Biochemistry of tea

Main groups of substances contained in elite Chinese tea

 

1. Water

2. Proteins and amino-acids

3. Alkaloids

4. Tea polyphenols

4.1  Phenols

4.2  Tannins

4.3  Katechines

4.4  Flavonols

4.5  Anthocyanidins

4.6  Pheno-acids

5. Carbohydrates (saccharides)

6. Organic acids

7. Lipids

8. Pigments

9. Fragrant substances (essential oils)

10.  Vitamins

11.  Ferments. Fermentation

12.  Inorganic compounds

 

Judging by historical sources humans had become familiar with tea several thousand years ago. Painstaking and slowly people had been studying its properties during many centuries but only in last several decades – due to progress in science and technology it became possible to get comparatively full-ranged conception of chemical composition of tea and idea about interaction of these compounds (biochemical synthesizing reactions and transforming reactions of tea components condition each other).

Chemical composition of a tea leaf is a base on which quality and specific properties of tea take their form.  Today we know that tea contains more than 500 various complicated and simple by their structure chemical compounds (more than 450 are organic ones and about 50 – inorganic). Moreover some substances are whether not yet found or are known only in very general aspects. Therefore tea is the most complicated and the most various plant by its chemical structure.

The significance of each substance-group of all tea substances one can consider from three points of view: in aspect of influence on tea-tree physiology; in aspect of influence on tea infusion (as ready product); in aspect of influence on function of human body (when possible we shall discuss each group of substances in such sequence).

At first chemical substances provide the growth and development of tea-tree and then – being a constituent part of a tea leaf – make for formation of principal properties of tea, and at last, having been ingested, provide energy for formation and regeneration of body tissues, for regulation of various functions, and for strengthening of organism.

Chemical substances in tea can be divided into two major groups: water (moisture) (75-78% in fresh fleches) and dry matter (22-25% in fresh fleches). Inorganic matters constitute 3.5-7.0% and organic matters constitute 93-96.5%. Only 30-50% of all substances is water-soluble (extractive) and passes into tea infusion. In green teas the amount of extractive substances is more than in fermented ones, and in young teas it is more than in teas, made of old and tough leaves.

 

1. Water (moisture)

Water is irreplaceable element necessary for vital activity of tea-tree and is the most important mediating substance providing behavior of a number of chemical transformations while processing of vegetable raw stuff (water plays an important role in creation of chemical medium because it lets one substance enter in close interaction – on level of molecules – with another one). For example the dry-curing changes character and speed of biochemical processes which in turn alter chemical composition and physical properties of tea leaf and prepare it to further processing. Significant alteration in polyphenol complex, amino-acid composition, essential oils, enzymatic activity and so on, accompanies water loss. The final drying stops enzymatic activity and other biochemical processes when in tea leaf the maximum of valuable substances accumulates. Changes of taste and aroma during processing depend on water content in raw stuff and therefore water is major biochemical marker assisting to control transformation of qualitative features during manufacturing.

2. Proteins and amino-acids

Proteins are the most significant constituent element of tea leaf. All enzymes are proteins (we’ll consider enzymes further on). Besides that proteins are the sources of amino-acids which emerge during processing of stuff. Proteins constitute 20-30% of dry matter; fraction of amino-acids constitutes 1-4% of dry matter. We may mention some important amino-acids (all in all there are more than 25 amino-acids): theanin, glutamate, aspartate, asparagine, arginine, serine, alanine, histidine, threonine, glutamine, glycine, valine, phenylalanine, thyrosin, leucine, isoleucine. Theanine accounts for 40-50% of total amino-acid content. This is unique amino-acid. Besides tea leaves it is contained (in smaller amount) in apples, mushrooms, red and white wine). Content of amino-acids depends on the degree of tea maturity (in young teas there are more, in old teas – less amino-acids) and on the season of collection (early spring teas a rich in amino-acids as opposed to autumn tea of the most late collection).

The majority of tea proteins are gluthelines – proteins soluble in alkali, the minority of proteins are albumins – the proteins soluble in water. Green teas contain many albumins; in fermented teas the fraction of gluthelins is higher. Water-soluble proteins along with other compounds determine taste of tea infusion. Amino-acids, and especially, theanine, are the most important elements which take part in creating tea aroma and give to tea its clean refreshing notes. The closest connection between amino-acids and aromatic properties is observed in green and red teas. In interaction with sugar and polyphenols under high temperature amino-acids form organic compounds – volatile aldehydes and therefore influence upon aromatic bouquet of tea. Besides that some amino-acids possess smell themselves. Also amino-acids influence upon color range of dry tealeaves and of brewed infusion.

