Monosodium Glutamate

OVERVIEW

Monosodium glutamate (mon-oh-SOH-dee-yum GLOO-tuh-mate) is an almost completely odorless white crystalline powder. It is the sodium salt of a common amino acid called glutamic acid. An organic salt is a compound formed when an inorganic base, such as sodium hydroxide, reacts with an organic acid, such as glutamic acid.

Monosodium glutamate has been available as a commercial product for about a century. But the compound has been used in its natural form for much longer. The ancient Greeks and Romans used fish sauce, which contains glutamic acid as a natural ingredient, in their cooking. Later Europeans also used a form of the substance in a product known as garum.

KEY FACTS

OTHER NAMES:

Sodium glutamate; glutamic acid monosodium salt; MSG

FORMULA:

COOH(CH₂)₂CH(NH₂)COONa

ELEMENTS:

Carbon, hydrogen, oxygen, nitrogen, sodium

COMPOUND TYPE:

Organic salt

STATE:

Solid

MOLECULAR WEIGHT:

169.11 g/mol

MELTING POINT:

Not applicable; decomposes when heated

BOILING POINT:

Not applicable

SOLUBILITY:

Very soluble in water and ethyl alcohol

The German chemist Karl Heinrich Ritthausen (1826–1912) first identified glutamic acid in wheat gluten in 1866, and its chemical structure was first identified in 1890 by the German chemist Wolff. Then in 1908, the Japanese chemist Kikunae Ikeda (1864–1936) discovered the flavor-enhancing properties of glutamic acid. He found in seaweed broth a compound, later identified as glutamic acid, responsible for the unique taste of cheese, meat, and tomatoes. The compound was not sweet, salty, sour, or bitter, but instead had a rich meaty taste. He named the unusual flavor umami. Ikeda used glutamic acid crystals to make a seasoning, which he then patented. Like salt and sugar, it was readily soluble in water and could be stored for long periods of time without clumping. The seasoning was actually the sodium salt of glutamic acid, monosodium glutamate, first sold commercially in Japan under the name Ajinomoto, which means "essence of taste." The product was introduced into the United States shortly after World War II, and the U.S. Food and Drug Administration approved its use as a food additive in 1958.

HOW IT IS MADE

Glutamic acid in the form of glutamate exists in two forms: bound and free. The term bound glutamate refers to the glutamic acid that has combined with other amino acids to form proteins. The term free glutamate refers to the acid radical COOH(CH₂)₂CH(NH₂)COO⁻ formed when a single molecule of glutamic acid loses one hydrogen ion. Foods such as tomatoes, mushrooms, and cheeses are naturally high in glutamate, which is responsible for their strong flavors. Only the free form of glutamate enhances food flavors. In the human body, glutamate is a nonessential amino acid found in the brain, muscles, kidneys, liver, and other organs.

Monosodium glutamate is made commercially by the hydrolysis of the waste products of beet sugar refining, wheat, or corn gluten. Hydrolysis is the process by which a compound reacts with water to form two new compounds. In the preparation of monosodium glutamate, water breaks apart the proteins present in the raw materials used (such as wheat or corn gluten), freeing the amino acids of which they are made. The glutamic acid present in the proteins can then be separated from other amino acids present, then isolated and purified. Monosodium glutamate can also be made by a very similar process in which bacterial fermentation is used to break proteins down into their component parts, of which glutamic acid is one, a process which is now the primary means of production for the compound.

COMMON USES AND POTENTIAL HAZARDS

The sole use of monosodium glutamate is as a flavor enhancer in food products. Annual worldwide consumption of the additive has been estimate at about 1 million metric tons (1.1 million short tons). It is used primarily in a variety of Asian foods, including soups, canned foods, and processed meats.

Interesting Facts

• The flavor-enhancing qualities of monosodium glutamate are a function of its concentration in foods. At concentrations of less than about 0.5 percent, it enhances the flavor of a food product. At greater concentrations, it begins to make the food product taste bad.

Monosodium glutamate is considered safe for human consumption. It is on the U.S. Food and Drug Administration's Generally Recognized as Safe (GRAS) list. The GRAS list contains chemicals that have never been tested scientifically for safety, but are generally believed to be safe for human consumption. In 1987, health experts from the United Nations and the World Health Organization reviewed more than two hundred studies on MSG and determined that the compound is a safe food additive when used at customary levels.

In spite of these studies and rulings, many people believe that monosodium glutamate can have harmful health effects. They say that eating foods that include MSG can cause headache, nausea, sweating, rapid heartbeat, a burning sensation in the back of the neck, and/or tightness in the chest. Thus far, scientific studies have been unable to confirm the association of MSG with these symptoms.

Researchers theorize that the reactions may be the result of allergies to certain ingredients in the foods. In particular, they are likely to occur among people who have specific allergies to monosodium glutamate or who have asthma.

FOR FURTHER INFORMATION

"The Facts on Monosodium Glutamate." European Food Information Council. http://www.eufic.org/gb/food/pag/food35/food352.htm (accessed on October 17, 2005).

"FDA and Monosodium Glutamate (MSG)." U.S. Food and Drug Administration. http://www.cfsan.fda.gov/∼lrd/msg.html (accessed on October 17, 2005).

"Glutamate Facts, Information and On-Line Services." International Glutamate Information Service. http://www.glutamate.org (accessed on October 17, 2005).

"L-glutamic Acid, Sodium Salt." J. T. Baker. http://www.jtbaker.com/msds/englishhtml/g3975.htm (accessed on October 17, 2005).

monosodium glutamate (MSG) The sodium salt of glutamic acid, used to enhance the flavour of savoury dishes and often added to canned meat and soups. First isolated from seaweed by Tokyo chemist Kimunae Ikeda in 1908; he called it ajinomoto, meaning ‘the essence of taste’. First manufactured in the USA in 1934; before then it was imported from Japan. See also flavour enhancers; umami.

mon·o·so·di·um glu·ta·mate / ˌmänəˌsōdēəm ˈgloōtəˌmāt/ (abbr.: MSG) • n. a compound, HOOC(CH₂)₂(NH₂)COONa, that occurs naturally as a breakdown product of proteins and is used as a flavor enhancer in food (although itself tasteless). A traditional ingredient in Asian cooking, it was originally obtained from seaweed but is now mainly made from bean and cereal protein.

MSG • abbr. monosodium glutamate.

MSG See monosodium glutamate.