Schemes reflecting the chemical composition of tea. Biochemistry of tea

Introduction

Judging by historical sources, people got acquainted with tea several millennia ago and painstakingly studied its features over many centuries, but only in recent decades, thanks to scientific and technological progress, it has become possible to get a relatively complete picture of what chemicals are in tea and how they interact with each other (biochemical reactions of synthesis and transformation of tea components determine each other).

The chemical composition of the tea leaf is the basis on which the quality and characteristic properties of tea are formed. To date, it is known that tea contains more than 500 different, complex and simple in structure, chemical compounds (over 450 of them are organic substances and about 30 are inorganic), while many chemical components of tea remain undiscovered or recognized only in the very general view. Therefore, tea is the most complex and most diverse plant in its chemical composition.

The value (basic functions) of each group of substances that make up tea can be considered from three points view: in terms of influence on the physiology of the tea tree; in terms of influence on the quality of tea as a finished product; from the point of view of the impact on the life of a person - a tea consumer (if possible, we will consider them in this order). Chemicals first ensure the growth and development of the tea tree, then, being an integral part of the tea leaf, determine the formation of the main properties of tea, and at the very end, getting into the human body, they serve to cover energy costs, build and renew body tissues, regulate various functions and general strengthening of the body.

Chemicals in the composition of tea fall into two main groups: water (moisture (water, moisture); 75-78% in fresh flushes) and dry matter (dry matter; 22-25% in fresh flushes), while inorganic ( mineral) compounds account for 3.5-7.0%, and organic - 93-96.5%. In dry tea, only 30-50% of the substances are extractive (soluble in water) and are released into the tea infusion. In green teas, as a rule, there are more extractive substances than in fermented ones, in young tea - more than in tea made from old and coarse leaves.

1. Water (moisture).

Water is the simplest stable chemical compound of hydrogen and oxygen under normal conditions.

The moisture content of fresh flushes is typically 75-78%, which can certainly vary depending on the degree of maturity of the raw material, the type of tea tree, and the season of the year. A fairly large amount of moisture (up to about 84%) is contained in young, tender buds and freshly hatched leaves, flushes covered with moisture from rain and dew drops, flushes of large-leaved species, as well as in buds and leaves during the rainy season and in spring. Old, overripe leaves, flushes of medium-leaved and small-leaved species, buds and leaves in the dry season and on clear, sunny days are characterized by a lower moisture content.

In finished tea, which has been fully processed, the moisture content, as a rule, can vary from 5-8% to 16%. However, for each variety, this indicator is set separately in the corresponding standard. So, for example, for jasmine teas it is ≤ 8.0%, for a number of green teas ≤ 6.5%, for red tea ≤ 6.5%, for loose Pu-erh tea ≤ 12.5%, for pressed Pu-erh ≤ 13%. Too high a moisture content can cause the tea to quickly spoil and oxidize residual enzymes, which will change the color of the tea.

Water is an indispensable element in the life of the tea tree and is the most important mediator substance that ensures the flow of a number of chemical transformations in the process of processing plant materials (water plays an important role in the formation of the chemical environment, since it allows one substance to enter into a close, at the level molecules, interaction with another substance). For example, withering changes the nature and speed of biochemical processes, which, in turn, change the chemical composition and physical properties of the tea leaf and prepare it for further processing. The loss of moisture is accompanied by significant changes in the polyphenol complex, the composition of amino acids, essential oils, enzyme activity, etc. The final drying stops the action of enzymes and other biochemical processes when the maximum amount of valuable substances accumulates in the tea leaf. During processing, the color, aroma and taste of tea change depending on changes in the moisture content of the raw material, so water is the main biochemical marker (indicator) that helps control the transformation of tea quality characteristics during the production process.

Proteins are high molecular weight natural organic substances built from amino acids. Amino acids are a class of organic compounds that combine the properties of acids and amines, that is, they contain, along with the carboxyl group -COOH, the amino group -NH 2. Proteins are the most important component tea leaf. Proteins are all enzymes (these substances will be considered separately). In addition, proteins serve as a source of amino acids that arise during the processing of plant materials. The share of proteins accounts for 20-30% of the dry matter contained in tea (hence, in terms of the amount of proteins and nutritional value, the tea leaf is practically not inferior to legumes, but only 1-3% of them are soluble in water), the amino acid content is 1-4 % by weight of dry matter. Among the main amino acids contained in tea (there are more than 25 types in total), one can name: theanine (theanine), glutamic acid (glutaminic acid), aspartic acid (aspartic acid), asparagine (asparagine), arginine (arginine), serine (serine ), alanine (alanine), histidine (histidine), threonine (threonine), glutamine (glutamine), phenylalanine (phenylalanine), glycine (aminoacetic acid (glycine, aminoacetic acid)), valine (valine), tyrosine (tyrosine), leucine (leucine), isoleucine (isoleucine). About 40-50% of the total amino acid content is theanine, a unique acid that is not found in any other plants (except for tea, this substance, but in smaller quantities, is found in apples, mushrooms, red and white wine). The content of amino acids depends on the degree of maturity of tea (there are more of them in young tea than in old tea) and the season of harvesting vegetable raw materials (in early spring teas are rich in amino acids, the least of them are in autumn tea of ​​the latest harvest).

Proteins play a fundamental role in the structure and life of organisms. It is they who carry out the metabolism and energy transformations, which are inextricably linked with active biological functions. Proteins serve as a source of restoration and renewal of the cytoplasm of cells, the formation of enzymes, hormones, etc.

It is known that some proteins dissolve easily in water, others require small concentrations of salts to dissolve, others pass into solution only under the influence of strong alkalis, etc. The tea leaf contains mainly alkali-soluble proteins (glutelins) and lesser degree proteins that are soluble in water (albumin). Green teas contain more albumins, while fermented teas, on the contrary, contain more glutelins. The water-soluble proteins of tea, along with other compounds, determine the taste of tea infusion. During processing, the amount of albumin in tea increases. Amino acids, and in particular theanine, are essential elements that take part in the formation of tea aroma and give the tea clean, refreshing notes. The closest relationship between amino acids and aromatic properties is observed in green teas and red teas. When interacting with sugar, as well as polyphenols at elevated temperatures during processing, amino acids form organic compounds - volatile aldehydes and, thereby, affect the formation of the aromatic bouquet of tea. In addition, some amino acids themselves have a certain smell. Amino acids also affect the color range of dried tea leaves and brewed infusions. So, for example, during the fermentation process in the production of red teas, amino acids react with orthoquinones (orthoquinone) and form compounds that determine the color of the drink, and during the drying process they participate in the formation of juicy glossy almost black shades of dry tea.

Many amino acids (for example, valine, leucine, threonine, phenylalanine), which are part of tea, are essential, that is, they cannot be synthesized in the human body, and must be supplied with food. With a lack of these amino acids or in the absence of at least one of them in food, the synthesis of proteins and many other biologically important substances necessary for life is impossible. Moreover, the main "tea" amino acid L-theanine five times enhances the protective function of the body: it mobilizes cells of the immune system - T-cells, they are activated, migrate to the lesion. T-cells regulate the secretion of the protective protein interferon (interferon), which suppresses the reproduction of viruses in the cell and is considered the key in the body's defense system against infections. Glutamic acid is also extremely important for the life of the human body, as it actively contributes to the restoration of an exhausted nervous system, normalizes protein and carbohydrate metabolism, and is necessary in the work of skeletal muscles.

3. Alkaloids (alkaloids).

Alkaloids are nitrogen-containing cyclic physiologically active organic compounds. In the same plant, there are usually several alkaloids that are similar in structure. Tea alkaloids are represented by purine bases. The composition of the tea leaf includes three different types of alkaloids: caffeine (caffeine), theobromine (theobromine) and theophylline (theophylline). In the tea leaf, caffeine is found in combination with tannins and is often referred to as theine.

As a rule, the alkaloid content of plants is determined by the nature of the soil and its agrotechnical processing, the height of the terrain above sea level, the water regime, the length of the day, the intensity of solar radiation, and other natural factors. Most of the tea alkaloids are represented by caffeine (its content is 2-5% by weight of dry matter), while the amount of theobromine and theophylline is minimal. That is why very often an indicator of the total content of alkaloids in tea is the content of caffeine. Thus, at the same weight ratios, tea contains more caffeine than coffee (0.65-2.7%), however, for the preparation of one cup of tea, as a rule, a smaller amount of dry tea leaf is used than coffee for the preparation of one cup of coffee drink. The amount of caffeine in tea depends on the type of tea tree, the timing of the collection of raw materials, the method of processing the leaves. A sufficiently large amount of caffeine is found in the leaves of large-leaved tea tree species, while it is more in teas grown in the southern regions of the country than in the northern ones. Theine is formed in the tea plant during growth, so there is more caffeine in young, barely opened leaves than in tea made from coarse, overripe raw materials (therefore, the grade (gradation) of tea is directly dependent on the theine content). Fermentation and drying lead to the loss of a certain amount of caffeine. At temperatures above 120ºC, caffeine begins to sublimate (sublimation is the property of a substance to turn into a gas when heated, bypassing the liquid state), and at 180ºC it actively volatilizes. In the production of green teas, the raw materials are subjected to high-temperature processing, while part of the caffeine is sublimated, which leads to a decrease in the caffeine content in tea. That is why the concentration of caffeine in green teas is lower than in red teas. In the most common varieties of Chinese tea, it is respectively 2.94% and 3.67%.

Alkaloids in plant organisms are actively involved in chemical reactions of metabolism. Alkaloids are by-products of metabolism, they serve as a reserve for protein synthesis, chemical defense against animals and insects, regulators of physiological processes (growth, metabolism and reproduction) or detoxification end products, neutralizing substances whose accumulation could damage the plant.

Theine is easily soluble in water (and its ability to dissolve increases with increasing water temperature) and is the most important flavoring element in the composition of tea. So, for example, the appearance after cooling in the infusion of red tea of ​​the effect of milky turbidity (the so-called “cream down” of the color of light soy sauce, a sign of high-quality tea) indicates the formation of a macromolecular complex from theine and polyphenolic substances (tea pigments - theaflavins ( theaflavin) and thearubigins (thearubigen), formed as a result of the oxidation of catechins), which decomposes when the temperature drops.

Caffeine dissolves well in water, so its content in tea is directly proportional to the concentration of the drink being made (but only 35-80% of caffeine is extracted into the infusion). However, even strong tea cannot cause severe harm to health. The chemical bond of tea caffeine with tannins ensures its milder effect on the human body compared to pure coffee caffeine. In addition, theine does not accumulate in the human body, which eliminates the risk of poisoning with frequent use of tea. Thein has numerous medicinal properties: it has a stimulating effect on the central nervous system(well tones, increases motor activity, increases mental and physical performance, reduces fatigue, drowsiness) and the cardiovascular system, acts as a diuretic, stimulates blood circulation, activates oxygen metabolism, promotes digestion, improves muscle tone, prevents cholesterol levels, lowers education thrombi (preventing platelet aggregation).

Theobromine stimulates cardiac activity, dilates the vessels of the heart and brain, as well as the bronchi, has an antispasmodic and diuretic effect. Compared to caffeine, it causes a much less pronounced effect on the central nervous system. Theophylline is similar in pharmacological action to theobromine (expands the blood vessels of the heart and bronchial muscles, excites the central nervous system), but differs from it by a stronger diuretic effect.

