Chemical composition and properties of tea. Biochemistry of tea

Introduction

Judging by historical sources, a person got acquainted with tea several millennia ago and painstakingly studied its features for many centuries, however, only in recent decades, thanks to scientific and technological progress, it has become possible to get a relatively complete picture of what chemicals are part of 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 most general way. Therefore, tea is the most complex and most diverse plant in its chemical composition.

The significance (main functions) of each group of substances that make up tea can be considered from three points of view: from the point of view of influencing 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, to a lesser extent, water-soluble proteins (albumins). 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 exchange. Alkaloids are by-products of metabolism, they serve as a reserve for protein synthesis, chemical protection 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 of a milky turbidity effect after cooling in a red tea infusion (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. Theine has numerous medicinal properties: it has a stimulating effect on the central nervous system (it tones well, increases motor activity, increases mental and physical performance, reduces fatigue, drowsiness) and cardiovascular system, acts as a diuretic, stimulates blood circulation, activates oxygen metabolism, promotes digestion, improves muscle tone, prevents cholesterol levels, reduces the formation of blood clots (preventing platelet aggregation).

Theobromine stimulates cardiac activity, dilates the vessels of the heart and brain, as well as 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 common name for more than 30 types of polyphenolic substances that are part of 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 are among the most common plant matter, 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 each other's reactivity). 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 amount. Many factors influence the accumulation of tannins. The main ones are the age and phase of plant development. In many plants, large quantity 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 body.

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. The products of their oxidation, 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 young teas harvested in early spring are most highly valued among green teas. 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 products of oxidation 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. So, 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 in strengthening the immune system (for example, epigallocatechin-3-gallate affects the lymphocytes that are responsible for 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 more efficient use ascorbic acid organism. 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 that 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 starting 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. The old leaves are coarse in texture and contain a lot of cellulose, as a result of which they produce a 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. Biological role carbohydrates for a person 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 the body's defense reactions (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 of the organic acids in tea are in the free state: these are 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, take part in the biosynthesis of alkaloids, glycosides, amino acids and other biologically active compounds, 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 as a result of oxidation they become aromatic substances (for example, linoleic acid), others are good adsorbents of aromatic components (for example, palmitic acid).

Organic acids stimulate sap secretion in 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 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 thearubigines. 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, tea polyphenols are oxidized (polyphenoloxidase catalyzes the oxidation leading to the 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 red tea tea leaves is due not only to the presence of oxidation products of polyphenolic compounds, but also to melanoids - 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 useful properties 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, promote weight loss, etc.).

Scientists from leading medical centers different countries V 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 multicomponent mixture of organic compounds. Main constituent elements 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 (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 (according to the content of vitamin C green tea comparable to citrus crops, although this content is reduced during fermentation). 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 to 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) is an anti-allergic vitamin that normalizes lipid metabolism, stimulates the production of adrenal hormones, making it a powerful tool for treating 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 ones 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 of the distinctive features of 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 . Thanks 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 shades, and a golden rim becomes noticeable along 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 takes place especially intensively and quickly 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 formation of 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 microorganisms, plays a paramount role in the formation of the main properties of Puer tea. 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 from the body heavy metals and radionuclides, 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. Maintains a high level of immune resistance of the body.
	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.

CHEMICAL COMPOSITION AND NUTRITIONAL ANALYSIS

Nutritional value and chemical composition "Tea (dry brew)".

The table shows the content of nutrients (calories, proteins, fats, carbohydrates, vitamins and minerals) per 100 grams of the edible part.

