Tea Camellia sinensis Theaceae

Camellia has eighty-two species, yet only one has a dominant role in various cultures and has risen to dominate worldwide beverage markets. Camellia sinensis is an evergreen shrub or tree, kept artificially small by the harvesting and plucking of top, terminal leaf shoots. These leaves, variously processed, contain caffeine (1 to 5 percent) and traces of theophylline, theobromine, and other xanthine alkaloids; however, it is the essential oils that are responsible for the flavors. Polyphenols (5 to 27 percent) are responsible for the dark brown tannin color.

The plant's origin is in China, but its geographic distribution today reflects its cultivation in China and Japan and in countries that were previously colonies of the British Empire, such as Sri Lanka, India, Kenya, and the Carolinas in the United States, as well as Uganda, Turkey, and Indonesia. The plant can grow as far north as 43°N in the Caucasus mountains and as far south as 28°S in Argentina. There are two varieties cultivated in different environments: C. sinensis var. sinensis is a dwarf tree with small leaves that is grown in the highlands, whereas C. s. var. assamica is a larger tree with larger leaves that is grown in the lowlands. Tea plants are cross-pollinated, and they are propagated by seeds

Tea pickers in the Himalayas, India, between 1890 and 1923. Library of Congress, Prints & Photographs Division, LC-USZ62-82954.

and cuttings. The harvesting of tea is very labor-intensive: in the lowlands, every 7 days; in the highlands, every 14 days. A mature plant yields about 2 lb green leaf per year, or about 0.5 lb dry weight. One acre yields 1000 lb per annum, and 2 billion lb of black tea are harvested each year.

Three main production processes can occur with the plucked leaves, each of which produces a well-known type of tea; however, the general public tends not to associate the process with the product. Green tea is made from shoots that are steamed (Japanese) or parched (Chinese), rolled, and dried. The heat halts the oxidative degradation process that turns leaves dark-colored, leaving them green and light tasting. While traditionally consumed mostly in Asia, green tea is earning a global reputation for its healthful properties. Pouchong or Oolong tea is made from shoots that are withered in the sun, stored indoors, and pan-dried at a succession of temperatures. This produces the typical curly leaves of this "half-fermented" tea. Oolong tea, typically encountered in Chinese restaurants in Europe and North America, has a relatively minor level of consumption worldwide compared to black tea. Black tea is made from fresh shoots that are first rolled and then crushed; thereafter, the mass is allowed to ferment, which allows oxidation of phenolic compounds, giving the dark, black color. The application of heat ends the fermentation, and the leaves are pan dried. Although India and Sri Lanka produce most of the black tea, it is consumed throughout world. However, there are rather striking regional differences in consumption. These differences are related directly to the story of coffee.

See: Age of Industrialization and Agro-industry pp. 369-71

Coping with Asthma

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