tea

tea, beverage produced by steeping in freshly boiled water the young leaves and leaf buds of the tea plant, Camellia sinensis. Two principal varieties are used, the small-leaved China plant (C. sinensis variety sinensis) and the large-leaved Assam plant (C. sinensis variety assamica). Hybrids of these two varieties are also grown. The leaves may be fermented or left unfermented.

History of the tea trade

According to legend, tea has been known in China since about 2700 bce. For millennia it was a medicinal beverage obtained by boiling fresh leaves in water, but around the 3rd century ce it became a daily drink, and tea cultivation and processing began. The first published account of methods of planting, processing, and drinking came in 350 ce. Around 800 the first seeds were brought to Japan, where cultivation became established by the 13th century. Chinese from Amoy brought tea cultivation to the island of Formosa (Taiwan) in 1810. Tea cultivation in Java began under the Dutch, who brought seeds from Japan in 1826 and seeds, workers, and implements from China in 1833.

In 1824 tea plants were discovered in the hills along the frontier between Burma and the Indian state of Assam. The British introduced tea culture into India in 1836 and into Ceylon (Sri Lanka) in 1867. At first they used seeds from China, but later seeds from the Assam plant were used.

The Dutch East India Company carried the first consignment of China tea to Europe in 1610. In 1669 the English East India Company brought China tea from ports in Java to the London market. Later, teas grown on British estates in India and Ceylon reached Mincing Lane, the centre of the tea trade in London. By the late 19th and early 20th centuries, tea growing had spread to Russian Georgia, Sumatra, and Iran and extended to non-Asian countries such as Natal, Malawi, Uganda, Kenya, Congo, Tanzania, and Mozambique in Africa, to Argentina, Brazil, and Peru in South America, and to Queensland in Australia.

Classification of teas

Teas are classified according to region of origin, as in China, Ceylon, Japanese, Indonesian, and African tea, or by smaller district, as in Darjeeling, Assam, and Nilgris from India, Uva and Dimbula from Sri Lanka, Keemun from Chi-men in China’s Anhwei Province, and Enshu from Japan.

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Teas are also classified by the size of the processed leaf. Traditional operations result in larger leafy grades and smaller broken grades. The leafy grades are flowery pekoe (FP), orange pekoe (OP), pekoe (P), pekoe souchong (PS), and souchong (S). The broken grades are: broken orange pekoe (BOP), broken pekoe (BP), BOP fanning, fannings, and dust. Broken grades usually have substantial contributions from the more tender shoots, while leafy grades come mainly from the tougher and maturer leaves. In modern commercial grading, 95 to 100 percent of production belongs to broken grades, whereas earlier a substantial quantity of leafy grades was produced. This shift has been caused by an increased demand for teas of smaller particle size, which produce a quick, strong brew.

The most important classification is by the manufacturing process, resulting in the three categories of fermented (black), unfermented (green), and semifermented (oolong or pouchong). Green tea is usually produced from the China plant and is grown mostly in Japan, China, and to some extent Malaysia and Indonesia. The infused leaf is green, and the liquor is mild, pale green or lemon-yellow, and slightly bitter. Black tea, by far the most common type produced, is best made from Assam or hybrid plants. The infused leaf is bright red or copper coloured, and the liquor is bright red and slightly astringent but not bitter, bearing the characteristic aroma of tea. Oolong and pouchong teas are produced mostly in southern China and Taiwan from a special variety of the China plant. The liquor is pale or yellow in colour, as in green tea, and has a unique malty, or smoky, flavour.

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Processing the leaf

In tea manufacture, the leaf goes through some or all of the stages of withering, rolling, fermentation, and drying. The process has a twofold purpose: (1) to dry the leaf and (2) to allow the chemical constituents of the leaf to produce the quality peculiar to each type of tea.

The best-known constituent of tea is caffeine, which gives the beverage its stimulating character but contributes only a little to colour, flavour, and aroma. About 4 percent of the solids in fresh leaf is caffeine, and one teacup of the beverage contains 60 to 90 milligrams of caffeine. The most important chemicals in tea are the tannins, or polyphenols, which are colourless, bitter-tasting substances that give the drink its astringency. When acted upon by an enzyme called polyphenol oxidase, polyphenols acquire a reddish colour and form the flavouring compounds of the beverage. Certain volatile oils contribute to the aroma of tea, and also contributing to beverage quality are various sugars and amino acids.

Only black tea goes through all stages of the manufacturing process. Green tea and oolong acquire their qualities through variations in the crucial fermentation stage.