MSG, which stands for monosodium glutamate, is the sodium salt of glutamic acid.
Glutamic acid is actually a common amino acid that occurs naturally in a range of food like, tomatoes and dried mushrooms, and it’s what makes those foods taste so flavorful and good. It’s also found human breast milk.
MSG has an intense umami quality ― umami is essentially a savory flavor that doesn’t fall into the salty, sweet, sour or bitter categories of taste. It is basically umami in crystalline form.