Thursday, June 25, 2020

Knowledge: Misunderstood tea "fermentation"

It is often said that Chinese tea is divided into six major types of tea according to the degree of "fermentation" and the comprehensive manufacturing method. Usually, what we call fermentation refers to a certain decomposition process of organisms by organisms. But the term "fermentation" here is completely different from microbial fermentation in the traditional context of Chinese tea.

"In tea, a green leaf is processed into green tea, black tea, oolong tea, etc. by controlling biological oxidation. This process is also mistakenly referred to as "fermentation." The "fermentation" of tea leaves actually exists after the cell wall is damaged. The oxidases in the cell wall promote a series of oxidative processes carried out by catechins. This process is more like a series of enzymatic reactions, and perhaps it should be called "biological oxidation".

In the cells of tea, catechins are present in the cytosol, while oxidase is mainly present in the cell wall, rather than mainly in microorganisms, so the cell wall needs to be damaged. This naturally explains why tea "fermentation" needs to be twisted. According to the different degrees of oxidation of polyphenols, it also distinguishes between "full fermentation", "semi-fermentation" and "light fermentation". In black tea, the degree of oxidation of polyphenols is very high, it is called "full fermentation"; the degree of oxidation of polyphenols in oolong tea is about half, it is called "semi-fermentation".

For example, in the processing of Taiwan high mountain tea, the purpose of "fermentation" is to oxidize the catechins contained in the leaves. The color of the leaves changes from green to dark green, resulting in the unique color of Taiwan high mountain tea. After the tea cell membrane is damaged, the polyphenols, amino acids and other substances in the vacuole are gradually oxidized. At the same time, due to the oxidation of catechins, some of the substances in the leaves undergo chemical action to form the unique color and fragrance quality of Taiwan high mountain tea.

Wenshan Baozhong tea has the lowest degree of "fermentation" and is known as the "first tea". The top-grade Wenshan Baozhong tea is active, with a thick and dense change in fragrance and taste. After slowly swallowing, it is a scent of fresh fragrance!

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