Some amino-acids (e.g., valine, leucine, threonine, phenylalanine), which are contained in tea, are essential ones, i.e. they cannot be synthesized in human body and must be taken in with food. When there is deficit or absence of at least one of them in food, synthesis of proteins and many other biologically important substances necessary to life ceases. Moreover, the main “tea” amino-acid theanine five times strengthens the immune function in organism: it mobilizes T-cells of immune system – they activate themselves and migrate to an alteration focus. T-cells regulate secretion of protective protein interferon which inhibits intracellular viral proliferation. Interferon plays a very important role in body defense against infection. Glutamat is also very important to vital activity of human body because it helps to restore exhausted nervous system, normalizes protein and carbohydrate metabolism and is necessary for the work of skeletal muscles.

3. Alkaloids

Alkaloids are nitrogen-containing cyclic physiologically active compounds. In one and the same organism there usually exist several alkaloids with similar structure. Tea alkaloids are presented by purine bases. Among tea alkaloids there are three ones – caffeine, theobromine and theophylline. Tea leaves contain caffeine bound to tannin. This complex is called “theine”.

The most part of alkaloids in tea is presented by caffeine (its content is 2-5% of dry weight). The content of caffeine depends on the breed of tea-tree, time of picking and method of processing. Large enough amount of caffeine is contained in large-leaved teas. At the same time this amount is larger in teas growing in southern regions of China than in northern regions. Theine is generated in tea-plant during growth and this is why in young hardly opened leaflets the amount of caffeine is more than in tea manufactured from rough overripe stuff (this is why gradation of tea stands in direct dependence on theine content). Drying and fermentation result in partial loss of caffeine. Caffeine concentration in green teas is lower than in red teas. In the most common Chinese teas concentration of caffeine is 2.94 and 3.67% respectively.

Caffeine is well-soluble in water and therefore its content in tea is proportional to concentration of brewed beverage (but into infusion it extracts only 35-80% of caffeine). However even the strong tea can’t make real damage to your health. Chemical bound of caffeine with tanning substances provide more mild influence on the human organism in comparison with pure caffeine of coffee. Besides that theine doesn’t accumulate in human organism and this excludes the danger from frequent drinking. Theine possesses many healing properties: it stimulates the central nervous system (it topes up, heightens motor activity, heightens mental and physical capacity, and lowers tiredness and sleepiness) and cardiovascular system, works as diuretic, stimulates circulation, activates an aerobic metabolism, improves digestion, muscle tonus, prevents rise of blood cholesterol, prevents platelet aggregation and thromboses.

Theobromine stimulates heart activity, dilates vessels of heart and brain, and also dilates bronchi. Besides that it possesses antispasmodic and diuretic effects. In comparison with caffeine it presents much less effect on CNS. Pharmacologically theophyllin is similar to theobromine (dilates blood vessels of heart and brain, dilates bronchi, stimulates CNS), but differs in that it is more potent diuretic.

 

4. Tea polyphenols

This expression denotes more than 30 types of polyphenole compounds which are contained in tea. Tannin content significantly depends on species, sort, and time of picking and age of tea leaf. Distribution of polyphenols in tea fleche is as follows: the most part of them are located in buds. There are more polyphenols in the young hardly opened first leaflet than in more matured second or third leaf. There are more polyphenols in leaves than in stem. Fraction of polyphenols is equal to 20-35% of dry weight.

There are four main groups among tea polyphenols: catechines, flavonols, anthocyanidines and phenolic acids. Except the last group all the rest phenolic compounds are related to wide-spread vegetable substances known as “flavonoids” (flavonoids are the group structurally related natural phenolic compounds which are contained in highest plants; mutual transformations are highly possible by means of enzymatic and usual rections; the most part of flavonoids are biologically active, i.e. they are bioflavonoids).

4.1 Phenols are aromatic organic compounds in molecules of which hydroxyl group (-OH) is bound with carbon atom of aromatic cycle. Phenol compounds present the most common and numerous class of natural substances possessing biological activity (activity is provided by high reactivity of molecules due to interaction between hydroxyl and aromatic cycle)/ According to number of –OH groups one distinguishes single-atomic and multi-atomic phenols. Simple phenols with one or two aromatic cycles possess many various biological properties (they are the most active) and the widest range of pharmacological effects. Large enough amount of these compounds are present in growing tea leaf but during processing they are being partly lost. In ready tea phenols are mainly presented in the form of polyphenolic compounds (polyphenols, tea polyphenols). They are considered “tanning substances” or tannins.

