the differences in morphology between Camellia sinensis (var. assamica) and Camellia sinensis (var. sinensis), botanists have long asserted a dual botanical origin for tea. Camellia sinensis (var. assamica) is native to the area from Yunnan province in China to the northern region of Myanmar and the state of Assam in India. Camellia sinensis (var. sinensis) is native to eastern and south-eastern China [2]. However, recent research questions this. The same chromosome number (2n=30) for the two varieties, easy hybridization, and various types of intermediate hybrids and spontaneous polyploids all appear to demonstrate a single place of origin for Camellia sinensis – the area including the northern part of Myanmar, Yunnan and Sichuan provinces of China [2]. Story of tea began in ancient China over 5,000 years ago (some time around 2737 BC). According to legend, the Shen Nong, an early emperor was a skilled ruler, creative scientist, and patron of the arts. His far-sighted edicts required among other things, that all drinking water be boiled as a hygienic precaution. One summer day while visiting a distant region of his realm, he and the court stopped to rest. In accordance to his ruling, the servants began to boil water for the court to drink. Dried leaves from the nearby bush fell into the boiling water, and a brown liquid was infused into the water [3]. The ever inquisitive
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and curious monarch took a sip of the brew and was pleasantly surprised by its flavour and its restorative properties. A variant of the legend tells that the emperor tested the medical properties of various herbs on him. Some were poisonous, but found tea to work as an antidote. Shen Nong is also mentioned in Lu Yu’s ‘Cha Jing’, a famous early work on the subject [4]. As a scientist, the emperor was interested in the new liquid, drank some and found it very refreshing. Therefore, according to the legend, tea was created. (This myth maintains such a practical narrative, that many mythologists believe it may relate closely to the actual events now lost in ancient history). According to a Tang dynasty legend which spread along with Buddhism, Bodhidharma and the founder of Zen school of Buddhism is based on a meditation known as “Chan”. After meditating in front of a wall for nine years, he accidentally fell asleep. He woke up in such disgust at his weakness that he cut off his eyelids and they fell to the ground and took root, growing into tea bushes. Sometimes, the second story is retold with Gautama Buddha in place of Bodhidharma. In another variant of the first mentioned myth, Gautama Buddha discovered tea when some leaves had fallen into boiling water. Whether or not these legends have any basis, tea has played a significant role in the Asian culture for centuries as a staple beverage, a curative, and as a symbol of status. It is not surprising that its discovery is ascribed to the religious or royal origins. Whether tea originated in India or China is still a matter of debate. One thing that is certain is that tea drinking was first initiated in China for medicinal purposes and later gained popularity as a nourishing beverage [4]. Tea cultivation flourished in India under the British and today India is the largest producer of tea in the world. After Europe adopted tea as its main hot beverage, China imposed restrictions on its export to the outside world The British established tea cultivation in the north-eastern parts of India. Organized cultivation spread to South India during the First World War years and later to Sri Lanka. Many features of tea cultivation and processing were standardized during this period and mechanization was undertaken to handle the ever-increasing crop to meet the global supplies. Green tea, which was normally made in China, was improved upon and Black tea manufacturing was set up which enhanced the shelf-life of tea and allowed it to be transported for longer duration to reach far flung areas. Darjeeling tea is grown in the foothills of the Himalayas and is a prized Indian black tea. This tea was marketed with vigorous campaigning by the royal family and it is still accepted among the best teas of the world [5]. Assam teas are known for their malty liquors and are promoted as the milk teas, and a
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newer process called CTC (Crush, tear and curl) was established to handle the huge bulk of the crop harvested during the rainy season. Indian teas came to be known world-wide as milk teas in many markets dominating over the lighter green teas coming out of China till then. The East India Company also had interests along the routes to India from Great Britain. The company cultivated the production of tea in India. Its products were the basis of the Boston Tea Party in Colonial America [5]. The Indian Tea Board took various programmes to protect the interests of the Indian tea industry. Genetic Inheritance (GI) registration process for establishing Darjeeling CTM (certification trade mark) was also initiated. In the 1600s, tea became popular throughout Europe and the American colonies. Since colonial days, tea has played a role in the American culture and customs. Today American school children learn about the famous Boston tea party protesting the British tea tax – one of the acts leading to the revolutionary war. During the 20th century, two major American contributions to the tea industry occurred. In 1904, iced tea was created at the World’s Fair in St. Louis, and in 1908, Thomas Sullivan of New York developed the concept of tea in a bag. Tea breaks down into three basic types: Black, Green, and Oolong. In U.S.A., over 90 percent of the tea consumed is black tea which has been fully oxidized or fermented and yields a hearty flavoured amber brew. Some of the popular black teas include English breakfast (good breakfast choice since its hearty flavour mixes well with milk), Darjeeling (a blend of Himalayan teas with a flowery bouquet suited for lunch) and Orange Pekoe (a blend of Ceylon teas that is the most widely used of the tea blends). Green tea skips the oxidizing step. It has a more delicate taste and is light green/golden in colour. Green tea, a staple in the Orient, is gaining popularity in the USA, due to recent scientific studies linking its consumption with reduced cancer risk. Oolong tea, popular in China, is partly oxidised and is a cross between black and green tea in colour and taste. While flavoured teas evolve from these three basic teas, herbal teas contain no true tea leaves. Herbal and medicinal teas are created from the flowers, berries, peels, seeds, leaves, and the roots of many different plants [3].
5.2.1 China Tea consumption spread throughout the Chinese culture, reaching into every aspect of the society. In 800 A.D., Lu Yu wrote the first definitive book on tea, the Cha Ching. This amazing man was orphaned as a child and raised by scholarly Buddhist monks in one of China’s finest monasteries. However, as a young man he rebelled against the discipline of priestly training which had made him a skilled observer. His fame as a performer increased with each year but he felt his life lacked meaning. Finally, in mid-life, he retired for 5
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years into seclusion. Drawing from his vast memory of observed events and places, he codified the various methods of tea cultivation and preparation in ancient China. The vast definitive nature of his work projected him into near sainthood within his own lifetime. Patronized by the emperor himself, his work clearly showed the Zen Buddhist philosophy to which he was exposed as a child. It was this form of tea service that Zen Buddhist missionaries would later introduce to imperial Japan [3].
5.2.2 Japan The returning Buddhist priest viz., Yeisei, who had seen the value of tea in China in enhancing religious meditation, brought the first tea seeds to Japan, and as a result he is known as the “Father of Tea” in Japan. Because of this early association, tea in Japan has always been associated with Zen Buddhism. Tea received almost instant imperial sponsorship and spread rapidly from the royal court and monasteries to the other sections of the Japanese society. Japanese tea ceremony – Tea was elevated to an art form resulting in the creation of the Japanese Tea Ceremony (“Cha-no-yu” or “the hot water for tea”). The best description of this – the Irish-Greek journalist-historian who probably wrote the complex art form ‘Lafcadio Hearn’, one of the few foreigners ever to be granted Japanese citizenship during this era. He wrote from personal observation, “The Tea ceremony requires years of training and practice to graduate in the art, yet the whole of this art, to its detail, signifies no more than the making and serving of a cup of tea. The supremely important matter is that the act be performed in the most perfect, polite, graceful and charming manner possible”. Such purity of a form of expression prompted the creation of supportive arts and services. A special form of architecture (chaseki) developed for “tea houses”, based on the duplication of the simplicity of a forest cottage. The cultural/artistic hostesses of Japan, the Geishi, began to specialize in the presentation of the tea ceremony. As more and more people became involved in the excitement surrounding the tea, the purity of the original Zen concept was lost. The tea ceremony became corrupted, boisterous, and highly embellished. “Tea Tournaments” were held among the wealthy where nobles competed among each other for rich prizes in naming various tea blends. Rewarding winners with gifts of silk, armour and jewellery was totally alien to the original Zen attitude of the ceremony. Three great Zen priests restored tea to its original place in Japanese society. Ikkyu (1394–1481), a prince who became a priest, was successful in guiding the nobles away from their corruption of the tea ceremony. Murata Shuko (1422–1502), the student of Ikkyu was very competent in re-introducing ‘The Tea ceremony’ into the Japanese society. Sen-no Rikkyu (1521–1591), a priest, set the rigid standards for the ceremony, which are intact even today
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and largely used. Rikkyu was successful in influencing the Shogun Toyotomi Hideyoshi, who became Japan’s greatest patron of the art of tea. A brilliant general, strategist, poet, artist and a unique leader facilitated the final and complete integration of tea into the pattern of Japanese life. There was complete acceptance to view tea as the ultimate gift, and warlords paused for tea before battles [3].
5.2.3 Europe While tea was at this high level of development in both Japan and China, information concerning this unknown beverage began to filter back to Europe. Earlier, caravan leaders had mentioned it but were unclear as to its service, format or appearance. One reference suggests that the leaves be boiled, salted, buttered and eaten. The first European to personally encounter tea and write about it was the Portuguese Jesuit Father Jasper de Cruz in 1560. Portugal, with her technologically advanced navy, had been successful in gaining the first right of trade with China. It was on the first commercial mission that Father de Cruz had tasted tea four years before. The Portuguese developed a trade route by which they shipped their tea to Lisbon, and then Dutch ships transported it to France, Holland, and the Baltic countries. At that time Holland was politically affiliated with Portugal. When this alliance was altered in 1602, Holland with her excellent navy, entered into full Pacific trade in her own right. When tea finally arrived in Europe, Elizabeth I had more years to live and Rembrandt was only six years old. Because of the success of the Dutch navy in the Pacific, tea became very fashionable in the Dutch capital – The Hague. This was due in part to the high cost of the tea (over $100 per pound) which immediately made it the domain of the wealthy. Slowly, as the amount of tea imported increased, the price fell as the volume of sale expanded. Initially available to the public in apothecaries along with such rare and new spices as ginger and sugar, it was available in common food shops throughout Holland by 1675. As the consumption of tea increased dramatically in the Dutch society, doctors and university authorities argued on the negative and/or positive benefits of tea known as “Tea Heretics”. The public largely ignored the scholarly debate and continued to enjoy their new beverage, though the controversy roughly lasted from 1635 to 1657. Throughout this period France and Holland led Europe in the use of tea. As the craze for oriental things swept Europe, tea became a part of the way of life. The social critic Marie de Rabutin-Chantal, the Marquise de Sevigne, makes the first mention in 1680 of adding milk to tea. During the same period, Dutch inns provided the first restaurant service of tea. Tavern owners would furnish guests with a portable tea set complete with a heating unit. The independent Dutchman would then prepare tea for himself and his friends outside in the tavern’s garden. Tea remained popular in France
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for only about fifty years, being replaced by a stronger preference for wine, chocolate and exotic coffees [3].
5.2.4 England Great Britain was the last of the three great sea-faring nations to break into the Chinese and East Indian trade routes. This was in part due to the unsteady ascension to the throne of the Stuarts and the Cromwell Ian civil war. The first samples of tea reached England between 1652 and 1654. Tea quickly proved popular enough to replace ‘Ale’ as the national drink of England whereas in Holland, it was the nobility that provided the necessary stamp of approval and so insured its acceptance. King Charles II married the Portuguese Infanta Catherine de Braganza during exile in 1662. Charles himself had grown up in the Dutch capital. As a result, both he and his Portuguese bride were confirmed tea drinkers. When the monarchy was re-established, the two rulers brought this foreign tea tradition to England with them. As early as 1600, Elizabeth I had founded the John Company for the purpose of promoting Asian trade. When Catherine de Braganza married Charles, she brought as part of her dowry the territories of Tangier and Bombay. Suddenly, the John Company had a base of operations. The John Company was granted the unbelievably wide monopoly of all the trade in east of the Cape of Good Hope and west of Cape Horn. Its powers were almost without limit and included among others the right to legally acquire territory and govern it; coin money, raise arms and build forts; form foreign alliances, declare war, conclude peace, pass laws; and try and punish lawbreakers. It was the single largest, most powerful, monopoly to ever exist in the world. In addition, its power was based on the import of tea. At the same time, the newer East India Company floundered against such competition. Appealing to Parliament for relief, the decision was made to merge the John Company and the East India Company (1773). Their re-drafted charts gave the new East India Company a complete and a total trade monopoly on all commerce in China and India. As a result, the price of tea was kept artificially high, leading to later global difficulties for the British crown. Tea mania swept across England as it had earlier spread throughout France and Holland. Tea imports rose from 40,000 pounds in 1699 to an annual average of 240,000 pounds by 1708 [3]. Prior to the introduction of tea into Britain, the English had two main meals, i.e. breakfast and dinner. Breakfast was Ale, bread, and beef. Dinner was a long, massive meal at the end of the day. It was no wonder that Anna, the Duchess of Bedford (1788–861), experienced a ‘sinking feeling’ in the late afternoon. Adopting the European tea service format, she invited friends to join her for an additional afternoon meal at five o’clock in her rooms at Belvoir Castle. The menu is centred on small cakes, bread and butter sandwiches,
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assorted sweets, and of course tea. This summer practice proved so popular that the Duchess continued it when she returned to London, sending cards to her friends asking them to join her for ‘Tea and walking in the fields’. London at that time still contained large open meadows within the city. A common pattern of service soon merged. The first pot of tea was made in the kitchen and carried to the lady of the house who waited with her invited guests, surrounded by fine porcelain from China. The hostess warmed the first pot from a second pot (usually silver) that was kept heated over a small flame. Food and tea was then passed among the guests with the main purpose of the visit being conversation [3]. Tea cuisine expanded quickly into a range of products such as wafer thin crustless sandwiches, toasted breads with jams, and regional British pastries such as scones (Scottish) and crumpets (English). At this time two distinct forms of tea services evolved, namely as high and low. ‘Low tea’ (served in the low part of the afternoon) was served in aristocratic homes of the wealthy and featured gourmet titbits rather than solid meals. The emphasis was on the presentation and conversation. ‘High tea’ or ‘Meat tea’ was the main or ‘High’ meal of the day. It was the major meal of the middle and the lower classes and consisted of mostly full dinner items such as roast beef, mashed potatoes, peas, and of course, tea [3]. Tea was the major beverage served in coffee houses, but they were so because coffee arrived in England some years before tea. These were called ‘penny universities’ exclusively for men because for a penny any man could obtain a pot of tea, a copy of the newspaper, and engage in conversation with the sharpest wits of the day. The various houses specialized in selected areas of interest—some serving attorneys, some authors and others the military. They were the forerunners of the ‘English Gentlemen’s Private Club’. One such beverage house was owned by Edward Lloyd and was favoured by ship owners, merchants, and marine insurers. That simple shop was the origin of the Lloyd’s, the worldwide insurance firm. It attempted to close the coffee houses which were made throughout the eighteenth century because of the free speeches encouraged, but such measures proved so unpopular and were always quickly revoked. Experiencing the Dutch tavern garden teas, the English developed the idea of tea gardens. Here ladies and gentlemen took their tea outdoors surrounded by entertainment such as orchestras, hidden arbours, flowered walks, bowling greens, concerts, gambling or fireworks at night. It was at such a tea garden that Lord Nelson, who defeated Napoleon by sea, met the great love of his life, Emma, known as Lady Hamilton later. Women were permitted to enter a mixed, public gathering for the first time without social criticism. British society (public) mixed here freely for the first time at these gardens, cutting across lines of class and birth [3].
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Tipping as a response to proper service developed in the tea gardens of England. Small locked wooden boxes were placed on the tables throughout the garden. Inscribed on each were the letters T.I.P.S, which stood for the sentence ‘To Insure Prompt Service’. If a guest wished the waiter to hurry (and so insure the tea arrived hot from the often-distant kitchen) he dropped a coin into the box on being seated ‘To Insure Prompt Service’. Hence, the custom of tipping servers was created.
5.2.5 Russia Imperial Russia was attempting to engage China and Japan in trade at the same time as the East Indian Company. The Russian interest in tea began as early as 1618 when the Chinese embassy in Moscow presented several chests of tea to the Czar Alexis. By 1689, the Trade Treaty of Newchinsk established a common border between Russia and China, allowing caravans to cross back and forth freely. Still, the journey was not easy. The trip was 11,000 miles long and took over sixteen months to complete. The average caravan consisted of 200– 300 camels. As a result of such factors, the cost of tea was initially prohibitive and available only to the wealthy. By the time Catherine the Great died (1796), the price had dropped to some extent, and tea was spreading throughout the Russian society. Tea was ideally suited to the Russian life – hearty, warm, and sustaining. The Samovar, adopted from the Tibetan hot pot, is a combination of bubbling hot water heater and teapot. Placed in the centre of a Russian home, it could run all day and serve up to forty cups of tea at a time. Again showing the Asian influence in the Russian culture, guests sipped their tea from glasses in silver holders, very similar to the Turkish coffee cups. The Russian have always favoured strong tea which is highly sweetened with sugar, honey, or jam. With the completion of the TransSiberian railroad in 1900, the overland caravans were abandoned. Although the revolution intervened in the flow of the Russian society, tea remained a staple throughout. Tea (along with vodka) is the national drink of the Russians today [3].
5.2.6 America By 1650, the Dutch were actively involved in trade throughout the Western world. Peter Stuyvesant brought the first tea to America and to the colonists in the Dutch settlement of New Amsterdam (later re-named New York by the English). Settlers here were confirmed tea drinkers. In addition, on acquiring the colony, the English found that the small settlement consumed more tea at that time than all of England put together [3].
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It was not until 1670 that English colonists in Boston became aware of tea, and it was not publicly available for sale until twenty years later. Tea Gardens were first opened in the New York City, already aware of tea as a former Dutch colony. The new gardens were centred on the natural springs, which the city fathers now equipped with pumps to facilitate the tea craze. The most famous of these were the tea springs at Roosevelt and Chatham (later Park Row Street). By 1720 tea was a generally accepted as a staple of trade between the colony and the mother country. It was especially a favourite of colonial women, a factor England was to base a major political decision on later. Tea trade was centred in Boston, New York, and Philadelphia, future centres of American rebellion. As tea was heavily taxed, even at this early date, contraband tea was smuggled into the colonies by the independent minded American merchants from ports far away, and adopted herbal teas from the Indians. The directors of the ‘then’ John Company (to merge with the East India Company later) fumed as they saw their profits diminish and so they pressured the Parliament to take action [3].
Tea and the American Revolution England had recently completed the French and the Indian war fought, from England’s point of view, to free the colony from French influence and stabilize trade. It was the feeling of Parliament that as a result, it was not unreasonable that the colonists shoulder the majority of the cost. After all the war had been fought for their benefit, Charles Townshend presented the first tax measures, which today are known by his name. They imposed a higher tax on newspapers (which they considered far too outspoken in America), tavern licenses (too much free speech there), legal documents, marriage licenses, and docking papers. The colonists rebelled against taxes imposed upon them without their consent and which were so repressive. New and heavier taxes were levelled by the Parliament for such rebellion. Among these was the tea tax in June 1767 that was to become the watershed of America’s desire for freedom. Townshend died three months later due to fever and he never knew that his tax measures helped create a free nation. The colonists rebelled and openly purchased imported tea, largely Dutch in origin. The John Company, already in deep financial trouble saw its profits fall even further. By 1773, the John Company merged with the East India Company for structural stability and pleaded with the Crown for assistance. The new Lord of the Treasury, Lord North, as a response to this pressure, granted to the new Company permission to sell directly to the colonists, bypassing the colonial merchants and pocketing the difference. In plotting this strategy, England was counting on the well-known passion among American women for tea to force consumption and it was a major miscalculation. Throughout
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the colonies, women pledged publicly at meeting and in newspapers not to drink English sold tea until their free rights, and those of their merchant husbands, were restored [3].
The Boston Tea Party By December 16, events had deteriorated enough that the men of Boston, dressed as Indians (remember the original justification for taxation had been the expense of the French and Indian war) threw hundreds of pounds of tea into the harbour. Such leading citizens as Samuel Adams and John Hancock took part. England had had enough. In retaliation, the port of Boston was closed and the city occupied by royal troops. The colonial leaders met and revolution declared. The trade continued in the Orient, though concerned over developments in America, English tea interests still centred on the product’s source—the Orient. There the trading of tea had become a way of life, developing its own language known as Pidgin English. Created solely to facilitate commerce, the language was composed of English, Portuguese, and Indian words all pronounced in Chinese. Indeed, the word pidgin is a corrupted form of the Chinese word for ‘does business’. So dominant was the tea culture within the English speaking cultures that many of these words came to hold a permanent place in our language. Mandarin (from the Portuguese ‘mandar’ meaning ‘to order’) – the court official empowered by the emperor to trade tea. Cash (from the Portuguese ‘caixa’ meaning ‘case or money box’) – the currency of tea transactions; Caddy (from the Chinese word ‘one pound weight’) – the standard tea trade container; Chow (from the Indian word ‘food cargo’) – slang for food.
The Opium Wars Not only was language a problem, but also was the currency. Vast sums of money were spent on tea. Transportation of large amounts of currency out of England would have been impossible to transport safely half way around the world and the country would have collapsed financially. With plantations in newly occupied India, the John Company saw a solution. In India, they could grow the inexpensive crop of opium and use it as a means of exchange. Because of its addictive nature, the demand for the drug would be long, insuring an unending market. Chinese emperors tried to maintain the forced distance between the Chinese people and the devils. However, disorder in the Chinese culture and foreign military might have prevented it. The Opium Wars broke out with the English ready to go to war for free trade (their right to sell opium). By 1842 England had gained enough military advantages to enable her to sell opium in China undisturbed until 1908 [3].
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America began direct trade with China soon after the revolution was over in 1789. America’s newer, faster, clipper ships out-sailed the slower, heavier English tea wagons that had dominated the trade until then. This forced the English navy to update their fleet, a fact America would have to address in the War of 1812. The new American ships established sailing records that still stand for speed and distance. John Jacob Astor began his tea trading in 1800. He required a minimum profit of 50% on each venture and often made 100%. Stephen Girard of Philadelphia was known as the gentle tea merchant. His critical loans to the young and weak American government enabled the nation to re-arm for the war of 1812. The orphanage founded by him still perpetuates his good name. Thomas Perkins was from one of Boston’s oldest sailing families. The trust of the Chinese in him as a gentleman of his word enabled him to conduct enormous transactions half way around the world without a single written contract. His word and his handshake was enough – so great was his honour in the eyes of the Chinese. It is to their everlasting credit that none of these men ever paid for tea with opium. America was able to break the English tea monopoly because its ships were faster and it paid in gold. By the mid-1800 the world was involved in a global clipper race as nations competed with each other to claim the fastest ships. England and America were the leading rivals. Each year the tall ships would race from China to the tea exchange in London to bring in the first tea for auction. Though beginning half way around the world, the mastery of the crews was such that the great ships often raced up the Thames separated by only by minutes. However, by 1871 the newer steamships began to replace these great ships [3].
5.2.7 Global tea plantations The Scottish botanist Robert Fortune, who spoke fluent Chinese, was able to sneak into mainland China the first year after the opium war. He obtained some of the closely guarded tea seeds and made notes on tea cultivation. With the support from the Crown, various experiments in growing tea in India were attempted. Many of these failed due to bad soil selection and incorrect planting techniques. However, through each failure, the technology was perfected. Finally, after years of trial and error, fortunes made and lost the English tea plantations in India and other parts of Asia flourished. The great English tea marketing companies were founded and production mechanized as the world industrialized in the late 1880s.
5.2.8 Iced tea and teabags America stabilized her government, strengthened her economy, and expanded her borders and interests. By 1904, the United States was ready for the world
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to see her development at the St. Louis world’s fair. Trade exhibitors from around the world brought their products to America’s first world’s fair. One such merchant Richard Blechynden, a tea plantation owner, had planned to give away free samples of hot tea to fair visitors. However, when a heat wave hit no one was interested. To save his investment of time and travel, he dumped a load of ice into the brewed tea and served the first iced tea. It was the hit of the fair. Four years later, Thomas Sullivan of New York developed the concept of bagged tea. As a tea merchant, he carefully wrapped each sample delivered to restaurants for their consideration. He recognized a natural marketing opportunity when he realized the restaurants were brewing the samples in the bags to avoid the mess of tea leaves in the kitchens.
5.2.9 Tea rooms, tea courts and tea dances Beginning in the late 1880s in both America and England, fine hotels began to offer tea service in tea rooms and tea courts. In the late afternoon, Victorian ladies (and their gentlemen friends) could meet for tea and conversation. Many of these tea services became the hallmark of the elegance of the hotel, such as the tea services at the Ritz (Boston) and the Plaza (New York). By 1910, hotels began to host afternoon tea dances. These swept the United States and England [3].
5.2.10 Vari (Tea) – English breakfast The prototype of this most popular of all teas was developed over a hundred years ago by the Scottish tea master Drysdale in Edinburgh. It was marketed simply as breakfast tea. It became popular in England, as Queen Victoria created the craze for Scottish (the summer home of Victoria) things. Teashops in London, however, changed the name and marketed it as English breakfast tea. It is a blend of fine black teas, often including some Keemun tea. Many tea authorities suggest that the Keemun tea blended with milk creates a bouquet that reminds people of toast hot from the oven and maybe the original source for the name. It should be offered with milk or lemon. (One never serves lemon to a guest if they request milk as it would curdle the milk.) It may also be used to brew iced tea.
5.2.11 Irish breakfast The Irish have always been great tea drinkers, and they drink their tea brewed very strong. In fact, there is a common tea saying among the Irish is that “a proper cup of tea should be strong enough for a mouse to trot on”. Along the same line, the Irish believed there were only three types of tea fit to drink. The first and best of quality was in China. The second best was sent directly
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to Ireland. The third and lowest in quality was sent to the English. Irish tea is usually drunk only in the morning because of its robust flavour, except for the Irish who drink it all day. Usually it is blended with an Assam tea base. Due to its taste, it is served with lots of sugar and milk.
5.2.12 Tea – Commercial varieties Caravan, this excellent tea was created in imperial Russia from the teas brought overland by camel from Asia. Because the trade route was dangerous and supplies unsteady, Russian tea merchants blended the varying incoming tea cargoes, selling a blend rather than a single tea form. It was usually a combination of black teas from China and India. Like the Irish, the Russian favoured this tea all day long. Earl Grey (1764–1845), though he was prime minister of England under William IV, is better remembered for the tea named after him. Tea legends say a Chinese mandarin gave the blend to him seeking to influence trade relations. A smoky tea with a hint of sweetness to it and served plain is the second most popular tea in the world today. It is generally a blend of black teas and bergamot oil. Black teas and Oolong Darjeeling refers to the tea grown in the mountain area of India. The mountain altitude and gentle misty rains of the region produce a unique full-bodied but a light flavoured, with a subtly lingering, aroma reminiscent of muscatel and highest grade. Reserved for afternoon use, it is traditionally offered to guests with lemon and without milk. Oolong, the elegant tea is sometimes known as the champagne of teas. Originally grown in the Fukien province of China, it was first imported to England in 1869 by John Dodd. Today, the highest grade Oolongs (Formosa Oolongs) are grown in Taiwan. A cross between green and black teas, it is fermented to achieve a delicious fruity taste. It is perfect for afternoon use with cucumber sandwiches and madeleine. Green tea makes up only ten percent of the world’s produced tea. The Japanese tea service (in which green tea is used) is an art. The serving of a full Japanese tea service would be beyond the ability of most properties and as a result, should not be attempted. Green tea is generally not a part of the afternoon tea tradition as appropriate to the hotel use. Keemun China Teas is the most famous of China’s black teas. Because of its subtle and complex nature, it is considered the burgundy of teas. It is a mellow tea that will stand alone as well as support sugar and /or milk, because of its wine-like quality [3] Today the bush tea is known as Camellia sinensis (L.) O. Kuntze of which there are two varieties: var. sinensis and var. assamica. In 1690, Kaempfer, a German medical doctor cum botanist who came to Japan from Holland and
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observed the habit of tea drinking among the people, named the bush Thea. In 1753, the famed botanist Linne gave the name of Camellia sinensis, changing its original naming of Thea sinensis. Since, the nomenclature of tea bush has been confused between these two names, in 1958 a British botanist Sealy classified all plants in Genus Camellia and tea was given the name it has today [6]. Tea is cultivated successfully in many different countries of the world and consumed in almost every part of the world, but the association of tea with China remains strong. Today the birthplace of tea is assumed to be southwestern China, centred in Yunnan district [7]. There are two approaches in tracing the history of tea usage, viz., anthropological or archival. Chinese legend claimed that the tea consumption goes back as far as 2737 BC. The first credible documentary reference on tea was made in 59 BC in a servant’s contract which stated that his duties included the making of tea and going to the city to buy it. Lu Yu, who described the botany, cultivation and processing of tea, as well as the utensils and proper way of drinking tea, etc., in his writings in detail, Tea classics or tea sutra has been the bible for people involved with tea ever since [8].
5.3 Tea production 5.3.1 World scenario of production and trade
Figure 5.1 Major tea producing countries [9]
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China and India are the two largest producers as well as consumers of tea. In global production, China’s contribution is 31% while that of India is 25% (Figure 5.1). The contribution of both in global tea business is 18% and 11% respectively. Other countries like Kenya, Sri Lanka, Vietnam and Indonesia contribute 25% of the world tea and control 50% of the world trade [9]. Food and Agriculture Organization (FAO) reports that the market for tea industry is expected to grow at 3% per annum. With the removal of quantitative restrictions (QRs) following World Trade Organization (WTO) regulations coming into force, the consumption is going to increase in developing countries. During the last four decades, Kenya has increased tea production by 25 times. Chinese tea production has witnessed a cumulative growth rate of 4.6%. The production growth rates have been slower in India and Sri Lanka at 2.3% and 0.9% respectively, during the same period. The area under cultivation has gone up by 33% in India and ten times in Kenya during the last 40 years [10].
5.3.2 Indian scenario Indian is one of the largest producer and consumer of tea in the world. In India, tea is grown in 15 states. Among these states, the major share is by Assam (50%), followed by West Bengal (24%), Tamil Nadu (17%) and Kerala (7%), others account for remaining 2%. India accounts for 20% of the total area under tea cultivation in the world, 25% of global tea production, 22% of world tea consumption and 11% of total tea exports [9]. India also leads in global research and development in tea industry. India is the largest manufacturer and exporter of tea machinery. The annual per capita consumption in India is low at 800 g compared to other countries like Pakistan (950 g), Sri Lanka (1.2 kg), UK (2.3 kg) and Bangladesh (1.2 kg). The annual tea production has been above 900 million kg for the last four years (Table 5.1). The tea production grew at an average annual rate of 2.3% during last 4 decades and 1.4% in the last decade. But over last few years the consumption growth has slowed down, this coupled with falling exports (Table 5.2) has led to surplus supply, and so the prices are declining in the market. It has reflected in the statistics of auction centres [10]. Table 5.1 Production of tea in India from 2001 to 2008 (in million kg) [11]
State
Assam West Bengal Tamil Nadu
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2001
2002
2003
2004
2005
2006
2007
2008
132
143
167
163
159
164
161
171
454 187
433 188
435 201
436 215
487 218
502 237
512 236
487 233
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Kerala India*
65 854
58 838
58 878
62 893
63 946
59 982
560 987
70 981
*Includes other states also Table 5.2 Tea exports from India during 2006–2008 [12]
Year Quantity (in million kg) Value (in crores) Unit price (Rs/kg)
2006 218.73
2007 178.75
2008 203.12
2006.53 91.73
1810.11 101.26
2392.91 117.81
5.4 Botanical and taxonomical characteristics Tea as a commercial crop includes several species within the Genus Camellia in the family Theaceae. The Genus Camellia includes 82
species, which are mostly indigenous to the highlands of South-East Asia [6]. The systematic position of the tea plant is given in Table 5.3. Table 5.3 Systematic taxonomical position of tea
Division
Angiospermae
Class
Dicotyledones
Order
Parietales
Family
Theaceae
Genus
Camellia
Species
sinensis
Tea is commonly accepted as Camellia sinensis (L) O. Kuntze, irrespective of any variation in the characteristics. This is normally a diploid (2n=30 chromosomes) but polyploids occur. Taxonomically, four basic varieties of the tea plant are recognized commercially – China type (Camellia sinensis var. sinensis), Assam type (Camellia sinensis var. assamica), Cambodia type (Camellia sinensis var. lasiocalyx), and the hybrid of China and Assam types [13]. Based on leaf pose and growth habitat, two intra specific forms of C. sinensis (L.) are China variety, Camellia sinensis var. sinensis (L.) and Assam variety, Camellia sinensis var. assamica (Kitamura). The characteristic features that separate these two varieties are presented in Table 5.4 [6, 14]. Table 5.4 Characteristics of two tea varieties
Variety
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Sub-variety
Growth habitat
Leaf features
Leaf pose
Leaf angle
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China Camellia sinensis var. sinensis (L.)
Camellia sinensis var. sinensis f. paviflora (Miq) Sealy Camellia sinensis var. sinensis f. macrophylla Sieb (Kitamura)
Assam Camellia sinensis var. assamica (Kitamura)
_
Dwarf, slow growing, shrub like
Small, erect narrow, dark green
Erectophile
<50 degree
Tall, quick growing tree
Large, horizontal, broad, mostly non-serrated, light green
Planophile
>70 degree
5.4.1 General characteristics Tea plant is an evergreen perennial shrub most often reaching a height of 30 ft. The leaves are of small length 5.5–6.1 cm, by width 2.2–2.4 cm, alternate, evergreen, elliptical, acuminate, serrated margins, glabrous sheet with pubescent below surface and become dark green and leathery on maturity. The flower buds originate either singly or in clusters from the side buds, flowers are white with 5 to 7 leathery sepals and petals. Fruits are glabrous, brownish green in colour, and trilobate with 1–3 seeds.
5.5 Cultivation practices 5.5.1 Climatic requirements The temperature in the range of 18–30°C is optimal for shoot growth. The minimum air temperature for shoot growth appears to be 13–14°C. Soil temperature is also important and optimum growth occurs between 20°C and 25°C [15].
5.5.2 Soil type Tea is grown in a wide variety of soil types, ranging from alluvial soils, drained soils and peat in the soil derived from volcanic ash. Growth of tea is favoured by acidic conditions, a pH value of 5.0–5.6 being considered optimum. Tea will not grow in soils with a pH value as low as 4.0 but soils with a pH value
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only marginally above 5.6 are considered unsuitable. Soils with pH values above 6.5 are not amenable to treatment and cannot be used for tea cultivation [15].
5.5.3 Land preparation Land clearance is required for tea cultivation as per the rules of different countries. The accumulation of large quantities of decaying vegetation can lead to significant rise in pH values and cleared material should be removed from the site. Burning is not recommended, as ash will also raise the soil’s pH value. Soil should be mixed well and proper drainage should be provided [15].
5.5.4 Seed Tea propagation is done by sowing seeds directly into the field and also by vegetative propagated clones. The quality of seeds within a single batch can vary considerably and a simple grading by floatation is applied immediately before planting. Seeds that remain floating after 72 h are unsuitable for use. Seeds require cracking before use to permit water entry and ensure a high and even rate of germination. Nursery beds require good quality of top soil. Shade is necessary for young plants, the shade density being progressively reduced until the plant is exposed to full sunlight and fertilizer is generally applied as foliar spray. In the field, bushes should be planted as closely as possible, to give complete ground coverage without over-crowding. Optimum spacing is dictated by the branching patterns of clones. Tea plants are most commonly planted as hedges, plant with the hedges are usually planted 0.6–0.8 m apart, with a space of about 1.2 m between the hedges [15].
5.5.5 Hoeing Hoeing is an operation in which soil around young plants is frequently loosened to a depth of 3 inches for a distance of 12 inches around. The hoeing helps to cut down the weeds and also helps in better aeration [8].
5.5.6 Irrigation Irrigation is an absolute necessity in countries such as Zimbabwe, where annual rainfall may be less than 700 mm. Irrigation should be considered where regular dry seasons of three to six months may be expected, where potential soil water deficits 300 mm annually. Evaporative loss of water in a whole year from many tea areas exceeds 1270 mm, which is believed to be a minimum annual requirement of water by tea plant [16].
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5.5.7 Fertilizer requirements The requirements of major nutrients like nitrogen, phosphorus and potassium for the tea plant are as follows, nitrogen at the rate of 200–300 kg, phosphorus ranges from 75 to 100 kg and potassium application ranges from 100 to150 kg per hectare [16].
5.5.8 Shade trees and windbreaks The role of shade trees and shelter in tea husbandry has been the subject of discussion for many years. The finding that yields were often higher without shade led to the removal of shade trees. Shade trees were, however, valuable in some low altitude tree growing areas, particularly Assam, due to the maintenance of the air temperature with in the optimum range. Leaf fall from shade trees can also improve the nutrient status and physical conditions of soil. Trees grown under shade will be blacker due to more chlorophyll but has lower polyphenol content, more of amino acids and caffeine content. The major types of tree grown for shade in tea plantations include: Albizzia stipulate, A. procera; Dalbergia assamica and Derris Robusta in north India, and Eryrhrina lithosperma, Dalbergia sisso, Albizzia lebbeck and Grevillea Robusta in south India. High winds have an adverse effect on tree through physical damage, reduction of leaf temperature and increased transpiration rate. Belts of shelter can transfer these effects. The shelter trees can reduce yield through competition for nutrients and water and through shading. Belts of shelter trees are usually justified only where very high wind is common. Apart from all these, mulching and top dressing are done at regular intervals.
