Malic Acid is one of two important natural acids found in grapes that make wine taste so fine. It’s in all fruits, and is responsible for a complicated chain of reactions.
Malic acid is sour or tart-tasting acid when young. As fruit ripens, malic acid breaks down until all you’re left with is overripe fruit with just a trace of malic acid.
In winemaking, malolactic fermentation is introduced into some wines to convert malic acid to lactic acid, which is sweeter. This not only reduces a wine’s tartness, it adds complexity to the flavor and body to the wine.
Malic acid is also found in food products, like potato chips. Sour candies often use it for an intense sour flavor. Vinegar-flavored potato chips also use it to produce a tart, vinegar-like flavor.