lactic acid

lactic acid CH ₃ CHOHCO ₂ H, a colorless liquid organic acid. It is miscible with water or ethanol. Lactic acid is a fermentation product of lactose (milk sugar); it is present in sour milk, koumiss, leban, yogurt, and cottage cheese. The protein in milk is coagulated (curdled) by lactic acid. Lactic acid is produced in the muscles during intense activity by the breakdown of glucose, and may be used by muscle cells as a source of energy. Calcium lactate, a soluble lactic acid salt, is used as a source of calcium in the diet. Lactic acid is produced commercially for use in pharmaceuticals and foods, in leather tanning and textile dyeing, and in making plastics, solvents, inks, and lacquers. Although it can be prepared by chemical synthesis, production of lactic acid by fermentation of glucose and other substances is a less expensive method. Chemically, lactic acid occurs as two optical isomers , a dextro and a levo form; only the levo form takes part in animal metabolism. The lactic acid of commerce is usually an optically inactive racemic mixture of the two isomers.

lactic acid A three-carbon hydroxyacid, formed as the major metabolic product of certain bacteria, and also from pyruvic acid in animal cells when glycolysis occurs under anaerobic conditions.

lactic acid (lak-tik) n. a compound that forms in the cells as the end-product of glucose metabolism in the absence of oxygen (see glycolysis). Lactic acid (owing to its low pH) is an important food preservative.