5.5.9 Pest and diseases Major pests of tea includes tea mosquito bug (Helopeltis theavora), red spider mite, pink mite, green fly, thrips, aphides, crickets, tea mealy bugs, Leafy feeding caterpillar (Homona coffearia), etc. Major diseases of leaves, shoot and root are mentioned in Table 5.5. Table 5.5 Diseases of tea plant
Plant part Leaves
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Disease
Blister blight Grey blight Brown blight Anthacnose Eye spot Brown spot
Causative organism
Exobasidium vexans Pestalotia theae Colletotrichum camilleae Colletotrichum thea-sinensis Pseudocercospora ocellata Calonectria spp.
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Bacterial blight Stem canker Armillaria rot Charcoal rot Red rot Brown root Violet root
Pseudomonas syringe pv. theae Phomopsis theae Armillaria mellea Ustulina deusta Poria hypolateritia Fomes noxius Sphaerostillbe repens
5.5.10 Harvesting The harvesting is done manually by employing labourers. This is expensive compared to mechanical harvesting. Irrespective whether manual and/ or mechanical plucking is used, it is usual to maintain a flat plucking table parallel to ground. Manual labourers are able to maintain the correct level by the use of a light pole, while wheeled harvesting equipment maintains a preset level. Maintaining a flat plucking table is, however, difficult where held mechanical sheers hand is used. It is important to stress that freshly harvested tea shoots are perishable. These can be bruised or broken easily, there by premature triggering the fermentation process and causing deterioration in quality. To avoid these problems, it is necessary to begin the manufacture process as quickly as possible after harvest. The most popular factor is coarseness of harvest (leaf number per shoot). The polyphenol and caffeine content is highest on dry weight basis in the youngest leaf of a given shoot. The content drops with each older leaf moving down the stem. It is very important that the harvested shoots are uniform. Without uniformity at the front end, it is very difficult to manage all the later steps. In north India the method of plucking involves two leaves and a bud (Figure 5.2). In south India however tea is plucked year round and the practice is to pluck two leaves and a bud, leaving the fully developed leaves on the bush exclusive of sheath leaf, which is called as Jannum or fish leaf. From the second flush until the end of July one fully matured leaf is left beside the fish leaf. From the first of August, close plucking is practiced. The interval between each pluck is 7–9 days. Plucking may be coarse or fine. Fine plucking involves plucking two leaves and a bud. Coarse plucking involves plucking 3 or 4 leaves [15].
5.5.11 Pruning Pruning is a necessary evil for tea plants. Shaping of new bushes is to develop new surface with new shoots and it is achieved by pruning and bending branches down and pegging into position, is commonly referred as bringing into bearing. After the bush is brought into bearing but before regular plucking has commenced, a procedure commonly known as tipping is applied. This is
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intended to level the plucking surface and to increase the number of plucking points. Pruning is required to remove all stems above the basic frame of the bush [16]. The frequency of pruning i.e., the pruning cycle, varies from 1 to 4 years. For economic reasons, it is desirable to prune during the dry seasons when yield is low. Usually, pruning is done at a height of 8 to 15 inches from ground level. A very light pruning is sometimes possible as an alternative to full maintenance pruning. Only the over crowded upper layer is removed and bushes are out of production for only a short period. On the other hand, light pruning cannot maintain a bush in a satisfactory condition indefinitely, so it is necessary to prune very heavily below the lowest normal prune. This is variously referred as collar pruning. Heavy pruning is done once in ten years. Pruning helps to get good growth in subsequent season [16].
Figure 5.2 Tea garden; two leaves and a bud
5.5.12 Adulterants Most common adulterants are the leaves of other plants. Commonly used leaves are beech (Fagus sylvatica), hawthorn (Crataegus oxycantha), sloe (Prunus spinosa), oak, poplar, maple and other trees. Another formerly wide spread adulteration was the addition of spent tea leaves. These spent teas were impregnated with catechins, caramel, campeachy wood, indigo, berlin blue, curcuma, humus, graphite etc. Adulteration can be detected by microscopic examinations and can often be discovered by chemical means, particularly by the estimation of hot water extract, tannin and total water-soluble ash [8].
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6 Types of tea and processing
6.1 Introduction Processed tea can be classified on the basis of established quality and processing methods. There are six types of processed teas – green, green brick, yellow, white, oolong and black tea. This categorization is based on the degree of fermentation and oxidation of simple polyphenols present in tea leaves. Green and yellow teas are unfermented. Polyphenols are hardly oxidized in green tea, but these are subjected to non-enzymatic oxidation in yellow tea. White, oolong (red) and black teas are fermented with white having least fermentation and black having the most. All these have distinct flavours and qualities that are determined by the degree of oxidation of polyphenols, whether enzymatic or non-enzymatic [17].
6.2 Green tea Green tea (Figure 6.1) is widely preferred in Japan and China and is produced from var. sinensis. With respect to demand in the world market, green tea is next to black tea. There are two types of green tea manufacturing process – Japanese method (Sen-cha process) and Chinese method (Pan-fried green tea).
6.2.1 Sen-cha process Sen-cha was developed in the 18th century in the Uji area – the prosperous area traditionally associated with producing the ceremony tea. Before Sen-cha was developed, a primitive tea was made by sun drying after steaming or parching the leaves. The process (Figure 6.2) consists of a series of controlled heating and curing operations. Plucked leaves are steamed for 45–60 s, then cured and dried in hot air at 90–110°C for 40–50 min. This primary drying and rolling process reduces the moisture from 76% to about 50%. The leaves are further rolled for 15 min without heat and then pressed and dried for 30–40 min in hot air at 50–60°C. This secondary drying reduces the moisture content of the
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tea to about 30%. A further curing is followed by third drying stage, in which the tea leaves are dried directly on a hot pan at 80–90°C and twisted for 40 min under pressing and rolling by a curing-hand mounted on the pan. Finally, the tea leaves are dried at 80°C, until moisture content of 6% is achieved. And then a fine needle-like form of Sen-cha tea is prepared [15].
Figure 6.1 Green tea
Plucking
Transportation
Steaming (Sen-cha)
Pan-fried (Kamairi-cha)
Drying and machine rolling
Final drying
Packaging Figure 6.2 Manufacture of green tea
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6.2.2 Pan-fried process (Kamairi-cha) Pan-fried tea had become popular in China by the 14th century or during the Ming Dynasty era. Kamairi-cha production differs from Sen-cha production by omitting the steaming operation and by using a higher temperature in the first firing stage (Figure 6.2). The manufacturing process for pan-fried tea is as follows: Fresh leaves are fried in a pan at 250–300°C for 10–15 min with agitation, 4–5 times per minute, to protect the leaves from burning. During frying, the greenish odour note is evaporated and the typical pan-fried aroma is developed. The leaves are manipulated to one of the three shapes characteristic of Chinese green tea during 10–15 min in a roller, and then dried at 100–150°C in a pan. The products are the gun type of tea which is ball-like – the chun-mee and sow-mee types which have a fine, twisted form, and the pan-fired type which has a flat form and has been polished to a pale white colour [15].
6.3 Green brick tea Green brick tea is an excellent beverage having a high demand in Mongolia, China and Central Asian Republics of the U.S.S.R. The manufacture of green brick tea differs from that of other teas in both raw materials and the processing procedures. In contrast to other teas, green brick tea is not only a flavoured product but also consumed as a soup prepared from water or milk supplemented with butter, mutton fat and salt. Green brick tea is produced from the coarse tea leaves and wastes obtained from autumn and spring pruning of tea plantations. Green brick tea production technology includes two independent steps:
(a) Preparation of half-finished lao-cha (b) Pressing into green brick tea
In Chinese lao-cha means old tea. Lao-cha is produced from November to February / March from raw material of two kinds – one for coating and other for inner portion of brick tea. The raw materials used for making the coating portion should be of higher quality than that used to obtain the inner portion. The inner material is made mainly of coarse shoots having up to 12 leaves on green stalk and may also include green and brown stalks. In general, green brick tea contains 70% leaves and 30% lignified stalk. There are two methods of lao-cha production technology. An ancient Chinese method dates back to old times and other method developed at Bakh Institute of Biochemistry, U.S.S.R. Academy of Sciences [18].
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The Chinese method requires many technological operations to be carried out for 16–20 days. The first step is raw tea roasting. The roasted tea is allowed to stand for 2–3 h in small stacks and then is cooled, rolled and dried to reduce moisture to 18–20%. The dried lao-cha is kept in large stacks to assure the basic fermentation. The time when the temperature reaches 55–65°C, is regarded as the end of fermentation process. To achieve uniform fermentation throughout the entire tea bulk, the inner portion is removed and changed to the outside. After 5 days, the temperature of inner portion of the stalk rises again to 50°C. This indicates termination of fermentation process. The stalk is then taken apart, loosened, cooled and exposed to final frying. Later the tea is fried at 85–90°C to reduce moisture content 8–9%. This is the end of lao-cha process. The lao-cha fermentation process takes 20 days. The Chinese method has no scientific support. As indicated above, the fermentation that induces selfwarming and formation of the quality was supposed to be a microbiological process. In an alternate method, roasting, at high temperature, rolling and thermal treatments are performed in specially designed boxes, and firing in regular tea firing furnaces. This technological scheme is used for the production of lao-cha [18]. Pressing 400 g of the coating material and 1600 g of the inner material are exposed to steaming and pressing. As a result, tea bricks of 2000g are produced. Half of the coating material is used to cover the lower layer and the other half for the upper layer. The first stage in green brick production is laocha steaming. Each portion of the coating and inner material is wrapped up in a cloth napkin and exposed to water vapour at 6–7 atm for 2 min at 95–100°C. As a result, the lao-cha bulk loosens and can be readily pressed. The lao-cha bulk thus prepared is placed into a machine in a certain order. At first half, 200g of coating material, then the inner material 1600 g and finally remaining half (200 g) of the coating material are placed. Then the press machine filled with well-arranged lao-cha is moved onto the hydraulic press that presses brick tea at a pressure of 100–110 atm. The press machine is transferred onto the conveyor line where it moves slowly. Tea bricks are allowed to stand in the press machine for 60min in order to retain a standard shape, strength and to cool down. Additional drying is needed because in steaming the moisture content of lao-cha increases. The drying is carried out in the drying chamber at 34–36°C with a relative humidity of 50–55%. The drying process is applied for 15–20 days to reduce the moisture content to 11% at the most. Finally, the green brick tea is wrapped up into paper and sixteen bricks are packed in each standard plywood box. The bricks are of following size – 350 mm long, 160 mm wide and 31–33 mm thick [19]. The investigation at Bakh Institute of Biochemistry, U.S.S.R. Academy of Sciences, disproved the theory. The self-warming of lao-cha in stacks was
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found to be a physico-chemical process, and developing under the influence of increased temperature and humidity. Exposure of the sterile raw tea to 55– 65°C produced lao-cha of high quality. Eventually, an alternate method of lao-cha production was developed; the method shortened the technological procedures from 20 days to 10–20 h, and increased markedly the manufactured tea quality. This method involves three steps in the lao-cha manufacture – (i) roasting and high temperature rolling; (ii) thermal treatment; (iii) firing.
6.4 Yellow tea Yellow tea (Figure 6.3) occupies intermediate position between the black and green teas, and is close to green teas [18]. The yellow tea infusion is of a bright colour than that of green tea. Yellow tea is pleasant refreshing beverage. It has a milder taste and strong aroma than green tea. Yellow tea is extremely popular in China and few other countries. In China, it is called blue tea occasionally, because the boiled tea leaf is dark blue and the dry tea has a bluish shade. Yellow tea produced from second and third leaves and tender shoots of tea plant [20]. A description of the yellow tea production technology is described in the following steps:
6.4.1 Withering Withering is the first step in the yellow tea production. It is important to apply uniform withering to the tender part of the shoot and the bud. The first leaf should not be withered to the same extent as that of the third leaf and the stalk. The withering is performed to reduce the moisture to 62–64%.
6.4.2 Roasting and rolling Following withering, the tea material is roasted in boilers at 166–176°C for 2–3 min with continuous stirring. The withered and roasted tea leaves are allowed to cool down for 30–60 min. At this stage, the leaf looses its grassy odour and acquires pleasant aroma. The leaf is exposed to high temperature rolling for 50–60 min.
6.4.3 Firing The first step is performed at 90–95°C to assure moisture content of 5–7% and subsequent thermal treatment decreases the moisture content to 4–5%. In the course of yellow tea manufacturing, tannins, volatile compounds and other constituents undergo chemical transformations. For instance, the content of tannin decreases by 1.2% and that of volatile aldehyde increases from 1.46 to
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7.01 mg per 100 g dry tea. These changes develop primarily at the stages of withering, roasting and rolling [21]. Yellow tea manufacture does not include fermentation. Nevertheless, in withering, roasting, rolling and frying, a portion of tannin undergoes oxidation and therefore, dry yellow tea is darker than green tea. Its infusion looks like that of green tea but has an organic shade. The taste of yellow tea differs from that of green tea. The aroma of yellow tea is stronger and superior than that of green tea. During 1970s, yellow tea production was initiated in Georgia [19]. The content of extractives of tea in the Georgian yellow tea is 48.4% and in Chinese 46.3%. The total amount of tannin is 21.5% and 24.5% whereas the content of catechins is 16.0% and 19.8%, in Georgian and Chinese teas respectively. The chromatographic separation of tannin from the Georgian and Chinese yellow tea has demonstrated that the qualitative composition of catechin is identical [18].
Figure 6.3 Yellow tea
6.5 White tea White tea is produced in the Fujian province and accounts for less than 0.1% of the total tea production. It is a fermented tea peculiar to China and originated before the 16th century. Raw material consists of fresh leaves from the first plucking of spring tea with a moderate content of polyphenol. These are large and medium leaves with profuse hair. Sprouting buds are used for the processing of the bud white tea group while the sprouting bud with two to three fresh leaves for other white tea groups. Brief description of the manufacturing process is described below.
6.5.1 Withering Tea leaves are spread on a mat made of bamboo. The leaves are overlapped so that there are no spaces between them. On cloudless days, the leaves are dried
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in the sun for several hours and then moved indoors. The procedure is repeated for 2–3 days. The leaves are withered also by spreading in a well-ventilated room at a temperature of 29–30°C and a relative humidity of 65–70%, till the buds contain about 30% moisture and leaves about 13%.
6.5.2 Rolling Rolling is done at once before the temperature drops. Rolling is carried out 2–3 times with a suitable pressure.
6.5.3 Firing Bud tea is fired at a temperature of 40–45°C for 20–30 minutes. Leaf tea is fired at a temperature of 70–80°C for 10–15 min until the leaves contain about 6% moisture. The material is stirred gently for uniform firing [17].
6.6 Oolong tea Oolong tea (Figure 6.4) is a semi-fermented tea with special flavour and quality. It is originated in the Fujian province. China derives its name from the Chinese word Wulong, literally means black dragon and symbolizing authority and nobility. The creation time of oolong tea can be traced back to 1855. By combining green and black tea processing procedures, tea farmers in Fujian province invented a new type called oolong tea. Oolong teas are recognized such as wuyi rock tea, red robe tea, iron budha tea, rougui tea, golden key tea etc. Oolong teas are widely consumed in mainland China, Taiwan, Japan, the United Kingdom, America and South-East Asian countries. The processing steps in the manufacture of oolong tea are described below [22].
6.6.1 Plucking A fully matured shoot (a dormant bud and bhanji with 2–3 leaves) is plucked for oolong tea manufacture [22].
6.6.2 Withering Unlike black tea, a special name called Zuoquing, literal meaning green making, is given to withered stage of oolong tea processing. This stage is done in the open air by sunlight. The plucked leaves are spread on bamboo mats (0.5 kg/m2) and exposed to sunlight and the leaves are turned 2–3 times. When the leaves become soft and the total moisture loss reaches 10–20%, the leaves are moved indoor for the next step [22].
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6.6.3 Rotating Rotating causes friction between leaves and disrupts the leaf cells. Most famous or high-grade oolong teas are rotated by hand using a bamboo tray. A special machine designed for rotating withered leaves is now widely used for common oolong tea. Rotating is done indoors at a temperature of 20–25°C and at a relative humidity of 75–85%. The rotating of leaves causes damage to leaf edges and fermentation takes place. The leaf edges turn red at first, gradually spreading to the inner part of leaves. Rotating step lasts for 6–8 h and occurs 5–6 times [22].
6.6.4 Fixing The rotated leaves are immediately subjected to high temperature fixing in order to stop fermentation at the edge and to deactivate the enzyme activity in the green part. The fixing involves pan heating for 3–7 min at 180–220°C [22].
6.6.5 Rolling Rolling is done at once before the temperature drops. Rolling is carried out 2–3 times with suitable pressure. The cell breakage degree is lighter than green or black tea, i.e. about 30%. This is the reason why oolong tea can be brewed repeatedly [22].
Figure 6.4 Oolong tea
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6.6.6 Drying Drying is usually done in two stages. In the first stage, leaves are spread thinly on a bamboo basket or the drying machine and dried quickly at high temperatures. In the second stage lower temperature is used [22].
6.7 Black tea The basic principle of manufacturing black tea (Figure 6.5) is the control of colour change or browning reaction known as “fermentation”. Much of the effort in the tea manufacture goes into controlling timing, rate and degree of this reaction. It is important to note that this is not a true fermentation, but rather an enzymatic oxidation process, and it occurs when the cellular contents (polyphenols and polyphenol oxidase enzymes) are mixed in presence of oxygen. There are many variable parameters in tea processing. The outlines of major steps of black tea processing are presented below [22].
Figure 6.5 Black tea
6.7.1 harvesting Harvesting (Figure 6.6) is not technically a part of the manufacturing process. The harvesting is done manually or mechanically. It is also important to stress that freshly harvested tea shoots are perishable. They can be bruised or
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broken easily by prematurely triggering the fermentation process and causing deterioration in quality. To avoid these problems, it is necessary to begin the manufacturing process as quickly as possible after harvest [22]. Harvesting Withering Rolling / leaf distortion
Fermentation
Frying/drying
Sorting Figure 6.6 Processing of black tea
6.7.2 Withering Freshly harvested shoot contains 75–85% moisture. The moisture level need to be reduced to 50–70% before leaves can be handled properly in the maceration or rolling step that follows. This initial water reduction is called withering and can be accomplished in many ways. In south India where the climate is humid withering is done in enclosed lofts, where as in the north-east, it is done on open-air racks. The most common method is to spread the tea in large, indoor troughs designed to allow airflow through the leaf. Withering with this system is usually done with ambient or slightly heated air, and requires 12–14 hours. The tea must be treated very gently during the withering phase to avoid premature triggering of the oxidation process. Properly withered tea-leaves are very supple and soft to touch. The primary focus of withering is moisture reduction; other chemical changes also occur in the leaf during process. The withered leaves are physically rolled without breaking up excessively [22].
6.7.3 Rolling/ maceration/ leaf distortion The primary purpose of rolling step is to disrupt the cells of tea leaves to mix the substrates (e.g., polyphenols) with the enzymes (e.g., polyphenol oxidase)
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and triggering the fermentation process [23]. Based on the rolling mechanism, there are two main methods of tea manufacture. The first is called orthodox type of manufacture and the other is CTC (crush-torn-curl type). CTC grades are mostly granulated in appearance while orthodox grades are long particles or whole leaf type [22].
Orthodox rolling This traditional type of manufacture (i.e., rolling the withered tea leaves in rollers) has steadily lost favour with traders and consumers because it diffuses slowly, breaks into smaller particles easily while packing and most of all, it brews less cups per kilogram against CTC. Producers also find it more costly to produce. However, this slow process allows the end produce to retain a majority of delicate flavour molecules inherent in the plucked green leaf. Therefore, almost all teas produced in high elevation areas such as Darjeeling, Sikkim, Himachal and Tamil Nadu (Nilgiris) continues to be of the orthodox variety, fetching premium prices. The orthodox method of manufacture accounts for about 20% of the Indian crop, amounting to approximately 160 million kg [22].
CTC This style of manufacturing (i.e., crushing, tearing and curing the tea leaves in between twin metal cylinders with serrated surfaces) has the advantage by being a quick brewer and yielding more cups per kg. In the domestic market, where strong tea liquor is more in demand and more cups per kg are important, this type of manufacture has virtually taken over the demand. In the export market, particularly in the western hemisphere where the tea bags have gained popularity, CTC teas are in demand. In addition, for the tea plantation owner the cost of manufacture is less due to less waste and less caution needed in plucking. However, the CTC process does reduce the delicate natural flavours of tea. In India today, over 80% of tea production is of the CTC type, amounting approximately to a staggering 650 million kg/year [24].
6.7.4 Fermentation Immediately following the maceration or rolling step, fermentation begins. This step is of critical importance, being at a stage where briskness, colour and strength are being developed. Depending on the style of rolling or maceration used, the fermentation process generally requires between 0.75 and 3 hours to accomplish. All teas have optimum ‘fermentation’ time for any given characteristic. Oxygen, temperature and humidity are the key variables that
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are controlled during fermentation. Higher temperatures and a greater supply of oxygen cause things to proceed more rapidly. Humidity is controlled to prevent leaf from drying out. During fermentation the leaf changes colour from green to coppery black. The characteristic tea aroma also develops. It is important to take steps to ensure evenness of fermentation within the tea.
Changes occurring during fermentation During fermentation, following physical changes occur: disappearance of bitter taste of tannin and the development of a pleasant, astringent taste due to oxidation of tannins. The first stage in the fermentation of tea is the enzymatic oxidation of ascorbic acids with the formation of dehydro-ascorbic acid and H2O2. H2O2 and peroxidase then oxidizes the tea tannin. As each molecule of tea tannin takes up one atom of oxygen only in its oxidation and also tea tannin contains the catechol grouping, so the primary product of oxidation of tea tannin is orthoquinone. These orthoquinones are condensed to theaflavins, which are further oxidized to thearubigins (Figure 6.7). Polyphenolic bodies Enzymatic oxidation Orth quinones Condensation Theaflavins (TF) Oxidation Thearubigins (TR) Figure 6.7 Changes during fermentation of black tea
6.7.5 Drying The first objective of a drying process is to arrest fermentation. This is accomplished by exposing the tea to hot air in the first stage of drying operation. The second objective of drying is to reduce the moisture level to 3–4%. There are many approaches to drying. These range from simple batch dryers to very sophisticated fluidized bed designs.
6.7.6 Sorting and fibre removal The final stage of tea processing is the classification of leaf according to the size and removal of stalk and fibre particles. Classification is accomplished by passing the tea over a series of vibrating screens. Stalks and fibre particles are removed electro statically. The final grades of tea are based on the size of
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particles. The major grades, in descending order of size are whole, broken, fannings and dusts. The relative proportion of different grades is primarily the function of the methods used for rolling/ maceration step. Whole leaf teas are produced only through orthodox tea manufacture. The rotovane produces leaf fragments primarily in the broken category. CTC machine produce particles primarily in the fanning size range [23].
6.8 Comparison of tea quality Comparison of the quality of various types (green, green brick, yellow, white, oolong and black) of tea is described in Table 6.1. The parameters include tenderness of fresh leaf, infusion colour, infused leaf, aroma and taste. Table 6.1 Comparison of the quality of various types of tea [17, 22]
Teas
Tenderness of Fresh leaf
Infusion colour
Infused leaf
Aroma
Taste
Green tea
bud
Brilliant green
Jade green
Fresh of Chestnut
Brisk
Green brick Tea
Yellow tea
White tea
bud and 4–6 leaves with some old stalks Leaf tea bud and 4–6 leaves Bud tea – 1 bud and 1–2 leaves
Brownish yellow
Bright Yellow
Bud and 1–2 Light orangish leaves or bud yellow
Hard, Stalk, pine mixed smokes and bluish brown arches flavour
Tender yellow fresh and pure
Plane
Open and mixed
Fresh and pure Flower odour
Oolong tea
Bhanji bud and 2–3 leaves
Golden yellow
Green leaf with yellow margin
Black tea
Bud and 2–6 leaves
Brownish yellow
Brownish orange
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Mellow
Plane
Rich and mellow
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7 Chemical composition and pharmalogical, medical properties of tea
7.1 Introduction Tea (Camellia sinensis) is one of the most commonly consumed beverages in the world today. Since ancient time, tea has been regarded as a healthy beverage. In Chinese literature (from Tang Dynasty), tea has been rated as a leading health giving beverage and a cure for many diseases [25]. The health benefits of tea have been known to human civilization for centuries. In earlier days, tea infusion was popular for improving blood flow, detoxification and disease prevention. The types and percentage content of flavonoids (polyphenols) present in tea usually differ depending on the variety of leaf, the environment in which tea is grown, its processing, manufacturing, particle size of ground tea leaves and the infusion prepared. Typically, more than 90% of the total tea phenolic compounds are reported to be flavonoids [25]. However, fresh tea composes of water (75–78%) and dry matter (22–25%). Proximate composition of tea leaves is provided in Table 7.1. Table 7.1 Proximate composition of dry matter of leaves [26]
Components
Percentage
Proteins Free amino acids Alkaloids Polyphenols Sugars Organic acids Lipids Pigments Ash Vitamins Aroma substances
20–30 1–4 3–5 20–35 20–25 1–3 2–6 <1 2–5 <1 < 0.1
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7.2 Diversity of therapeutic compounds in tea Tea has important chemical constituents, some of which are as unique as the plant itself. Main constituents of tea leaves were broadly identified to be carbohydrates, proteins, polyphenols, caffeine, theanine, vitamins and minerals. But these chemicals in tea leaves undergo dynamic changes as green tea leaves are converted into black tea during the process of manufacturing. There is nothing static about these compounds because these undergo rapid changes not only during manufacturing process, but also according to agricultural practices, sunlight, plant location and varieties. The leaf also contains enzymes that facilitate the chemical reactions in processing young shoots to produce green, oolong and black teas [27]. The chemical composition of fresh tea flush on dry weight basis is provided in Table 7.2. From therapeutic point of view, polyphenols and caffeine are pivotal, though vitamins and minerals are also of considerable medicinal significance. It is generally believed that these chemical constituents of tea, together or separately, most probably by their interactions affect both the quality and the medicinal attributes [28].
7.2.1 Polyphenols Tea contains 30–42% polyphenols on dry weight basis; catechins in tea are unique and important in particular. Catechins generally belong to a group of compounds, the flavonoids, which have C6–C3–C6 carbon structure (Figure 7.1) with two aromatic rings [29]. Catechins were first reported using the technique of paper chromatography. Major catechins represent (−)-Epigallocatechin3-gallate (EGCG); (−)-Epigallocatechin (EGC); (−)-Epicatechin-3-gallate (ECG); and (−)-Epicatechin (EC). The highest concentration is that of EGCG, followed by EGC, ECG and EC in decreasing order. Other minor catechins include (+)-Gallocatechin (GC), (−)-Gallocatechin gallate (GCG), (−)-Catechin gallate (CG) and (+)-Catechin. Table 7.2. Chemical compositions of fresh tea flush [27]
Component
% dry weight
Total polyphenols
25–35
Flavanols
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(-)- Epicatechin
1–3
(-)- Epicatechin gallate
3–6
(-)- Epigallocatechin
3–6
(-)- Epigallocatechin gallate
9–13
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Chemical composition and pharmalogical (+)-Catechin
1–2
(+)-Gallocatechin
3–4
Flavonol and flavonol glucoside
0.9–1.0
Leucoanthcyanins acids and depsides
2–3
Other categories Caffeine
3–4
Theanine
1
Carbohydrate (simple)
3
Protein
15
Ash
5
Cellulose
7
Lignin
6
Pigments
0.5
Lipids
4
A cup of tea may contain between 300 and 400 mg of polyphenols in total. EGCG is the major polyphenolic constituent contributing about 25–40% of the total catechin load of the tea. Polyphenols possess high antioxidant properties and protect human cells from adverse effect of damaging reactive oxygen species (ROS). The origin of most of the human diseases can be traced to ROS, and polyphenols can act as scavengers to ROS and prevent damages to cellular macromolecules [30]. The catechin content of tea varies according to genotype. The Assam variety generally accumulates more catechin than the China variety. In the former, catechin accounts for 30% of the dried matter against 20% in other varieties.
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THEAFLAVIN R=R1=OH THEAFLAVIN -3- MONO GALLATE (TF-2A) R= GALLOYL R1= OH THEAFLAVIN -3’- MONO GALLATE (TF-2B) R= OH R1= GALLOYL THEAFLAVIN -3,3’- DI GALLATE (TF-3) R=R1= GALLOYL Figure 7.1 Structures of catechins and theaflavins
Individual catechins (precursors) mixed with polyphenol oxidase resulted in the development of bioflavonols in addition to theaflavins. Thearubigins are formed by the polymerization of catechins and constitute 10–20% in black tea which is 10–20 times greater than the dry weight of theaflavins. High theaflavin content usually implies good manufacturing practices. Classification of tea poly phenols is presented in Figure 7.2 [27]. Phenolic polyphenols
Non flavanoid polyphenols
Flavonols (Low level)
Unconverted Catechin
Flavanoids
Flavanols (High level)
Catechins (4 major groups)
Theaflavins (Accounts for 10–15% of converted catechin)
Flavanoids acids
Isoflavones
Converted catechin
Thearubigins (Accounts for 40–60% of converted catechin)
Figure 7.2 Classification of tea polyphenol
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7.2.2 Caffeine Caffeine (trimethylxanthine, Figure 7.3), a purine alkaloid constitutes 2.5– 5.5% of the total chemical constituent present in tea leaf on dry weight basis and occurs along with small quantities of monomethylxanthine and dimethylxanthine [31]. Caffeine being a product of methylation of purine nucleotides does not result from the degradation of ribonucleic acid, as supposed to be earlier. Recently, a gene in the tea leaf encoding caffeine synthase, N-methyltrasferase, has been cloned and the recombinant enzyme was produced in E. coli [32].
Figure 7.3 Structure of caffeine
7.2.3 Vitamins Tea contains a wide range of vitamins that include carotene, riboflavin, nicotinic acid, pantothenic acid, ascorbic acid and thiamine, though most of them are lost during the processing of fresh green tea leaves to black tea. Vitamin B content of black tea ranges from 1.4 µg% of biotin to 127.5 µg% of riboflavin [27].
7.2.4 Carbohydrates Carbohydrates constitute about 4–5% of solids extracted in tea infusion. Though concentrated mostly in roots, carbohydrates are not uncommon in leaves. From the nutritional point of view, carbohydrate content is significant [33].
7.2.5 Lipids Lipids are an interesting group that shows marked variation in their chemistry. Young tea leaves contain more phosphotidyl ethanolamine and phoshotidyl choline than mature leaves, but monogalactosyl diglyceride are present in higher concentrations in mature leaves [34]. The contents of neutral lipid, glycolipid and phospholipid and their fatty acid composition in processed leaves at different stages
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of black tea manufacture were reported. Glycolipids account for approximately 50% of the total lipids and are rich in linolenic acid. Neutral lipids are found in moderate amounts (35%) and contain a high content of lauric, myristic, palmitic, stearic, oleic and linoleic acids. Phospholipids are present in the least amount (15%) and possess a high proportion of oleic, linoleic and palmitic acids. With the maturation of the tea shoot, the lipid content is reported to increase. Considerable losses of lipids/fatty acids were observed during the withering process as well as in the firing process. The other stages of processing (rolling and fermentation) registered only a minor change in lipid/fatty acid contents. The superior flavour of orthodox teas over CTC teas is related to lipid degradation and to the volatiles produced. Wide variation in lipids, fatty acid composition of the lipid fractions and flavour content was described with season and clonal variations [35].
7.2.6 Amino acids Amino acids constitute about 2–3% of solids. These include theanine, asparitic acid, threonine, glutamic acid, glycine, α-alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, arginine, glutamine, asparagines and tryptophan. Theanine (50% of total amino acids), unique to tea and identified as N-ethylglutamine, accounts for 1% of the dry weight of tea. It possesses an antagonistic action against the stimulating action of caffeine. Theanine is also a constituent of the thearubigin fraction which is responsible for most of the colour of tea brews and is a prime factor in the taste of green tea.
7.2.7 Carotenoids and pigments The 14 carotenoid compounds identified in tea-leaves are mostly concentrated in mature leaves. However, their therapeutic significance is not clear. Tea pigments, however, have considerable medicinal properties particularly beneficial in cardiac diseases. About 125–250 mg of green tea pigments thrice a day appears to have good effect on human subjects [36].
7.2.8 Triterpenoids The unsaponifiable portion of the tea extract contained spinasterol glycoside and β-amyrin in leaves, roots and stems. The other fractions, the saponins, are mostly active in roots [36].
7.2.9 Minerals Minerals constitute about 4–9% of the inorganic matter of tea. For dental health, fluorine (3–200 ppm) in leaves could prevent dental decay. The role
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of aluminium (20–11000 ppm) is controversial, but potassium (9000–34000 ppm) could have a supplementary effect in diets lacking potassium [37].
7.3 Pharmacological aspects associated with tea consumption In the normal human life span, occur lifestyle-related diseases that may be preventable with non-toxic agents. This section deals with the preventive activity of green tea in some lifestyle-related diseases. Green tea is one of the most practical cancer preventives as shown in various in vitro and in vivo experiments and epidemiological studies. Among various biological effects of green tea, it showed inhibitory effect on TNF-α gene expression mediated through inhibition of NF-kB and AP-1 activation. TNF-α is an endogenous tumour promoter. TNF-α is also known to be a central mediator in chronic inflammatory diseases such as rheumatoid arthritis and multiple sclerosis. It was hypothesized that green tea might be a preventive agent for chronic inflammatory diseases. To test this hypothesis, TNF-α transgenic mice, which over express TNF-α only in the lungs, were examined. The TNF-α transgenic mouse is an animal model of human idiopathic pulmonary fibrosis, which frequently develops lung cancer. Expressions of TNF-α and IL-6 were inhibited in the lungs of these mice after treatment with green tea in drinking water for 4 months. In addition, judging from the results of a prospective cohort study, green tea helps to prevent cardiovascular disease. In this study, a decreased relative risk of death from cardiovascular disease was found for people consuming over 10 cups of green tea a day, and green tea also had life-prolonging effects on cumulative survival. These data suggest that green tea has preventive effects on both chronic inflammatory diseases and lifestyle-related diseases (including cardiovascular disease and cancer) resulting in prolongation of life span [38]
7.3.1 Cardiovascular system Epidemiological observations suggesting an inverse correlation between tea consumption and the incidence of cardiovascular diseases have been well established. It gives an overview of the effects of polyphenolic compounds in tea on the function of the cardiovascular system, especially, on various signal transduction pathways in cardiovascular cells. The underlying mechanisms of tea polyphenols in preventing cardiovascular disease, however, are yet to be well understood. It is widely known that the incidence of coronary events (death definitely or probably due to coronary heart disease or nonfatal myocardial infarction) in Japanese is substantially lower than in Western populations. In Japan, as well as in other Asian countries, tea consumption is very high, and green tea is favoured in Japan. Green tea is made by steaming
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freshly harvested tea leaves and therefore, contains more antioxidants and vitamins than fermented teas such as oolong or black tea. The major polyphenols of green tea are catechins which constitute about one third of green tea total dry weight. The major catechin is (−)-epigallocatechin-3gallate (EGCG). The biological effects of tea polyphenols are mainly focused on the effects of EGCG, including the prevention of LDL oxidation, reduction of platelet aggregation, lipid regulation, and inhibition of proliferation and migration of smooth muscle cells. Any of these factors might be promising in reducing cardiovascular diseases. Recently, in Japan, a large populationbased cohort study of 40,530 subjects showed green tea consumption to be inversely associated with mortality due to cardiovascular disease. In another study that enrolled 203 patients who underwent coronary angiography, the observation is that green tea consumption was significantly higher in patients without coronary artery disease than in those with coronary artery disease. However, most of the effects of tea polyphenols in cell culture systems are observed with rather high doses of these compounds – doses that are not compatible with tea intake in daily life. In addition, the bioavailability of tea catechins is very low. Because tea is comprised of many different ingredients, it is unresolved whether the beneficial effects of tea are due to EGCG or theaflavins, or combinations of any of tea’s ingredients. Evidence from both basic experiments and prospective cohort studies is accumulating; data from randomised and controlled clinical trials connecting basic experimental results to epidemiological observations are lacking. The possibility that dietary tea intake reduces the risk of cardiovascular events remains open to the need for further clinical trials to clarify the effects of tea polyphenols in humans in order to recommend their use against cardiovascular diseases [39].
