Saturday, June 6, 2020

Pu-erh tea fermentation


When it comes to the fermentation of tea, frequently heard words include unfermented, semi-fermented, fully fermented and so on. For tea, which varieties do these fermentation levels correspond to? What changes will the tea produce with different degrees of fermentation?
What is "fermentation"?

  Fermentation refers to the process in which people use microbial life activities under aerobic or anaerobic conditions to prepare microbial cells themselves, or direct metabolites or secondary metabolites. Generally speaking, fermentation refers to a certain decomposition process of organisms for organic matter.

  What is the fermentation of tea?

  Fermentation of tea leaves, that is, a series of reactions such as oxidation and hydrolysis that occur in the tea leaves in a special environment (including the action of enzymes, the benefits of damp and hot environment, etc.). The most important one is the change of tea polyphenols promoted by the oxidation promoted by polyphenol oxidase and peroxidase.

  It is different from the process of making noodles and making wine that we are familiar with. This process is more like a series of enzymatic reactions, maybe it should be called "biological oxidation". The "biological oxidation" of tea leaves is a series of oxidation processes in which oxidases present in the cell wall promote the formation of catechins after the cell wall is damaged.

  What are the types of tea fermentation?

   Chinese tea is divided into four types according to the degree of fermentation and processing technology:

   Non-fermented tea mainly refers to the tea leaves made directly without fermentation. The representative teas are Biluochun and Longjing tea.

  Semi-fermented tea destroys the chlorophyll in the tea during the production process, and makes it fermented at a state of 20%-70%, which represents Tieguanyin and Wuyiyan tea.

  Fermented tea is 100% fermented. The degree of oxidation of polyphenols is very high. The leaves turn from green to red. At this time, the representative tea of ​​full fermentation is black tea.

After fermenting tea, the tea leaves are piled up after being greened and twisted, allowing a large number of microorganisms to participate in the conversion of tea components to obtain compound polysaccharide compounds. After formation, the unique mellow and smooth taste of fermented tea is the familiar Puerh cooked tea. It is representative of fermented tea.

  Puer tea fermentation:

  The fermentation of Puerh tea is a special one in the fermentation of all tea leaves. Specially, the fermentation process is divided into pre-fermentation and post-fermentation.

Pre-fermentation:

The green tea of ​​Puerh tea is actually fermented while the sun is being exposed, especially in our high-altitude area in Yunnan. The ultraviolet radiation energy is very strong. Even a few hours of exposure is enough to make the tea in the production process The middle part of the fermentation, coupled with natural air drying, the tea itself has a very high water content, which also promotes the oxidation of organic matter in the tea, known as pre-fermentation.
Post-fermentation of cooked tea:

The post-fermentation of cooked tea is mainly due to the different types of micro-organisms (such as Aspergillus, yeast) growing in different changes in humidity (humidity) and heat (temperature), using enzymes produced by different micro-organisms, To transform the organic substances such as catechins, sugars, starch, cellulose, etc. in the tea, plus the heat energy generated when the fungus is multiplied, and simultaneously change the color, taste and aroma of the tea.

  Post-fermentation of raw tea:

  Because raw tea is not fermented by fermenting, it is only slightly fermented during the early picking process, and many components such as polyphenols and catechins remain. Therefore, in the later period of storage, through the control of the dry warehouse and the temperature and humidity, the fermentation involved by the microorganisms is blocked, and only the active ingredients of the tea itself are slowly transformed under the action of time, thereby obtaining an old tea with a good taste.

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