Monosodium glutamate

Monosodium glutamate(MSG), also known assodium glutamate,  is asodiumsaltofglutamic acid.  MSG is found naturally in some foods includingtomatoesandcheesein this glutamic acid form.MSG is used in cooking as a flavor enhancer with a savory taste that intensifies theumamiflavor of food, as naturally occurring glutamate does in foods such asstewsand meat soups.
MSG was first prepared in 1908 by JapanesebiochemistKikunae Ikeda, who tried to isolate and duplicate the savory taste ofkombu, an edibleseaweedused as abroth(dashi) forJapanese cuisine. MSG balances, blends, and rounds the perception of other tastes.MSG, along withdisodium ribonucleotides, is commonly used and found instock (bouillon) cubes,soups,ramen,gravy,stews,condiments, savorysnacks, etc.
The U.S.Food and Drug Administrationhas given MSG itsgenerally recognized as safe(GRAS) designation.It is a popular misconception that MSG can causeheadachesand other feelings of discomfort, known as "Chinese restaurant syndrome". Severalblinded studiesshow no such effects when MSG is combined with food in normal concentrations, and are inconclusive when MSG is added to broth in large concentrations.TheEuropean Unionclassifies it as afood additivepermitted in certain foods and subject to quantitative limits. MSG has theHS code2922.42 and theE numberE621.
Pure MSG is reported not to have a highly pleasant taste until it is combined with a savoryaroma.The basic sensory function of MSG is attributed to its ability to enhance savory taste-active compounds when added in the proper concentration.The optimal concentration varies by food; inclear soup, the "pleasure score" rapidly falls with the addition of more than one gram of MSG per 100mL.
The sodium content (inmass percent) of MSG, 12.28%, is about one-third of that insodium chloride(39.34%), due to the greater mass of the glutamate counterion.Although other salts of glutamate have been used in low-salt soups, they are less palatable than MSG.Food scientistSteve Witherly noted in 2017 that MSG may promote healthy eating by enhancing the flavor of food such askalewhile reducing the use ofsalt.
Theribonucleotidefood additivesdisodium inosinate(E631) anddisodium guanylate(E627), as well as conventional salt, are usually used with monosodium glutamate-containing ingredients as they seem to have a synergistic effect. "Super salt" is a mixture of 9 parts salt, to one part MSG and 0.1 partsdisodium ribonucleotides(a mixture ofdisodium inosinateanddisodium guanylate).
MSG isgenerally recognized as safeto eat.A popular belief is that MSG can cause headaches and other feelings of discomfort, butblinded testshave not provided strong evidence of this.International bodies governing food additives currently consider MSG safe for human consumption as a flavor enhancer.Under normal conditions, humans can metabolize relatively large quantities of glutamate, which is naturally produced in the gut in the course of protein hydrolysis. Themedian lethal dose(LD50) is between 15 and 18 g/kg body weight in rats and mice, respectively, five times the LD50oftable salt(3 g/kg in rats). The use of MSG as a food additive and the natural levels of glutamic acid in foods are not of toxic concern in humans.Specifically MSG in the diet does not increase glutamate in the brain or affect brain function.
A 1995 report from theFederation of American Societies for Experimental Biology(FASEB) for theUnited States Food and Drug Administration(FDA) concluded that MSG is safe when "eaten at customary levels" and, although a subgroup of otherwise-healthy individuals develop an MSG symptom complex when exposed to 3 g of MSG in the absence of food, MSG as a cause has not been established because the symptom reports are anecdotal.
According to the report, no data supports the role of glutamate inchronic disease. High quality evidence has failed to demonstrate a relationship between the MSG symptom complex and actual MSG consumption. No association has been demonstrated, and the few responses were inconsistent. No symptoms were observed when MSG was used in food.