4. Tea polyphenols (tea polyphenols).

The term "tea polyphenols" is a generic name for more than 30 types of polyphenolic substances that are found in tea. The content of tannins largely depends on the type, variety, collection time and age of the tea leaf. The distribution of polyphenols in tea flush is as follows: most of them are found in the kidney. In a young, barely opened first leaf, there are more of these substances than in the more mature second and third leaves, and in the leaves - more than in the stem. The share of tea polyphenols accounts for 20-35% of the mass of dry matter.

There are four main groups of tea polyphenols: catechins, flavonols, anthocyanidins, and phenolic acids. With the exception of the last group, the above phenolic compounds belong to common plant substances known as "flavonoids" (flavonoids are a group of structurally related natural phenolic compounds found in higher plants, the mutual transformations of these compounds are easily carried out using enzymatic and conventional reactions; most flavonoids are biologically active (belong to the group of bioflavonoids)).

4.1 Phenols- These are compounds of the aromatic series, in the molecules of which the hydroxyl groups -OH are bonded to the carbon atoms of the aromatic ring (aromatic cycle). Phenolic compounds are one of the most common and numerous classes of natural compounds with biological activity (activity is ensured by the fact that the aromatic nucleus and OH groups combined in one molecule affect each other, significantly increasing the reactivity of each other). According to the number of OH groups, monatomic and polyhydric phenols are distinguished. Simple phenols with one or two aromatic rings have a variety of biological properties (they are the most active) and the widest spectrum of pharmacological action. A sufficiently large amount of these compounds is present in the growing tea leaf, but they are largely lost during processing. In the finished tea, phenols are mainly represented by polyphenolic compounds (polyphenols, tea polyphenols), which are traditionally classified as "tanning (tanning) substances", or "tannins" (in many sources - "tannins", "theotannins"; French. tannin , from tanner - 'to tan the skin': originally (since the end of the 18th century), the term "tannin" was used to refer to a mixture of substances extracted from a number of plants with water, which has the property of turning raw skin into tanned).

4.2 Tannins have the ability to form strong bonds with proteins and some other natural polymers (cellulose, pectin), which explains their "tanning effect". The most common tannins are in the representatives of the dicotyledonous class (tea belongs to this class), where they accumulate in the maximum number. Many factors influence the accumulation of tannins. The main ones are the age and phase of plant development. In many plants, the largest amount accumulates in the flowering phase, and decreases in the fruiting phase. Factors environment(light, soil, moisture, temperature, altitude, etc.) also have a significant effect on the accumulation of tannins. In the southern and mountainous regions, under the influence of light and on soils rich in microelements, the content of these compounds increases. In the plant, tannins are in a dissolved state and are localized mainly in small cavities (cytoplasmic vacuoles) of the cells of the main tissue of the plant - the parenchyma. It has been established that there are specialized tissues in tea leaves, consisting of cells specific in shape and size, in which tannins are deposited.

To date, there are several hypotheses regarding the details of the process of biosynthesis of tannins in plants. Scientists believe that tannins in plants perform versatile biological functions, participating in the redox processes of the plant organism.

If tannins in a fresh tea leaf have a bitter taste, then after processing this bitterness disappears, and the tea acquires a pleasant astringency, which gives the main taste to the brewed infusion. It is unoxidized (natural) polyphenols that are responsible for the astringency of tea (in the drink they create the effect of astringency, a “viscous” sensation in the mouth, due to which the tea infusion stimulates the activity of the salivary glands and quenches thirst well). However, most tannins do not remain unchanged during the processing of tea raw materials. Their oxidation products, which occur during the factory production of tea (especially during fermentation), in turn cause the oxidation of other substances and form many of the components involved in creating the color, aroma and taste of tea. Oxidized polyphenols give tea its color and flavor. The higher the degree of oxidation, the more color and less astringency the tea has. The content of tannins in green teas is much higher than in fermented ones, since in green teas they are in an almost unoxidized state. In addition, usually all higher grade teas contain more tannins than lower grades.

4.3 Catechins(derivatives of flavan-3-ol) - natural biologically active substances from the group of bioflavonoids. Catechins and their oxidation products are ternary compounds containing carbon, hydrogen and oxygen. Carbohydrates are exposed to a number of enzymes, resulting in the formation of shikimic acid, which is a precursor to compounds with benzene rings. At the very end of this cycle of reactions, the synthesis of catechins occurs. These are colorless crystalline substances that dissolve well in water and alcohol, easily oxidize and enter into complex compounds with many other components. To date, 12 types of catechins have been found in tea, some of them belong to simple, or free, catechins, others belong to the category of esters (they have a tart, bitter-astringent taste; they account for 70-80% of the total content of catechins). The percentage of catechins decreases with the aging of the tea leaf and depends on the type of tea tree (there are more catechins in the leaves of large-leaved species than in small-leaved species). Most catechins are found in white tea, a little less in green tea. Tea contains four main types of catechins: epicatechin (epicatechin - EC, 5-10% of total catechins), epigallocatechin (epigallocatechin - EGC, 10-15%), epicatechin gallate (epicatechin gallate - ECG, 10-20%) and epigallocatechin gallate (epigallocatechin gallate - EGCG, 50-60%). Epillocatechin gallate (EGCG) is the most powerful of the four major catechins, and is 25 to 100 times more powerful in antioxidant activity than vitamins C and E.

It has been established that tea exhibits strong antioxidant properties due to the high content of catechins, especially epigallocatechin gallate (EGCG), which makes up 50-60% of the entire catechin group.

The quality of green tea depends on the concentration of catechins and their derivatives, since it is they that provide the formation of a strong, rich, long-lasting taste. The concentration of catechins decreases as the leaf ages, so among green teas, young teas harvested are the most highly valued. in early spring. In addition, studies have shown that polyphenols and their primary oxidation products affect the color range of the infusion and the aroma of green teas. So, for example, the primary oxidation products of catechins, the so-called orthoquinones, are yellow substances and give golden-yellow hues to the brewed infusion. Reacting with amino acids, orthoquinones form aromatic substances. Oxidative transformations of catechins also play an important role in tea fermentation. These substances largely determine the color, aroma and taste of tea. For example, the products of oxidative polymerization of catechins - theaflavin and thearubigin pigments - play a decisive role in the formation of a rich golden-amber color and taste of infusion in red teas.

As already mentioned, the antioxidant index of green tea extract is superior to that of vitamins C, E, as well as selenium and zinc. The antioxidant effect of tea catechins is closely related to their ability to scavenge free radicals. Thus, tea, and first of all, green tea, being a strong antioxidant, reduces the amount of free radicals in the human body, preventing the occurrence of cancer.

Tea catechins and, in particular, epigallocatechin gallate (EGCG), actively reduce the level of cholesterol and low-density lipoprotein (LDL) in the blood plasma. These substances are also extremely useful for strengthening the immune system (for example, epigallocatechin-3-gallate affects the lymphocytes that are responsible for the normal immune responses, so that the human immunodeficiency virus (HIV) cannot enter the cell and disrupt its function) . Catechins regulate the permeability of capillaries, increase their resistance, increasing the elasticity of the walls, and also contribute to a more efficient use of ascorbic acid by the body. Therefore, catechins are classified as substances with P-vitamin activity and are used in the treatment of diseases associated with impaired capillary function, edema of vascular origin, etc. Tea catechins have antimicrobial properties and are used in the treatment of dysentery.

4.4 Flavonols- one of the most common plant pigments (yellow crystals), some of them are highly soluble in hot water. Flavonols are fairly stable compounds, so they practically do not undergo changes during the processing of plant materials. A rough colorimetric estimate shows that the total content of flavonols is up to 6% of the total dry matter mass and 10-12% of the total content of tea polyphenols. Among the flavonols found in tea, the main glycosides are kaempferol (kaempferol), quercetin (quercetin), myricetin (myricetin), vitexin (vitexin), as well as traces of the corresponding aglycones - non-carbohydrate components of these glycosides. Flavonols are one of the most important groups of substances that have a direct impact on the properties of green teas (especially on the color scheme of the infusion, since flavonols are compounds that contain water-soluble substances of green and yellow color). Flavonols are substances of P-vitamin action. They reduce the permeability and increase the strength of blood capillaries, promote the absorption of vitamin C, participate in redox processes, and regulate the work of some endocrine glands (primarily the thyroid gland).

4.5 Anthocyanidins- substances formed as a result of the hydrolysis of anthocyanins (plant pigments) under the action of enzymes and acids. They have a different color - from pink to blue and purple. The main among them are cyanidin (cyanidin), delphinidin (delphinidin), incarnatine (incarnatin), etc. Anthocyanidins are unstable substances that are easily oxidized when heated, under the action of direct sunlight, peroxidase enzymes (peroloxidase) and phenoloxidase (phenoloxidase), therefore, their presence in fermented tea was not detected. Anthocyanidins give tea a bitter-tart taste.

Anthocyanidins help vitamin C to penetrate into the cells of the body, strengthen capillaries and joints. These substances are useful for restoring and maintaining vision, perfectly protect the body from the aggressive effects of free radicals and prevent the development of atherosclerosis, cancer, and hypertension.

4.6 Phenolic acids- cyclic (aromatic) acids, which contain both an acidic -COOH group and one or more -OH groups in the nucleus. The content of phenolic acids in tea is quite low, the main among them are gallic acid (3,4,5-trihydroxybenzoic acid (gallic acid, 3,4,5-trihydroxybenzoic acid)), theogallin (theogallin), chlorogenic acid (chlorogenic acid), caffeic acid (caffeic acid), ellagic acid (ellagic acid), (coumaric acid). Phenolic acids are present not only in green teas, but also in fermented teas.

Phenolic acids have astringent, choleretic, diuretic, capillary-strengthening and anti-inflammatory effects, regulate the function of the thyroid gland, and stimulate the antitoxic function of the liver.

Substances from the group of flavonoids are called "natural biological response modifiers" because of their ability to change the body's response to allergens, viruses and carcinogens. This is evidenced by their anti-inflammatory, anti-allergic, anti-viral and anti-carcinogenic properties. Flavonoids are strong antioxidants, have choleretic, antiulcer, diuretic, antispasmodic and other actions, participate in the body's immune reactions, affect lipid metabolism and enzyme activity.

5. Carbohydrates (saccharides (carbohydrates, saccharides)).

Carbohydrates are an extensive group of organic compounds, which include carbon, oxygen and hydrogen (general formula C m (H 2 O) n). They are part of all living organisms. Tea contains monosaccharides (monosaccharides), disaccharides (disaccharides) and polysaccharides (polysaccharides), they account for 20-25% of the mass of dry matter.

The role of carbohydrates in living organisms is extremely diverse. In the tea tree, monosaccharides are the primary products of photosynthesis and serve as initial compounds for the biosynthesis of various glycosides, polysaccharides, as well as substances of other classes (amino acids, fatty acids, polyphenols, etc.). Carbohydrates are also reserve substances (stored in the form of starch) and serve as an energy reserve for the life of the plant organism. In the form of glycosides, various metabolic products are transported. Numerous polysaccharides or more complex carbohydrate-containing polymers perform supporting functions in living organisms. So, for example, the rigid cell wall of the tea tree is built from cellulose and hemicelluloses. Pectin substances help to maintain the state of turgor in the tissues, increase the drought resistance of the plant.

