Tea is a beverage

by: reddy
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Tea is a natural source of the amino acid theanine, methylxanthines such as caffeine and theobromine, and polyphenolic antioxidant catechins. It has almost no carbohydrates, fat, or protein. It has a cooling, slightly bitter, and astringent flavor.

The word tea came into the English language from the Chinese word for tea, which is pronounced tee in the Min Nan spoken variant.

Processing and classification:

These types of tea are distinguished by the processing they undergo. Leaves of Camellia sinensis soon begin to wilt and oxidize if not dried quickly after picking. The leaves turn progressively darker because chlorophyll breaks down and tannins are released. This process, enzymatic oxidation, is called fermentation in the tea industry although it is not a true fermentation: it is not caused by micro-organisms, and is not an anaerobic process. The next step in processing is to stop the oxidation process at a predetermined stage by heating, which deactivates the enzymes responsible. With black tea this is done simultaneously with drying. Without careful moisture and temperature control during its manufacture and thereafter, fungi will grow on tea. This form of fungus causes real fermentation that will contaminate the tea with toxic and sometimes carcinogenic substances and off-flavours, rendering the tea unfit for consumption.

Tea is traditionally classified based on producing technique:

• Green tea: Un-wilted and unoxidized
• Yellow tea: Un-wilted and unoxidized but allowed to yellow
• White tea: Wilted and unoxidized
• Oolong: Wilted, bruised, and partially oxidized
• Black tea/Red tea: Wilted, crushed, and fully oxidized
• Post-fermented tea: Green Tea that has been allowed to ferment/compost

Contents:

Tea contains catechins, a type of antioxidant. In a fresh tea leaf, catechins can be up to 30% of the dry weight. Catechins are highest in concentration in white and green teas, while black tea has substantially less due to its oxidative preparation. Tea contains theanine, and the stimulant caffeine at about 3% of its dry weight, translating to between 30mg and 90mg per 8oz (or 0.25 L) cup depending on type, brand and brewing method. Tea also contains small amounts of theobromine and theophylline. Tea also contains fluoride, with certain types of brick tea made from old leaves and stems having the highest levels.