From Big Medical Encyclopedia

TEA — a product of processing of green listonosny escapes of a tea plant of types of Thea sinensis and this Thea assamica. Theaceae. The drink made from dry tea well satisfies thirst, possesses the expressed tonic action on an organism.

The homeland of a tea plant — southwest China and the adjacent regions of India, Vietnam, Burma. In the USSR the tea plant is cultivated in the Georgian SSR, the Azerbaijani SSR, Krasnodar Krai of RSFSR.

H is long leaf — black and green, and also pressed — tiled, brick and tableted. Long leaf Ch. receive from young two-trifoliate escapes — flyshes. Production includes it processes of drying, twisting, fixing (for green Ch.) or fermentations (for black H), drying, at to-rykh in a tea leaf happen considerable biochemical changes. As a result of drying and twisting 80 — 85% of cells of a leaf collapse, the share of extractives considerably increases. During the fixing (processing of a tea leaf the hot moistened air or steam for preservation of its main properties) inactivate enzymes and further biochemical transformations stop. In the course of fermentation under the influence of oxidizing (a polifenoloksidaza, a peroka idose, a catalase, etc.) and other enzymes in a tea leaf the specific substances defining aroma, taste and color black Ch. are formed, the chlorophyll collapses, tanning agents partially are oxidized, there is a hydrolysis of difficult compounds of carbohydrates and glycosides. The dried-up Ch. is sized tea leaves and mixes up (is blended) according to a compounding. For receiving the flavored Ch. add the crushed parts of fragrant plants to it (flowers of a jasmine, a rose, leaves of mint, etc.) or essential oils (see) and food essences (see).

The tiled and tableted Ch. is received by pressing of seedings and a crumb of black or green H. Brick Ch. develop from the raw materials received from the coarsened tea leaves and escapes. Raw materials are subjected to heat treatment, pressed and dried.

As a part of a tea leaf hundreds of chemical connections — proteins, carbohydrates, mineral substances, vitamins, alkaloids, polyphenols, etc. are found. But because by dry Ch. it is used for preparation of infusion, most of them has no essential value for the food characteristic of Ch. as drink. Content of extractives, to-rye pass into infusion, makes in green tea 40 — 45%, in black 35 — 40%. They define food value Ch. and its tonic action on an organism. The main of them — caffeine (see), theophylline (see), theobromine (see), tanning agents, and also essential oil, colorants.


the Content of caffeine make in long leaf black tea 1,8 — 4%, in green — 1,8 — 2,5%, in brick — apprx. 1,2 — 1,5%. At Ch.'s zavarivaniye passes into infusion apprx. 60 — 70% of caffeine, hl. obr. in the form of complex connection with a tannin (see). The glass of Ch. which is strong made long leaf contains 0,02 — 0,1 g of caffeine. Caffeine in such quantities has moderate exciting effect on c. the N of page, stimulates cardiac performance and kidneys. The caffeine connected with a tannin is soaked up in went. - kish. a path more slowly more softly, than pure caffeine or its drugs also works.

A tannin of tea represents a complex of tanning agents, hl. obr. catechins (see) and their gallic ethers. Content of tannin in green tea 12 — 20%, in black — 8 — 15%, in brick — not less than 4%. We will dissolve tannin in hot water; with fall of temperature of water it drops out in a deposit why infusion Ch. becomes muddy. Tannin is good adsorbent, possesses the antimicrobic and knitting action, stimulates motility of intestines. The catechins which are a part of a tannin have properties of citrin (see Bioflavonoida), normalize permeability of capillaries.

Tea contains apprx. 0,01 — 0,02% of essential oil of complex structure (see. Essential oils). Availability in it of citronellol, geraniol and other components possessing exciting action supplements tonic effect of caffeine. From mineral elements Ch. it is especially rich with fluorine and manganese.

For preparation of one glass of drink Ch. it is recommended to take

1 — 3 g dry black Ch. (green slightly more). Quite often Ch. is drunk with sugar and milk that increases nutrition value of drink. From tiled and brick Ch. usually make drink with milk, sometimes add fat and salt to it. Nutrition value of such Ch. depends on a share of milk and fat. H as drink should be taken at once after preparation since it quickly loses flavoring properties.

The unlimited use too strong Ch. can be followed by the general excitement, sleeplessness, heartbeat, increase in the ABP that is connected with overdose of caffeine. A large amount of the liquid entered with Ch. can have an adverse effect on activity of cardiovascular and urinary systems. Therefore strong Ch. do not recommend to drink to the persons having sleeplessness, arterial hypertension, heart diseases and kidneys. It is also not recommended to drink strong Ch. before going to bed.

Dry Ch., packaged in vla-go-and an air-tight container, stored in dry (relative humidity no more than 70%), well aired room, keeps the qualities within not less than 8 months. It is necessary to store Ch. separately from products with a strong smell (spices, a herring and so forth) since he easily perceives foreign smells. At the wrong storage of Ch. essential oil disappears and is oxidized, colorants change, its humidity can increase. At moisture content in Ch. over 8,5% he quickly «grows old», at 12% and more — grows mouldy.

Ch.'s suitability for food is determined by organoleptic properties — color, aroma, taste of infusion. Content in it of caffeine, tannin, moisture and ferroprimesy shall correspond to GOST. Apply organoleptic, physical and chemical, hromatografichesky methods and microscopy to control of Ch.'s quality.

Ch.'s substitutes are fruit or flower Ch. prepared from leaves and flowers of the nontoxic plants having aroma (a wild strawberry, a pear, currant, a willow-herb, the tributary, a marjoram, a linden, etc.). The infusions prepared from them do not contain caffeine and sometimes replace natural H. Bibliography: Hygiene of food, under the editorship of.

K. S. Petrovsky, t. 2, page 285, M., 1971; Zaprometov M. N. Biochemistry of catechins, M., 1964; Pokrovsky A. A. Metabolic aspects of pharmacology and toxicology of food, M., 1979; Turova A. D. and With and p about N and to about in and E. N. Medicinal plants of the USSR and their use, M., 1984; X about the h about l and in and I. A. Tekhnologiya of tea, M., 1977, bibliogr.

A. N. Zaytsev, K. M. Dzhemukhadze.