4.2  Tannins have an ability to form strong stable bounds with proteins and some other natural polymers (cellulose, pectines) and these bounds let explain their tanning effect. The most common tanning substances originate from plant class of dicotyledons (tea-tree is included into namely this botanic class), where they accumulate in maximal amounts. It was established that in tea leaves there are specialized tissues consisting of specific cells in which the tanning substances are saved).

In a fresh tea leaf tannins possess bitter taste, after processing however this taste disappears and tea acquires pleasant tartness; and this is the main taste of tea infusion. These are non-oxidized polyphenols which are responsible for tartness of tea (they create effect of tartness, astringent feeling in mouth due to what tea stimulates salivary glands and slakes thirst well). Oxidized polyphenols give color and taste to tea infusion. The more degree of oxidation is, the more color and less tartness. Content of tanning substances in green teas is significantly higher than in fermented teas because in green teas they are contained in nearly non-oxidized state. Besides that in all teas of highest gradations usually there are more tannins than in teas of low gradations.

4.3 Catechines (derivatives of flavan-3-ol) are natural biologically active substances of bioflavonoid group. Until now there has been found 12 types of catechines. Some of them are related to the simple or free catechines, the other – to the group of esters (they possess tart, bitter-astringent taste; they consist 70-80% of all catechines). Percentage of catechines decreases as tea leaf ages and depends on breed of tea-tree (in leaves of large-leaved breeds there are more catechines than in leaves of small-leaved breeds). Most of all catechines are contained in white tea, a little less in green tea. Tea contains four main kinds of catechines: epicatechine (EC, 5-10% of all amount of catechines), epigallocatechine (EGC, 10-15%), epicatechine gallate (ECG, 10-20%) and epigallocatechine gallate (EGCG, 50-60%). Epigallocatechine gallate (EGCG) – is the most potent catechine of all four main catechines by its antioxidant activity. It is 25-100 times more than the activity of vitamins C and E.

It was established that tea possess the strong antoxidant properties due to high content of catechines, in particular epigallocatechine gallate (EGCG) which constitutes 50-60% of all catechine group.

Quality of green tea depends on concentration of catechines and their derivatives because they provide formation of strong, rich and long-playing taste. Concentration of catechines decreases as tea leaf ages and therefore among green teas the young ones are the most highly rated. These are teas picked early in spring. Besides that some studies have shown that polyphenols and primary products of their oxidation influence on color range of infusion and on aroma of green teas. Oxidative transformations of catechines also play important role in fermentation of tea. These sum=bstances significantly determine color, aroma and taste of tea. So, for example the products of oxidative polymerization of catechines – pigments theaflavine and thearubigine – play the decisive role in creating rich golden-amber color and taste in infusion of red teas.

As was said an antioxidant index of an extract of green tea surpasses one of vitamins C, E and of Selenium and Zinc too. Antioxidant effect of tea catechines is closely related to their ability to absorb free radicals. Thereby tea and in the first place green tea, being potent antioxidant decreases an amount of free radicals in human organism preventing cancer. Tea catechines and, In particular, epigallocatechine gallate (EGCG) effectively lower cholesterol level and level of LDL in the blood serum. These substances are also exclusively useful in strengthening of immune system (so, for example, epigallocatechine-3-gallate affects lymphocytes responsible for normal immune reactions so that virus of human immune deficit can’t enter the cell and deteriorate its function. Catechines regulate capillar permeability, heighten their elasticity and resiliency and facilitate effective use of ascorbic acid by human organism. Therefore catechines are considered substances possessing P-vitamin properties and are used in treating diseases connected with capillaropathies, in patients with oedemata of vascular origin etc. Catechines of tea possess antibacterial properties as well and are used in treating dysentery.

4.4 Flavonols are the most wide-spread vegetable pigments (they are crystals of yellow color). Flavonols are compounds stable enough to resist alterations during processing. Flavonols present one of the most important groups which directly affect properties of green teas (in particular – color range because flavjnols are compounds consisting partly of soluble substances of green and yellow color). Flavonols are substances possessing p-vitamin properties. They decrease permeability and increase durability of blood capillaries, facilitate assimilation of vitamin C, take part in processes of oxidation-reduction, regulate activity of some endocrine glands (first of all of the thyroid gland).

4.5 Anthocyanidines are substances synthesized in result of hydrolysis of anthocyans (vegetable pigments) under influence of enzymes and acids. Anthocyanidines give bitter-astringent taste to tea.

Anthocyanidines help vitamin C to enter cells, strengthen capillaries and joints. These substances are useful in restoration and saving of vision, protect organism against aggressive effects of free radicals and prevent atherosclerosis, cancer and arterial hypertension.

