Synonym: Camellia thea.
Biological source: Tea contains prepared leaves and leaf buds of Thea sinensis Linn.
Geographical source: Tea is cultivated in India, Srilanka, Indonesia, China and Japan. In India it is cultivated in North-Eastern India (mainly in Assam and Bengal), South India (in Nilgiri, Palni, Annamalai hills in Tamilnadu, Kerala and Karnataka states) and North West India (in Dehradun, Almora and Garhwal district of Uttaranchal, Kangra valley and Mandi district of Himanchal Pradesh).
Cultivation and Collection:
The tea is available in two forms:
1. Black tea
2. Green tea
Black tea is available from India and Srilanka whereas green tea is available from China and Japan. Black tea is obtained by fermentation of fresh tea leaves which further dried artificially.
Green tea is obtained by keeping tea leaves in copper vessel and then dried artificially.
Tea is a dried leaf of bush which contains theine which gives cheap and stimulation drink upon addition of boiling water with sugar and milk. So tea is most important beverage crop of India. The basic requirement for the cultivation of tea leaves are deep, light, well drained acidic soil (pH 5.8 to 5.4 or less), humid climate with annual rainfall (100 cm), altitude (2100 meter above sea level), temperature is in the range of 21°C to 29°C is ideal for its cultivation. Tea is shade loving plant and it develops more vigorously when planted along with shady trees.
The propagation is mainly done by seeds which are sown in germination beds and developed saplings are transplanted into the open fields. The garden or field is regularly hoed and weeded for the better quality of crop. Pruning is done time to time for maintaining the proper shape of tea bush. The yield can be increase by the use of nitrogenous fertilizers like ammonium sulphate. Tea does not favor water logging because roots of tea plant gets leached and deteriorated. Hence it is grown in hilly areas where water drains out easily.
The tea leaves along with bud are plucked by the skilled labour preferably female labourers and dried by artificial method. Tea needs to be stored in heat, light, air and moisture proof packing to remain fresh and mold free.
Preparation of Green Tea:
The freshly collected tea leaves are exposed to air until most of the moisture gets removed. Then it is roasted and stirred continuously so that the leaves become moist and flaccid. These are passed through rolling table to make rolling balls which should be moisture free. The leaves are shaken and roasted in copper vessel. The leaves turned dull green in colour. The leaves are winnowed, screened and graded into different varieties.
The cultivated tea is small evergreen shrub which is 1 to 1.5 meter in height. The wild plants are up to 6 meter in height. The leaves are dark green in colour, lanceolate, elliptical, blunted at apex, serrate, hairy and glabrous in nature. Flowers are solitary in nature and generally in group of 2 to 3 leaf axils. It possesses characteristic odour and bitter taste.
Tea leaves contain caffeine (1 to 3 percent), theobromine and theophylline (in trace amount), gallotannic acid (15 percent) and an enzyme mixture known as thease. The colour of tea leaves is due to the presence of gallotannic acid.
Caffeine is a white powder which is odourless and bitter in taste. It is weakly basic in nature. It has feeble solubility in water, alcohol, chloroform and ether.
Caffeine is an example of purine group of alkaloids which gives positive Murexide test.
1. Murexide test: Take caffeine in a petridish and add hydrochloric acid with potassium chlorate. Heat it upto dryness. Then this obtained residue is exposed to ammonia vapours, a purple colour develops which disappears upon the addition of alkali solution.
2. When caffeine is treated with tannic acid solution it produces white precipitate.
Tea is used as central nervous system stimulant and as diuretic. Caffeine possess cerebral vasoconstrictor action hence it uses as CNS stimulant. Caffeine also uses in migraine (given along with ergotamine tartarate).