7.3.2 Cancer The possible cancer-preventive activity of tea and tea polyphenols has been studied extensively. Many studies in animal models, cell lines are done and possible relevance of these studies to the prevention of human cancer is revealed. The cancer-preventive activity of tea constituents have been demonstrated in many animal models including cancer of the skin, lung, oral cavity, esophagus, stomach, liver, pancreas, small intestine, colon, bladder, prostate, and mammary gland. The major active constituents are polyphenols and caffeine, of which (−)-epigallocatechin-3-gallate (EGCG) is most abundant, most active and most studied. The molecular mechanisms of the cancer-preventive action, however, are just beginning to be understood. Studies in cell lines led to the proposal of many mechanisms on the action of EGCG. However, mechanisms based on studies with very high concentrations of EGCG may not be relevant to cancer prevention in
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vivo. The auto oxidation of EGCG in cell culture may also produce activities that do not occur in many internal organs. In contrast to the cancer prevention activity demonstrated in different animal models, no such conclusion can be convincingly drawn from epidemiological studies on tea consumption and human cancers. Even though the data using human are inconclusive, tea constituents may still be used for the prevention of cancer at selected organ sites if sufficient concentrations of the agent can be delivered to these organs [40]. Green tea has attracted large attention, recently, both in the scientific community and in the public opinion for its pronounced health benefits towards a variety of disorders ranging from cancer to weight loss. A clear link between the health benefits of green tea and the high content of catechins has rapidly emerged. In particular, much emphasis has been given to the anti-cancer effects of these substances and to the investigation of the underlying biochemical mechanisms [41].
7.3.3 Malaria Appreciation of the health effects of green tea has been hindered by the low oral bioavailability of its polyphenolic catechins. Moreover, absorbed green tea catechins are known to undergo rapid and extensive metabolic transformations. These are most probably the reasons why no association has been reported so far between green tea consumption and its anti-malarial effects, despite the large use of this beverage in several Asian countries where malaria is endemic. To evaluate the possible interactions between artemisinins and a variety of natural substances, the specific anti-plasmodial properties in vitro of the green tea catechins, either alone or in combination with artemisinins, against two distinct Plasmodium falciparum strains 3D7, chloroquine sensitive (CQS) and FCR-1/FVO, chloroquine resistant (CQR) were analysed. Also, the anti-malarial effects of crude extracts of green tea have been studied. A crude extract of green tea as well as two of its main constituents,epigallocatechin-3-gallate (EGCG) and epicatechingallate (ECG) strongly inhibit Plasmodium falciparum growth in vitro. Both these catechins are found to possess the anti-malarial effects of artemisinin without interfering with the folate pathway. Establishing the anti-malarial effects in vitro of the crude extract of green tea as well as of some of its major polyphenolic constituents is of great interest. Indeed, these substances are very abundant and widespread in the malaria endemic countries, and are cheap, easily accessible, safe and virtually lacking of systemic toxicity. The additive/sub-synergistic interaction observed between EGCG/ECG and artemisinin might be conveniently exploited to design new and/or more effective combination therapies [41].
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7.3.4 Dental health Epidemiological surveys have reported that a considerable percentage of population that drink tea on regular basis have lesser carious teeth., Green tea and various catechins are also known to inhibit growth of cariogenic bacteria by preventing the adherence and growth of such bacteria on the dental surface. Also, the adsorption of theaflavins to dental enamel may play an important role in curbing the formation of plaque and keeping the teeth clean and shining [42]. Tea could be effective towards the replenishment of fluoride to the oral cavity as well as prevent dental decay and gum diseases [43]. It has also been reported that the tannins in tea can inhibit salivary amylase, thus, reducing the carcinogenic potential of starch-containing foods [44].
7.3.5 Oxidative stress Green tea, an infusion prepared with the leaves of Camellia sinensis is particularly rich in flavonoids, which are strong antioxidants. Tea drinking, by providing antioxidants, may become valuable in several oxidative stress conditions and even while evaluating the effect of green tea drinking on some factors reflecting the development of oxidative stress in plasma and in erythrocytes. It is evaluated that the green tea affects the total antioxidant status (TAS), the lipid peroxidation products-malonyldialdehyde (MDA), malonyldialdehyde+4-hydroxy-2(E)-nonenal (MDA+4-HNE) and the oxidative changes in erythrocyte membrane, namely membrane bound haemoglobin (MBH) and the band 3 profile. After drinking green tea, a significant reduction in serum levels of MDA and MDA+4-HNE and in the oxidative stress within the erythrocyte was reported. A rise in the antioxidant capacity was also observed. Drinking green tea is having beneficial effect by reducing the development or the enhancement of oxidative stress and, therefore, protecting the individual from oxidative stress diseases. Moreover, further studies are also needed to clarify the effect of green tea consumption, the value of regular green tea consumption and the way of preparation for a healthy effect [45].
7.3.6 Fluid replenishment In early days, tea was not considered to be an alternative to fluid replacement because of its diuretic action (due to presence of caffeine). However, it was later observed that tea did not exert any diuretic action unless the amount of tea consumption exceeds 6 cups (i.e. 250–300 mg caffeine equivalent). It may be mentioned that owing to volume of fluid that is consumed with tea, the habit of tea consumption significantly contributes towards the daily recommended fluid intake in adults, thereby improving the hydration status [46].
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7.3.7 Gastrointestinal system It was reported that black tea extract given to rats for seven days inhibited development of both aspirin and cold-restrained, stress-induced, acute, gastric ulcer. Tea extract was found to reduce acid and peptic activity of gastric secretion induced by aspirin and cold-restrained stress [47]. Moreover, tea increased gastric glutathione peroxidase, hexosamine and sialic acid contents, thereby, suggesting the tea probably stimulate the overall production of gastric mucosa [48]. From studies it has been observed that ingestion of black tea infusion significantly inhibited aspirin, alcohol and serotonin-induced ulceration in rats. It was also observed that following black tea (infusion) pretreatment there was significant restoration of superoxide dismutase (SOD) and catalase (CAT) enzyme activity in gastric and liver tissue following ethanol induced oxidative stress [49].
7.3.8 Neurological effects of tea Both green and black tea extracts significantly potentates the onset, duration and mortality in experimentally induced convulsion in mice. These extracts are suggested to act probably by influencing the calcium channels. Tea infusion has been found to improve alertness, which could be attributed to both caffeine and theanine [50].
7.3.9 Anti-hyperglycemic activity The hot water extract of black tea was found to significantly reduce the blood glucose level of streptozotocin-induced diabetic rats. Studies have also shown that the constituent of tea may indirectly stimulate the secretion of insulin [51]. It has also been observed that green tea can reduce glucose transportation from intestine [52].
7.3.10 Anti-inflammatory and anti-arthritic actions Studies have shown the effectiveness of tea polyphenols in reducing the release of histamine and also hyaluronidase activity during the inflammatory process. Such anti-inflammatory and anti-arthritic activity (induced with collagen) has also been reported. The saponins present in tea leaf were found to inhibit carrageenin-induced rat paw oedema in a dose-dependent manner, probably by the inhibition of hyaluronidase enzyme activity and also by antagonizing the action of leukotriene D4. Tea has also been found to be useful in rheumatoid arthritis. Tea consumption also related to increased bone mineral density and relief from osteoporosis particularly in women [53].
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7.3.11 Skin and topical wound healing activity Tea leaves can inhibit bleeding from cuts and wounds, probably due to the involvement of tannins, when applied topically. Tea polyphenols (particularly EGCG and ECG) have been found to protect skin tissues from damaging effects of ultraviolet rays and also from acne [54].
7.3.12 Anti-microbial action Tea infusion has been found to be effective against bacteria (particularly gram-positive). Tea catechins demonstrate strong anti-microbial activity against Helicobacter pylori. Yanagawa (2003) [55] reported that tea extract show inhibitory affects against Salmonella typhi, Campylobacter jejuni, Campylobacter coli, Shigella, Closteridium, Pseudomonas and other different organisms. Tea was also found to be effective against amoebiasis. From animal cell culture studies, it has been observed that the tea polyphenols could be effective against rotavirus, influenza A virus and also HIV [56]. Immense beneficial potential of tea beverage is realised since studies have definitely revealed the extent of health benefits associated with tea and possible mechanism related to its pharmacological activities.
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8 High impact value-added products of tea
8.1 Introduction Tea is now in its high impact specialization, in all its forms. The constant innovations are making this beverage more popular than ever. It is becoming popular in stores and is on consumer’s favourite restaurant menu. Consumers are embracing Camellia sinensis for its health benefits as well as its delicious taste. In addition to increased availability of wide variety of teas, improved brewing methods and equipments have changed the way people perceive tea. In the past few years there is an increase in number of tea variations. One reason for its popularity is the added health benefits and that has caused the medical community to take note. The constant innovations are making this ancient beverage more popular than ever [1]. Tea is a widely consumed beverage, and for a number of third world countries tea is a major plantation crop that earns foreign exchange by way of exports. A disturbing trend in the export market that has become more and more evident in recent times is that the tea price fluctuates in erratic cycles. The Indian export trade is also afflicted by the increasing competition from other tea-producing countries and escalating cost of inputs, which tend to make the tea plantation uneconomical. This trend can be offset by increasing the productivity of tea plantation or by diversification into value-added products. In this section, a variety of value-added products are described. These include tea bags, packet tea, instant tea, flavoured tea, decaffeinated tea, fortified tea, tonic tea, tea cider, tea Kombucha, iced tea, herbal tea and tea concentrate.
8.2 Tea bags Tea bags (Figure 8.1) were invented in 1826. The poor quality of instant tea hither to marked has forced tea vendors to the manufacture of tea bags, which represents a compromise in convenience between instant tea and black tea. Tea bags which may be made of specially processed paper or nylon are used to brew cup of tea without the inconvenience of having to strain the tea
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leaves away as the bag is discarded after brewing. As a result of the slow rate of diffusion of the tea extract through the paper bag, it is necessary for the bag to contain tea having the large area to volume ratio, such teas are mostly CTC teas and dust tea grades. It is this growing tea bag marked for which the CTC tea is specially favoured. The advent of tea bags reduced the quantum of tea required for brewing a cup by around 20%. Furthermore tea dusts and often refuse or stalks of tea which can be hardly classified as tea leaves or included in the contents of the bags which are hidden from the consumer, the development of the nylon tea bag appear to hold the promise for good quality tea because the nature of tea contained with in the nylon bag is immediately evident to the consumer [57].
8.2.1 History and packaging designs of tea bags During 1908, the US tea importer Thomas Sullivan introduced tea bag to the world. By 1920s, tea bags were commercially produced in the USA and fully embraced in England by the 1960s. For some time, paper filters were chlorine bleached. This process created a dioxin chemical residue in the paper and waste water from the paper mill. Dioxin is known as potent carcinogen to avoid, thus the true flavour of the tea bag was drastically diminished. With that oxygen bleached paper took centre stage and continues to be used today. Many bags are also produced from nylon mesh and some are biodegradable. Tea fanning or dust has been used in tea bags. Another innovation t-sac is one of that Linda Smith of Divine tea has found offers an opportunity to marry loose leaf and the new tea bag technology. This German product is a chlorine free, natural brown tea filter, developed to address public concern for chlorine bleached paper. The bag has bottom fold that opens automatically, providing enough volume of tea to properly infuse [58].
Figure 8.1 Tea bags
A tea bag can deliver a brewed whole leaf tea in a short time. Whole leaf teas and herbs with convenience can be used, adding value and therefore allowing
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them to charge higher price. The hottest trend of the moment ‘pyramid’ shapes are made with silky, food grade nylon materials, with no glue or staples, and filled with whole leaf tea, fruits, flowers, and herbs. The concept was first launched in Tokyo, Japan, in the 1980s especially for green tea. Pyramid bags have more space than the traditional flat bags. It allows the packers to put what they formerly put in tins, instead of tea bags. When this pyramid bag is put inside the boiled water, the tea leaf expands and circulates inside the bag, so extracts better flavour from it. Tea bags are made up of silken infusers (made from food grade nylon) and are filled manually in tea gardens of Asia. The material is woven properly to have proper flow. Over the past few years a tea bag revolution has been taking place; and now even real connoisseurs can prepare a high quality, great-tasting infusion from a teabag. It is not just the taste and quality that has changed, but the shape too. The pyramid revolution started few years ago. The three-dimensional pyramid now been taken to new stage of style and sophistication, so that the consumer can have a teabag filled with quality large leaf tea, herb, flower or fruit, and can actually observe the material in the bag. Gauze pyramid bags are the latest technology in design. Ordinary square and rectangular cartons are no longer enough to entice the choosy shopper to this smart new-look teabag. So it is mentioned as ‘Vive la revolution’ [59]. There are many patents regarding tea bags, of which a few are described over here. A patent assigned to Ferro et al [60] describes a tea bag with a squeezing device provided with a string attached at one end to an infusion bag with a quantity of ground tea leaves sealed therein. A cover of two panels is joined together along a fold line and has a hole at the centre of the fold line. The string passes through the hole with a tag attached to the other end of the string. The panels of the cover can be used to squeeze the bag to extract infusion liquid and are disposable along with the bag. A patent by Heinrich [61] describes the method for producing a heat-sealable tea bag paper; the tea bag paper comprises a first phase of natural fibres in a weight percentage from 60 to 85% and a second phase of heat-sealable fibres with the remainder of the weight percentage from 15 to 40. The second phase penetrates the first phase in such a way that both sides of the paper are adapted to be heat-sealed, with the unit area weight of the paper being between 10 and 15 g/m2. The tea bag paper exhibits enhanced tea diffusion, and may be processed on special high-speed automatic tea packing machines, because it is heat-sealable on either side thereof. Drake et al [62] patented a double-chamber tea bag with a centrefold that is crimped by squeezing it between a toothed wheel and a plain wheel and a head fold in which the front chamber has a flap that folds over the part of the end of the front chamber between triangular folds at each corner.
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Patent assigned to Romagnoli [63] describes the method for attaching a tag to tea bag, where both have at least one border with reduced thickness. The method includes the following steps: hooking of first end or leader of the thread by an eye of a needle and running the thread into the border through to the opposite side or the border so as to make a loop in the thread, widening the loop in such a way as to form an aperture through which the thread can be inserted, inserting the leader into the aperture in the loop and releasing the thread from the needle, the thread being pulled in such a way as to tighten the resulting knot.
8.2.2 Kinetics of tea infusion The rate of infusion of caffeine from Ceylon Orange Pekoe tea of leaf size 1.4–2.0 mm in loose form and inside a tea bag membrane was determined at 80°C. The tea bags were varied in size and shape. It was found that the rate constant increased significantly with an increase in tea bag size until the ratio of tea leaf to tea bag size was 1:10. It also indicates that the shape of a tea bag had no influence on the rate of infusion, and that the tea bag membrane offered some hindrance to the infusion of caffeine [64]. Bag teas, packed 3 g of ground black, green, oolong, paochoung and pu-erh tea leaves (the particle size used was 1–2 mm), were steeped in 150 ml of 70, 85 or 100°C hot water to study the effects of the number of steeping (the same bag tea was steeped repeatedly eight times, 30s each time, as done in China for making ceremonial tea) and varied steeping durations (0.5–4 min) on caffeine, catechins and gallic acid in tea infusions. The changes in tea infusions during storage at 4 or 25°C for 0–48 h and the variations in these compounds of bag tea infused with150 ml of 4 or 25°C cold water for 0.5–16 h were also investigated. A HPLC method with a C18 column and a step gradient solvent system consisting of acetonitrile and 0.9% acetic acid in deionized water was used for analysis. Results for all kinds of tea samples showed that the second tea infusion contained the highest contents of caffeine, catechins and gallic acid, when bag teas were steeped in 70°C water. It was different from that steeped at 85 and 100°C, the highest contents existed in the first infusion. These compounds decreased gradually in later infusions. Higher amounts of caffeine, catechins and gallic acid could be released from bag teas, as hot water was used. As steeping duration prolonged, these ingredients increased progressively; however, their levels were lower than that cumulated from the infusions with the identical bag tea prepared recurrently at the same temperature and time points. (−)-Gallocatechin gallate and (+)-catechin existed in these tea infusions rarely and could not be detected until a certain amount of them are infusing. Except gallic acid that showed a significant increase and caffeine that exhibited no significant change, all kinds of catechins decreased appreciably
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after tea infusions were stored at 25°C for 36 h; nevertheless, all of them showed no evident changes at 4°C storage. Quantities of caffeine, catechins and gallic acid are increased along with time of cold water infusion. Their contents in 25°C steeped tea were higher than that made at 4°C; moreover, their infusion rates from bag teas to cold water were markedly lower than that steeped in hot water. Infusing efficiencies of non-gallated catechins were higher than gallated catechins under cold water steeping [65].
8.3 Instant tea The time consuming ritual of brewing tea appears irrelevant to the fast modern society, this lead to the discovery of instant tea. Instant tea is a dry extract of natural tea. Instant tea is portable, completely soluble in hot water, and need not to be pre-brewed. Due to this, instant tea has certain advantages over regular teas during trips, journeys and expeditions. Instant tea may be prepared from either black tea or from low-grade leaves, crude leaves, fannings collected after pruning of tea plantations. Many countries, which do not grow tea, prepare instant tea from manufactured tea. India is one of the major producers of instant tea, and the tea auction centres show that India is one of the major exporting country; it exports to the United Kingdom, West Europe, the USA, Australia and other countries [66]. Methods of instant tea preparations are described below. The basic technology is however common to all processes and is summarized in Figure 8.2.
8.3.1 First method Indian tea factories adopted the method developed by the Nestle Company (Switzerland). The method is based on the direct preparation of instant tea from the tea leaf. Indian tea factories produce instant tea of two kinds, for hot and cold consumption. The instant tea manufacturing process applied at Indian tea factories is carried out as follows. The tea leaf is withered, carefully washed and purified of contaminants and foreign bodies. Then it is cut in the Rotor vane type machines, transferred to the extractor and covered with warm water. The resultant suspension is exposed to fermentation in cylindrical extractors (fermenters). The fermentation time varies, depending on the water temperature and leaf quality. Then extract is separated from the tea bulk and centrifuged. The hot-soluble variety should reproduce, as far as possible, the characteristic aroma and taste of a cup of tea brewed in the conventional way. However, processing difficulties are enormous and there is a substantial difference in quality between a cup of hot instant tea and traditionally brewed tea [67].
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Cold water soluble instant tea is prepared by subjecting the extract to secondary purification, centrifugation in vacuo and spray drying. During the process, tea essential oils are trapped, purified and returned to the product before drying. In the dried granular instant tea, the moisture content is 2–4%. The yield of instant tea is 7–11% depending on the raw tea quality [67]. Extraction Clarification Aroma stripping Tea cream processing Concentration Maltodextrins Spray drying
Freeze drying
Free-flowing agents
Packaging Figure 8.2 Process of instant tea
8.3.2 Second method Extraction The key requirements for the extraction stage are high total yield of tea solids and highly concentrated extract. In the case of instant green tea, it is also necessary to ensure the leaf is heated to at least 70°C to inactivate enzymes. Modern extraction systems are based on counter-current flow and either batch or continuous systems may be used. Clarification is necessary after extraction. Centrifugation, decantation or filtration may be used, individually or in combination [66].
Aroma stripping Loss of aroma is a major factor leading to low-perceived quality in instant tea. Most modern processes strip the aroma constituents, rather than attempting to
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retain the aroma with the tea during concentration. Aroma stripping involves passing the stripping gas through the extract, or spraying extract into a stream of gas. An inert gas, such as nitrogen, is preferred for stripping and gives a higher quality product, although steam is widely used [66].
Tea cream processing On cooling, as tea solution becomes opaque and lightens in colour. This is due to the formation of tea cream, a colloidal substance that contains the same components as the original extract. Tea cream can be removed by cooling followed by precipitation or centrifugation. This method is effective, but results in a poor quality product due to loss of flavour compounds along with the tea cream. Solid yield is also reduced. An alterative method, which is widely used, is to maintain the temperature above 65°C. This is effective, but results in a stewed flavour due to polymerization of theaflavins [66].
Concentration Tea extract requires concentration before drying; a solids concentration of 40–45% is most common, although concentrations as low as 20% and as high as 51% were used. High solid concentrations in the dryer feed are desirable to improve reconstitution properties of the instant tea powder. Thermal evaporation under reduced pressure is most commonly used, evaporators usually being of the falling film or plate types. Aroma recovery equipment may be fitted to avoid the need for a separate aroma stripping stage. More recently efforts have been made to reduce the damage suffered during concentration, with the use of reverse osmosis or freeze-concentration. Reverse osmosis offers advantages in terms of reduction of thermal damage and avoidance of aroma stripping. Freeze-concentration involves the removal of ice crystals formed when the tea extract is cooled beyond freezing point [66].
Drying The vast majority of instant tea is dried using a spray dryer. This consists of a chamber in which atomized tea extract, with a droplet diameter of 10–150 µm is mixed with hot air at an inlet temperature of 240°C. Drying is almost instantaneous and the temperature of the product does not exceed 70°C. Large dried particles are removed from the base of the dryer, while small particles remain in the air stream and are removed by a series of cyclones and filters. Dryers used in instant tea production are of the co-current type in which air and product flows are in the same direction. Spray dryers used in the production of instant tea usually complete the drying operation
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within the drying chamber, producing a powder with moisture content of 3–5%. Loss of aroma occurs during spray drying, but is minimized by using a feed of high solids concentration. Aroma loss can be further reduced by addition of carbohydrates such as maltodextrin to the feed. Freeze dried instant tea has been introduced on a number of occasions, but appears to have been met with only limited success. Freeze dried tea is granulated after drying [66].
Additional ingredients Addition of free-flow agent such as tricalcium orthophosphate is common practice. Foaming is further problem, especially in cold water – reconstituted tea silicon powder is highly effective and acts both to prevent foam formation and to defoam. Attempts have also been made to use additives to improve the colour and flavour of tea. A number of commercial products are available, and include tea aroma distillate and tea aroma oil. Instant lemon tea powder contains lemon flavouring, often with a carrier, together with various other ingredients including acidulants and anti-oxidants. Instant white tea is also available and is a blend of tea powder with spray-dried skim milk powder and a whitener, usually consisting of glucose syrup, vegetable oil and caseinates. The low temperature suppresses the volatility of delicate oils, which impart to its characteristic tea flavour. Hence it has become the practice to scent the cold soluble instant tea, this lead to invention of flavour teas [15].
8.3.3 Decaffeinated and flavoured instant tea A major new trend is the rise of decaffeinated instant tea. The marketing reason makes good sense because of its health message all around. Like organic specialty tea, decaffeinated instant / RTD varieties are also available. Another broad trend is an increase in flavouring, including instant tea mixes and RTD varieties. In the old days, the choices have been lemon or non-lemon, now the choices are truly amazingly diverse. Peach and raspberry are becoming relatively common. Selected industries introduced light green during 2004, stating the brand offer both the benefits of an antioxidant and low calorie drink and attracts a health-oriented consumer, not usually known to the instant tea market. Decaffeinated teas are flavoured with a combination of flavours recently, e.g., Republic of Tea – a RTD decaf black tea with Ginger Peach; Honest Tea has a brand called Decaf Ceylon. Honest Tea goes beyond organic; the bottle is PET-1, widely considered the most environmental friendly form of fossil-fuel-derived plastic [68].
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8.4 Iced tea Iced tea (Figure 8.3) started to become popular in South of USA and continued to grow in popularity when, on an unseasonably hot day in 1904, Richard Blechynden – who has been credited with inventing iced tea – added ice to his hot tea samples at the World’s Fair in St. Louis. The drink was a hit and iced tea has been an American staple ever since. Typically fannings, dust and other offgrade teas are found in a standard commercial mass-market iced tea. But there is a new wave of premium-iced teas that include Black Orange Pekoe (BOP) and BOP fannings, although sometimes they include a full leaf. Speciality tea companies have been able to sell premium-iced tea to restaurants and retailers who are willing to pay higher price for this tea. Whether favourite cup of tea is hot or cold, the most important thing to know is what’s inside your cup [69]. Several patents on iced tea indicate the commercial importance. The Sweden is world leader in consumption of ice tea, at 39 litres per capita per year, compared with Europeans of only 6 litres. The tea concentrate, water, and additives are mixed to pre-set concentrations by flow and degree of Brix. Virgin-ice tea contains fructose instead of sugar making it suitable for diabetics. Two flavours are produced peach and cool lemon. The tea concentrate is fed into the water stream to form the pre-blended ice tea. Flow meters and process logic controllers control the ratio between the two streams. Pasteurization and aseptic treatment of the ice-tea product takes place in a tetra-therm aseptic drink module. The tetra pack system of flash pasteurization lasts for 30 seconds; it prevents the product from losing its flavour and aroma. Air is removed from the product by deaeration. Deaeration is important as light acts as a catalyst and speeds up the oxidation process and air can affect the final product. An extract aroma trap ensures that the full taste is retained in the final beverage.
Figure 8.3 Iced tea
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There are six stages. At the first one, the bottle is flushed with air at 100°C. At the second stage beside hot air, 200 ml of hydrogen peroxide is added to sterilize it. Three separate drying stages follow this, when air at 100°C evaporates the liquid. The bottle is actually filled on the sixth station. Filling nozzles are positioned clear of the neck, and flow meters control the dosage of the beverage. There is a small headspace in the bottle to prevent neck overrun. A screw cap is applied and labels it. Traditionally, ice tea is made by extracting soluble tea solids from tea leaves and then adding various flavouring agents such as sugar, lemon, mint, peach and the like. The beverage is then cooled. This method results in a good quality tea product. This is a time-consuming method. It is possible to make an ice tea beverage by steeping tea leaves in water at reduced temperatures; the beverage obtained is poor unless it is steeped for excessively long periods. The extraction is too slow and the beverage has a poor colour and a flavour, which lacks body. A patent by Carns et al [70] describes the method of preparation of tea bag for ice tea beverages. The tea bag contains a tea mixture made up of 30–95% by weight of tea leaves, and 5–70% dried soluble tea solids. The tea bag may be immersed in cold water to provide a tea beverage of acceptable colour and flavour in less than 10 minutes. A patent assigned to Lunder et al [71] describes the production of a cold soluble tea product and more particularly to a powdered tea extract, which is readily and completely soluble in cold water. A cold soluble tea powder may be prepared from tea leaves by a very simple process without using chemicals or enzymes, which involves maceration, a cold-water extraction and then a hotwater extraction. Black tea leaves are macerated with water for 20 minutes to obtain a good wetting of the tea leaves. The maceration step softens and swells the tea leaves making extraction in cold water easier and more productive. A patent [(US 4,919,041)] has been assigned to Miller (1990) [72], which describes a system for brewing and dispensing of pre-sweetened iced tea, which is suited for use in a fast-food restaurant. This system includes supply of fresh tea brew and sweetener liquid in a chilled condition using a chiller; the chilled tea and sweetener are under constant circulation. A dispenser is provided for dispensing pre-sweetened tea having a selected ratio of sweetener and tea at one or multiple locations. A compressor propels the sweetener and the tea under pressure from supply to the chiller and from there to the dispenser. Remaining tea and sweetener from the dispenser are circulated back to the chiller and are kept constantly circulating until dispensed. An alarm, including fluid level detection, is also provided to ensure that the proper levels of the tea and sweetener supplies are maintained while the system is in operation. Water supply, valve and drain lines are further provided to enable the system to be easily flushed and sanitized.
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The research in the field of tea resulted in the invention of an appliance for preparing freshly brewed iced tea with microwave energy comprising a funnelshaped reservoir of moulded plastic construction having an open upper end, closed lower end and an aperture near the closed lower end. The reservoir is dimensioned to hold a pre-determined amount of water and tea simultaneously. A valve arrangement controls the flow of liquid from the reservoir through the aperture and to move from a closed position to an open position after water in the reservoir is heated by using microwave energy to a pre-determined temperature. A receptacle is dimensioned to hold the hot brewed tea from the reservoir and a pre-determined amount of ice, and includes a barrier to shield ice therein from microwave energy [73]. Hatch et al [74] disclosed a method for making low-calorie powdered ice tea and its composition (Table 8.1). The ice tea composition comprises finely ground particles of tea solids, finely ground particles of artificial sweetener (e.g., Aspartame), and granulated (size 425–1180 µ) citric acid. With such a composition, the ice-tea solids and the citric acid dissolve in a liquid at different rates. The macerated leaves are then extracted with cold water; after the extraction, cold extract is separated from the tea leaves. Later the hot water (65°C) extraction is carried out for 15 minutes, and then the extract is separated from the tea leaves. The separated hot extract is treated with activated charcoal before being mixed with the cold extract; this step prevents the formation of cold-water insoluble material formed by tea cream and polymers of polyphenols. The activated charcoal is washed with hot water to minimize the losses of solids. The cold and hot extracts are then mixed and concentrated to desired solids content before drying, by freeze or spray-drying. Table 8.1 Composition of low-calorie powdered ice tea formulation
Ingredients
Weight (%)
Conventional ice tea solids
45
Aspartame
6
Citric acid
34
Flavouring agents
9
Trisodium citrate
6
8.5 Herbal teas An herbal infusion refers to a single herb or a blend of herbs (most often they are caffeine free) infused in boiling water (steeped for 3–5 minutes). According to the pharmacopoeia of the people’s republic of China, herbal tea (Figure 8.4)
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is a kind of herbal medicine mixture with a dosage form of a coarse powder or small cube, and granular form. Herbal tea beverage is prepared with boiling water as infusion or short-time decoction, and then taken as tea drink. Many a times, it could be an herbal decoction or herbal extract along with tea. Herbal tea blends can contain not just combination of herbs but also spices, seeds, fruits, flowers, barks, roots and grains. The earliest herbal tea appeared in the Tang Dynasty and further developed in the Song, Yuan, Ming and Qing dynasties as well as in modern China. Wang Tao (720 AD) described the preparation, application, and indication of herbal tea in Medical Secrets of an Official. An official publication called Holy Benevolent Prescriptions in Song Dynasty (992 AD) carried eight herbal tea recipes, such as menthol tea, Alium-Glycine Soja fermented tea and Gypsum tea, to treat the common cold and its complicated headache and fever, respectively [75]. A patent assigned to Chang [76] describes a system for extracting and concentrating active ingredients from herbs. The herbs are boiled in a suitable extraction medium, such as water or alcohol, in an extraction vessel. The extraction vessel is connected to a vacuum line that serves to lower the pressure of the extraction vessel and to draw off herbal vapour formed in the boiling process. A vapour condenser cools the herbal vapour, forming herbal condensates that is collected and periodically reintroduced into the extraction vessel, thereby lowering the density of the herbal liquid. After a predetermined period of time, first portion of herbal liquid is transformed from the extraction vessel to a concentration tank, while the remainder of the herbal liquid continues to boil in the extraction vessel. Further a concentration tank is provided with side and bottom heating elements work together to minimize burning of the contents of the concentration tank. Herbal teas are known for their medicinal properties, the herb used may cure particular disease. A few herbal teas are listed in the Table 8.2. Table 8.2 Herbal teas and herbs used for health benefits
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Herbal tea
Herb
Anti diabetic tea
Gyminema sylvestre
Laxative tea
Emblica officinalis
Rejuvan tea
Piper longum
Anti stress tea
Withania sominfera, Ocimum sanclum
Anti cough tea
Ocimum sanctum, Zingiber officinalis
Anti obesity tea
Garcinia cambogia
Memory tea
Gynostemma pentaphylla
Immune system strengthener
Astragalus membranacus, Radix codonopsis
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Figure 8.4 Herbal tea
8.5.1 Tea surrogates Besides the leaves of the tea shrub, the leaves/flowers of other plants are sometimes dried and a beverage is made from them in the same way. Most important surrogate is Yebramate, Paragnay Tea, or Brazilian Tea. It is made from the dried leaves of Ilex paraguayensis. Other surrogates include Bourbon Tea (fa-am) consists of dried leaves of Angraecum fragrans common in Africa. Iwan tea (Kaproic) – mixture of leaves of Epilcbium angustifolium, Filipendula ulmaria, Sorbus aucuparia, South Sea Tea – leaves of Ilex vomitoria [8].
8.5.2 Gabaron tea Gabaron tea is made from anaerobically treated leaves, which is rich in Gamma-amino butyric acid (GABA). The amount of GABA in Gabaron tea is 70 times as high as that in ordinary tea (Omori et al, 1991). GABA is known to be one of the major inhibitory neurotransmitters in the sympathetic nervous system and to play an important role in cardiovascular function. GABA is widely distributed and, together with alanine, has been reported to accumulate in plants, chlorella and mammalian tissues, under anaerobic conditions. In
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Japan, it was accidentally found that a large amount of GABA accumulate in green tea under anaerobic condition. It was examined further that the GABA content of green, oolong and black tea is made under anaerobic condition, and GABA accumulates in all teas. GABA is being reported to reduce blood pressure in experimental animals and humans; GABA tea is produced on a commercial basis for people with hypertension. [77].
8.5.3 Banana flower tea Banana is the world’s most unique fruit tree. A process of obtaining fresh banana flowers and trimming, cleaning, and washing produces the banana flower tea. This is followed by cutting/shredding the flowers. The flowers are then dried in a dryer or sun dried followed by roasting. Roasting of the banana flowers takes place in a roaster at 400–450°F for 5–7 minutes. The roasted flowers are then milled, blended with desired flavour and aroma materials, and packaged in tea bags and boxes for subsequent brewing to form a banana flower tea beverage. Banana is rich in vitamins, minerals, essential amino acids and other nutrients that are needed to keep our body disease free and healthy. It is believed to be an excellent source of antioxidants and tannins. Antioxidants are chemicals known to prevent cancers and tannins have been reported to prevent bladder and urinary tract infections in women [78]. Process of banana tea manufacture is shown in Figure 8.5. For the preparation of fruit tea, Zaimi (1993) [79] has been assigned with a patent (US 5,238,700). The fruit selected was a hard fleshed, light colour fruit like quince, first it was grated and the gratings were heated and grilled to dark brown and shredded to a mass which was then steeped in boiling water. This resulted in a sweet caffeine-free tea (Figure 8.6).
Banana flowers Cutting or shredding Drying Roasting 400–450°C, 5–7 min Brewing Banana flower tea Figure 8.5 Process of banana flower tea manufacture
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High impact value-added products of tea Hard-flesh, light colour fruit (quince) Flesh grating Heating and grilling (darker brown) Shredded mass-steeped in boiling water Sweet caffeine-free tea Figure 8.6 Process for fruit tea manufacture
8.5.4 Ginseng fruit tea The human physiological need for vitamins has been well established. Regular dietary consumption of vitamins is essential to good health. A flavoured drink, especially tea, is a common source of refreshment. Herbal teas can be a source of caffeine-free stimulation and a source of vitamins and nutrients. The patent US 6, 210, 738 [80] describes a tea beverage containing ingredients from the ginseng berry (Table 8.3). A generalized formula for the tea beverage of the present invention comprises ginseng berry combined with fruit extract and/ or one or more natural health promoting ingredients. The ginseng berries are freeze dried, and the above said ingredients are added to the freeze-dried ginseng berries. Table 8.3 Essential vitamins and ingredients in ginseng berry
Vitamin
Quantity per gram
Riboflavin
172 µg
Vitamin A
110 IU
Vitamin E
<2 IU
β-Carotene
17 IU
Table 8.4 shows information about various types of herbal teas with their compositional features according to manufacturer’s information.
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Table 8.4 Composition of herbal tea [81]
Tea
Content
Lift instant tea (lemon)
Dextrose, soluble solids of tea, citric acid, maltodextrin, sodium citrate, flavourings, vitamin C
Lipton ice tea (lemon)
Water, sugar, glucose syrup, citric acid, tea extract, lemon juice, trisodium acetate, ascorbic acid, flavouring
8.5.5 The erosive potential of some herbal teas Many epidemiological studies show a high prevalence of tooth wear, even in young patients. One factor that may be contributing to this problem is the consumption of herbal teas that are often considered to be ‘healthy’ alternatives to other beverages. The erosive potential of a variety of herbal teas was assessed through the measuring their pH, neutralisable acidity and their ability to erode enamel and these were compared to a positive control, orange juice. The pH of the herbal teas ranged from 3.1 to 7.1, and the neutralisable acidity ranged from 3.5 to 60.3 ml of 0.1 M NaOH. The amount of enamel removed following 1 h immersion in the herbal teas ranged from 0.00 to 9.6 mm. In comparison, the orange juice (control) possesses a pH of 3.7 and a neutralisable acidity of 21.4 ml and removed 3.3 mm of enamel. Many of the herbal teas tested were found to be more erosive than orange juice. This information will be of use to clinicians when counselling patients with tooth surface loss. Table 8.5 shows the data of laboratory results of enamel erosion for various kinds of herbal teas [81]. Table 8.5 Initial pH value, neutralisable acidity and enamel erosion values
Liquid
pH
Neutralisable acidity (ml)
Enamel erosion (mm)
Tesco blend
5.7
3.5
0.1
Lift instant lemon tea
3.8
31.1
3.8
Echinacea and raspberry
3.5
13.4
3.6
Blackcurrant, ginseng and vanilla
3.5
14.9
5.1
Raspberry, cranberry and elderflower
3.2
23.4
9.0
Raspberry, strawberry and loganberry
3.2
20.0
9.1
Camomile
7.1
**
**
Traditional blackcurrant
3.2
23.5
9.6
Traditional lemon
3.7
19.9
2.2
Peach and passion fruit
3.5
16.0
6.4
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3.3
60.3
9.3
Orange juice
3.7
21.4
3.3
**Unable to measure
8.6 Tea concentrate Tea concentrate refers to a product derived from concentrated tea extract, which is diluted with water to form a drinkable tea beverage. Tea beverage comprise about 0.4–0.8% tea solids. The tea concentrates can be in liquid form but are preferably in solid form. A patent (US 6,413,570) assigned to Lehmberg et al (2002) [82] describes tea concentrate. This patent relates to concentrated solutions or dispersions of tea extracts, which may be used in preparing iced tea beverages. Hot-tea beverages may also be prepared using this method. A brewed tea concentrate contains 5–30% tea solids, combined with selected carbohydrates in a ratio of 1.5 parts or more of carbohydrate to 1 part of tea solids. This concentrate contains caffeine, flavonoids and gallic acid on dilution to a final tea beverage at a ratio of about 100 parts water to 1 part tea contains a total tea solid content of about 0.1–3% or higher. The beverage thus prepared has a Hunter haze of 50 or less. In order to achieve the shelf-stability of tea concentrates, selected amounts of carbohydrates such as sucrose, corn syrup, oligosaccharides, high fructose corn syrup have been employed. Tea extracts from continuous or batch extraction using specific, enzyme treated or extracted tea leaves are centrifuged and separated to achieve certain levels of clarity. The carbohydrate can be added either before or after evaporation and preferably after to achieve a final concentration of 12–20% (w/w) on tea solids basis of the concentrate. The stabilized concentrate is pasteurized, acidified to a pH below 4.6, aseptically packed or preserved and stored at ambient temperature. Products made from the concentrate have fresh brewed tea flavour and good clarity.
