At present, scientists have analyzed that there are as many as 500 kinds of substances in tea, most of which are organic compounds, and the contents are the most and also have the greatest impact on the quality of tea
Polyphenols are the general name of various substances in tea, also known as tea polyphenols, tea tannins, tea tannins. Flavonoids are the main polyphenols in fresh tea leaves, including catechin, flavonol, flavonoids, anthocyanins and phenolic acids. The content of tea polyphenols varies greatly with tea varieties, seasons and fresh leaves. The low content is less than 20%, and the high content can reach 40%.
Polyphenols have a great influence on the color and aroma of tea. They are very important taste substances and have bitter and astringent taste on the whole. During the processing of polyphenols in fresh leaves, a series of reactions such as hydrolysis, isomerization, oxidation and polymerization will take place to form the strong, fresh or mellow taste of tea.
The results showed that the content of polyphenols in fresh leaves was moderate, the quality of green tea was better, the taste was strong and fresh; the red leaf bottom and red bright soup color of black tea were formed by the oxidative polymerization products of polyphenols.
The main alkaloids in tea are caffeine, theophylline and theobromine, and the content of caffeine is the highest. It’s about 2% – 5%. Caffeine itself tastes bitter, but when it forms a complex with polyphenols and oxidation products, the bitterness and astringency will be reduced and a fresh taste substance will be formed.
The substance formed by the reaction of caffeine with catechin, theaflavin, thearubin, polysaccharide, protein and amino acid is the main component of black tea soup. Therefore, black tea “cold after muddy”, indicating that it is a good tea.
3、 Free amino acids, proteins and enzymes
Amino acids and proteins are the products of nitrogen metabolism in tea plants. Generally, the protein content in fresh leaves accounts for about 20% ~ 30% of dry matter. The water-soluble protein can enhance the taste and concentration of tea soup.
Enzymes are special proteins with high efficiency and specific catalytic ability in tea tissue, mainly including hydrolase, phosphorylase, lyase, oxidoreductase, transferase and isomerase. They are not only involved in all life processes of tea plant, but also related to the quality of tea processing.
There are more than 20 kinds of free amino acids in fresh leaves. Theanine is a non protein amino acid, which is the most important free amino acid in tea. All kinds of amino acids have special taste, such as sweet, sour, salty, bitter, delicious and so on. They are important taste substances in tea. The taste of tea mainly comes from amino acids, especially theanine, glutamic acid, glutamine and aspartic acid.
The pigment in fresh leaves includes fat soluble pigment and water soluble pigment. Chlorophyll and carotenoids are lipid soluble pigments, but flavonoids and anthocyanins are water soluble pigments.
The chlorophyll content in fresh leaves is generally 1-7 mg / g. The large leaves with yellow green leaves have low chlorophyll content, which is suitable for making black tea; the small leaves with dark green leaves have high chlorophyll content, which is beneficial to the appearance, color and bottom color of green tea, and is suitable for making green tea.
Another kind of pigment in fresh leaves is carotenoids, which are yellow or orange. About 15 kinds of carotenoids have been found and identified, which play a positive role in enhancing the aroma of tea.
5、 Mineral elements
At present, more than 30 kinds of mineral elements have been found in various organs of tea plant, including 11 kinds of large elements, including nitrogen, phosphorus, potassium, calcium, magnesium, iron, etc.; more than 20 kinds of trace elements, including zinc, boron, molybdenum, fluorine, cobalt, sodium, selenium, etc.
Some elements, such as fluorine, are very low in common plants, but can reach 20-2500 mg / kg in tea. The content of mineral elements is mainly affected by the soil environment, the young and old shoots and different tea varieties.
6、 Aromatic substances
The content of aromatic volatile compounds in fresh leaves is less than 0.02%, but there are more than 100 kinds of aromatic compounds, including alcohols, aldehydes and acids. The highest content of aroma compounds in fresh leaves was cyanopherol, which accounted for 60% of the aroma components in fresh leaves.
In the process of tea making, aroma substances interact and transform to form new aroma components. In the process of tea making, some of them are volatilized due to the increase of temperature, and some of them are isomerized into trans cyanophyll alcohol, which makes the tea set have delicate fragrance.
The carbohydrate in the fresh leaves of tea plant is mainly monosaccharide, disaccharide and polysaccharide, accounting for 20% ~ 30% of dry matter. Monosaccharide and disaccharide are easily soluble in water and have a sweet taste, which is one of the sweet taste substances of tea; at the same time, monosaccharide and free amino acid react to transform into aroma substances, which make tea give off tea fragrance.
Cellulose and hemicellulose are the most abundant polysaccharides. Cellulose content is highly negatively correlated with tea tenderness, which is an important chemical index of tea tenderness.
Pectin is also found in fresh leaves. Pectin is beneficial to the formation of streaks in the processing of fresh leaves, which is beneficial to the color and luster of tea.
In addition, fresh leaves contain a certain amount of tea saponin, bitter and spicy, and easy to blister in the water. This is what causes the surface to float with a bubble when brewing tea. But don’t worry, this layer of foam is not only harmless, but beneficial. Scientific research has confirmed that tea saponin has antibacterial, anti-inflammatory and anti-oxidation effects.
The fresh leaves of tea plant contain many kinds of vitamins, among which vitamin C is the most important nutritional component.
The content of vitamin C in fresh leaves of spring tea was the highest, especially in the first and second leaves, while that in mature leaves was relatively low; the content of vitamin C in summer and autumn tea decreased gradually.
Lipids are the substances that produce fatty acids during tea hydrolysis. The content of lipids in fresh tea leaves is 40-90 mg / g, mainly including glycolipids, neutral lipids and phospholipids.
Under the catalysis of lipoxygenase, the lipids in fresh leaves can be hydrolyzed and transformed into enol and hexenal, which can promote the formation of tea aroma.
10、 Organic acids
Fresh leaves contain a variety of organic acids, up to 3% of dry matter, including malic acid, citric acid, gallic acid and so on.
Organic acid is one of the taste substances of tea. Fatty acids are involved in the formation of aroma substances in tea. Gallic acid, chlorogenic acid and other phenolic acids participate in the chemical changes in the process of black tea production, which is related to the formation of black tea pigment.
The above are the main substances contained in tea. We will give a more detailed introduction to each substance in the corresponding articles later. I hope you will have the most basic scientific knowledge about the piece of tea you drink after reading, instead of blindly listening to other people’s boasting.