1.1 Processing and classification
Main article: Tea processing
Teas of different levels of oxidation (L to R): green, yellow, oolong, and black
Tea is generally divided into categories based on how it is processed. At least six different types 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 紅茶 [hóngchá], “red tea” in Chinese tea culture);
- Post-fermented: green tea that has been allowed to ferment/compost (called 黑茶 [hēichá] “black tea” in Chinese tea culture).
After picking, the leaves of C. sinensis soon begin to wilt and oxidize unless immediately dried. An enzymatic oxidationprocess triggered by the plant’s intracellular enzymes causes the leaves to turn progressively darker as their chlorophyllbreaks 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. Without careful moisture and temperature control during manufacture and packaging, growth of undesired molds and bacteria may make tea unfit for consumption.
Oolong tea is brewed around 82 to 96 °C (185 to 205 °F), with the brewing vessel warmed before pouring the water. Yixing purple clay teapots are the traditional brewing-vessel for oolong tea which can be brewed multiple times from the same leaves, unlike green tea, seeming to improve with reuse. In the southern Chinese and Taiwanese Gongfu tea ceremony, the first brew is discarded, as it is considered a rinse of leaves rather than a proper brew.
Cold brew tea
While most tea is prepared using hot water, it is also possible to brew a beverage from tea using room temperature or cooled water. This requires longer steeping time to extract the key components, and produces a different flavor profile. Cold brews use about 1.5 times the tea leaves that would be used for hot steeping, and are refrigerated for 4–10 hours. The process of making cold brew tea is much simpler than that for cold brew coffee.
Cold brewing has some disadvantages compared to hot steeping. If the leaves or source water contain unwanted bacteria, they may flourish, whereas using hot water has the benefit of killing most bacteria. This is less of a concern in modern times and developed regions. Cold brewing may also allow for less caffeine to be extracted.
Pouring from height
The flavor of tea can also be altered by pouring it from different heights, resulting in varying degrees of aeration. The art of elevated pouring is used principally to enhance the flavor of the tea, while cooling the beverage for immediate consumption.
In Southeast Asia, the practice of pouring tea from a height has been refined further using black tea to which condensed milk is added, poured from a height from one cup to another several times in alternating fashion and in quick succession, to create a tea with entrapped air bubbles, creating a frothy “head” in the cup. This beverage, teh tarik, literally, “pulled tea” (which has its origin as a hot Indian tea beverage), has a creamier taste than flat milk tea and is common in the region.
2. Tea Space