Tea Tree Uses and Chemical Constituents
Tea contains the prepared leaves and leaf buds of Thea sinensis belonging to the family Theaceae (Ternstroemiaceae). It is also known as camesia thea.
Tea is cultivated in India, Sri Lanka, China, Indonesia and Japan. Black tea is available from India and Sri Lanka where as Green tea is available from China and Japan. Black tea is obtained by fermenting the heap of fresh tea leaves and drying further with artificial heat. Green tea is obtained by putting tea leaves in copper pans and then drying with artificial heat. Tea tree is a small evergreen shrub and is much branched and has grey bark. It grows to a height of 1 to 1.5 metres. They are bitter in taste.
Preparation of Green Tea :
Green tea is prepared by exposing the freshly collected tea leaves to the air so as to remove the moisture from them. After the moisture is removed, they are roasted and stirred continuously for the leaves to become moist and flaccid. After that they are placed on rolling tables and rolled into balls. Then they are subjected to pressure which removes the moisture. The leaves are then shaken on the copper pans and are roasted again until the leaves become dull green in colour. Then the leaves are winnowed, screened and graded into many varieties.
Chemical constituents :
Tea leaves are the rich source of caffeine and is extracted from tea dust, tea leaf waste and sweepings. Theobromine and theophylline are also present in minor amounts. Gallotannic acid is responsible for the colour of the tea leaves. Odour is due to the presence of a yellow volatile oil. The leaves also contain an enzymatic mixture called as thease.
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