Lactic << LAK tihk >> acid is the common organic acid found in milk and other dairy foods that have turned “sour.” It also occurs in sauerkraut , pickles, and beer. It exists in two forms, D-lactic acid and L-lactic acid. D-lactic acid is formed by the fermentation of sugar. L-lactic acid is found in human and animal blood. During bursts of muscular activity, L-lactic acid builds up in the muscle tissue. Scientists once thought that the lactic acid caused muscle soreness, contributing to fatigue. However, studies have suggested that the muscle cells actually break down the lactic acid to produce additional energy.
Lactic acid is formed naturally by the fermentation of lactose (milk sugar). Its name comes from the Latin word lac, which means milk. Carl Scheele, a Swedish chemist, first isolated the acid from sour milk in 1780.
Commercially, the acid is made by fermenting cornstarch, molasses, potatoes, or whey (the watery part of milk). It is used in foods and beverages to bring out flavor. The tanning industry uses crude lactic acid to remove lime from hides. The textile industry uses it in dyeing wool. It combines with alcohols to form lactate esters, used as lacquer solvents and in medicines and foods. Lactic acid is a colorless or yellowish syrupy liquid that mixes readily with water.
