One, water Water Water is the basis of all life activities. Various chemical changes occurring in plants, the formation and transformation of substances, are inseparable from water. Similarly, water is also indispensable to the life activities of the tea tree material, but the distribution of water in the tea tree parts of the body is not uniform, the life activities of the metabolism of the parts of the water content is high. Young tea tree tips generally contain 75-78% water, leaf aging after the water content is reduced. Different tea varieties, natural conditions and agricultural technology measures, so that the water content of fresh leaves is the same. Tea tree body water can be divided into free water and bound water. Free water mainly exists in the cellular fluid and cell interstitial space, free state. Soluble substances in tea such as tea polyphenols, amino acids, caffeine, inorganic salts, etc. are dissolved in this water. Moisture in the manufacturing process to participate in a series of biochemical reactions, but also an important medium for chemical reactions. Therefore, the control of water content is also an important technical indicators, tea in addition to free water there is a bound water, it is combined with the cell protoplasm, protoplasmic colloid and exist. Fresh leaves in the tea-making process, the water has a different degree of reduction. Due to the reduction of water, lifting the expansion pressure of the leaf cells, the cellular fluid concentration, thus stimulating a series of changes in the various chemical components within the cell, so that the fresh leaves are suitable for processing requirements. Therefore, the correct control of water changes in the tea-making process is an important technical indicator of tea-making, is to ensure the quality of tea-making key. After the fresh leaves are processed into dry tea, most of them have been evaporated and lost, and finally only 4-6% of the water is generally required to be retained. Therefore, it usually takes more than 2kg of fresh leaves to make 0.5kg of dry tea. The water content of finished tea varies according to different requirements of tea types. It is generally believed that the water content of finished tea is controlled within 3-5%, under reasonable storage conditions, the quality is more stable and not easy to deteriorate. Broadly speaking, in addition to water in the tea, the rest are dry matter, as a beverage tea, its dry matter in about 35-45% of the material is soluble in boiling water, this part of the material can be dissolved in boiling water collectively referred to as the "water leachate", due to the old and young of the fresh leaves are different, and made of the tea of the Due to the different age and tenderness of fresh leaves, the water leachate content of the tea made from them is also different. Water leachate contains a variety of substances, such as tea polyphenols, caffeine, amino acids, soluble sugar, pectin, inorganic components, vitamins, water-soluble pigments and aromatic substances. Tea quality is determined by the variety of substances, the number and composition of the proportion.
Tea polyphenols Tea polyphenols is the general term for phenolic substances in tea. Mainly composed of more than 30 phenolic substances, according to its chemical structure can be divided into four categories of catechins, flavonoids, anthocyanins and phenolic acids. Among them, the content of catechins accounted for the largest proportion of the highest, accounting for about 70% of the total amount of tea polyphenols, different varieties vary, high up to 80% or more, and low also about 50%. Tea polyphenols are the most active part of tea tree physiology. In the tender tea tree, metabolism is strong, especially the photosynthesis of the strongest parts of the synthesis. Therefore, the more tender the buds and leaves, the more tea polyphenols, with the maturity of the new shoots, the content gradually decline. Tea catechins generally contain 10-25%, mainly composed of the following six kinds of catechins: L-EGC; D.L-GC; L-EC; D.L-C; L -The last two catechins are also called ester catechins, and the first four are usually called non-ester catechins. The fresh leaves of tea contain the largest amount and proportion of ester catechins, while L-EC and D.L-C contain the least. The content and proportion of various catechins vary with varieties, old and young, seasons and cultivation conditions. The changes of catechins in the process of tea making are quite significant and important, and are closely related to the color, aroma and taste of tea. Ester-type catechins have strong astringency, with bitter and astringent flavor; non-ester-type catechins have weak astringency. In the process of tea making, catechins are oxidized and polymerized, forming a series of oxidized polymerization products such as TF, TR, TB, etc., which play a decisive role in the quality characteristics of black tea. Theaflavin (TF) is bright orange-yellow, pungent flavor, combined with caffeine to make the taste more fresh; thearubigin (TR) is brown, is the main component of the red tea soup, combined with protein, generating insoluble brown-red material, so that the leaf quality becomes red. In the TF and TR content of both, TF content is high, the tea broth is red, bright, "gold ring" obvious, taste fresh; TR proportion is high, the soup color is red and dark, taste mellow. Flavonoids, also known as flower flavonoids, mostly in the form of glycosides present in tea, belong to flavonoids and flavonols. Green tea in the presence of flavonoids and their glycosides have 21 kinds, of which the more important are oyster glycoside soapwort glycosides and so on. There are more than ten kinds of flavonol substances, due to different molecular structure