Tea is generally divided in three groups that is, black, green and white or oolong tea. All type of tea are produced from same tea plant which is Camellia sinensis. The leaves of this plant contains polyphenol compounds. The technique used for processing gives different type of tea.
For producing black tea, tea plant leaves are treated at twenty-eight degree Celsius for eighteen hours. This reduces water content to half. These leaves are then rolled vigorously by machine and then fermented at twenty-five degree Celsius for three hours. The fully fermented leaves are pan-fried and then dried to get black tea. This processing results in destruction of polyphenols of leaves.
This tea has strong flavour and black colour. This is also called fermented tea. It is the most famous and constitute 80 percent of all tea produced and drunk.
Green tea is light in colour. This is unfermented tea and rich in antioxidants. For the production of green tea, plant leaves are steamed immediately after the harvest to stop the enzyme reactions and auto-oxidation. Steaming inactivates enzyme polyphenol oxidase. This is done to preserve natural anti-oxidants of the leaves. The leaves are then rolled by hand to break the cells of the leaves.
Oolong tea is also known as 'Half-fermented' tea. This tea is partially oxidised tea and slightly stronger in taste then green tea but delicate to black tea.
For the production of oolong tea, the leaves are kept under certain conditions to produce specific flavours by fermentation. This causes polymerization of polyphenols. These leaves are not rolled and the leaf cells are not broken.