4.6 Phenolic acids are cyclic (aromatic) acids which contain one acid group –COOH and also one or more hydroxyls –OH bound to its nucleus. Content of phenolic acids in tea is not large/ The main ones are gallic acid (3,4,5-trihydroxibenzoat), theogalline, chlorogenic acid, ellagic acid, coumaric acid and caffeic acid. Phenolic acids are present not only in green but also in fermented teas.

Phenolic acids possess astringent, cholagogic, diuretic< strengthening capillaries and anti-inflammatory action. They regulate function of thyroid gland, stimulate antitoxic function of liver.

Substances belonging to flavonoids are often called “natural biolofgical modulators of reactions” due to their ability to change organism’s reaction on allergens, viruses and carcinogens. Evidence of this is their anti-inflammatory, anti-allergic Antiviral and anti-carcinogenic properties. Flavonoids are the potent antioxidants, possess cholagogic, anti-ulcer, diuretic< antispasmodic and other useful properties. They take part in immune reactions, affect lipid metabolism and enzymatic activity.

5. Carbohydrates (saccharides)

Carbohydrates represent the wide group of organic compounds which contain carbon, oxygen and hydrogen (general formula (Cm(H2O)n). We find them in all living organisms. Tea contains monosaccharides, disaccharides and polysaccharides. Carbohydrates constitute 20-25% of tea dry weight.

Carbohydrates play various roles in living organisms. Monosaccharides in tea-tree are primary products of photosynthesis and are input material for biosynthesis of various glycosides, polysaccharides and of the substances of other classes (amino-acids, fatty acids, polyphenols etc.).

Mono- and disaccharides (soluble saccharides: sucrose, glucose, fructose, maltose; 0.8-4%) are well soluble in water and take part in creation of taste peculiarities of tea. The most tea saccharides (more than 20%) belong to the group including starch, cellulose, hemicelluloses, lignin. These substances are insoluble in water. Pectins, which are products of carbohydrate metabolism, constitute ca. 4% of dry weight. Soluble pectin define a degree of saturation of tea infusion and glossy glitter on the surface of tealeaves. Besides that pectins play significant role in preserving of tea quality because it possesses a high hygroscopic property. (Pectin acid covers each tealeaf with thin gelatinous film which is little permeable to water). In a lack of pectin acid absorbability becomes high and tea therefore spoils quicker.

Nearly all substances beneficially influencing on tea quality and are in the basis of its color, aroma and taste are contained in young teas in larger amounts than in old tea. Therefore tea made from tender  young fleches is better than tea made from overripe stuff.

Carbohydrates constitute the most (often the main) part of human food ration. Biological role of carbohydrates is determined by their energetic value. Carbohydrates are used whether as direct source of heat or as reserve of energy. Carbohydrates also perform supporting and structural function. Carbohydrates take part in protective reactions (for example the viscous secrets released by various glands contain much carbohydrates and their derivates; they protect walls of hollow organs – esophagus, intestines, stomach and bronchi) against mechanical damage, penetration of bacteria and viruses. Some findings confirm that carbohydrate structures participate in such highly specific phenomena of cell interaction as fertilization, “recognition” of cells in tissue differentiation and rejection of foreign tissues etc.

Presence of small amounts of soluble saccharides is one of the most important advantages of tea. It not only makes tea an ideal antisclerotic remedy, particularly in association with iodine and vitamin P, but also provides preserving in tea vitamin B which is actively absorbed by saccharides.

6. Organic acids

Organic acids play an important role in metabolism of tea-tree, are – mainly – the products of sugar transformation. They take part in biosynthesis of alkaloids, glycosides, amino-acids and other biologically active compounds; serve as links between separated stages of fat, protein and carbohydrate metabolism.

Organic acids play an important role in forming of tea aroma. Today we know that among aromatic components ca. 25 types of organic acids are present. Some of them have no smell themselves but become aromatic due to oxidation (e.g. linoleic acid). Other organic acids are good sorbents of aromatic components (e.g. palmitinic acid).

Organic acids stimulate release of gastric juice and therefore improve digestion, regulate the state of intestinal flora, support normal acid-base balance, activate peristaltic movements in intestines and decrease risk of many gastro-intestinal and other diseases.