Mono- and disaccharides (soluble sugars: sucrose (sucrose), glucose (glucose), fructose (fructose), maltose (maltose); 0.8-4%) are highly soluble in water and participate in the formation of the taste characteristics of tea. Most tea saccharides (more than 20%) belong to the group of polysaccharides, which includes starch (starch), fiber (cellulose (cellulose)), hemicellulose (hemicellulose), lignin (lignin). These substances are insoluble in water. The share of pectins (pectins), which are products of carbohydrate metabolism, accounts for about 4% of dry matter. Soluble pectin determines the degree of saturation of the tea infusion and the presence of a glossy sheen on the surface of dry tea leaves. In addition, pectins are of no small importance for maintaining the quality of tea, since its hygroscopicity is associated with them (pectic acid covers each tea leaf with a thin gelatin film that is poorly permeable to moisture). With a lack of pectin acid in tea, its hygroscopicity increases sharply, and, consequently, the tea spoils faster.

Almost all substances that have a beneficial effect on the quality of tea and underlie the formation of its color, aroma and taste properties are found in greater quantities in young tea than in old tea. That is why tea made from tender, young flushes is better than tea made from overripe raw materials. The high content of polysaccharides, on the contrary, indicates the old age (maturity) of tea, young tea contains a small amount of these components. Young buds and leaves are soft, flexible and plastic. They make thin and elegant or tightly twisted, heavy, as if poured, tea leaves, painted in rich colors and having a glossy sheen. Old leaves are coarse in texture and contain a lot of cellulose, as a result of which they produce low-grade tea, which consists of light, not very dense, slightly twisted tea leaves, similar to large, coarse flakes with a dull surface.

Carbohydrates make up a large (often major) part of the human diet. The biological role of carbohydrates for humans is determined by their energy value; these substances are used by the body either as a direct source of heat or as an energy reserve. Carbohydrates also perform supporting and structural functions. They are part of the cell membranes and subcellular formations. Carbohydrates are involved in defensive reactions organism (for example, viscous secretions secreted by various glands are rich in carbohydrates and their derivatives; they protect the walls of hollow organs (esophagus, intestines, stomach, bronchi) from mechanical damage, penetration of harmful bacteria and viruses). There is evidence that carbohydrate structures are also involved in such highly specific phenomena of cellular interaction as fertilization, "recognition" of cells during tissue differentiation and rejection of foreign tissue, etc.

The presence of a small amount of soluble sugars is one of the great benefits of tea, not only does it make tea an ideal anti-sclerotic drink, especially when combined with iodine and vitamin P, but also ensures that tea retains vitamin B, usually absorbed by sugars.

6. Organic acids.

Organic (carboxylic) acids are a class of organic compounds containing a carboxyl group -COOH; are formed as a result of biochemical processes in the cell sap of most plants. Tea contains quite a lot of different organic acids, while they account for only 3% of the dry matter mass. Most organic acids in tea are in a free state: malic acid (apple acid), citric acid (citric acid), succinic acid (succinic acid), oxalic acid (oxalic acid). In the process of processing vegetable raw materials in tea, palmitic acid (palmitic acid) and linoleic acid (linoleic acid) are also formed.

Organic acids play an important role in the metabolism of the tea plant, they are mainly products of the transformation of sugars, they take part in the biosynthesis of alkaloids, glycosides, amino acids and other biologically active compounds, they serve as a link between the individual stages of the metabolism of fats, proteins and carbohydrates.

Organic acids play an important role in the formation of tea aroma. To date, it is known that among the aromatic components of tea there are about 25 types of organic acids. Some of them are odorless by themselves, but become aromatic substances as a result of oxidation (for example, linoleic acid), others are good adsorbents of aromatic components (for example, palmitic acid).

Organic acids stimulate the secretion of juice in the gastrointestinal tract and thus improve digestion, regulate the state of the intestinal microflora, maintain a normal acid-base balance, activate intestinal motility, reducing the risk of developing many gastrointestinal and other diseases.

7. Lipids

Lipids are fat-like substances (derivatives of higher fatty acids, alcohols or aldehydes) that are part of all living cells and are responsible for the normal course of basic physiological processes. The main lipids that make up tea are: fats (fat), phospholipids (phospholipids), glycerides (glycerides) and glycolipids (glycolipides). They account for about 8% of dry matter.

Lipids are contained in the protoplasm of tea tree cells, and therefore they regulate the process of penetration of substances into cells (being one of the main components of biological membranes, they affect cell permeability). These substances affect the activity of many enzymes, participate in the formation of an energy reserve and the creation of protective water-repellent and thermal insulation covers in the plant body.

These compounds play a significant role in the formation of tea aroma.

In the human body, lipids are involved in the transmission of a nerve impulse, in muscle contraction, in the creation of intercellular contacts, in immunochemical processes, and protect various organs from mechanical influences. Fats play a special role in life processes. This is the main source of energy (the energy value of fats is more than two times higher than carbohydrates). In addition, fats, which are part of most cell membrane formations and subcellular organelles, perform important structural functions.

8. Pigments.

Pigments are colored substances that make up the tissues of living organisms. The color of pigments is determined by the presence in their molecules of the so-called chromophore groups, which determine the selective absorption of light in the visible part of the solar spectrum. The pigments that make up the tea (about 1% by weight of dry matter) determine the color of dry tea leaves, brewed infusion and leaves of sleeping tea. Tea pigments belong to two different groups: fat-soluble pigments and water-soluble pigments. Pigments from the first group do not dissolve in water, they include green chlorophyll (chlorophyll), yellow xanthophyll (xanthophyll), orange-yellow carotene (carotene). The group of water-soluble pigments includes flavonols, anthocyanidins, which have already been mentioned above, as well as the oxidation products of tea polyphenols - theaflavins (give a golden orange-yellow color and determine the brightness of the infusion; these compounds are formed as a result of the reaction of quinones, derivatives of simple catechins, with quinones, gallocatechin derivatives; continued fermentation reduces theaflavins, because they are rather unstable substances, undergo further oxidation and are converted into thearubigins), thearubigins (give reddish tones) and theabrownins (theabrownin) (give dark brown hues; are oxidation products of thearubigins; ( too dark color of the infusion indicates excessive formation of theabraunins, and therefore too strong fermentation.) For example, in the production of red tea, about 15% of tea catechins remain unchanged and about 10% are involved in the formation of theaflavin. The remaining 75% of catechins are converted into tearu bigins. The water extract of red tea contains approximately 2-6% of theaflavins (the main among them are four varieties: theaflavin (TF), theaflavin-3-gallate (theaflavin-3-gallate), theaflavin-3'-gallate (theaflavin-3'-gallate ) and theaflavin-3,3'-digallate (theaflavin-3,3'-digallate)) and more than 20% thearubigins.

Pigments play an important and diverse role in the life of the tea tree organism. The pigment system is a link that connects the light conditions of the external environment with the metabolism in the body. One of the most important functions of tea tree pigments (primarily chlorophyll) is their participation in photosynthesis. In addition, the absorption of light by pigments plays a role in the processes of plant growth and development. Many pigments (for example, carotenoids) protect the body from the harmful effects of ultraviolet radiation from the sun, and also play an important role in the transport of oxygen (that is, they are involved in respiration). Pigments determine the color of the tea tree, which is important for its adaptation to the external environment (in plants, color serves to attract pollinating insects and seed-dispersing birds).

Fat-soluble pigments are involved in the formation of the colors of dried tea leaves and leaves of sleeping tea. So, for example, the color of green teas depends not only on the total content of chlorophyll, but also on the percentage of chlorophyll a and chlorophyll b. Chlorophyll a is dark green and chlorophyll b is yellow-green. Young fresh flushes contain a fairly large amount of chlorophyll b, so dry tea leaves are distinguished by delicate light yellow hues or light green tones with pale yellow blotches and a rich glossy sheen. The color of the infusion of green teas is due to the presence of green chlorophyllin (chlorophyllin) - a derivative of chlorophyll, but also flavonols. When processing red teas during the fermentation process, chlorophyll is mostly destroyed. At this time, in the plant tissues of the tea leaf, black- Brown color, tea polyphenols are oxidized (polyphenoloxidase catalyzes the oxidation leading to polymerization of polyphenols), proteins combine with pectins and saccharides, resulting in red teas becoming red with brownish-brown hues or juicy blue-black tones. The color of dry tea leaves of red tea is due not only to the presence of oxidation products of polyphenolic compounds, but also to melanoids (melanoid) - brown substances, products of the so-called Maillard reaction (Maillard Reaction), during which the nitro groups of amino acids are combined with reducing sugars (carbohydrates). Thearubigins and orthoquinones react with proteins and form water-insoluble compounds that cause the color of the leaves of the tea. Thus, the color range of all types of tea is closely related to the percentage, composition and transformation of a particular pigment. In addition, pigments also affect the taste of red teas. For example, theaflavins give tea a pleasant, clean, refreshing and lively taste, increase the strength and intensity of the taste. Thearubigins make the drink rich, endow it with a thick long-playing taste with a strong tonic effect and astringent properties.

The pigments contained in tea have a beneficial effect on the human body. The pigments that are formed as a result of the oxidation of polyphenols are polymeric polyphenolic compounds, therefore they also have the beneficial properties of polyphenols and, first of all, antioxidant activity (in addition, these substances lower cholesterol levels, prevent the development of cardiovascular and cancerous diseases, stimulate the immune system). systems, promote weight loss, etc.).

Scientists from leading medical centers different countries in last years opened new medicinal properties chlorophyll, as a fighter against infectious and even cancerous diseases. This pigment has a strong antibacterial effect and has a stimulating effect on various organs and systems: cardiovascular, pulmonary, gastrointestinal, kidneys, etc.

Xanthophyll and carotene belong to the group of carotenoids. Carotenoids have a powerful antioxidant effect, due to which they neutralize the harmful effects of free radicals (xanthophyll slows down the aging process and the development of cancerous tumors). Carotenoids improve the functioning of the immune and reproductive systems. Carotenoids are especially useful for the prevention of cataracts and other eye diseases (eg, age-related macular degeneration (AMD)).

9. Aromatic substances (essential oils (aromatic (fragrant) substance, essential oils)).

The term "aromatic substances" serves as a general name for the volatile substances that make up the composition of tea and directly determine its quality. Essential oils are fragrant (odorous), easily volatile substances contained in various parts of plants, mainly in flowers, leaves, fruits.

Although these components account for a very small percentage of the total chemical composition (0.02% - in fresh flushes (that is, to obtain 100 g of essential oils in their pure form, more than 500 kg of tea leaves must be processed), 0.005-0.02% - in green teas, 0.01-0.03% - in red teas), they are very diverse. According to the results of scientific analysis, tea can contain more than 300 different aromatic compounds: there are about 50 in fresh flushes, more than 100 in green teas, and over 300 in red tea varieties. Essential oils are a multi-component mixture of organic compounds. The main components of tea aromatic substances are: alcohols (alcohol), phenols (phenol), aldehydes (aldehyde), ketones (ketone), acids (acid), esters (ester), lactones (lactone), nitrogenous compounds (nitrogenous compounds), sulfo compounds (sulfocompounds), hydrocarbons (hydrocarbon) (mainly terpenes), oxides (oxides (oxide)) etc.

The aroma of finished tea is determined by the composition and concentration of aromatic substances in freshly picked raw materials. The percentage and composition of aromatic compounds in tea depend on the season of the year, the type of tea tree, the degree of maturity of the raw materials, and the place of growth. As a rule, there are more aromatic substances in spring tea than in summer and autumn, in young tea - more than in mature tea. Tea made from young, tender flushes has a pronounced soft fragrance (pekoe flavor), which carries shades of lively freshness. In each individual area, tea develops its own special aromatic palette. For example, red tea from Qimen County (Anhui Province) has a characteristic honey aroma, and highland green teas often have the smell of ripe chestnut.