can be divided into three categories: (a) kaempferol and its glycosides; (b) quercetin and its glycosides; (c) popcorn ketone and its glycosides. The total content of flavonoids in tea is 1-2%. Flavonoids are the main substances that constitute the yellow-green color of green tea soup. According to research, nineteen kinds have been found in green tea soup. Anthocyanin is also known as flower pigment. Tea tree in the high temperature and dry season, many varieties of purple buds and leaves appear, this is the formation of anthocyanin accumulation, purple buds and leaves in the anthocyanin content is often as high as 0.5 - 10% or more. Anthocyanins have obvious bitter flavor, unfavorable to the quality. The anthocyanins found in tea are rosmarinus officinalis pigment, delphinium pigment, green hibiscus anthocyanin and their glycosides. The content of phenolic acids in tea is small, mainly including gallic acid, tea gallotannins, ellagic acid, chlorogenic acid, caffeic acid, p-coumaric acid, etc., of which gallic acid and tea gallotannins are more abundant. The total amount of tea polyphenols accounts for about one-third of the dry matter of fresh leaves, which is an important feature of tea tree metabolism. Catechin biosynthesis pathway, so far, although not completely clear, but a large number of tests have proved that the formation of the basic structure of catechins and sugar metabolism is closely related to the basic structure of catechins, anthocyanins and flavonoids in tea is extremely similar. Tea polyphenol content and composition changes are very susceptible to external conditions, is the formation of tea quality is one of the important components. Tea polyphenols are a class of physiologically active substances, tea polyphenols have the function of vitamin P, can regulate the permeability of human blood vessel wall, enhance the toughness of microvessels. Synergistic effect with vitamin C, the effect is more pronounced, certain heart disease has a certain efficacy, can prevent arterial and hepatic sclerosis, as well as detoxification, antidiarrheal, antibacterial and other pharmacological effects.
Three, protein and amino acids in tea is the product of nitrogen metabolism of amino acids. Nitrogen is absorbed by the tea tree through the metabolic transformation into the ammoniacal nitrogen or nitrate nitrogen in the soil is absorbed by the tea tree, converted into ammonia and then through the reduction of ketashioic acid ammonia, the formation of a certain type of amino acid, and then through the role of ammonia and amino acid transformation, the formation of a variety of amino acids. Amino acids in tea in the process of metabolism, through oxidation, hydrolysis and a series of effects of deamination and conversion into other substances, deamination and decarboxylation of free ammonia and amines formed in the process of amide, converted into asparagine, glutamine and theanine and other substances. Amino acids and proteins are important nitrogenous substances in tea, and many amino acids are the basic units of proteins. The protein content in tea is up to 22% or more, but most of them are not water-soluble, so people can't make full use of these proteins when drinking tea. Proteins that can dissolve in water are usually called "water-soluble proteins", and their content is only 1-2%. Proteins in tea by gluten, xxx, globulin and protein composition, of which the largest proportion of gluten, about 80% of the total amount of protein, the other several protein content is less. Water-soluble is xxx, this protein has a positive effect on the flavor of tea soup. Amino acids in tea are very diverse, and more than 25 kinds have been found. The main ones are: theanine, aspartic acid, asparagine, glutamic acid, glycine, glutamine, arginine, serine, alanine, lysine, histidine, threonine, valine, phenylalanine, tyrosine, leucine and isoleucine. The total content of amino acids varies greatly according to varieties, seasons, old and young and other factors, young tea leaves generally contain 2-4% of the above dozen kinds of amino acids, theanine, glutamic acid, aspartic acid, arginine and other content is higher, especially the content of theanine is the most prominent, accounting for more than 50-60% of the total amount of free amino acids, the young shoots and young stems accounted for a greater proportion; glutamic acid, alanine, lysine, histidine, threonine, valine, phenylalanine, tyrosine, leucine and isoleucine. Tender shoots and stems accounted for a larger proportion; glutamic acid is next, accounting for about 13-15% of the total; aspartic acid is next, accounting for about 10% of the total. These three amino acids account for about 80% of the total free amino acids. Tea tree synthesizes theanine in large quantities, is one of the characteristics of the tea tree metabolism, so far, in addition to a small amount of this amino acid found in a kind of mushrooms and tea tree, other plants have not been found. Pure crystalline theanine is a colorless needle crystal, melting point of 217-218 ℃, very soluble in water (soluble in 2.6 times cold water), is an important substance that constitutes the fresh taste of tea. When brewing tea, 81% of the amino acids in tea can be brewed. Most of the amino acids have fresh flavor. Some amino acids also have aroma, such as phenylalanine similar to rose scent, alanine, glutamic acid similar to flower flavor, theanine similar to caramel flavor. Amino acids and neighboring quinones can generate aldehydes with aroma, such as valine into isobutyraldehyde, leucine into isovaleraldehyde, alanine into acetaldehyde and so on. In the process of tea making, some proteins are hydrolyzed to amino acids under the action of enzymes, which is conducive to improving the quality of tea.