8.7 Packet tea Packet tea continues to be popular with the older generation who are reluctant to switch over their preference to other tea types. Packet tea is a non-conventional item of export. It was introduced in 1920s and associated with the conventional appeal of tea. Leaf tea possess a distinct aroma and is being packed in laminated pouches, lined cartons for unit packs while for bulk packaging corrugated fibred board (CFB) boxes, lined cartons, tea chests, laminated multi wall sacks are being used. One of the main reasons for developing wraps is absorption of moisture and consequent bulging of the tea out of the packet. Fully fired tea will reduce the bulking effect. With the introduction of flexible films, the
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tea packaging has reached to the new dimensions because the trend in unit packaging has shifted to flexible laminates and plastic films. For tea drinking people the instant tea was not giving the traditional appeal. India exports the packet teas to more than 25 countries and this adds to the revenue. The Union Government levies excise duty on packet tea above 100 g. Demand for tea is highly price sensitive, and consumers tend to shift to relatively cheaper varieties of loose tea, when a price of branded/packaged tea rises. The levy of excise has a negative impact and witnessed a decline in consumption of branded tea segment [83].
8.8 Carbonated bottled tea The basic industrial methods for the manufacture of carbonated tea beverages include mainly two, which are described below.
8.8.1 Method one Black tea is extracted with hot water and the extract is mixed with sugar, acid, preservatives, etc. (Figure 8.7). Then the product is filled in the clean and sterilized bottles, carbonated and hermetically sealed [84]. Black tea Hot water Hot water extract Sugar
Acids, preservatives Bottling in clean bottles
Sterilized bottles
Carbonation
Sealing Figure 8.7 Carbonated bottled tea manufacturing method one
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8.8.2 Method two In this process, sterilized water, the acid, sugar, preservative, etc, are mixed in this order and poured into each bottle (Figure 8.8). Thereafter the tea concentrate is added in each bottle followed by carbonation and sealing of the bottles [84]. Hot water
mixed with acid, sugar pres ervatives etc.
Sealing
Carbonation
filled in clean, sterile bottles
Add tea concentrate to individual bottle
Figure 8.8 Carbonated bottled tea manufacturing method two
8.9 Flavoured tea In many countries whenever the delicate aroma of tea cannot be easily produced, there is a trend to produce scented/flavoured tea (Figure 8.9). In this process certain delicate flavours already present in the tea are accented. It is the product of tea obtained by incorporation of natural or natural identical or synthetic flavours to black, green or decaffeinated tea. The addition of other aromas is in practice, like addition of bergamot oil in small amounts in black tea [57].
Natural flavours These are the chemicals, i.e. defined materials with flavour characteristic produced by suitable physical procedures including distillation and extraction with solvents with the help of microbiological and enzymatic procedures, from raw materials with animal or vegetable origins.
Figure 8.9 Flavoured tea
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Nature identical flavours These are chemicals with characteristics of natural flavour molecules, produced by chemical synthesis or by isolation from different sources, e.g. vegetable or animal origin in the meaning of natural flavours.
Flavour extracts These are concentrated and non-concentrated products with flavour characteristics produced by suitable physical procedures, viz. distillation and extraction with solvents, with the help of microbiological and enzymatic procedures.
Maillard flavours These are products under the observance of honest producer practices by the usual procedures, such as the heating of a mixture of raw materials, of which at least one contains nitrogen group and sucrose, for a maximum of min at a temperature of not more than 180°C.
Smoked flavours These are preparations of smoke, which are used in the usual procedures for the smoking of foods [85].
8.9.1 Methods of incorporation of flavours (a) Flavouring tea extract (soluble/Instant tea), (b) flavour incorporation into tea bags, (c) diffusion method, (d) spray method / sprinkling, (e) heating/ firing (Poey process – warm tea leaves and flowers), (f) using encapsulated flavours, (g) addition during brewing stage and (h) aromatisation using β-cyclodextrins Flavour tea production – tea leaves of all kind are highly receptive to liquid flavour. Not only liquid flavours work well, but also dry granule flavours are successfully used in tea packaged in teabags. The granule flavours are not recommended to loose leaf tea. However the granule flavour slowly releases the flavour through the tea bags, during the steeping process. Two different large-scale production methods for flavouring teas are available; both of these methods have uniform distribution of flavour. The first method involves applying the flavour to the tea mixer or bin. The flavour should be added slowly, while the tea is continuously tumbled. The leaves should be exposed to the flavour; the tea should be spread out on a clean,
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dry surface for drying. The drying process lasts for 10–20 min, depending on the surface area of the tea exposed to the air and the quantity of tea being flavoured. The second technique is suited to larger quantities and the tea is flavoured via the use of a manual or electrical sprayer. The tea should be spread out over a clean, dry surface and the flavour sprayed over the leaves. The flavoured tea leaves should then be allowed to dry for 10–20 minutes. For both flavouring methods, the flavoured dry tea leaves are kept in a covered bin or container for a day or two to fully develop the combined aroma and taste. Incorporation of lemon flavour for tea in tea bags consists of a compressed intimate mixture of a major amount of solid food grade acid, a small amount of hardening agent such as starch hydrolysate, a flavouring agent such as glycerin. The preparation of lemon-flavoured tea bags has also been reported. The flavouring composition consisted of lemon oil, hydrogenated vegetable oil and crystalline sugar. Bhattacharya [84] described the incorporation and stability of selected flavouring compounds, viz. citronellol, phenyl ethyl alcohol, citral and bergamot of reminiscent of these popular varieties of flavoured teas viz. rose, lemon and early grey in CTC black teas. Their storage characteristics were studied at three temperature conditions of 5°C, room temperature and 37°C using laminated aluminium foil, metal can and metallized polyester as packaging materials for a period of 90 days. Significant linear correlations were established between the instrumental and sensory values. Researchers at CFTRI, India, have developed early grey (bergamot), jasmine, ginger and mint flavour blends for flavouring orthodox BOP fannings grade teas. A prototype flavouring system has been developed for the manufacture of 800 kg of each per day of selected varieties of flavoured teas (Figure 8.10). Flavour blends + raw material Flavour application system Drying
Solvent
Canning Packaging Figure 8.10 Flavoured tea manufacture
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8.9.2 Jasmine tea Scented tea is a reprocessed tea made with the addition of fragrance of fresh flowers. Jasmine tea, a scented green tea, is the main product in Fiian and Zhejiang provinces of China. Scented teas are made with green, oolong, black and other varieties of teas. Type of fragrance of tea is determined using the flowers added such as jasmine, magnolia, rose, pomelo, deidal, chloranthus, osthamsthus, etc.
Preparation of flowers Buds are picked and immediately spread out in a well ventilated, hygienic room, away from direct sunlight. Flowers are piled 20–30 cm depth at about 34°C. If the temperature is higher, the pile is made less depth. Care must be taken to avoid damage of flower buds. When the flowers are opened 60–70%, they are sifted to remove unripe buds and impurities. Vibrating during sifting helps the flowers to open. When the flowers are open, the flowers are mixed gently, but quickly, with tea leaves. Care is taken not to injure the flowers and to prevent them from turning red and losing their fragrance. The mixture of tea leaves and flowers are piled 30–50 cm depth for 8–12 h at 38–44°C to allow the tea leaves to absorb the fragrance of the flowers. If the temperature becomes too high, the mixture is turned over for cooling to prevent the flowers from withering too quickly. When the tea leaves have fully absorbed the fragrance, the mixture is sifted and the flowers, which have withered and turned yellow, are separated from the tea leaves. The tea leaves with flower fragrances are dried at about 100°C, 2 cm depth, for 8–10 min to moisture content of 7–8%. The fragrance tea leaves are spread out to cool until the leaf temperature is below 35°C and then immediately stored in boxes for blending in traditional processing; the moisture content was maintained below 9%, which required firing and drying. However, recent research has shown that tea leaves do not dry before adding fragrance and contain over 9% moisture, and yields a betterquality tea. Elimination of extra drying step lowered the costs, simplified the procedure, and yielded a better product. Care must be taken that the final drying after fragrance that has been added is not excessive, to ensure that the fragrance is not lost. The final product is produced by blending 1–2% of dried flowers to the tea leaves processed with added fragrance [17].
8.9.3 Flavoured tea beverage Cirigliano et al [86] explained the use of flavouring materials in tea beverages. These also contain sufficient amount of a selected substituted phenyl flavouring/antimicrobial compound to prevent microbial growth
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while simultaneously contributing to the pleasant flavour of the beverage. This beverage is acceptable both organoleptically and microbiologically. This beverage contains a non-halogenated flavouring/antimicrobial compound (20–2000 ppm) and comprises about 0.02–0.5% tea solids by weight. Optionally selected hurdles or step-wise antimicrobial controls are employed. The steps include employing water having a very low hardness; using a pH of about 2.5–4.0; using selected sequestrants; with the pH and water adjustments, using selected polyphosphates; and using selected wellknown preservatives such as nisin, natamycin, sorbic acid and sorbates and benzoic acid and benzoates together with the low water hardness, the pH adjustment, sequestrants and polyphosphates. Together these steps contribute to the antimicrobial effect. Each of these steps produces at least incremental and frequently synergistic antimicrobial effects. None of them however contribute positively to the overall delicate flavour of the tea beverage; rather all of the steps taken are done to improve microbiological stability without negatively affecting the flavour. Thus, the antimicrobial effect must take into account the flavour profile of the tea [86].
8.10 Decaffeinated tea The major object of decaffeination tea is removal of caffeine. Excessive consumption like 1.5–1.8 g of caffeine can lead to caffenism which causes anxiety, neurosis condition, restlessness, irritability, insomnia, twitches, palpitations, nausea, vomiting, diarrhoea, headache, late onset of sleep, etc. Doses of 100 mg/kg body weight cause serious poisoning hazard in children. The signs of poisoning are agitation, convulsions, tachycardia, etc. and coma with death from cardio pulmonary arrest. The others effects include (a) ulcers tea stimulates the gastric mucosa and increases secretions of stomach and exacerbating existing ulcers, (b) calcium loss in long run cause osteoporosis [15]. Hence, decaffeination is suitable step to over come these ill effects for the caffeine containing beverages. The general methods for decaffeination of tea are solvent as well as super critical solvent extraction, liquid–liquid extraction, oil/fat phase extraction, water decaffeination and microbial degradation. Methylene chloride is the only chlorinated solvent used from 1976. For tea, ethyl acetate and super critical CO2 are allowed presently. Solubility between methylene chloride and water at 80°F is virtually linear from 0.1 to 1.0%. There are four steps involved in the procedure: (1) steaming increases moisture content from 10 to 40%. (2) The tea is treated counter currently with an organic solvent for 12 h to extract 97% of the caffeine. (3) The tea steamed with live steam to remove all of the residual solvent. (4) The excess of moisture is removed by air or vacuum drying.
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Process of decaffeination of tea using super critical gas is presented in Figure 8.11 [15]. Aroma extraction of leaves (Dry food grade CO 2 gas) Separate the extracts (reducing the pressure and increasing temperature) Tea leaves extraction in H2 O Spray/freeze dried Figure 8.11 Decaffeination of tea powder by super critical gas
8.10.1 Decaffeination of fresh green tea leaf by hot water treatment Hot water treatment was used to decaffeinate fresh tea leaf. Water temperature, extraction time and ratio of leaf to water had a statistically significant effect on the decaffeination. When fresh tea leaf was decaffeinated with a ratio of tea leaf to water of 1:20 (w/v) at 100°C for 3 min, caffeine concentration was decreased from 23.7 to 4.0 mg/g, while total tea catechins decreased from 134.5 to 127.6 mg/g; 83% of caffeine was removed and 95% of total catechins was retained in the decaffeinated leaf. It is considered that the hot water treatment is a safe and inexpensive method for decaffeinating green tea. However, a large percentage of tea catechins were lost if rolled leaf and dry tea were decaffeinated by the hot water treatment and so the process is not suitable for processing black tea [87].
8.11 Fortified tea An approach to fortification will be able to fortify the tea beverage with nutritious and energy-giving materials. This can be achieved by incorporation of various cereal-based materials and proteins. There are various patents concerning the fortification of tea with cereals. A patent assigned to Hatsuzawa [88] describes the fortification of tea with a combination of roasted barley and caramel from roasted sugar. A barley tea of improved flavour is obtained. Another patent assigned to Horie Food Co. [89] describes barley tea production in which roasted barley grains are leached to obtain their vitamins, which are added to barely tea in bottles and heat sterilized.
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8.11.1 Vitamin A fortification Vitamin A deficiency leading to keratomalacia is one of the chief causes of preventable blindness in young children. Incidence of keratomalacia is high in the 1–3 year group. The cheapest method to meet the deficiency would be to use synthetic vitamin A for fortification of foods. A major problem in establishing fortification programs to meet known deficiencies in essential nutrients is to select a suitable vehicle. Studies of food-consumption patterns and consumer habits in India [90] have shown that compare to all other food products tea is consumed by young and old, rich and poor, in both rural and urban areas. Tea comes close to being the ideal vehicle for converting vitamin A to millions of Indians of all ages whose diet is seriously deficient in vitamin A. Buxton and Lipsius [91] described the fortification of brewed tea with ethanol solution of vitamin A in their patent. Beverage from tea dust is consumed by 65% of the population in India. It is quick brewing and produces a darker, stronger brew. Tea dust was fortified by dry mixing the dust with fine powdered vitamin A palmitate, and it contains 250,000 IU of vitamin A per gram. The fortified tea dust retained 85% of the vitamin A activity for 1 year at room temperature. Tea leaves were fortified using emulsions of vitamin A palmitate and acetate. Tea emulsions were made homogenizing the vitamin A into acacia or dextrin solutions at 500,000 IU/g. These emulsions are 100% stable for 1 year at 24°C but are too concentrated to be used directly. The emulsions diluted in water and in 20% dextrin solution showed unsatisfactory stability during storage. Vitamin A emulsions diluted in 50% sucrose solution and sprayed on tea resulted in satisfactory stability. Vitamin A palmitate applied in both the powdered form and emulsion form showed 100% retention after 1 h of boiling. Laboratory testing proved that tea dust or tea leaves can readily fortified with vitamin A will be stable even during a 1 h of cooking period [92].
8.11.2 Thiamine fortification Stagg and Millan [27] reported that black tea contains a relatively low level of thiamine (13 µg/g). Further, it has substantial antithiamine activity, which has been attributed to the high levels of tannins [93, 94]. They have identified tea as a direct cause of thiamine deficiency in a group of people from the Chieng mal region of Thailand, an area with a history of infant beriberi [95]. Here, all age groups of the population consume tea. Thiamine status of the people was improved when tea was removed from the diet. It is difficult to alter the eating habits of populations but an alternative, to discouraging tea intake, could be to fortify the tea with thiamine.
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Thiamine hydrochloride was added by spraying an aqueous solution onto the commercial black tea leaves with an aerosol gun at the rate of 2 ml solution to 20 g of leaves. The treated leaves were allowed to dry in air before storage at 30°C. A tea infusion was prepared in the following way – adding tea leaves (1g) to purified water (50 ml) at room temperature, and heating the mixture to 85° or 95°C in a water bath. The mixture was then filtered for the tea leaves, and infusion analysed for thiamine content. About 20% of thiamine was present in the solution after 2 min brewing while after prolonged infusion 40% was present. The amount of thiamine present in the solution is the result of a dynamic equilibrium established between the solubilisation of thiamine from the leaf surface and destruction of thiamine by anti-thiamine factors in tea and heat degradation of thiamine. Tea leaves sprayed with thiamine and stored at 30°C in glass jars showed a substantial loss of thiamine during storage but the rate of decline appeared to diminish sharply after seven weeks about 50% of the added thiamine had degraded (Table 8.6). Study by Wills and Dwyer [96] showed that it is possible to apply thiamine to tea leaves and produce a tea infusion with sufficient thiamine to be of nutritional significance without affecting the colour and flavour of the beverage. A patent by Henry et al [97] on tea fortification with iron discloses the composition of fortified tea beverage (Table 8.7). Table 8.6 Effect of storage of thiamine-sprayed tea leaves on recovery of thiamine from infusion liquor
Time (weeks)
% Thiamine in solution
% Loss due to storage
0
55
0
2
42
24
7
26
52
14
24
56
Note: Thiamine was added to the leaves at 0.24 mg/g; the leaves were infused at 85°C for 30 min. Table 8.7 Composition of fortified tea beverage with iron
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Ingredients
Percentage
Tea solids
0.79
Sugar
4.72
Citric acid
0.10
Ascorbic acid
0.04
Ferrochel
0.01
Water
94.35
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8.12 Tonic tea To improve organoleptic, tonic and therapeutic properties of the tea leaves, tonic beverage is made. It is non-alcoholic tonic beverage basically made by extracting tea leaves, clarifying the extract, blending and carbonating. A patent assigned to Ru [98] describes a process in which tea leaves are divided into two parts, one fraction is ground and fermented followed by extraction with 20% ethanol solution in a ratio of 1.3–1.5. Other fraction is stabilized with 0.5–5.0% aqueous solution of citric acid followed by extraction with 0.03–0.8% aqueous solution of citric acid in a ratio of 1.3–1.6 for 10–30 min at 95–100°C. This is followed by clarification and mixing of the resultant extracts in a ratio of 1.1–1.5.
8.13 Tea cider Tea cider is not entirely new; it has been brewed for some decades, but largescale consumption has not been exploited for a variety of reasons. Tea cider is a fermented alcoholic tea beverage. The essential process involved in the production of any alcoholic beverage is the breakdown or fermentation of a carbohydrate, in this case sugar to carbon dioxide and alcohol. The ferment has more than one organism; only two organisms are of importance – yeast, Saccharomycodes ludwigii and a bacillus Bacterium xylinum. It is however possible that other species of Saccharomycodes may also be responsible for the production of satisfactory brew. The ferment is grown on the medium used for the preparation of cider. The medium supports the growth of unwanted microbes as contaminants, so the media should be sterilized and fermentation should be carried out in aseptic conditions.
8.13.1 Preparation of cider and vinegar Black tea of 25 g quantity is infused in 330 ml of freshly boiled water for 3–5 min. Infusion is filtered and 200–300g of sugar is added before it gets cooled. The sugared tea is covered and cooled to room temperature. Float the ferment on the sugared tea if necessary using a clean disc of cork under the ferment. The vessel must be kept covered but not airtight or hermetically sealed. The fermentation is allowed to proceed for 2–5 days depending on the temperature. The higher the temperature, the faster will be the fermentation. The brew should not be artificially heated. The cider should be tasted periodically in order to fix the time at which the ferment should be removed. Then the ferment is removed on reaching the desired taste, filtered through a double layer of linen. The bottles are filled to the brim and stopper the bottles securely and stored in a cool place. In case of vinegar, after removing the ferment do not bottle
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the brew but instead let the brew stand in the vessel for about 1 month. Strain the vinegar, boil it and then bottle it. The cider is alcoholic, and although its alcohol content would be only about 1%, its sale would be naturally comes under the provision of exercise ordinance [99].
8.14 Tea kombucha Kombucha tea (Figure 8.12) is a refreshing beverage obtained by the fermentation of sugared tea with a symbiotic culture of acetic bacteria and fungi, consumed for its beneficial effects on human health. The first apical leaves are picked from the evergreen shrub and can be processed by different methods. Green tea is readily dried to inactivate enzymes [100]. Black tea, the most popular form around the world, is the result of the oxidation of leaf polyphenols through a multi-stage enzymatic process [101]. Black tea and white sugar are the best substrates for the preparation of Kombucha, although green tea can also be used [102]. Tea leaves are added to boiling water and allowed to infuse for about 10 min after which the leaves are removed. Sucrose (50 g/l) is dissolved in the hot tea and the preparation is left to cool. Tea is poured into a wide-mouthed clean vessel and is acidified by the addition of vinegar or already-prepared Kombucha. The tea fungus is laid on the tea surface, and the jar is carefully covered with a clean cloth and fastened properly. Tea preparation is allowed to incubate at room temperature (between 20° and 30°C) for 1–8 weeks. During fermentation, a daughter tea fungus is formed at the tea surface. The tea fungus is removed from the surface and kept in a small volume of fermented tea. The beverage is passed through cheese-cloth and stored in capped bottles at 4°C. The taste of the Kombucha changes during fermentation from a pleasant fruit sour-like lightly sparkling flavour after a few days, to mild vinegar-like taste with prolonged incubation [103, 104].
Figure 8.12 Tea kombucha
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The main acetic acid bacteria found in the tea fungus are Acetobacter xylinum [105], A. xylincides, Bacterium gluconicum, A. aceti, and A. pasteurianus [106]. Yeasts are identified as Schizosaccharomyces pombe. Saccharomycodes ludwigi, Kloeckera aciculata, Saccharomyces cerevisiae, Zygosaccharomyces baili, Brettanomyces bruxellensis, B. lambicus, B. custersil, Candida and Pichia species [105, 106]. The main metabolites identified in the fermented beverage are acetic, lactic, gluconic and glucuronic acids, ethanol and glycerol [104, 106]). It is also reported that the fermentation process induces the synthesis of the vitamin B complex and folic acid [107]. The pH value of Kombucha decreases during the fermentation process following the increase in the organic acid content [104]. Many benefits for health have been reported based on observations and testimonials [108]. Kombucha regulates intestinal activities often disturbed by the lifestyle in the army [109]. Between 1925 and 1950, several medical studies conducted by doctors and physicians confirmed the traditional claims about Kombucha and reported beneficial effects such as antibiotic properties, regulation of gastric, intestinal and glaridular activities, relief of joint rheumatism, gout and haemonholds, positive influence on the cholesterol problems [109]. In 1951, important population study conducted in Russia by the “Central Onchological Research Unit” and the “Russian Academy of Sciences in Moscow” found that the daily consumption of Kombucha was correlated with an extremely high resistance to cancer. In 1960s, researches reaffirmed the cancer healing properties of Kombucha, its detoxifying effects and proposed that a long-term consumption increased the immune system performance and boosted interferon production. A recent study reported the antibiotic activity of Kombucha against Helicobacter pylori, Escherichia coli, Staphylococcus aureus and Agrobacterium tumefaciens mainly related to the acetic acid produced during the fermentation [110]. Tea extracts used at the same concentration did not exhibit any effect. Its detoxifying property is presumably due to the capacity of glucuronic acid to bind to toxin molecules and to increase their excretion from the organism by the kidneys or the intestines. Gout, rheumatism, arthritis or kidney stones produced by the accumulation of toxins in the body may be relieved this way. Heavy metals or environmental pollutants can also be excreted through the kidneys after glucuronidation. It was reported that patients suffering from cancer do not have l-lactic acid in their connective tissues and have a blood pH higher than 7.50. Kombucha can re-equilibrate the blood pH and the lactic acid concentration. The laxative activity of Kombucha is also attributed to its lactic acid content [107]. The tea fungus is also used for medical purposes in skin therapy. The cellulosic pellicle formed mainly by Acetobacter xylinum during the fermentation of tea has been used as a temporary skin substitute on burns and in other skin injuries [111].
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Although the consumption of Kombucha generally presents no adverse side effects, a few cases of health disorders have been reported. Upset of stomach, some allergic reactions, particularly for those predisposed to acid sensitivities, and renal insufficiencies are usually improved through ceasing or lowering consumption [112]. Mechanisms of adverse effects have not been elucidated. When taking Kombucha, it is recommended to drink plenty of water to facilitate the elimination of toxins and to adjust consumption to any body reaction [113]. When Kombucha is home cultivated, because fermentation is conducted in non-aseptic conditions and the culture is often propagated from one house to another, the potential for contamination is high [114]. Contaminations are always possible but the zooglea protects itself against foreign microorganisms [114]. Penicillium spp and Candida albicans were identified in home-cultivated tea fungus but no pathogenic bacteria have been found [115]. Enthusiastic supporters often claim Kombucha as a remedy for everything and a miracle elixir. Allegations are numerous and varied. The list includes the elimination of gray hair, the increase of sex drive, and the improvement of eyesight, to the utilisation as a household cleaner, underarm deodorant or soothing foot soak [116]. The scientific literature revealed a lack of evidence to support many of these claims and raised doubts as to the validity of others. More research is needed to evaluate Kombucha, but there are new reasons to think that it may have a positive effect on human health. Findings about the beneficial effects of tea and fermented tea of health are meaningful because of the popularity of these beverages around the world. Two species of acetic acid bacteria and three species of yeast were isolated from tea fungus (Kombucha) using appropriate isolation media. The isolated bacteria were identified as Acetobacter aceti and Acetobacter pasiteurianus, based on their biochemical properties, and compared with those of the type strains of the genus Acetobacter. The yeasts were Saccharomyoes cerevisiae, Zygosaccharomyces bailli and Brettanomyces bruxellensis, according to conventional phenotypic characterisation combined with the yeast identification program. The brew broth analysed by high-performance liquid chromatography (HPLC) was shown to contain glycerol, acetic acid and ethanol. The symbiosis phenomenon between the yeast and Acetobacter was studied. It was found that the autoclaved yeast cells and ethanol produced by yeasts were helpful for Acetobacter to grow or produce acetic acid. The acetic acid produced by Acetobacter could stimulate the yeast to produce ethanol. The ethanol and acetic acid produced by yeasts and Acetobactor might prevent the competition from other microorganisms [106].
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8.15 Toyoma kurocha Toyoma kurocha is a tea that is microbial fermented by a natural fungus, which is only native to Japan. It is consumed specifically on religious occasions or during meetings in the Asahi area in Toyama prefecture. This tea is traditionally prepared to drink by boiling with water, adding salt, and stirring with a tea whisk as in tea ceremony. Toyoma kurocha is classified as piled tea based on the following manufacturing process as shown in Figure 8.13: steaming, rolling, fermenting in a wooden frame (150×180×90 cm) with a straw mat for 20–25 days, and solar drying for 2 days. The low water content of Toyoma kurocha (66.5%) during fermentation causes fungal fermentation, compared to Awa cha, a pickled tea with a water content of 76.1%. Aspergillus niger is the predominant microbe in Toyoma kurocha manufacturing. Volatile phenolic compounds have also been reported as characteristic component in this microbial fermented tea. The precursors of some of these volatile components seem to be ferulic acid and p-Coumaric acid, based on their chemical structures. Tea leaves Picking in late July Steaming, 30 sec onds Steamed tea Rolling, 10 min utes Fermenting, 20 –25 days Fermented tea Solar drying, 2 –3 d ays Toyoma Kurocha Figure 8.13 Manufacturing process of Toyoma kurocha
8.16 Canned tea Tea is one of the oldest and most favourably consumed beverages around the world. Tea is generally categorized into 3 major groups – green tea, oolong tea, and black tea depending on the degree of fermentation of tea leaf. The tea species, cultivated region, processing method and various other factors significantly contribute to the formation of delicate sensory characteristics of tea. Green tea, which is not fermented, is characterised by its fresh green and astringent flavour due to aldehydes, alcohols, and polyphenols. Semifermented oolong tea tends to have stronger burnt, roasted flavour compared
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to the other 2 types of tea. Completely fermented black tea has sweet, floral, and citrus characteristics as a result of volatile flavour compounds formed during enzyme-oxidation, Strecker degradation and Maillard reaction from the precursors in tea leaves. As the growth of the beverage industry enables the massive production of tea products, the market for canned tea products has expanded rapidly during the past few years and now shares a large proportion of the Korean beverage market. The types of canned tea products sold are black tea, oolong tea, and green tea. The findings of various health benefits of tea compounds have led to a general consumer’s appreciation for the functional properties of tea products. Thus, tea is consumed not only to satisfy consumers’ fine taste buds but also to acquire health benefit. If the sensory characteristics of a product were the major drivers that determined the product acceptance in the past, nowadays non-sensory factors such as health functional ingredients, product concept, and processing methods have emerged as additional significant factors affecting consumers’ acceptance. The preference for a product varies widely among consumers. The consumer hedonic score is regressed against the sensory dimension of products, thus providing the information of key sensory attributes that drives consumer liking for a product. Table 8.8 show different types of canned tea products available in market and these are having higher degree of consumer acceptance based on sensory analysis. Green tea with brown rice flavour and functional ingredients provides health benefits. Table 8.8 Various categories of canned tea and their attributes [117]
Category
Additional ingredients
Green tea
Brown rice flavour
Green tea
Brown rice flavour with functional ingredient
Black tea
Lemon flavour
Black tea
Milk powder
Overall, black tea type canned product was most widely accepted to the general consumer group. The acceptance for green and oolong type canned beverage dependent not only on the sensory characteristics of individual products but also on age and information. Therefore, to understand the acceptance of a product, especially for products those are consumed for taste as well as for health benefit, the sensory characteristics of the product along with the ethno-background of the target consumer must be precisely understood. Then the canned tea will fetch a better marketability and acceptance in consumer’s forum [117].
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8.17 Instant tea granules Instant tea is presently manufactured by spray/freeze drying of the concentrated brew of processed tea leaves/dust and the drawbacks of this method are inferior quality, high cost and energy (Figure 8.14). A novel technique has been developed for the production of instant/soluble tea powder from the expressed juice of green leaves. After plucking, the leaves are crushed and juice pressed out. The juice is then subjected to fermentation under specified conditions. The fermented juice is steamed, centrifuged and freeze-dried to get instant tea powder. The pressed leaf residue is subjected to fermentation and drying for preparation of tea granules. The instant tea produced is of good liquoring characteristics and various constituents are also in the acceptable range [Theaflavin (TF) to Thearubigin (TR) ratio – 10.71 for instant tea (IT) and 12.12 for tea granules (TG), caffeine content 40.4 mg/cup of IT and 96 mg per cup of TG]. The tea granules produced is comparable to CTC (crushing, tearing and curling) tea in quality and liquoring characteristics. There is considerable savings in the economy as the juice and residue are converted into value-added products in this method [118]. Fresh tea shoots Crushing; Pressing Tea extracts Fermentation (Oxygen) Heat treatment Centrifugation Freeze drying Instant tea
Pressed leaf residue Fermentation Drying Tea granules
Figure 8.14 Process of manufacture of soluble tea powder and tea granules
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9 Tea by-products
9.1 Introduction It was estimated that 2–4% of black tea produced is wasted every year, which cannot be further processed for consumption. To make tea-producing operations economically viable, attempts should be made to utilise the tea waste. Numerous tea plantations in different parts of the world are shifting from seed Bari cultivation to clonal propagation techniques. The seed Bari gardens produce and will continue to produce for years to come significant quantities of tea seeds which may go waste. The literature shows that research and development efforts are centred on the following by-products for utilization of tea waste: (a) caffeine, (b) polyphenols, (c) pigments, (d) triacontanol, (e) tea seed oil and saponins and (f) extender in plastics.
9.2 Caffeine Tea waste contains 1.5–3.5% caffeine (Figure 7.3). It is used largely in pharmaceuticals, apart from its pharmacological properties caffeine is also an essential ingredient of carbonated beverages. Methods of manufacture permit the recovery of caffeine from tea waste with the exclusion of the tea polyphenols [57]. Methylene chloride, ethyl acetate, chloroform, carbon tetrachloride, trichloroethylene, benzene, alcohols, and various mixtures of these have been used for the extraction of this alkaloid [119]. Two general methods are used for the extraction of caffeine. The first method involves the denaturing of tea wastes with lime or alkali, extraction with solvents, and evaporation of the solvent followed by extraction with hot water, purification and crystallization (Figure 9.1). In the second procedure the denatured tea waste is extracted with hot water, followed by transfer of caffeine to any of the immiscible solvents
147
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like methylene chloride, ethyl acetate, concentration of the organic phase, purification and crystallisation. Another process called pilot-scale process, was developed of which the details were published [120, 121]. Damayanthi et al [122] reported efficient extraction of caffeine from denatured tea wastes by water. They found that 1,1, 2,2-tetrachloroethane was ideally suited for the removal of caffeine from tea infusions. Tea wastes
Heating with lime water
Release of bound caffeine
Extraction with solvent
Extraction with hot water
Purification
Crystallization Figure 9.1 Process of extraction of caffeine
9.2.1 Uses of caffeine Caffeine is a well-known drug useful as a stimulant of the central nervous system and is also used as a diuretic. It is commonly used in analgesic and antipyretic tablets, and in stimulant beverages. Besides its direct use in pharmaceuticals, caffeine forms the starting material for the manufacture of Theophylline, Aminophylline and Bramanine.
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9.3 Polyphenols Polyphenols of tea waste mainly comprise theaflavins, thearubigins and catechins (Figure 7.1) and these constitute 10–15% of the black tea extractives. Since several of these compounds are themselves gallocatechins and catechingallates, they can be potentially used as antioxidants in food systems. For example, (−)epigallocatechin gallate and other polyphenols separated from black tea infusions have shown strong antioxidant activity towards the oxidation of linoleic acid [123]. The lauryl and benzoyl derivatives of tea polyphenols compare well with commonly used food antioxidants such as n-propyl gallate, butylated hydroxyanisole and butylated hydroxytoulene in extending the shelf life of vegetable oils such as ground-nut oil, linseed oil and hydrogenated fat [124].
9.3.1 Polyphenol extractives – food use The effect of alcoholic extracts of old tea leaves (OTL: 5–8 leaves of the shoots) on the stability of rape seed oil during heating at 60°C and deep-fat frying of potato crisps at 180°C was determined. The OTL extract (Figure 9.2) was effective in retarding oil deterioration at 60°C, and activity increases with concentration in the range 0.02–0.25%. At a concentration of 0.25% the OTL extract (0.1%) was as active in retarding the deterioration of oil as a rosemary extract (0.1%) during the repeated frying of potato crisps. Hence, it is clear that old tea leaves, which at present are often considered as agricultural waste contain antioxidants that may usefully be extracted and added to foods [125].
Figure 9.2 Polyphenol conserve
9.3.2 Polyphenol extractives – non-food use The phenolic content of tea leaves and their abundance as residual waste at tea producing factories warranted studies on the utilization of these wastes
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in particle board manufacture. Waste tea leaves particle board (WTLB) is expected to be more resistant against biological agents owing to high phenolic content. Mass loss of WTLB, the edges of which had been sealed with an epoxy, was 3.5–8.6% and 6.0–12.1% for paraffin added and non-added specimens respectively, following degradation by Tyromyces palustris and Coriolus versicolor. The addition of paraffin to binder during the manufacturing of the board and the sealing of the edges of specimens before decay testing, kept degradation to a minimum. Mass loss of WTLB after exposure to Formosan subterranean termite Coptotermes formosanus was around 16%. However, termite mortality levels after the three weeks of termite attack suggested that phenolic extractives of tea leaf act as natural toxicants. Physical and mechanical properties of WTLB indicated that it performs as the general purpose boards designated in BS 5669 [126].
9.3.3 Tea catechin products Two series of green tea extracts, PolyphenonesTM and Sain-catechinsTM, are utilised commercially for various purposes. Polyphenones are the extracts of green tea, composed mainly of catechins without any material other than those of green tea. Sain-catechins are dilutions of polyphenones with large amount of liquid, water or oils [4].