Malic acid is present in all cells of human organism and plays important role in transformation of sugars and fats into adenosintriphosphate (ATP) which is a universal accumulator and carrier of energy. This acid also quickens formation of bile in the liver, possesses anti-inflammatory properties and has ability to improve absorption of iron from food. Citric acid is a necessary link in the system of biochemical reactions of cell respiration. This acid regulates acid-base balance in organism and ionic balance; it possesses antioxidant properties too. Succinic acid enhances energetic metabolism in tissue cells, protect organism against radiation, possesses general health-improving and sanative properties. Oxalic acid facilitates effective assimilation of calcium. Palmitinic acid which belongs to the class of saturated fatty acids is used in organism as source of energy. Linoleic acid is one of three irreplaceable fatty acids necessary for assimilation and prevention of oxidation of fat-soluble vitamins A, D, E and K. All body cells need irreplaceable fatty acids because their deficit leads to alteration of skin and hair.

7. Lipids

Lipids are fat-like substances (derivates of highest fatty acids, spirits or aldehydes). They are present in all living cells and are responsible for normal passing of basic physiological processes. Main lipids in tea are fats, phospholipids, glycerides and glycolipids. They constitute ca. 8% of total dry weight.

Lipids are present in cytoplasm of cells of tea-tree and this is why they regulate process of other substances entering into cells (being one of the components of cellular wall they affect membrane permeability). These substances affect activity of many enzymes; they participate in establishing of energetic reserve and in creation of protective hydrophobic and thermo-isolating covers in vegetable organism.

Also these compounds play significant role in formation of tea aroma.

In human organism lipids participate in neurotransmission, in muscular contraction, in creation of intercellular contacts, in immune-chemical processes and provide protection of various organs against mechanical alteration. Fats play a particular role in vital processes. Fats are the main source of energy (energetic value of fats is two and a half times more than this of carbohydrates). Besides that fats presenting in the most of cell membranes perform important structural function.

8. Pigments

Pigments are colored substances within tissue structures of living organisms. Pigments of tea (ca. 1% of total dry weight) determine color of dry tealeaves, of brewed infusion and of leaves of weak tea.

Pigments play important and various roles in vital activities of tea0tree organism. Pigment system is a link between brightness in outer space and metabolism in organism. One of the most important function of pigments (and first of all chlorophyll) is their participation in photosynthesis. Besides that absorption of light by pigments plays role in growth and development of a plant. Many pigments (e.g. carotenoides) protect organism against harmful influence of ultra-violet solar radiation and besides that play significant role in transfer of oxygen, i.e. in respiration. Pigments determine coloration of tea-tree which is important for its adaptation to environment. (In plants color serves for attraction of insects as pollinators and birds as disseminators).

Fat-soluble pigments participate in forming of color range of dry tealeaves and of leaves of weak tea. So, for example, color of green teas depends not only on general content of chlorophyll but also on relation of chlorophyll a to chlorophyll b. Chlorophyll a has dark-green color, chlorophyll b – yellow-green one. In young fresh fleches there is much chlorophyll b and therefore dry tealeaves have tender pale-yellow points and rich glossy glitter. Color of green tea infusion is determined not only by presence of green chlorophylline (derivate of chlorophyll) but by presence of flavonols as well. In processing of red teas by fermentation chlorophyll is nearly entirely destroyed. At that time in vegetable tissues of tea leaf formation of substances of black-brown color occurs. This is a result of oxidation of tea polyphenols (polyphenol oxidase catalyzes oxidation leading to polymerization of phenols), proteins are bound to pectins and saccharides which results in red with brown tinges or rich dark-blue-black colors. Thereby the color range of teas of all types is closely connected with percentage, composition and transformation of various pigments. Pigments affect taste of red teas as well. For example, theaflavines give to tea a pleasant, clean, refreshing and live taste, enhances force and intensiveness of taste. Thearubigines make a beverage rich, allot to it thick long-playing taste along with strong stimulating effect and astringent properties.

Pigments contained in tea influence beneficially upon human organism. Pigments formed in result of oxidation of polyphenols are polymeric polyphenolic compounds and therefore also possess useful properties of polyphenols and first of all antioxidant activity (besides that these substances lower cholesterol level, prevent cardio-vascular diseases and cancer, stimulate immune system and facilitate weight loss etc.).

In leading medical centers in many countries in recent years they have found new healing properties of chlorophyll. Now it is known that it is a fighter against infections and even cancer. This pigment possesses a potent antibacterial effect and stimulates various organs and systems: cardiovascular, respiratory, gastro-intestinal and kidneys.

Xanthophyll and carotene belong to the group of carotinoides. The latter possess potent antioxidant properties due to which they level harmful effects of free radicals (xanthophyll slows down ageing and development of malignant tumors). Carotinoids improve activity of immine and reproductive sysyems. In particular they are useful for prevention of cataract and other eye diseases (e.g. age dependent macular degeneration).

