What is umami, actually?

Umami is the savory, meaty, mouth-filling taste that rounds out sweet, salty, sour, and bitter as the fifth basic taste, and it is a real, distinct perception with its own tongue receptors, not a vague culinary vibe. It was identified in 1908 by Japanese chemist Kikunae Ikeda, who isolated glutamate from kombu seaweed broth and named the taste umami, Japanese for pleasant savory taste, though Western science took most of a century to formally accept it. The receptors that detect it were confirmed only in the early 2000s.

Chemically, umami is the taste of certain amino acids and nucleotides, principally glutamate, plus compounds called inosinate and guanylate, which is why glutamate-rich foods taste so deep: aged parmesan, ripe tomatoes, mushrooms, cured meats, fish sauce, soy sauce, miso, and long-simmered broth. Those compounds also synergize, combining a glutamate source with an inosinate source, like parmesan on a tomato sauce, or dashi made from kombu and bonito, multiplies the savory effect far beyond either alone, a trick cuisines discovered by taste long before chemistry explained it. MSG is simply purified glutamate, which is why it delivers pure umami, and why the foods your palate calls rich and satisfying are usually the ones loaded with it.