What is fermentation
The fermentation that says commonly, it is to point to a certain kind of decomposition process of organism to organic matter more.
Fermentation has long been known, but its nature has been known for nearly 200 years.
Microbial physiology strictly defines fermentation: the process by which organisms oxidize and degrade organic matter to oxidizing products and release energy is referred to as biological oxidation.
Definition of fermentation in industrial production -- Industrial fermentation: In industrial production, all industrial production relying on microbial life activities are generally called fermentation, such as beer brewing, monosodium glutamate production, etc.
Fermentation in food: Fermented food refers to a kind of food made by people using beneficial microorganisms, which has a unique flavor, such as yogurt, cheese, wine, pickles, soy sauce, vinegar, fermented black beans, yellow rice wine, beer, wine, etc.
Fermentation of tea -- Biological oxidation
It is often said that Chinese tea is divided into six types according to the different degrees of fermentation and the comprehensive production method.
But the term fermentation here, in the usual context of Chinese tea, is quite different from the microbial fermentation mentioned above.
In tea, the same green leaf is processed into green, black and oolong tea by controlling biological oxidation, a process that is also erroneously called fermentation.
This process is more like a series of enzymatic reactions, perhaps better known as biooxidation.
The biological oxidation of tea leaves is a series of oxidation processes of catechins promoted by oxidases in cell walls after cell walls are damaged.
In tea cells, catechins are present in the cell fluid, and oxidases are present mainly in the cell wall, not mainly in microorganisms, so the cell wall needs to be broken down.
This naturally explains why fermented tea needs to be rolled.
According to the degree of oxidation of polyphenols, full fermentation, half fermentation and light fermentation were distinguished.
In black tea, polyphenol oxidation degree is very high, then called full fermentation;
The degree of oxidation of polyphenols in Oolong tea is about half, which is called semi-fermentation.
In black tea processing, for example, fermentation is intended to oxidize catechins contained in the leaves.
The leaves change from green to coppery red, giving black tea its characteristic color.
After tea liquid cell membrane is damaged, polyphenols, amino acids and other substances in vacuoles are gradually oxidized. At the same time, due to the oxidation of catechin, a part of the substances in the leaves have chemical effects, resulting in the unique color and flavor quality of black tea.
Above is the basic meaning of fermentation that Chinese tea often says.
However, due to the wide variety of Tea in China, rich processing techniques and production methods, the definition of quality formation varies. In the production and quality formation process of some tea leaves, in addition to the above fermentation in the sense of biological oxidation of its own enzymatic reaction, microorganisms may also participate in some links.
For example, the pile-fermentation process of pu-erh tea is not only enzyme-promoting, but also involving microorganisms.
The main microorganisms are aspergillus Niger, Aspergillus oryzae, Aspergillus canthoides, Aspergillus grey-green, Rhizopus, lactobacillus and yeast, etc.
Nevertheless, it is necessary to distinguish between fermentation in the sense of microbial involvement and fermentation in the sense of biological oxidation -- otherwise, conceptual ambiguities may easily lead to misinterpretation of the formation mechanism of tea quality.
