MSG in its pure form must be labeled. When it is added as an ingredient of another substance it need not be listed on the label. Example: When “broth” is sold as “broth,” its ingredients must be listed on its label. However, when “broth” (or any other product) is used as an ingredient in something else, its ingredients do not have to be disclosed.
The higher these substances appear on a list of ingredients, the more likely they are to contain MSG.
Definite sources of MSG include hydrolyzed protein, sodium caseinate or calcium caseinate, autolyzed yeast, yeast extract, or gelatin.
Probable sources of MSG include textured protein (TVP), carrageenan or vegetable gum, seasonings or spices, flavorings or natural flavorings, chicken, beef, pork, smoke flavorings, bouillon, broth or stock, barley malt, malt extract, malt flavoring, whey protein, whey protein isolate or concentrate soy protein, soy sauce or extract.