Tea polyphenol, commonly known as tea tannin and tea tannin, is the general name of various phenolic substances in tea.
Flavonoids are the main polyphenols in tea leaves, including catechin, flavonol, anthocyanins and phenolic acids. The content of tea polyphenols is different in different tea plants, different seasons, and the degree of tea tenderness. The low content is less than 20%, and the high content can reach 40%.
Catechin is the main component of tea polyphenols, the content is 50% ~ 80% of the total tea polyphenols.
The content of flavonol is about 1% ~ 4%, which has the basic structure of apigenin.
Anthocyanins are the general name of the anthocyanins of Delphinium, hibiscus viridis and their glycosides. Anthocyanins mainly exist in young buds and leaves. With the growth of buds and leaves, they will be converted into catechins and flavonols. Therefore, the content of anthocyanins in the grown tea is very low.
Phenolic acid contains many kinds of substances, among which the content of chlorogenic acid is the highest, which can reach 2% ~ 4%.
Tea polyphenols have a very important influence on the color, aroma and taste of tea. It has a bitter and astringent taste and is a very important taste substance. In the process of tea processing, a series of hydrolysis, isomerization, oxidation and polymerization of tea polyphenols will occur, which will affect the strength, freshness and alcohol content of tea.
The content of tea polyphenols has a very obvious effect on the quality of green tea. The green tea with moderate content of fresh leaves has better quality, strong taste and freshness; when the proportion of fat catechins in a certain limit is large, the quality of green tea will be further improved.
“Catechin quality index” is a symbol of tea quality. The more tender the fresh leaves are, the higher the content of fat catechins is, the better the quality of tea is; after ripening and aging, the content of fat catechins will decrease and the quality of tea will decrease accordingly.
The content of tea polyphenols has more obvious effect on black tea. The red leaf bottom and red bright color of black tea are formed by the oxidative polymerization products of tea polyphenols. The content of theaflavins in fresh leaves with high content of catechins is high, and the quality of black tea is excellent.
The orange color of some green tea and oolong tea is also related to the primary oxide of tea polyphenols. The oxidation of tea polyphenols and amino acids can emit fragrance and increase the aroma of tea.
Flavonoids can be dissolved in water and have an important influence on the color and taste of tea soup.
Anthocyanins have obvious bitter taste and can be dissolved in water. The fresh leaves with high anthocyanins content can be processed into green tea, which often has dark color, bitter taste and indigo at the bottom of leaves. When 150 ml of tea contains 15 mg of anthocyanins, there is an obvious bitterness.
Generally speaking, the tea polyphenols in the fresh leaves of large leaf tea plants are more than that in the fresh leaves of tea plants with sufficient sunlight, and the tea polyphenols in summer tea are more than those in spring tea.