E621 first referred to monosodium glutamate, or MSG, years before it meant related to furries. MSG is a flavor enhancer found in many foods. E621 is what’s known as the E number (a standardized code for substances in Europe) for MSG.

The origins of E621 can be traced back to its original meaning, which referred to monosodium glutamate (MSG), a flavor enhancer found in many foods. E621 is actually the standardized code for MSG used in Europe.

MSG is a white, odorless, crystalline powder commonly used as a food additive. In the food industry, it’s known as E621. It dissolves easily in water, separating into sodium and free glutamate (2). It’s made by fermenting carb sources like sugar beet, sugar cane, and molasses (3).

Flavour enhancer Monosodium glutamate (E621). Glutamic acid may be naturally found in various products (naturally fermented soy sauce, tomatoes, sea algae, ripened cheese, and others) and it imparts Umami (the fifth taste). Artificially produced monosodium glutamate is in the form of almost transparent flakes.