This is produced by yeasts which transform sugar from grapes into alcohol. 17 g of sugar per liter of must produces around 1 degree of alcohol. (200 g of sugar per liter of grape must is the minimum amount required to obtain a wine at 12° alcohol, as is often the case in Bordeaux). After water, it is the second most plentiful ingredient in wine, and brings a warm character that compensates for the acidic sensation.