People who know wine all know that a bottle of good wine must have one of the basic characteristics of "balance." So what is the balance? Balance refers to the wine, alcohol, tannin and acidity must form a harmonious whole, the acidity of which constitute the skeleton and the soul of the wine, if the wine doesn’t have acidity, or even cannot be called wine, these acidity material on the one hand to give the wine is fresh and refreshing feeling, on the other hand but also have effect on killing bacteria. They exist in the free acid state, including tartaric acid, malic acid, citric acid, succinic acid, lactic acid and acetic acid. Where these "acid" are come from? In fact, the wine "acid" comes from two parts; one part from the grape itself, such as tartaric acid, malic acid, citric acid, the other part is derived from the process of the succinic acid, lactic acid, acetic acid, etc.
Tartaric acid is a carboxylic acid, present in many plants, grape certainly no exception, and the content is high, is the most important component of wine. Grape varieties and soil structure determines the content of tartaric acid in grapes. Grapes in the flowering period, grape flowers and berries contain a lot of tartaric acid. In the ripening process, with the plant respiration, tartaric acid is not consumed, so it is consistently exists in the ripening process. In wine, less than half of tartaric acid is exist independently, and exist mostly in the form of tartrate.　　
In addition to containing tartaric acid in grapes, there are malic acids, and the content is the same as tartaric acid, not low. In vine, malic acid participates in the growth of grape, play the role of maintaining vine health. The content of malic acid also depends on the grape variety. In the course of grapes turn to mature, malic acid will be gradually consumed, but it does not mean that will be fully consumed, usually to harvest when the concentration will drop to 1-9g/L. When malic acid is consumed too much, it means that grapes are becoming over-ripe grapes or getting old. Therefore, at this time, winemaker must add acid in the winemaking process.　　
Grapes, in addition to containing tartaric acids and malic acids, there is a citric acid. However, compared to other fruits, its content is much less in the grapes.
It can be said, tartaric acid, malic acid, and citric acid is the main source of acidity in wine, in addition to those contained in the grape itself sour substances, there is produced in the brewing process of "acid."
Acidity in wine, of course, in addition to different because of different varieties and winemaker, it is also concerns to grapes growing climatic conditions and oak aging and other factors. However, no matter what kind of breed, which region, which type of wine, are decidedly inseparable from the "acid"!