piimhape

Piimhape, known in English as lactic acid, is an alpha-hydroxycarboxylic acid with the chemical formula C3H6O3. Its systematic name is 2-hydroxypropanoic acid. Lactic acid exists as two enantiomers, L-lactic acid and D-lactic acid, as well as a racemic mixture. It occurs naturally in many fermented foods and is produced by lactic acid bacteria during carbohydrate fermentation, giving characteristic sour flavors in products such as yogurt, kefir, sauerkraut, and sourdough. Industrially, it is produced by fermentation or by hydrolysis of lactide derived from polylactic acid.

In humans, lactic acid is produced in muscle tissue during anaerobic glycolysis and can contribute to the feeling of muscle fatigue and a temporary drop in local pH. It also participates in various metabolic pathways and can be converted back to glucose in the liver through the Cori cycle.

Physical and chemical properties: lactic acid is a colorless liquid that is miscible with water. It is a weak acid with a pKa around 3.86 and forms lactate salts. It is hygroscopic and soluble in water, ethanol, and many other solvents. The two enantiomers can have different biological and sensory effects, which is relevant in some applications.

Applications: In the food industry, lactic acid acts as an acidity regulator, flavoring agent, and preservative (E270). In cosmetics, it is used as an alpha-hydroxy acid for exfoliation and as a humectant. It is also the monomer used to make polylactic acid (PLA), a biodegradable polymer used in packaging and medical devices.

Safety: lactic acid is generally recognized as safe for common uses; high concentrations can be corrosive and may irritate skin or eyes. Proper handling and storage are advised.