Examples of products with Polyphenols Catechin 100 For easy consumption, Polyphenon 70S is produced in a capsule form of 100 mg of catechins per capsule. This capsule is marketed under the name Catechin 100TM. Catechins exert a multitude of beneficial effects in the body from the time of their oral intake to the time when they are excreted. In the oral cavity, catechins prevent various oral airway infectious microbes as well as the influenza virus. Catechins suppress not only the growth of carious bacteria but also the formation of dental plaque. Esophageal and stomach cancers are likely to be less among heavy tea drinkers who ingest a lot of catechins. After the intake of seven capsules of Catechin 100 every day for a month, out of 34 people who were infected with Helicobacter pylori, six people were proved to be free from the bacteria. H. pylori live in the mucous membrane of the stomach and causes atrophic ulcer and may ultimately cause stomach cancer. In the small intestine, catechins inhibit such digestive enzymes as α-amylase and sucrase, thus, preventing the over ingestion of saccharide. Catechins were also proved to suppress the ingestion of lipid by inhibiting the emulsification of lipids. Animal experiments showed, however,
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there will not be any malnutrition by the intake of catechins. It seems that only in the case where extra nutrients are taken, catechins work to inhibit the over ingestion. Thus, catechins are safe and natural dieting agent. Many animal experiments show the suppression of carcinogenesis by catechin intake in the small intestine and colon in particular. A trace of catechins absorbed into the vein from the small intestine is metabolized in the liver and works to suppress carcinogenesis in the liver, lung, spleen or bladder, according to the animal experiments. Catechins in the human bloodstream are likely to suppress the peroxidation of LDL Cholesterol, thus, lowering the chances of oxidative degradation of cardiovascular circulation systems. Most of the catechins consumed pass through the colon unabsorbed and are excreted. Catechins were proved to exert very favourable effects on the intestinal flora, increasing lactic acid bacteria and decreasing putrefactive bacteria. Very healthy bowel conditions were confirmed in humans by the administration of 3–9 capsules of Catechin 100 daily for several weeks. Various similar tea catechin capsules are sold in the U.S. health care market [4].
Catechin ACETM Though tea catechins works miraculously for the benefit of human health through their endeavour to fortify the beneficial effects, other desirable components may be included in catechin extract products. One such product is Catechin ACE in capsule form. Catechin ACE contains, in addition to 50 mg of tea catechins, 10 mg of Gingko biloba extract, 200 I.U. of vitamin A, 20 mg of vitamin C and 10 mg of vitamin E. Gingko biloba extract is known to facilitate the blood circulation. Vitamin A, E, C are the most representative antioxidant components in vegetables and fruits, and these each work synergistically with tea catechins to enhance antioxidant activity. One capsule exerts SOD (Super Oxide Disputes) like the activity of 28,000 I.U. For those who are under oxidative stress and are prone to vascular disorders, 6–12 capsules a day are recommended [4].
Catechin 100 Plus Obligate Very favourable modulation of intestinal flora by tea catechin was reported. In order to further enhance the bowel modulating actions of tea catechins, galactic-oligosaccharide was formulated with tea catechins to make Catechin 100 plus Olio, in the tablet form. Galactic-oligosaccharide is known to be a good nutrient for bifid bacteria in the intestine and to improve the condition of the bowel. Tea catechins work to inhibit the growth of putrefactive bacteria and do not interfere with bifid bacteria, thus resulting in a decrease of putrefactive bacteria and an increase of bifid bacteria or lactobacillus bacteria. In this way,
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the combination of tea catechins with galactic-oligosaccharide is the most ideal combination for improved health of our bowel. One tablet contains 50 mg of tea catechins and 40 mg of galactic-oligosaccharide. Daily intake of 6–9 tablets is recommended [4].
Bottled health drinks– β-Catechin Tea catechins are mixed with β-carotene and various other herbal extracts to enhance the scavenging actions against oxygen radicals. This concentrated mixture is contained in a small 50 ml bottle; it is a potent health drink that can be consumed daily [4].
Ant flu air purifier The remarkable effect of tea polyphenols in preventing the infection of influenza virus was utilised on the catechin air filter. The air purifier with catechin filter was developed with the collaborative research of National Panasonic and Mitsui Morin Company. Tea catechin (P-60) was impregnated in the air purifying filter by way of a special technique. The air purifier equipped with the catechin filter was proved to reduce the number of viruses sprayed on the filter from 200,000 to less than 10 in about six hours of ventilation, whereas on the filter not impregnated with catechin 170,000 viruses were counted. This was proved with the Coxsackie’s virus, which is much smaller and more resistant than the influenza virus. The catechin filter is fitted together with a charcoal filter and the electrostatic filter to the air purifier. The antiviral effect of the filter is guaranteed for a year of ventilation (8 hours/day). The filter is exchangeable and a new one can be fitted when the effectiveness wears off [4].
Ant flu mask A small piece of catechin air filter as manufactured above was fitted in a facial mask. This mask gave moderate protection from airborne contamination by viruses. Use of this catechin mask is recommended particularly at times when influenza is rampant, especially for older people when they go out in cold weather, since they are more susceptible [4].
Catechin candy Anticipating the same anti-flu effect as above, candies containing catechin have entered the market. Regulations do not allow claims concerning the efficacy but this knowledge may be spread widely. Similarly, catechin chewing gum is under development [4].
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Catechin eggs Tea catechins mixed in the feed of laying chickens produce eggs with uniquely favourable characteristics as compared with the conventional (non-catechin) ones. The change in the contents of total lipid, protein, sodium and cholesterol as well as the peroxide and calories are shown in Table 9.1. Table 9.1 Changes in the composition of Catechin Eggs versus Conventional Eggs (100 g)
Item
Catechin egg
Conventional egg
Calories (kcal)
125.0 (−37)
162.0
Protein (g)
11.2 (−1.1)
12.3
Lipid (g)
7.7 (−3.5)
11.2
Carbohydrate (g)
1.0 (+0.1)
0.9
Sodium (mg)
147.0 (+17)
130.0
Cholesterol (mg)
321.0 (−149)
470.0
Peroxide (mmol)
5.2 (−1.3)
6.5
*The values in the brackets are differences
Value in the yolk is quoted to be much lower than in conventional eggs. The Hough unit value, which indicates the height of the thickest part of the white of an egg, is higher in the catechin egg. These factors suggest that not only does the egg have health benefits for those who eat it but it is possible that if the egg was fertilized, these health benefits may be passed on to the chick. Several other interesting features are noted in the catechin eggs. The white of the egg is totally transparent and when whipped it is pure white in colour. No dark iron sulphide is present on the surface of the yolk when the egg is hardboiled. The eggs are marketed widely in Japan through Nippon Formula Feed Manufacturing Company and are gaining in popularity [4].
Cosmetics Antioxidative potency and UV protecting functions of tea catechins (polyphenons) are utilized in cosmetics. Cosmetic formulas and their manufacturing processes are highly specialised techniques known only to the cosmetic manufacturers. Various products are presently on the market and there are plans for still more to be marketed [4].
Catechin Soap Highly purified catechins are blended and made into rather crude looking square-shaped soap (Figure 9.3). Though priced high, users enjoy remedial effects on skin disorders by using this soap [4].
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Figure 9.3 Catechin soap
Kitchen deodorizer Tea catechins are dissolved in ethanol / water and added to a hand spray. After cooking fish, a spray of this liquid removes the fishy smell. Antibacterial actions are also anticipated by using this spray on kitchen utensils [4].
Mouth deodorizing tablets These catechin tablets can reduce odours such as that of garlic or fish, if taken after meals. They are packaged in a convenient portable size [4].
Catechin-enriched green tea bags Powdered green tea and herbs supplemented with Polyphenon 60 are kneaded, extruded and dried. The dried particles are put into tea bags and are being marketed in U.S. health care stores. Ginko biloba, ginseng, gymnema, bilberry and several others make up the range of flavours. These teas have been produced with the intention of making green teas palatable to the U.S. market [4].
Catechin matcha Matcha is a mixed Polyphenon and powdered milk, thereby doubling the normal catechin content per cup and making it less-pungent in taste [4].
Catechin enriched natural soft drink This is a thirst-quenching drink made from a mix of tea catechins and other natural ingredients [4].
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Slug and snail spray This is a safe, natural spray containing tea catechin, which exterminates slugs and snails [4].
Pet foods Tea catechins were mixed in pet foods to promote good health and to reduce faecal odour and caries in animals [4].
Pure tea polyphenol compounds Pure catechin compounds, a crude mixture of them, and crude theaflavins, are distributed by Funakoshi Company in Japan and Sigma Chemical Company worldwide [4].
9.4 Tea dyes Replacement of amaranth and other synthetic dyes with natural dyes of plant origin is an important goal of the modern food industry. This was emphasized during the Second International Congress of Food Science and Technology held in Warsaw, Poland in 1966. Amaranth is found to be a carcinogenic agent. Vitamin P-rich dyes of yellow, green, brown, orange, pink, red and black colours were developed from raw tea [127]. It is noteworthy that tea dyes containing valuable constituents (viz., catechins (vitamin P), caffeine, vitamins, amino acids, organic acids, etc) enrich food products. Tea dyes are produced from low-grade tea leaf and fanning, i.e., wastes of the tea-growing industry. In the tea dye manufacturing process (Figure 9.4), the raw material is exposed to thermal treatment to assure the complete enzyme inactivation. Then the raw tea is dried and extracted with water or ethanol; the extract is separated and spray or freeze dried to convert the starting material into a powder [128]. The yellow dye is obtained by treating the raw tea leaves extract with hot water. The brown dye is obtained by thermal treatment of the raw tea extract and yellow dye, as well as by pre -fermentation of the fresh tea leaf. The dye can be produced in two forms, with or without caffeine. The green caffeine containing dye is produced from the dried raw tea by means of extraction with 96% ethanol and its subsequent sublimation. The green caffeine-free dye is manufactured from tea leaves in accordance with technology production of vitamin P [129]. Tea dyes are prepared without the addition of other substances. These contain vitamin P as the tannin-catechin
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complex, caffeine, proteins, amino acids, organic acids, and other valuable tea constituents. Orange and pink dyes can be produced from green, yellow, or brown dyes by their treatment with ethyl acetate. The black dye can be manufactured from the yellow, brown, and green dyes supplied with ferric lactate. Due to this, the black dye increases the haemoglobin content in blood. By mixing several dyes with a wide spectrum of colours, nuances can be obtained. Low grade leaf and fannings
Extraction (C2H5OH) Green dye
Ferric lactate
Black dye
Extraction (H2O) Drying
Yellow/brown
Ethyl acetate extraction
Orange or pink dye Figure 9.4 Manufacturing of tea dyes
The red dye is produced from yellow tea dye. The method of production of red dye is simple and inexpensive. With respect to their organoleptic characteristics and physiochemical parameters, the foods coloured with red dyes meet the current requirements, maintain high quality in storage, and show good nutritional and biological value due to high content of vitamin P. Many patents are on the tea colour concentrate products. Tse [130] describes the preparation of tea colour concentrate wherein tea is employed as a catalyst in reactions generating colour formation. The resultant tea concentrate with enhanced colour, as well as tea products and beverages prepared from this are stable. The process comprises heating as a solution of sugar and acid to effect caramelisation reactions, followed by adding tea solids and heating to a higher temperature to catalyse Maillard reactions.
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9.4.1 Tea pigments as health molecules Tea polyphenols which are colourless, traditionally, have been known to be mainly composed of four catechins including (-) epicatechin (EC), epigallocatechin3-gallate (EGCG), epicatechin-3-gallate (ECG), and epigallocatechin (EGC). Recently, another group of polyphenolic compounds which are found in black tea (formed at the fermentation stage of black tea manufacture) are being studied [131]. These are catechin dimer, trimer or multipolymer [132]. Since, they can give a yellow or dark brown colour; they have the general name, ‘tea pigments’ in order to distinguish them from the traditional tea polyphenols. The pigments exhibited a significant role in treating hypertension, decreasing blood sugar, preventing cancer and atherosclerosis [133] and can increase super oxide dismutase (SOD) activity and decrease lipid per oxidation levels in patients with coronary heart disease, and reduce oxidative damage by free radicals in mice and guinea pigs [134]. The free radical scavenging abilities of tea pigments towards super oxide radical anion (O2-) and hydroxyl radical (OH.) and its comparison was made with tea polyphenols using a Chemiluminescence’s technique. O2- and OH were generated from pyrogallol autoxidation and fenton-type reaction respectively. Tea pigments could scavenge O2- and OH at EC50 values of 0.08 and 0.003 mg/ ml respectively, and the kinetics of the scavenging reactions varied with the concentration suggesting the operation of different mechanisms. In addition, the free radical scavenging abilities and kinetics of tea pigments were similar to those of tea polyphenols. The results indicated that tea pigments scavenged O2- as well OH in a dose-dependent fashion [135].
9.4.2 Use of tea dyes Tea dyes may be widely used in the confectionery industry and in many other food industries. Tea dyes can also be employed to colour soups, broths, sweets, desserts, ice creams, and synthetic and artificial foods. Tea dyes are also used in the butter and cheese industry, and in the manufacture of various skin creams, tooth pastes, tooth elixirs, etc. Tea dyes rich in vitamin P may be well used in the manufacture of lipsticks and hair dyes because those currently produced have a comparatively high toxicity when interacting with cellulose and proteins. Tea dyes yield stable coloration, therefore, they can be utilised in the textile and leather industries.
9.5 Triacontanol Triacontanol, the long chain fatty alcohol having the molecular formula C30H62O recognized as the substance responsible for the growth promoting
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ability of chopped Alfa-alfalfa [136]. The Alfa-Alfa chips and their extract (in quantities as small as 10–50mg dissolved in 280–380 litre of water applied over 1 hectare) can enhance the yields of some crops such as tomato, cucumber, lettuce, maize, corn and rice. The alcohol –A, which had earlier been isolated from green tea [137], was found to be the same as Triacontanol [138]. The Triacontanol content of green tea, black tea and tea waste from instant tea manufacturing process was reported. Instant tea wastes obtained from green leaves contain a maximum amount followed by black tea and green tea. This explains the effect of high temperatures involved in the firing stage of black and green tea manufacturing process [139]. Scientists at the CFTRI, Mysore, India developed the technology for the extraction of Triacontanol from tea wastes at a cost substantially lower than the international price. Successful field trials conducted in South India by UPASI Tea Research Institute showed that the harvestable yield increased by 25–30% with reduction in the dormant shoots of the tea plant [140]. This compound had been successfully field tested on other crops as well; it will not only help to increase the agricultural productivity but will also improve the economics of the caffeine extraction and instant tea processing factories.
9.6 Tea seed oil All species of genus camellia produce large oleaginous seeds. With increasing emphasis on clonal propagation of tea, the seeds will be used less for planting the crops. The cotyledons are present in a buff-coloured testa. The seed consist of 70% cotyledon and 30% testa. Seed production in India Malawi goes through biennial cycles [141], and seeds may fall over an extended period or in sharp peaks in shorter periods. The yield potential and productivity vary depending on various geographic, agro-climatic and varietal factors. Tea seeds can be decorticated and subjected to solvent extraction. Cloughley [141] reported the production of edible oil from tea seed oil. It was found in preliminary tasting trials that foods fried in tea seed oil were indistinguishable from those fried in groundnut oil. In tea producing countries, such as India where tea production is abundant and where there is an acute shortage of edible oils, tea seed oil could be considered a potential alternative. The oil content of seeds show wide differences ranging from 20% in Camellia sinensis to 45% in C. sasanqua (which is grown mainly for seed production). The oil yield could be improved by breeding and cultural practices. Tea seed oil closely resembles groundnut oil and olive oils in chemical composition [141]. It is rich in unsaturated fatty acids especially linoleic acid. It can be readily hydrogenated in the presence of nickel catalyst to give a hydrogenated fat. Because of its close similarity to olive oil, tea seed oil has been used for
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adulteration of olive oil; its presence is detectable by Fitelson’s test and tests by Chakrabarty and Chakrabarty [142]. The properties of tea seed oil give it a potential to use in cosmetic and pharmaceutical industries as a substitute for olive oil. Crude edible tea seed oil is refined so as to minimize the destruction of antioxidants and antioxidant precursors naturally occurring in the crude oil. This specially processed oil may be mixed, in small proportion, with much less expensive edible ‘bulk’ oil which has been conventionally refined. The mixture exhibits to a substantial extent, resistance of the dedicated oil to oxidation and polymerization [143].
9.7 Saponins Saponins are another valuable by-product that can be obtained from tea seeds. They constitute about 10–14% of tea seeds and are glycosides with good emulsifying properties. These are based on theasapogenols A, B, C, D and E as the aglycones, which are polyhydroxyoleanane type triterpenses. The sugar composition of the saponins isolated from the Japanese variety consists of D-glucoronic acid, D-xylose, D-glucose and D-galactose. According to Wickermasinghe [119] the residue after extracting the oil and saponins form about 25–40% of original seed material and contains about 2% N, 0.5% P and 2% K. Its high content of protein (12.6%) indicates that it would be useful as a cattle feed. These saponin compounds are available under the commercial name teaponin. Because of their excellent surface active properties, saponin compounds can be used as stabilizers in the photographic film emulsions and for increasing the solubility of CO2 in carbonated beverages. These are also used to control predaceous fish in ponds [144] and have been used for controlling earthworms in golf courses. Tea seed saponins possess a broad range of biological properties. These exhibit pronounced anti-exudative and anti-inflammatory properties. The treatment of pruned tea bushes with pure tea seed saponins led to an increased yield of flush on recovery, and treated nursery plants showed increased root weight and shoot growth [145].
9.8 Tea waste as extenders in polymers Phenol formaldehyde resins are used for a variety of applications. Research efforts have been focused on substituting phenol with cheaper waste phenolic materials of agricultural origin. Tea waste because of its low cost, easy availability and good concentration of phenolic materials seems to meet the need well. A partial replacement of phenol with tea polyphenols seems to
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increase the flow ability of the resultant resin without adversely impairing its polymer characteristics, thereby imparting a cost reduction [146]. Adhesives for wood with high water content have been prepared viz., formaldehyde-phenolresorcinol co-polymer using tea powder as filler [147]. Phenol-formaldehyde, melamine-formaldehyde resins and PVC resin with tea biomass as filler gives plastics with high flow values [148]. If suitably exploited, tannin polymers from tea wastes can replace existing resins in the plywood adhesive filed.
9.9 Summary and conclusion “If you are cold, tea will warm you. If you are too heated, it will cool you. If you are too depressed, it will cheer you. If you are excited, it will calm you”. – William Ewart Gladstone, former British Prime minister ‘Tea’ – the word is enough to explain a tremendous beverage with all its high impact properties and popularity among all the people across the world. It is the second-most widely consumed drink in worldwide, after water. Starting from its glamorous history till the date, it is flourishing in all its forms and compositions. In the book many new value-added products have been focused with a prospective to bring those things aware to common men. India and China are the largest and second largest producer as well as consumers of tea, respectively. In global production India’s contribution is 25% while that of China is 31%. The contribution of India and China in global tea business is 11% and 18%, respectively. Other countries like Kenya, Sri Lanka and Indonesia contribute 25% of world tea but control 50% of world trade. As per Food and Agriculture Organization (FAO) report on tea industry, the market for tea industry is expected to grow at 3% per annum. With removal of Quantitative Restrictions (QRs) and World Trade Organization (WTO) regulations coming into force, the consumption is going to increase in developing countries. India also leads in global research and development in tea industry. India is the largest manufacturer and exporter of tea machinery. There are six types of processed teas: green, green brick, yellow, white, oolong and black tea. This categorization is based on the degree of fermentation and oxidation of simple polyphenols present in tea leaves. Green and yellow teas are unfermented. Polyphenols are oxidized hardly in green tea, but these are non-enzymatically oxidized in yellow tea. White, oolong (red) and black teas are fermented, with white having least fermentation and black the most. All these possess distinct flavours and qualities that are determined by degree of oxidation of polyphenols, whether enzymatic or non-enzymatic. All processing plants need to be mechanised and sophisticated, so as to cope up
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with the globalisation scenario. In India, awareness about green tea and its high therapeutic applications need to be increased among the consumers. This can be implemented by mass media. People also should gain the idea of teamaking process rather than making it in traditional style. The perspective changes with advances in chemical research and main constituent of tea leaves were broadly identified to be carbohydrates, proteins, polyphenols, caffeine, theanine, vitamins and minerals. But these chemicals in tea leaves undergo dynamic changes as green tea leaves are converted into black tea during the process of manufacturing. Green tea has preventive effects on both chronic inflammatory diseases and lifestyle-related diseases (including cardiovascular disease and cancer), resulting in prolongation of life span. Black tea also possesses many biological effects on the organisms. It acts as an effective antioxidant because of its free radical-scavenging and metalchelating ability. Due to this, it is active against inflammation, clastogenesis, and several types of cancer. Tea reduces DNA damage and mutagenesis due to oxidative stress or the presence of pro-mutagens through antioxidant function, blocking activation pathways of mutagens, suppressing transcription of enzymes involved etc. Inhibition of low-density lipoprotein (LDL) peroxidation, suppression of fatty acid synthase, etc., suggest that tea may have a role in preventing cardiovascular diseases. Some epidemiological studies support the protective role of black tea against cardiovascular diseases but some do not. Besides, black tea has beneficial effects on the gastrointestinal tract; it affects motility, absorption, microflora, etc., by influencing the hormonal balance and antioxidant function black tea improves bone mineral density. It is also antiviral due to its enzyme-inhibiting and receptor-blocking properties. Although its role in cancers of the gastrointestinal tract, liver, and prostate is confirmed, its effect against urinary tract cancer is uncertain and further studies are required. Apart from these, excess consumption may lead to the formation of a stained pellicle layer on teeth, which is difficult to eliminate, inhibits trypsin, influences mineral absorption, causes convulsions, etc. Excess caffeine intake may have adverse effects on selected organs as reported in studies on some organisms. These reports indicate that there is a wide scope of further research for the efficient use of black tea active conserves/isolates to reap health benefits. Recently, ample amount of research has been carried out on high impact value-added products, and wide varieties of products are also launched into market. Tea is a widely consumed beverage; and for a number of Third World countries like India, Sri Lanka, Kenya, Indonesia and others, tea is a major plantation crop that earns foreign exchange by way of exports. A disturbing trend in the export market has become more and more evident in recent times
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is that the tea price fluctuates in erratic cycles. The Indian export trade is also afflicted by the increasing competition from other tea-producing countries and escalating cost of inputs, which tend to make the tea plantation uneconomical. This trend can be offset by increasing the productivity of tea plantation or by diversification into value-added products. In this article a variety of valueadded products are described. These include tea bags, packet tea, instant tea, flavoured tea, decaffeinated tea, fortified tea, tonic tea, tea cider, tea Kombucha, iced tea, herbal tea and tea concentrate. Point of attention is that how the consumers accept these products. Here, one has to carry out the market research and product has to be popularised based on its school of benefits and organoleptic properties. Then the lab to industry programme will be successful. By-product utilization has to be carried out to obtain a better economic profit and also to become environmental friendly. These will able to reduce the overall processing cost as well as price of product. It has been estimated that 2–4% of the black tea produced is wasted every year, which cannot be further processed for consumption. To make tea-producing operations economically viable, attempts should be made to utilize the tea waste. The literature shows that research and development efforts are centred on the following by-products fors utilization of tea waste: (a) caffeine, (b) polyphenols, (c) pigments, (d) triacontanol, (e) tea seed oil and saponins, and (f) extender in plastics.
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10 Introduction to soft drinks
10.1 Soft drink Fruit drink or juice, squash, crush or cordial, soda water, artificially sweetened carbonated water (flavoured or unflavoured, herbal or botanical) beverage is called soft drink [1]. A soft drink is the term commonly applied to carbonated and non-carbonated drinks, and is also known as still drinks, made from concentrates [2], as opposed to hot tea, coffee, milk and milkshakes. Commonly, a soft drink refers to almost any cold drink that does not contain alcohol. Beverages like soda, lemonade and fruit punch are among the most common type of soft drinks. Soft drinks usually contain carbonated water, high fructose corn syrup or sucrose, caramel colour, phosphoric acid and flavours. Soft drinks are basically found in two forms such as ready-to-drink and concentrated form. The concentrated form of beverage is diluted further to obtain dilutable soft drinks known as ready-to-drink [3].
10.2 Need of soft drinks Beverages have become part of our culture and serve as social enjoyment. Soft drinks are consumed mainly for refreshment. Refreshment is very important to people of all ages at work and play. Sugar sweetened soft drink contains energy giving carbohydrate, which is a refreshing addition to a balanced diet. These can also be psychologically refreshing during stress. There are a wide variety of soft drinks – clear, cola, fruit and others (as cream sodas). Soft drinks can be made on our own by combining sparkling water with grape, apple, orange, lemon or limejuice. Soft drinks are found conveniently at every grocery stores and health food stores, where these are available round the year.
10.3 Benefits of soft drinks Soft drinks contribute to the healthy and enjoyable diet. Soft drinks in addition to water also meet the fluid requirement. Besides water, body needs other
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nutrients for growth, energy and good health. Selected beverages can provide this vital combination of protein, carbohydrate, fat, vitamins, minerals and water. Hence, soft drinks provide part of the total daily intake of liquid and energy. The second area of nutritional significance is the ability of soft drinks to promote rapid uptake of salts and water by body. Soft drinks are the part of balanced diet and healthy lifestyle as these contain health elements like vitamins and calcium. The consumers choose the soft drinks that best suit their lifestyle, tastes, nutritional needs and physiological constraints. Soft drinks provide a refreshing and positive contribution to everyday living. There are three main areas of soft drink’s nutritional significance. The first area is energy; carbohydrates are the important sources of energy. The second area of nutritional significance is rapid uptake of body salts and water by isotonic drinks. The third area is low-calorie forms which are meant for those people who wish to enjoy such beverages with minimum calorie intake. Other nutritional benefits are availability of essential vitamins and minerals [3]. Along with the benefits, the negative side is the development of dental caries. This has been claimed by means of sugar residues in the mouth when an acidic drink is consumed constantly [4].
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11 Beverage consumption
11.1 Introduction Country-wise beverages’ consumption is given in Table 11.1 and share of each type of beverage is presented in Table 11.2. Table 11.1 Country-wise beverages consumption [5]
Name of the country
Consumption (%)
Japan
4
Brazil
5
India
9
China
10
United States
15
Others
57
Despite undergoing significant changes, the soft drink industry responded strongly and grew by five percent. Total soft drinks value is now £7.8 billion, up by 5%. 2005 saw a continued trend towards health and well-being. Takehome soft drinks growth, outperformed all other grocery categories in the top ten. Now a day’s smoothies, dairy drinks, water and pure juice are the top performers. Annual per capita consumption of soft drinks is 242 litres up, from 239 litres, an increase of 1% in 2005 [6]. In the same year, the global soft drink market is estimated to be at a value of US$340 billion. In the soft drink sector, the main idea is to get steady growth. The recognition, familiarity and shelf life are very important. Consumers also want fresh products in naturally good form, which should be clear on the packaging. More the proportion of fruits and vegetables in a drink, better is its quality. Table 11.2 Market share of different soft beverages [5]
Soft Drinks
% Share
Dilutable
7
Juice/Nectars
8
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11
Carbonates
41
Bottled water
33
11.2 World market North America provides the largest soft drinks market with 27% of total soft drink sales, with the consumption of 192 litres/person/year. The European market accounts for 21%, with consumption of 50.8 litres/person/year. Asia and South America shows fastest growth in soft drinks sector. Carbonated soft drinks occupy 45% of the global volume of all soft drinks [7]. Currently, the fastest developing markets are expected to come from Asia. Pakistan is predicted to have the highest percentage while India is expected to make sizable volume gains. The other countries expected to be are Indonesia, China and Vietnam. Food and beverage companies increased their advertising expenditure in 2005. Brands like Coca-cola Enterprises, PepsiCo and Britvic are on the top of the list. GlaxoSmithKline; Pepsi Max and Danacol Actimel have also increased this advertising expenditure. The soft drinks like colas, dairy drinks, fruit juice and smoothies contribute as much as £27 million, £37 million, £17 million and £5 million respectively towards advertising trends [6].
11.3 Major players of soft drinks in the world Global market for energy drinks with respect to Asian sector, especially Thailand, Japan, China and South Korea outlined with sales in Western Europe and USA (The formulation, presentation and the future outlook). The leading companies as consumer of energy drinks were from Thailand, USA and Japan [8]. Now the two multinational Companies (viz., Coca Cola and PepsiCo) are largely controlling the global soft drink industry. Coca Cola leads in the world with 60% of the global cola market under the flagship of Coca-Cola brand. Cadbury Schweppes includes among other notable players [9].
11.4 Indian scenario The market growth rate is presently 7–8% per annum, which was around 2–3% in the 1980s and increased to 5–6% in the 1990s. The soft drinks sales mostly occur in summer and only 5–6% of total sales occur in winters. The 50% of the total yearly sales is contributed by summers as the season lasts for 70–75 days. In terms of regional market distribution, cola drinks have their main markets in metro cities and northern states like Uttar Pradesh, Punjab,
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Haryana, etc. In southern states orange flavoured drinks and sodas are popular, whereas mango-flavoured drinks are preferred in western markets. Soft drinks in India can be divided into carbonated and non-carbonated drinks and these are available in glass bottles, aluminium cans, pet bottles or disposable containers. Carbonated drinks include cola, lemon and oranges, and noncarbonated drinks include mango drinks. Another classification in India is cola products and non-cola products. Cola products include brands like Pepsi Cola, Diet Pepsi, Coca-Cola, Diet Coke, Thumps Up etc. In India, cola drinks account for nearly 61–62% of the total soft drinks market. The 36% of the total soft drink market is accounted by non-cola products [7].
11.4.1 Major players of soft drinks in India The major players in India are PepsiCo and Coca-cola. Coca-cola has re-entered India after 16 years in 1993, which had winded up its Indian operation during the introduction of the Foreign Exchange Regulation Act (FERA) regime. A couples of years before PepsiCo came into the market. Pepsi had brought over, Mumbai–based Duke’s range of soft drinks in 1991. The figures are always conflicting to consider, which is to be higher in production; however, these are the two dominating companies world over. The increased responsibilities for soft drink industry are due to the provision of nutritional information, product composition, response promotion, choice and range. Soft drink is one of the most important product category in the delivered wholesale cash and carry market. It contributes more than £1billion of sales per year through independent retail, catering and on-premise outlets [6]. The soft drinks industry has a great potential for growth in grocery categories as the relationship between shopping trials and consumption occasions is critical. Day-by-day increase in demand by children and youth, and repeat purchase is encouraged at home after consumption.
11.5 Market trends of functional drinks The trends in soft drink market showed that nutraceuticals were the fastest growing segment followed by sport drinks. The fortified drinks contributed a market share of 76%, followed by sports drinks, energy drinks and nutraceuticals 13, 8, 3% of market volume, respectively [10]. The day by day growth of soft drinks market is for beverages with additional health benefits, due to increased scientific knowledge about the benefits of functional ingredients among consumers. Rapid growth of the market for energy drinks and amino-acid containing soft drinks are expected.
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11.6 Expansion of soft drinks market The soft drink market is expanding day by day due to continued focus on health and well-being. Pure juice, fruit drinks, bottled water, smoothies and dairy drinks continue to drive growth. Significant opportunities for soft drinks manufactures are provided by increased demand for functionality, such as blood-pressure-reducing and cholesterol-lowering drinks. Soft drink manufactures emphasised more on low calorie variants such as 7UP Free, Tango Clear and Fanta Z. The soft drinks market has found to be expanded to all categories [7]. Quick service restaurants are significantly larger than full service restaurants both in terms of outlets and value of soft drinks. Fast food volume for soft drinks has shown 21 percent growth since 2000 [6]. Workplace catering and growth of eating-out by adults and families contributed to the growth and sale of soft drinks. Rapid growth in leisure and sports leads to sale of soft drinks. Cinema contribution is also increasing day by day in soft drinks sales. Still drinks account for 50 percent of all sales through schools, which is 12 percent more than the previous years.
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12 Soft drink classification
12.1 Introduction Soft drinks can be classified into two categories: ready-to-drink and concentrated soft drinks.
12.2 Ready-to-drink This category of soft drinks is divided into carbonated and non-carbonated soft drinks. Non-carbonated drinks have shown considerable growth because of aseptic packaging, whereas carbonated beverages provide an effective antimicrobial effect because of the presence of CO2. Ready-to-drink soft drinks are also classified into following categories.
12.2.1 Fizzy drinks This is made by injecting carbon dioxide into the drink at a pressure of several atmospheres. At high pressure large volumes of gas can be dissolved. As the pressure is released, carbon dioxide comes out of the solution forming numerous bubbles as being released back into the atmosphere. After the release of carbon dioxide, the drink is said to be flat. Carbonated drinks taste fizzy due to carbonic acid including a slight burning sensation and bubbles; both the phenomena are caused by carbonic acid concentration [11].
12.2.2 Natural juice These drinks are prepared from processed fruits. These are formulated with plant-based formulations and nutrient content of fruit and vegetable juices. [12]. It includes all concentrated juices except frozen juice. Such drinks require dilution and sometimes powders for reconstitution in bottles, cans, and ready to drink or in jars. Some examples are lemon, orange and grapefruit juices.
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12.2.3 Colas Colas (Figure 12.1) are flavoured carbonated drinks, containing cherry flavour and twist of lemon. They are made essentially from an extract of cola nut and may contain caffeine.
Figure 12.1 Cola beverage
12.2.4 Fruit flavoured These are with a sweet taste. The fruit flavours like strawberry and grape are abounding in sugar. Citrus-flavoured juices seem to be a mixture of sweet and tart; the people who like tangy drinks prefer these drinks.
12.2.5 Fruit-flavoured carbonates These are carbonated drinks with typical fruit flavours. The fruit flavours used in this type of drinks are orange, cherry, lime, blackcurrant, apple, pineapple, lemon, grapefruit, tropical and other fruit flavours. Lemonade also belongs to this class.
12.2.6 Energy drinks There are three basic types of energy drinks – refreshment, sports and functional.
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(i) R efreshment – These are formulated for someone whose energy levels rundown or is recovering from illness. (ii) Sports – These are formulated to replace fluids rapidly during exercise and also to maintain the body’s blood glucose level. The top three global markets for sports drinks are North America 50%, Asia/ Australia 41%, and Europe 8% [13]. (iii) Functional – These are formulated for anyone who wants to gain alertness. The two important varieties are as follows: (1) energy supplements containing slow, medium and fast-acting sugars to supply energy, and (2) energy enhancers containing caffeine or taurine to boost alertness.
Company-wise contribution – energy drinks Coca-Cola Company has launched a new sport drink named Powerade (lowcalorie). The drink is a source of electrolytes and B complex vitamins at comparable levels. The Powerade is available in lemon, black cherry and strawberry flavours. Another energy drink launched by Coca-Cola is Von Dutch. Bravo has also come up as a new line of breakfast beverages, blended with fruits and flavours. Moreover these are fortified with naturally found antioxidants. Pepsi has launched a specialized sports drink, named Gatorade Endurance Formula, a blend of electrolytes such as Ca, Mg, Na and K with 65 carbohydrates. This comes in two flavours – orange and fruit punch. Cadbury Schweppes has re-launched 7Up as 7Up line, expanded with new flavours like cherry flavour, fruit juices and with added calcium.
Other energy drinks Energy 69, LLC, New York, has launched a new beverage called Energy 69, (sugar free version) with ingredients such as taurine, guarana seeds, green tea leaf, caffeine, d-ribose, schizandra, L-carntine and damiana leaves. Glaceau, Whitestone, NY, has launched a vitamin water line-up, flavoured with lemon along with Ca, Mg, Na and K. Their function is to speed up hydration process. The drink is also rich in vitamin B and C. Natural Percepts, LLC, Los Angeles have launched the ‘Yes’ drink. The composition of the drink is 12 vitamins, 8 antioxidants, 10 fortified minerals, 70 trace minerals, 22 amino acids and other essential nutrients. Universal Food & Beverage Company has replaced its healthy drinks with its feed water selection. Frost 20 is a drink with no calories, sugar-free, vitamin enhanced and naturally flavoured. The flavours include lemon lime, mixed berry, peach and tropical fruits. Abbott Laboratories, Ohio, has launched a line of beverages including Healthy Mon snack bars and nutrition shakes specially designed for pregnant women. The
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lactose-free shakes contain 2 g proteins, 3 g fat with creamy milk chocolate and homemade vanilla varieties [14].
12.2.7 Mixed soft drinks Soft drink made by mixing many soft drinks together is variously known as graveyard, pop bomb, swamp water and garbage soda. An example for mixed fruit juice is blending of ber, pomegranate and guava juice to get desired colour and flavour, which can not be obtained in their individual formulations [15].
12.2.8 Dry powder mix These are designed to appeal to a number of consumers and for variable uses. These formulations are similar to liquid soft drinks except for water content. The compositions that differ in dry powder mix are flavours, clouding emulsions and fruit materials, which are spray dried and/or freeze dried. The long-term stability of dry powder mix is better than that of liquid drinks. These are found to be ideal for vitamin fortification because of their slow decay rate in the absence of water and air [16].
12.3 Concentrated soft drinks Most of the concentrated beverages contain fruit juice or whole fruit. The term whole fruit refers to comminute form of citrus that includes juice, albedo (pith), flavedo (peel) and essential oil. The preservation methods of concentrated soft drinks are flash pasteurization and chemical preservation. Some of the examples of concentrated soft drinks are as follows:
12.3.1 Squash A fruit juice intended for consumption after dilution. It possesses natural juice strength. The popular drinks are lemon barley and orange barley. These contain a liquor called as barley water, prepared from steeped barley and is incorporated into orange or lemon fruit juice [2].
12.3.2 Cordial These drinks comfort the heart. It is a kind of beverage containing sugar and requires dilution before drinking. The examples are as follows:
(a) L ime juice cordial – A squash, which must contain 25% fruit juice by volume. (b) Black currant cordial – A squash, which must contain 10% blackcurrant juice by volume [1].
