Monosodiumglutamate (MSG) is used as a flavor enhancer in a variety of foods prepared at home, in restaurants, and by food processors.
MSG is the sodium salt of the amino acid glutamic acid and a form of glutamate.
Glutamate itself is in many living things: It is found naturally in our bodies and in protein-containing foods, such as cheese, milk, meat, peas, and mushrooms.
Glutamate is an amino acid, and is a building block of protein.
To be used as seasoning, glutamate had to have some of the same physical characteristics which are found, for example, in sugar and salt: it had to be easily soluble in water but neither absorb humidity nor solidify.
Because monosodiumglutamate has no smell or specific texture of its own, it can be used in many different dishes where it naturally enhances the original flavor of the food.