Resinous substances (resin alcohols, resin acids, resin phenols and other organic compounds) act as carriers and fixatives of tea aroma.

During the processing of tea, most of the essential oils (about 70-80%) are lost, but at the same time, during the technological procedures, new components appear that give the tea a characteristic aroma (for example, many researchers have experimentally observed that aldehydes are formed during the reaction amino acids with both sugars and tannins; the characteristic aromatic components of red teas arise from the oxidation of carotene). This may explain the diversity of aromatic properties. various kinds tea (since they have undergone different processing).

The aromatic substances of fresh, unprocessed tea leaves are mainly represented by alcohol and aldehyde compounds. For example, cis-3-hexenol (“leaf alcohol” (cis-3-hexenol, leaf alcohol)) has a low boiling point and an intense herbal smell of fresh greens. Linalool, as well as phenethyl alcohol, have a high boiling point and are distinguished by a delicate, fresh aroma or a slight floral scent. Ready-made green teas contain a fairly large amount of hydrocarbons, alcohol and pyrazine (pyrazine) aromatic compounds (they give the tea a very refined and delicate, clean and fresh, soft and delicate aroma). The latter of them are mostly formed in the process of hot drying and roasting of vegetable raw materials. Semi-fermented teas (oolongs) contain a large amount of aromatic aldehydes, which take an active part in the formation of a tea bouquet. In red teas, alcohol, aldehyde, ketone and ether aromatic compounds are mainly represented (they give the tea a strong and persistent sweet aroma). Most of them are formed during the processing of red tea as a result of oxidative reactions.

Essential oils have a wide range of therapeutic and prophylactic properties. However, the most significant is their ability to influence the central nervous system. These substances stimulate the nervous system, relieve stress, emotional excitability, increase efficiency.

10. Vitamins (vitamins).

Vitamins are a group of organic compounds of diverse chemical nature. Tea is rich in various vitamins, these substances account for 0.6-1% of the dry matter mass. Vitamins are water-soluble and fat-soluble. Fat-soluble vitamins in tea include vitamins A (the largest amount), D, E, K. However, these substances do not dissolve in water, so they are not extracted in the brewed infusion. The group of water-soluble vitamins includes vitamins C, B 1 , B 2 , B 3 , B 5 , B 11 , P, inositol (inosite). Most of all in tea, and especially in high-grade elite green teas (100 g - about 250 mg (maximum - 500 mg)) contains vitamin C (in terms of vitamin C content, green tea is comparable to citrus crops, although this content decreases during the fermentation process). ). Thus, along with green teas, a person receives nutrients that are of great importance for normal metabolism and life.

The physiological functions of vitamins in the life of organisms (both plant and animal) are very significant. Vitamins are either part of enzymes or are components of enzymatic reactions and therefore play a huge role in metabolism. Vitamins are involved not only in the processes of decomposition of substances and the release of the energy contained in them, but also in the processes of synthesis and the construction of body structures.

All water-soluble vitamins of tea, which are extracted in the brewed infusion, have a beneficial effect on human health:

Vitamin C (ascorbic acid) - a powerful antioxidant, participates in all types of metabolism, ensures normal permeability of the walls of capillary vessels, increases their strength and elasticity, participates in the synthesis of hormones, helps strengthen bone tissue, increases the body's resistance to adverse effects promotes regeneration.

Vitamin B 1 (thiamine (thiamine)) is involved in carbohydrate metabolism and associated energy, fat, protein, water-salt metabolism, has a regulatory effect on the activity of the nervous system, protects the body from the damaging effects of aging, alcohol and tobacco, regulates the activity of the glands internal secretion.

Vitamin B 2 (riboflavin (riboflavin)) is necessary for the formation of red blood cells and antibodies, for cell respiration and growth, improves skin condition, has a positive effect on the liver, organ of vision and mucous membranes of the digestive tract.

Vitamin B 3 (vitamin PP, nicotinic acid) normalizes blood cholesterol and liver function, regulates redox processes in the body.

Vitamin B 5 (pantothenic acid (pantothenic acid)) - anti-allergic vitamin, normalizes lipid metabolism, stimulates the production of adrenal hormones, due to which it is powerful tool for the treatment of diseases such as arthritis, colitis, allergies and heart disease.

Vitamin B 11 (carnitine) plays a decisive role in the metabolism of fats, helps to cleanse the body, and supports the function of the cardiovascular system.

Vitamin P (rutin (rutin)) - a group of flavonoid compounds that maintain the impermeability of capillary walls, reduce their fragility, protect ascorbic acid and adrenaline from oxidation, promote the accumulation and absorption of vitamin C. Tea catechins enhance the effect of vitamin P. The highest P-vitamin activity has green tea. Drinking 3-4 glasses of good strength tea, we provide our body with a daily preventive dose of vitamin P.

Inositol is involved in the metabolism of fats and cholesterol, has a calming effect.

11. Fermentation

Enzymes (enzymes, enzymes).

The most important difference between teas is the degree of their fermentation: so teas can be post-fermented (black tea), fermented (red tea), unfermented (green tea), slightly fermented (white tea, yellow tea) and semi-fermented (oolong tea).

Enzymes are specific protein catalysts that are involved in a number of biochemical reactions that take place during the life of the tea tree and during tea processing. The composition of tea (usually in an insoluble, bound state) includes a variety of enzymes: oxidoreductase (oxidoreductase; the main among them are polyphenoloxidase (polyphenoloxidase), peroxidase (peroxidase) and catalase (catalase)), hydrolase (hydrolase), lyase (lyase) , phosphorylase (phosphorylase), transferase (transferase), isomerase (isomerase).

Almost all biochemical reactions that occur in any organism (both plant and animal) and, in their natural combination, the constituents of its metabolism, are catalyzed by the corresponding enzymes. Thus, by directing and regulating metabolism, enzymes play a crucial role in all life processes.

The action of enzymes depends on a number of factors, primarily on the temperature of the environment. For each enzyme, the temperature optimum of action is determined: as a rule, enzymes show the greatest activity in the range of 30-50ºC. The decrease in the intensity of the action of enzymes with increasing and decreasing temperatures compared to the optimal one is explained by the beginning destruction of the protein that is part of the enzymes (the protein part of the enzyme (apoenzyme) is characterized by the usual properties of proteins - instability to heat and low temperatures). Inactivation and denaturation (change in the structure and natural properties) of enzymes leads to a loss of catalytic ability.

The catalytic action of the enzyme is strictly specific and differentiated (depending on the structure of the substrate on which the enzyme acts). For example, polyphenol oxidase can only catalyze the oxidation reaction of tea polyphenols with the formation (as a result of polymerization) of theaflavins, thearubigins and theabraunins. Proteases (protease) accelerate only the reaction of hydrolysis (cleavage) of proteins with the formation of amino acids. This feature of enzymes is just used in the processing of tea raw materials. By regulating the action of enzymes, suppressing or, conversely, enhancing their activity with the help of technological methods, it is possible to cause certain reactions, as a result of which each type of tea will acquire the necessary, only its inherent properties. So, for example, when processing green teas, a special roasting procedure is used (“sha-qing” - “getting rid of greens” (de-enzyming)). At high temperatures, the activity of enzymes is suppressed, which in a fairly short time leads to the inhibition of a number of chemical transformations and, as a result, contributes to the formation distinctive features this type of tea. Red teas belong to the category of fermented teas, in which the process of enzymatic oxidation has passed most fully. As a result of enzymatic oxidation polymerization (enzymatic oxidation polymerization) of tea polyphenols (mainly catechins) - a process caused by the action of enzymes, as well as a number of other transformations, three types of colored substances appear in the composition of the tea leaf - yellow theaflavin, red thearubigin and brown pigment TB . Due to the course of these reactions, red tea acquires one of its distinctive features - its infusion turns out to be clean and transparent, with a glossy sheen, the brewed drink turns into rich and bright red hues, and a golden rim becomes noticeable around the edges of the cup (bright, red brilliant) . Oxidative polymerization of tea polyphenols is accompanied by the formation and changes of various aromatic components. The increase in the amount of aromatic substances is especially intense and fast during fermentation, which is why the degree of fermentation of red tea affects not only the color and taste properties of the brewed infusion, but is also of great importance for the process of forming the aromatic bouquet of this type of tea.

Particular attention in discussing the importance of enzymes in tea production should be given to black post-fermented Pu-erh teas. In the process of processing Puer tea, a specific procedure for wetting plant materials in heaps is used. At this stage, microorganisms are naturally born in the nutrient medium (currently, the method of artificial seeding of dominant species of mold fungi and bacteria is also used), due to which a number of complex biochemical reactions occur in the tissues of the tea flush. So, for example, the so-called " black mold”(scientific name Aspergillus Black (Aspergillus niger)), namely enzymes and organic acids, which are metabolic products of this type of microorganism. Aspergillus niger is able to secrete both intracellular (endoenzymes - endoenzyme, cell-bound enzyme) and extracellular enzymes (exoenzymes - exoenzyme, cell-free enzyme). Among these enzymes, there are about 20 varieties of hydrolases (enzymes that catalyze hydrolysis reactions), for example, glucoamylase (glucoamylase, amyloglucosidase), cellulase (cellulase) and pectinase (pectinase). Polysaccharides, fats, proteins, natural fibers, pectin, insoluble compounds, and other organic substances undergo hydrolysis. Most hydrolysis products are monosaccharides, amino acids, hydrated pectin, and soluble carbohydrates. The hydrolysis reaction contributes to a more efficient release and diffusion of useful active components contained in the tissues of the tea leaf. Thanks to such chemical transformations, the taste qualities of tea infusion are enhanced, the drink acquires an intolerant, clean and rich taste, carrying a pleasant sweetish aftertaste.

12. Inorganic (mineral) compounds.

Minerals account for 3.5-7.0% of the total dry matter mass. Inorganic compounds are divided into two groups - soluble in water (2-4%) and insoluble in water (1.5-3%). Under the influence of high temperatures, these compounds turn into "ash" (ash), while about 50-60% of this ash is water-soluble (water-soluble ash). In young tea, most of the ash is water soluble. The content of total ash (total ash) is one of the mandatory parameters when checking the quality of exported tea (as a rule, the total ash content should not exceed 6.5%).

