Wikipedia, the Free Encyclopedia 03-11-09 12:04
Total Page：16
File Type：pdf, Size：1020Kb
Tea - Wikipedia, the free encyclopedia 03-11-09 12:04 Tea From Wikipedia, the free encyclopedia Tea is the agricultural product of the leaves, leaf buds, and internodes of the Camellia sinensis plant, prepared and cured by various methods. "Tea" also refers to the aromatic beverage prepared from the cured leaves by combination with hot or boiling water,[1] and is the common name for the Camellia sinensis plant itself. After water, tea is the most widely-consumed beverage in the world.[2] It has a cooling, slightly bitter, astringent flavour which many enjoy.[3] The four types of tea most commonly found on the market are black tea, oolong tea, green tea and white tea,[4] all of which can be made from the same bushes, processed differently, and in the case of fine white tea grown differently. Pu-erh tea, a post-fermented tea, is also often classified as amongst the most popular types of tea.[5] Green Tea leaves in a Chinese The term "herbal tea" usually refers to an infusion or tisane of gaiwan. leaves, flowers, fruit, herbs or other plant material that contains no Camellia sinensis.[6] The term "red tea" either refers to an infusion made from the South African rooibos plant, also containing no Camellia sinensis, or, in Chinese, Korean, Japanese and other East Asian languages, refers to black tea. Contents 1 Traditional Chinese Tea Cultivation and Technologies 2 Processing and classification A tea bush. 3 Blending and additives 4 Content 5 Origin and history 5.1 Origin myths 5.2 China 5.3 Japan 5.4 Korea 5.5 Taiwan 5.6 Thailand 5.7 Vietnam 5.8 Tea spreads to the world 5.9 United Kingdom Plantation workers picking tea in 5.10 United States of America Tanzania. 5.11 India 5.12 Sri Lanka/Ceylon 5.13 Africa and South America 6 Health effects http://en.wikipedia.org/wiki/Tea Pagina 1 van 27 Tea - Wikipedia, the free encyclopedia 03-11-09 12:04 7 Etymology and cognates in other languages 7.1 The derivatives from tê 7.2 Derivatives from cha or chai 8 Tea culture 9 Preparation 9.1 Black tea 9.2 Green tea 9.3 Oolong tea 9.4 Premium or delicate tea 9.5 Pu-erh tea (or Pu'er) 9.6 Serving 9.7 Adding milk to tea 9.8 Other additives Tea plant (Camellia sinensis) from 10 Economics of tea Köhler's Medicinal Plants. 11 Statistics 11.1 Production 11.1.1 Tea production certification 11.2 Trade 11.2.1 Export 11.2.2 Import 11.2.3 Prices 12 Packaging 12.1 Tea bags 12.2 Pyramid tea bags 12.3 Loose tea Loose dried tea leaves 12.4 Compressed tea 12.5 Instant tea 12.6 Canned tea 13 Storage 14 See also 15 Notes 16 References 17 External links Traditional Chinese Tea Cultivation and Technologies Camellia sinensis is an evergreen plant that grows mainly in tropical and sub-tropical climates. Nevertheless, some varieties can also tolerate marine climates and are cultivated as far north as Pembrokeshire in the UK mainland[7] and Washington in the United States. In addition to a zone 8 climate or warmer, tea plants require at least 50 inches of rainfall a year and prefer acidic soils.[8] Traditional Chinese Tea Cultivation and Studies believes that high-quality tea plants are cultivated at elevations of up to 1500 meters (5,000 ft): at these heights, the plants grow more slowly and acquire a better flavour.[9] Only the top 1-2 inches of the mature plant are picked. These buds and leaves are called flushes.[10] A plant will grow a new flush every seven to ten days during the growing season. Leaves of Camellia sinensis, the tea plant http://en.wikipedia.org/wiki/Tea Pagina 2 van 27 Tea - Wikipedia, the free encyclopedia 03-11-09 12:04 A tea plant will grow into a tree if left undisturbed, but cultivated plants are pruned to waist height for ease of plucking.[11] Two principal varieties are used: the small-leaved China plant (C. sinensis sinensis), used for most Chinese, Formosan and Japanese teas (but not Pu-erh); and the large-leaved Assam plant (C. sinensis assamica), used in most Indian and other teas (but not Darjeeling). Within these botanical varieties, there are many strains and modern Indian clonal varieties. Leaf size is the chief criterion for the classification of tea plants:[12] tea is classified into (1) Assam type, characterized by the largest leaves; (2) China type, characterized by the smallest leaves; and (3) Cambod, characterized by leaves of intermediate size.