It's long been accepted in the Western world that there are four elements of taste: sweet, salty, sour and bitter. In 1908, Tokyo Imperial University researcher Kikunae Ikeda identified a fifth taste that he called "umami," a word that has no exact English translation, but which may be loosely interpreted as "delicious" or "savory"that is, the essence of flavor, another dimension. Ikeda determined that glutamic acid (glutamate) was the ingredient that produced this unique fifth taste and developed the seasoning monosodium glutamate (MSG) to provide the umami flavor. Ikeda concluded that, of the five tastes, umami and sweetness were the only two the palate perceives as singularly pleasant. Compared to the other four tastes, umami is exceedingly subtle, personifying more as an overall distinctive palate sensation than a taste.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.