Nutrient	Quantity	Norm**	% of norm in 100 g	% of the norm in 100 kcal	100% normal
calories	140.9 kcal	1684 kcal	8.4%	6%	1195
Squirrels	20 g	76 g	26.3%	18.7%	380 g
Fats	5.1 g	56 g	9.1%	6.5%	1098
Carbohydrates	4 g	219 g	1.8%	1.3%	5475 g
vitamins
Vitamin A, RE	50 mcg	900 mcg	5.6%	4%	1800
Retinol	0.05 mg	~
Vitamin B1, thiamine	0.07 mg	1.5 mg	4.7%	3.3%	2143
Vitamin B2, riboflavin	1 mg	1.8 mg	55.6%	39.5%	180 g
Vitamin C, ascorbic	10 mg	90 mg	11.1%	7.9%	900 g
Vitamin PP, NE	11.32 mg	20 mg	56.6%	40.2%	177 g
Niacin	8 mg	~
macronutrients
Potassium, K	2480 mg	2500 mg	99.2%	70.4%	101 g
Calcium Ca	495 mg	1000 mg	49.5%	35.1%	202 g
Magnesium	440 mg	400 mg	110%	78.1%	91 g
Sodium, Na	82 mg	1300 mg	6.3%	4.5%	1585
Phosphorus, Ph	824 mg	800 mg	103%	73.1%	97 g
trace elements
Iron, Fe	82 mg	18 mg	455.6%	323.3%	22 g
Fluorine, F	10000 mcg	4000 mcg	250%	177.4%	40 g

Energy value Tea (dry brew) is 140.9 kcal.

Main source: Skurikhin I.M. etc. Chemical composition of foodstuffs. .

** This table shows the average norms of vitamins and minerals for an adult. If you want to know the norms based on your gender, age and other factors, then use the My Healthy Diet application.

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USEFUL PROPERTIES TEA (DRY brewing)

Tea (dry brew) rich in vitamins and minerals such as: vitamin B2 - 55.6%, vitamin C - 11.1%, vitamin PP - 56.6%, potassium - 99.2%, calcium - 49.5%, magnesium - 110% , phosphorus - 103%, iron - 455.6%, fluorine - 250%

Benefits of tea (dry brew)

• Vitamin B2 participates in redox reactions, increases the susceptibility of color by the visual analyzer and dark adaptation. Inadequate intake of vitamin B2 is accompanied by a violation of the condition of the skin, mucous membranes, impaired light and twilight vision.
• Vitamin C participates in redox reactions, the functioning of the immune system, promotes the absorption of iron. Deficiency leads to friable and bleeding gums, nosebleeds due to increased permeability and fragility of blood capillaries.
• Vitamin PP participates in redox reactions of energy metabolism. Inadequate vitamin intake is accompanied by a violation of the normal state of the skin, gastrointestinal tract and nervous system.
• Potassium is the main intracellular ion involved in the regulation of water, acid and electrolyte balance, is involved in the processes of nerve impulses, pressure regulation.
• Calcium is the main component of our bones, acts as a regulator of the nervous system, is involved in muscle contraction. Calcium deficiency leads to demineralization of the spine, pelvic bones and lower extremities, increases the risk of osteoporosis.
• Magnesium participates in energy metabolism, synthesis of proteins, nucleic acids, has a stabilizing effect on membranes, is necessary to maintain homeostasis of calcium, potassium and sodium. Lack of magnesium leads to hypomagnesemia, increased risk of developing hypertension, heart disease.
• Phosphorus takes part in many physiological processes, including energy metabolism, regulates acid-base balance, is part of phospholipids, nucleotides and nucleic acids, is necessary for the mineralization of bones and teeth. Deficiency leads to anorexia, anemia, rickets.
• Iron is a part of proteins of various functions, including enzymes. Participates in the transport of electrons, oxygen, ensures the occurrence of redox reactions and activation of peroxidation. Insufficient consumption leads to hypochromic anemia, myoglobin deficiency atony of skeletal muscles, increased fatigue, myocardiopathy, atrophic gastritis.
• Fluorine initiates bone mineralization. Insufficient intake leads to caries, premature abrasion of tooth enamel.

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The complete guide to the most useful products you can see in the application - a set of properties of a food product, in the presence of which the physiological needs of a person for the necessary substances and energy are satisfied.

vitamins, organic substances needed in small amounts in the diet of both humans and most vertebrates. The synthesis of vitamins is usually carried out by plants, not animals. The daily human need for vitamins is only a few milligrams or micrograms. Unlike inorganic substances, vitamins are destroyed by strong heating. Many vitamins are unstable and "lost" during cooking or food processing.

