Lactic Acid
Lactic Acid, a colorless (or yellowish), odorless, organic chemical compound. Lactic acid is soluble in water, alcohol, and ether. Widely distributed in nature, it is commonly formed in animal tissues and by bacteria. For example, it is lactic acid produced by the bacterial breakdown of milk sugar that causes the acidity of soured milk and yogurt. Lactic acid also imparts the sour flavor to sauerkraut.
Lactic acid has a variety of commercial uses. It is added to foods and beverages as a flavoring agent and as a preservative. It is sometimes used by the textile industry in the acid dying of wool and other textiles and by the leather industry, both in the preparation of hides for tanning and in the tanning process itself. Lactic acid is also used in making some plastics, medicines, adhesives, and solvents. Most lactic acid for commercial use is produced synthetically. Some is produced by the bacterial fermentation of whey (the watery part of milk), molasses, potatoes, or other substances.
Small amounts of lactic acid are constantly being formed and neutralized by various cells of the human body, especially those in muscle tissue. During strenuous exercise, however, lactic acid accumulates faster than the body can neutralize it. It is this accumulation that is responsible for muscle fatigue.
Chemical formula: CH3CHOHCOOH. Melting point: 64.4 F. (18 C.); boiling point: 252 F. (122 C.).