Lactic Acid

Lactic Acid, colorless compound of formula CH₃CHOHCOOH. It exists in two optically active forms, dextro- and levo-, often designated as D-lactic acid and L-lactic acid. Ordinary lactic acid, or racemic lactic acid, is an optically inactive mixture made up of equal parts of the D- and L-forms.

The acid is usually prepared by fermentation of starch, cane sugar, or whey. Small amounts of L-lactic acid occur in blood, in muscles, and in other body fluids and organs. They are produced by body tissues, primarily muscle, that obtain energy by metabolizing sugar in the absence of oxygen (see Fermentation). The building up of large amounts of lactic acid in muscle leads to fatigue and can cause cramps. Lactic acid, generated in milk by fermentation of lactose, causes the souring of milk. Lactic acid is used in preparing cheese, sauerkraut, soft drinks, and other food products.