Monosodium glutamate, also known as
sodium glutamate or
MSG, is the sodium salt of
glutamic acidGlutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
, one of the most abundant naturally occurring
non-essentialAn essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism , and therefore must be supplied in the diet.-Essentiality vs. conditional essentiality in humans:...
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s.
It has been classified by the U.S.
Food and Drug AdministrationThe Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
as
generally recognized as safeGenerally recognized as safe is an American Food and Drug Administration designation that a chemical or substance added to food is considered safe by experts, and so is exempted from the usual Federal Food, Drug, and Cosmetic Act food additive tolerance requirements.-History:On January 1, 1958,...
(GRAS) and by the European Union as a
food additiveFood additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...
. MSG has the HS code 29224220 and the
E numberE numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...
E621.
The glutamate of MSG confers the same
umamiUmami , popularly referred to as savoriness, is one of the five basic tastes together with sweet, sour, bitter, and salty.-Etymology:Umami is a loanword from the Japanese meaning "pleasant savory taste". This particular writing was chosen by Professor Kikunae Ikeda from umai "delicious" and mi ...
taste of glutamate from other foods, being chemically identical.
Industrial food manufacturers market and use MSG as a flavor enhancer because it balances, blends and rounds the total perception of other tastes.
Trade names of monosodium glutamate include AJI-NO-MOTO®,
Vetsin, and
Ac'cent.
Invention
A Japanese chemist,
Kikunae Ikedawas a Japanese chemist and Tokyo Imperial University professor in Chemistry who, in 1908, uncovered the chemical root behind a taste he named umami. He discovered the common component that produced the flavor of meat, seaweed and tomatoes was glutamate, which produces the sensation of umami.He also...
, noticed that the Japanese broth of
katsuobushiis the Japanese name for dried, fermented, and smoked skipjack tuna .Shaved Katsuobushi and dried kelp - kombu - are the main ingredients of dashi, a broth that forms the basis of many soups and sauces in Japanese cuisine.Katsuobushi's distinct umami flavor comes from its high...
and
kombuKombu or konbu , also called dashima or haidai , is edible kelp from the family Laminariaceae widely eaten in East Asia....
had a peculiar taste that could not be classified as sweet, salty, sour or bitter. In 1908, Ikeda extracted glutamic acid from the seaweed
Laminaria japonicaSaccharina japonica is a marine species of Phaeophyceae , a type of kelp or seaweed, that is extensively cultivated in China, Japan and Korea....
, kombu, and purified it by
recrystallizationRecrystallization may refer to:*Recrystallization *Recrystallization *Recrystallization...
. He named this new taste "umami". To verify that
ionAn ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
ized glutamate was responsible for the umami taste, Ikeda studied the tastes of many glutamate salts such as calcium, potassium, ammonium, and magnesium glutamate. All salts elicited umami (in addition to a certain metallic taste due to the other minerals). Among those salts, sodium glutamate was the most soluble and palatable, and crystallized easily.
Ikeda submitted a patent to produce this compound, and the Suzuki brothers started the commercial production of MSG in 1909 as AJI-NO-MOTO®, meaning the essence of taste in Japanese, the first time that monosodium glutamate was produced in the world.
Production and chemical properties
Since the first time that MSG was released into the market, it has been produced by three methods: (1) hydrolysis of vegetable proteins with hydrochloric acid to disrupt peptide bonds (1909–1962), (2) direct chemical synthesis from acrylonitrile (1962–1973), and (3) bacterial fermentation; the current method.
Initially, wheat gluten was used for hydrolysis because it contains more than 30 g of glutamate and glutamine in 100 g of protein. In order to meet the ever-increasing demand for MSG, new production processes were studied:
chemical synthesisIn chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...
and
fermentationFermentation may refer to:* Fermentation , the use of fermentation in food preparation* Fermentation , a metabolic process whereby electrons released from nutrients are ultimately transferred to molecules obtained from the breakdown of those same nutrients* Fermentation , the process of...
. The
polyacrylicPoly or PAA or Carbomer is a type of anionic polymer. The monomer of poly is acrylic acid. In a water solution at neutral pH, many of the side chains of PAA will lose their protons and acquire a negative charge. This makes PAA a polyelectrolyte.Dry PAA is a white solid...
fiber industry began in Japan in the mid 1950s and
acrylonitrileAcrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...
was adopted then as starting material to synthesize MSG.
