Monosodium Glutamate (MSG)

At room temperature, MSG (C₅H₈NNaO₄• H₂O) is a salt, which typically exists as a white, odorless crystalline powder that is soluble in water and alcohol. It does not have a melting point per se, but it decomposes when it is heated. When crystals of MSG are created in a water solution, they develop in the shape of rhombic prisms.

The molecules of MSG can exist in two different forms known as isomers. These isomers are chemically identical, but physically different because their molecular structures are dissimilar. In fact, the elements on the two MSG isomers, known as stereoisomers, are arranged in such a way that if they were placed next to each other, they would appear as mirror images. The isomers of MSG have different physiological effects, and only one of them, known as the L form, has flavor enhancing properties.

Although MSG is tasteless by itself, it is a flavor enhancer that can be used to improve the taste of meat, fish, fowl, vegetables, and soup. It is said to provide a unique flavor that is neither bitter, sour, sweet, or salty. Typically employed at concentrations of 0.2-0.9%, it is used extensively by the food industry in canned, frozen, and dried foods and Oriental food. It has also been used, with sugar, to improve the palatability of bitter drugs.