We often hear from some tea friends that they can’t sleep after drinking tea at night. In fact, including the author himself, just began to learn to drink tea, also often insomnia, especially after drinking raw tea at night. Later, I learned from the tea book that this is because tea contains a class of things called alkaloids, alkaloids can make nerves excited, too excited, naturally can’t sleep.
There are three kinds of alkaloids in tea: caffeine, theobromine and theobromine. The content of caffeine is the highest, about 2% ~ 5%, the content of theophylline is about 0.002%, and the content of theobromine is about 0.05%. It can be seen that caffeine is the main reason for its action, so we can understand caffeine through the following key issues.
1、 What is caffeine?
Caffeine is a kind of alkaloids, which only comes from the biological kingdom. These substances contain a common nitrogen element, so it is also known as nitrogen-containing organic compounds, which widely exist in the plant kingdom.
Caffeine is an important substance in the nitrogen cycle of tea plants. Like protein and amino acids, caffeine is closely related to the growth and metabolism of tea plants. The content of young shoots with vigorous metabolism is more, the content of good quality tea is higher, and the content of coarse and old tea is lower. The caffeine content of tea plants grows faster in which season.
2、 All contain caffeine. Why can tea taste bitter but not coffee?
Caffeine itself is bitter, and it’s so bitter that it can hardly turn into sweet. Coffee, one of the three major drinks in the world, also contains more caffeine. However, there is a strange phenomenon: coffee is really bitter, while tea is only temporary bitter, but it can return to sweet later. All contain caffeine. Why can tea taste bitter but not coffee?
This is because the main content of tea, not only caffeine, but also tea polyphenols, protein, amino acids, polysaccharides and so on. After caffeine forms complex with tea polyphenols and oxidation products, the bitterness and astringency will be reduced, and a kind of substance with fresh taste will be formed, which will turn back to sweet.
At the same time, caffeine reacts with catechins, theaflavins, thearubins, polysaccharides, proteins and amino acids to form a substance, which is the main component of the milk curd material produced after the black tea soup is cooled. It is commonly said that black tea is “cold and muddy”. In fact, the tea with obvious “cold after muddy” just means that it is a good tea, which shows that the content of catechin, theanine and caffeine is higher.
3、 What kind of tea is high in caffeine content?
The content of caffeine in tea has its own distribution law
(1) The tenderer the tea plant is, the more caffeine it contains. On the contrary, the older the tea plant is, the less caffeine it contains.
(2) The content of caffeine in large leaf species was higher than that in medium and small leaf species.
(3) In summer, the temperature is higher, the growth of tea plant is the most vigorous, and the caffeine content of summer tea is the highest. Tea polyphenols are the same, so summer tea is often bitter and astringent.
(4) When the temperature reaches 178 ℃, caffeine begins to turn into gas sublimation. Therefore, the content of caffeine in the tea which is stir fried at high temperature for a long time or with the process of volatilization is relatively low, and the caffeine content will be reduced in the process of tea baking.
In particular, although caffeine is an important component of tea taste, it does not mean that the more caffeine is, the better. For some people, it is not even suitable to drink drinks containing caffeine.
4、 What effect does caffeine have?
After brewing, 80% caffeine will be dissolved in the tea soup. The main functions of caffeine are as follows:
(1) Excitatory effect. Caffeine can stimulate the central nervous system, enhance the excitation process of cerebral cortex, so as to make the brain clear, help thinking, eliminate fatigue, and improve work efficiency, which is the same as coffee.
(2) Diuretic effect. Caffeine can stimulate blood movement center, relax renal blood vessels, increase renal blood flow and improve glomerular filtration rate to achieve diuretic effect. For cardiac edema, water retention and other symptoms have a significant effect, but also on renal tuberculosis and kidney stones have good prevention and treatment effect.
(3) It can strengthen heart, relieve spasm and relieve asthma. Caffeine can relax coronary artery, promote blood circulation and relax bronchial smooth muscle, so it can relieve spasm, relieve asthma and treat bronchial cough and asthma.
(4) Toxic effect of jiejiujing. Caffeine can improve the liver’s ability of metabolism of substances, enhance blood circulation, discharge alcohol from the blood, and relieve and eliminate the stimulation caused by alcohol.
Because the caffeine in tea can stimulate the brain and stimulate the heart, some special people, such as the elderly, pregnant women, young children, heart patients and neurasthenia patients, can only not drink or drink less tea with high caffeine content.