9. Aromatic (fragrant) substances, essential oils

The term “aromatic substances” is collective name for volatile substances of tea immediately determining its quality. Essential oils are odorous very volatile substances which are contained in various parts of plants, mainly in flowers, fruits and leaves.

In spite of that the percentage of these substances is small (0.02% in fresh fleches. It means that for to produce 100 g of essential oil one must process more than 500 kg of tea leaves. Content of aromatic substances In green teas is 0.005%, 0.01-0.03 in red teas). Essential oils are numerous and various. According to scientific analysis tea can contain more than 300 various aromatic substances: in fresh fleches ca. 50, in green teas more than 100, in red teas more than 300. Essential oils are multi-component mixtures of organic compounds. The main elements of tea aromatic substances are alcohols, phenols, aldehydes, ketones, acids, esters, lactones, nitrogenous compounds, sulfocompounds, hydrocarbons (mainly terpenes) and oxides.

Aroma of ready tea is determined by composition and concentration of aromatic substances in picked stuff. Percentage and composition of aromatic compounds in tea depends on season, tea-tree breed, degree of stuff maturity and place of cultivation. As a rule, in spring tea there are more aromatic substances than in summer and autumn teas, in young teas more than in mature one. Tea made from young tender fleches possesses pekoe flavor which carries tinges of living freshness. In every surrounding tea has its specific aromatic range. For example red tea from district An-Hoi has characteristic honey aroma and teas from mountains have smell of the ripe chestnut.

Carriers and savers of aroma are resin substances (resin spirits, resin acids, resin phenols and other organic substances).

During processing the most part of essential oils (70-80%) is lost, however at the same time there emerge new components which give characteristic aroma to tea. This is why aromas of teas are as various as tea sorts. It is because teas are processed differently.

Essential oils possess the whole range of healing and prophylactic properties. However the most significant is their ability to affect CNS. These substances stimulate nervous system, level harmful stress, emotional excitability, enhance capacity for work.

10. Vitamins

Vitamins are the group of organic compounds of various chemical nature. Tea is rich in vitamins, their percentage is equal to 0.6-1% of dry weight. Vitamins can be water-soluble and fat-soluble. To fat-soluble vitamins belong vitamins A (the main quantity), D, E, K. These substances don’t dissolve in water and therefore theyare not extracted into brewed infusion. To the group of water-soluble vitamins belong vitamins C, B1, B2, B3, B5, B11, P, inosite. Most of all tea is rich in vitamin C (in 100 g of highest gradation elite green tea is contained 250-500 mg). By the content of vitamin C green tea is comparable with citrus fruits although part of vitamin is lost during processing. Thereby along with green tea a man gets nutrients which have an immense significance for normal metabolism and vital activity.

Physiological functions of vitamins in vital activity of organisms (vegetable and animal as well) are very significant. Vitamins whether are parts of enzymes or take part in enzymatic reactions and therefore play an immense role in metabolism. Vitamins participate not only in process of degradation of various substances and release of contained in them energy but also in process of synthesis and creation of biological structures.

All water-soluble vitamins of tea which are extracted into infusion influence beneficially upon human health:

Vitamin C (ascorbic acid) is a potent antioxidant, participates in all types of metabolism, provides normal permeability of capillary walls, enhances their durability and elasticity, participates in hormone synthesis, facilitates strengthening of bone tissues, enhances resistance of organism to harmful effects, facilitates tissue regeneration.

Vitamin B1 (thiamine) participates in carbohydrate metabolism and in connected with it energetic, fat, protein, water-salt metabolism, regulates activity of nervous system, protects organism from harmful effects of ageing, alcohol and tobacco, and regulates activity of endocrine glands.

Vitamin B2 (riboflavin) is necessary for formation of red blood cells and antibodies, for cell respiration and growth, improves state of skin, positively influences upon liver, eyes and mucous membranes of gastro0intestinak tract.

Vitamin B3 (vitamin PP, nicotinic acid) normalizes level of blood cholesterol and liver function, regulates oxidation and reduction in organism.

Vitamin B5 (pantothenic acid) – anti-allergenic vitamin, normalizes lipid metabolism, stimulates biosynthesis and release of hormones from adrenal cortex. Due to this action it is the potent remedy for treatment of such diseases as arthritis, colitis, allergy and cardiovascular disease.

Vitamin B11 (carnitine) plays a decisive role in fat metabolism, facilitates cleaning of organism enhances the function of cardio-vascular system.