Tea is a popular drink, the army of its fans is not getting smaller, on the contrary, in recent years more and more people have become interested in the history of the origin of tea, the properties of this drink. Both black and green tea are products derived from the same tea plant. Their difference is only in the degree and method of processing the tea leaf. Although it is these circumstances that affect the composition of black tea and its beneficial properties.

What is the chemical composition of tea

For more than 200 years, people have been researching tea to find out all the components and find out how useful it is. Until now, not all tea ingredients have been discovered and researched. But even now it is already clear that tea is a plant with a very complex chemical composition. It contains almost 300 substances. Up to 50% of the detected substances are soluble in water (extractive), in black tea - up to 40%.

The black composition contains the following components in different quantities:

• b vitamins,
• vitamins P, K, A,
• tannins,
• amino acids,
• caffeine,
• magnesium,
• iron,
• sodium,
• potassium,
• fluorine,
• zinc,
• copper,
• calcium.

A cup of brewed black tea contains 5 kcal, in dry form, the calorie content is 150 kcal per 100 g.

The effect of tea components on the body

Tea contains a lot of tannins. They make up to 30%. The tart taste of tea is due to the presence of tannin in it. Black tea has less of it than green tea, since more than half of it is fermented. Tannin makes tea sharp in taste, gives it a pronounced tea aroma. Ceylon and Indian teas have more tannins than Chinese teas. This substance has a wound healing, hemostatic, bactericidal, astringent, anti-inflammatory effect. Strongly brewed black tea can replace a powerful disinfectant when treating wounds.

Tea is the leader among vegetable crops in terms of the content of vitamin P. This component is not produced by the human body, but it is necessary for the normal functioning of blood vessels. In addition, vitamin P has the following properties:

• has an anti-allergic effect;
• normalizes blood pressure;
• improves digestion;
• increases the synthesis of glucocorticoids;
• useful in scurvy and rheumatic heart disease;
• restores the structure of damaged cells;
• strengthens the immune system.

Black tea contains carotene, from which vitamin A is obtained. It is necessary for the proper formation of bones. Vitamin A improves the condition of the skin, mucous membranes, fat metabolism, pancreatic function, vision. Vitamin deficiency leads to a decrease in immunity, skin diseases, malfunctions of the endocrine system.

A lot of tea and vitamins of group B. These are pantothenic acid, riboflavin, thiamine, vitamin PP. Thanks to these components, tea is useful for gout, diabetes, liver diseases, stomach ulcers, disorders of the nervous system, allergies, skin problems.

Black tea doesn't have a lot of vitamin C, but it does. Fresh tea leaves contain more ascorbic acid than citrus fruits. But with further processing, vitamin C is destroyed.

Vitamin K, contained in black tea, ensures blood clotting.

Essential oils have a beneficial effect on the nervous system. Tea has a unique property: it can soothe and tone in equal measure.

Some people find coffee to be more energizing than tea. In fact, coffee, thanks to the caffeine alkaloid, has a quick effect, which also quickly passes. And it is absorbed more slowly, but its effect does not go away for a long time, since it is excreted from the body gradually.

The benefits of black tea

Black tea can reduce the development of heart and vascular diseases, prevent the risk of atherosclerosis, heart attack, and stroke. Regular consumption of the drink strengthens the immune system, reduces the risk of developing diabetes.

The drink is useful for poisoning, digestive disorders. It speeds up metabolism, improves digestion, has a positive effect on the urinary system and kidney function. The drink is able to calm the nervous system, it improves mood, concentration, helps to cope with depression and stress.

Tea will only bring benefits, subject to the rules of brewing. It is necessary to choose only a quality product, purchasing tea only in specialized stores. Do not brew tea too strong, drink no more than 4 cups of black tea per day. Before going to bed, you should not drink black tea, so as not to cause insomnia. The Chinese believe that yesterday's tea is only harmful, so drinking it is not recommended.

Harm of black tea and contraindications

Black tea of ​​a strong concentration, especially in large quantities, can exacerbate certain chronic diseases and harm health.

Tea is contraindicated in case of increased excitability, diseases of the nervous system, mood swings, peptic ulcer. With increased eye and blood pressure, you need to be careful with the use of black tea. Consultation with a doctor in this case will not hurt.

