Monosodium glutamate, also known as sodium glutamate and MSG, is a sodium salt of glutamic acid, a naturally occurring non-essential amino acid. It is used as a food additive and is commonly marketed as a flavour enhancer. It has the HS code 29224220 and the E number E621. Trade names of monosodium glutamate include Ajinomoto, Vetsin, Ac’cent, “Sazón Goya” and Tasting Powder. It was once made predominantly from wheat gluten, but is now made mostly from bacterial fermentation; it is acceptable for coeliacs following a gluten-free diet.
Although traditional East Asian cuisine had often used seaweed extract, which contains high concentrations of glutamic acid, it was not until 1907 that MSG was isolated by Kikunae Ikeda. MSG was subsequently patented by Ajinomoto Corporation of Japan in 1909. In its pure form, it appears as a white crystalline powder that, as a salt, dissociates into sodium cations and glutamate anions while dissolving (glutamate is the anionic form of glutamic acid).
There are health concerns about the use of monosodium glutamate in food, but few are scientifically supported.