Vitamin P (rutin) – a group of flavonoid compounds which support impermeability of capillary walls, decrease their fragility, prevent oxidation of ascorbic acid and adrenaline, facilitate storage and assimilation of vitamin C. Tea catechines enhance effects of vitamin P. The most vitamin P-activity is characteristic for green tea. Drinking 3-4 glasses a day of good strength we provide our organism with a prophylactic daily dose of vitamin P.

Inosite participates in metabolism of fats and cholesterol and, above it, possesses tranquilizing properties.

11. Fermentation

Ferments (enzymes)

The most principal difference between various teas is degree of their fermentation. Teas may be post-fermented (black tea), fermented (red tea), non-fermented (green tea), weak-fermented (white tea, yellow tea) and half-fermented (ulung).

Ferments are specific protein catalysts which participate in a number of biochemical reactions having place during vital activity of a tea-tree and  during processing. In composition of tea there are presented (as a rule in a bound insoluble state) various ferments: oxidoreductases (the main one is polyphenoloxidase), peroxidase, catalase, hydrolase, lyase, phosphorylase, transferase, isomerase.

Nearly all biochemical reactions (vegetable and animal as well) which in their totality define metabolism of the body are catalyzed by ferments. Therefore by directing and regulating metabolism ferments play the most important role in all processes of vital activity.

By regulating enzymatic activity by means of technological methods, inhibiting or, in contrary, enhancing their activity we can stimulate certain reactions and in result we can get the kind of tea which would possess necessary and specific to it property. For example in processing of green teas one uses a special procedure frying-out (sha-tsing – deliverance from greenery, de-enzyming). Under high temperature we inhibit ferment activity what in short period of time leads to inhibition of a whole number of chemicak transformations which results in formation of distinguishing peculiarities of a given tea. Red teas belong to category of fermented teas in which process of enzymatic oxidation is nwarly full. As a result of enzymatic oxidative polymerization of tea polyphenols (mainly catechines) which process is going under the influence of ferments and as a result of other transformations in a tea leaf emerge three types od colored substances – yellow theaflavine, red thearubigine and a brown pigment TB. Due to these reactions  red tea acquires one of its distinguishing peculiarities – its infusion is clean and transparent with glossy glitter and brewed beverage is colored in rich and bright red tinges< and near the cup brim we see a golden rim. Oxidative polymerization of tea polyphenols is accompanied by formation and changes in amount of various aromatic components. The increase in amount of aromatic substances is  particularly rapid and intensive during fermentation, and therefore a degree of fermentation of red tea changes not only color range and taste of brewed infusion but has an immense significance for the process of formation of aromatic bouquet of a given tea.

Black post-fermented teas (pu-er) deserve a special attention in discussion of ferment significance. In the processing of tea pu-er they apply the specific procedure – wetting of vegetable stuff in heaps. At this stage in moister environment microorganisms are born (nowadays they often use the method of artificial seeding of some species of mold mushrooms and bacteria. Due to this method in a body of tea fleche the number of very complicated biochemical reactions occurs. For example, the main role in the process of formation the major properties of a tea pu-er is played by the so-called “black mold” (Aspergillus niger). In such cases necessary ferments are produced by this microorganism. Aspergillus niger is able to release endoenzymes (cell-bound enzymes) and exoenzymes (extracellular enzymes) as well. Among these ferments one can find more than 20 kinds of hydrolases, e.g. glucoamylase (amyloglucosidase), cellulose and pectinase. Polysaccharides, fats, proteinsnatural fibers, pectin, insoluble substances and other organic compounds undergo hydrolysis. The most part of its products are monosaccharides, amino-acids, hydrated pectin and soluble carbohydrates. Hydrolysis facilitates effective release ant diffusion into water of useful active components contained in tissues of tea leaf. Due to such chemical transformation taste quality of tea infusion are enhanced, a beverage acquires non-astringent, clean and rich taste with sweetish aftertaste.

12. Inorganic (mineral) compouns

Mineral substances constitute 3.5-7.0% of dry weight. Inorganic compounds are divided into two groups – water-soluble (2-4%) and njn-water-soluble (1.5-3%). Under high temperature these compounds turn into ash, thereby ca. 50-60% of this ash are water-soluble ashes. In young teas the main part of ash is water-soluble. Content of total ash is one of the obligatory parameters of testing quality of exported tea (total ash content has to be no more than 6.5%).

