When drinking tea, the sensitive tongue quickly transmits the flavors in the tea soup to the brain, creating a sense of satisfaction or enjoyment. But what substances are responsible for these tastes? Let's explore the science behind drinking tea!
The flavor compounds in tea soup can be categorized as: sugars, amino acids, phenolic substances and their oxidation products (mainly tea polyphenols), purine alkaloids (primarily caffeine), organic acids, and tea saponins. Among these, tea polyphenols, amino acids, and caffeine have the greatest impact on tea leaves quality. The taste of tea is a comprehensive response of human taste organs to the flavor components in tea. Therefore, the amounts of various flavor components and changes in their proportions all affect the taste of the tea soup.
1 Astringency — Phenolic Compounds and Their Oxides
Among the phenolic compounds in tea soup, catechins are the most abundant. Esterified catechins taste bitter and astringent, with a strong收敛性. The astringent sensation upon sipping tea soup is mainly caused by esterified catechins reacting with proteins in the oral mucosa to form impermeable substances, causing收敛. From a sensory perspective, astringency is also刺激触觉神经末梢产生的.
2 Bitterness — Purine Compounds (Mainly Caffeine)
Among the purine compounds in tea leaves, caffeine is the primary flavor substance, presenting bitterness. Due to its volatility when heated, its content decreases significantly during multiple infusions. Caffeine stimulates the central nervous system, activates cerebral cortex cells, and stimulates gastric juice and bile secretion, making it a key substance driving people's preference for tea.
Anthocyanins in tea soup are also a source of bitterness. When the anthocyanin content in tea soup exceeds its threshold, the tea soup has a noticeable bitter taste. A 150ml tea soup containing 15mg of anthocyanins will have a distinct bitterness. Purple buds contain 1% or even more anthocyanins. Summer tea, exposed to strong sunlight, has high anthocyanin content and more purple buds, which is why summer tea is often more bitter and astringent, resulting in poorer quality.
3 Freshness — Amino Acids
Green tea should taste mellow, sweet, and refreshing. The sweet and refreshing口感 are related to the amino acids in tea leaves. There are many types of amino acids in tea, each with different characteristics. The highest content is theanine, which is unique to tea. Other amino acids with relatively high content include glutamic acid, aspartic acid, arginine, glutamine, and asparagine. In terms of the taste characteristics of each amino acid, not all amino acids present鲜味; most taste sweet or bitter.
According to reports, most L-type amino acids taste bitter, with a few tasting sweet or鲜; D-type amino acids all taste sweet. In nature, the amino acids that constitute proteins are L-type. Therefore, amino acids obtained from the hydrolysis of proteins in tea mostly impart bitterness to the tea soup. Although the configuration of free amino acids in tea is difficult to determine, it is certain that they contribute not only鲜味 but also bitterness and sweetness to the tea soup. The combination and interaction of these different taste qualities constitute the various flavor characteristics of tea soup.
4 Sweetness — Sugars and Other Substances
The sugars that present sweetness in tea soup are mainly soluble sugars like monosaccharides and disaccharides found in tea leaves. The sugar content is not high. However, due to the different taste thresholds of the human taste organs for sweet and bitter flavors and the different locations where these tastes are perceived, the small amount of sugar in tea soup can create a stronger sensation after the initial slight bitterness. The协同作用 of sweetness and bitterness produces the pleasant feeling when tasting tea. Pectin and glycosides of phenolic substances in the tea soup also play a role in forming its taste. Water-soluble pectin can give the tea soup a thick and mellow口感.