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12.4 Other categories 12.4.1 Diet soft drinks These drinks are with low sugar content (reduction in calories) and sweetened with alternate sweeteners such as aspartame, saccharin, sucralose, potassium or a combination of these. They include soya protein, based with soluble fibre, antioxidants, phyto nutrients and herbal supplements to promote weight loss [11].
12.4.2 Sports drinks Sports drinks are suitable for consumption before, during and after sporting and other physical activities. They provide water, energy and electrolytes in a palatable and digestible form. The ingredients are dextrose, sucrose, citric acid, mono potassium phosphate, sodium chloride, sodium citrate, orange flavour, potassium chloride, sodium saccharin, ascorbic acid and colourings.
12.4.3 Functional drinks These are specially designed to boost or replace lost energy levels resulting from ill health. These are intended to replace lost minerals, sugars, trace elements and fluids due to exercise. These are sparkling, still and dilutable drinks and are specially designed to boost energy levels. Physiologically functional beverages can prevent allergic rhinitis and treatment of hyperlipaemia and diseases such as arteriosclerosis, obesity and liver disease. The methylated catechins are the active ingredients in beverages [17]. The important functional drinks are as follows:
Herbal drinks These are also called as health drinks due to their health benefits. These drinks rely on carefully chosen ingredients, which are associated with beneficial effects. For example, relax drink contains Schizandra, Ginseng and Hibiscus, where Ginseng and Schizandra are taken to combat stress and the known source of vitamin is Hibiscus. Other than the extracts, drinks also contain vitamins and minerals such as B3, B6, Niacin, Sodium, Ca, Mg and P [18]. The increase in the use of soft drink containing herbal extracts is due to their health promoting properties, development of new mixtures of herbal drinks with a wide range of beneficial effects, increase in consumer acceptance of distinctive flavours of herbal drinks and the growing volume of drinks produced, containing herbal extracts, e.g. elderflower and ginseng.
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Nutraceuticals It is defined as any food or part of food that provides medical or health benefits, including prevention and treatment of diseases [19]. The market for nutraceutical beverages has been growing rapidly over last several years to the point where no beverage has been left unfortified. Consumer demands are increasing, as they want their beverages to do more than just taste good and refresh. Moreover, consumers are making connections between diet and health [20]. Hence, these are also known as “better-for-you” beverages or “health and wellness” drinks. The concept of nutraceutical originated in Japan where the market for functional foods has been estimated to be 2.4 billion pounds [21]. One of Europe’s largest sports nutrition companies has launched a drink called “PeptoPro”. PeptoPro contains tiny peptides (consists of two to three amino acids – a casein hydrolysate ingredient), having better body uptake. This drink does not stay in the stomach, as acted upon by the above enzyme, which breaks the proteins into many small pieces. These di- or tripeptides comprises two or three amino acids. These are water soluble, no longer bitter and can be immediately taken up by the body, therefore can be consumed before, during and after exercise [14].
12.4.4 Smoothies Smoothies are fruit-based products. These are the excellent examples of addition of soluble fibres, vitamins and antioxidants into the diet. The source of fibres is inulin, which consists of oligosaccharides extracted from Chicory and Jerusalem artichokes (Helianthus tuberosus). The health benefits are claimed to improve colon function, enhance the working of the gut and act as a prebiotic [22].
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13 Ingredients of soft drinks
13.1 Introduction The main ingredients in the soft drinks are water, sweeteners, acidulants, colorants, flavours and clouding agents.
13.2 Water Water is the major component of soft drink. A carbonated soft drink usually contains 82–97% water. The quality of the water used in a beverage has a critical impact on the taste, appearance, physical and microbiological stability. The water used may come from the two main sources – water supply from local government agencies and privately owned wells. Although, the local government agencies or private well owners treat the water, but it may still have components that may affect the quality of the beverages in which it is used. These need to be eliminated or reduced to minimize their effects. Moreover, the water from different sources may differ considerably; so to maintain the uniform quality of the product the water has to be standardized in its quality [23].
13.2.1 Adverse factors from water Possible adverse factors from water that could affect the quality of soft drinks are suspended matter, micro-organisms and source quality variation.
Suspended matter The suspended colloidal matter and organic particles not only cause unpleasant appearance and turbidity but can also encourage the micro-organisms to grow. These serve as hiding places for micro-organisms.
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Micro-organisms One of the prime aims of treatment of source water is to eliminate pathogenic organisms. But soft drinks manufactures cannot take any risk in this matter to use the water as such. So water must be disinfected to check the health risks.
Source quality variation Sources of water (the surface and underground types) are often subjected to seasonal changes as well as unpredictable local events in the environment that affect the quality of raw water. Chemical composition of minor ingredients of the water is important. The alkalinity and pH of the raw water is determined by the amount of minerals dissolved. High pH neutralizes the acidity component of the beverage that affect the overall taste profile of the beverage. The minerals like iron, chloride, and sulphates at even very low concentration can impart off-taste to the beverage. The dissolved organic compounds such as trihalogens or residual pesticides may also be present, which are also hazardous to health. As the raw water from different sources differs considerably, there is a need for standard water specification to achieve consistent quality of soft drinks [23].
13.2.2 Water treatment The soft drink manufactures have to select an appropriate treatment to maintain quality of the product. The different treatments include lime decarbonization, ion exchange, reverse osmosis and nanofiltration for water with heavy salt loading. The consideration is to be given to economic viability, limitation of different treatments and extension of existing equipment in order to incorporate new treatment technology. Basic water treatment is presented in the Figure 13.1.
13.3 Sweeteners The sensation of sweetness is transmitted to human brain through specific protein molecules called receptors. The function of sweeteners is to bind these receptors on the surface of the cells. These receptors then produce the signals corresponding to different ingredients present in the food perceived by human brain. Probably the sweetness is the most important feature of a soft drink. According to UK Soft Drinks Regulations, 1964 [24], a low-calorie soft drink should contain sugar to a minimum level of 45g/l, but these regulations have been revoked in the year 1995 [25].
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Ingredients of soft drinks Raw water Alkalinity control Enhanced filtration
Disinfection
Activated carbon purification
Polishing filtration
Purified water Figure 13.1 Purification of water
13.3.1 Classification Sweeteners are classified as natural and synthetic. The natural ones are the most nutritive dietary sweeteners like sucrose, fructose, lactose and maltose. Sucrose is considered to be the major sweetener responsible for improving the acceptability of food from centuries [26]. Relative sweetness of natural sweeteners is presented in Table 13.1. Table 13.1 Relative sweetness of natural sweeteners [27]
Sugar
Relative sweetness
Sucrose
1.0
Glucose
0.6
Fructose
2.0
Maltose
0.6
Lactose
0.25
Steviol glycosides
40–300
From Table 13.1 it can be observed that there is a difference in the degree of sweetness of various sweeteners, such as glucose and maltose are half as sweet as sucrose while fructose is twice as sweet as sucrose. The sweetness
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of lactose is only one-fourth of that of sucrose. Relative sweetness of artificial sweeteners is presented in Table 13.2. Table 13.2 Relative sweetness of artificial sweeteners [27]
Sweetener
Relative sweetness*
Saccharine
300–500
Acesulfame-K
150–300
Cyclamate
30
Sucralose
600
Aspartame
150–200
Neotame
7000–13000
Alitame
2000
Talin
2500
*With reference to sucrose
The synthetic sweeteners because of their intense sweetness are called high potency sweeteners (HPS) e.g. certain proteins, terepene glycosides like saccharin, cyclamates, aspartame and acesulfame-K. The need for HPS sweeteners arises due to health reasons for persons who cannot have sugar in their meal. Further, the economic reasons also add for the development of HPS. According to American Dietetic Association, the consumer can safely enjoy both nutritive and non-nutritive sweeteners within the context of a diet consistent with the dietary guidelines for Americans. The International Food Information Council has also expressed same opinion. Major limitations of genetic production of natural HPS in commercialization are limited production and high cost. The genetically modified HPS are thaumatin and brazzein, extracted and purified from the plants. The degree of sweetness of natural HPS is presented in Table 13.3. Table 13.3 The degree of sweetness of HPS [27]
Sweetener
Degree of sweetness*
Chemical nature
Thaumatin
1000
Protein
Brazzein
2000
Protein
Stevioside
300
Triterpene-Glycoside
Glycyrrhizinic acid
300
Triterpene-Glycoside
Mogroside
250
Triterpene-Glycoside
* With reference to sucrose
13.3.2 Sweeteners in the industry These are broadly of three types – carbohydrate sweeteners, intense sweeteners and mixed sweeteners.
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Carbohydrate sweeteners include • Mono and disaccharides – glucose, fructose, sucrose, raw sugar, brown sugar, invert sugar, lactose, maltose, corn syrups, caramel sugar, caramel. • Sugar alcohols – sorbitol, mannitol, xylitol, isomalt, maltitol, lactose and starch hydrolysates. Intense sweeteners comprise of • Natural sweeteners – stevioside, thaumatin, dihydrochalcone, miraculin • Major artificial sweeteners – saccharin, cyclamate, acesulfame-K, and aspartame • Other sweeteners – synthetic peptide sweeteners, sucralose, L-sugar Carbohydrate sweeteners The profile of the use of sweeteners in soft drinks has changed significantly over the last 10–15 years. Carbohydrate sweeteners are widely being used in juices and soft drinks and represent the largest share of the global sweetener market. Currently these account for the 81% of sweetener usage [28]. A number of carbohydrate sweeteners are used in soft drinks to provide different attributes, including sweetness, mouth feel, stability and colour. Some of the carbohydrate-based sweeteners, which are used in soft drinks, are described below.
Sucrose It is regarded as the ‘gold’ standard for a sweet taste. It is a disaccharide with molecular weight of 342.31. It is available in crystalline form and is manufactured from cane or beet. During manufacturing, juice extracted from the cane or beet is subjected to purification steps including precipitation, absorption, crystallization and evaporation, which remove non-sugars and progressively concentrate the sucrose solution.
Glucose syrups / high fructose corn syrups Glucose syrups, also known as corn syrups, are defined by the European Commission (EC) as “a refined, concentrated aqueous solution of D(+)glucose, maltose and other polymers of D-glucose obtained by the controlled partial hydrolysis of the starch” [29]. These are manufactured either by acid or enzymatic hydrolyses of starch. In acid hydrolysis, hydrochloric acid is used because sulphuric acid causes
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haze in syrups due to insoluble sulphates. Corn, potato, wheat or cassava, all can be used as the source of starch in the manufacturing process. The method of acid hydrolysis is non-specific, but if conditions are tightly controlled, it is possible to make products with a reasonably good carbohydrate profile. The degree of hydrolysis is defined by ‘DE’ value or ‘dextrose equivalent’. It is the total reducing sugar content of the syrup, compared to D(+)-glucose on a dry matter basis. Starch with no hydrolysis has a DE of 0, whereas glucose or dextrose, which is the product of starch hydrolysis, has a DE of 100. Glucose syrups with DE values in the range of 42–63 are used in soft drinks industry [3]. Enzymatic method involves the use of glucose isomerase, which converts glucose to fructose, and provides greater degree of control over the sugar profile of the resulting syrup. High fructose corn syrup with fructose levels of 42% provides the same sweetness as sucrose. This can be further refined to obtain 55% fructose syrup. In soft drinks, glucose syrups are used to provide sweetness and mouth-feel to the products and occasionally, specific physiological properties in sports and energy drinks.
Fructose Fructose is unique among known sugars in being sweeter than sucrose. Fructose has a clean, sweet taste and functions as a synergist with many bulk and intense sweeteners. It is very soluble and also relatively hygroscopic, compared to sucrose [30]. Chemically, it is very active and readily takes part in Maillard reactions, which may cause browning in some products. Fructose can be used as a sugar substitute in crystalline or syrup form. It is found naturally in many fruits and also in honey, but commercially it is manufactured using sucrose as a starting material. Initially, sucrose is hydrolysed to give a mixture of glucose and fructose; these are separated using chromatography and the fructose is then crystallized. It has some interesting physiological properties. It is a monosaccharide with energy content of 4 kcal/g. Due to its increased sweetness, it can be used at lower levels than sucrose. It is slowly absorbed and metabolized in the body, independent of insulin production and does not cause rapid rise in blood glucose after ingestion. It is therefore, suitable for diabetics and also for use in drinks intended to act as a slower, more sustainable energy source. It is a low glycemic index sugar when compared to glucose and has been seen to have an increased satiety value [31]. Mineral absorption (iron and calcium) has also shown to be positively affected by the incorporation of fructose into the diet [32].
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L-Sugars L-sugars are simple six-carbon low calorie sugar (hexoses, monosaccharides), which are true sugar-flavour sweeteners and bulking agents. These taste like sucrose, but human body does not seem to metabolise. The L-sugars such as L-glucose, L-fructose and L-galactose were patented as low calorie sweeteners [33]. L-sugars provide a clean sweet taste while furnishing the bulk, texture, browning and other properties so necessary for effective formulation of food products. L- and D-sugars differ in their structure but they have similar physical characteristics, such as melting point, solubility, viscosity, texture, hygroscopicity, density, colour and appearance. Chemical properties of both forms in symmetrical environments are likewise identical. For e.g., thermal and pH stabilities in various aqueous solutions were identical for the glucose and fructose enantiomers. Unlike all currently available low calorie sweeteners, the L-sugars brown upon baking. Therefore, L-sugars are expected to yield food products similar to those using D-sugars, but without the calories. The taste profile of L-sugars was found to be same as that of D-sugars and no cooling effect or aftertaste was reported. The sugars are tested for toxicity and other side effects before approval from US FDA.
Intense sweeteners Mostly, these are synthetic sweeteners (Figure 13.2). Properties and applications of important synthetic sweeteners in foods are presented in the following sections.
Saccharin (o-sulfobenzoic acidimide). Saccharin is the oldest among synthetic sweeteners. The commercial manufacture of saccharin begins in early 1900 when millions of diabetic patients all over the world were waiting for the substitute of sugar. Saccharin is free from problems like tooth decay and also safe to use for diabetic patients. It is a white crystalline product, which gives a metallic after-taste when used at higher concentration [34]. The products used as masking agent for saccharin’s bitter taste are fructose, gluconates, tartarates, ribonucleotides [35], sugars, sugar alcohols and other intense sweeteners. Saccharin is widely used through out the world; however, according to a clinical research, high dose of it may cause cancer [36].
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Figure 13.2 Intense sweeteners
Acesulfame- K Clauss and Jensen [37] accidentally discovered a compound, Potassium salt of 6-methyl-1,2,3-oxathiazine-4 (3H)-one-2, 2-dioxide. Initially, used in dry food mixes now is used in carbonated as well as in non-carbonated drinks as well.. The sweetness varies from 100 to 200 times of sucrose, depending upon concentration and application can withstand high cooking temperatures. Basically acesulfame-K is a white crystalline powder. The specific gravity of pure crystalline acesulfame-K is 1.83 g/cm3 [38]. The sweet taste of acesulfame-K is perceived quickly and does not persist longer. In aqueous solution with higher acesulfame-K, bitterness can be detected sometimes [39]. It is not found to be reactive with other soft drink ingredients; however, the addition of potassium ion in the presence of acesulfame-K should be taken into account.
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Cyclamate Cyclamate derived from sulphamic acid of cyclohexylamine (cyclamic acid). It is approximately 35 times sweeter than sucrose, compared to other sweeteners. Moreover, this is banned in some countries as it is suspected to be carcinogenic. Cyclamate has improved sweetness in the presence of other sweeteners like acesulfame-K, aspartame, saccharin and sucralose [40]. Most of the people reported to metabolise less than 10% cyclamate. However, 47% of population can metabolise 20–85% cyclamate into cyclohexylamine [41, 42].
Sucralose This is trichloro-galacto sucrose which is formed by chlorination of sucrose. It is safe to use as it does not contribute calorie and does not cause dental caries. It was approved to be used as tabletop sweetener during 1998 [27].
Aspartame The trade names are NutraSweet, Equal, Sugar-Free, Egal, or Canderal. L-aspartic acid and L-phenylalanine are the two natural amino acids present in aspartame. It is the most popular sweetening ingredient now days, which was discovered in 1965 [43]. Earlier, it was synthesized by chemical method but now by enzymatic method (formation of peptide bond between its constituent amino acids). Currently, Japan’s Ajinomoto Company is the largest manufacturer of aspartame. It is slightly soluble in water (about 1.0% at 25°C) and is sparingly soluble in alcohol [44]. The solubility increases at elevated temperatures and in acidic conditions. The taste of aspartame is similar to sucrose sweetness.
Neotame and Alitame These two are closely related to asparatame. Neotame (N-[N-3, 3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine-methyl ester) differs from aspartame in structure, having neohexyl group in addition to the methyl ester group. It has been reported as a flavour enhancer and it is found to be 8000 times sweeter than sucrose, therefore, used at a very low concentration in soft drinks e.g. 6ppm in cola. The products containing neotame can be processed by high-temperature short-time (HTST) approach. Alitame (L-α-asparatyl-N-(2,2,4,4-tetramethyl –3-thietanyl)-D-alanine) is a peptide sweetener. The aspartic acid component of alitame is metabolized, contributing 4kcal/gram to diet, but it produces negligible energy as a sweetener. It is a white, crystalline, non-hygroscopic and water-soluble
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powder. It is partially metabolised and is excreted as unchanged alitame and mixture of its metabolites [45].
Blends of synthetic sweeteners The blend of synthetic sweeteners shows synergy. They reduce the total quantity of sweetener to achieve a predominated level of sweet taste. The use of a blend is to improve the shelf life of the product and blended sweeteners pose no health safety risk. They provide a balanced profile of sweetness without pronounced after taste [27].
Mixed sweeteners Food technologists have found that the use of combination of more than one sweetener in a single system is more economical and characteristically feasible, e.g. saccharin and cyclamate, aspartame, saccharin / aspartame mixtures in soft drinks industry. The aim behind the combining of sweeteners is to imitate the taste and stability of their sugar sweetened counterpart, to create new taste by using sweeteners as flavours in the industry, to increase the safety level and to regulate the cost [46]. A variety of nutritive as well as non-nutritive sweeteners have been discovered, and many of these occupy a place in the commercial market [26]. Sweetener combinations for applications are presented in Table 13.4. However, the analysis of their organoleptic and functional characters shows that none of these currently known sweeteners can match the taste and functionality of sucrose. The differences are observed in the following parameters
1. T aste properties such as sweetness lag, e.g., Aspartame [44], undesirable lingering after taste, e.g., Stevioside having menthol after taste [47] 2. Lack in bulking properties 3. Problems of stability during food processing 4. Competitive prices, e.g., high cost of Aspartame
Table 13.4 Sweeteners combinations [35, 48]
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Sweetener
Amount (mg)(a)
Acesulfame-K
50–60
Acesulfame-K + Aspartame
30 +3
Aspartame
40–50
Sodium saccharin
30–40
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Ingredients of soft drinks Sodium cyclamate
(a)
150–200
Sodium cyclamate + Sodium saccharin
80 + 8
Aspartame + Sodium saccharin + Sodium cyclamate
10 + 4 + 30
Aspartame + Sodium saccharin
5 +15
Effective amount required to provide the sweetness equivalency of two teaspoons;
These limitations can be overcome partially in some selected applications e.g., introduction of polydextrose combined with sugar substitutes can now help avoid the bulking problems. In Canada, aspartame is the only sweetener approved for this application. Beverages contain 50–95 mg of aspartame per 100 ml depending on the brand and flavour. Aspartame-based beverages loose sweetness depending on the storage time, temperature and pH. A study shows that about 50% of initial aspartame remains in cola beverages stored at 30°C for 24 weeks and in cola syrups pH 2.4, 75% of initial aspartame remains after about 2 weeks of storage at 30°C [49]. The use of aspartame in combination with saccharine at a ratio 1:1 and stored at 20ºC, shows significantly better sweetness stability than the beverages sweetened with aspartame alone and stored at the same conditions [50]. Addition of small amount of aspartame (0.0007%) can improve the acceptance of saccharine sweetened beverages significantly [51]. Combination of Acesulfame-K and aspartame enhanced the sweetness by about 35%, while combination of Acesulfame-K and cyclamate yields excellent taste quality and exceptional storage stability. Neohesperidin dihydrochalcone (NHDC) when used in combination with saccharine, has a synergistic effect and gives improved taste perceptions [52]. In Japan, combination of fructose and stevioside has been successfully used and has good acceptance in reduced calorie soft drinks [53]. While Hoppe [54] discussed the effect of various mixtures of sucrose, saccharine and cyclamate on sweetness perception in aqueous solutions, and also the benefits of the consumers that can be derived from the use of combination sweeteners in soft drinks.
13.3.3 Current trends of sweeteners The fructose is nearly two times sweeter than sucrose while glucose is only half as sweet as sucrose. The sugar produced during hydrolysis of cane sugar is sweeter than sucrose but less sweet than high fructose syrup. “High Fructose Syrup” is nowadays used to reduce the total sugar in beverages. This is done to get predetermined degree of sweetness. Another advantage is that it helps in regulating post perennial blood sugar level in diabetic persons. The development of low calorie beverages with reference to use of multi-sweet is to combat increasing incidence of obesity. Further, the sensory properties
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of beverages sweetened with multi-sweet compared well with conventional sweeteners. The demand in low calorie sweeteners is to highlight the decline in consumption of sugar, changes in consumer’s habits and interest in health foods with increase in consumer sophistication. The concentrations of aspartame and sodium saccharin in mixed sweetener for soft drinks and syrup is presented in Table 13.5. Table 13.5 Concentration of saccharin and aspartame in soft drinks and syrups
Aspartame (mg per 100 ml) [55]
Sodium saccharin (mg per 100 ml) [48]
Cola
57.7
31–42
Orange
92.6
37–38
Lemon-Lime
50.1
26–42
Cola
347.6
–
Orange
401.0
–
Lemon-Lime
234.2
–
Flavour Soft drinks
Syrups
13.4 Acidulants The acid component is useful in modifying the sweetness of sugar. The acidulants stimulates the flow of saliva in the mouth due to their thirstquenching properties. The acids act as mild preservatives as they reduce the pH level of the product [3]. The common acidulants for beverage industry are presented in Table 13.6. Table 13.6 Commonly used acidulants in beverage industry
Acidulants
Molecular weight
Melting point (°C)
Citric acid
192.1
152–154
Tartaric acid
150.1
171–174
Phosphoric acid
98.0
42 –43
Lactic acid
90.1
18
Malic acid
134.1
98–102
Fumaric acid
116.1
299–300
Acetic acid
60.0
16–18
13.4.1 Citric acid Citric acid is the most widely used acidulant. It has a fruity character blended with fruit flavours. For example unripe lemon contains 5–8% citric acid,
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associated with malic acid in apple, apricot, blueberries, cherries, gooseberries, peaches, plum and pears; with isocitric acid in blackberries and with tartaric acid in grapes. Citric acid is a white crystalline solid and is available in powder form as the monohydrate [3].
13.4.2 Tartaric acid Tartaric acid is present in the form of acid of potassium salt. It occurs naturally in grapes. This acid can be obtained in four forms – dextro, laevo, mesotartaric acid and mixed- isomer equilibrium. The acid is produced by means of fermentation process. It is a white crystalline solid and imparts a strong and tart taste [3].
13.4.3 Phosphoric acid It occurs usually in the form of phosphates in some fruits e.g. lime and grapes. It is exclusively used in cola-flavoured carbonated beverages. Phosphoric acid bears a sharp flavour as compared to other flavours like citric acid or tartaric acid; therefore, it tends to blend better with non-fruit drinks. It is a colourless crystalline solid [3]. It is highly water-soluble and available in solution concentration of 75, 80 and 90%. It is highly corrosive so recommended to use in rubber-lined steel/food grade stainless steel.
13.4.4 Lactic acid Lactic acid is used to a greater extent in the food industry but not commonly used in beverages. This acid has a mild taste as compared to other acids and is mainly used in soft drinks as a flavour modifier rather than an acid. A lactic acid bacterium produces lactic acid through fermentation [3].
13.4.5 Acetic acid It is widely used in soft drinks industry except in non-fruit beverages. It is a colourless crystalline solid with melting point of 16°C and bears a suffocating and pungent aroma. The acetic acid in terms of its dissociation constant is found to be strongest among all other acidulants [3].
13.4.6 Malic acid Malic acid is the primary acid present in apple and the secondary acid present in citrus fruit rather than citric acid. It imparts a smoother fruity flavour than any other acid. Malic acid is a crystalline white solid with a melting point of
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100°C. It is water soluble and less hygroscopic as compared to others, so as to provide a good storage shelf-life. It is widely used in low-calorie drinks, e.g. cider (apple wine). It enhances the colour and flavour in carbonated and noncarbonated fruit-flavoured drinks [3].
13.4.7 Fumaric acid Fumaric acid is used at a lower level, as two parts of it are just equivalent to three parts of citric acid. The main drawback in its use is that the solubility of fumaric acid is lower than that of citric acid. It is not allowed for use in soft drinks directly by UK or EU legislation whereas it is permitted under Annexure IV of directive 95/2/EC (98/72/EC). It also has a tendency to stabilize the suspended matter in both flash-pasteurized and frozen fruit concentrates [3].
13.4.8 Ascorbic acid Ascorbic acid is not only used as an acidulant but it also behaves as a stabilizer. It has anti-oxidant property (provides shelf-life stability of flavours) by shielding the ingredients used in flavours against oxidation. It also acts as a browning inhibitor [3].
13.5 Colours Colourants are used in food items to enhance aesthetic appeal and also to promote sales. Colour provides a means of presenting a beverage to the consumer. The colours used in soft drinks are both natural and synthetic ones. The natural colorants are anthocyanins, betanins and carotenes. The natural colours are derived from plant sources like beetroot, cabbage and paprika, which are easily available and acceptable also. Natural carotene is used as colorant emulsion in soft drinks [10]. The carotenoids useful for soft drinks are carotene, annatto, carotenal, carotenic acid and canthaxanthin. Major ones are the synthetic colours such as tartrazine, sunset yellow, chocolate brown, caramel, amaranth and carmosine, etc. The reasons for the popularity of synthetic colours are low price, high effectiveness and excellent stability. The market for natural colours is expected to grow twice as that of synthetic colours due to improved technological performance of natural colours. The daily-consumed synthetic colours are Amaranth, Erythrosine and Allura Red [56].
13.5.1 Natural colours Nowadays consumers are more aware of their diet and health. This can be achieved by means of concept of functional foods, where the natural colours/
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pigments have recently been recognized for their health benefits. The increase in demand for natural colours as consumers increases their awareness of food ingredients. The other factors includes improved stability to oxidation, pH, heat and light, colour shades extension, increased intensity and brightness, oil soluble pigments in water dispersible forms, application of oil-soluble colour pigments in fat based media, replacement of ingredients unfriendly to consumers, development of new pigment resources. Some of the natural colours used in soft drinks along with sources and their shades are provided in Table 13.7. Table 13.7 Sources and shades of natural colours(a)
Pigment
Sources
Shade
E-No
Anthocyanin
Grape Skins, Elderberry, Red Cabbage, Hibiscus
Red-purple-blue, pH dependent
E163
Beetroot Red
Red beetroots
Pink to red
E162
Carmine
Cochineal insect
Strawberry red, orange/red hues
E120 E160
Annatto
Seeds of annatto shrub
Orange
E160
β-Carotene
Carrots, Algae, Palm synthesized
Yellow to orange
E160
Paprika
Red pepper
Orange to red
E160
Lutein
Aztec marigold
Yellow
E161
Curcumin
Turmeric
Yellow
E 100
Chlorophylls
Green-leafed plants
Green
E140,141
EU DIRECTIVE 94/36/EC; The Commission of the European Committee, 1999; EUnder consideration by EEC for ‘E’ prefix. (a)
13.5.2 Synthetic colours Synthetic colourants can be classified as water-soluble and fat-soluble colourants based on their solubility. The water-soluble colourants are Amaranth (E123, FD&C red no.2), Brilliant Blue FCF (E133, FD&C blue no.1), Ponceau 4R (E124, FD&C red no.7), Sunset Yellow FCF (E110, FD&C yellow no.6) and Tartrazine (E102, FD&C yellow no.5). The synthetic colours have been added legally into foods since 1880. The use of food colouring is carefully controlled under various legislations like EEC (European Economic Committee) and FDA (Food and Drug Administration of the USA). The permitted synthetic colours for soft drinks are presented in Table 13.8.
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Table 13.8 Synthetic colours – soft drinks
Colour
Shade
E-No.
Quinine yellow
Greenish yellow
E-104
Tartrazine
Lemon yellow
E-102
Sunset Yellow
Orange shade
E-110
Carmosine
Bluish red
E-122
Ponceau 4R
Bright red
E-124
Patent blue FCF
Bright blue
E-131
Indigotine
Dark bluish red
E-132
Brilliant blue FCF
Greenish blue
E-133
13.5.3 Global food colours market Global food market is estimated to exceed US$1,201.23 million. The rate of growth of natural colours is expected to be 4–6% per year whereas the growth rate for synthetic colours is expected to be only 2% per year. In figures, the market is split as 28% share for natural colours, 41% for synthetic colours, 20% for nature- identical colours and 11% for caramel. The natural-identical products are synthetic colours having the same structure as found in nature and the colours include β-carotene and apo-carotenal. These are only sparingly soluble in vegetable oils and fats and insoluble in water. Hence, waterdispersible suspensions and fat-soluble preparations are used in beverages. The studies show that for each 100 litres of finished beverage, 10–50 g of carotene is used.[57].
13.6 Flavours Flavours are the substances that impart the distinct characteristic sensory properties of the beverage. Flavours share fifty percent of a soft drink’s raw material cost and can be of great significance in the beverage formulation design. All the ingredients of soft drinks, such as sweetener and acidulant, contribute to the taste of a beverage, but flavours are the one, which gives the overall distinctive properties of taste and smell. A drink is made by water, sugar and acid, but the characteristic part of any soft drink is its flavour. Flavours can be broadly classified as water-soluble and water in-soluble ones. Watersoluble flavours are easily dissolvable and dispersible and relatively small amount of flavour is required, whereas non water-soluble flavours forms a neck- ring in the beverages and can bee seen as tiny suspended particles, giving an unsightly appearance. To overcome this problem, these are formulated as flavour emulsions [23].
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13.6.1 Classification Most flavours are of plant origin so are termed as natural flavours and those which do not have any existing counterpart in nature, and are synthesized are termed as artificial flavours. The mostly used flavours are made of whole aromatic plants such as mint, thyme and oregano. These are commonly called spices, which play a considerable role in beverage industry. Flavours are broadly classified as natural flavourings, nature identical flavourings and artificial flavourings [23].
Natural flavourings The natural flavourings are obtained by physical process (including drying and solvent extraction) or by an enzymatic or microbiological process from material of vegetable or animal origin.
Nature identical flavourings Nature identical flavourings are prepared using chemical processes. These are chemically identical to a substance present in natural product intended for human consumption.
Artificial flavouring substances Artificial flavourings are also chemically synthesised and these substances have not been identified in natural products, whether processed or not.
Industrial application of flavourings The flavourings that are most common in use in the beverage industry are of two types – water-miscible and water-dispersible. Water-miscible flavourings as the name suggest forms a clear solution with water at the rate of 0.1%. Flavouring substances are dispersed in a suitable carrier solvent system (ethyl alcohol / propylene glycol), which tend to exhibit variation in sensory profile due to blending and allowing them to settle, as the component may react before their stabilization. Water-dispersible flavourings are water-insoluble ones, having non-polar oil phase. These flavourings are used as emulsions (Figure 13.3), which facilitate the oil-based flavouring substances to be incorporated into beverage system. These emulsions serve dual purpose of an oil phase, that is, it provides flavour and cloud effects [3].
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Warming, mixing and dissol ution
Allow settling
Gum arabic
Premix
Homogenisation
Flavouring emulsion Figure 13.3 Preparation of flavouring emulsions
Aqueous phase contains hydrocolloids; gum Arabic is used primarily and its admixture with other gums are also used. Oil phase, usually contains essential oil or volatile (e.g., citrus oil) based with ‘weighting agent’ such as ester gum, sucrose acetate iso-butyrate, beeswax and brominated vegetable oil (restricted use, not permitted in selected countries).
13.6.2 Methods of isolation Flavours can be isolated using different methods viz., distillation (e.g. steam distillation, hydro distillation, simultaneous distillation and solvent extraction), solvent extraction and mechanical pressing.
Distillation Distillation is used for isolation of volatile aromatic flavouring compounds. In the process of distillation water or steam is used to separate flavouring compounds from their plant source. By virtue of their different condensation temperatures, they can be distilled in different fractions. A large part of flavourant is occupied by these compounds, which are extensively used in soft drinks [23].
Extraction Flavours are extracted from the plant source by using organic solvents. The solvent is then removed and flavourant is retained in its pure concentrated
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form, e.g. vanilla flavour is prepared by curing beans of the vanilla plant, which results in a flavourant known as vanillin. Vanillin is extensively used in soft drinks such as colas and cream soda formulations. Similarly, oleoresins of spices (e.g., ginger) and various fruit flavours are produced and used in soft drinks [23].
Mechanical pressing By mechanical pressing of plant source material, the essential oil as well as other flavourant compounds can be prepared; e.g. citrus processing where peel oils are collected and subjected to cold pressing. The resultant product is termed, as cold pressed oils and very often used in beverages. These may be further processed by extraction or distillation processes. The active ingredients present in these essential oil are volatile substances such as Terpenes, aromatic or aliphatic esters/alcohols. As these are water insoluble components, these have to be incorporated as emulsion in carbonated soft drinks [23].
13.5.3 Flavours in soft drinks:
1. Citrus flavours; 2. Orange flavours 3. Lime 4. Grapefruit 5. Cranberry 6. Strawberry 7. Cherry 8. Pomegranate 9. Pineapple flavours 10. Coconut and winter fruits.
In carbonates, new flavours include mango tango, apple splash, fanta, raspberry and cranberry, Britvic 55. Day by day, the demand for flavours is increasing. The current trend in flavourings is demand for popular flavours, flavour blends, nutraceutical flavours, sport drink flavours and fortified beverage flavours.
13.7 Clouding agents Clouding agents should impart the following attributes to the finished carbonated beverage: (1) products should remain stable for at least three
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months without ‘ringing’, ‘creaming’ or ‘sedimentation’. (2) The clouding agents should not adversely interfere with the colour, taste or odour of the finished beverage. (3) The clouding agents must satisfy the legal requirements of the country in which the drink is consumed. Some of the examples of clouding agents are pectin, gelatin, glyceryl acetate, brominated vegetable oils, sucrose acetate, dibenzoate and tribenzoate etc. The functionalities and characteristics of two important clouding agents, viz. ‘Pectin’ and ‘Gelatin’, are discussed in the following sections.
13.7.1 Pectin Pectin (Figure 13.4) is found to be a commonly used polysaccharide and it has a complex structure. The majority of the structure consists of homopolymeric partially methylated poly-α-(1 4)-D-galacturonic acid residues, but there are substantial ‚hairy‘ non-gelling areas of alternating α-(1 2)-L-rhamnosylα-(1 4)-D-galacturonosyl sections, containing branch-points with mostly neutral side chains (1-20 residues) of mainly L-arabinose and D-galactose (rhamnogalacturonan I). Pectin may also contain rhamnogalacturonan II side chains containing other residues such as D-xylose, L-fucose, D-glucuronic acid, D-apiose, 3-deoxyD-manno-2-octulosonic acid (Kdo) and 3-deoxy-D-lyxo-2-heptulosonic acid (DHA) attached to poly-α-(1 4)-D-galacturonic acid regions. D-galacturonic acid residues form most of the molecules in blocks. The molecule does not adopt a straight conformation in solution, but is curved with a large amount of flexibility. The `hairy‘ regions of pectin are even more flexible and may have pendant arabinogalactans. The carboxylate groups tend to expand the structure of pectins as a result of their charge. Methylation of these carboxylic acid groups forms their methyl esters which are more hydrophobic, and hence have a different effect on the structure of the surrounding water.
Figure 13.4 Pectin
The properties of pectins depend on the degree of esterification, which is normally about 70%. Low methoxyl-pectins (< 40% esterified) gel formed due to calcium di-cation, bridging between adjacent two-fold helical chains forming ‚egg-box‘ junction zone structures, and a minimum of 14–20 residues
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can cooperate. Gel strength increases with increasing Ca2+ concentration but reduces with temperature and acidity increase (pH < 3). If the methoxyl esterified content is greater than 50%, calcium ions show some interaction but do not form gel. The controlled removal of methoxyl groups converting high methoxyl pectins to low-methoxyl pectins is possible using pectin methylesterases. High methoxyl-pectins (> 43% esterified, usually ~67%) gel by the formation of hydrogen-bonding and hydrophobic interactions in the presence of acids (pH ~3.0, to reduce electrostatic repulsions) and sugars. Low methoxy-pectins (~35% esterified), in the absence of added cations, gel by the formation of cooperative ‚zipped‘ associations at low temperatures (~10°C) to form transparent gel. The rheological properties of low methoxy-pectins are highly dependent on the salt cation, salt concentration and pH [58]. Pectins are mainly used as gelling agents, but can also act as thickener, water binder and stabilizer. Low methoxyl pectins (<50% esterified) form thermoreversible gels in the presence of calcium ions and at low pH (3–4.5), whereas high methoxyl pectins rapidly form thermally irreversible gels in the presence of sufficient (65% by weight) sugars such as sucrose and at low pH (<3.5); the lower the methoxyl content, the slower the set.
