1. About Tea
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.
Many of the active substances in black tea do not develop at temperatures lower than 90 °C (194 °F). As a result, black tea in the West is usually steeped in water near its boiling point, at around 99 °C (210 °F). Since boiling point drops with increasing altitude, it is difficult to brew black tea properly in mountainous areas.
Western black teas are usually brewed for about four minutes. In many regions of the world, however, actively boiling water is used and the tea is often stewed. In India, black tea is often boiled for fifteen minutes or longer to make Masala chai, as a strong brew is preferred. Tea is often strained while serving.
A food safety management group of the International Organization for Standardization (ISO) has published a standard for preparing a cup of tea (ISO 3103: Tea — Preparation of liquor for use in sensory tests), primarily intended for standardizing preparation for comparison and rating purposes.
In regions of the world that prefer mild beverages, such as the Far East, green tea is steeped in water around 80 to 85 °C (176 to 185 °F). Regions such as North Africa or Central Asia prefer a bitter tea, and hotter water is used. In Morocco, green tea is steeped in boiling water for 15 minutes.
The container in which green tea is steeped is often warmed beforehand to prevent premature cooling. High-quality green and white teas can have new water added as many as five or more times, depending on variety, at increasingly higher temperatures.
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.
Pu-erh teas require boiling water for infusion. Some prefer to quickly rinse pu-erh for several seconds with boiling water to remove tea dust which accumulates from the ageing process, then infuse it at the boiling point (100 °C or 212 °F), and allow it to steep from 30 seconds to five minutes.
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. About Tea Culture