A process by which food or drink goes through a chemical change caused by enzymes produced from bacteria, microorganisms or yeasts. Fermentation alters the appearance and/or flavor of foods and beverages such as beer, buttermilk, cheese, vinegar, yogurt, and wine. In wine, for example, yeast enzymes convert grape-juice sugars into alcohol, while in rum, the enzymes convert sugar cane molasses into alcohol. With whiskeys, a mash is made from cereal grains such as corn, rye or barleydiastase enzymes convert the grain's starches into sugar, which is subsequently converted by yeast to alcohol. And in cheesemaking, the fermentation of milk converts carbohydrates into acids, producing lactic acid from the lactose (milk sugar).
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.