What do you mean by ‘returning to Gan’
Sweet is a natural sensory effect that people often have when drinking tea and a positive evaluation of the taste of excellent tea. The aftertaste effect is a specific taste formed mainly by the combined action of bitterness and sweetness. It is a taste that is sweet and slightly bitter when tasted, has a long aftertaste in the mouth, and gradually surpasses bitterness in sweetness over time, ultimately ending in sweetness. The sensory experience is mainly manifested as “slightly bitter upon entry, with a clear and sweet aftertaste”, “bitter with a hint of sweetness upon entry, followed by a gradual disappearance of bitterness, a longer sweetness, and a longer aftertaste of sweetness than bitterness”.
However, not all plants have both flavors at the same time. For example, bitter melon and lotus seeds are bitter and unwilling to be bitter, while licorice has a sweet but not bitter taste. The production of a sweet taste in tea soup is usually based on a bitter taste, followed by the production of a sweet taste. Good tea often has a “aftertaste”, and the strength and persistence of aftertaste are also considered as one of the indicators to judge whether it is a good tea. Compared to the immediate sweetness upon entry, this change of “bitterness over sweetness” is more dramatic and is more associated with the quality of good tea.
What are the reasons for the “sweet aftertaste” of tea soup?
Some say it is the result of the transformation of astringency. Professor Wang Yuefei, Deputy Director of the Department of Tea Studies at Zhejiang University, expressed his views in his edited book “Tea Culture and Tea Health”: “Tea contains tea polyphenols, which can bind with proteins to form an impermeable membrane in the oral cavity. The contraction of local muscles in the oral cavity causes a bitter sensation, making us feel that the tea we just drink will have a bitter taste. If the content of tea polyphenols is appropriate, a membrane with only one or two single or double molecular layers can be formed. This membrane thickness is moderate, and there is a bitter taste in the oral cavity at the beginning. Later, after the membrane ruptures, the local muscles in the oral cavity begin to recover, and the convergence transformation occurs, presenting a feeling of returning sweetness and producing saliva. So Professor Wang Yuefei believes that “returning sweetness” is the result of the combination of tea polyphenols and proteins.
Another theory suggests that “returning sweetness” is an illusion in the mouth, known as the “contrast effect”. In their article “The Relationship between Different Taste Qualities and Stimulants” published in 1979, Professor McBurney and Bartoshuk proposed that “sweetness and bitterness are relative concepts. When you taste sweeteners such as sucrose, you will find that water is a bit bitter, while when you taste bitter substances such as caffeine and quinine, you will feel that water is sweet.” This phenomenon is a comparative effect, so many people also believe that this illusion may be one of the factors causing aftertaste. However, the stronger the bitterness intensity of tea soup, the higher the aftertaste intensity. Some teas cannot wait for aftertaste after the bitterness we feel. Some teas are not very bitter when they enter the mouth, but their aftertaste is not significant. Gan is obvious and persistent. The academic community is also conducting systematic and in-depth research on the mechanism of “returning Gan”, and there is currently no absolute consensus, But some scholars’ research and viewpoints can provide us with reference.
Many scholars and experts have experimentally proven that there are some components in tea soup that may cause “aftertaste”:
1. Tea polyphenols and total sugars: Electronic tongue (an intelligent recognition electronic system developed to mimic the human taste mechanism) is used for tea soup taste analysis. Research has shown that there is a significant positive correlation between the bitterness and aftertaste of tea soup, and the two complement each other; There is a significant positive correlation between the content of tea polyphenols and total sugar and the strength of the sweet aftertaste of tea soup, indicating that within a certain concentration range, both tea polyphenols and total sugar contribute to improving the strength of the sweet aftertaste of tea soup.
2. Flavonoids: Although there have been no reports in the tea industry that flavonoids can produce “aftertaste”, there are reports that flavonoids are substances that produce aftertaste in olives. The bitter taste of olives comes from its special chemical components, such as oleuropein, flavonoids, and polyphenolic compounds, among which flavonoids are higher in content than other foods. The bitter substances in bitter gourd are bitter gourd saponins and bitter gourd glycosides; The bitter substances in Kuding tea are also glycosides and a small amount of flavonoids. Glycosides only exhibit bitter taste, so when eating bitter melon, only a bitter taste is felt, and there is almost no feeling of returning sweetness. The taste expression of flavonoids is very unique, showing a bitter taste when first tasted, but after a period of time, a natural sweet taste can be felt. The flavonoids contained in olives are the main reason for their ability to regain sweetness, and the higher the flavonoid content, the more pronounced the regain and the richer the aroma. The flavonoids in tea are about 3% -4% of the dry matter. However, the mechanism of flavonoids returning to sweetness is still under study and not very clear.
3. Organic acids: Organic acids in tea stimulate salivary glands to secrete and produce a feeling of “producing saliva and returning sweetness”. There are many types of organic acids in tea, with a content of about 3% of the total dry matter. The organic acids in tea are mostly free organic acids, such as malic acid, citric acid, succinic acid, oxalic acid, etc. Other organic acids may also be formed during the tea making process. During the withering and greening process of tea leaves, the content of organic acids will increase.
4. Carbohydrates: Tea soup contains polysaccharides, which do not have a sweet taste but have a certain viscosity, so they may be retained in the mouth. And saliva contains salivary amylase, which can catalyze the breakdown of starch water into maltose, which has a sweet taste. Enzymes require a certain amount of time to break down polysaccharides, and this reaction time difference creates a feeling of “returning sweetness”.
Many tea drinkers always show a favorable impression of the “sweetness” in tea. In terms of enjoyment in drinking, a rich, refreshing, and non bitter tea flavor can most evoke pleasant emotions. However, for many old tea lovers who love to drink tea, the tea that can “taste bitter and sweet” is the true good tea. Although the mechanism of “returning sweetness” is currently unclear, this does not prevent us from pursuing the pursuit of “sweetness after bitterness” when tasting tea – because tea is also a part of life.