It is a naturalpreservative/conservative which occurs naturally in citrus fruits and is also used to add an acidic or sour taste to foods and drinks. In biochemistry, the conjugate base of citric acid, citrate, is important as an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. It consists of 3 carboxyl (R-COOH) groups.Citric acid is a commodity chemical, and more than a million tons are produced every year by fermentation. It is used mainly as an acidifier, as a flavoring, and as a chelating agent.