Many minerals are part of complex compounds, but, being in a colloidal state, can be dissolved in water, released into tea infusion, increasing the nutritional value of the drink, and can have a beneficial effect on the human body. Tea is a natural complex of mineral elements that are actively involved in the formation of other substances, presented in an optimal combination and easily digestible form. There are about 27 different mineral elements in tea, the main ones are presented in the table:

Element name	Quantity (with daily consumption of 10 g of tea)	Therapeutic properties
	Daily requirement (adults): 2.0-3.0 g	Helps regulate the water-salt balance in the body. It contributes to the normal functioning of muscles (participates in muscle contraction) and the nervous system (together with magnesium, it alleviates the course of diseases, restores energy in people suffering from weakness, insomnia, headaches). Normalizes the activity of the cardiovascular system.
Magnesium (Mg)	Daily requirement (adults): approximately 4.5 mg per 1 kg of body weight	It is necessary in all major biological processes of the body, as it activates enzymes (for example, it supports the normal metabolism of carbohydrates). Maintains muscle tone, stimulates their work, increases the ability of cells to absorb oxygen. Strengthens the nervous system, is a natural tranquilizer. Prevents the development of heart disease. Participates in bone formation (necessary to strengthen the skeleton). Stimulates the motor activity of the intestines and gallbladder.
Manganese (Mn)	Daily requirement (adults): 2.5-7.0 mg	Participates in all types of metabolism, playing an important role in activating the function of many enzymes. It is of particular importance in the implementation of the function of the sex glands, the musculoskeletal system, and the nervous system.
	Daily requirement (adults): 2.0-4.0 mg	Prevents the development of caries (promotes the restoration of enamel and reduces the penetration into the tissues of the tooth, slowing down the action of microorganisms of soft plaque, facilitates the process of enamel remineralization, has an antibacterial effect). Promotes bone formation. Stimulates immune responses.
Calcium (Ca)	Daily requirement (adults): 800-1000 mg	It is the main structural element of bone tissue. Participates in the processes of excitability of the nervous tissue, muscle contractility. - Plays a role in all stages of blood coagulation. Essential for the normal functioning of the immune system. - Participates in the work of many enzyme systems. Promotes the excretion of salts of heavy metals and radionuclides from the body, has anti-allergic and anti-inflammatory effects.
Sodium (Na)	Daily requirement (adults): 4.0-6.0 g	Regulates the movement of substances in and out of each cell. Participates in water-salt metabolism and in maintaining the acid-base balance in the body.
	Daily requirement (adults): 500-1000 mg	It is a structural component of most proteins, including enzymes. Together with B vitamins, it is involved in metabolism. It is anti-allergenic.
Iron (Fe)	Daily requirement (adults): 10-15 mg	It plays an important role in hematopoietic function, it is necessary for the synthesis of a key protein in red blood cells - hemoglobin. It is a mandatory and indispensable component of various proteins, is part of a number of enzymes - catalysts for redox processes. Supports high level body's immune resistance.
	Daily requirement (adults): 1.0-5.0 mg	Participates in redox processes, supporting many enzymes, affecting the activity of certain hormones and vitamins. Participates in hematopoiesis and a large number of metabolic reactions. Enhances the regenerative capacity of tissues. Prevents cancer. Stimulates the immune system.
Nickel (Ni)	Daily requirement (adults): 60 µmol	It has an indirect effect on the body through the microflora and enzymes of the digestive tract. Takes a direct part in the metabolism. Takes part in the synthesis and functioning of the main components of DNA, RNA, protein.
Silicon (Si)	Daily requirement (adults): 20-30 mg	Necessary for the formation of the basic substance of bone and cartilage, is directly involved in the process of mineralization of bone tissue. Actively participates in the work of the blood coagulation system. - Necessary for the construction of epithelial and nerve cells.
	Daily requirement (adults): 10-20 mg	It is a part of many enzymes, affects redox processes, catalyzes energy processes in the cell. Stimulates growth and development. It helps to reduce the deposition of cholesterol on the walls of blood vessels. - Used by the body to produce its own antioxidants. Provides normal visual function.
	minimal amount Daily requirement (adults): 50-70 mcg	It is an important component of the body's antioxidant system. Prevents the development of cancer. It is a cofactor in a number of redox enzymes Stimulates the formation of antibodies and thereby increases the body's defense against infectious and colds. Promotes the removal of radionuclides and mercury from the body.

The composition of the finished tea includes various compounds that determine its aroma, color and tonic properties:

Tannins (phenolic) substances;

Caffeine 2-4%;

Vitamins - B1, B 2, P, PP, C;

pantocrinic acid;

Essential oils;

Minerals (potassium, calcium, phosphorus, magnesium, etc.).

During processing, water is removed from the tea leaf, the content of which is reduced to 3-7%, and therefore, the dry matter content in the finished dry tea is 93-97%. More than 300 compounds are included in tea.

One of the important indicators of the value of tea is the content of extractive substances in the water, which in the finished green tea is 40-50%, and in black - 30-45%.

The most important component of tea is a complex of phenolic compounds (tea tannin), consisting of catechins and their gallic esters. Long leaf green tea is the richest in them.

Phenolic compounds and their condensation product give tea thirst-quenching properties, tart, pleasantly astringent taste and beautiful color. Tea tannin has a high P-vitamin activity, contributes to a better perception of vitamin C by the body, enhances its resistance to infectious diseases. Catechins prevent hemorrhages, as they strengthen the walls of blood vessels, have antioxidant properties, and anti-radiation effects. Tannins are one of the components of the tea leaf. According to the ability to dissolve in water, tannins (phenolic) substances are divided into water-soluble and water-insoluble. In shaping the quality of finished tea, water-soluble tannins, which are rich in young leaves and buds, are of great importance.

Tea contains the most caffeine - from 2 to 4% of dry weight. More caffeine accumulates in the second flush leaf. During the processing of tea, a significant part of the caffeine forms caffeine tanate (oxytheaniate) with tannin, which has a pleasant taste without the bitterness inherent in both initial components and has a milder effect on the human body than a pure caffeine preparation. This compound causes the tea beverage to become cloudy as it cools, which is a sign of high quality tea. When heated, the haze disappears.

Protein substances make up from 24.9 to 29.1% of dry matter. Their decay products - amino acids - play an indispensable role in the formation of the aroma of tea, especially black. But, on the other hand, reacting with tannins, they form insoluble compounds, thereby reducing the content of extractives.

Of the carbohydrates in the tea leaf, sucrose, starch, and fiber were found. The average content of soluble sugars in the finished tea is 3-4.7%, and fiber and hemicelluloses - 7.9-16.8%. The transformation products of these carbohydrates are involved in the formation and coloring of tea.

Pectin substances (from 2 to 3% of dry weight), which are much more in young leaves than in old ones, contribute to the adhesion of the leaf during the curling period and impart hygroscopicity.

Resinous substances influence the formation of the taste and aroma of tea.

Mineral (ash) substances are mainly represented by oxides of potassium, phosphorus, calcium, magnesium.

The intensity and tone of the color of tea are associated with the coloring substances in it.

The tea leaf contains a wide variety of enzymes that oxidize tannins.

The vitamin value of tea is determined by the content of vitamins C, B 2 , PP, etc. There are more vitamins in green tea than in black tea.

The energy value of black tea is 109 kcal (456 kJ) per 100 g.

Tea is a real pantry of biologically active substances. The most important of them is the alkaloid caffeine, which has a tonic effect, stimulates the activity of the nervous system and increases mental performance. Caffeine stimulates heart activity, favorably affects kidney function and promotes normal digestion. An increased amount of caffeine can also have an adverse effect on the body. There are no direct indications for the exclusion of tea from the diet, however, the restriction of tea consumption is often required not so much because of caffeine, but because of the restriction of fluid intake. This is required in violation of cardiac activity, with excess weight, in old age. Doctors believe that the amount of tea should be limited in advanced atherosclerosis and hypertension, and strong tea in these cases should not be drunk at all. This is especially true for people suffering from gastritis.

volume with high acidity and peptic ulcer, since strong tea concentrates oxalic acid, which irritates the gastric mucosa.

Theobromine and theofimine alkaloids are contained in small amounts and complement the tonic effect of caffeine.

Tannins give the tea a tart, astringent taste and a wonderful golden color.

All tannins with iron oxide ions form black substances. This oxidation property of tea with ferric iron is used in the production of artificial black caviar. Therefore, tea should not be brewed in oxidizing iron dishes or in water containing iron (“rusty”).

The color of tea catechins (tannins) becomes lighter in an acidic environment. This property explains the fact that when lemon is added to tea, it brightens.

Tannins are highly soluble in hot water and poorly in cold water. Therefore, when strong tea leaves are cooled, they precipitate, and the tea leaves become cloudy. If it is heated again, it becomes transparent again. If the brew does not become cloudy when cooled, it means that it is weak.

The more we love a product, the more myths we create about it. This rule has not bypassed tea - about its properties, useful and harmful, we still argue. On the one hand, in our arsenal Scientific research, on the other - popular opinions and prejudices, on the third, finally, our own experience, you can’t discount it either ...

Useful properties of tea ... black and green

Black and green tea is drinks, "collected" not from different bushes, as many people think, but from the same - tea. Both the one and the other are TEA, just processed differently. Green tea practically does not undergo fermentation (oxidation processes), therefore, unlike black tea, it contains more “natural” substances - extractive (soluble) ones, first of all.

In other words, at least one shrub plant, but two products that differ quite a lot in taste and chemical composition. And in terms of usefulness, by the way, too - green tea is healthier than black.

As for the taste, green tea is recognizable as a grassy note, somewhat tart, sweetish and fresh. Black tea is heavier, deeper and literally saturated with astringency, its aroma has floral and honey notes. However, neither one nor the other, if they are of good quality, never bitter, bitterness is the lot of low-quality, "left" non-format. More about the well-known differences: green tea is light in color, in all the richness of yellow and greenish hues; black tea is a warm and dark palette, from orange to red and brown.

Useful properties of tea - in its chemical composition

Do you know how long people have been researching the composition of tea? About 200 years old. But there is still no complete clarity, and not all of its ingredients are known and even discovered. The most important thing, however, we know. For example, it is clear that tea is the most complex chemical plant, consisting of at least 130 substances. From 30 to 50% - the so-called extractive, that is, soluble in water, they are more in green tea (up to 50%) and young, less in black (up to 40) and old.

What substances are included in the chemical composition of tea

Tannins (tannin, catechins, polyphenols), vitamins
Tannins make up from 15 to 30% of the composition of tea, in total there are at least 30 of them. Tea owes its main, tart taste to them, and in particular tannin. There is more tannin in green tea, almost twice as much as in black tea, and it is not oxidized in it, while up to 50% of the tannin contained in black tea is fermented. This substance makes tea sharper in taste, more "tea", or something. By the way, there is less of it in Chinese tea than in Indian and Ceylon.

Tannins have powerful bactericidal, hemostatic, wound healing, anti-inflammatory and astringent properties - strongly brewed tea can disinfect no weaker than 1% carbolic acid. Even more powerful is green tea: if you stand it for two days, you won’t need to go to the pharmacy if you have wounds.

Polyphenols
When talking about the beneficial properties of tea, they primarily mean polyphenols. Most of all vitamin P is in the form of tannin and catechin, according to the content of which tea is the leader among plant crops. Vitamin P, which is not produced by the human body, is flavonoids - substances responsible for vascular permeability.

In addition, vitamin P:

• normalizes blood pressure
• has a pronounced anti-edematous and anti-allergic effect
• stimulates the adrenal cortex, thereby increasing the synthesis of glucocorticoids
• useful in rheumatic heart disease and scurvy
• improve digestion

The above is not a complete list of the positive properties of vitamin P.

Especially a lot of catechins and polyphenols in green tea, it is no coincidence that it is considered more valuable.

In addition to P, tea contains a lot of other vitamins - C, B1, B2, K, PP, pantothenic acid. Together they form a biologically active complex. Interestingly, green tea contains 10 times more vitamin C than black tea.

(This is very good, including for pregnant women, but you also need to be aware of the problems that green tea creates. In particular for folic acid - see - these problems are significant).

The beneficial properties of tea, the polyphenols it contains, directly depend on the art of brewing tea and its storage.

It is known, for example, that “rusty” welding is obtained in iron utensils - an unpleasant brown color. This is how tea reacts to iron. The Chinese have been actively and for a long time experimenting with the material of teapots - their finest porcelain vessels were created not only for the sake of beauty. - not only a beautiful art, but a condition under which the beneficial properties of tea are fully revealed.