Four, aromatic substances Aromatic substances is a general term for a wide variety of volatile substances in tea, customarily known as aromatic oils. Aromatic substances in the tea content is not much, but the quality of tea plays an important role. Generally less than 0.02% of the content of fresh leaves, green tea contains about 0.005-0.02%, black tea leaves contain more, containing 0.01-0.03%, the content of aromatic substances in tea, although not much, but because of the composition of various types of tea aroma aromatic substances up to more than three hundred kinds of different combinations of these substances constitute the Various types of aroma. After analysis and identification, the fresh leaves to contain alcohols and some aldehydes, acids and other compounds, but more than 50 kinds of compounds, the aroma characteristics of green grass mainly, green tea are generally after killing and frying, containing hydrocarbons, alcohols, acids and nitrogen-containing compounds, so that the aroma with the green and chestnut, about 107 kinds of black tea due to withering and fermentation, the tea production in the increase of aroma components are more, which are alcohols, aldehydes, ketones, esters, acid compounds, mainly, the aroma of the tea. The black tea has more aroma components due to withering and fermentation, in which alcohols, aldehydes, ketones, esters and acids are the main compounds, and there are more than 200 kinds of aromatic substances in the aroma components. Composition of tea aroma aromatic substances, the application of gas chromatography analysis of the results of the study, can be summarized into eleven categories: hydrocarbons, alcohols, ketones, esters, lactones, acids, phenols, oxygenated compounds, sulfur-containing compounds and nitrogen-containing compounds. Various aroma substances, as they contain hydroxyl, ketone, aldehyde and other aroma groups and the formation of a variety of aroma. Tea in the various aromatic substances have their own aroma characteristics, the presence of a large number of fresh leaves is cis-cynanol, there is a strong grass gas, made of green tea, to contain indole, zirospermone compounds, benzyl alcohol, sedum alcohol, has been alcohol and pyrazine compounds; made of black tea, sedum alcohol and its oxides, has been allyl alcohol, methyl salicylate, has been acid, etc., mainly in the tea, tea in addition to aroma substances, in addition to the above introduced Aromatic substances in tea, in addition to the above mentioned aromatic substances, some amino acids and their transformations, amino acids and catechin o-quinone action products have a certain tea flavor. The above aromatic substances, its boiling point varies greatly, low only a few dozens of degrees to more than 100 degrees, high up to more than 200 degrees, for example, accounting for 60% of the aromatic substances of the fresh leaves of the green leaf alcohol, with a strong green odor, but because of its boiling point is only 157 ℃, high temperature greening, the vast majority of the volatilization of the loss of the high boiling point of aromatic substances such as sedum alcohol (that is, linalool), geraniol, phenylethanol, jasmine ketone acid, geraniol esters, etc. will retain more. etc. will be retained more, so that the tea leaves form a unique fragrance, floral and fruity, etc.. The source of aromatic substances in tea, some are synthesized in the body of tea tree in the process of new growth, but most of them are produced in the process of tea making, and transformed by other substances. Green tea greening, baking and frying thermochemical effect; black tea withering, fermentation process of biochemical effect; oolong tea greening process of enzymatic oxidation is an important source of a large number of aroma substances.