13.7.2 Gelatin Gelatin [59] is a substantially pure protein food ingredient, obtained by the thermal denaturation of collagen. It possesses fruit juice’s clarifying properties. In ‘fining’ applications, gelatin reacts with polyphenols (tannins) and proteins in fruit juices forming a precipitate, which settles leaving a supernatant, which is stable to further, give cloud formation with storage time. Traditionally, low bloom strength gelatins are used but it has been shown that high bloom strengths are equally effective. But, practically low bloom strength gelatin is used as it is cheaper and easier to mix into the bulk of the cold juice before gelation can occur. The haze-forming activity of a polypeptide depends greatly on its proline content. Haze-forming polyphenols have at least two binding groups, each of which has at least two hydroxy groups on an aromatic ring. The protein/ polyphenol ratio has a strong influence on the amount of haze formed; the largest amount occurs when the numbers of polyphenol binding ends and protein binding sites are nearly equal. This has important consequences for turbidimetric methods used to measure haze-active proteins and polyphenols in beverages. The ratio also influences the effectiveness of a number of stabilization procedures [58].
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14 Processing technology
14.1 Introduction The processing technology involves various critical steps such as raw material handling, pulping and extraction, clarification, concentration, syrup preparation, blending, pasteurisation, carbonation, de-aeration, filling, packaging and cleaning.
14.2 Handling Raw Material The raw material viz., fruits or spices, is delivered in lorry loads to a reception area, washing and sorting is done to remove foreign particles. Washing is done by different kinds of equipments such as a rotating rod-cylinder with a helical screw inside to push the fruit along; moreover, it is fitted with jets of water, forced with a centrifugal pump. This type of equipment is mainly used for mandarin oranges [60]. Another important step in raw material handling is sorting out on a continuous woven belt, made of woven metal. The primary material for the manufacture of soft drinks is either the juice or pulp from the fruit.
14.3 Pulping and Extraction Soft fruits such as papaya, can easily be pulped by using a pestle and mortar or by hand. There is a wide range of hand-operated pulpers available or multipurpose kitchen-scale equipment such as blenders can be used, if electric power is available. At industrial level, this process is done in pulpers, which brush the fruit through a sieve and eject the skin and stones as well. Juice can be extracted from fruit in several ways such as using a fruit mill, hand pulper / sieve or a fruit press. Crushing with a mortar and pestle and then sieving through a muslin cloth can also be done. In case of citrus fruit juices, extraction is done by squeezing the fruit and then sieving [60]. The equipments used for pulping and extraction are roller-type press, plunger-type press and
211
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continuous screw-expeller press. In the continuous screw-expeller press, the working principle is that fruit segments are fed through a hopper at one end of a feeding screw, revolving inside a conical section, which has perforations through out. The juice flows out through these perforations. In other type of pressing equipments like in roller-type press, rollers are made up of wood or hard granite to crush the fruits for juice extraction, whereas, in plungertype press the fruits are held in an inverted cup, and they are pressed by an automatic adjustment against a metallic cone fitting in the cup.
14.4 Clarification The recent development in the clarification of juice is the membrane processing, mainly ultra filtration and micro filtration. The causes of the popularity of membrane processing are their advantages over the traditional methods of clarification. The membrane processing is found to be efficient as there is no phase change during the process [61]. This also eliminates the need for heat generating equipments, condensers and heat transfer equipments [62]. It also helps to retain enzymes on the basis of the pore size e.g. depectinization and polyphenoloxidase enzyme can be retained, otherwise they can cause enzymatic browning. It can be continuous and automated and thus, reduces cost and labour. Juices are not subjected to any heat treatment as they are cold and sterilized using aseptic packaging. The membrane processing reduces processing time, is simple, requires less staff, less risk, no use of filter aids and less loss of product due to less spoilage such as change in colour, odour etc. [63–65]. The ultra and membrane filtration processes are mainly employed for clarification of fruit juices such as apple fruit juice [66]. The overall extraction efficiency of ultrafiltration is 95–97% as compared to 90–93% efficiency of the traditional processing. The clarification of juice through traditional as well as membrane processing is presented in Figure 14.1.
14.4.1 Application of Enzymes in Clarification Enzymes are added to improve yield and facilitate clarification. They are necessary to get 70°B concentrate [69]. The common enzymes of interest are pectin methyl esterase and polygalactouronase. Their function is to breakdown the negatively charged pectin coat to expose the positively charged underneath. These positive charges combine with other negative charges of protein-carbohydrate particles to cause flocculation. The fining agents such as gelatine, bentonite or kiesel sol cause aggregation of flocculation due to charges, neutralization and adsorption. Then separation is done by
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clarification. Commercially pectinases are added from 0.005% to 0.015% and treated for 6–8 h at 15 to 20°C or 1 to 2 h at 55°C [68]. The application of polygalacturonase is to reduce the particle size and remove web-like aspect in apple [70]. Fruit sorting and washing
Pressing
Pomace
Aroma stripping
Enz ymatic depectinization
Addition of fining agent
Ultra / microfiltration
Retentate Evaporation to 70 °B
Polishing filtration
Permeate
Pasteurization and packaging
Blending and diluting Packaging
Storage and shipping
Figure 14.1 Clarification of juice through traditional as well as membrane processing [67, 68]
14.4.2 Filtration Principle Filtration is a phenomenon of separating particulate matter in a continuous liquid using a permeable barrier [67]. The particulates accumulate on the membrane surface and build up a cake, and the filtered liquid is called filtrate. The deposition of cake will restrict the filtration rate but the problem can be overcome by cross-flow filtration, where the fluid flow is tangential to the membrane surface, which minimizes the build up of cake. Clarification of juice through the membrane processing as well as the traditional filtration is presented in Figure 14.1.
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14.5 Concentration The traditional methods of concentration are multi-stage vacuum evaporation, and the thermal effects of evaporation,results in colour degradation, cooked taste and in a loss of fresh fruit flavours. The alternative to these losses is development of new technology for concentration of juices such as reverse osmosis, freeze concentration, sublimation concentration [71, 72]. However, each process shows one or the other disadvantage such as reverse osmosis has limitation of achieving not more than 25–30°B concentration due to high osmotic pressure. Thus, to overcome the shortcoming of reverse osmosis, membrane processes came into picture. This includes membrane distillation, osmotic distillation and integrated membrane processes. The aim behind using the membrane processing for juice concentration is to improve product quality and reduce energy consumption, and this is the most promising alternative for concentration of juice. The different methods used for concentration are reverse osmosis, direct osmosis concentration, osmotic distillation, Integrated membrane process.
14.5.1 Reverse Osmosis The advantages of reverse osmosis (RO) over traditional evaporation are lower capital investment, low power consumption and low thermal damage to product [73]. There is no phase change in water removal and moreover, it is carried out at low temperatures. The concentration of a variety of fruits, such as apple, pears, grapefruit, kiwi, pineapple, passion fruit, has found to be excellent by reverse osmosis [74–79].
14.5.2 Direct Osmosis Concentration This process is performed at low temperature and low pressure to maintain original characteristics such as flavour, colour and odour of the fruit. To establish an osmotic pressure gradient across a semi permeable membrane, an osmotic agent is used which facilitates the removal of water from a single- strength fruit juice. An osmotic agent is generally solid, highly soluble in water, does not impart any colour and flavour to the foodstuff and does not pass through the membrane. Higher concentration of dissolved solids provides higher osmotic pressure. The most commonly used osmotic reagents are sodium chloride, sucrose, glycerol, cane molasses or corn syrup. The osmotic pressure of an osmotic agent is higher than that of concentrated fruit juices such as 74°Brix high fructose syrup i.e. 270 bar is greater than that of 90 bar for 42°Brix pulpy orange juice [80].
14.5.3 Osmotic Distillation Osmotic distillation (OD) is a recent membrane process [81], also called as osmotic evaporation [82] or isothermal membrane distillation. This is used
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to extract the water from aqueous solutions under atmospheric pressure and at room temperature without subjecting the product against high temperature [83]. Therefore, it is mostly adapted to the concentration of heat-sensitive products like fruit juices [82, 84–86]. This involves separation of two aqueous solutions: a hypertonic salt solution and a dilute solution. There is generation of a vapour pressure difference at the vapour–liquid interface due to difference in solute concentrations and further difference in water activity of both solutions. The water transport through osmotic distillation occurs as water evaporation at vapour-liquid interface, convective vapour transport through membrane pore and condensation at the membrane/brine interface [87–92]. The salts, which are used here, include MgSO4, CaCl2 and KH2PO4. The potassium salt of orthoand pyrophosphoric acid has certain advantages like high water solubility, low molecular weight and safe to use [82, 89, 90, 93].
14.5.4 Integrated Membrane Processes This process appears to be highly valuable for high quality concentrated juices. Fruit juices such as orange juice have high solid and pectin content, which creates a viscous stream when processed under RO or OD and results in a lower permeate flux. Moreover, using a single method of concentration cannot reach concentration of more than 25–30°Brix. Combination of RO with MF or UF for concentration, the flux increases as viscosity decreases [94]. The UF is used to separate juice into the pulp and serum prior to heat treatment to retain flavour and colour. The retentate contains all suspended solids, pectin and spoilage micro organisms. It is subjected to heat treatment quickly and then recombined with RO concentrate [95]. The serum contains almost all the flavour and aroma, which is concentrated to a level of 42°Brix by RO.
14.6 Syrup Preparation Syrup is a sugar solution with required brix. Preparation of syrup involves the following steps: measured amount of treated water is pumped into tank, agitator is started; measured amount of sugar is added and mixing is done; resultant sugar solution is called a simple syrup, which is pumped through a filter to second tank. The size of filter is usually in the 5–20 mm ranges. Thus, the prepared syrup is used for the preparation of soft drinks [23].
14.7 Blending Various types of blenders (Figure 14.2) are available to blend all the ingredients. Syrup is dosed through a mass flow meter, whereas water is dosed volumetrically through a magnetic induction flow meter. This step is very important so as to get the required Brix. Other ingredients are also added
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one by one to get a uniform product. At the industrial level, blending is done in three routes: batch, flip-flop and continuous blending [3].
Figure 14.2 Blender
14.7.1 Batch Blending The ingredients are mixed in a large tank. The minor ingredients are first mixed in smaller tank and later on shifted to a larger tank. These may need heating / cooling to maintain temperature. To increase the efficiency of blending, a variety of stirrers and mixers are available commercially.
14.7.2 Flip-Flop Blending This is a type of batch blending where a batch is prepared in one mixing tank, then fed to the line and second batch is delivered to the line directly as first finished, so batches flip-flop between the tanks.
14.7.3 Continuous Blending The blending is done on a continuous basis. This is achieved by making use of the positive displacement pump or flow meter to control the stream through pumps and valves. This is used when limited streams are there such as water, sweeteners, premix 1 and premix 2.
14.8 Pasteurisation Generally, hot water plate or tubular hot exchanger heats the drink to a desired temperature and is held at that temperature for a specified period of time. The common methods of pasteurization are flash pasteurisation and in-pack
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pasteurisation. Flash pasteurisers have a regenerative section, which serves the purpose of saving the energy. Here the hot product going out heats the incoming raw product, and in return it gets cooled. Thus, regeneration of energy occurs. To make the process microbiologically safe, it is important that the correct conditions are maintained during the complete operation. Inpack pasteurisation is considered to be most secure form of hot treatment. The pasteurisers have two zones: first have a heating zone and a superheat zone, which brings the temperature of the product to the desired level. The second is the pasteurizing zone to hold the product for the specified period of time. Then the product is cooled to below 30°C. An example of this type of pasteurisation is retortable process where packs can be treated at temperature above 100°C in a retort and then cooled [3].
14.9 Carbonation Nowadays, carbon dioxide containing beverages are very popular.. Consumers enjoy their “pleasurable and sought after” sensation. The sensations are either of mechanical origin or of chemo-genic origin. Mechanical origin is due to the bursting of CO2 bubbles stimulating mechanoreceptors on the tongue, or chemo-genic origin by formation of carbonic acid (H2CO3) in a reaction catalysed by carbonic anhydrase, which stimulates polymodal nociceptors in the oral cavity [96]. Whenever concentration level of CO2 goes 3–5 times higher than the saturation equilibrium value, bubbles appear. It also depends on the pre-existing gas-liquid interfaces. These bubbles enhance the mass transport of CO2 when the bubbles impinge upon the tongue and increase the “tingling” sensation [97, 98]. In soft drinks, polysacharides or hydrocolloids are used as thickeners, stabilisers and gelling agents, to improve “mouth feel” and to aid in carbonation retention due to the augmentation of the tensioactive charge of the liquid. As the liquid phase gets modified, it may affect the visual or taste perception of effervescence of a drink.
14.9.1 Components of Carbonation Unit (Figure 14.3) The components of the carbonation unit are venturi, two stainless steel tanks, pump, refrigerated bath, sensor for monitoring the dissolved CO2, liquid and gas ducts made with Rilsan tubing [97].
Working principle Injecting the gas into a pressure-sealed vessel can do carbonation [97, 98]. The working principle is that the system is pressure-sealed, as the internal pressure increases, the CO2 solubility increases, and up to 9 g/l of CO2 can be dissolved. Gas can be injected continuously through a venturi into the
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liquid flow. Thus, mixing is much more efficient so as to achieve higher carbonation levels. The beverage is collected in pressurized tanks or directly in bottles. This is the common process in use by the carbonated drinks industry.
Figure 14.3 Carbonator
Carbon dioxide monitoring Monitoring of CO2 concentration in the liquid during the carbonation process is very important. The most common devices used for monitoring CO2 concentration are the Severinghaus electrode [99] and the infrared detector. The Severinghaus type CO2 electrode comprises a pH electrode with a thin layer of bicarbonate buffer solution. The whole system is encapsulated by a thin, gas-permeable membrane. CO2 diffuses through the gas-permeable membrane and equilibrates with the internal aqueous solution and alters its pH. The electrode monitors the change in pH in a time period of 5–15 minutes. The infrared absorption detector is preferred over CO2 electrode due to quick response times and reliable results. But the disadvantage is that they are bulky and expensive, and only applicable to gaseous CO2. Other devices include gas chromatography (GC) and mass spectrometry (MS). MS gives real-time measurements but its price is very high, whereas GC is less expensive but cannot be used for real-time measurements. Thermal conductivity detectors
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[100] are also used to record the difference in conductivity between a reference gas N2 and CO2 after diffusion in a measurement chamber. Thus, the monitoring device should be such that it gives real-time measurement, which is a real challenge during carbonation process.
14.10 De-aeration (Figure 14.4) The air present in the product leads to its deterioration and also gives a false reading of CO2 level due to partial pressure involved. To overcome these shortcomings de-aeration is done. The reduction in the level of air is done below 0.5 ppm. Hence, the shelf-life of the product can be enhanced due to the deterioration of risk caused by the presence of O2. Fobbing is the type of deterioration that occurs due to the presence of CO2 and air. Higher the air content, lower the level of CO2 held during carbonation. The methods followed for de-aeration are reflux and vacuum. The de-aeration method is applied to water before mixing the syrup, instead of applying to the final product. In reflux de-aeration, a positive CO2 pressure is applied in a sealed vessel and the air attaches to the carbon dioxide due to nucleation and driven off through a pump. In case of vacuum de-aeration, it is to atomize water into a vessel held under a vacuum. As the atomized water is exposed to vacuum, the air is stripped out. Often the vacuum de-aeration is followed by reflux de-aeration, which results in an air content of less than 0.5 ppm in the final product [3].
Figure 14.4 De-aerator
14.11 Filling The filling of a drink into a container is achieved under gravity. The flow rate also depends on the head difference between the filter bowl and the container. The pressure applied at the top of the filling bowl provides the driving force
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to fill the container. The filling of container is influenced by the pressure at the top of the bowl, viscosity of the liquid, diameter of the filling tube and length of the pipe [3]. Filler is made up of stainless steel (Grade 316) to withstand chemical attack from both products as well as from cleaning process. There is a central frame having drive motor and pipe work supports. Each valve is piped to central frame via a rotary valve. The different types of fillers are gravity filler, counter-pressure filling cycle, etc.[3]. In gravity filler, the important thing is to seal the container near the filler bowl, so that there is no leakage. The filling bowl is filled to a required level maintained by means of float valve, which creates a constant pressure head during filling. When valve is opened filling occurs. Due to the pressure of the vent, gas gets expelled. The rate of flow of the liquid to the container is proportional to the rate of flow of the gas displaced. The filling continues till the time the pressure within the vent tube becomes equal to the filling tube pressure heads. At this equilibrium stage, the liquid flow stops and thus, the filling valve can be closed. In the counter pressure filling (CPF) filler, container is sealed to the filler bowl and gas valve opens. The gas within the bowl headspace flows under pressure into the container and displaces the air at the atmospheric pressure. Then the air is vented out to the atmosphere. The advantage of CPF cycle system is that before filling the bottle, air content can be reduced but it cannot be eliminated completely. As soon as the equilibrium is attained, liquid valve is opened and gas valve is closed. A short settling period is very important before the liquid valve is closed. This is required to allow the gas to vent off within containers, which otherwise cause fobbing. To control fobbing, fillers should operate up to 22°C temperature, because higher temperatures will tend to increase the risk of fobbing. Other types of fillers which are electronically controlled such as volumetric and capacitance probe fillers are also available. The capacitance probe filler has a capacitance probe to detect the point where filling has to be stopped. The swirl valve contains this probe in its centre. As the filling is over, the probe senses and reduces the filling rate. Another type is the volumetric filler or a mass flow meter. Here the filling volume is decided by a magnetic inductive volumetric flow meter. These fillers with probe are also connected to electro pneumatic valves, which enable accurate control of the process. The important thing to be considered is that these valves have to be kept clean which is critical for the operation.
14.12 Packaging Bottles are unloaded on to the empty bottle conveyer system. A decrate unloads the returnable bottles from crates, passes them on to a bottle washer to clean them, and finally to a bottle sorting area. In line to this system, de-
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cappers and de-labellers are also required. Then bottles are transferred in bulk towards the filler. Bottles are firstly rinsed and then exposed to UV light for sterilisation. After rinsing, bottles are filled and then capping is done. Fillers are so equipped that they can handle a range of bottles by changing parts. The speed of the filler depends upon the number of valves and physical properties of the liquid. Fillers are equipped with vacuum system to speed the filling rate. Filling machines are highly sophisticated as it provides cleaning of bottles through steam, pre-evacuate it to reduce oxygen levels, reduce fobbing using a long tube-filling valve to fill it. Filling should be done to a precise weight and volume [3].
14.13 Clean-In-Place (CIP) System CIP can be defined as the process of circulating various chemical solutions along with water through the process equipments in the assembled state [16]. The aim of circulating these chemical solutions under higher turbulence is to remove solid debris and micro organism. The best results can be obtained by following a suitable combination of temperature, time, physical action and chemical concentration. CIP is efficient as this facilitates the cleaning of all the components in their respective places, which has been in contact with the product. It increases plant utilization as equipment can be cleaned as soon as they are empty. It requires minimum manual effort as automated designs are available. CIP is absolutely safe, as the personnel are not required to enter the hazardous environment. This gives satisfactory result as cleaning is perfect. This improves the quality and shelf-life of the product. Pre-rinsing is done to reduce the work of detergent as it facilitates the removal of loose soil. Remaining soil is removed by recirculation of detergent. The CIP cycle depends on three variables: chemical strength, exposure time and cleaning temperature. The intermediate rinsing is done to remove detergent with fresh water. Recirculation of hot water (above 90°C) for >20 minutes is practised to destroy remaining microbial contamination.
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15 Quality control
15.1 Introduction Quality control can be defined as that industrial management technique by means of which, product of uniform acceptable quality is manufactured. The quality control comprises of two words i.e. quality and control. Quality is the inherent property of a product with respect to its shape, dimension, composition strength, workmanship, adjustment and colour. On the other hand, control refers to the sum of all the means whereby quality standards could be maintained. Control is a broad term; it includes the product to be processed, workmen and their operation methods. Quality control deals with control of all those factors which are responsible to increase the degree of excellence of the product. The main functions of quality control are as follows: • It helps to achieve a high standard of quality in the product. • It meets the requirement of the factory. • It takes effective inspection so as to introduce effective systems of production. • It includes quality control right from raw material to the end of the product formation. • The standards for raw material, process and the product to be developed by quality control only. • Quality control develops plans for inspection, analysis, sampling and acceptance of the product. Quality control system is composed of different wings viz., system quality control, production quality control and microbial quality control.
15.2 System quality control System quality control is in relation to raw material quality and cleaning (e.g., bottle washing) and inspection.
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15.2.1 Raw materials The quality of finished product depends upon the degree of control required for any raw material. The quality of raw material determines the quality of the finished product. The quality control system of raw material includes water, sweetening agents (e.g., sugar), flavours (e.g., fruit juices), acidulants, preservatives and carbon dioxide.
15.2.2 Water The quality control of water is important as it contributes the 90% part of the soft drinks. The key quality parameters are alkalinity, colour and mineral content. If these exceed beyond their limits, these may affect product flavour and appearance. The quality parameters of the water used in soft drinks are provided in Table 15.1. The treatments used to obtain quality water are the following:
Cold lime softening Use of ferrous sulphates Chlorine treatment Demineralization Ozone treatment Reverse osmosis
1. 2. 3. 4. 5. 6.
In addition, the water used for boiler is also need to be treated as above. Further, the water used for final rinsing should under go ion-exchange softening to correct its pH. Table 15.1 Quality parameters for water used in soft drinks
Parameters Physical and organoleptic Taste Odour Colour Turbidity Sediments Chemical Total dissolved solids Alkalinity Chloride Sulphate Fluoride Nitrate
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Maximum level Should be tasteless Should be odourless 5 Hazen units 1 mg/l Nil 500 mg/l 50 mg/l 250 mg/l 250 mg/l 2 mg/l as F 10 mg/l as N
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Organic matter
5.2.3 Sugar There are two grades of sugars suitable for use in soft drink production. The granulated sugar (Gran – EEC grade) is the most commonly grade used in soft drink industry [1]. The specification for granulated white sugar is presented in Table 15.2. The manufacturers have begun using grade liquor prior to crystallization; the grade liquor is cheaper than granulated sugar which is recommended for concentrated drinks and not for carbonated products. In sugar the quality parameters are degree brix, colour, taste, odour and temperature. In the soft drink industry, the storage of sugar is a critical task. The storage place should be separate, dry and rodent proof. Moreover, the temperature and relative humidity (60% RH at 10–20°C temperature) conditions need to be maintained. The bagged sugar storage should be done on pallets with proper circulation of air. Table 15.2 Specification for granulated white sugar
Parameters
Specification
Ash Arsenic Colour Odour Sulphur dioxide Moisture Purity Lead Taste
> 0.02% <1 ppm <25 ICUMSA* units Free from abnormal odour <15 ppm < 0.05% (loss of weight on drying) >99.7% by polarization <0.5 ppm Free from any foreign taste
*International Commission for the Unification of Methods of Sugar Analysis (1978). 15.2.4 High fructose glucose syrup The glucose isomerase is capable of converting glucose to the sweet fructose. This has been observed as an alternate for sucrose. High fructose glucose syrup (HFGS) is supplied in liquid form with 72°Brix. At higher concentration, handling and storage of sugar is critical as highly viscous and may get crystallized. The quality control parameters applicable for HFGS are low colour, free from turbidity, free from foreign taste and odour and there should not be any flocculation. The composition of syrup is such that 91% of the solid content should be composed of glucose and fructose, where at least
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41g per 100g of total solid is fructose only. The syrup should not be exposed to a temperature greater than 45°C and a pH of 4.0±0.5 [1].
15.2.5 Saccharin The important consideration here is that on heating, saccharin decomposes in the presence of acids,so boiling is avoided. Another problem is that it is insoluble, so sodium bicarbonate solution is required to dissolve it [1].
15.2.6 Carbon dioxide The supply of CO2 can be done in the form of dry ice, as a gas in cylinders at ambient temperature or as a liquid by refrigerated tanker. The main impurity in CO2 is oil introduced during its manufacture. Other impurities are off-odours and off-tastes from fermentation process. Thus, quality control parameters have to be followed.
15.2.7 Fruit juices Fruit juices should not contain any viable yeast cells and it should be sterile. Analysis of juice includes taste, colour, pulp appearance, acidity, brix, pectinase activity, preservative type and microbial content. The fruit juice should be completely sterile to use in the soft drink industry [1].
15.2.8 Acidulants In laboratories and also in on-line processing, determination of acid content is carried out by titration method. Now-a-days, in soft drinks industry new automated method of titration is followed that is sequential injection titration which is simple, fast, automated and precise. Any automated method of analysis is most expensive method. High degree of automation, cost effectiveness and high speed are the requirements of process control in an automated method of analysis. The main advantage of this method of titration is that the concentration requirement of reagent is in micro quantities. The acids like citric acid, phosphoric acid, lactic acid, fumaric acid and ascorbic acid are the common acidulants used in soft drinks industry. As these acids determine the sensory quality of soft drinks, the determination of total acidity becomes very important. In sequential injection titration, a pH electrode is used as a detector for total acidity measurements. The principle of working is based on the concept of flow and gradient exploitation where the distance between the two points of identical amplitude is proportional to the logarithm
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of acid concentration. In this method of titration, the titrant acts as a carrier which carries the sample along with it as a mixed in the chamber before detection.
15.2.9 Preservatives To prevent the growth of yeasts, moulds and bacteria in food and beverages, preservatives such as sorbic acid, benzoic acid, p-hydroxy benzoic acid ethyl, isopropyl, propyl, isobutyl, and butyl esters (parabenes) [101] need to be added. The commonly used preservatives are sorbic and benzoic acids, but they differ in their pH requirement to show antibacterial activity. Benzoic acid is mainly used for acidic food products such as soft drinks and other fruit based beverages, as its activity in the pH range of 2.5–4.0 is high. Parabenes are effective at much higher pH 3–8, whereas sorbic acid is also effective at high pH only. To ensure the level of preservatives in the soft drinks, it is necessary to determine their level. The traditional methods of their determination are titrimetric, spectrophotometerric [102] and thin layer chromatography methods. The traditional methods have their limitations such as several extractions, evaporation and derivatization steps (GC) [102]. As a pre-treatment, solid phase extraction has been introduced to minimize the sample volume, solvent volume, purification and evaporation steps in HPLC, GC, etc. [103–108]. In 1999, another new extraction technique has been developed known as stir-bar sorptive extraction (SBSE), using stir-bar coated with 50–300 µL polydimethylsiloxane (PDMS) [109].
15.2.10 Bottle washing Returned bottles may contain straw, paint, grease, cigarette butts, and cement. The bottles need to be cleaned properly before their reuse. To clean the bottles and to make them sterile, efficient washing is required. Washing of thousands of bottles at a time, is not an easy task. Thus, bottle-washing system should be equipped with automatic washing machine, so as to result into an efficient method of washing. The bottle washing system has a detergent section, which is preceded by a pre-rinse with water. Final wash is done by means of warm water as well as cold water to remove the detergent residue. The capacity and efficiency of washing system is determined by some factors such as contact time, strength of the detergent and temperature of the detergent. The commonly used detergent is caustic soda. Due to some of its undesirable characters such as de-flocculation and emulsification, it has to be blended with other chemicals. Regardless of the fact that how efficiently washing is done, some bottles will not be cleaned /sterilized properly, therefore bottle inspection also plays
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an important role here. The inspection can be done visually or electronically. The visual inspection section includes an inspection screen with lights and reflector, which gives an on line inspection. Electronic inspection system is another system, which can be used efficiently in places where there are chances of retention of detergent inside the bottles. If the inspection is still not up to the mark, then automatic residual liquid detergents are also available. The working principle of these machines is to induce interference of optical microwave or gamma rays emission and detection of changes in dielectric capacitance between bottle and conveyer. This is further linked to the electronic bottle rejection system of existing electronic bottle inspector, which induces a signal to stop the conveyor [1].
15.3 Product quality control 15.3.1 Preparation of syrup The quantities of sugar and water must be measured accurately. Weighing method is used for granulated sugar and bagged sugar; bags are weighed on a platform scale. The regular calibration of weighing equipment is important and the equipment should be free from caked dust. Similarly, water is measured by weight or by volume (using a flow meter). Weight method is found to be accurate whenever flow meter is used to measure water for the preparation of syrup and the flow meter should have a repeatability of at least ± 0.2% at a selected flow rate. It is to be designed such that water is always measured at same flow rate and a constant pressure drop across the meter. In cases where water pressure fluctuations are there, a flow control device is preferred. A quick closing valve has to be used between water meter and syrup tank. Agitators are also used in the tank when sugar is allowed to mix in the tank. The sugar syrup has to be filtered to remove small foreign particles. Mainly horizontal and vertical plate type filters are used for clarification of sugar syrup [1].
15.3.2 Addition of ingredients All the ingredients like acids, preservatives, colours, flavourings, fruit juices and clouding agents should be added to simple sugar syrup in order to the chemical nature of each ingredient. If acid is added, the preservative like benzoic acid has to be added and dissolved prior to acid addition as it has low solubility in the presence of acid [1]. Syrup de-aeration is done to remove air entrapped during dissolving and mixing. Other wise it leads to fobbing during filling, when filtration is done. The time taken for aeration varies with temperature, viscosity of syrup and
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depth of the syrup in the tank. The cost of syrup represents a large proportion of the overall cost and any mistake at this stage can affect the quality of finished product. Physical, chemical and organoleptic tests are carried out to confirm that the syrup contains all the ingredients in the required quantity. Hydrometer or refractometer can be used to determine the percentage of soluble solids, titration for acids and other qualitative and quantitative tests. Every time the taste and appearance of beverage should be confirmed with a standard for colour, taste and off-odour. Inversion of sugar is an important and common process where syrup is stored overnight or over the weekend. The sugar inversion depends on temperature and acidity of syrup. The reaction involved is as follows:
C12H22O11 + H2O → C6H12O6 + C6H12O6 In this reaction, some of the water is converted into solids, which gives a slight decrease in the total volume of syrup. So prior to filling, it is important to measure dissolved solids by hydrometer so as to give a product of target strength [1].
15.3.3 Carbonation It includes two types – pre-mix and post-mix. Post mix includes filling the bottle with an accurate volume of flavoured syrup and water which has to be added before carbonating soft drinks. Further, capped bottles are inverted to mix the contents. This is now replaced by premix, where flavoured sugar syrup and carbonated water are filled in proportion along with mixing. The various quality parameters in quality control aspects are syrup, water ratio, carbonation and the height of filling.. To get the ratio control for sugar with water, refractometer is used. But there is some limitation in refractometer; it measures only dissolved solids and insoluble materials like fruit pulp having no effect on the refractive index of the solution, leading to the clogging of the prism. As soft drinks are multi-complex mixture the overall refractive index is the product of the individual refractive indices due to concentration of components [110]. Hence, overall refractive index is affected by the concentration of individual ingredient. Another instrument is in-line monitoring densitometers. It is found to be better than refractometer but applicable for non-carbonated beverages. The artificial sweetening agents cannot be measured by measuring solid content since its concentration is very low so it is usually measured by colour or acidity in the beverage. Carbonation is measured in volumes of CO2. This includes the measurement of pressure and temperature of gas in bottles and then consulted
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with the chart to get the values in terms of volume of carbonation. Another sophisticated instrument is infrared spectrophotometry which is suitable for very high-speed lines. The proper recording of all the quality control tests has to be done and must be compared with standard charts. During bottle filling, care has to be taken that the bottle breakage occurs frequently. The breakage depends on the shape, type of bottle, filling pressure and the part of bottle which has to be burst. Therefore, a clean-up procedure has to be there at places of burst and the incidence of burst should be minimized as much as possible.
15.3.4 Capping Capping is an important part of production of a quality product. Capping is done by means of crown or aluminium screw closures. The quality control parameters are testing of crimp diameter using gauges and crown leakage by inspection only. The essential thing is the regular cleaning of hopper and crown chutes to check dust build up. The proper sealing and its visual examination after application and in stock are required.
15.3.5 Labelling The visual application of the product is under the direct influence of the quality of labelling. To achieve this there should be proper maintenance of labelling equipment, correct choice of paper and adhesive as well.
15.3.6 Finished product inspection This is the stage where quality control is little as product has already been prepared. The finished products quality depends upon the qualities of the raw material and process control. Thus, the inspection of finished product is done to check whether it follows the required standards. Before sending the product to the market, the quality tests should be done on suspected cans. If suspected cans are filled, the cost will be many times than that of the cost of empty cans due to loss in production of saleable product and destruction of cans. Moreover, the quality control at the finished product is limited if effective quality control of raw material is practiced. The quality control is done at retailer outlets also for confirming the shelf life of the product, which will necessarily depend on the product formulation, packaging and storage conditions. To obtain a satisfactory shelf life, products have to be filled in ultra-violet absorbing glass. This minimizes the effect of light and loss of colour. Canned products produce off-taste and colour changes due to the reaction of iron with canned product; they loose flavour and age with time. Thus, soft drinks are known to be intermediate shelf life products with extension of 12 months [1].
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15.3.7 Packaging The packaging has a significant effect on the quality of soft drinks. The manufacturer as well as the users of cans and bottles must follow the acceptable quality level for various parameters. In the case of cans, the shelf life of the product depends on the interaction of cans and product. The physical examination of beverage cans for metal pick up (iron, tin, aluminium), appearance, lacquer breakdown and corrosion is necessary. The major objective of user should be to monitor the quality aspects so as to improve the performance of package quality in conjunction with the manufacturer. The deliveries are sampled according to BS 6001. The quality tests preferred on bottles include visual examination of defects, glass weight, height of filling capacity and other dimensional measurements. The internal pressure of bottle is measured by recording the number of burst per 1,00,000 bottles on the filler. Visual examination of cans include defects in weight, brim capacity and printing. The quality checks of deliveries depend on their acceptance or rejection by users.
15.4 Microbial control The microbial deteriorations can be divided into two main groups: • Deterioration of the product by general organisms to produce spoilage. • Deterioration of the product by pathogens to produce food poisoning. As soft drinks are nutrient-poor media, spoilage is mainly by yeasts and to some extent by low-acid tolerant bacteria and fungi. Yeast in general and Zygosaccharomyces baili in particular, are considered the key spoilage organisms [111]. Soft drinks can be non-carbonated, carbonated with or without fruit juice often with the addition of preservatives like acids. The fruit juices, nectars, concentrations etc. may be pasteurized or unpasteurized, aseptic or clean filled [111, 112]. The recent technology being employed,as cold pasteurization is ultra-high pressure which not only destroys the majority of pathogenic organisms, but enhance the shelf-life of the fresh product [113]. Some of the soft drinks too are acids like Orangeade and lemonade, so spoilage is only by high acid resistant species such as Dekkera anomala [112]. The prime requirement of yeast growth is sugar as carbon source, amino acids, and ammonium salts as nitrogen source, simple salts, trace minerals and vitamins. Some of the species of yeast are particular in their requirement of sugar, such as Zygosaccharomyces bailii and Z. rouxii cannot utilize sucrose as a carbon source [111]. In soft drinks, spoilage is generally due to facultative
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anaerobes because of low oxygen level and CO2 level either low or very high. The mould and bacterial growth is not very common as they are CO2 sensitive. Regarding packaging, PET containers are preferred which also serves as a source of spoilage. The cause is the permeability to oxygen [114], which leads to the growth of aerobic spoilage agents. Causal organisms of microbial spoilage are yeast, bacteria, moulds and mycotoxins. These need to be controlled.
Yeast Out of 800 species of yeast [115], currently ten are associated with the spoilage of foods [116], even under good hygienic conditions and using correct preservatives. Yeasts can be classified into four categories [117–119]. Group 1: Spoilage organisms well adapted to growth in soft drinks. These can cause spoilage at a low concentration such as one cell per container. These types of yeasts are osmotolerant, aggressive fermenting agents and preservative resistant e.g. Zygosaccharomyces baillii, Z. bisporus, Z. rouxii, Saccharomyces cerevisiae [116]. Group 2: These can cause spoilage if something goes wrong during manufacturing process such as absence of preservatives, ingress of O2, poor or no pasteurization. The common examples are Candida davenportii and Pichia anomala. Group 3: These are indicators of poor hygiene in relation to the factory state. Even present in higher number, they will not grow in soft drinks. The examples are candida solani, c. tropicalis and aneurobasidium pullulans. Group 4: These are called as aliens as they are not meant for the existing environment e.g. Kluveromyces lactis and K.marxianus.
