The sweet taste is a kind of taste that human instinct like, it gives us pleasure. We will also show a good impression for the sweet taste of tea". “Back sweet mellow”, “Back sweet”, this kind of words are always used to express the high quality of tea.
The current study of sweet taste is clear. Sweet substances in tea in addition to polysaccharides, there are some amino acids, catechin, tea red pigment. Tea contains polysaccharides and oligosaccharides, sweet taste in the tea mainly contains glucose, galactose, mannose, fructose, sucrose, and maltose formed in the process. In the tea tree, these carbohydrates increased with the growth of leaves, that is sugar content of mature leaves higher than tender leaf; In the spreading drying process, many monosaccharides was consumed as respiratory substrate. But disaccharides and oligosaccharides and polysaccharides can be hydrolyzed into monosaccharides, its content will increase; And in the subsequent high temperature process, that will happen the Maillard reaction and caramelization, and again consume a portion of the sugar. These carbohydrate after complex experience, after we brew th tea, it is the sugar we can taste. Therefore, in the finished tea, sometimes soluble sugar content of tea with high tenderness will be higher than low tenderness tea, but there's no rule.
For the mysterious "back to sweet", our ancient people began to pay attention to this feeling. Good tea often comes with "back to sweet", the strength and durability of "back to sweet" is often used as an indicator of good tea. "Back to sweet " and "promote the secretion of saliva or body fluid" also often linked in the practical experience. This is a more mysterious experience, but it is undeniable that “back to sweet” give us a pleasant experience. Relative to the inlet immediately showed the sweet taste, it is more dramatic for the after-taste of "All sufferings have their reward(苦尽甘来)", it is more linked together with the good quality of tea.
For "back to sweet", different people have different viewpoint.
Some people think this is an illusion of the oral cavity, that is a type of contrast effect:
It is “all sufferings have their reward(苦尽甘来)”. The tea soup contains a lot of bitter taste ingredient of caffeine and chlorogenic acid and catechin. These ingredient lead to bitter when the tea soup enter the mouth, but the human senses will be automatically adapted to the bitter taste. Wait until these bitter substances into the stomach, the senses still retain the illusion, so that will produce a sweet feeling. But the kind of statement don't have persuasive: One, if just is a type of contrast effect, the more bitter tea should be more obvious for the "back the sweet", but it is not the case, a lot of tea we just feel the bitter taste, but don't feel a trace back to sweet; Two, in a good tea, its bitter feeling is not strong when the tea soup enter the mouth, but its back to sweet is still obvious and lasting. But we cannot reject the true existence of this feeling. If we drink tea soup that have obvious bitter taste, immediately drink a white boiling water, you will find that the water will become sweet, this is a contrast effect. Perhaps this delusion is only a factor causing the back to sweet.
Some people think this is a result of astringent taste transformation:
Tea polyphenols caused a sense of astringent taste of the mouth in the tea. But the sense won't last forever. when the tea polyphenols bitter taste off, convergence transformation, oral local muscle began to recover, so that show a feel of promote the secretion of saliva or body fluid.