Five, alkaloids Tea contains a variety of purine alkaloids, the main component of which is caffeine, which accounts for a considerable proportion. In addition, it also contains a small amount of theophylline, theobromine and so on. Caffeine is a very weak alkali with a bitter taste. Pure product has a silky luster of colorless needle-like crystals, with a molecule of water of crystallization when crystallized from water. Heated to 100 ° C to lose water. Melting point 230 ° C, but at 120 ° C, began to sublimate. Slightly soluble in cold water, with the increase in water temperature and solubility gradually increased. Less soluble in organic solvents such as ethanol, ether, but soluble in chloroform. Tea caffeine contains about 2-5%, caffeine biosynthesis pathway and amino acids, nucleic acids, nucleotides metabolism is closely linked, so caffeine is also in the active life of the tea tree shoots part of the synthesis of the most, the highest content. Caffeine is a kind of nitrogen-containing substance, which is a nitrogen metabolism product, therefore, the amount of content is related to the level of nitrogen fertilizer applied. In the process of tea making, caffeine is slightly reduced, because caffeine begins to sublimate at 120 ℃, if the baking temperature exceeds 120 ℃, the loss may be more. Caffeine in the tea broth and tea polyphenols, amino acids combined to form a complex, with fresh flavor, has the effect of improving the taste of tea broth. This complex in the tea soup after cooling, can be dissociated out, the formation of milky "cold after the cloud", which is a sign of excellent tea soup. Caffeine is used as medicine, has the effect of excitation of the central nervous system, strengthening the ability of muscle contraction and eliminating fatigue. Pharmacologically, it is diuretic, cardiotonic and antihypertensive. In addition, there is an accelerated detoxification of the liver, reducing the toxic effects of nicotine and alcohol.
Six, sugar tea sugar including monosaccharides, disaccharides and polysaccharides in three categories, there are dozens of more than 20-30% of its content. Sugar compounds in tea are synthesized by photosynthesis, metabolic transformation and the formation of sugar compounds, therefore, the content of sugar compounds and tea yield is closely related. Monosaccharides in tea include: glucose, mannose, galactose, fructose, ribose, xylulose, arabinose, etc., its content of about 0.3-1%; tea in the disaccharide, including: maltose, sucrose, lactose, cotton seed sugar, etc., its content of about 0.5-3%; monosaccharides and disaccharides are usually easily soluble in water, so it is always known as the soluble sugar. With a sweet flavor, is one of the tea flavor substances. Tea monosaccharides and disaccharides in the metabolic process, under the action of a series of converting enzymes, easy to convert into other compounds. Broadly speaking, tea polyphenols, organic acids, aromatic substances, fats and lipids and other substances are sugar metabolites, sugar substances and important respiratory substrate, therefore, the synthesis and transformation of sugar is an important factor in the life activities of the tea tree. Tea monosaccharides and disaccharides are not only the flavor material, but also involved in the formation of tea aroma in the process of tea making. Some tea has "chestnut", "sweet" or "caramel", the formation of these aromas are often associated with changes in sugar, sugar and amino acids, organic acids, tea polyphenols and other substances Interaction. Tea polysaccharide usually refers to starch, cellulose, hemicellulose and lignin and other substances, which account for about 20% of the dry matter of tea, of which starch contains only 1-2%, the content of more cellulose and hemicellulose, containing about 9-18%. Starch in the body of the tea tree is as a storage material. Therefore, it is more abundant in seeds and roots. Cellulose material is the main component of the cell wall of the tea tree body, the whole tea tree depends on cellulose, hemicellulose and lignin to play a supporting role and growth. Tea polysaccharides are generally insoluble in water, high content is the aging of tea, poor tenderness signs. If the fresh leaves are not picked in time, cellulose increases, tissue aging, so that the appearance of the tea is coarse and loose, the inner quality of the decline. Sugar compounds in tea, in addition to the above sugar substances, there are many sugar-related substances, including: pectin, various phenolic glycosides, tea saponins, lipopolysaccharides and so on. Pectin is a colloidal substance in tea, which is a polymer compound formed by sugar metabolism, and its content accounts for about 4% of the dry weight of tea. Its water-soluble pectin is called water-soluble pectin, and its content accounts for about 0.5-2% of the pectin, which is one of the components of the formation of tea broth flavor and dry tea color and gloss. In addition to water-soluble pectin, the rest of the original pectin, insoluble in water, is involved in the composition of the cell wall components. Tea saponins, also known as tea saponin, present in the tea tree seeds, leaves, roots, stems, seeds in the highest content, containing about 1.5-4.0%. Often the saponin in the seed is called tea seed saponin, and tea saponin in the tea leaves is called tea saponin. Tea saponin taste bitter and pungent, easy to foam in water, coarse old tea coarse flavor and foam may be related to tea saponin. Tea saponin is a combination of xylose, arabinose, galactose and other sugars and other organic acids and other substances into a macromolecular compound. Tea saponin general content of about 0.4%, such as the content is too high may affect the flavor quality of tea. Lipopolysaccharide in tea is a kind of large molecule material that combines lipid and polysaccharide together, of which 50% is lipid, 30-40% is sugar, 10% is protein and other substances. Tea in the content of lipopolysaccharide is about 0.5-10%, extracted lipopolysaccharide, the activity of the note thanks to the test has the effect of anti-radiation, has aroused the interest of research workers at home and abroad.
