A natural acid found in sour apples and other fruits. In winemaking, when certain bacteria convert malic acid to lactic acid (which is much less strong and sour), a process called "malolactic fermentation" occurs. This reduces the wine's tartness, adds complexity to the flavor and sometimes contributes a slight sparkle. Malic acid is used as an acidulant as well as a flavoring agent in the processing of some foods.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.