Introduction
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, is the important one from which tea of commerce is made. Commercial 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. Amongst cultivated C. sinensis there are two types:"China" and "Indian". The former type is a slow-growing smaller tree with narrow leaves, while the latter is fast growing with large drooping leaves. The yield from the Indian type 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. 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.
Production :
In India, the two main tea-growing regions are the hilly districts of Assam and West Bengal, and the
Western Ghats of Kerala, Tamil Nadu and Karnataka. India tops the list in production and export of tea, in the world. In 2005, the world production of tea was 2.7 million tonnes of which India's share was 1.02 million tonnes. Of the total world export of about 1.61 million tonnes during that year, India exported 2,05,000 tonnes valued at Rs. 1,924 crore. The tea exported from India is mostly black tea and the export of green tea is small. However, large quantities of tea waste and fluff (pieces of leaves, leaf hair, fibre, etc.) are exported and used for the manufacture of caffeine. India has also been exporting consumer tea packets instead of bulk tea chests and instant tea.
Processing :
Commercial tea is available mainly in three forms—black tea, green tea and 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.
1. Black tea:
The various processing steps in the manufacture of black tea are withering, rolling,
fermentation, drying, grading and packing. 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. 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. 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 catech in and Gallocatech in.
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 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.
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.
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. 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 and 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 the leaf grade.Besides the above grade, there are the waste products— farmings and dustings.
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.
2. 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, yellow-green beverage when brewed correctly. The Japanese mainly produce and consume green tea.
3. 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.
4. White tea:
White tea is made from young leaves that have not undergone oxidation. The buds may be shielded from sunlight to prevent formation of chlorophyll. White tea is produced in lesser quantities than most of the other types.
4. Yellow tea:
Either used as a name of high quality tea served at the Imperial Court of Japan or of special tea processed similarly to green tea but with a slower drying phase.
5. Kukicha:
Also called winter tea, Kukicha is made from twigs and old leaves pruned from the tea plant during its dormant season and dry roasted over a fire. It is popular as a health food in Japan and in macrobiotic diets.
Composition of Tea :
The important constituents of tea contributing to the flavour of tea beverage are caffeine, polyphenols and essential 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 manufacture 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 oxidase.
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.
Different types of Tea-
• Instant Tea :
Instant tea (soluble tea) products have become popular in recent times. These products are hot and cold water solubles, iced tea concentrates, carbonated tea, etc. In the preparation of hot water soluble instant tea, the fermented tea leaves are extracted with hot water, centrifiiged and dried in a drum drier or freeze drier. For the manufacture of cold water soluble tea, the aqueous extract is cooled to 5°C, the separated caffeine-polyphenol compound is removed by centrifiigation and then dried. Iced tea concentrate is cold water soluble and contains sugar, citric acid and essences. Ready tea is instant tea with sugar and milk powder. India produces all these varieties of instant tea and sizeable quantities are exported. The export in 1980-81 was 10.76 million kg.
Instant tea is largely used in making iced tea because of its solubility in cold water. However,
the flavour and aroma of instant tea is less full than that of the beverage freshly prepared from tea
leaves.
• Herbal tea :
It is a herbal infusion not made from leaves of the tea bush but from fresh or dried flowers, leaves,
seeds or roots generally by pouring boiling water over the plant parts and letting them steep for a few minutes.
•Tea bags :
Tea bags were invented way back in 1908. Tea leaves are packed into small (usually paper) tea bags. It is easy and convenient, making tea bags popular for many people nowadays.
•Tea sticks :
One of the modern forms of tea consumption, an alternative to the common tea bags, is tea sticks.
•Blended and unblended varieties :
Various blended and unblended teas which have achieved fame for their characteristic flavours
include Assam, Darjeeling and Keemun, also known as English breakfast tea. Popular blended teas
include Irish breakfast, Russian style and Earl grey.
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