How to brew black tea

The healing effect on the body is preserved if it is properly brewed. A clean kettle is rinsed with boiling water to warm it up. Then the required amount of tea leaves is poured into it. One teaspoon of tea is usually taken for one cup of tea.

The teapot is closed with a lid and left for a minute so that the tea opens a little. Fill it with hot water at least 95 °. Black tea is infused for about five minutes. After that, the drink can be poured into cups. If foam appears, it's okay, this once again confirms the quality of the tea.

Kyrgys Chayana

The chemical composition of tea is being studied. The 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 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

Subject:

"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 the research work "The chemical composition of tea" the chemical composition, the effects of tea on the human body are studied. 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 does not 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, 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 does not 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 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 at the same time quite 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, the better the color, firmness 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: they are associated with such physical property tea, as its hygroscopicity. 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 chemical composition 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 the nervous system, enhances blood circulation, improves digestion, helps regulate kidney activity and the accumulation of ascorbic acid in the body, strengthens the walls 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.

Conclusion:

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

Progress:

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

Conclusion:

• 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

Progress:

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

Progress:

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, improving the tone of 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 delicate velvety skin, beautiful shiny hair, and how many disappointments are caused 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 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 of 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 be insisted, filtered and applied to the hair, covered with a plastic bag and insulated. 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.

The text of the work is placed without images and formulas.
The full version of the work is available in the "Job Files" tab in PDF format

Introduction.

Tea is a tonic drink with high taste, aromatic properties, positive influence on the human body and is the most common drink on the globe. Today it can be called the drink number 1. Without it, it is impossible to imagine either a holiday or an everyday table. Herbalists in many countries claim that the constant consumption of tea reduces the risk of cancer.

Tea as a drink is so familiar and well-known to everyone that, it would seem, you won’t find anything unusual in it. We decided to look at tea from a chemical point of view. The purpose of our study is to study the chemical composition of different types of tea and show its nutritional value. In this regard, the following tasks were set: to collect and systematize literature data on the chemical composition of various varieties of tea and its effect on the body; determine the organoleptic properties of tea; determine the pH of the tea solution; determine the presence of the dye; isolate caffeine and prove its presence; isolate tannin and prove its presence; determine the content of vitamins C and D.

The subject of the study are the chemicals that make up the tea. Research objects:

1. Great tiger, natural Indian black tea, GRAND LLC, Moscow.

2. Lisma, Indian black fine leaf tea. Moscow region, Fryazino JSC Company "MAY"

3. Lipton., black long leaf, Moscow region, Serpukhov LLC Universal food technologies

4. Princess Gita, India medium, Black long leaf, broken leaf, LLC "NEP" Leningrad region, pos. them. Sverdlov.

5. JAVA "Karkade", Russia, St. Petersburg.

1. Chemical composition of tea

The value of tea as a flavoring product is due to its aromatic, gustatory and tonic properties. Tea eliminates fatigue, helps restore lost ability to work and improves a person's well-being. It is widely used as a diaphoretic for colds, it has a positive effect on the digestive, circulatory and nervous systems.

Tea is obtained by special processing of young apical shoots (flushes) of an evergreen tea plant.

Tea is the most complex plant in terms of its chemical composition. It contains over 300 chemicals and compounds.

The tea leaf consists of water, solids, extractives, alkaloids, phenolic compounds, carbohydrates, nitrogen-containing substances of non-alkaloid nature, glycosides, pigments, organic acids, minerals, essential oils, aldehydes, resins, vitamins and enzymes.

Water- the main component of the tea leaf and the environment in which the interaction of substances occurs.

