Names | |
---|---|
IUPAC name Sodium 2-aminopentanedioate | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
ECHA InfoCard | 100.005.035 |
EC Number |
|
E number | E621 (flavour enhancer) |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
| |
| |
Properties | |
C5H8NO4Na | |
Molar mass | 169.111 g/mol (anhydrous), 187.127 g/mol (monohydrate) |
Appearance | White crystalline powder |
Density | 322 |
Melting point | 232 °C (450 °F; 505 K) |
740 g/L | |
Hazards | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 16600 mg/kg (oral, rat) [1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Monosodium glutamate (MSG), also known as sodium glutamate, is a sodium salt of glutamic acid. MSG is found naturally in some foods including tomatoes and cheese in this glutamic acid form. [2] [3] [4] MSG is used in cooking as a flavor enhancer with a savory taste that intensifies the meaty, savory flavor of food, as naturally occurring glutamate does in foods such as stews and meat soups. [5] [6]
MSG was first prepared in 1908 by Japanese biochemist Kikunae Ikeda, who tried to isolate and duplicate the savory taste of kombu , an edible seaweed used as a broth ( dashi ) for Japanese cuisine. MSG balances, blends, and rounds the perception of other tastes. [7] [8] MSG, along with disodium ribonucleotides, is commonly used and found in stock (bouillon) cubes, soups, ramen, gravy, stews, condiments, savory snacks, etc.
The U.S. Food and Drug Administration has given MSG its generally recognized as safe (GRAS) designation. [9] It is a popular misconception that MSG can cause headaches and other feelings of discomfort, known as "Chinese restaurant syndrome". Several blinded studies show no such effects when MSG is combined with food in normal concentrations, and are inconclusive when MSG is added to broth in large concentrations. [9] [10] [11] The European Union classifies it as a food additive permitted in certain foods and subject to quantitative limits. MSG has the HS code 29224220 and the E number E621. [12]
Pure MSG is reported not to have a highly pleasant taste until it is combined with a savory aroma. [13] The basic sensory function of MSG is attributed to its ability to enhance savory taste-active compounds when added in the proper concentration. [7] The optimal concentration varies by food; in clear soup, the "pleasure score" rapidly falls with the addition of more than one gram of MSG per 100 mL. [14]
The sodium content (in mass percent) of MSG, 12.28%, is about one-third of that in sodium chloride (39.34%), due to the greater mass of the glutamate counterion. [15] Although other salts of glutamate have been used in low-salt soups, they are less palatable than MSG. [16] Food scientist Steve Witherly noted in 2017 that MSG may promote healthy eating by enhancing the flavor of food such as kale while reducing the use of salt. [17]
The ribonucleotide food additives disodium inosinate (E631) and disodium 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 parts disodium ribonucleotides (a mixture of disodium inosinate and disodium guanylate). [18]
MSG is generally recognized as safe to eat. [2] [19] A popular belief is that MSG can cause headaches and other feelings of discomfort, but blinded tests have not provided strong evidence of this. [10] International bodies governing food additives currently consider MSG safe for human consumption as a flavor enhancer. [20] Under normal conditions, humans can metabolize relatively large quantities of glutamate, which is naturally produced in the gut in the course of protein hydrolysis. The median lethal dose (LD50) is between 15 and 18 g/kg body weight in rats and mice, respectively, five times the LD50 of table 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. [20] Specifically MSG in the diet does not increase glutamate in the brain or affect brain function. [21]
A 1995 report from the Federation of American Societies for Experimental Biology (FASEB) for the United 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. [22]
According to the report, no data supports the role of glutamate in chronic 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. [23] [24] [25] [26]
Adequately controlling for experimental bias includes a blinded, placebo-controlled experimental design and administration by capsule, because of the unique aftertaste of glutamates. [25] 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. [23] 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. [27]
Studies exploring MSG's role in obesity have yielded mixed results. [28] [29]
Although several studies have investigated anecdotal links between MSG and asthma, current evidence does not support a causal association. [30]
Food Standards Australia New Zealand (FSANZ) MSG technical report concludes,
