Any of a number of acids (chiefly organic) either occurring naturally in fruits and vegetables or used as additives in food processing. They function in the following ways: (1) as bacteriostats in processed foods; (2) as aids to the sterilization of canned foods by lowering the pH; (3) as chelating agents for metal ions such as iron and copper, which catalyze rancidity reactions in fats; (4) as flavor enhancers by offsetting excessive sweetness by their tart taste. Commonly used acidulants are citric, acetic, fumaric, ascorbic, propionic, lactic, adipic, malic, sorbic, and tartaric acids.