Synthetically produced glutamates under the names hydrolyzed soy protein, autolyzed yeast, yeast extracts, protein concentrates and other additives add flavor to many of our processed foods, especially those looking for meaty type flavors. Labeling as MSG is only required when it is a direct ingredient. Glutamates can also be in ingredients labeled as vegetable broth or chicken broth.
MSG was used as a cheap, synthetic alternative to get the flavor 'umami' (the flavor of glutamic acid, which is found naturally in many savory foods) “Just like salt and sugar, it exists in nature, it tastes good at normal levels, but large amounts at high concentrations taste strange and aren’t that good for you,” says Dr. Chaudhari of the University of Miami, who has studied glutamates.
My favorite part:
"Nacho-cheese-flavor Doritos, which contain five separate forms of glutamate, may be even richer in umami than the finest kombu dashi (kelp stock) in Japan.
No wonder they taste so good."
Yes, MSG, the Secret Behind the Savor
New York Times, Published: March 5, 2008