"There is no convincing evidence that MSG is a significant factor in causing systemic reactions resulting in severe illness or mortality. The studies conducted to date on Chinese restaurant syndrome (CRS) have largely failed to demonstrate a causal association with MSG. Symptoms resembling those of CRS may be provoked in a clinical setting in small numbers of individuals by the administration of large doses of MSG without food. However, such effects are neither persistent nor serious and are likely to be attenuated when MSG is consumed with food. In terms of more serious adverse effects such as the triggering of bronchospasm in asthmatic individuals, the evidence does not indicate that MSG is a significant trigger factor." [31] [32]
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). [33] In a highly seasoned restaurant meal, intakes as high as 5,000 mg or more may be possible (Yang et al. 1997). [34] When very large doses of MSG (>5 g MSG in a bolus dose) are ingested, plasma glutamate concentration will significantly increase. However, the concentration typically returns to normal within two hours. In general, foods providing metabolizable carbohydrates significantly attenuate peak plasma glutamate levels at doses up to 150mg/kg body weight. Two earlier studies –the 1987 Joint FAO/WHO Expert Committee on Food Additives (JECFA) and the 1995 Federation 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". [31]
MSG has been produced by three methods: hydrolysis of vegetable proteins with hydrochloric acid to disrupt peptide bonds (1909–1962); direct chemical synthesis with acrylonitrile (1962–1973), and bacterial fermentation (the current method). [35] Wheat gluten was originally used for hydrolysis because 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. The polyacrylic fiber industry began in Japan during the mid-1950s, and acrylonitrile was adopted as a base material to synthesize MSG. [36]
As of 2016, most MSG worldwide is produced by bacterial fermentation in a process similar to making vinegar or yogurt. Sodium is added later, for neutralization. During fermentation, Corynebacterium species, cultured with ammonia and carbohydrates from sugar beets, sugarcane, tapioca or molasses, excrete amino acids into a culture broth from which L-glutamate is isolated. Kyowa Hakko Kogyo (currently Kyowa Kirin) developed industrial fermentation to produce L-glutamate. [37]
The conversion yield and production rate (from sugars to glutamate) continues to improve in the industrial production of MSG, keeping up with demand. [35] The product, after filtration, concentration, acidification, and crystallization, is glutamate, sodium ions, and water.
The compound is usually available as the monohydrate, a white, odorless, crystalline powder. The solid contains separate sodium cations Na+
and glutamate anions in zwitterionic form, −OOC-CH(NH+
3)-(CH
2)2-COO−. [38] In solution it dissociates into glutamate and sodium ions.
MSG is freely soluble in water, but it is not hygroscopic and is insoluble in common organic solvents (such as ether). [39] It is generally stable under food-processing conditions. MSG does not break down during cooking and, like other amino acids, will exhibit a Maillard reaction (browning) in the presence of sugars at very high temperatures. [40]
Glutamic acid was discovered and identified in 1866 by the German chemist Karl Heinrich Ritthausen, who treated wheat gluten (for which it was named) with sulfuric acid. [41] Kikunae Ikeda of Tokyo Imperial University isolated glutamic acid as a taste substance in 1908 from the seaweed Laminaria japonica ( kombu ) by aqueous extraction and crystallization, calling its taste umami ("delicious taste"). [42] [43] Ikeda noticed that dashi , the Japanese broth of katsuobushi and kombu, had a unique taste not yet scientifically described (not sweet, salty, sour, or bitter). [42] To determine which glutamate could result in the taste of umami, 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. [44] Ikeda called his product "monosodium glutamate" and submitted a patent to produce MSG; [45] the Suzuki brothers began commercial production of MSG in 1909 using the term Ajinomoto ("essence of taste"). [35] [40] [46]
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, including hydrolyzed vegetable protein, autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts, 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 sodium ion). The Food and Drug Administration (FDA) does not require disclosure of components and amounts of "natural flavor/s." [47]
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 its International Numbering System (INS) number, 621. [48]
The Punjab Food Authority banned Ajinomoto, commonly known as Chinese salt, which contains MSG, from being used in food products in the Punjab Province of Pakistan in January 2018. [49]
The following are alternative names for MSG: [50] [51]