Many mineral substances are bound to complex compounds but being in colloid state are susceptible to dissolution in water and releasing into tea infusion enhance nutrient value of a beverage and can beneficially influence upon human organism. Tea is a natural complex of mineral elements which are actively included in a process of formation of other substances. These elements are present in optimal amounts and, besides that in a form optimally suitable for assimilation. There are ca. 27 various mineral elements in tea. They are presented in following table^

 

Name of element

Amount by daily use of 10 g of tea

Curative and health-improving properties

Potassium (K)

140-300 mg

Daily requirement for adult 2.0-3.0 g

Facilitates regulation of water-salt balance in an organism.

Facilitates normal muscular (participates in muscular contraction) and nervous function (along with magnesium improves state of patients with various diseases, restores energy in patients suffering from insomnia, weakness, headaches)

Normalizes activity of cardiovascular system.

Magnesium (Mg)

1.5-5.0 mg

Daily requirement (adults) ca. 4.5 mg/1 kg of body weight

Is necessary in all main biological processes in organism, because activates enzymatic activity (e.g. supports normal carbohydrate metabolism)

Support muscle tonus, stimulates muscular work, enhance ability of cells to absorb oxygen.

Strengthens nervous system, is a natural tranquilizer.

Prevents heart diseases.

Participates in osteogenesis (is necessary for strengthening of skeleton)

Stimulates motor activity of intestines and gall-bladder.

Manganese (Mn)

3.8-8.0 mg

Daily requirement in adults 2.7-7.0 mg

Participates in all kinds of metabolism playing an important role in activation of various ferments.

Has a particular significance in function of sexual glands, musculoskeletal system, nervous system.

Fluorine

1.5-5.0 mg

Daily requirement in adults 2.0-4.0 mg

Prevents caries (facilitates restoration of enamel and decreases permeability of dental tissues slowing down reproduction of microorganisms in dental deposit, facilitate remineralization of enamel)

Facilitates osteogenesis

Stimulates immune reactions

Calcium (Ca)

3.0-4.0 mg

Daily requirement in adults 800-1000 mg

Is a main structural element of bone tissue

Participates in processes of excitation in nervous tissue and in muscular contraction

Plays a major role in blood coagulation at all stages

Is necessary for normal function of immune system

Participates in activity of various ferment systems

Facilitates elimination of heavy metal salts and radio-nuclides, possesses anti-allergic and anti-inflammatory properties

Sodium (Na)

2.o-8.0 mg

Daily requirement in adults 4.0-6.0 g

Regulates movements of substances into and out of cells

Participates in water-salt metabolism and in supporting of acid-base balance

Sulfur (S)

5.8-8.0 mg

Daily requirement in adults 500-1000 mg

Is a structural element of various proteins including ferments

Participates along with vitamins of group B in metabolism

Possesses anti-allergic properties

Iron (Fe)

0.6-1.0 mg

Daily requirement in adults 10-15 mg

Plays an important role in hematogenesis, is necessary for synthesis of the main protein of red blood cell – hemoglobin

Is irreplaceable component in various proteins, is a part of a whole number of ferments, catalysts of oxidative and reductive processes

Supports a high level of immune resistance of organism

Copper (Cu)

0.5-0.6 mg

Daily requirement in adults 1.0-5.0 mg

Participates in oxidative and reductive processes supporting various ferments influencing upon activity of some hormones and vitamins

Participates in hematopoesis and in many metabolic reactions

Enhances regenerative activity in tissues

Prevents cancer

Stimulates immune system

Nickel (Ni)

0.05-0.28 mg

Daily requirement in adults 60 mcmol

Performs indirect influence upon organism via microflora and ferments of gastro-intestinak tract

Participates directly in metabolism

Participates in synthesis and functioning of major components of DNA, RNA and proteins

Silicon (Si)

o.2-0.5 mg

Daily requirement in adults 20-30 mg

Is necessary for formation of basic substance of bones and cartilages, take an immediate part in processes of mineralization of bone tissues

Actively participates in functioning of a system of blood coagulation

Is necessary for build-up of epithelial and nervous cells

Zinc (Zn)

0.2-0.4 mg

Daily requirement in adults 10-20 mg

Is contained in various ferments, influences upon oxidative and reductive processes, catalyzes energetic processes in cells

Stimulates growth and development

Decreases deposition of cholesterol on vessel walls

In organism is naturally used for making its own antioxidants

Provides a normal visual function

Selenium (Se)

Minimal quantity

Daily requirement in adults 50-70 mcg

Is an important part of antoxidant system of organism

Prevents cancers

Is a cofactor in a number of oxidative and reductive ferments

Stimulates releasing of antibodies enhancing the immune system and protection against infectious diseases and colds

Facilitates elimination of radio-nuclides and mercury.