Dry matter can be divided into soluble in hot water and insoluble. The first group includes substances that positively affect the quality of tea: phenolic compounds (tannin, catechins, phenolcarboxylic acids, etc.), essential oils and aldehydes, caffeine, amino acids, vitamins, enzymes, water-soluble carbohydrates, micro- and macroelements, etc. The second group includes ballast substances, i.e., negatively affecting the quality of tea: high-molecular polymers (cellulose, hemicellulose, lignin, protopectin, pectic acid), chlorophylls, insoluble proteins, etc.

alkaloids- nitrogen-containing substances, widely distributed in the plant world. The tea leaf also contains alkaloids, which belong to heterocyclic compounds and are organic bases, so they give salts with acids (tartaric, malic, citric, etc.). The tea leaf contains purine derivatives - caffeine, theobromine and theophylline:

In the tea plant, mainly caffeine is formed and accumulated, the content of which can reach 2-3%. The high content of caffeine in tea indicates its quality. Caffeine is widely used in medicine as a central nervous system stimulant, causes an increase in the vital activity of all body tissues, enhances metabolism, respiration and blood circulation, excitation of cortical processes, and also has a diuretic effect. Subjectively, the overall effect of the physiological effects of caffeine on the human body is often associated with an increase in activity, insomnia, and the ability to focus on tedious work. This effect lasts approx. 30 min. Although caffeine does not accumulate in the body, excessive consumption of tea (more 600 mg of caffeine per day, which corresponds to approximately 6 cups of tea) can lead to a kind of drug addiction - "coffeeism" (anxiety, palpitations, insomnia, headache, etc.).

Phenolic compounds. This group is the most valuable part of the green tea leaf and is represented mainly by catechins and their gall esters. Phenolic compounds include over 30 compounds close in nature, their content reaches 25% dry weight of tea leaves. Catechins account for 60-70% all phenolic compounds.

Carbohydrates- an important group of chemical compounds that make up the tea plant.

Water soluble carbohydrates - glucose and fructose have the same empirical formula C 6 H 12 O 6 . They differ in that glucose contains an aldehyde group, while fructose contains a ketone group. When one molecule of glucose and one molecule of fructose combine, a disaccharide, sucrose, is formed:

Over time, the content of monosaccharides and sucrose in the tea leaf increases.

Among polysaccharides cellulose, hemicellulose and starch were found in tea. Cellulose- the main structural polysaccharide of the plant cell wall. Depending on the growing season, the cellulose content ranges from 6 before 10%. As the leaf ages, its amount increases sharply. In the production of tea, it is considered a ballast substance.

Glycosides are considered as complex substances that consist of two components connected by a glycosidic hydroxyl: one is a sugar, and the other is a non-sugar, or aglycone. In glycosides, sugars can be glucose, fructose, etc. Various compounds can be used as aglycones: aldehydes, alcohols, ketones, phenols, etc. All of them can take a certain part in the formation quality indicators finished tea.

Flavonols tea leaves are represented by mono-, di- and triglycosides of three aglycones - kaempferol, quercetin and myricetin: they cause a whole range of different colors

Anthocyanins- pigments that unite a group of coloring substances of plants that are involved in the color of fruits, leaves, flowers and other plant organs.

organic acids. Tea contains acids such as citric, malic, oxalic, succinic, as well as acetic, pyruvic, ketoglutaric, oxaloacetic and a number of phenolic acids.

Minerals are contained both in the tea leaf and in the finished product. The composition of minerals includes potassium, phosphorus, calcium, magnesium, sulfur, iron, manganese, fluorine, etc. There is a direct correlation between the quality of tea and the content of the soluble part of minerals in it. Its potassium content in a tea leaf is 50-60% by weight of minerals. He is assigned great importance, both in general metabolism and in the synthesis of carbohydrates and protein compounds. The content of phosphorus in a tea leaf is 15-20% by weight of all minerals. There is more of this element in the bud and in the first leaf than in the lower and coarse leaves of the tea shoot. Magnesium part of the chlorophyll molecule. Copper and iron - in go to the composition of some physiologically important organic compounds, such as the enzymes of orthodiphenol oxidase (copper) and peroxidase (iron). A significant role in redox processes belongs to manganese, its content is 1-4% of the total mass of mineral substances.

One of the most important indicators of the quality of tea is the aroma, which is due to the presence of essential oil and resinous substances.

Essential oil- a complex mixture of substances belonging to the most diverse classes of compounds, soluble in organic solvents and having the ability to volatilize with water vapor.

Aromatic aldehydes play a significant role in the formation of tea aroma.

