TEA Camellia sinensis
Camellia is an evergreen shrub or tree, which grows wild from India to China. There are about 45 species of Camellia of which Camellia sinensis, considered native to India. Tea is obtained from plants propagated by seed sown in a nursery; cuttings can also be rooted. Trees for plucking are regularly pruned to obtain a bush shape, which encourages maximum leaf production. C. sinensis there are two types: `China' and `Indian'. China type is a slow-growing smaller tree with narrow leaves. India type is fast growing with large drooping leaves. The yield from Indian types is higher than that of the China type. The important tea growing countries are India, China, Sri Lanka, Japan and Kenya.
Tea leaves are usually plucked by hand Tea leaves are usually plucked by hand. The average interval between pluckings is about a week. In India, about 5-6 pluckings are made in a season. Usually, the terminal bud and two terminal leaves from the end of each shoot are plucked. In some cases, the bud and three leaves are taken giving a higher yield and a poorer quality product. Some of the best teas come from high-altitude areas, such as Darjeeling, while teas from the plains are often of `common' quality. The yield at high elevation is poor compared to that at lower elevation for the same kind of plant.
Processing : Commercial tea is available mainly in three forms 1 Processing : Commercial tea is available mainly in three forms 1. Black tea 2. Green tea 3. Oolong tea The three forms of tea differ only in the method of processing the leaves. Black tea is by far the most popular among the three.
Black Tea Withering Rolling Fermentation Drying Grading Packing The various processing steps in the manufacture of black tea are Withering Rolling Fermentation Drying Grading Packing
Withering Withering is carried out by spreading tea leaves thinly on racks or shelves, to dry the leaves partially. Generally withering is allowed till the water-content in the leaf is lowered by about 40 per cent. Rolling The withered leaves are then rolled to break open the cells and release the juices and enzymes. Various rolling techniques are employed and the flavour characteristics inherent in various teas partially depend on the technique used.
Fermentation After rolling, the leaves are shifted and spread out thinly on suitable platforms and allowed to ferment for 2-6 hours at temperatures between 21° to 27°C. During this process, the enzymes bring about the oxidation of the various polyphenols present in the juices, resulting in the change of colour from green to reddish copper. Two of the important polyphenols that undergo oxidative changes are catechin and gallocatechin.
Drying/Firing When the fermentation has proceeded to the desired degree, further change is arrested by drying or firing. This comprises the passing of the fermented leaves through a chamber in which hot air is circulating,; At the entrance of the chamber, the temperature is 93°C which drops to about 49°C near the exit. The time required for this process is about 30-40 minutes and the dried product contains 3-4 per cent moisture. Besides halting the fermentation process, firing causes some caramelization to occur resulting in the characteristic colour of black tea leaves. . 930C 490C Tea (3-4 % moisture) Entrance Exit 30-40 min
The aroma of tea is believed to develop during the fermentation and firing processes. Although a large number of volatile compounds have been identified from tea leaves, none has -been found to make any significant contribution to the tea aroma.
Grading The dried product is cleaned and sorted into various grades of tea of commerce. The quality of black tea is related to the polyphenol and enzyme content of the leaves used in processing. They are maximum in the buds and the first and the second leaves (28, 28 and 27 per cent respectively) and teas obtained from these are the most desirable. On this basis, tea is categorized as "leaf' grade and 'broken' grade.
Both leaf grade and broken grade are further categorized as The broken grade comprises the smaller : sizes sifted from bulk or those obtained by cutting the longer leaf grades to desirable sizes. Both leaf grade and broken grade are further categorized as Orange pekoe Pekoe Souchang Orange pekoe and pekoe refer to the size of the leaf only. Orange pekoe has the largest leaves, followed by pekoe and souchang in decreasing order. Orange pekoe is perhaps the best quality. Other things being equal, the broken grades usually give a stronger tea than leaf grade. Besides the above grade, there are the waste products Fannings and Dustings.
Blending & Packaging Tea is generally blended before it reaches the consumer. In India, the blended tea is packed in plywood boxes lined with aluminium foil and parchment paper. During packing, tea absorbs moisture. If the moisture content increases to 6-7 per cent, tea is to be subjected to a second firing before packing. India is also exporting tea in consumer tea packs instead of bulk tea chests.
Green Tea Green tea is made in the same manner as black tea, but the withering and fermentation steps are omitted. The leaves are heat treated, rolled and dried. The heat treatment consists of pan-firing or steaming to inactivate the enzymes. The aroma, flavour and colour of green tea are significantly different from those of black tea. Green tea is a light, yellowgreen beverage when brewed correctly. The Japanese mainly produce and consume green tea.
Oolong Tea Oolong tea is an intermediate between black and green tea in colour and taste characteristics. Its production method is similar to that employed for green tea, except that the leaf is slightly withered and light fermentation allowed before the leaf is dried.
Composition of Tea The important constituents of tea contributing to the flavour of tea beverage are Caffeine Polyphenols Essetial oils Analysis of fresh leaves of Indian tea gives the following values: Polyphenols, 22.2; protein, 17.2; caffeine, 4.3; crude fibre, 27.0; starch, 0.5 and ash, 5.6 per cent. Fresh tea leaf also contains carotenes, B -vitamins and ascorbic acid. During the manufacturing of black tea, ascorbic acid is lost.
The maximum amount of caffeine is present in the bud and the first two leaves. Small quantities of compounds related to caffeine, viz., theophylline, theobromine, xanthine and hypoxanthine are also present. The important polyphenols present in tea leaves are catechins and gallocatechins. These undergo changes during fermentation in black tea manufacture. Enzymes involved in fermentation are polyphenol oxidases. No change takes place in green tea as its manufacture does not involve fermentation. During fermentation, polyphenols undergo oxidation and the oxidized products polymerize and part of them combine with caffeine. The caffeine-polyphenol complexes are soluble only in hot water and this accounts for the 'creaming' observed when hot tea infusions are cooled.
Tea leaves contain a volatile oil consisting of alcohols, aldehydes, phenols and some fatty acids. On steam distillation, black tea gives an essential oil. The characteristic aroma and flavour of tea is due to the essential oil. Tea, like coffee, has no nutritive value. The proteins present in tea leaves are rendered insoluble in the processing. Tea infusion contains negligible quantities of carbohydrates and fat. Whatever nutritive value tea has comes from added milk and sugar. Tea as a beverage is consumed mainly for its stimulating value.