By the way, the amount of polyphenols can be checked as follows: if after cooling the drink it becomes cloudy, then everything is in order, since polyphenols dissolve sufficiently only in hot water.

Benefits of lemon tea

Polyphenols also actively react to acids. Lemon, for example, brightens tea and adds new properties to it. First of all, lemon in tea enhances all the beneficial properties of the tea itself. And besides, it is an excellent remedy for colds, a defender of immunity.

Polyphenols are natural antioxidants

It is known that antioxidants are very important, even vital for humans. In particular, these substances are believed to protect cells from the aggression of free radicals and thereby prevent cancer and cardiovascular disease. There was even a time of active fashion for the use of biologically active antioxidant supplements. BUT! There are different points of view about the usefulness of "man-made", in the form of dietary supplements, antioxidants. At the same time, all researchers agree that these substances, being in the products in a natural way, are absolutely necessary.

Antioxidants are especially abundant in green tea. Everyone can appreciate their beneficial effects “with their own eyes”: in case of poisoning with poor-quality food or excessive alcohol consumption, green tea will quickly put you in order.

Essential oils

In fact, there are very few essential oils in tea, only 0.08%, but the unique aroma of the drink, its “spirit” depends on their content and quality. Different types of tea have different composition of essential oils. Among them are those that give tea the smell of roses, vanilla and honey, lilac, cinnamon and citrus. Tea connoisseurs taste these delicate aromas and determine the elitism and dignity of the variety by the bouquet.

Most essential oils are found in the so-called oolongs - red teas, so they are often mixed with black varieties. Conversely, green tea aldehydes are in a bound state and do not participate in the formation of aroma. In this case, the aroma is formed mainly due to tannin.

What are essential oils? These are exclusively volatile substances - aromatic carbohydrates, aldehydes, phenols, complex acids like salicylic. They evaporate even with slight temperature rises, as well as improper storage and brewing. Whether our tea will be fragrant depends to a large extent on ourselves. The beneficial properties of tea practically do not depend on volatile substances, but essential oils affect the receptors of our senses, and if we enjoy the aroma, the benefits to our health are obvious.

Alkaloids - caffeine and others

The most famous alkaloid found in tea is caffeine, or theine (= caffeine, which is found in tea). Few people know what caffeine is in its “pure” form, so to speak. Caffeine is a bitter, colorless and odorless substance. It is contained, in addition to tea, in coffee, cola nuts, cocoa, mate and a number of other plants from the Tropics.

Can caffeine be called an unhealthy ingredient, or is it one of the health benefits of tea?

Contrary to popular myth, it is the chemical composition of tea, and not coffee, that contains more caffeine (1-4%), but tea caffeine (theine) is softer than coffee and is not so harsh in relation to the nervous and cardiovascular systems. In addition, tea caffeine does not accumulate in the body, it is impossible to “overdrink” it.

What you need to know about tea caffeine Even the British tea drinkers, who consume the most tea in the world, have an average of 0.3 grams of tea caffeine per day, or about 100 grams per year - this is very little. In Russia, tea is not consumed so actively, somewhere in the 20th part of the English norm - we take a microscopic dose of caffeine, less than 0.01 g. At the same time, the stimulating dose of caffeine per day, which pharmacologists allow, is 30-40 times more.

IN different varieties teas varying amounts of caffeine. It is more in elite varieties, less in young leaves, green tea. The strongest tea varieties can contain 5% caffeine. At the same time, it is not thein that provides tea with a fortress. And, in particular, Ceylon, known for its strength, contains less caffeine than Indian. There are also completely decaffeinated teas, which is especially important for nursing or pregnant women.

Caffeine- a great brain stimulant, and in moderation it is completely harmless in diseases of the heart and blood vessels.

Caffeine is far from the only alkaloid that is part of tea. It also contains soluble theophylline And theobromine- excellent diuretics and vasodilators, as well as several more insoluble ones, including those with negative effects and therefore not significant for humans.

Proteins and amino acids

You will be surprised if you do not already know: in terms of nutritional value, which is determined by the content of proteins, the tea leaf is comparable to legumes. Japanese green tea is especially rich in this respect. And its quality does not suffer from this (which cannot be said about black tea, especially if there is little tannin in it). For those interested in chemistry: in tea, proteins are mainly represented by glutelins (such proteins are soluble in alkalis), and to a lesser extent by water-soluble albumins. There are more of the latter just in green tea, so it is more nutritious - it saturates better.

There are 17 amino acids in tea! Among them, a special place is occupied by an important for human life glutamic acid, known for its beneficial effect on the depleted nervous system.

Proteins make tea nutritious. Proteins + amino acids are responsible for metabolism.

Pigments

Pigments have nothing to do with the beneficial properties of tea, but without them it is impossible to imagine its "design", aesthetics. The beauty of tea coloring depends on what pigments are included in chemical composition of tea. The variety and richness of tea coloring delight: from light golden and greenish to deep olive, red-brown, brown - tea is beautiful in its color!

The drink owes its color not to tannins at all, as it was once thought, but chlorophyll(found in green tea) xanthophyll(more than 50 shades) and carotene(the same that is contained in carrots), present mainly in black teas. There are a huge number of combinations of these pigments!

Also, chromaticity is associated with coloring substances. thearubigins (red-brown palette) and theaflavins (golden-yellow palette). It is believed that theaflavins are an excellent criterion for determining the quality of tea. They should be at least 25%, they give the drink brightness and lively tone, and their deficiency can be easily identified by an inexpressive, opaque brown tone.

Minerals and organic acids

There are few of them in tea - no more than 7%. These are metals such as iron, manganese, magnesium, sodium, silicon, calcium and potassium. Tea also contains trace elements of iodine, fluorine, phosphorus, copper, gold and some others. All of them are in tea in a water-soluble state. Thus, their properties turn out to be active - in particular, iodine and fluorine have their anti-sclerotic effect, magnesium and potassium are also indispensable for cores and hypertensive patients and good for the nervous system. And the higher the quality of tea, the more minerals they contain, especially potassium and phosphorus.

In a small amount, tea contains resinous substances (they fix the tea aroma) and useful organic acids - citric, oxalic, pyruvic, malic, succinic. This chemical composition of tea makes it a product of high dietary and nutritional value.

Substances of interest to the manufacturer + useful properties of tea

These are insoluble substances that are not of great importance to the consumer, but are important in the production of tea. This enzymes, pectins, carbohydrates and glycosides. They are significant for all kinds of reactions that occur during the harvesting and production of tea. Thanks to them, we get a delicious variety of this product, but from a nutritional point of view, they are of little value.

Pectins

However, not everything is clear-cut here either. For example, pectins. If the tea is of good quality, then the pectins that it contains are predominantly water-soluble, which means they are absorbed by humans. Meanwhile, it is known that pectins useful for the human gastrointestinal system.

Carbohydrates

Or are carbohydrates sugars and polysaccharides. Moreover, useless or harmful carbohydrates, fortunately, are insoluble, while good ones (glucose, fructose, maltose) are soluble. This remarkable property, together with vitamin P and iodine, allows tea to be an exceptional anti-sclerotic drink, preserving, among other things, vitamin B1 from being absorbed by sugars.

Tea is a real chemical warehouse. Moreover, a warehouse with a constantly changing assortment, so to speak. The chemical composition of tea changes - at all stages of its transformation from a plant into a sip of genuine pleasure.

Tea is unique, the beneficial properties of tea are a real gift of nature to man. It is unlikely that there will be another product that can synthesize such different substances and dissolve the most useful of them.

What myths about tea have not been confirmed

• tea is bad for heart disease
• strong infusion of the drink creates problems for the gastrointestinal tract
• tea is a mild addictive drug
• tea spoils the color and structure of the skin of the face
• causes insomnia
• creates physical weakness
• weakens vision
• leads to urinary incontinence
• causes dizziness
• it is better to drink weak tea

So, all these ideas have no basis. We will return to the question of the dangers of tea. And now let's consider a more pleasant question - about the benefits of tea.

What is known for sure about the beneficial properties of tea? (conclusions)

Tea is a biologically active product with a huge number of health benefits.

Tea is a tonic drink that charges a person with cheerfulness, energy and good mood. It is indispensable for all states of weakness, loss of strength, low pressure, depression. Yes, it does contain the alkaloid caffeine, but its effect on blood vessels and the heart is mild, and it is quickly excreted from the body.

Relieves fatigue, headache.

Tea is a nutritious drink that perfectly satisfies hunger, one of the beneficial properties of tea is that you can even lose weight on it!

Paradoxically, it helps not only with hypotension, but also with hypertension, contributing to vasodilation.

Normalizes metabolism, metabolism, protects against self-oxidation of fats, promotes their digestion.

Removes poisons from the body, helps with alcohol and drug poisoning.

Good for teeth as it contains fluoride.

It has a pronounced anti-atherosclerotic property. It is beneficial for high "bad" cholesterol.

Tea prolongs life.

The harm of tea - it turns out that it still exists ...

"After all of the above?" - you will be surprised. Alas, what is an extremely useful property of tea often brings harm.

Tannins, if consumed in large quantities, bind vitamins, not only those that come with tea, but also those that come with other products.

A large amount of drink is a big load on the blood vessels, which increases the heartbeat, pressure and excites the nervous system.

It is better not to get carried away with tea with increased anxiety, during a period of stress and “loose nerves”.

With exacerbations of diseases of the gastrointestinal tract, you should limit yourself to drinking strong tea, as it increases acidity.

The conclusion is simple - tea (as, indeed, everything in life) is good in moderation. As long as we drink it with pleasure, we get benefits. As soon as we start consuming just like that, from “nothing to do”, it definitely becomes harmful. Another thing is that everyone's vessels are different, so the norm will be different for everyone.

Get yourself such a criterion for evaluating the benefits or harms of tea: do you like it? Gives pleasure? Do you feel this delicious taste and aroma? Great, the tea did you good. The feeling of fatigue or even “tastelessness” indicates that it is time to stop - tea, alas, is already harmful. Specifically for you and specifically now.

Recommendations for tea lovers who want to reduce the harm of tea

These recommendations may be of interest to people suffering from cardiovascular diseases, as well as those who experience problems with the nervous system, but love tea very much and are not ready to give it up. The Chinese, in particular, give such advice:

• do not drink tea on an empty stomach
• don't drink it cold or too hot
• brew tea correctly, but no more than four times
• never drink tea before meals and immediately after
• drink only the tea that was brewed today
• do not take medicine with tea
• strong, properly brewed tea is preferable to weak tea
• if strong tea makes you feel a heartbeat and your blood pressure rises, add some milk to the drink

The main thing: tea gives us pleasure, so there is no need to refuse it even for hypertensive patients and cores. Rejection in favor of unconfirmed myths does a lot of harm to health, while good mood- to the benefit of our well-being. Just follow the measure and live up to 100 years!

Kyrgys Chayana

The chemical composition of tea is being studied. Benefits and harms of tea. Helpful Hints on the use of tea in cosmetics.

