Tea processing is the method in which the leaves from the tea plant Camellia sinensis are transformed into the dried leaves for brewing tea. The categories of tea are distinguished by the processing they undergo. In its most general form, tea processing involves different manners and degrees of oxidation of the leaves, stopping the oxidation, forming the tea, and drying it.
At least six different types of tea are produced:
- White (wilted and unoxidized)
- Yellow (unwilted and unoxidized, but allowed to yellow)
- Green (unwilted and unoxidized)
- Oolong (wilted, bruised, and partially oxidized)
- Black (wilted, sometimes crushed, and fully oxidized; called ‘red tea’ in China)
- Post-Fermented (green tea that has been allowed to ferment/compost; ‘black tea’ for the Chinese)
After being picked, the tea leaves soon begin to wilt and oxidize unless immediately dried. An enzymatic oxidation process triggered by the plant’s intracellular enzymes causes the leaves to turn progressively darker as their chlorophyll breaks down and tannins are released. This darkening is stopped at a predetermined stage by heating, which deactivates the enzymes responsible. In the production of black teas, halting by heating is carried out simultaneously with drying. The innate flavor of the dried tea leaves is determined by the type of cultivar of the tea bush, the quality of the plucked tea leaves, and the manner and quality of the production processing they undergo. After processing, a tea may be blended with other teas or mixed with flavourants to alter the flavor of the final tea.