Piimhappeded

Piimhappeded, or lactic acids, are a group of simple organic acids led by lactic acid (2-hydroxypropanoic acid). They are alpha-hydroxy acids (AHA) with the chemical formula C3H6O3 and occur as two enantiomers: L-lactic acid and D-lactic acid. In many contexts the L-enantiomer is the predominant form. The acids are weak, water-soluble, and form lactate salts at neutral or basic pH.

Occurrence and production

Lactic acids are produced by lactic acid bacteria during fermentation, contributing to the sour taste of dairy products like yogurt and kefir, as well as fermented vegetables and sourdough. In human metabolism, lactate is formed from pyruvate during anaerobic glycolysis and can be used as an energy source by various tissues. Lactic acid and lactate also appear naturally in exercising muscle and in some tissues under low-oxygen conditions.

Industrial production and applications

Commercially, lactic acid is produced by fermentation using lactic acid bacteria or by chemical synthesis from pyruvic acid. It serves as an acidifier, flavoring, and preservative in foods, a humectant and pH adjuster in cosmetics, and a monomer for the production of biodegradable polylactic acid (PLA) used in plastics. In food labeling, lactic acid is often listed as an additive (for example, E270 in the European Union).

Safety and metabolism

Lactic acid is generally recognized as safe for use in foods. Excessive accumulation of D-lactic acid, particularly in certain medical conditions, can lead to metabolic complications. In most healthy individuals, the body metabolizes lactate efficiently, balancing production and clearance through the liver, heart, and kidneys.