1. Tannin is an acidic substance that mainly originates from grape skins and seeds.

2. Red wine is to retain the grape skins fermentation, in the fermentation process, the wine will also draw a certain amount of tannin substances from the oak.

3. In terms of chemical structure, the tannins that are infiltrated by the grape skins are "condensed tannins", and the tannins that are drawn from the oak barrels are "hydrolyzed tannins".

4. The tannin content is not directly proportional to the quality of the red wine, and it is not the case that the higher the tannin content, the better the wine.

5. A good glass of wine should be the result of the harmonization and balance of alcohol, acid and tannin.