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Monosodium glutamate

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This article is about the chemical compound. For its use in food flavouring and health concerns, see glutamic acid (flavor). For glutamic acid in general, see glutamic acid.
Monosodium glutamate
Crystalline monosodium glutamate
Names
IUPAC name
Sodium 2-Aminopentanedioate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.005.035 Edit this at Wikidata
E number E621 (flavour enhancer)
  • C(CC(=O)O)C(C(=O)[O-])N.[Na+]
Properties
C5H8NNaO4
Molar mass 169.111 g/mol
Appearance white crystalline powder
Melting point 232 °C (450 °F; 505 K)
74g/100mL
Hazards
Lethal dose or concentration (LD, LC):
16600 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Monosodium glutamate, also known as sodium glutamate and MSG, is a sodium salt of the naturally occurring non-essential amino acid glutamic 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[1]. Trade names of monosodium glutamate include Ajinomoto, Vetsin, Accent 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.[2][3][4][5]

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).

Production and chemical properties

MSG is obtained by the fermentation of carbohydrates and by using bacterial or yeast species from genera such as Brevibacterium, Arthrobacter, Microbacterium, and Corynebacterium. Yields of 100 g/litre[6] can be prepared in this way. From 1909 to the mid-1960s, MSG was prepared by the hydrolysis of wheat gluten, which is roughly 25% glutamic acid. Glutamic acid is one of the least-soluble amino acids, which facilitates its purification.[7]

Like the sodium salts of other amino acids, MSG is a stable colourless solid that is degraded by strong oxidizing agents. It exists as a pair of mirror image stereoisomers (enantiomers), but only the naturally occurring L-glutamate form is used as a flavour enhancer.

Commercialization

The Ajinomoto company was formed to manufacture and market MSG in Japan; the name 'Aji no moto' translates to "essence of taste". It was introduced to the United States in 1947 as Ac'cent flavor enhancer.[8]

Modern commercial MSG is produced by fermentation[9] of starch, sugar beets, sugar cane, or molasses. About 1.5 million tonnes were sold in 2001, with 4% annual growth expected.[10] MSG is used commercially as a flavour enhancer. Although once associated with foods in Chinese restaurants, MSG is now used by most fast-food chains and in many foodstuffs, in particular, processed foods.[11]

Examples include:

Only the L-glutamate enantiomer has flavour-enhancing properties.[12] Manufactured MSG contains over 99.6% of the naturally predominant L-glutamate form, which is a higher proportion of L-glutamate than found in the free glutamate ions of naturally occurring foods. Fermented products such as soy sauce, steak sauce, and Worcestershire sauce have levels of glutamate similar to foods with added MSG. However, glutamate in these brewed products may have 5% or more of the D-enantiomer.[12]

Health concerns

Main article: Health effects research into Glutamic acid

A report from the Federation of American Societies for Experimental Biology (FASEB) compiled in 1995 on behalf of the United States Food and Drug Administration (FDA) concluded that MSG is safe for most people when “eaten at customary levels”. However, it also said that, based on anecdotal reports, some people may have an MSG intolerance that causes “MSG symptom complex” and/or a worsening of asthmatic symptoms.[13] Subsequent research found that, while large doses of MSG given without food may elicit more symptoms than a placebo in individuals who believe that they react adversely to MSG, the frequency of the responses was low and the responses reported were inconsistent, not reproducible, and not observed when MSG was given with food.[14] No statistical association has been demonstrated under controlled conditions, even in studies with people convinced that they are sensitive to it.[14][15][16][17] Adequately controlling for experimental bias includes a placebo-controlled double-blind experimental design and the application in capsules because of the strong and unique after-taste of glutamates.[15]

Obesity experiments often rely on treating lab rats with monosodium glutamate, which is a fast and reliable way of inducing obesity in animal test subjects.[18] In 2008, The New York Times published an article elucidating a link between MSG and obesity in humans. The article, based on a study conducted by the University of North Carolina, noted that for every 0.04 ounce daily increase in MSG intake, B.M.I. went up by 0.61.[19] This hypothetical association is contended by a study observing Chinese adults, over a five year period, which has shown MSG to have no effect on obesity or weight gain.[20]

United States

Monosodium glutamate is one of several forms of glutamic acid found in foods, in large part because glutamic acid, being an amino acid, is pervasive in nature. Glutamic acid and its salts can also be present in a wide variety of other additives, including hydrolyzed vegetable proteins, autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts, and protein isolate, which must be labeled with these common and usual names. Since 1998, these cannot be included in the term "spices and flavorings". The food additives disodium inosinate and disodium guanylate, which are ribonucleotides, are usually used in synergy with monosodium glutamate-containing ingredients.

The FDA considers labels such as "No MSG" or "No Added MSG" to be misleading if the food contains ingredients that are sources of free glutamate, such as hydrolyzed protein. In 1993, the FDA proposed adding the phrase "(contains glutamate)" to the common or usual names of certain protein hydrolysates that contain substantial amounts of glutamate.

