Tea is an infusion made by steeping processed leaves, buds, or twigs of the tea bush, Camellia sinensis, in hot water for a few minutes. The processing can include oxidation, heating, drying, and the addition of other herbs, flowers, spices, and fruits.
The four basic types of true tea are
- black tea,
- oolong tea,
- green tea, and
- white tea
Tea is one of the most widely-consumed beverages in the world. It has a cooling, slightly bitter, astringent flavor. It has almost no carbohydrates, fat, or protein.
Tea is a natural source of the amino acid theanine, methylxanthines such as caffeine and theobromine, and polyphenolic antioxidant catechins.
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
Tea and its antioxidants
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 and its caffeine content
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.
Many blends of real tea are prepared by adding other plants to an actual tea (black, oolong, green, yellow or white tea); for example, the popular Earl Grey tea is black tea with bergamot, Jasmine tea is Chinese tea with Jasmine, and Genmaicha is green tea with roasted rice.
Such preparations are still called "tea".
Herbal tea, tisane, or ptisan is an herbal infusion made from anything other than the leaves of the tea bush (Camellia sinensis).
Herbal teas can be made with 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. Seeds and roots can also be boiled on a stove.
The tisane is then strained, sweetened if so desired, and served. Many companies produce herbal tea bags for such infusions. Although tisane does not contain as much polyphenols, it does promote other various health qualities such as relaxation and calming effects.