I. The Main Components of Tea Leaves and the Composition of Tea Soup Flavor
The main components in tea leaves are amino acids, alkaloids, and tea polyphenols.
Amino acids, which have a fresh and brisk taste, are important components constituting the flavor of tea soup;
The main component of alkaloids, caffeine (also called theine), has a bitter taste and is also an important component constituting the flavor of tea soup;
II. Explanation of the Taste Transformation from Bitterness/Astringency to Sweet Aftertaste and Saliva Induction
The primary substances forming the bitter taste of tea soup are caffeine and tea tannin. The primary substance forming the astringent taste of tea soup is tea tannin. The bitterness of caffeine does not linger long on the tongue; it can dissipate quickly. This bitterness is the foundation of the "sweet aftertaste." When the bitter-tasting substances no longer linger on the tongue and dissipate, it can lead to a change in taste perception, creating a taste "illusion" that presents as a sweet aftertaste. This illusion should be a reflection of a basic human need. Fortunately, tea tannin can slow down the effect of caffeine, causing this instinctive illusion to linger in the mouth and on the tongue. The often-heard phrases "tea addiction" or "getting hooked on tea" stem from this reason.
The astringent sensation in tea soup is because it contains tea tannin. Tea tannin has a收敛性 (astringent) effect, which can coagulate the proteins of single-celled bacteria in the mouth, thereby causing local muscles in the mouth to contract. When the bitter and astringent taste of tea tannin dissipates and its收敛性 transforms, the local muscles in the mouth begin to recover, presenting the sensation of saliva induction (生津). If the收敛性 of tea tannin is too strong, the intense astringency strongly stimulates the taste buds, lingering unpleasantly on the tongue, often accompanied by bitterness causing discomfort. This kind of bitterness and astringency is mainly formed by improper processing of the tea leaves and represents a significant flaw for the tea.
The physicochemical properties of caffeine are relatively stable and basically do not change much during tea processing. In tea soup, the combination of tea tannin and caffeine moderates the physiological effects of caffeine on the human body. Tea tannin can slow down and prolong the stimulating effect of caffeine. The often-heard sayings "tea refreshes the mind" and "tea dispels drowsiness" stem from this reason.
III. The Taste of Tea Soup and Differences in Personal Evaluation
The main flavor substances in tea soup are amino acids, alkaloids, and tea polyphenols. Differences in the content of these three flavor substances lead to variations in the overall taste profile.
The bitterness/astringency of tea soup and its sweet aftertaste/saliva induction are interconnected and inseparable, much like the concept of mutual generation and restraint in the Five Elements theory.
Without generation, things cannot originate and grow; without restraint, things have no constraint and cannot maintain normal harmonious relationships.
Only by maintaining a dynamic balance of mutual generation and restraint can things develop normally.
When we drink tea, we cannot determine the content of the three flavor substances—amino acids, alkaloids, and tea polyphenols—let alone determine the proportion these three flavor substances should follow.
Personal sensory evaluation criteria:
If there is bitterness upon entering the mouth, the bitterness should be acceptable to one's personal taste, and it should not linger long on the tongue but dissipate and lead to a sweet aftertaste; if there is astringency upon entering the mouth, the astringency should not cling to the upper palate, teeth, or lips, and it should not linger long on the tongue but transform and induce saliva.
What we often call personal taste is actually a subjective feeling, a comprehensive subjective perception formed by the stimulation of the tea soup on an individual's sense of taste, smell, and touch. Therefore, tea appreciation also varies from person to person.
Good tea is when the strong, fresh, and brisk original charm of the tea soup overpowers the bitterness and astringency of the soup, and the bitterness and astringency transform before one even becomes aware of them. But this lack of awareness lies in human subjective perception. The often-heard saying "good tea requires fate" stems from this reason.