A naturally occurring grape acid that decreases with ripening. It is one of the principal components of a wine's total acidity. If a wine is too acidic (the grapes hadn't ripened fully), it can be de-acidified by a malolactic fermentation, in which the malic acid will get metabolized by malolactic bacteria and excreted as lactic acid.
A naturally occurring acid found in apples, cherries, grapes grown in less sunny regions, and certain other fruit. It is the presence of malic acid, along with Bacillus Gracile, which sometimes produces malolactic fermentation.