Speaking of tea, everyone often talks about full fermentation, semi-fermentation, and light fermentation. Is this the same fermentation as our common fermented foods such as yogurt, wine, vinegar, etc.? What are the differences between them? Let’s learn about the fermentation of tea. .

What is fermentation

Generally speaking, fermentation refers to a certain decomposition process of organic matter by organisms. The phenomenon of fermentation has long been recognized by people, but it has been nearly 200 years to understand its essence. The fermentation is strictly defined by microbial physiology: the process by which organic matter is oxidized and degraded by organisms into oxidation products and releases energy is collectively called biological oxidation.

Fermentation defined in industrial production—industrial fermentation: Industrial production generally refers to all industrial production that relies on the life activities of microorganisms as fermentation, such as beer brewing and monosodium glutamate production. Fermentation in food: Fermented food refers to a kind of food manufactured by people using beneficial microorganisms, which has a unique flavor, such as yogurt, cheese, fermented rice, pickles, soy sauce, vinegar, tempeh, rice wine, beer, wine, etc.

Fermentation of tea-biological oxidation

It is often said that Chinese tea is divided into six major tea types according to different fermentation levels and comprehensive preparation methods. But the term fermentation here is completely different from the above-mentioned microbial fermentation in the idiom of Chinese tea. In tea, the same green leaf is processed into green tea, black tea, oolong tea, etc. by controlling biological oxidation. This process is also wrongly called fermentation. This process is more like a series of enzymatic reactions, and perhaps more should be called biological oxidation. The biological oxidation of tea is a series of oxidation processes that the oxidases existing in the cell wall promote catechins after the cell wall is damaged.

In tea cells, catechins are present in the cell fluid, while oxidase is mainly present in the cell wall, not mainly in microorganisms, so it is necessary to break the cell wall. This naturally explains why fermented tea needs to be twisted. According to the different degree of oxidation of polyphenols, it is divided into full fermentation, semi-fermentation and light fermentation. In black tea, the degree of oxidation of polyphenols is very high, which is called full fermentation; the degree of oxidation of polyphenols in oolong tea is about half, which is called semi-fermentation.

For example, in black tea processing, the purpose of fermentation is to oxidize the catechins contained in the leaves. The color of the leaves changes from green to copper-red, generating the unique color of black tea. After the cell membrane of tea is damaged, the polyphenols, amino acids and other substances in the vacuoles are gradually oxidized. At the same time, due to the oxidation of catechins, some of the substances in the leaves undergo a chemical action to produce the unique color and flavor quality of black tea.

The above is the basic meaning of fermentation in Chinese tea. However, due to the wide variety of teas in China, the rich and colorful processing technology and production methods, the definition of quality formation is different. In the production and quality formation process of some teas, in addition to the above-mentioned fermentation in the sense of biological oxidation in addition to its own enzymatic reaction In addition, microorganisms will also participate in some links.

For example, in addition to the enzymatic effect, microorganisms also participate in the fermentation process of Pu'er tea. After separation and research, the main microorganisms are Aspergillus niger, Aspergillus oryzae, Aspergillus clavulus, Aspergillus griseus, Rhizopus, lactic acid bacteria and yeasts. Nevertheless, it is necessary for us to distinguish between fermentation involving microorganisms and fermentation in the sense of biological oxidation-otherwise, the conceptual ambiguity will easily lead to misunderstandings of the formation mechanism of tea quality.