L-(+)Sodium glutamate

L-(+)sodium glutamate (monosodium L-glutamate, MSG) has a unique taste, known as “umami”, which is different from the four basic tastes of sweet, salty, sour, and bitter.
MSG is used in large quantities as a flavor enhancer throughout the world. MSG is not a direct taste enhancer but a complex flavor enhancer for gravies, meats, poultry, sauces, and in other combinations. MSG is also used to enhance the taste of tobacco and to treat hepatic coma. As a salt of amino acid, MSG is also safe in practices of use and concentration in cosmetics, such as skin care products.

[1] Tetsuya Kawakita, L-Monosodium Glutamate (MSG), Kirk-Othmer Encyclopedia of Chemical Technology, 2000
[2] Leslie T. Webster and Charles S. Davidson, The effect of sodium glutamate on hepatic coma, The Journal of Clinical Investigation, 1956, vol. 35, 191-199
[3] DV Belsito, Safety Assessment of α-Amino Acids as Used in Cosmetics

History of development. The best known and most widely used flavor enhancer is monosodium glutamate (MSG). In 1866, a German chemist, Ritthausen, isolated glutamic acid. Later, another chemist converted the acid to a sodium salt, monosodium glutamate. In doing their work, neither had any interest in flavor.
More than 40 years later, in 1908, a Japanese chemist at the University of Tokyo, Dr. Kikunae Ikeda, discovered the flavor enhancing properties of MSG. Dr. Ikeda had set out to find out why and how a certain seaweed, Laminaria japonica, affected flavor. Japanese cooks had used this seaweed for centuries to improve the flavor of soups and certain other foods. Dr. Ikeda discovered that the ingredient in the seaweed that made the difference was MSG, and that it had an unusual ability to enhance or intensify the flavor of many high protein foods.
After isolating MSG, Dr. Ikeda developed a process for extracting it from wheat flour and other flours. Working with the Japanese chemical company, Suzuki and Co., he supervised the construction of a plant and, as a partner with the company, began commercial production of MSG in 1909.
There were several attempts to produce MSG in the United States in the years following, but it was not until the 1940s that large- scale MSG production began in this country. By 1968, U.S. production had grown to 46 million pounds per year. The latest production figures (1987) reported 18.6 million pounds per year.
Flavor and enhancing properties. At one time, it was felt that MSG had a somewhat meaty flavor and that this flavor was a factor in its ability to intensify the flavors of other foods, particularly protein-rich foods. It was discovered, however, that the meaty taste came rather from contaminants in the crude glutamate, and when these contaminants were sharply reduced, the flavor characteristic also was reduced considerably.
MSG is not flavorless. In large enough concentrations, or by itself, it has been found to have a taste of its own, sometimes described as sweet-saline. There are some, in fact, who feel that MSG is nothing more than a seasoner which gains its effect by combining with and intensifying the flavors of the foods to which it is added. However, to say that MSG only intensifies the flavor of foods is too simplistic. When monosodium glutamate is added to food, several specific flavor characteristics are enhanced - such as impact, body or fullness, continuity, mouth fullness, mildness, and complexity. Glutamate also harmonizes the wide range of flavors present in sauces, soups and casseroles, promoting a highly blended and full-bodied perception of flavor.
The savory taste of glutamate is to tomatoes, cheese, and meat what sweetness is to sugar, sourness is to lemons, saltiness is to anchovies and bitterness is to coffee. Just as each of these foods has a distinctive taste, food high in glutamate has a basic and independent taste. In China and Japan, there is a concept for this independent taste, which they call Xian-Wei (China) and Umami (Japan). Current research has found more than 40 umami substances of which glutamate is most common. In fact, umami is an integral part of cuisines throughout the world and has been described by Westerners as “savory,” “broth-like” and “meaty.”.
Production. MSG is commonly produced using a fermentation process using a glucose (often sugar molasses) as a starting substance. Once the glucose is converted to glutamic acid, the glutamic acid is filtered, dissolved and converted to monosodium glutamate by neutralization with sodium hydroxide. The monosodium glutamate solution is decolorized. Monosodium glutamate is then crystallized, dried, sieved, packed and shipped.

Monosodium glutamate, the best-known and most widely used flavor enhancer, is practically odorless and may have either a slightly sweet or slightly salty taste. Addition of monosodium glutamate to food enhances several specific flavor characteristics, such as impact, body of fullness, continuity, mouth fullness, mildness and complexity. For a detailed description of this compound refer to Burdock (1997)

Monosodium glutamate occurs as white free-flowing crystals or a crystalline powder. It is practically odorless and has a meat-like taste.

Colorless powder

Reported found in certain seaweeds including Laminaria japonica

MSG is used as a food additive, mainly in oriental cuisine, to enhance and impart a meaty flavor.

sodium glutamate is an amino acid with skin-conditioning, odormasking, and hair-conditioning action.

Flavor enhancer for foods in concentration of about 0.3%.

ChEBI: An optically active form of monosodium glutamate having L-configuration.

Monosodium glutamate is the monosodium salt of the naturally occurring L-form of glutamic acid. It is commonly manufactured by fermentation of carbohydrate sources such as sugar beet molasses. In general, sugar beet products are used in Europe and the USA. M 452 Monosodium Glutamate Other carbohydrate sources such as sugar cane and tapioca are used in Asia.