Adequately controlling for experimental bias includes a blinded,placebo-controlledexperimental designand administration by capsule, because of the unique aftertaste of glutamates.In a 1993 study, 71 fasting participants were given 5 g of MSG and then a standard breakfast. One reaction (to the placebo, in a self-identified MSG-sensitive individual) occurred.A study in 2000 tested the reaction of 130 subjects with a reported sensitivity to MSG. Multiple trials were performed, with subjects exhibiting at least two symptoms continuing. Two people out of the 130 responded to all four challenges. Because of the low prevalence, the researchers concluded that a response to MSG was not reproducible.
Studies exploring MSG's role inobesityhave yielded mixed results.
Although several studies have investigated anecdotal links between MSG andasthma, current evidence does not support a causal association.
Food Standards Australia New Zealand(FSANZ) MSG technical report concludes,
However, the FSANZ MSG report says that although no data is available on average MSG consumption in Australia and New Zealand, "data from the United Kingdom indicates an average intake of 590mg/day, with extreme users (97.5th percentile consumers) consuming 2,330mg/day" (Rhodes et al. 1991).In a highly seasoned restaurant meal, intakes as high as 5,000 mg or more may be possible (Yang et al. 1997).When very large doses of MSG (>5 g MSG in abolusdose) are ingested, plasma glutamate concentration will significantly increase. However, the concentration typically returns to normal within two hours. In general, foods providing metabolizablecarbohydratessignificantly attenuate peak plasma glutamate levels at doses up to 150mg/kg body weight. Two earlier studies – the 1987 JointFAO/WHOExpert Committee on Food Additives (JECFA) and the 1995Federation of American Societies for Experimental Biology(FASEB) – concluded, "there may be a small number of unstable asthmatics who respond to doses of 1.5–2.5 g of MSG in the absence of food". The FASEB evaluation concluded, "sufficient evidence exists to indicate some individuals may experience manifestations of CRS when exposed to a ≥3 g bolus dose of MSG in the absence of food".
MSG has been produced by three methods:hydrolysisof vegetable proteins with hydrochloric acid to disruptpeptide bonds(1909–1962); direct chemical synthesis withacrylonitrile(1962–1973), andbacterial fermentation(the current method).Wheat glutenwas originally used forhydrolysisbecause it contains more than 30 g of glutamate and glutamine per 100 g of protein. As demand for MSG increased, chemical synthesis and fermentation were studied.  Thepolyacrylicfiber industry began in Japan during the mid-1950s, andacrylonitrilewas adopted as a base material to synthesize MSG.
As of 2016, most MSG worldwide is produced bybacterial fermentationin a process similar to making vinegar or yogurt.Sodiumis added later, for neutralization. During fermentation,Corynebacteriumspecies, cultured withammoniaandcarbohydratesfromsugar beets,sugarcane,tapiocaormolasses, excrete amino acids into a culture broth from which L-glutamate is isolated. Kyowa Hakko Kogyo (currentlyKyowa Kirin) developed industrial fermentation to produce L-glutamate.
The conversion yield and production rate (from sugars to glutamate) continues to improve in the industrial production of MSG, keeping up with demand.The product, after filtration, concentration, acidification, and crystallization, is glutamate, sodium ions, and water.
The compound is usually available as themonohydrate, a white, odorless, crystalline powder. The solid contains separate sodium cationsNaand glutamate anions inzwitterionicform,OOC-CH(NH3)-(CH2)2-COO.In solution itdissociatesinto glutamate and sodium ions.
MSG is freely soluble in water, but it is nothygroscopicand is insoluble in common organic solvents (such asether).It is generally stable under food-processing conditions. MSG does not break down during cooking and, like other amino acids, will exhibit aMaillard reaction(browning) in the presence of sugars at very high temperatures.
