Lactic acid

Lactic acid (2-hydroxypropanoic acid, CH₃CH(OH)COOH) is an organic acid found naturally in sour milk, molasses, fruits, beer and wine. Produced by lactic fermentation of sugars by lactic-acid bacteria — or industrially by fermentation of starch-derived glucose — it gives fermented foods (yoghurt, sauerkraut, sourdough, salami) their characteristic tang, lowers pH to inhibit pathogens and spoilage organisms, and is used directly as an acidulant (E270) and preservative in beverages, confectionery, meats and pickles. Both L(+)- and D(-)- enantiomers occur in foods; the L-form dominates human metabolism, while excess D-lactate can signal bacterial spoilage.