Seven, tea pigmentation Broadly speaking, tea pigmentation refers to the pigment composition of the tea tree body and into the tea brewing, the formation of tea color pigment components. Including chlorophyll, carotene, flavonoids, anthocyanins and other oxidation products of tea polyphenols, TF, TR, TB and so on. Chlorophyll, lutein and carotene are insoluble in water, collectively known as fat-soluble pigments, flavonoids, anthocyanins, TF, TR and TB can dissolve in water, collectively known as water-soluble pigments. Fat-soluble pigments have a great influence on the color of dry tea and the color of the leaf bottom, while water-soluble pigments determine the soup color of tea broth. The content of chlorophyll in tea is generally 0.3-0.8%, and chlorophyll is mainly composed of orchid green chlorophyll a and yellow-green chlorophyll b. The chlorophyll in tea leaves is usually 0.3-0.8%. Usually tea tree leaves, chlorophyll a content than chlorophyll b content is 2-3 times higher, so the leaves are usually dark green, but young leaves, leaf color light, sometimes yellow-green, that is chlorophyll b content is relatively high. Varieties and climatic factors can also have an effect on the ratio of chlorophyll a and b. Chlorophyll in the manufacturing process has different degrees of decomposition and destruction. Black tea chlorophyll destruction is more, green tea destruction is less. Chlorophyll exists in the chloroplasts of tea tree leaf tissue, accepting light energy for photosynthesis, effectively converting light energy into chemical energy, and inorganic substances through metabolism to form a variety of organic matter to maintain the normal growth and development of the tea tree. Carotene in the tea leaves in general content of 0.02-0.1%, lutein for 0.01-0.07%, for the yellow-orange-yellow material. This kind of pigment in tea has been found in about fifteen kinds, collectively known as carotenoids, the content of more β-carotene, lutein, corydaline, α-carotene and so on. Carotenoids can also absorb light energy, chlorophyll photosynthesis plays an auxiliary role. In the process of tea production, carotenoids are easy to oxidize, loss of more, lutein change is small, when the chlorophyll is destroyed, the yellow color to show. They are insoluble in water, do not affect the tea soup color, but they are one of the pigments that constitute the bottom of the leaf and dry tea color. Carotene has the role of vitamin A on the human body, can cure eye diseases such as keratitis. After degradation in tea making, certain aromatic substances can be formed, such as dihydroanemone lactone, to improve the quality of tea. Flavonoids and anthocyanins are polyphenolic compounds, yellow and yellow-green, not only is the main component of green tea soup color, its oxidized polymers and black tea soup color also has a close relationship. The color of anthocyanin changes with the pH of the cellular fluid, under acidic conditions anthocyanin is red. Under alkaline conditions, anthocyanins are red. Under alkaline conditions, anthocyanins are blue-purple. Catechins, anthocyanins and flavonoids can be transformed into each other in the tea tree. Tea polyphenols in the manufacture of black tea oxidation polymerization of the formation of colored products collectively referred to as black tea pigments, black tea pigments generally contain theaflavin, thearubigin and theaflavin three categories of substances, theaflavin was orange-yellow color, is the decision of the tea broth is bright the main components. Black tea contains about 0.3-2.0%, thearubigin is red, is the formation of black tea soup color of the main substances, containing about 5-11%; theaflavin is dark brown is the main component of black tea soup color dark, containing about 4-9%. One of the close relationship with the quality of theaflavin, about more than eight components, usually can be divided into four categories: 1, theaflavin and isophyllotoxin and so on (3 kinds) accounted for about 10-13% of the total amount of theaflavin; 2, theaflavin single gallate (2 kinds) accounted for about theaflavin 48-58% of the total amount of theaflavin; 3, theaflavin double gallate (1 kind) accounted for about 30% of the total amount of theaflavin The theaflavin bis-gallate (1 type) accounts for about 30-40% of the total amount of theaflavin; 4. Theaflavinic acid and theaflavinic acid gallate (2 types) account for only 0.2-0.3% of the total amount of theaflavin. The amount of theaflavin formation is determined by the tea-making process, but also by the biochemical characteristics of the variety. How to maximize the content of theaflavin is a worthy research topic.