Glutamic acidwas discovered and identified in 1866 by the German chemistKarl Heinrich Ritthausen, who treated wheatgluten(for which it was named) withsulfuric acid.Kikunae IkedaofTokyo Imperial Universityisolated glutamic acid as a taste substance in 1908 from the seaweedLaminaria japonica(kombu) by aqueous extraction and crystallization, calling its tasteumami("delicious taste").Ikeda noticed thatdashi, the Japanese broth ofkatsuobushiandkombu, had a unique taste not yet scientifically described (not sweet, salty, sour, or bitter).To determine which glutamate could result in the taste ofumami, he studied the taste properties of numerous glutamate salts such as calcium, potassium, ammonium, and magnesium glutamate. Of these salts, monosodium glutamate was the most soluble and palatable, as well as the easiest to crystallize.Ikeda called his product "monosodium glutamate" and submitted apatentto produce MSG;the Suzuki brothers began commercial production of MSG in 1909 using the termAjinomoto("essence of taste").
MSG is one of several forms of glutamic acid found in foods, in large part because glutamic acid (an amino acid) is pervasive in nature. Glutamic acid and its salts may be present in a variety of other additives, includinghydrolyzed vegetable protein,autolyzed yeast,hydrolyzed yeast,yeast extract,soyextracts, and protein isolate, which must be specifically labeled. Since 1998, MSG cannot be included in the term "spices and flavorings". However, the term "natural flavor/s" is used by the food industry for glutamic acid (chemically similar to MSG, lacking only the sodiumion). TheFood and Drug Administration(FDA) does not require disclosure of components and amounts of "natural flavor/s."
Standard 1.2.4 of the Australia and New Zealand Food Standards Code requires MSG to be labeled in packaged foods. The label must have the food-additive class name (e.g. "flavour enhancer"), followed by the name of the additive ("MSG") or itsInternational Numbering System(INS) number, 621.
ThePunjab Food Authoritybanned Ajinomoto, commonly known as Chinese salt, which contains MSG, from being used in food products in thePunjab Provinceof Pakistan in January 2018.
The prohibition against the import and manufacture of MSG was enforced on 28 February 2018, following an order by the Supreme Court on 10 February 2018.
In 2024, the federal government lifted the ban on MSG, following objections from Japan and a review of scientific evidence by an expert committee.The committee comprising experts from various institutions—including thePakistan Council of Scientific and Industrial Research,National Agricultural Research Centre, andPakistan Standards and Quality Control Authority—confirmed MSG as a safe food additive.
The following are alternative names for MSG:
The controversy surrounding the safety of MSG started with the publication of Robert Ho Man Kwok's correspondence letter titled "Chinese-Restaurant Syndrome" in theNew England Journal of Medicineon 4 April 1968.In his letter, Kwok suggested several possible causes before he nominated MSG for his symptoms.This letter was initially met with insider satirical responses, often usingrace as prop for humorous effect, within the medical community.During the discursive uptake in media, the conversations were recontextualized as legitimate while the race-based motivations of the humor were not parsed, which replicated historical racial prejudices.
Despite the resulting public backlash, theFood and Drug Administration(FDA) did not remove MSG from their Generally Recognized as Safe list.In 1970, a National Research Council under theNational Academy of Science, on behalf of the FDA, investigated MSG but concluded that MSG was safe for consumption.
The controversy about MSG is tied to racial stereotypes against East Asian societies.Herein, specificallyEast Asian cuisinewas targeted, whereas the widespread usage of MSG in Western processed food does not generate the same stigma.These kind of perceptions, such as the rhetoric of the so-called Chinese restaurant syndrome, have been attributed to xenophobic or racist biases.
Food historian Ian Mosby wrote that fear of MSG in Chinese food is part of the US's long history of viewing the "exotic" cuisine of Asia as dangerous and dirty.In 2016,Anthony Bourdainstated inParts Unknownthat "I think MSG is good stuff ... You know what causes Chinese restaurant syndrome? Racism."
In 2020,Ajinomoto, the leading manufacturer of MSG, and others launched the #RedefineCRS campaign, in reference to the term "Chinese restaurant syndrome", to combat the misconceptions about MSG, saying they intended to highlight the xenophobicprejudiceagainstEast Asian cuisineand the scientific evidence.Following the campaign, Merriam-Webster announced it would review the term.