Whether it is green tea, black tea, oolong tea, or black tea, when making tea, especially when using the first brew of the gaiwan, some small white bubbles often appear on the surface of the tea soup. Some were joined together, densely packed like small beads, while others were just a few close together and then shattered.

Should the foam on the surface of the tea soup be scraped clean when making tea?

When tea leaves are brewed with hot water, a lot of foam sometimes floats, and after the brewed tea is cooled, a thin film may form on the surface. Some people are concerned that these tea foams and tea films are pesticide residues or a sign of poor tea quality. In this regard, experts in the field of food science explained that the substance that makes tea foam is tea saponin, which has an antibacterial effect, while the tea film is composed of oxidized tea polyphenols, calcium carbonate and other substances, and consumers do not have to worry or question their safety when drinking tea.

Professor Liu Shaowei, a member of the expert group of the Shanghai Food Safety Research Association, said in an interview with a reporter from China Consumer Daily that the foam produced when tea is brewed is mainly tea saponins and proteins. Among them, tea saponin, also known as tea saponin, is a compound that is insoluble in water. According to the results of current scientific research, tea saponin has antibacterial effect and can inhibit fat absorption. However, the amount of tea saponins in a cup of tea is too low to really count on them to have an antibacterial effect.

As for whether there is foam in the tea soup and the amount of foam, it mainly depends on the variety of tea trees and the shape of the finished tea. The tea saponin content of different tea varieties is high or low, and the shape of tea leaves is also different, which may affect the amount of tea foam.

Generally speaking, multi-milli varieties (the surface of the tea is full of hair) tea, such as some Jin Jun Mei, Fuding Dabai, Fuding Dahao, etc., are basically made of tea buds, tea saponin, tea polyphenols and other content is higher, if the tea is kneaded hard, resulting in the precipitation of the contents and sticking to the surface of the tea, it is easy to produce foam when brewing.

In addition, some tea raw materials are finely crushed, such as red broken tea, or broken tea crumbs produced during the packaging and transportation of tea leaves, and the contents of the tea will be effectively released after brewing, which will produce foam.

Similar to the tea foam formed by tea saponins, the tea film formed on the surface of tea after cooling is mainly composed of oxidized tea polyphenols, calcium carbonate and other forms of salt. The hardness of water, PH value, tea concentration and brewing temperature are all factors that affect the formation of tea film.

For example, calcium ions and bicarbonate ions in water are the key factors that induce the formation of tea films, and as long as both are present at the same time, tea films will be produced. And if you use completely pure water to make tea, there will be no tea film after cooling.

The variety of tea also affects the formation of the tea film. Generally, black tea is more likely to form a tea film, while white tea, yellow tea, green tea or lightly processed oolong tea basically does not form a tea film after cooling, because black tea has a longer fermentation time and a higher degree of oxidation than other varieties of tea.

As for some people's concern that tea foam or tea film may be pesticide residues, Liu Shaowei explained that 98% of the tea pesticides allowed to be used in the mainland are fat-soluble substances, and they are not soluble in water, so it is impossible to form foam or form a tea film after cooling. At the same time, there are no experimental studies to prove a link between pesticide residues and tea film or tea foam.

In short, it is completely normal for these small bubbles to appear when making tea. Since it is unsightly

, you should try to scrape it off, but you don't need to have obsessive-compulsive disorder, you must completely scrape it off 100%.

There are more first brews, but there are still more or less second brews, third brews, and even after multiple brews. As long as it doesn't affect our drinking experience, we don't have to worry too much about it.