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Ministry of Education, Science and Youth Policy of the Republic of Tyva

Municipal educational institution

Secondary school No. 3 of Ak-Dovurak

Work for the XV republican scientific-practical conference

"Step into the Future"

Section chemistry

Topic:

"Study of the chemical composition of tea"

Performed:

10 "a" class student

Kyrgys Chayana Mergenovna

MOU secondary school №3 Ak-Dovurak

Supervisor:

Saryglar Tatyana Ashak-oolovna

Chemistry and biology teacher

MOU secondary school №3 Ak-Dovurak

Ak-Dovurak

2011

annotation

work performed by a student of 10 "a" class MOU secondary school No. 3 in Ak-Dovurak

Kyrgys Chayana

IN research work"The chemical composition of tea" studies the chemical composition, the effects of tea on the human body. The use of tea in cosmetics.

In the experimental part, he analyzes the chemical composition of tea for pectins and caffeine

The aim is to determine the most pectin-containing varieties of tea; to reveal the possibilities of non-traditional use of tea in cosmetics.

1. Introduction………………………………………………………………………...3

2. Biology of the tea plant …………………………................................................... ..4.

3. The chemical composition of tea……………………………………………………....... 5.

4. The effect of tea on the human body……………………………………………….8.

5. experimental part

Obtaining pectins from tea……………………………………………………..9

Getting caffeine from tea……………………………………………………….10

6. Conclusions………………………………………………………………………… 11

7. Literature…………………………………………………………………......12

8. Appendix …………………………………………………………………….13

Introduction

Nowadays, every person in the world drinks tea every day. But he doesn’t think at all about their benefits or harms, what determines the quality and taste of tea, what is the difference between varieties and the difference in price, because today there are more than enough varieties of these products. In our work, we will try to answer these questions.

Tea well relieves fatigue and headache, increases mental and physical activity, stimulates the brain, heart, and respiration. But certain categories of people should reduce tea consumption. Tea contains much more caffeine than coffee.

Tea consists of 30-50% extractives, i.e. water-soluble parts. The six most important components of tea are tannins, essential oils, alkaloids, amino acids, pigments and vitamins, and pectin.

Pectin substances are one of the components of the prevention of lipid metabolism disorders, atherosclerosis, diabetes mellitus, cholelithiasis. The content of pectins in tea ranges from 2 to 3%, but the quality of tea largely depends on them. 1 To determine the most pectin-containing varieties of tea was the goal of our work.

Studying the chemical composition of tea

Target: - to determine the most pectin-containing varieties of tea;

To identify the possibilities of non-traditional use of tea.

Tasks: 1. To study the literature on the chemical composition of various varieties of tea.

1. Identify the most pectin-containing varieties of tea
2. Determine the possibility of non-traditional use of tea

Object of study– tea of ​​various brands

Subject of study- the content of pectin substances in tea of ​​various brands

Relevance work is that at present every person in the world drinks tea every day. But he doesn’t think at all about their benefits or harms, what determines the quality and taste of tea, what is the difference between varieties and the difference in price, because today there are more than enough varieties of these products. In our work, we will try to answer these questions.

Practical significancework lies in the fact that in the course of theoretical and practical study of the chemical composition of tea, students learn about the benefits or harms of tea. We can recommend several prohibitions on the use of it and the additional use of tea in cosmetics.

Methods: study of theoretical material; experiment; comparisons and analysis.

1. V.V. Pokhlebkin. Tea 3.

Biology of the tea plant

Where did the word "tea" come from?

The tea drink is first mentioned in manuscripts from 2700 BC. Tea cultivation began in China in the 4th century BC. AD Russia before Europe got acquainted with the Chinese drink "tsai-e". This name was subsequently transformed into the word "tea".

In 1638, the Russian ambassador Vasily Starkov brought dried tea leaves to Mikhail Fedorovich as a gift from the Mongolian Aldyn Khan.

Where is tea grown?

The main tea-producing countries in the world areAsian states:India, China, Sri Lanka, Indonesia, Pakistan, Japan, Malaysia, Burma, Thailand, Vietnam, Iran. In Europe : Georgia, Azerbaijan, Russia in the south of the Krasnodar Territory, in the Black Sea region. In Africa : Kenya, Sudan, Uganda, Rwanda, Tanzania, Zimbabwe, Zambia, Mozambique, Cameroon, Burunda, Mali, Madagascar, South Africa, as well as on the islands of Mauritius, the Azores. In South America: Brazil, Argentina, Peru, Chile, Colombia, Bolivia,In Central America: in Mexico, Guatemala..In Northern Australia, Papua New Guinea and the Fiji Islands.

Tea is an evergreen plant that exists in two forms: Chinese tea - (this is a shrub - the mountainous regions of Southeast Asia) and Assam tea (a tree growing in India)

What external factors influence the development and taste of tea?

Tea needs warm summers and autumns to grow; (not lower than +20), but it is enough Cold winter(not higher than +10, but not lower than -3). The concentration of aromatic substances in the tea leaf depends on the length of daylight hours and the total number of sunny days. With a lack of light and sun, tea acquires a rough taste, becomes non-aromatic and grassy.

Is the quality of the finished tea closely related to the place of growth?

Certainly. Indian black teas are strong, give an intense infusion

Ceylon has a brighter infusion with a reddish tint and the same strong taste. Chinese ones are more diverse in shades of taste and aroma, less harsh in taste. Azerbaijani and Krasnodar teas with their properties are closer to Chinese and Indian ones, they are distinguished by evenness of taste and aroma, delicate, but rather weak. Georgian teas have a pleasant, velvety, pungent taste that is more pleasant, the aroma is slightly pronounced.

The chemical composition of tea

Although tea has been studied for centuries, and scientists have been working on uncovering its chemical composition for at least a hundred and fifty years, only in recent decades has it become possible to gain a relatively complete picture of what chemicals are in tea.

Studies have shown that tea consists of 30-50% of extractives, i.e. water-soluble parts. In practice, solubility is never fully realized. Green teas contain more soluble substances (40-50%), while black teas contain less (30-45%). In addition, the younger, the higher the quality of the tea leaves, the richer in extractive substances the dry tea obtained from them. And vice versa, the older, coarser the leaves, the less soluble substances go into the infusion, the less tasty the tea.

From soluble substances, first of all, you should pay attention to the six most important groups or components of tea:these are tannins, essential oils, alkaloids, amino acids, pigments and vitamins. 1

Tannins- one of the essential components of tea and tea infusion. They make up 15-30% of tea and are a complex mixture of more than three dozen polyphenolic compounds, consisting of t annina and various (at least seven) catechins, polyphenols and their derivatives. 1

Tannin in tea acquires a pleasant astringency, which gives the main taste to the tea infusion.The more tannins, the higher the quality of tea, better color, bitterness and aroma. Tannins have a calming effect on the stomach and intestines;

An essential component of tea are and alkaloids . Among the alkaloids, the most famous has always been and remains caffeine or, as it is also called in the composition of tea, thein.

It has a stimulating effect. There is more caffeine in tea than in coffee (1-4%), but tea caffeine has a milder effect: firstly, they take less tea for brewing than coffee; secondly, caffeine in tea forms a compound with tannin, which has a milder effect on the cardiovascular and central nervous systems; thirdly, tea caffeine does not accumulate in the human body; fourthly, in addition to caffeine, tea contains alkaloids theobromine and theophylline - they are good vasodilators and diuretics.

Caffeine - one of the main culprits of people's craving for tea as a tonic drink. In its pure form, it is a colorless, odorless, but bitter-tasting substance, which is contained, however, not only in tea, but also in coffee, cocoa, kola nuts, mate and some other tropical plants.

1 V.V. Pokhlebkin. Tea 5.

Caffeine belongs to those few substances of tea, the composition and quantity of which change very little during processing. Meanwhile, different varieties of tea contain different percentages of caffeine. For a long time it remained a mystery. Then it turned out that caffeine is distributed unevenly in the tea plant. The first leaf of the flush contains 4-5% caffeine, the second - 3-4%, the third - 2.5%, the rest - from 0.5 to 1.5%. There is no caffeine in tea seeds. This suggests that caffeine is not inherent in tea from birth, but is acquired in the process of growing a tea bush. From this it is clear that high quality teas made from the first leaves contain more caffeine than teas from coarse raw materials. That is why pressed teas, where caffeine is practically absent, the peoples of Buryatia, Kalmykia, Mongolia can drink in very large quantities. And that is why Kazakhs, Turkmens, who also consume black tea in large quantities, prefer its second and even third grades, where caffeine is contained in extremely small doses, but there are a lot of tannins, pectins, which are so important for preventing gastrointestinal diseases in Central Asia.

In addition, proteins serve as a source of those amino acids that arise during the processing of tea leaves into finished tea.

Protein substancestogether with free amino acids make up from 16 to 25% of tea. Proteins are the most important component of the tea leaf. Proteins are enzymes.

As for amino acids,then 17 of them were found in tea, and the nature of one of them has not yet been clarified. Among the amino acids of tea there is glutamic acid, which is extremely important for the life of the human body, actively contributing to the restoration of the depleted nervous system. Amino acids, when interacting with sugars, as well as tannins and catechins, at elevated temperatures during the production of tea, form aldehydes and thus take part in the formation of tea aroma.

Pigments (rutin), which are part of tea, also play an important role. People have long noticed the ability of tea infusion to take on different colors. These substances determine the color of the infusion, which, depending on the type and variety of tea, can be from light yellow to reddish brown.

. Mineral and other inorganic substancestea contains from 4 to 7%. They are not limited to iron salts, which have been discovered in tea for a relatively long time. In addition to ferrous compounds, tea also contains metals such as magnesium, manganese, and sodium.

Together with silicon, potassium, calcium, they are extremely important for the nutrition of various human tissues and especially for the formation of centers of electrostatic and radioactive phenomena in our body. Tea also contains other metals and inorganic substances in the form of trace elements, including fluorine, iodine, copper, gold, etc. All of them are part of complex compounds, but, being in a colloidal state, can be dissolved in water and go into tea infusion (especially fluorine and iodine, which serves as an anti-sclerotic agent).

Particular attention should be paid to phosphorus and its compounds. The higher the grade of tea, the more phosphorus and potassium it contains. The latter is very important for maintaining the normal activity of the cardiovascular system.

The composition of tea also includes a small in terms of specific gravity, but a diverse group ofresinous substances. These are complexes of complex chemical composition: alcohols (resenols), resin acids, resin phenols and other organic compounds.

But their role in tea is broadly clear: they act mainly as carriers, and even more so as tea flavor fixers.

Another group of soluble organic compounds in tea is formed byorganic acids(about 1%), which include oxalic, citric, malic, succinic, pyruvic, fumaric and two or three more acids. In the composition of tea, they are still poorly studied, but it is clear that in general they increase the nutritional and dietary value of tea.

Enzymes or enzymes , are contained in tea mainly in an insoluble, bound state. These are biological catalysts. With their help, all chemical transformations take place both in a living tea plant, during its growth, and in the process of factory preparation of tea.

pectin substancesare colloidal substances with a complex composition. Their content in tea ranges from 2 to 3%. In the presence of sugars and acids, they can form gelatinous masses - jelly. Pectins are of no small importance for maintaining the quality of tea: such a physical property of tea as its hygroscopicity is associated with them. With a lack of pectin acid in tea, its hygroscopicity increases sharply, and, consequently, the tea spoils faster. The fact is that pectic acid covers each tea leaf with a thin gelatin film that is poorly permeable to moisture and thus plays the role of a “raincoat” for tea. Recently, the positive role of pectins for the human body has been increasingly determined, especially in the treatment of gastrointestinal diseases. Good-quality teas tend to contain more water-soluble pectins than poor-quality teas.

