Monosodium glutamate (MSG) is the sodium salt of the amino acid glutamic acid, widely used as a flavor enhancer to impart umami taste in foods. It occurs naturally in foods like tomatoes and cheese but is produced industrially via fermentation of starch or sugar. Chemically stable under normal conditions, it functions by stimulating glutamate receptors on the tongue. MSG is highly water-soluble, forming clear solutions, and is approved as a food additive (E621) with GRAS status by the FDA. It does not alter the flavor of food but amplifies existing savory notes. Physical properties include a white crystalline appearance and decomposition at high temperatures without boiling.