In the 2004 version of his book On Food and Cooking, food scientist Harold McGee states that "[after many studies], toxicologists have concluded that MSG is a harmless ingredient for most people, even in large amounts."[21]

Asia

The INTERMAP Cooperative Research Group conducted a study of 752 healthy Chinese (48.7% women), age 40–59 years, randomly sampled from three rural villages in north and south China and determined that MSG intake may be positively correlated to an increased body mass index (BMI).[22]

Australia and New Zealand

Standard 1.2.4 of the Australia and New Zealand Food Standards Code requires the presence of MSG as a food additive to be labeled. The label must bear the food additive class name (e.g., flavour enhancer), followed by either the name of the food additive, MSG, or its International Numbering System (INS) number, 621.[23]

See also

References

  1. ^ http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist
  2. ^ http://www.celiac.com/articles/181/1/Safe-Gluten-Free-Food-List-Safe-Ingredients/Page1.html
  3. ^ Leung, Albert Y. (2003). "Monosodium Glutamate". Encyclopedia of Common Natural Ingredients: Used in Food, Drugs, and Cosmetics (2nd ed.). New York: Wiley. pp. 373–375. ISBN 978-0-471-47128-8. Monosodium glutamate can generally be produced by three methods: (1) hydrolysis of proteins such as gluten or proteins present in sugar beet wastes, (2) synthesis, and (3) microbial fermentation. In the hydrolysis method, the protein is hydrolyzed with a strong mineral acid to free amino acids, and the glutamic acid is then separated from the mixture, purified, and converted to its monosodium salt, [monosodium glutamate]. This used to be the major method of [monosodium glutamate] manufacture. Currently most of the world production of [monosodium glutamate] is by bacterial fermentation. In this method, bacteria (especially strains of Micrococcus glutamicus) are grown aerobically in a liquid nutrient medium containing a carbon source (e.g., dextrose or citrate), a nitrogen source such as ammonium ions or urea, and mineral ions and growth factors. The bacteria selected for this process have the ability to excrete glutamic acid they synthesize outside of their cell membrane into the medium and accumulate there. The glutamic acid is separated from the fermentation broth by filtration, concentration, acidification, and crystallization, followed by conversion to its monosodium salt [monosodium glutamate]. {{cite encyclopedia}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  4. ^ http://www.celiac.ca/Articles/Fall1990-1.html
  5. ^ http://www.jstor.org/stable/3421360
  6. ^ http://www.ukfoodguide.net/e621.htm
  7. ^ Kawakita, Tetsuya (2005). "Monosodium Glutamate". Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16 711. {{cite encyclopedia}}: Check |doi= value (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ Sand, Jordan (2005). "A Short History of MSG". Gastronomica. 5 (4): pp. 38–49. doi:10.1525/gfc.2005.5.4.38. {{cite journal}}: |pages= has extra text (help)
  9. ^ "Production process". Encyclopedia of Amino Acids. Anjimoto Co., Inc.
  10. ^ http://www.ajinomoto.co.jp/ajinomoto/A-Company/company/zaimu/pdf/fact/food_biz.pdf
  11. ^ Moskin, Julia (2008-03-05). "Yes, MSG, the Secret Behind the Savor". New York Times.
  12. ^ a b Rundlett, Kimber L (1994). "Evaluation of free D-glutamate in processed foods". Chirality. 6 (4): pp. 277–282. doi:10.1002/chir.530060410. PMID 7915127. {{cite journal}}: |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  13. ^ FDA Backgrounder: FDA and Monosodium Glutamate
  14. ^ a b Geha RS, Beiser A, Ren C; et al. (2000). "Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study". J. Nutr. 130 (4S Suppl): 1058S–62S. PMID 10736382. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  15. ^ a b Tarasoff L., Kelly M.F. (1993). "Monosodium L-glutamate: a double-blind study and review". Food Chem. Toxicol. 31 (12): 1019–1035. doi:10.1016/0278-6915(93)90012-N. PMID 8282275.
  16. ^ Freeman M. (2006). "Reconsidering the effects of monosodium glutamate: a literature review". J Am Acad Nurse Pract. 18 (10): 482–6. doi:10.1111/j.1745-7599.2006.00160.x. PMID 16999713. {{cite journal}}: Unknown parameter |month= ignored (help)
  17. ^ Walker R (1999). "The significance of excursions above the ADI. Case study: monosodium glutamate". Regul. Toxicol. Pharmacol. 30 (2 Pt 2): S119–S121. doi:10.1006/rtph.1999.1337. PMID 10597625. {{cite journal}}: Unknown parameter |month= ignored (help)
  18. ^ http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WN4-4CCGGN1-9P&_user=10&_coverDate=11%2F30%2F1984&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5f2c4cd3d168c72a8af8f1078f124f35&searchtype=a
  19. ^ http://www.nytimes.com/2008/08/26/health/nutrition/26nutr.html
  20. ^ http://www.ncbi.nlm.nih.gov/pubmed/20370941
  21. ^ McGee, Harold, On Food and Cooking, the Science and Lore of the Kitchen, 2004
  22. ^ He, Ka (2008). "Association of monosodium glutamate intake with overweight in Chinese adults: the INTERMAP Study". Obesity. 16 (8). The Obesity Society: pp. 1875–1880. doi:10.1038/oby.2008.274. PMC 2610632. PMID 18497735. {{cite journal}}: |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  23. ^ "Standard 1.2.4 Labelling of Ingredients". Food Standards Code. Food Standards Australia New Zealand. Retrieved May 15, 2010.
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