Carbohydrates Tea contains a variety of sugars, from simple sugars to complex polysaccharides. The higher the percentage of carbohydrates in tea, the lower its grade. Therefore, carbohydrates are a kind of ballast for tea. Fortunately, most of them are insoluble. Moreover, polysaccharides that are unnecessary to a person are insoluble - starch, cellulose, hemicellulose, which make up from 10 to 12% of tea. But useful carbohydrates - sucrose, glucose, fructose, maltose (they are from 1 to 4% in tea) are soluble. 1

So, even a cursory and incomplete acquaintance with the chemical composition of tea convinces us that nature has created a kind of chemical warehouse in the tea leaf, or rather, a whole chemical laboratory. Moreover, the most surprising and remarkable thing is that this is a permanent laboratory.

What is the effect of tea on the human body?

Tea increases mental activity, eliminates fatigue, tones up the nervous system, enhances blood circulation, improves digestion, helps regulate the activity of the kidneys and the accumulation of ascorbic acid in the body, strengthens the walls of blood vessels. Tea protects teeth from caries: it contains fluoride. Tea helps to eliminate toxins from the body, it contains a lot of minerals that restore the acid-base balance of the body. In addition, the catechins found in tea cleanse the body of free radicals and lower blood cholesterol levels.

Output:

1. Tea is a treasury of useful substances for humans
2. The tea plant draws from the soil and synthesizes the most diverse and rare substances useful to humans.
3. Ready tea has the ability to give its best, most useful part to the solution
4. To preserve the chemical composition tea needed brew correctly

The taste of tea is influenced by the method of preparation of tea leaves. Need good water clean, odorless. The teapot can be ceramic, porcelain or glass. Green tea is brewed for 2-3 minutes, and then immediately filtered, as it quickly begins to taste bitter. Black tea - longer - up to 4-5 minutes, so that more tannins dissolve in water. Cream or milk is served with tea, as well as berries and fruits.

1. A.T. Soldatenkov, N.M. Kolyadina et al., Fundamentals of organic chemistry of food, feed and biological additives

experimental part

Obtaining pectin substances

Target: identify the most pectin-containing varieties of tea

Working process:

1. The tea leaves of the brand were placed in a flask and poured 40 ml of warm water
2. After 30 minutes, the solution was filtered and 40 ml of warm water was poured again.
3. Mixed filtrate No. 1 and No. 2, taking 5 ml of pectin, added 20 ml of NaOH to it and waited 30 minutes.
4. Heated on a water bath 2 ml of an alkaline solution of pectins. Added 5 ml of 1N acetic acid and 1 ml of lead acetate

The results of the experiment on the presence of pectins in tea

	Tea brands	Sediment	Quality
	Akbar	Curdled bright yellow	high
	Lisma	Curdled bright yellow	high
	Kandy	No sediment Footprints	Low
	Nuri	No sediment	Low
	Gita	No sediment	Low

Output:

• The physical property of tea, as its hygroscopicity, is associated with pectins. With a lack of pectin acid in tea, its hygroscopicity increases sharply, and the tea spoils faster. Good-quality teas tend to contain more water-soluble pectins than poor-quality teas.
• . Curdled light yellow precipitates fell out in test tubes No. 1, No. 2. Precipitation did not fall in test tubes No. 3,4,5. Hence, it follows that the content of pectins is higher in tea "Akbar" "Lisma"; less or absent in Kandy, Nuri, Gita tea
• The most pectin-containing teas: "Akbar" - green tea, "Lisma" - black Indian tea
• .Pectin substances are polymer compounds with a molecular weight of 10 ... 100 thousand daltons. They are the carbohydrate component of the cell wall and intercellular space of plants

Their meaning: prevention of fat metabolism, atherosclerosis, diabetes mellitus, cholelithiasis; affect the function of the large intestine; there is a positive role of pectins in the treatment of gastrointestinal diseases.

They are part of the cell walls of plants, but peels of citrus fruits (40%), as well as the core of apples (20%) are especially rich in them. Found in fruits and roots. They protect them from drying out, affect drought tolerance.

Getting caffeine from tea.

Target: release of caffeine from tea

Equipment: porcelain crucible, mortar and pestle, spirit lamp, match, laboratory stand, porcelain cup

Reagents: black tea, 2 g magnesium oxide

Working process:

1. Put a teaspoon of black tea crushed in a mortar and 2 g of magnesium oxide into a porcelain crucible.

2. Mix the substances and put the crucible on fire. Heat over moderate heat

3. Put a porcelain cup with cold water on top of the crucible

4. In the presence of magnesium oxide, caffeine will sublimate, i.e. turn into steam. When exposed to a cold surface, the caffeine will harden and settle to the bottom of the cup in the form of colorless crystals.

Qualitative reactions to pectin and caffeine

Objective: to prove the presence of obtained pectin and caffeine

Working process:

1. To an alkaline solution of galacturonic acid (sodium pectate)5 ml of 1N acetic acid and 1 ml of lead acetate were added and heated in a water bath. In the presence of pectin, the formation ofbrick-red precipitate of lead pectate.

2.A few crystals of caffeine put onporcelain cup and drip 1-2 potassium concentrated nitric acid. Heat until the mixture on it is dry. The caffeine will oxidize and turn into amalic acid. When the acid is neutralized with ammonia solution, a red salt is formed.

CONCLUSIONS:

1. Tea has both a healing and weakening effect on the body. Almost the entire alphabet of vitamins is present in tea. Those suffering from atherosclerosis and hypertension should not drink strong tea, which is associated with the stimulating effect of caffeine on the central nervous system.

2. There are pectins in tea and much more than in coffee, but less in an apple. The largest amount of pectins was found in Akbar and Lisman teas. Of the tea brands "Princess Kandy", "Princess Nuri", "Princess Gita" that participated in the same experiment, they did not receive pectins, which indicates the poor quality of tea or its fake.

3. During the experiment, it was proved that the composition of Akbar tea includes caffeine. We got them in their pure form and carried out qualitative reactions to make sure that these are really obtained organic substances..

4. The possibility of additional use of pectin-containing tea varieties has been identified: eye baths, nourishing and moisturizing masks for facial skin care, toning up tired, aging skin, masks for hands, brittle nails and hair

5. Tea is a treasure trove of substances useful for humans. The tea plant draws from the soil and synthesizes the most diverse and rare substances useful to humans.

6. Ready tea has the ability to give its best, most useful part to the solution into the solution

7. To preserve the chemical composition, tea must be brewed correctly

Literature:

1.V.V. Pokhlebkin. Tea. -- M.: Tsentopoligraf, 1997.

2.A.T. Soldatenkov, N.M. Kolyadina et al., Fundamentals of organic chemistry of food, feed and biological additives. - Moscow: ICC, 2006

3. Chemistry magazine at school No. 1. 2010 .

Tea in cosmetics

The use of tea in cosmetics is widely known. Modern cosmetic lines based on tea tree extract offer various products for face and hand skin care, hair care, hygiene products, etc. But, firstly, all these products are quite expensive, and secondly, they contain synthetic ingredients that can cause an allergic reaction. Well, and thirdly, having prepared a cosmetic product with your own hands, you are absolutely sure of its composition and the origin of the components.

With a little effort, you will create your own cosmetic line. Every woman dreams of soft velvety skin, beautiful shiny hair, and how many disappointments are delivered by hands that do not look the best after using various detergents, or heels that do not want to be soft and tender, like a baby. Every woman, and many men these days, need to make some time for their “me” and take care of their skin.

Facial tea
1. Rinsing your face with an infusion of salted green tea, or better, rubbing with ice cubes from it, will keep your skin fresh and healthy.
2. Weak infusion of tea can be used instead of make-up remover milk.
3. Rubbing the skin with an infusion of red tea in a cascade will help with inflamed acne.
4. A tea mask will help with sun-inflamed skin, enlarged pores and blood vessels. Moisten a soft cloth or gauze with tea solution and apply for 20 minutes. If the skin is dry, then after the mask it is necessary to apply a nourishing cream.
4. Tea can be used to make a mask for aging skin. Dilute a tablespoon of flour with strong tea to the consistency of sour cream, add one yolk. Apply to the skin for 10-15 minutes, rinse with warm water.
6. Self-tanning tea. Brew a teaspoon of black tea with three tablespoons of water, boil for 2-3 minutes, strain. In the morning and evening, after washing, wipe the face with infusion.
7. From bags under the eyes and swollen eyelids, the thick tea that remains in the teapot will help. Mix it with sour cream and apply on the eyelids for 5-10 minutes.
Body tea
1. From sweating hands, baths from strong infusion of tea help well. It is better to choose green, because black can stain the skin. Brew 4 teaspoons of tea with two glasses of water and boil for 2-3 minutes. Do warm baths for 10-15 minutes.
2. The same procedure will save you from sweating your feet, only it is advisable to add 1 teaspoon of ground oak bark to 4 teaspoons of tea.
3. Tea baths are very tonic for the skin. Brew 4 dessert spoons of black or green tea with a glass of boiling water. Infuse for 10 minutes, strain and pour into the bath. If you take a bath with black tea, it will help your skin to "tan" a little. But after that, the bath itself will have to be thoroughly cleaned.

4. If you have minor abrasions or cuts on the body, the skin is slightly inflamed, wipe it with hibiscus infusion.
hair tea
1. Rinse your hairafter washing with a weak infusion of green tea. Hair will become lush and shiny. If this option does not suit you, simply rub the tea infusion into the hair roots with a cotton swab. So you strengthen the roots and get rid of dandruff.
2. For oily hair.Mix 30 g of vodka with a teaspoon of lemon juice and a glass of green tea, dilute with a liter boiled water. Apply everything to washed hair and do not rinse. Do 3-4 procedures.
3. Hair coloring.To give your hair a chestnut hue, prepare a strong infusion of black granulated tea. This is about 2 tablespoons per liter of water, boiled over low heat for 10-15 minutes. They need to insist, strain and apply to the hair, cover them plastic bag and insulate. After 10-15 minutes a shade will appear, after 40 minutes a saturated color. Don't rinse.
For gray hair. Mix a glass of strong hot tea with 4 tablespoons of cocoa powder or coffee, stir, apply to hair, rub and comb. Don't rinse.
4. Instead of hairspray. Before winding on curlers or braiding braids, moisten your hair well with the following solution: pour 2 teaspoons of dry tea with a glass of boiling water, insist and strain. Curls will last much longer.

REVIEW

for work done by a student of 10 "a" class MOU secondary school No. 3

Ak-Dovurak, Kyrgys Chayana Mergenovna

The author studied the work on the topic "The chemical composition of tea". The goal is to determine the most pectin-containing varieties of tea and to identify the possibilities of non-traditional use of tea. Various varieties of tea were chosen as the object of the study.

To achieve this goal, the author studied a literature review on the research topic, which makes it possible to expand knowledge about the biology of the tea plant and the chemical composition, about the benefits and harms of tea, as well as the possibility of using tea in cosmetics.

The work is presented clearly and consistently according to the plan. The author used experimental methods, comparative analysis.

Processing, analysis of the results of the experiment. Conclusions are drawn on the facts and corresponds to the objectives of the work. Practical recommendations are given at the end of the work.

The essence of the work performed shows that the student has studied theoretical issues well and owns the methodology for studying and analyzing the chemical composition of tea

The work was reviewed by the teacher of biology and chemistry of the highest category MOUSOSH No. 3 of the city of Ak-Dovurak Saryglar Tatyana Ashak-oolovna.