Monosodium glutamate is commonly produced by a fermentation process using glucose (often sugar molasses) as a starting substance. Once the glucose is converted to glutamic acid, it is filtered, dissolved and converted to monosodium glutamate by neutralization with sodium hydroxide. The monosodium glutamate solution is decolorized and then crystallized, dried, sieved, packed and shipped

White or off-white crystalline powder with a slight peptone-like odor. pH (0.2% solution)7.0.

Water soluble.

L-(+)Sodium glutamate is an amide. Amides/imides react with azo and diazo compounds to generate toxic gases. Flammable gases are formed by the reaction of organic amides/imides with strong reducing agents. Amides are very weak bases (weaker than water). Imides are less basic yet and in fact react with strong bases to form salts. That is, they can react as acids. Mixing amides with dehydrating agents such as P2O5 or SOCl2 generates the corresponding nitrile. The combustion of these compounds generates mixed oxides of nitrogen (NOx).

Flash point data are not available for L-(+)Sodium glutamate, but L-(+)Sodium glutamate is probably combustible.

Monosodium glutamate is used in oral pharmaceutical formulations as a buffer and a flavor enhancer. For example, it is used with sugar to improve the palatability of bitter-tasting drugs and can reduce the metallic taste of iron-containing liquids. It has also been used in subcutaneous live vaccine injections such as measles, mumps, rubella and varicella-zoster live vaccine (ProQuad). However, the most widespread use of monosodium glutamate is as a flavor enhancer in food products. Typically, 0.2–0.9% is used in normally salted foods, although products such as soy protein can contain 10–30%. The use of monosodium glutamate in food products has been controversial owing to the apparently high number of adverse reactions attributed to the substance, which gives rise to the so-called ‘Chinese Restaurant Syndrome’.
The current consensus is that there is no clinically compelling evidence to suggest that monosodium glutamate may be harmful at the current levels used in foods.

Monosodium glutamate(MSG) is a food additive and an environmental agent, that can affect inflammation.

Moderately toxic by intravenous route. Mildly toxic by ingestion and other routes. An experimental teratogen. Other experimental reproductive effects. Human systemic effects by ingestion and intravenous routes: somnolence, hallucinations and distorted perceptions, headache, dyspnea, nausea or vomiting, dermatitis. The cause of "Chnese restaurant syndrome." When heated to decomposition it emits toxic fumes of NOx and Na2O.

Monosodium glutamate is widely used in foods and oral pharmaceutical formulations. It is generally regarded as moderately toxic on ingestion or intravenous administration. Adverse effects include somnolence, hallucinations and distorted perceptions, headache, dyspnea, nausea or vomiting, and dermatitis. The lowest lethal oral dose in humans is reported to be 43 mg/kg.The use of monosodium glutamate in foods has been controversial due to the so-called ‘Chinese Restaurant Syndrome’, although it is generally regarded as safe at intake levels of up to 6 mg/kg bodyweight.In Europe, total glutamate intake from food ranges from 5–12 g/day.
There has been a report of a foreign body granuloma caused by monosodium glutamate after a BCG vaccination.

The industrial production of glutamic acid is primarily carried out in the form of monosodium glutamate (MSG), mainly through microbial fermentation. This process has replaced earlier methods such as protein hydrolysis and chemical synthesis. In this modern and efficient production method, specific bacterial strains, such as Corynebacterium glutamicum, are cultivated in large fermenters using carbohydrates such as sugarcane, sugar beets, or molasses as raw materials. These bacteria secrete glutamic acid into the culture medium. After fermentation, the glutamic acid is separated, purified, and then neutralized with sodium hydroxide, ultimately yielding the product—monosodium glutamate (MSG).

MSG is a white, odorless powder with high water solubility. If released into the air, it remains in the particulate phase until removed by deposition.

Aqueous solutions of monosodium glutamate may be sterilized by autoclaving. Monosodium glutamate should be stored in a tight container in a cool, dry place.

Although several mechanisms have been proposed to be responsible for causing CRS, none has been extensively studied. One hypothesis has been that the effects are due to an immediate hypersensitivity reaction. Since no immunoglobulin E (IgE)-mediated reaction has been documented, there is no direct evidence that this is the case. Another hypothesis is that vitamin B6 deficiency plays a role in the response because the symptoms were prevented by supplementing individuals with the vitamin. Since glutamate can be converted to acetylcholine by the tricarboxylic acid cycle, it has also been proposed that the effects are due to an increase in acetylcholine levels. It has been noted that after MSG ingestion, there is a decrease in the levels of cholinesterase (the enzyme that breaks down acetylcholine). Due to inadequate investigations, it is not currently known if any or all of these mechanisms are responsible for CRS. The neurotoxicity of MSG has only been demonstrated in rodent species and rabbits after exposure to very large doses. The neurotoxic effect has been attributed to excitotoxicity.

GRAS listed. Accepted in Europe for use as a food additive in certain applications. Included in the FDA Inactive Ingredients Database (oral syrup). Included in nonparenteral medicines licensed in the UK. Included in subcutaneous vaccine injections.