Fermentation of tea is the oxidation of a mixture of polyphenols and enzymes (enzymes) present in the tea leaf. As a result of this, theaflavins and thearubigins are formed, which give the infusion of tea (black) a characteristic brown color with a reddish tint.
Fermentation is a series of chemical reactions that proceed in different ways. It all depends on external conditions (light, temperature, humidity, etc.). Known methods of artificially interrupting fermentation at a time when the sheet has reached the necessary readiness. This is done by quickly heating the tea leaf, not leading to its drying, but a transforming substance so that the fermentation processes stop.
Oxidative enzymes
Fermentation of tea is the core process of the entire technology of its production. For its implementation, it is necessary to influence the oxidizing enzymes of tea leaves: phenol oxidase and peroxidase.
Tea production provides for the maximum preservation of the valuable aromatic and taste properties of tea leaves by modifying their chemical composition. As a result, a high-quality product is obtained from raw materials.
The biochemical transformations favorable to this begin even during the collection of the tea leaf, continue when it is wilted and twisted, and already during fermentation they acquire special strength.
In the process of fermentation, a leaf twisted under the influence of oxidative processes becomes copper-red, and the smell of green slowly turns into a delicate aroma of fermented tea.
Fermentation process
In the 19th century, it was believed that fermentation of tea was a microbiological process. It was believed that a certain microflora is inherent in the tea leaf, some microorganisms produce oxidative enzymes capable of oxidizing phenolic compounds. Such an ancient theory did not justify itself, because as a result of experiments under aseptic conditions it was established that the external microflora can only interfere with the proper development of the fermentation process.
Later, already in the 20th century, oxidative enzymes were found in the tea leaf, and concluded that they are inactive in the tea bush and are able to activate when they wither. In the process of studying these soluble enzymes individually, it was found that phenol oxidase, its soluble form, has weak activity, and soluble peroxidase does not form red and brown products with high activity.
They decided to study the enzymes separately, as a result of which they discovered active phenol oxidase. This enzyme is located in insoluble areas of the leaf and does not pass into solution under ordinary conditions, which prevented it from being detected in early studies. Thus, insoluble phenol oxidase was discovered, which turned out to be the main enzyme.
Fast and slow fermentation
Fermentation of tea is carried out quickly and slowly.
During the fast fermentation process, the processing of tea leaves is carried out mechanically, that is, it is twisted or wrinkled, damaging the cell membranes. This causes a more active oxidation and reaction of enzymes among themselves.
During the process of slow fermentation, the leaves are not damaged.
According to the degree and method of leaf fermentation, tea is divided into five groups:
- white tea ;
- green tea
- Oolong tea;
- Red tea;
- Black tea.
After the collapse of the Soviet Union, tea production in Russia remained only in the Krasnodar Territory.
Having survived the crisis of the 90s, tea production in this area began to stabilize, but the quality of products remained low and volumes also did not reach the previous level. However, local tea processing plants and tea packing factories in Adler and Dagomys did not stop their activities; the Russian company Krasnodarchay was preserved.
Despite the fact that the soil and climatic conditions are far from optimal for growing tea, in the Sochi region tea plantations occupy about 1.5 thousand hectares of area. Over 4,000 tons of tea leaf are harvested here annually.