Eight, organic acids tea contains a variety of small amounts of free organic acids. The main ones are malic acid, citric acid, oxalic acid, cinchona acid and p-coumaric acid. Some organic acids and material metabolism close relationship, such as seed germination and the formation of new shoots when more organic acids, which is a sign of vigorous metabolism. Some organic acids are aroma components, such as vinyl acid; some itself is not aroma, but under the influence of oxidation or other effects, can be converted into aroma components, such as linoleic acid; some are aroma components of good suction agent, such as palmitic acid. Tea aroma components have been found in the organic acids have twenty-five kinds, some volatile, some non-volatile. Phenolic acid substances such as gallic acid is a product of tea polyphenol metabolism, involved in the biochemical changes in the tea-making process, the formation of black tea pigment has a direct impact. Tea calcium oxalate content of 0.01%, in the tea tree, it forms calcium oxalate crystals with calcium, in the anatomy of tea leaves for microscopic observation can see this crystal, can be used as a basis for identifying the true and false tea.
Nine, enzymes and vitamins Enzymes are a class of physiologically active compounds, organisms are catalysts for a variety of chemical reactions, it has a high degree of efficacy, specialization and strong characteristics. Leaving such compounds, all living things, including the tea tree can not survive, the synthesis and transformation of tea tree substances, but also rely on the catalytic effect of this substance. Such as tea root theanine synthase, can effectively synthesize a large number of theanine; tea, polyphenol oxidase can promote the oxidation of tea polyphenol polymerization to form theaflavin; protease can make protein hydrolysis into amino acids; amylase can hydrolysis of starch into glucose; oolong tea processing technology links with the main control and use of enzymes. Enzymes in tea are many and complex, summarized in several categories: hydrolases, glycosidases, phosphorylases, laccases, oxidative reductases, enzymes and isomerases. The polyphenol oxidase in tea plays an important role in the process of tea making, and is highly relevant to the formation of various tea quality styles. With the progress of research, the current use of electrophoresis technology has been divided into five or six kinds of polyphenol oxidase isomerase (function is basically the same, but the results of the enzyme class slightly different). Differences in fermentation performance of fresh leaves of different varieties, as well as differences in suitability, are related to the composition and proportion of polyphenol oxidase isoenzymes. According to the latest findings, the enzymes related to the quality genesis of oolong tea include polyphenol oxidase, peroxidase, pectinase, glycosidase, protease, and amylase, etc. In particular, glycosidase has a close relationship with the formation of the aroma of oolong tea, and β-cherrylcyrrhizal glucosidase in the tea is considered to be the main substrate for the formation of the aroma. Protease can hydrolyze the proteins in tea into various amino acids, which not only improves the aroma and freshness of tea, but also reduces the production of insoluble complexes and improves the quality of tea broth. In the process of oolong tea, although protein hydrolase can not make amino acids and soluble proteins in the amount of more accumulation, but its further participation in a variety of reactions, the transformation of the formation of a series of aromatic substances, protease on the formation of oolong tea unique qualities, especially the play of the aroma plays a very important role. Enzyme is a kind of protein body, in terms of its composition, the enzyme can be divided into two categories, one is composed of proteins with catalytic effect, known as single-component enzyme; the other is composed of protein part (enzyme protein) and non-protease part (cofactor), known as two-component enzyme. Enzymes have their own optimum temperature and pH for their reaction rate, and show maximum activity when the conditions are right; when the conditions are not right, the activity is affected or stops. When the temperature gradually increases, the activity increases. Generally speaking, when the temperature reaches 45-55℃, the effect is the strongest; above this temperature, the activity starts to be inhibited; under the temperature of 70-80℃, it