Glutamic acid (Glu) is an amino acid with two carboxyl groups. The main component of MSG is the sodium salt of glutamic acid: monosodium glutamate.

Glutamic acid has the structural formula: HOOC-CH2-CH2-CH(NH2)-COOH

Sodium glutamate is: HOOC-CH2-CH2-CH(NH2)-COONa (which is more likely to be the case, with NaOOC-CH2-CH2-CH(NH2)-COONa,NaOOC-CH2-CH(NH2)-COONa,NaOOC-CH2-CH(NH2)-COONa,NaOOC-CH2-CH(NH2)-COONa. CH2-CH(NH2)-COOH is also possible)

MSG is a type of seasoning whose main ingredient is monosodium glutamate.

Monosodium glutamate is the sodium salt of the amino acid glutamic acid. It is an odorless, colorless crystal that disintegrates and melts at 232°C. Monosodium glutamate is very water soluble, dissolving 74 grams of monosodium glutamate in 100 milliliters of water.

The main function of MSG is to increase the freshness of food, and it is most used in Chinese cuisine, as well as in soups and sauces.

MSG was discovered and patented in 1909 by the Japanese company Ajinomoto (Ajinomoto). Pure MSG is a white crystalline powder. When MSG is dissolved in water (or saliva), it is rapidly ionized into free sodium ions and glutamate ions (glutamate ions are the anion of glutamic acid, which is a natural amino acid). It is important to note that if MSG is used at high temperatures above 100°C, the flavor agent monosodium glutamate will be converted to monosodium pyroglutamate, which is carcinogenic to humans. Also, if used in an alkaline environment, MSG will react chemically to produce a substance called disodium glutamate. So it is important to use and store it appropriately.

MSG stimulates specific taste receptors on the taste buds of the tongue, such as amino acid receptors T1R1/T1R3 or glutamate receptors, such as metabotropic glutamate receptors (mGluR4 and mGluR1), in order to bring about a taste sensation. This taste sensation is known as the freshness of the five flavors.