Bacteria The bacteria associated with spoilage of soft drinks include Acetobacter, Alicyclobacillus, Bacillus, Clostridium, Gluconobacter, Lactobacillus, Leuconostoc, Saccharobacter, Zygomonas [120]. Gluconobacter is a strict aerobe and a common spoilage organism [111]. Another important spoilage organism in fruit juices is Alicyclobacillus. It produces two compounds such as antiseptic and smoky taints within juice. Antiseptic is due to 2,6-dibromophenol [121] and smoky taints is due to guaiacol (2-methoxyphenol) [122]. The factors, which favour the production of taints are heat shock; taint precursor, incubation temperature and oxygen. Another important thermotolerant spore forming aerobic organism is Alicyclobacillus acidoterrestris. The spoilage occurs from a very low inoculums i.e.1 spore per 10 ml [123, 124]. The
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effective control measures are the use of sorbate/benzoate, removal of oxygen, addition of ascorbic acid, rapid chilling of juice below 10°C [125], use of appropriate pasteurization method, use of chlorine or 4% peroxide [126].
Moulds The common symptoms of mould growth are tainting, discolouration. The causes are poor hygiene within the factory/field environment and within heat processed juices (heat-resistant moulds). Heat resistant moulds include Aspergillus ochraceus, A.tamarii, A.flavus, Thermoascus aurantiacum, Penicillium notatum and Clostridium species [111, 116, 127]. Most of them are found on fruits pre- and post-harvest and grow in the form of surface mats, producing spores. The extra cellular enzyme like pectinase is also produced by some of the moulds. Mycotoxins Mycotoxins are secondary metabolites produced by fungi found to be a serious threat to human and animal health [128]. The details of moulds and the mycotoxins produced in fruit materials and soft drinks products are presented in Table 15.3. In fruit juices, particularly apple juice, Ptaulin is most commonly found mycotoxin [116]. This mycotoxin can be reduced by the use of ascorbic acid or by fermentation [129]. Table 15.3 Soft drinks – moulds and mycotoxins
Moulds
Toxins
Fruit (s)
Penicillium expansum P. digitatum Aspergillus versicolor Fusarium oxysporum
Patulin, Citrinin, Roqufortine C Trptoquivalins Geosmin sterigmatocystin Oxysporone
Penicillium roqueforti
Isofumigaclavine A and B
P. glabrum
Citromycetin
Apple Citrus Fruit juices Treated orange juice Diluted fruit/ Water beverages Carbonated beverages
15.4.1 Quality assurance tests for microbial control Raw material The major step in quality assurance test is the selection of raw materials containing minimal number of bacteria, yeasts and moulds. To assure the quality of the raw materials, standards should be established, so that each lot of raw materials must meet the specification limits. Whenever there is any batch of raw materials stored for more than 3–6 months, re-testing should be done before its use.
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Water used in soft drinks industry should be tested daily or twice in a week. Sampling should be done at factory site as well as at the manufacturing plant. If the microbial count is found to be high, immediate control measures have to be followed. Sampling should be done at various points in manufacturing plant for microbial build-up. In-process testing is done and adequate actions are taken on the basis of tests results. The sample for testing the presence of microbes is done from bottles or cans. The appropriate control measures like proper cleaning of containers before and after their use have to be followed. The sampling is done from the finished product for microbial contamination and followed by control measures if required. Methods to test the presence of viable bacteria, yeasts and moulds: • • • • • • •
Direct plating and pour plate method Surface inoculation Membrane filtration Broth inoculation Roll tube method Most probable number method Microscopic examination of sediment after centrifugation.
In microbial testing the most important steps are preparation of samples, nutrient media and incubation conditions. Sample preparation is done for all the ingredients such as sugar, acids, flavours, colours, and fruit juices. Others are intermediate samples where they are taken in sterile container and tested directly. Finished product does not require sample preparation and are directly subjected to appropriate microbiological tests. After appropriate sampling swab should be supplied in suitable media and incubated at appropriate temperature to find specific type of micro organism. The two important methods commonly followed in soft drinks industry are – membrane filtration method and pour plate method [23].
Membrane filtration method The principle of working is passing the liquid through a thin membrane made up of cellulose nitrate. The advantages of the micro filter system include rapidity compared to culture methods; the low flow resistance of the filters (permitting rapid filtration); the transparency of the filter (permitting easy application of optical techniques); ability to detect very low counts of micro organisms; and the ability to detect living and dead micro organisms. The counts determined by the micro sieving were found to be higher than those with a conventional counting method. The diameter of the membrane pores is
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much smaller than the size of the micro organism’s cell, thus any cells in the sample are trapped on the membrane surface. Then membrane is removed and placed on an absorbent pad in a Petridish. Pad has a nutrient broth (specific for particular micro organism), as the membrane is trapped it helps the micro organism to get it stick to the pad. The Petridish is then covered and kept for incubation at a temperature favourable for the growth of the organisms. After the gap of incubation period, the micro organism’s cells become visible to our eyes as a colony. Depending upon the type of organism, colonies can be flat, domed, shiny or dull etc. Finally the number of colonies present on membrane reflects the number of individual micro organism’s cells originally present in the sample. The important aspect here is that with differently formulated media, we can selectively test the different groups and type of organisms. Moreover, for a particular micro organism to grow, the requirement of nutrient media, incubation period and temperature conditions all are found to be specific. Membrane filtration is advantageous to use as it can be used for large volume samples. Only problem with soft drinks is that they may cause clogging of the membrane pores, and reducing the size of the sample can solve this [23].
Pour plate method Pour plate method is the second efficient method of testing the microbial load. The first requirement of pour plate method is nutrient media in the form of nutrient agar. A measured volume of sample is placed into a petri dish and to this about 20 ml of nutrient agar is added. The covered Petri dish is kept as such to allow the nutrient agar to solidify and incubated as per the requirement for a prescribed period of time. After incubation period is over, the colonies are observed. The disadvantage of this method is that by using small volume, a true picture cannot be obtained. To overcome this problem, large samples like 30–50 ml should be taken. Another disadvantage is that the thick layer of agar leads to growth of anaerobic micro organisms. But above all these disadvantages, it is suitable to use for laboratory purposes as less laborious and less expensive also [23]. Thus, microbial tests are the important part of quality control, but the limitation here is the lack off microbiological standards in relation to raw materials and finished products. Although there are some in-house standards, but no official guidelines for microbiological standards in soft drinks industry are recommended.
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16 Packaging aspects
16.1 Introduction Packaging is considered to be a silent salesman as it draws the attention of consumer due to its appealing look. The function of packaging is to protect, to maintain and to promote the product. The types of packaging help to differentiate one product from another and every product need to be packed in some package throughout the supply chain. The unique packaging techniques also help for competition of the product in the market which is growing day by day. Packaging material must meet the processing and production line requirements and also the economic constraints to compete with the existing market trends. The important aspect regarding packaging is its specification, determined by the product and processing requirements, pack size, neck size, material and exposure to various hazards.
16.2 Packaging methods There are commonly two types of packaging: (i) aseptic packaging and (ii) non-aseptic packaging. The selection of a suitable packaging material is based on the following aspects – cold filling, in-pack pasteurising, hot filling, aseptic filling.
16.2.1 Cold filling Recent trend says that many soft drinks do not require any heat treatment to make them microbiologically stable. In this context, the packaging material should be such that, it bears the properties like gas and water barriers, flexibility / rigidity. The packaging demand in the market is such that it can withstand internal pressure and impact as well. The packaging material suitable to fulfil all these properties is PET bottle. Smooth shoulder contours and special footed design at the base, help them to withstand the pressure and impact if dropped. This makes the packaging material to withstand the required pressures and impact, if dropped [3].
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16.2.2 In pack pasteurisation Many soft drinks are not in the requirement of heat treatment but some are to make them microbiologically safe for which heat treatment is required. One such treatment is In-pack pasteurization (IPP). Generally followed for soft drinks as they cannot be hot filled, IPP cycle gives a better balance of internal/external pressure. The packaging materials suitable for these classes of beverages are certain plastic containers, heat shrink sleeves and metal cans. The bottles or packs once filled are taken through an IPP unit giving pasteurizing temperature in a short period of 20 minutes. After pasteurization, next important step is to hold up at a temperature of 70–75°C for next 20 minutes followed by immediate cooling. As high pressure build up is observed inside the package, the choice of the closure is also very critical. The closures preferred are metal roll-on. These closures are stable at a high temperature and can resist better internal pressures as well [3].
16.2.3 Hot filling Hot filling is done in the case of still products and other juices. Hot filling is done at 85°C and then sealed. This is to make the product microbiologically sterile, so the temperature should not be allowed to fall below 80°C during the first 3 minutes after filling. To prevent cooking and to retain desired flavour profile, it is either immersed in cold-water tank or dowsed in cold water. Care should be taken that package should be dry before distribution, if remains damp the secondary packaging that is corrugated board will soften and the will products collapse [3].
16.2.4 Aseptic packaging There are three work flows for aseptic packaging (Figures 16.1 and 16.2) such as the first system sterilizes the container, fills and seals it, and the second takes the sealed, pre-cleaned bottle, removes the seal fill and reseal in aseptic conditions. Final workflow is to blow a bottle, fill it and then seal it. All functions are performed within same machine so are known as form-fillseal (FFS) system. In aseptic packaging, foil can be sterilised easily by using H2O2 treatment. Heat resistant material can be steam sterilised, but steam sterilisation cannot be used for plastic materials. After treatment, H2O2 needs to be flushed out using hot air so the bottles used should be wide mouthed, as the sterilant has to be driven out. The specification for bottle and its shape has to be taken into account while selecting the package for aseptic packing. Various packaging materials, their characteristics and types of soft drinks used are presented in Table 16.1.
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Figure 16.1 Asceptic packaging machine
Figure 16.2 Asceptic packets Table 16.1 Packaging materials, characteristics and types of soft drinks [3]
Packaging Material
Characteristics
Impermeable to gas Glass Prevent oxygen ingress and CO2 loss (Carbonated drinks) Tolerant to elevated temperature Aseptic filling Flexible package Clarity Polyethylene terephthalate Unbreakability (Aseptically packed drinks) Consistent neck finish Recyclables Better re-seal ability and bottle strength Polyvinylchloride (PVC) Easy moulding (Juice product, Carbonated Rigidity products)
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Type of Closure Roll-on-pilfer-proof (ROPP) plastic closures
Plastic closures Vacuum seal closures
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High Density Polyethylene (Multi serve and single serve drinks, and juice drinks)
Longer shelf-life Prefer cold-filing
Polypropylene (Juice products and carbonated products)
Hot fill able (85°C) Retortable pouches Better oxygen permeability Remarkable clarity
Cans (Still drinks and carbonated drinks)
Cartons (Tetra pack/Tetra briks)
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Easy open ends with complex shapes, Good opening Pack integrity Attractive Less expensive Single serve Multi serve Storage and distribution without refrigeration Outstanding quality No added preservatives Reclosure facility
Aluminium / Steel open-ends
Plastic closures Plastic resealable cap
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17 Towards future
17.1 Introduction The recent trends in soft drinks includes functional drinks with various herbs for health purposes; carbonated beverages with variety of food additives such as vitamins and their precursors, alternate sweeteners and nutrients; fat regulating mixed fruit juices and soft drinks from horticultural waste. The demand of the future is beverages as a source of functional foods. The consumer demands for foods with added nutritional value such as fortification of food with vitamins and nutrients, to provide healthy benefits in more natural forms. The advantages of supplementation of beverages with antioxidant vitamins results in increased vitamin availability.
17.2 Healthy carbonated beverages The new formulations of carbonated drinks include use of carrot juice/βcarotene, aspartame and mint flavour. Each one of them serves a particular function. Carrot juice/β-carotene as precursor of vitamin A; Aspartame reduces the sugar content to make them as low-calorie beverages and mint flavour enhances the traditional flavours. The daily consumption of 1–2 cans of these type of healthy carbonated drinks along with Ca and vitamin supplements are highly nutritious which is more than 10 cans of simple carbonated drinks per day [130].
17.3 Functional drinks 17.3.1 Herbal drinks Functional drinks offer numerous benefits such as hydration, the maintenance of body fluid level and good health. Herbal drinks forms the part of functional drinks sector and gaining importance day by day [131]. Herbal infusion
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imparts their colour and flavour to the soft drinks, which is not very much desirable. Therefore, these are used in low amount and moreover their colour gets masked by colours such as orange, yellow and reds of most products. Another concept is the use of flower extracts in soft beverages. Some of the examples of the herbs being used in soft drinks along with their benefits are presented here: Artichoke (Cynara scoelymus):
• Reduces blood lipids, cholesterol and blood glucose level
• Maintains high insulin content valuable for diabetics
• Regenerates liver tissues [132, 133] Clover (Trifolium pratense):
• Relaxant
• Wound healing properties
• Expectorant
• Treatment of cough and chest problem [132–134] Damiana (Trunera diffusa):
• Nerve stimulant
• Mild irritant of genitor urinary tract
• As an aphrodisiac [132, 134] Ginseng (Panax ginseng):
• Raises body’s own defence mechanisms
• Reduces blood sugar level
• Formulations as herbal tonic [132–134]
• Kola (cola nitida):
• Nerve stimulant
• Stimulate digestive system
• Breakdown of fat
• Mild diuretic [132–134] Lemon balm (Melissa officinalis):
• Antibacterial and antiviral effects
• Calming sedative • Effective for stomach upsets in children [132–134]
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17.3.2 Fat regulating functional beverages The fruit of Garcinia indica contains characteristics acidic flavour. The acid present is hydroxy citric acid. The hydroxy citric acid helps in reduction of obesity and functions a as fat regulating agent. It also contains anthocyanin (cyaniding-3-glucoside and cyanidin-3-sambubioside), which can work as antioxidants [135].
17.4 Mixed fruit juice beverages Ber, pomegranate, strawberry, guava and citrus are the commercially grown horticultural crops. Ber juice is used to prepare ready-to-serve (RTS) beverage, squash and syrup [136]. As ber juice can’t be preserved so it is not meant for the preparation of RTS beverages [137]. Pomegranate can be utilized for preparation of RTS beverages [138], but its aroma is not very attractive, so needs to be blended with strong flavours. Thus, ber and pomegranate juices are blended with guava juice. RTS beverages prepared in proportions such as guava–pomegranate (30:70) and guava–ber (40:60) were found to be superior to any other combination of these horticultural crops (Figure 17.1).
Figure 17.1 Fruit beverages
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17.5 Carbonated beverages from jackfruit waste Jackfruit is used to prepare squash and nectar from blanched and blended pulp of bulbs with the addition of sugar and citric acid [139]. Nearly, fifty percent of fruit goes as waste so it can be utilized for the preparation of RTS beverage. Pectin enzyme is used to break pectin of pulp and for the extraction of juice. The RTS prepared contains 12% juice, 15°Brix (sugar) and 0.3% acidity (citric acid). The RTS can be used to prepare carbonated or non-carbonated RTS beverages with three different levels of carbonation such as 1, 2 and 3 volumes, at CO2 gas pressure of 0.775, 2.092 and 3.685 kg/cm2 respectively. The level of carbonation is monitored through a pressure gauge [140].
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[100] Hale, J., Stehle, G. and Bals, I. (1992). Gas analysis using a thermal conductivity method. Sensors and Actuators B., 7: pp. 665–671. [101] Yamada, T. (1997). Simultaneous determination of preservatives in beverages, vinegar, aqueous sauces and quasi drug drinks by Stir-Bar Sorptive Extraction (SBSE) and thermal desorption. Bunseki. 4: p. 296. [102] Helrich, K. (ed). (1990). Official Methods of the Association of Official Analytical Chemists, 15th edn. Association of Official Analytical Chemists (AOAC), Arlington, VA. Method Number. 976.22. [103] Moors, M., Teixeria C.R.R.R., Jimidar, M. and Massart, D. L. (1991). Determination of soft drink by gas chromatography with on-line pyrolytic methylation technique Anal. Chem. Acta, 225: p. 177. [104] Chen, B. H. and Fu, S. C. (1995). Separation and determination of phenolic antioxidants by HPLC with surfactant/n-propanal mobile phases. Chromatographia, 41: p. 43. [105] Fujimori, M., Kawamura, Y., Ito, Y. and Horitsu, H. (1994). Simultaneous determination of preservatives in beverages, vinegar, aqueous sauces and quasi drug drinks by Stir-Bar Sorptive Extraction (SBSE) and thermal desorption. Journal of Agricultural Chemist Society of Japan, 68: p. 967. [106] Ochiai, N., Yamagami, T. and Daishima, S. (1996). Determination of soft drink by gas chromatography with on-line pyrolytic methylation technique. Bunseki Kagaku, 45: p. 545. [107] Gonzalez, M., Gallego, M. and Valcarcel, M. (1998). Simultaneous determination of preservatives in beverages, vinegar, aqueous sauces and quasi drug drinks by Stir-Bar Sorptive Extraction (SBSE) and thermal desorption. J Chromatogr, 823: p. 321. [108] Mohamedilias, J. and Hamoir, T. P. (1993). Determination of benzoic acid in soft drink by gas chromatography with on-line pyrolytic methylation technique. J Chromatogr., 823: p. 321. [109] Baltussen, E., Sandra, P., David, F. and Cramers, C. (1999). Stir bar sorptive extraction (SBSE), a novel extraction technique for aqueous samples: Theory and principles J. Microcolumn Sep. 11, 737. [110] Norrish, R. S. (1967). Selected tables of Physical Properties of Sugar Solutions, BFMIRA Sci. Tech. Surv. No. 51. [111] Stratford, M., Hofman, P. D. and Cole, M. B. (2000). Fruit juices, fruit drinks, and soft drinks, In: The Microbial Safety and Quality of
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[125] Cerny, G., Duong, H. A, Hennlich, W. and Millers, S. (2000). Alicyclobacillus acid terrestris: influence of oxygen content on growth in fruit juices. Food Australia, 52: pp. 289–291. [126] Orr, R. V. and Beuchat, L. R. (2000). Efficacy of disinfection in killing spores of Alicyclobacillus acidoterrstris and performance of media for supporting colony development by survivors. Journal of food Protection, 63: pp. 1117–1122. [127] De Nijs, M., van der Vossen, J., Van Osenbruggen, T. and Hartog, B. (2000). The significant of heat resistant spoilage moulds and yeasts in fruit juices – a review. Fruit Processing, 10: pp. 255–259. [128] Nagler, M. J., Coker, R. D., Pineiro, M., Wareing, R.M. and Nicolaides, L. (2001). Manual on The Application of the HACCP System in mycotoxin Prevention and control, FAO Food and Nutrition Paper 73, FAOI / IAEA training and Reference Centre for Food and Pesticide Control, FAO, Rome, 113 pp. [129] Marth, E. H. (1992). Mycotoxins: production and control. Food Laboratory News, 8: pp. 34–51. [130] Fang-Chen (2005). Healthy carbonated beverages/soda. US 2005/0247739 Al; (US 2005/0247739 Al). [131] Zenith (2003). The 2003 Zenith Report on International Functional Soft Drinks, Zenith International Publishing Ltd, Bath, United Kingdom. [132] Brown, D. (2003). Royal Horticultural Society’s Encyclopedia of Herbs and Their Uses. London: CPL Scientific Publishing Services, Dorling Kindersley Publishers. [133] Gruenwald, J., Brendler, T., Jaenicke, C. and Smith, E. (2002). Plant – Based Ingredients for Functional Foods. Surrey, UK: Leatherhead Publishing. [134] British Herbal Medicine Association (1983). The British Herbal Pharmacopoeia 1983, pp. 80. Dorset: BHMA Publications. [135] Anthony, J. I. X. (1997). Garcinia Indica – A Natural Fat Regulating Functional Beverage. Beverage & Food World, May, 24. [136] Kadam, S. S., Chavan, U. D. and Dhotre, V. A. (1991). Processing of Ber. Preparation of Ready-to-Serve beverages, Beverage and Food World, 18: pp. 13–14. [137] Gupta, O. P. and Kadam, S. S. (1995). Ber. In: Handbook of Fruit Science and Technology. Salunke, D. K. and Kadam, S. S. (eds). New York: Marcel Dekker, pp. 387–395.
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[138] Adsule, R. N., Kotecha, P. M. and Kadam, S. S. (1992). Preparation of wine from pomegranate. Beverage and Food World, 19: pp. 13– 14. [139] Anonymous (1953). Preparation of jackfruit nectar. Bull. CFTRI, 3: pp. 93–94. [140] Ranganna, S. (1986). Handbook of Analysis and Quality Controls of Fruit and Vegetable Products, 2nd Ed., 9–10, 903–907, New Delhi: Tata McGraw Hill Publishing.
References Part III.indd 255
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Index
Adulterants 85 Amino acids 106 Anticarcinogenic 28 Antidiabetes 29 Antimicrobial 30 Antioxidant 27 Arabica 06 Artificial flavourings 205 Baba budan 03 Banana flower tea 126 Berries 03, 08 Beverage 31 Black tea 66, 77, 95 Blending soft drink 216 Blossoming 08 Blue tea 91 BOP fannings 121 Botany coffee 06 Caffeine coffee, tea 16, 105 Camellia sinensis 65 Canned tea 143 Cappuccino 45 Carbohydrates coffee, tea 19, 105 Carbonation 217 Catechins 104, 150, 151 Chromosome 65 CIP 221 Clarification 212, 213 Clouding agents 207 Coffea arabica 07
Coffea canephora 07 Colas 184 Composition tea 101 Concentration soft drink 214 Cordial 186 CTC 67, 97 Cultivation 03 Cutting 08 Darjeeling tea 66 Deaeration 219 Decaffeinated coffee coffee 43 tea 120, 135 Diet soft drinks 187 Dioxin 114 Endocarp 8 Endosperm 8 Energy drink 184 refreshment 185 sports 185 functional 185 Fizzy drink 183 Flavoured tea 131 Fortified drinks 181 Fortified tea 136 Frozen juice 183 Functional drinks 181, 187 GABA 125 Gabaron 125 Gingeng 127 Grafting 08
257
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Green brick tea 89 Green tea 66, 77
colours 202 flavourings 205 Natural juice 183 Nature identical flavourings 206 Nutraceuticals 188
Harvesting tea equipment 84 plucking 84 Health benefits 27 Herbal drinks 187 Herbal teas 123 Hoeing tea 82 Iced tea 121 Infusion tea 116 Ingredients soft drinks 189 water 189 sweetener 190 acidulants 200 colours 202 flavours 204 Instant coffee 44 Instant tea 117 Kamairi cha 89 Keemun 77 Kombucha 140 Lao -cha 89, 90 Layering 08 Lipids coffee 21, 105 tea 106 Melanoidins 20 Minerals 20 Moisture 13, 16 Monsoon coffee 46 Mucilage coffee 08 National drink England 70 Russia 72 Natural sweetener 191
Index.indd 258
Oolong tea 66, 67, 77, 93 Organic acids 13, 14, 18 Parchment 08 Pasteurisation 216 Peaberry 08 Pests diseases tea 83 Pharmacological tea 107 Poly phenol 102, 103, 149 Processing coffee 08 Production scenario 04 Production tea 78, 79 Propagation 08 tea 82 Proteins 13, 18 Pruning 84 Pulping 211 Pyramid tea bag 115 Quahweh 03 Relative sweetness 191 Reverse osmosis 214 Roasting coffee 11 bound moisture 11 breaking strength 12 colour of beans 12, 13 cup quality 11 equipment 11 flavour 11 roasters 12 specific gravity 13 swelling of beans 12
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Index Robusta 07 Rubiaceae 06, 07 Saponins 159 Sen-cha process 87, 88 Smoothies 182, 187 Soft drink 177 ready to drink 177 dilutable 179 nectar 179 major players 180 Indian scenario 180 Soluble coffee 44 Squash 186 Sub tropical 04 Synthetic sweetener 190, 192 colours 203 Syrup 215 Tasting 24 Tea by-products 147
Index.indd 259
ceremony 68 cider 139 concentrate 129 dyes 155 fanning 114 granules 145 heretics 68 quality 99 seed oil 158 surrogates 125 Thea sinensis 78 Theaceae 80 Tonic tea 139 Toyoma kurocha 143 triacontanol 157 Trigonelline 18 Tropical 04 Value added tea 113 Value addition 31 Vitamins tea 105 Volatile compounds 13, 14, 21 Yellow tea 91
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Recent Trends in Soft Beverages
L. Jagan Mohan Rao and K. Ramalakshmi
WOODHEAD PUBLISHING INDIA PVT LTD New Delhi ● Cambridge ● Oxford ● Philadelphia
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Published by Woodhead Publishing India Pvt. Ltd. Woodhead Publishing India Pvt. Ltd., G-2, Vardaan House, 7/28, Ansari Road Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com Woodhead Publishing Limited, 80 High Street Sawston Cambridge CB22 3HJ UK www.woodheadpublishing.com Woodhead Publishing USA 1518 Walnut Street, Suite 1100 Philadelphia PA 19102-3406 USA First published 2011, Woodhead Publishing India Pvt. Ltd. © Woodhead Publishing India Pvt. Ltd., 2011 This book contains information obtained from authentic and highly regardedsources. Reprinted material is quoted with permission. Reasonable efforts havebeen made to publish reliable data and information, but the authors and thepublishers cannot assume responsibility for the validity of all materials. Neitherthe authors nor the publishers, nor anyone else associated with this publication,shall be liable for any loss, damage or liability directly or indirectly caused oralleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in anyform or by any means, electronic or mechanical, including photocopying,microfilming and recording, or by any information storage or retrieval system,without permission in writing from Woodhead Publishing India Pvt. Ltd. The consent of Woodhead Publishing India Pvt. Ltd. does not extend tocopying for general distribution, for promotion, for creating new works, or forresale. Specific permission must be obtained in writing from WoodheadPublishing India Pvt. Ltd. for such copying. Trademark notice: Product or corporate names may be trademarks or registeredtrademarks, and are used only for identification and explanation, without intentto infringe. Woodhead Publishing India Pvt. Ltd. ISBN 13: 978-93-803081-2-8 Woodhead Publishing India Pvt. Ltd. EAN: 9789380308128 Woodhead Publishing Ltd. ISBN 13: 978-0-85709-009-6 Typeset by 3rdEyeQ, New Delhi Printed and bound by Sanat Printers, New Delhi
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This book is dedicated to our mentors, who constantly encouraged us in our life.
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Contents
Preface
xiii
Foreword
xv
1
Part I Introduction to coffee
1 3
1.1
Origin and history of coffee
3
1.2
Coffee production scenario
3
1.3
Botany, agricultural practices and propagation
6
1.4
Processing
8
1.5
Chemical composition
16
1.6
Additives in coffee
23
1.7
Tasting of coffee
24
2
Health benefits
2.1
Introduction
27
2.2
Antioxidant activity
27
2.3
Anticarcinogenic activity
28
2.4
Central Nervous System (CNS)
28
2.5
Reproductive system
29
2.6
Bone system
29
2.7
Cardiovascular system
29
2.8
Antidiabetes effect for type-2 diabetes
29
2.9
Antimicrobial effect
30
3
Recent trends in value addition
3.1
Introduction
31
3.2
Coffee beverage
31
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27
31
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viii
Contents
3.3
Canned coffee beverages
37
3.4
Ready-mix coffee beverage
37
3.6
Coffee jelly beverage
38
3.7
Fortified coffee beverages
38
3.8
Fortified coffee drink
39
3.9
Honeyed coffee
39
3.10
Coffee tablet
39
3.11
Freeze-dried coffee tablets
39
3.12
Flavoured coffee
40
3.13
Coffee wine
41
3.14
Candy from coffee beans
41
3.15
Torrefacto coffee
41
3.16
Germinated coffee
41
3.17
Coffee filled packet
42
3.18
Cookie formulation with coffee
42
3.19
Coating of frozen pizza with coffee colorant
42
3.20
Carbonated coffee
42
3.21
Decaffeinated coffee
43
3.22
Soluble coffee
44
3.23
Instant hot cappuccino
45
3.24
Monsoon coffee
46
3.25
Coffee paste
47
4
Value-added by-products
4.1
Introduction
49
4.2
Source of dietary fibre
50
4.3
Coffee spirit
50
4.4
Charcoal production
51
4.5
Mushroom cultivation
51
4.6
Production of citric acid and gibberellic acid
52
4.7
Antioxidant compounds
52
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Contents
ix
4.8
Source of natural food colour
52
4.9
Production of aroma compounds
52
4.10
Biogas production
53
4.11
Source of phenolic compounds
53
4.12
Summary and conclusion
53
References
55
5
Part II Introduction to tea
5.1
Introduction
65
5.2
Origin and history
65
5.3
Tea production
78
5.4
Botanical and taxonomical characteristics
80
5.5
Cultivation practices
81
6
Types of tea and processing
6.1
Introduction
87
6.2
Green tea
87
6.3
Green brick tea
89
6.4
Yellow tea
91
6.5
White tea
92
6.6
Oolong tea
93
6.7
Black tea
95
6.8
Comparison of tea quality
99
7 Chemical composition and pharmalogical, medical properties of tea
63 65
87
101
7.1
Introduction
101
7.2
Diversity of therapeutic compounds in tea
102
7.3
Pharmacological aspects associated with tea consumption
107
8
High impact value-added products of tea
8.1
Introduction
113
8.2
Tea bags
113
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x
Contents
8.3
Instant tea
117
8.4
Iced tea
121
8.5
Herbal teas
123
8.6
Tea concentrate
129
8.7
Packet tea
129
8.8
Carbonated bottled tea
130
8.9
Flavoured tea
131
8.10
Decaffeinated tea
135
8.11
Fortified tea
136
8.12
Tonic tea
139
8.13
Tea cider
139
8.14
Tea kombucha
140
8.15
Toyoma kurocha
143
8.16
Canned tea
143
8.17
Instant tea granules
145
9
Tea by-products
9.1
Introduction
147
9.2
Caffeine
147
9.3
Polyphenols
149
9.4
Tea dyes
155
9.5
Triacontanol
157
9.6
Tea seed oil
158
9.7
Saponins
159
9.8
Tea waste as extenders in polymers
159
9.9
Summary and conclusion
160
References
163
10
Part III Introduction to soft drinks
10.1
Soft drink
177
10.2
Need of soft drinks
177
10.3
Benefits of soft drinks
177
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147
175 177
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Contents
xi
11
Beverage consumption
11.1
Introduction
179
11.2
World market
180
11.3
Major players of soft drinks in the world
180
11.4
Indian scenario
180
11.5
Market trends of functional drinks
181
11.6
Expansion of soft drinks market
182
12
Soft drink classification
12.1
Introduction
183
12.2
Ready-to-drink
183
12.3
Concentrated soft drinks
186
12.4
Other categories
187
13
Ingredients of soft drinks
13.1
Introduction
189
13.2
Water
189
13.3
Sweeteners
190
13.4
Acidulants
200
13.5
Colours
202
13.6
Flavours
204
13.7
Clouding agents
207
14
Processing technology
14.1
Introduction
211
14.2
Handling Raw Material
211
14.3
Pulping and Extraction
211
14.4
Clarification
212
14.5
Concentration
214
14.6
Syrup Preparation
215
14.7
Blending
215
14.8
Pasteurisation
216
14.9
Carbonation
217
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179
183
189
211
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xii
Contents
14.10
De-aeration
219
14.11
Filling
219
14.12
Packaging
220
14.13
Clean-In-Place (CIP) System
221
15
Quality control
15.1
Introduction
223
15.2
System quality control
223
5.2.3
Sugar
225
15.3
Product quality control
228
15.4
Microbial control
231
16
Packaging aspects
16.1
Introduction
237
16.2
Packaging methods
237
17
Towards future
17.1
Introduction
241
17.2
Healthy carbonated beverages
241
17.3
Functional drinks
241
17.4
Mixed fruit juice beverages
243
17.5
Carbonated beverages from jackfruit waste
244
223
237
241
References
245
Index
257
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Preface
The aim of the book is to provide an overview of chemistry, technology, quality control with respect to raw material as well as finished product, value-added product development and marketing strategies of the most widely consumed natural beverages such as coffee, tea and other carbonated soft drinks. First section entitled Recent trends in coffee deals with coffee, which is the most fascinating beverage throughout the world. Coffee, an aromatic, non-alcoholic brew is loved by the consumers’ world over, for its stimulating and refreshing taste. Coffee is one of the international products and is the second largest traded in the world next to crude oil. In this chapter, a brief historical perspective of beverage, botany, and processing of green to roasted coffee are analysed. Effect of roasting on chemical composition, physical and chemical changes during roasting and their significance in nutritional quality and physiological impact in the cup quality is also discussed in detail. Further, health benefits and recent value-added coffee products, utilization of by-products are highlighted. In value addition section, details about the variety of speciality coffee beverages, canned coffee, ready mix coffee, coffee jelly, fortified coffees, honeyed coffee, coffee tablets, variety of flavoured coffee, coffee wine, coffee candy, germinated coffee, coffee cookies, pizza with coffee colourant, carbonated coffee, decaffeinated coffee, instant coffee, monsoon coffee and coffee paste are discussed. In by-products section information regarding dietary fibre, coffee spirit, mushroom cultivation, production of charcoal, citric acid, gibberellic acid, antioxidant as well as phenolic compounds, natural food colour, aroma compounds and bio gas is provided. Second section entitled Recent trends in tea describes tea, which is the second most widely consumed beverage in the world next to water. Considerable interest has developed in the past decade in unravelling the beneficial health effects of tea, in particular, polyphenolic components and its antioxidant activity. There are three major categories of tea: the non-fermented green tea, the partially fermented Oolong and the fully fermented black tea. The origin and history, various types of tea, chemical composition and medicinal and pharmacological properties of tea are discussed. In high impact value-added products section, relevant fine points about tea bags, instant tea, iced tea, herbal tea, tea concentrate, carbonated tea, various flavoured teas, decaffeinated tea,
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xiv
Preface
different fortified teas, tonic tea, tea cider and vinegar, tea kombucha, toyama kurocha, canned tea and instant tea granules are described. In tea by-products section, particulars about caffeine, polyphenols, dyes, triacontanol, tea seed oil and tea saponins are presented. Third section entitled Recent trends in soft beverages is written to describe all about soft drinks. The term ‘soft drinks’ includes all type of non-alcoholic liquid and powder beverages, although it is generally used to signify carbonated beverages. The beverage industry is the fastest growing sector in the global business. Carbonates are the biggest soft drinks sector with 45% of global volume. Consumers purchase soft drinks primarily to quench thirst. Advances in technology have improved all aspects of the soft drink industry. Quality control of the beverage starts with raw materials and ends only when the product reaches the consumer. Computerized manufacturing technologies have contributed to higher efficiency and quality in bottling operations. Another important aspect of quality control in soft drinks is the test for storage life. Therefore, it is essential to maintain the quality system in each and every step including microbiological aspects. Also there are varieties of novel soft drinks with different flavours available in worldwide. This chapter describes all the above aspects, which include classification, ingredients (viz., water, sweeteners, acidulants, colours, flavours and clouding agents), processing technology, packaging and quality control. Future trends section includes healthy carbonated drinks, functional drinks, mixed fruit juice beverages and carbonated beverages from waste of fruits. We thank all the contributing authors for their cooperation in preparing this book, which we hope will serve as an excellent reference for those researchers and students interested in the beverages such as coffee, tea and carbonated beverages. Dr L. Jagan Mohan Rao K. Ramalakshmi
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Foreword
The world of beverages is fast expanding due to increasing number of consumers. Beverages include fruit juice, squash, soda water, artificially sweetened carbonated water, tea, coffee, milk and milk shakes. A hot beverage is normally served heated. This may be through the addition of a heated liquid, such as water or milk, or by directly heating the beverage itself. Tea, coffee hot milk and chocolate generally belong to this category. Commonly soft drink refers to any cold drink that does not contain alcohol. Soft drinks are found in two forms such as ready-to-drink and in concentrated form, which need to be diluted to make ready-to-drink beverage. Beverages are produced and marketed in almost every country in the world. Consumers consider beverages not simply as thirst quenchers low or no calorie products to manage their weight but instead prefer nutrient dense, no calorie beverages. It is these preferences that pose new challenges in the development of beverages and utilization of drinks as functional foods. There are many books on beverages including tea, coffee and soft drinks. This book “Recent trends in soft beverages” is a step forward in imparting updated information on constituents, their chemical structures, chemical reactions and interactions, nutritional, health and medicinal aspects of beverages, The book “Recent trends in soft beverages” has three parts. Part I on Coffee, Part II on Tea and Part III on Soft beverages generally deal with several varieties of products and formulations, chemical constituents, nutrients and anti-nutrients, manufacturing practices, quality control and future trends. The book covers a wide range of topics highlighting both positive and negative aspects of coffee, tea and several soft drink formulations. Potential of health and medicinal effects of tea, coffee, etc is extensively reviewed. The strength of book is that most sections contain several chapters that provide complimentary views on each topic. List of several references will be a big treatise. Authors have a very rich experience in research and development of varieties of beverages and they have attempted to cover a wide range of their collected experience to make this volume. I wish to thank all the
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xvi
Foreword
editors and contributors for their effort in bringing out this important publication. Thanks to a welcome invitation from the editors to write this foreword. Reading this book is a rewarding experience. Body of information is of real value as it reaches wider audience – academicians, food scientists, health professionals, teachers and students. Dr N S Mahendrakar, Editor-in-Chief, Journal of Food Science and Technology, AFST (I), Mysore and Springer, India Scientist G (Retired), Central Food Technological Research Institute, Mysore. 23 Feb 2011.
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