You, who love tea, must have treasured a lot of good tea. But you may not know, they may be deteriorating. The deterioration of tea is due to the change of some chemical components inside, but it will be obviously reflected in the appearance. How to judge from the appearance that your tea is deteriorating?
1、 The significant browning of green tea indicated that chlorophyll was decreasing
Chlorophyll is an important component of green tea appearance color, soup color and leaf bottom color. In the tea, the content of chlorophyll determines the color and content of tea, so tea is green.
But chlorophyll is very unstable, especially vulnerable to light and heat. When storing tea leaves, if the light and heat are not suitable, the chlorophyll will be de magnesium transformed into magnesium free chlorophyll. When the proportion of this kind of magnesium free chlorophyll exceeds 70%, the green tea will appear obvious browning.
2、 The browning of tea soup and the deterioration of taste indicate the oxidation and polymerization of tea polyphenols
Tea polyphenols are the most important components that affect the color and taste of tea soup. The taste concentration, astringency and freshness of tea soup are determined by the content of tea polyphenols.
The content of tea polyphenols in green tea is very high, but if it is not stored properly, the tea polyphenols are easily oxidized and polymerized to form brown substance, which makes the tea soup brown. Moreover, the brown substance will further react with amino acids, making the tea soup taste inferior.
If it is found that the taste of tea becomes lighter, the color of soup turns yellow, the aroma becomes low, and even gradually loses its original quality characteristics, then it indicates that the tea polyphenols have undergone serious oxidative polymerization, and the proportion of effective components in tea has been seriously out of balance.
When making black tea, enzymes should be used to catalyze the reaction of tea polyphenols to produce theaflavins and thearubins to obtain the best color and taste of black tea. However, if not stored properly, theaflavins and thearubins will continue to oxidize and polymerize to form high polymers which are very unfavorable to the color and taste of the soup.
3、 Green tea brown, taste not fresh, indicating that vitamin C is being oxidized
Vitamin C is a health care component in tea, which also has a very important impact on the quality of tea. High quality green tea, vitamin C content is very high. But vitamin C is very easy to oxidize, so the higher the green tea, the more difficult it is to keep.
After vitamin C is oxidized, the nutritional value of tea will be reduced, the color will turn brown, and the amino acids will be reduced accordingly, and the freshness of tea soup will be greatly reduced.
Therefore, the storage of green tea, it is very important to keep vitamin C from being oxidized. If the vitamin C in green tea is retained more than 80%, the quality of green tea will hardly change, and once it drops to below 60%, the quality of green tea will deteriorate obviously.
4、 Tea produced rancid odor, indicating that lipids were hydrolyzed and carotene was oxidized
Tea contains about 8% of the lipid substances. If it is not preserved properly, it is easy to hydrolyze the lipid substances to produce aldehydes and ketones, which will produce the smell of rancidity.
There is also a kind of yellow carotenoids in tea, which has certain light absorption properties and is easy to be oxidized. When carotenoids are oxidized, they produce an odor similar to that produced by stored carrots, which makes the tea soup taste worse.
5、 Tea loses astringency, loses freshness and becomes tasteless, indicating that amino acids are declining
Amino acids are the main substances that give the fresh and pleasant taste to tea soup, which is particularly important for green tea. Therefore, the content of amino acids is the main indicator to judge the quality of green tea.
The changes of amino acids were mainly affected by the changes of other substances in tea. The oxidized products of tea polyphenols will combine with amino acids to form a dark substance, which makes the tea lose its astringency, freshness and tastelessness. If the tea is not stored properly, the longer the storage time, the more amino acids will decrease.
6、 The aroma gradually declined with time
Generally speaking, the longer the tea is stored, the lower the aroma will be and the stronger the stale taste will be. Especially for new tea, the unique fragrance will be lost. It was found that the main components of the new tea aroma of green tea decreased significantly with the passage of time.
The fragrance of tea can be divided into new tea fragrance and old tea fragrance, which are the relationship between the ebb and flow. For some tea, the longer the storage time, the longer the storage time. For most tea, fresh and fresh fragrance is the most important feature, so it is very important to prevent the loss of fresh flavor.
In short, to buy a good tea, but also have a good storage method. If not stored properly, good tea will turn into bad tea. As for how to store tea scientifically, we will introduce it in detail in the following article.
Now, go and have a look at your precious tea. Are they OK?