Currently, most of the world production of MSG is by bacterial fermentation in a process similar to wine, vinegar, yogurt and even chocolate. During fermentation, selected bacteria (coryneform bacteria) cultured with ammonia and carbohydrates from sugar beets, sugar cane, tapioca or molasses, excrete amino acids into the culture broth from where L-glutamate is isolated. Kyowa Hakko Kogyo Co Ltd developed the first industrial fermentation to produce L-glutamate. The yield and production rate from sugars to glutamate continues to improve in the industrial process, which allows manufacturers to keep up with demand. The final product after filtration, concentration, acidification and crystallization is pure glutamate, sodium and water. It appears as a white and odorless crystalline powder that in solution dissociates into glutamate and sodium. It is freely soluble in water, but not hygroscopic and practically insoluble in common organic solvents such as ether.
In general, MSG is stable under the conditions of regular food processing. During cooking, MSG does not decompose, but like other amino acids, browning or
Maillard reactionThe Maillard reaction is a form of nonenzymatic browning similar to caramelization. It results from a chemical reaction between an amino acid and a reducing sugar, usually requiring heat....
s will occur in the presence of sugars at very high temperatures.
Usage
Pure MSG does not have a pleasant taste by itself if it is not combined with a consonant savory smell.
As a flavor and in the right amount, MSG has the ability to enhance other taste-active compounds balancing and rounding the overall taste of certain dishes. MSG mixes well with meat, fish, poultry, many vegetables, sauces, soups and marinades, and increases the overall preference of certain foods like beef consommé.
But like other basic tastes except sucrose, MSG improves the pleasantness only in the right concentration. An excess of MSG quickly ruins the taste of a dish. Although this concentration varies with the type of food, in clear soup the pleasantness score rapidly falls with more than 1 g of MSG per 100 ml.
Moreover, there is an interaction between MSG and
saltIn chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
(sodium chloride) and other umami substances such as nucleotides. All need to be in an optimum concentration for maximum palatability. With these properties, MSG can be used to reduce salt intake (
sodiumSodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
), which predisposes to hypertension, heart diseases and stroke. The taste of low-salt foods improves with MSG even with a 30% salt reduction. The sodium content (in
mass percent) of MSG is roughly one third (12%) as compared with sodium chloride (39%).
Other salts of glutamate have been used in low-salt soups, but with a lower palatability than MSG.
Safety
MSG has been used for more than 100 years to season food. During this period, extensive studies were conducted to elucidate the role, benefits and safety of MSG. At this point, International and national bodies for the safety of food additives consider MSG safe for human consumption as a flavor enhancer.
The "MSG symptom complex" was originally termed as the "Chinese restaurant syndrome" when anecdotally Robert Ho Man Kwok reported the symptoms he felt after an American-Chinese meal. Kwok suggested multiple reasons behind the symptoms, including alcohol from cooking with wine, the sodium content, or the MSG seasoning. But MSG became the focus and the symptoms have been associated with MSG ever since. The effect of wine or salt content was never studied.
With the years, the list of non-specific symptoms has grown on
anecdotalThe expression anecdotal evidence refers to evidence from anecdotes. Because of the small sample, there is a larger chance that it may be true but unreliable due to cherry-picked or otherwise unrepresentative of typical cases....
grounds. In normal conditions, we have the ability to metabolize without problems high levels of glutamate: in other words, it has a very low acute toxicity. The Oral lethal dose to 50% of subjects (LD50) is between 15 to 18 g/kg body weight in rat and mice respectively, 5 times greater than the LD50 of Salt (3 g/kg in rats). Therefore, the intake of MSG as a food additive and the natural level of glutamic acid in foods do not represent a toxicological concern in humans.
A report from the
Federation of American Societies for Experimental BiologyThe Federation of American Societies for Experimental Biology, abbreviated FASEB, is a non-profit organization that is the principal umbrella organization of U.S. societies in the field of biological and medical research. FASEB organizes academic conferences and publishes scientific literature...
(FASEB) compiled in 1995 on behalf of the United States Food and Drug Administration (FDA) concluded that MSG is safe when "eaten at customary levels" and although there seems to be a subgroup of apparently healthy individuals that respond with the MSG symptom complex when exposed to 3 g of MSG in the absence of food, causality by MSG has not been established because the list of MSG Symptom complex was based on testimonial reports.
This report also indicates that there is no data to support the role of glutamate in chronic and debilitating illnesses. A controlled double-blind multicenter clinical trial failed to demonstrate the relationship between MSG Symptom complex and the consumption of MSG in individuals believed to react adversely against MSG. No
statistical associationIn statistics, an association is any relationship between two measured quantities that renders them statistically dependent. The term "association" refers broadly to any such relationship, whereas the narrower term "correlation" refers to a linear relationship between two quantities.There are many...
has been demonstrated, there were few responses and they were inconsistent. Symptoms were not observed when MSG was given with food.