[12] Processing and classification Main article: Tea processing A tea's type is determined by the processing which it undergoes. Leaves of Camellia sinensis soon begin to wilt and oxidize if not dried quickly after picking. The leaves turn progressively darker as their chlorophyll breaks down and tannins are released. This process, enzymatic oxidation, is called fermentation in the tea industry, although it is not a true fermentation: it is not caused by micro-organisms, and is not an anaerobic process. The next step in processing is to stop the oxidation process at a predetermined stage by heating, which deactivates the enzymes responsible. With black tea this is done simultaneously with drying. Without careful moisture and temperature control during manufacture and packaging, the tea will grow fungi. The fungus causes real fermentation that will contaminate the tea with toxic and sometimes carcinogenic substances, as well as off-flavors, rendering the tea unfit for consumption. Tea is traditionally classified based on the techniques with which it is produced and processed.[13] White tea: Unwilted and unoxidized Yellow tea: Unwilted and unoxidized but allowed to yellow Green tea: Wilted and unoxidized Oolong: Wilted, bruised, and partially oxidized Black tea: Wilted, sometimes crushed, and fully Tea leaf processing methods (Simplified) oxidized Post-fermented tea: Green Tea that has been allowed to ferment/compost Blending and additives Main article: Tea blending and additives Almost all teas in bags and most other teas sold in the West are blends. Blending may occur in the tea-planting area (as in the case of Assam), or teas from many areas may be blended. The aim is to obtain better taste, higher price, or both, as a more expensive, better- tasting tea may cover the inferior taste of cheaper varieties. Some teas are not pure varieties, but have been enhanced through additives or special processing. Tea is highly receptive to inclusion of various aromas; this may cause problems in processing, transportation and storage, but also allows for the design of an Tea weighing station north of almost endless range of scented and flavored variants, such as http://en.wikipedia.org/wiki/Tea Pagina 3 van 27 Tea - Wikipedia, the free encyclopedia 03-11-09 12:04 Tea weighing station north of almost endless range of scented and flavored variants, such as Batumi, Russian Empire before 1915 vanilla, caramel, and many others. Content Tea contains catechins, a type of antioxidant. In a freshly-picked tea leaf, catechins can compose up to 30% of the dry weight. Catechins are highest in concentration in white and green teas, while black tea has substantially fewer due to its oxidative preparation.[14][15] Research by the U.S. Department of Agriculture has suggested that levels of antioxidants in green and black tea do not differ greatly, with green tea having an Oxygen Radical Absorbance Capacity (ORAC) of 1253 and black tea an ORAC of 1128 (measured in μmolTE/100g).[16] Tea also contains theanine and the stimulant caffeine at about 3% of its dry weight, translating to between 30 mg and 90 mg per 8 oz (250 ml) cup depending on type, brand[17] and brewing method.[18] Tea also contains small amounts of theobromine and theophylline,[19] as well as fluoride, with certain types of brick tea made from old leaves and stems having the highest levels.[20] Dry tea has more caffeine by weight than coffee; nevertheless, more dried coffee is used than dry tea in preparing the beverage,[21] which mean that a cup of brewed tea contains significantly less caffeine than a cup of coffee of the same size. Tea has no carbohydrates, fat, or protein. Origin and history According to Mondal (2007, p. 519): "Camellia sinensis originated in southeast Asia, specifically around the intersection of latitude 29°N and longitude 98°E, the point of confluence of the lands of northeast India, north Burma, southwest China and Tibet. The plant was introduced to more than 52 countries, from this ‘centre of origin’." Based on morphological differences between the Assamese and Chinese varieties, botanists have long asserted a dual botanical origin for tea; however, statistical cluster analysis, the same chromosome number (2n=30), easy hybridization, and various types of intermediate hybrids and spontaneous polyploids all appear to demonstrate a single place of origin for Camellia sinensis — the area including the northern part of Burma, and Yunnan and Sichuan provinces of China.[22] According to this theory, tea plants in southeast Asia may have been the products of the 19th Century and 20th Century hybridizing experiments. Yunnan Province has also been identified as "the birthplace of tea...the first area where humans figured out that eating tea leaves or brewing a cup could be pleasant".[23] Fengqing County in the Lincang City Prefecture of Yunnan Province is said to be home to the world's oldest cultivated tea tree, some 3,200 years old.[24] Origin myths In one popular Chinese legend, Shennong, the legendary Emperor of China and inventor of agriculture and Chinese medicine was drinking a bowl of boiling water some time around 2737 BC when a few leaves were blown from a nearby tree into his water, changing the color.