is passivated; above 80℃, the enzyme protein starts to be denatured, and the activity is destroyed. Although a variety of different enzymes have their own requirements, but generally between 30-50 ℃, the temperature is too high, too low will affect the enzyme activity, the enzyme protein reaches a certain temperature, that is, to produce denaturation loss of activity. Similarly, a variety of different enzyme requirements of acidity and alkalinity are also different, a variety of enzymes only in the optimal pH, in order to achieve maximum activity. Such as polyphenol oxidase below the optimal pH5.5, its activity is getting lower and lower. Oolong tea is to create suitable conditions, give full play to the role of enzymes, promote the hydrolysis of terpene alcohol glycosides and polyphenols and other substances contained in the appropriate oxidation, the formation of oolong tea color, aroma, taste, in order to obtain excellent tea quality. On the contrary, oolong tea high temperature killing, its purpose is to use high temperature to quickly destroy the enzyme activity, fixed quality has been formed. Tea contains a variety of vitamins, water-soluble and fat-soluble vitamins, water-soluble vitamins include vitamin C, B1, B2, B3, B11, vitamin P, vitamin B and creatine. Tea contains the most vitamin C. The content of high-grade green tea can reach 0.5%, but the content of poor quality green tea and black tea is only 0.1%, or even less. Tea contains a variety of B vitamins, generally in 100g of dry tea contains 15mg or so, B vitamins have a variety of effects, is indispensable to the human body vitamins, tea in the catechins and flavonoids with the role of vitamin P, can enhance the elasticity of human blood vessels, hardening of blood vessels has an auxiliary therapeutic effect. The content of vitamin B2 (nicotinic acid) in tea, 100g of dry tea in about 100 mg or so, with the prevention of mange, dermatitis, etc.. Because tea is rich in various vitamins, so tea can not only quench thirst, refreshing, but also has a certain nutritional significance. Tea fat-soluble vitamins are vitamin A, vitamin D, vitamin E and vitamin K, etc.. Vitamin A content is more, vitamin A is a derivative of carotene, these vitamins are difficult to dissolve in water, so drinking tea for people to use not much.
Ten, ash (inorganic components) tea after high-temperature burning of the residual material is called "ash", accounting for about 4-7% of the weight of dry matter. Tea inorganic components of the largest content of phosphorus, potassium, followed by calcium, magnesium, iron, manganese, aluminum, sulfur, trace components of zinc, copper, fluorine, molybdenum, boron, lead, chromium, nickel, cadmium and so on. Most of the inorganic components in tea are nutrients absorbed by the tea tree from the soil, nitrogen, phosphorus, potassium, etc. are familiar with the bulk nutrients, and most of the rest are collectively referred to as trace elements. Ash has pure ash and coarse ash. Pure ash refers to the oxides of the elements in the ashed material; coarse ash (total ash) means that there are some un-ashed carbon particles and carbonates. Some of the ash is soluble in water, known as water-soluble ash; some insoluble in water, known as water-insoluble ash. Water insoluble ash by strong acid treatment, some soluble in acid, known as acid soluble ash; some insoluble in acid, known as acid insoluble ash. The proportion of water-soluble ash in the total ash is about 56-65%. Potassium and sodium are composed of ash are water-soluble ash, the rest of calcium, magnesium, iron, manganese, phosphorus, silicon, sulfur, etc., some soluble in water, some insoluble in water, also insoluble in dilute acid, according to the nature of its constituents and different. In general, the total ash content of young leaves is low, while the content of old leaves and tea stalks is high. Different varieties of tea water-soluble ash content also varies. In the process of tea making, the change of ash is very small. For example, the ash content of fresh leaves is 4.97%, and after making black tea and green tea, it is 4.92% and 4.93% respectively. Water-soluble ash content of high and low, can reflect the quality of the finished tea good or bad, better quality tea water-soluble ash content is relatively more. Ash content is one of the tea export inspection items, and it is usually stipulated that the ash content should not exceed 6.5%. Excessive ash content is poor quality tea or mixed with sand impurities.