Lactic acid (2-hydroxypropionic acid, CH3-CHOH-COOH) is the most widely occurring organic acid in nature. Due to its chiral a-carbon atom, lactic acid (LA) has two enantiomeric forms. Of these, L-(+)-lactic acid is more important in food and pharmaceutical industries because humans have only L-lactate dehydrogenase. The chemical behavior of lactic acid is mostly determined by the two functional groups. Besides the acidic character in aqueous medium, the bifunctionality (a terminal carboxylic acid and a hydroxyl group) allows lactic acid molecules to form ‘‘interesters’’ such as the cyclic dimers, the trimers, or longer lactic acid oligomers.
