lactic acid

A normal intermediate in the fermentation (oxidation, metabolism) of sugar. In pure form, a syrupy, odorless, and colorless liquid obtained by the action of the l. bacillus on milk or milk sugar; in concentrated form, a caustic used internally to prevent gastrointestinal fermentation. A culture of the bacillus, or milk containing it, is usually given in place of the acid. l- L. is also known as sarcolactic acid.

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lactic acid n a hygroscopic organic acid C₃H₆O₃ that is known in three optically isomeric forms:

a) or L-lactic acid 'el- the dextrorotatory form present normally in blood and muscle tissue as a product of the anaerobic metabolism of glucose and glycogen

b) or D-lactic acid 'dē- the levorotatory form obtained by biological fermentation of sucrose

c) or DL-lactic acid 'dē-'el- the racemic form present in food products and made usu. by bacterial fermentation (as of whey or raw sugar) but also synthetically, and used chiefly in foods and beverages, in medicine, in tanning and dyeing, and in making esters for use as solvents and plasticizers

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a compound that forms in the cells as the end-product of glucose metabolism in the absence of oxygen (see glycolysis). During strenuous exercise pyruvic acid is reduced to lactic acid, which may accumulate in the muscles and cause cramp. Lactic acid (owing to its low pH) is an important food preservative. The lactic acid produced by the fermentation of milk is responsible for the preservation and flavour of cheese, yoghurt, and other fermented milk products.

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lac·tic ac·id (lakґtik) a metabolic intermediate involved in many biochemical processes; it is the end product of glycolysis, which provides energy anaerobically in skeletal muscle during heavy exercise, and it can be oxidized aerobically in the heart for energy production or can be converted back to glucose (gluconeogenesis). Lactate is also the end product of fermentation in several bacterial species. See also lacticacidemia. [USP] a preparation of lactic acid prepared by the lactic fermentation of sugars or prepared synthetically; used as a pharmaceutic necessity.