Some people think that tea itself has been processed by a special process
and will not deteriorate. In fact, otherwise, the deterioration and aging of
tea are the result of oxidation, degradation and transformation of various
chemical components in tea. After the production is completed, it will
naturally age for a long time. Of course, this process of Pu-erh tea is
different from other teas. For most teas, the environmental conditions that
affect it most are: temperature, moisture, oxygen, light, and their
interactions.
1. Temperature.
As a chemical change, tritium oxidation and polymerization are closely related to the temperature. The higher the temperature, the faster the reaction speed. Various experiments have shown that the rate of browning of tea leaves increases 3 to 5 times for each 10 ° C increase in temperature. If the tea leaves are stored below 10 ° C, the browning process of the tea leaves can be better suppressed. But it can be stored frozen at minus 20 ℃, which can almost completely prevent aging. Studies also suggest that the recovery of residual polyphenol oxidase and peroxidase activity in black tea is positively correlated with temperature. Therefore, when tea leaves are stored at a higher temperature, the enzymatic oxidation and auto-oxidation of unoxidized flavanols, further oxidation of theaflavin, and the polymerization rate will be greatly accelerated, thereby accelerating the aging of new tea and the quality of tea Loss.
1. Temperature.
As a chemical change, tritium oxidation and polymerization are closely related to the temperature. The higher the temperature, the faster the reaction speed. Various experiments have shown that the rate of browning of tea leaves increases 3 to 5 times for each 10 ° C increase in temperature. If the tea leaves are stored below 10 ° C, the browning process of the tea leaves can be better suppressed. But it can be stored frozen at minus 20 ℃, which can almost completely prevent aging. Studies also suggest that the recovery of residual polyphenol oxidase and peroxidase activity in black tea is positively correlated with temperature. Therefore, when tea leaves are stored at a higher temperature, the enzymatic oxidation and auto-oxidation of unoxidized flavanols, further oxidation of theaflavin, and the polymerization rate will be greatly accelerated, thereby accelerating the aging of new tea and the quality of tea Loss.
2. Moisture.
Food theory believes that absolute dry food is susceptible to oxidation by oxygen in the air because various components are directly exposed to the air. And when water molecules are combined with food ingredients by hydrogen bonding and are in a single molecular layer state, it is like covering a surface of food ingredients with a protective film, thereby protecting the protected substance and slowing down the oxidation process. It is considered that when the moisture content of tea is about 3%, the composition of tea and water molecules are almost in a single-layer molecular relationship. Therefore, lipids can be better isolated from oxygen molecules in the air to prevent oxidative deterioration of lipids. However, when the moisture content exceeds this level, the situation is completely different. At this time, the moisture not only can not function as a protective film, but also functions as a solvent. Especially when the moisture content in tea leaves exceeds 6%, the chemical changes become quite drastic. One of the characteristics of the solvent is that the concentration of the dissolved substance diffuses to the left and right, thereby intensifying the reaction and accelerating the deterioration. One of the main manifestations is that chlorophyll will be rapidly degraded, and the process of automatic oxidation and enzymatic oxidation of tea polyphenols and the further polymerization into polymers will be greatly accelerated, especially the speed of color deterioration will increase linearly.
3. Oxygen.
Oxygen can be combined with almost all elements to make it an oxide. Most of the ordinary air is molecular oxygen, and its reactivity is not very strong. However, when it is combined with other substances, especially the presence of enzymes that can promote the reaction, this oxidation can become very intense. In the case of enzyme inactivation, various compounds can still be oxidized by molecular oxygen, but only at a much slower rate. The automatic oxidation of catechins in tea, the oxidation of vitamin C, the oxidation of tea polyphenols catalyzed by residual enzymes of tea polyphenols, and the further oxidative polymerization of theaflavin are all related to the presence of oxygen, and the oxidation of lipids produces aging. Taste substances also have the direct involvement and role of oxygen.
4. Light.
Essence of light is an energy. Light irradiation can increase the energy level of the entire system, which has a very adverse effect on tea storage and accelerates the progress of various chemical reactions. Light can promote the oxidation of plant pigments or lipids, especially chlorophyll, which is susceptible to light and fades, and ultraviolet rays are more obvious. Studies have shown that compared with light exposure during tea storage, 1-pentene-3-ol, pentanol, octenol, heptadienal, octanol, and four unknown components in tea have increased significantly. In addition to the components that usually increase due to deterioration, pentanol, octenol, and three unknown components are considered to be the characteristic components of aging that are unique to light.
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