Article: Monosodium glutamate

This article appears to contradict another article: Glutamic acid. Please see discussion on the talk page.

This article is about sodium glutamate as a food additive. For an overview of the chemistry of glutamic acid, see glutamic acid.

Chemical structure of monosodium glutamate

Monosodium glutamate, sodium glutamate, flavour enhancer 621 EU food additive code: E621. HS code: 29224220. (IUPAC names: 2-aminopentanedioic acid, 2-aminoglutaric acid, 1-aminopropane-1,3-dicarboxylic acid), commonly known as MSG or Vetsin, is a sodium salt of glutamic acid. MSG is a food additive, popularly marketed as a "flavour enhancer". In its pure form, it appears as a white crystalline powder; when dissolved in water (or saliva) it rapidly dissociates into free sodium and glutamate ions (glutamate is the anionic form of glutamic acid).

Natural occurrence of MSG

Glutamate itself is a widespread amino acid: it is found naturally in our bodies and in protein-containing foods, such as cheese, milk, meat, peas, and mushrooms. Some of the glutamate in foods is in a "free" form; and only this free form of glutamate can enhance the flavor of foods. Part of the flavour-enhancing effect of tomatoes, certain cheeses, and fermented or hydrolyzed protein products (such as soy sauce) is therefore due to the presence of free glutamate.

Asian cuisine originally used a natural seaweed broth, such as kelp, to bring up the umami taste in soups. Manufacturers, such as Ajinomoto, use selected strains of Micrococcus glutamicus bacteria in a bath of nutrient. The bacteria are selected for their ability to excrete glutamic acid, which is then separated from the nutrient bath, purified, and made into its sodium salt, monosodium glutamate.

Hydrolyzed proteins, or protein hydrolysates, are acid- or enzymatically treated proteins from certain foods. They contain salts of free amino acids, such as glutamate, at levels of 5 to 20 percent. Hydrolyzed proteins are used in the same manner as MSG in many foods, such as canned vegetables, soups, and processed meats.

Umami

MSG stimulates specific receptors located in taste buds such as the amino acid receptor T1R1/T1R3 or other glutamate receptors like the metabotropic receptors (mGluR4 and mGluR1) which induce the taste known as umami, one of the five basic tastes (the word umami is a loanword from Japanese; it is also referred to as "savoury" or "more-ish").

Scientific review

In 1959, FDA classified MSG as a "generally recognized as safe", or GRAS, substance. This action stemmed from the 1958 Food Additives Amendment to the Federal Food, Drug, and Cosmetic Act, which required premarket approval for new food additives and led FDA to promulgate regulations listing substances, such as MSG, which have a history of safe use or are otherwise GRAS. Since 1970, FDA has sponsored extensive reviews on the safety of MSG, other glutamates and hydrolyzed proteins, as part of an ongoing review of safety data on GRAS substances used in processed foods. One such review was by the Federation of American Societies for Experimental Biology (FASEB) Select Committee on GRAS Substances. In 1980, the committee concluded that MSG was safe at current levels of use but recommended additional evaluation to determine MSG's safety at significantly higher levels of consumption. Additional reports attempted to look at this. In 1986, FDA's Advisory Committee on Hypersensitivity to Food Constituents concluded that MSG poses no threat to the general public but that reactions of brief duration might occur in some people. Other reports gave similar findings:

• A 1991 report by the European Communities' (EC) Scientific Committee for Foods reaffirmed MSG's safety and classified its "acceptable daily intake" as "not specified", the most favorable designation for a food ingredient. In addition, the EC Committee said, "Infants, including prematures, have been shown to metabolize glutamate as efficiently as adults and therefore do not display any special susceptibility to elevated oral intakes of glutamate."
• A 1992 report from the Council on Scientific Affairs of the American Medical Association stated that glutamate in any form has not been shown to be a "significant health hazard".
• Also, the 1987 Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and the World Health Organization have placed MSG in the safest category of food ingredients.

Scientific knowledge about how the body metabolizes glutamate developed rapidly during the 1980s. Studies showed that glutamate in the body plays an important role in normal functioning of the nervous system. Questions then arose on the role glutamate in food plays in these functions and whether or not glutamate in food contributes to certain neurological diseases.