Taking into account the specifics of tea consumption in the form of an aqueous extract Special attention given to water-soluble vitamins in the composition of raw materials and finished products.

vitamins- these are groups of relatively low molecular weight organic compounds of various chemical nature. By solubility, they are divided into two large groups: soluble in fats and soluble in water. Fat-soluble vitamins include vitamin A, the absence of which is associated with impaired growth; vitamin D - anti-rachitic factor; vitamin K, necessary for normal blood clotting; vitamin E (tocopherols) - antihemorrhagic factor. Water-soluble vitamins include vitamins B, C, biotin, folic acid. Given that tea is consumed in the form of an aqueous extract, special attention is paid to water-soluble vitamins in the composition of tea.

Vitamin C. The tea leaf is rich in vitamin C (L-ascorbic acid). However, during the processing of tea leaves, the content of this vitamin decreases sharply, especially during fermentation and drying. This is due to the fact that vitamin C takes an active part in redox processes.

Vitamin B (thiamine, aneurin) - contains pyrimidine and thiazole nuclei. It plays an important role in the processes of carbohydrate transformations, as it is part of pyruvate decarboxylase. The content of vitamin B in tea averages 0.3-10 mg per 1 kg of dry raw materials.

Vitamin B 2 (riboflavin, lactoflavin) - a nitrogenous base of yellow-orange color, which contains the remainder of the pentaatomic alcohol ribitol. During the processing of tea leaves, riboflavin is not destroyed and almost completely passes into the finished tea.

Vitamin P- participates in redox processes, and also inhibits the action of hyaluronidase. The concentration of hyaluronic acid increases, which increases the elasticity of capillaries and reduces their permeability. In addition, it has antioxidant properties and, in particular, protects ascorbic acid and adrenaline from oxidation.

Thus, acquaintance with the chemical composition of tea shows that nature has created a kind of chemical warehouse in the tea leaf.

2. Study of the composition of tea - chemical experiment

Experience number 1. Organoleptic properties.

All types of tea were placed on filter paper and the appearance of the tea was determined. Tea was brewed for 5 minutes, then the bags were taken out and the aroma of tea in pairs, taste characteristics, degree of astringency and the presence of foreign flavors were compared.

Table 1. Appearance.

	Name of tea	Aroma in pairs	Taste	Degree of astringency	Foreign taste
	great tiger	tart strong
		Medium sweetish	nice
			Weak bitterness
	Princess Gita				grassy
	JAVA "Karkade"		Weak bitterness

Experience number 2. Determination of the pH of a tea solution.

Different types of tea were placed in test tubes, hot water, then lowered the indicator paper to determine the pH, and then compared it with the standard. All varieties of tea showed a neutral environment.

Experience number 3. Changing the color of tea depending on the pH of the environment. Determination of flavonoids in tea.

Brewed tea has a different color. Especially saturated color tea "Karkade" has, because. it is made from the bright flowers of the hibiscus plant (Sudanese rose).

Coloring depends on the content of anthocyanins - coloring substances of the cell sap of flowers, fruits and vegetables. The color of anthocyanins can change depending on the reaction of the environment. In this regard, it was interesting to investigate whether the color of tea will change from the action of acids and alkalis on it. Different varieties of tea were placed in cups and poured with boiling water. Then acid or alkali was added dropwise to each of the cups and the color change of relatively pure tea and solution medium was observed.

Table 2. Color of tea at various pH levels.

Experience No. 4. The presence of a dye.

50 ml of distilled water were poured into chemical beakers and a tea bag was lowered into each of them, the bags were then removed and the degree of coloration of cold water was compared, as well as with the color of the water in which leaf tea was placed. In containers, one tea bag was brewed for 5 minutes (100 ml of boiling water), then the bag was taken out and each tea drink, 50 ml, was poured into 2 chemical glasses. A piece of lemon weighing 2 g was placed in one of the beakers, after 10 minutes the color of the tea was compared before and after adding the lemon. The results were entered into a table.

Table 3. Presence of dye.

	Name of tea	IN cold water	In hot water
	great tiger	Color not saturated	Saturated
		Light color	The color is quite saturated
			Saturated
	Princess Gita	The brightest
	JAVA "Karkade"	The color is bright enough	Saturated

Experience number 5. Isolation of caffeine.