A controversy surrounding the safety of MSG began on 4 April 1968, when Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine , coining the term "Chinese restaurant syndrome". [57] [58] In his letter, Kwok suggested several possible causes before he nominated MSG for his symptoms. [59] [23] This letter was initially met with insider satirical responses, some using race as prop for humorous effect, within the medical community. [57] Some claimed that during the discursive uptake in media, the conversations were recontextualized as legitimate while the supposed race-based motivations of the humor were not parsed. [57]
In January 2018, Howard Steel claimed to Jennifer Lemesurier of Colgate University (who had published an article on the letter) that the letter was actually a prank submission by him under the pseudonym Ho Man Kwok. [58] [60] However, there was a Robert Ho Man Kwok who worked at the National Biomedical Research Foundation, both names Steel claimed to have invented. [60] Kwok's children, his colleague at the research foundation, and the son of his boss there confirmed that Robert Ho Man Kwok, who had died in 2014, wrote this letter. [60] When told this about Kwok's family, Steel's daughter Anna was not very surprised that the story her late father had told so many times over the years was false. He liked to prank people. [60]
Researchers, doctors, and activists have tied the controversy about MSG to xenophobia and racism against Chinese culture, [61] [62] [63] [64] [65] saying that East Asian cuisine is being targeted while the widespread use of MSG in other ultra-processed foods has not been stigmatized. [66] These activists have claimed that the perpetuation of the negative image of MSG through the Chinese restaurant syndrome was caused by "xenophobic" or "racist" biases. [67] [68]
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. [69] In 2016, Anthony Bourdain stated in Parts Unknown that "I think MSG is good stuff ... You know what causes Chinese restaurant syndrome? Racism." [70]
In 2020, Ajinomoto, the first corporation to mass-produce MSG for consumers and today its leading manufacturer, launched a campaign called "Redefine CRS" to combat what it said was the myth that MSG is harmful to people's health, saying it intended to highlight the xenophobic prejudice against East Asian cuisine and the scientific evidence. [71]
Miso is a traditional Japanese seasoning. It is a thick paste produced by fermenting soybeans with salt and kōji and sometimes rice, barley, seaweed, or other ingredients. It is used for sauces and spreads, pickling vegetables, fish, or meats, and mixing with dashi soup stock to serve as miso soup, a Japanese culinary staple. Miso is high in protein and rich in vitamins and minerals, and it played an important nutritional role in feudal Japan. Miso is still widely used in both traditional and modern cooking in Japan and has been gaining worldwide interest.
Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture media. They are often used to create savoury flavors and umami taste sensations and can be found in a large variety of packaged foods including frozen meals, crackers, snack foods, gravy, stock and more. They are rich in B vitamins. Yeast extracts and fermented foods contain glutamic acid, an amino acid which adds an umami flavor. Glutamic acid is found in meat, cheese, fungi and vegetables—such as broccoli and tomatoes. A number of other substances found in yeast extract provide aromas, some meat-like, when allowed to react under heat.
Umami, or savoriness, is one of the five basic tastes. It is characteristic of broths and cooked meats.
Glutamic acid is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synthesize enough for its use. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system. It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABAergic neurons.
Disodium inosinate (E631) is the disodium salt of inosinic acid with the chemical formula C10H11N4Na2O8P. It is used as a food additive and often found in instant noodles, potato chips, and a variety of other snacks.
Kikunae Ikeda was a Japanese chemist and Tokyo Imperial University professor of chemistry who, in 1908, uncovered the chemical basis of a taste he named umami. It is one of the five basic tastes along with sweet, bitter, sour and salty.
Disodium guanylate, also known as sodium 5'-guanylate and disodium 5'-guanylate, is a natural sodium salt of the flavor enhancing nucleotide guanosine monophosphate (GMP). Disodium guanylate is a food additive with the E number E627. It is commonly used in conjunction with glutamic acid.
Ajinomoto Co., Inc. is a Japanese multinational food and biotechnology corporation which produces seasonings, interlayer insulating materials for semiconductor packages for use in personal computers, cooking oils, frozen foods, beverages, sweeteners, amino acids, and pharmaceuticals. Aji-No-Moto is the trade name for the company's original monosodium glutamate (MSG) product, the first of its kind, since 1909. The corporation's head office is located in Chūō, Tokyo. As of 2023, Ajinomoto operates in 34 countries worldwide and employs an estimated 34,615 people. Its yearly revenue in 2023 is around ¥1.44 trillion JPY or $9.1 billion USD.