Adequately controlling for experimental bias includes a
double-blind placebo-controlled experimental designA randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
(DBPC) and the application in capsules because of the strong and unique after-taste of glutamates. In a study performed by Tarasoff and Kelly (1993) 71 fasting participants were given 5 g of MSG and then administered a standard breakfast. There was only one reaction, and it was to the placebo in a self-identified MSG sensitive individual. In a different study done by Geha et al. (2000), they tested the reaction of 130 subjects that reported sensitivity to MSG. Multiple DBPC trials were performed and only subjects with at least two symptoms proceeded. Only 2 people out of the whole study responded in all four challenges. Because of this low prevalence, the researchers concluded that the response to MSG was not reproducible.
Additional studies that have looked into whether MSG causes obesity have given mixed results. There have been several studies investigating an anecdotal link between MSG and
asthmaAsthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
; current evidence does not support any causal association.
Since glutamates are important
neurotransmitterNeurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
s in the human brain, playing a key element in learning and memory, there is ongoing study by neurologists about possible side–effects of MSG in food but no conclusive studies drawing any connections.
Australia and New Zealand
Food Standards Australia New Zealand (FSANZ) cites "overwhelming evidence from a large number of scientific studies" to explicitly deny any link between MSG and "serious adverse reactions" or "long-lasting effects", declaring MSG "safe for the general population". It does, however, describe that in less than 1% of the population, sensitive individuals may experience "transient" side effects such as "headache, numbness/tingling, flushing, muscle tightness, and generalised weakness" to a large amount of MSG taken in a single meal. People who consider themselves sensitive to MSG are encouraged to confirm this through an appropriate clinical assessment.
Standard 1.2.4 of the Australia and
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
Food Standards Code requires the presence of MSG as a food additive to be labeled in packaged foods. The label must bear the food additive class name (e.g.,
flavor enhancer), followed by either the name of the food additive,
MSG, or its E number,
621.
United States
Monosodium glutamate (MSG) 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 proteinsHydrolyzed protein is protein that has been hydrolyzed or broken down into its component amino acids. While there are many means of achieving this, two of the most common are prolonged boiling in a strong acid or strong base or using an enzyme such as the pancreatic protease enzyme to stimulate...
, autolyzed yeast, hydrolyzed yeast,
yeast extractYeast extract is the common name for various forms of processed yeast products made by extracting the cell contents ; they are used as food additives or flavourings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations. Monosodium...
,
soyThe soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
extracts, and protein isolate, which must be labeled with these common and usual names. Since 1998, MSG cannot be included in the term "spices and flavorings". The food additives
disodium inosinateDisodium inosinate 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.-Use as a food additive:...
and
disodium guanylateDisodium guanylate, also known as sodium 5'-guanylate and disodium 5'-guanylate, is a natural disodium salt of the flavor enhancer guanosine monophosphate . Disodium guanylate is a food additive with the E number E627...
, which are ribonucleotides, are usually used in synergy with monosodium glutamate-containing ingredients. However, the term 'natural flavor' is now used by the food industry when using glutamic acid (MSG without the sodium salt attached). Due to lack of FDA regulation, it is impossible to determine what percentage of 'natural flavor' is actually glutamic acid.
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 CookingOn Food And Cooking: The Science And Lore Of The Kitchen is a book by Harold McGee, published by Scribner in the United States in 1984 and revised extensively for a 2004 second edition...
, food enthusiast and author
Harold McGeeHarold McGee is an American author who writes about the chemistry, technique and history of food and cooking and has written two seminal books on kitchen science. His first book, On Food and Cooking: The Science and Lore of the Kitchen was initially published in 1984. A greatly revised second...
states that "[after many studies], toxicologists have concluded that MSG is a harmless ingredient for most people, even in large amounts."
See also
- Acceptable daily intake
Acceptable daily intake or ADI is a measure of the amount of a specific substance in food or drinking water that can be ingested on a daily basis over a lifetime without an appreciable health risk...
- Disodium glutamate
Disodium glutamate, abbreviated DSG, is a sodium salt of glutamic acid.-Formation:Disodium glutamate can be produced by neutralizing glutamic acid with two molar equivalents of sodium hydroxide ....
- Excitotoxicity
Excitotoxicity is the pathological process by which nerve cells are damaged and killed by excessive stimulation by neurotransmitters such as glutamate and similar substances. This occurs when receptors for the excitatory neurotransmitter glutamate such as the NMDA receptor and AMPA receptor are...
- List of food additives
- Monopotassium glutamate
Monopotassium glutamate is a compound with formula KC5H8NO4. It is a potassium acid salt of glutamic acid.It has the E number E622 and is used in foods as a flavor enhancer. It is a non-sodium MSG alternative....
External links