One teaspoon of black tea ground in a mortar and about 2 g of magnesium oxide (this substance is sold in pharmacies under the name "burnt magnesia") was placed in a porcelain crucible. Both substances were mixed and heated on an alcohol lamp. Heating should be moderate. A porcelain cup filled with cold water was placed on top of the crucible. In the presence of magnesium oxide, caffeine sublimates; turns into vapor, bypassing the liquid stage. Once on a cold surface, caffeine settles to the bottom of the cup in the form of colorless crystals. The heating was stopped, the cup was carefully removed from the crucible, and the crystals were scraped off into a clean flask. The presence of caffeine has been found in all varieties of tea.

Experience number 6. Isolation of tannin.

50 g different sort tea was poured with half a glass of boiling water and boiled over low heat for about 1 hour for a more complete extraction of soluble substances. The mixture was filtered through several layers of gauze; The filter cake was washed with hot water. It turns out about a glass of a yellow-green solution, into which 15 g of lead acetate was added. A precipitate of lead tanate formed. The liquid was carefully poured off. A glass of hot water was added to the sediment, stirred, allowed to settle, and the supernatant liquid was drained again. This operation was repeated three times to remove lead ions from the precipitate. To check whether they were really removed, a sample of the liquid was taken into a test tube and a few drops of dilute sulfuric acid were added to it. In the presence of lead ions in the solution, a white precipitate of PbSO 4 was formed.

If the reaction was negative, the lead tanate precipitate on the filter was washed with a 1% sulfuric acid solution (acid consumption was approximately ~50 ml). The solution was collected, a 0.5% solution of barium hydroxide was added dropwise, after which the precipitation of barium sulfate was separated by filtration:

Ba (OH) 2 + H 2 SO 4 \u003d BaSO 4 + 2H 2 O.

The remaining clear solution contains tea tannin. The solution was evaporated to dryness on a water bath. The tannin thus obtained was scraped off the bottom and ground into a powder. Tannin has been found in all types of tea.

Experience number 7. Determination of vitamin C in tea.

The determination technique is based on the fact that ascorbic acid molecules are easily oxidized by iodine. As soon as iodine oxidizes all ascorbic acid, the next drop, having reacted with iodine, will turn iodine blue. This determination is carried out using the iodometric method.

Placed in a flask 2 g of tea and added water to a volume of 10 ml, and then a little starch solution. Then, iodine solution was added dropwise until a stable blue color appeared, which did not disappear within 10–15 s. As a result, vitamin C was not found in Princess Gita tea.

Experience number 8. Determination of vitamin R.

Vitamin P (rutin) is determined by titration. Titration is one of the methods for determining concentration, based on measuring the volumes of solutions that react with substances. For titration, a solution of a known concentration was poured into the burette (in our case, it was a 0.05 N solution of potassium permanganate) and the buret was set to the working position. The exact volume of the solution, the concentration of which must be determined, was taken with a pipette and transferred to a conical flask (in our case, these are tea extracts).

Then, a solution with a known concentration was added dropwise from the burette into the flask with the analyzed solution, which was continuously stirred. The end of the titration was determined by the change in the color of the indicator. Vitamin P has been found in all varieties of tea, but more in Lisma and Lipton teas.

Summarizing.

The results of all studies were correlated and entered into a general table of results.

Table 4. General table of all indicators.

	Appearance	Organoleptic properties	medium pH	Changing the color of tea depending on the pH of the medium	Presence of dye	Release of caffeine	Isolation of tannin	Vitamin C	Vitamin P

Legend:

"+" - positive indicator,

"+-" - average,

"-" - a negative indicator.

Conclusion.

In the course of chemical research, we were able to find out the following:

1. The best indicators of organoleptic properties in the samples of Lisma, Lipton and Karkade.

2. All tea samples are neutral (pH = 7.0).

3. A large content of dyes contains Great Tiger tea.

4. Caffeine was found in all samples.

5. The highest content of tannin is found in Lisma and Lipton tea.

6. Vitamin C is not found in Princess Gita tea.

7. Vitamin P is found in the greatest amount in Lisma and Lipton tea.

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