2hydroxypropanoic

2-hydroxypropanoic acid, commonly known as lactic acid, is a naturally occurring hydroxycarboxylic acid with the formula C3H6O3. It is the simplest alpha-hydroxy acid, featuring a hydroxyl group on the second carbon of propanoic acid. The molecule contains a chiral center at C2, giving rise to two enantiomers: L-(+)-lactic acid and D-(-)-lactic acid; the naturally occurring form in foods and in human metabolism is predominantly the L enantiomer.

Occurrence and production: Lactic acid is produced by lactic acid bacteria during fermentation of carbohydrates, contributing to the tangy flavors of yogurt, kefir, sauerkraut, and other fermented foods. It can also be produced industrially by microbial fermentation or chemical synthesis, and is obtained as racemic DL-lactic acid or as an optically active enantiomer depending on the process.

Uses: Lactic acid is used as a food additive for acidity regulation and flavor enhancement, as well as a preservative and humectant. In cosmetics and personal care products it serves as a pH adjuster and mild exfoliant. In materials science, lactic acid is polymerized to polylactic acid (PLA), a biodegradable bioplastic widely used in packaging and 3D printing.

Metabolism and biology: In animals, lactate is produced from pyruvate during anaerobic glycolysis and can be transported to the liver for gluconeogenesis in the Cori cycle. Lactic acid accumulation can occur under intense exercise or certain metabolic conditions.

Safety and history: Lactic acid is generally recognized as safe for use in foods. It was first isolated by the Swedish chemist Carl Wilhelm Scheele in 1780 from sour milk, a fact reflected in its common name.

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