The reason why tea is deteriorated and aged is that various components in tea will be oxidized, hydrolyzed and transformed. Among them, the most influential factors are temperature, moisture, oxygen and light, as well as the interaction among these four factors.
Temperature affects the rate of oxidation and polymerization of various components in tea. The higher the temperature, the faster the reaction. The browning rate of tea leaves increases 3-5 times when the temperature increases by 10 ℃.
Therefore, in order to effectively prevent the browning of tea leaves, it is necessary to keep them at a temperature below 10 ℃. If the temperature reaches – 20 ℃, it can almost completely prevent the tea from aging. The rate of leaf browning will increase 3-5 times.
The higher the temperature, the higher the enzyme activity in tea, the faster the oxidation and polymerization of tea polyphenols, theaflavins and thearubin, the faster the aging of new tea and the fast quality loss.
Many friends may think that the drier the tea leaves are, the better they are preserved and the less likely they are to deteriorate. Tea is one of the food, for food, absolute drying will make all kinds of ingredients directly exposed to the air and be quickly oxidized.
The results show that when the moisture content of tea is about 3%, the relationship between tea components and water molecules will be monolayer. Water molecules form a protective film to isolate tea from the air and prevent the components in tea from being oxidized.
However, once the water content increases, the opposite effect will occur. Water molecules will become a kind of solvent, which makes the various components in tea undergo intense chemical changes. Especially when the moisture content is more than 6%, the change will be very intense. As a result, chlorophyll is rapidly degraded, tea polyphenols are oxidized automatically, and the rate of tea color deterioration is increasing.
The characteristic of oxygen is that it can combine with almost all the elements and become oxides, and the material elements in tea are no exception.
The particularity of tea oxidation is that tea contains active enzymes, which accelerate the oxidation to become intense. So we emphasize the importance of low temperature, because low temperature can inhibit the activity of enzymes. When the enzyme loses its activity, although the tea will still be oxidized, the rate will be much slower.
The oxidation of catechins, vitamin C, tea polyphenols, theaflavins, thearubins, etc., as well as the aging substances produced by lipid oxidation, are closely related to the existence of oxygen. Therefore, in order to prevent rapid oxidation of tea, it is necessary to isolate oxygen.
Light, in fact, is an energy. The energy of the tea will be accelerated by the light, so it will not promote the chemical reaction.
Once the tea is exposed to strong light, especially ultraviolet light, the chlorophyll will quickly fade, and some substances with aging characteristics will be generated. For green tea, light can oxidize fatty acids into aldehydes, which will deteriorate the aroma and produce a strong sunlight flavor.
Understand the four main factors that affect the deterioration of tea. Now, you can also design a scientific and safe tea warehouse for your good tea. That is: the temperature should be at least below 10 ℃, and the moisture content of tea should be kept at about 3%. Try to isolate oxygen and avoid direct sunlight.
This is the most tea, especially green tea storage should follow, but can not be generalized, individual special tea, need to adjust according to the actual situation.