I say discovered, but that's really a misnomer. All that really means is that Western scientists have confirmed a fifth taste receptor on the tongue that detects glutimate. The Japanese have known about it for years. The Chinese may have known about it, too, considering they seem to have started the whole MSG in food craze.
A taste is a sensation created by receptors on the tongue. The flavor of food is a combination of its taste, smell, texture, temperature, and perhaps a few other chemicals.
While there is no direct English translation of the word umami, it's often described as "meaty", "savory" or "broth-like". Traditionally, MSG has been considered a taste enhancer; it was thought to make the tongue more receptive to other tastes. Although the Japanese have considered umami a taste for a long time, only recently have taste receptors on the tongue been identified, which allowed umami to be officially classified as the fifth taste.
Glutamate gives some vegetables a "meaty" taste. For example, umami is the "meaty" or "savory" taste found in sauteed mushrooms, fermented foods and sauces such as soy sauce, and even fresh tomatoes. The umami taste is also high in cheese, shellfish, stocks, broths and even chocolate.
Most prominently associated with glutamate, ribonucleic acids can also impart an umami taste. Glutamate and ribonucleic acid may complement each other, creating an enhanced umami taste.
Glutamate is an amino acid. In its free form, called a salt of glutamic acid - monosodium glutamate or simply sodium glutamate - it imparts the umami taste to food. Glutamate is also an amino acid that makes up regular proteins, but when glutamate is bound in a protein, it doesn't really impart the umami taste.
Adding a pinch of MSG to your seasoning mix or or directly when cooking foods may generate a more "meaty" or "savory" flavor. Another option is to use foods naturally high in glutamate. This may be secret behind the use of stocks, broths and tomatoes in imparting a rich, savory flavor to dishes.
This is all well and good, but isn't MSG dangerous to our health? I've always thought so. The more research I do, though, the weirder it gets. Stay tuned …