Guanosine monophosphate (GMP), also known as 5′-guanidylic acid or guanylic acid, is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. GMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase guanine; hence it is a ribonucleotide monophosphate. Guanosine monophosphate is commercially produced by microbial fermentation.
Inosinic acid or inosine monophosphate (IMP) is a nucleotide. Widely used as a flavor enhancer, it is typically obtained from chicken byproducts or other meat industry waste. Inosinic acid is important in metabolism. It is the ribonucleotide of hypoxanthine and the first nucleotide formed during the synthesis of purine nucleotides. It can also be formed by the deamination of adenosine monophosphate by AMP deaminase. It can be hydrolysed to inosine.
Disodium glutamate, abbreviated DSG, (Na2C5H7NO4) is a sodium salt of glutamic acid. It is used as a flavoring agent to impart umami flavor.
Calcium diglutamate, sometimes abbreviated CDG and also called calcium biglutamate, is a compound with formula Ca(C5H8NO4)2. It is a calcium acid salt of glutamic acid. CDG is a flavor enhancer (E number E623)—it is the calcium analog of monosodium glutamate (MSG). Because the glutamate is the actual flavor-enhancer, CDG has the same flavor-enhancing properties as MSG but without the increased sodium content. Notably, only the L isomer is used in flavouring as D-glutamate does not have an umami/savoury flavour.
A salt substitute, also known as low-sodium salt, is a low-sodium alternative to edible salt marketed to reduce the risk of high blood pressure and cardiovascular disease associated with a high intake of sodium chloride while maintaining a similar taste.
Disodium 5'-ribonucleotides or I+G, E number E635, is a flavor enhancer which is synergistic with glutamates in creating the taste of umami. It is a mixture of disodium inosinate (IMP) and disodium guanylate (GMP) and is often used where a food already contains natural glutamates or added monosodium glutamate (MSG). It is primarily used in flavored noodles, snack foods, chips, crackers, sauces and fast foods. It is produced by combining the sodium salts of the natural compounds guanylic acid (E626) and inosinic acid (E630).
Taste receptor type 1 member 1 is a protein that in humans is encoded by the TAS1R1 gene.
Glutamate flavoring is the generic name for flavor-enhancing compounds based on glutamic acid and its salts (glutamates). These compounds provide an umami (savory) taste to food.
The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception stimulated when a substance in the mouth reacts chemically with taste receptor cells located on taste buds in the oral cavity, mostly on the tongue. Taste, along with the sense of smell and trigeminal nerve stimulation, determines flavors of food and other substances. Humans have taste receptors on taste buds and other areas, including the upper surface of the tongue and the epiglottis. The gustatory cortex is responsible for the perception of taste.
Tien Chu Ve-Tsin Chemical Limited is a Chinese manufacturer of honey by-products, food chemicals and additives including monosodium glutamate (MSG).
Corn sauce or fermented corn sauce is produced by fermentation using corn starch as the primary substrate. It is used as a food condiment and ingredient, both in paste and in powder form. Corn sauce, like soy sauce, has a characteristic savory taste. It is used to flavor dishes including soups, broths, and gravies.
Kewpie—often misspelled kyūpī (キューピー) according to the pronunciation—is a Japanese brand of mayonnaise, and the name of the company that makes it. Kewpie is the best selling mayonnaise in Japan, and is also sold in other countries.
MSG occurs naturally in many foods, such as tomatoes and cheeses
Consumption of monosodium glutamate, or MSG, the widely used food additive, may increase the likelihood of being overweight, a new study says.
{{cite book}}
: |website=
ignored (help)Introduction: 'Chinese Restaurant Syndrome' as Rhetorical [...] Finally, I trace how the journalistic uptakes of this discussion, in only taking up certain medical phrases and terms, reproduce the tacit racism of this boundary policing while avowing the neutrality of medical authority.