If you're like me, you grew up learning that the tongue has taste buds for each of the four basic tastes: sweet, salty, sour, and bitter. Moreover you learned that each of these taste bud groups are localized on the tongue, with sweet being on the tip, salty on the sides, sour on the sides as well but farther back, and bitter at the back of the tongue. It turns out that not only do these locales not exist, but also that there is at least one additional basic taste and probably several more.

Umami is a Japanese word corresponding to a notion of meatiness or savoriness, and more specifically to the presence of free glutamates, also known as glutamic acid, an amino acid found naturally in many foods. Glutamates are found mostly in protein-rich foods, like cheeses and meats, and are also closely related to the synthetic flavor enhancer Monosodium glutamate (which is just the ionic form of the animo acid bonded to a sodium ion).

Umami was discovered in 1908 in Japan by Kikunae Ikeda, and is present in many fermented foods as soy sauce, fish sauce, or an old Parmigiano-Reggiano (the fermentation helps break down the proteins into small amino acid molecules). Tomatoes as well are high in glutamates, which probably explains why pasta with tomatoes and cheese is such a tasty treat! In fact, as it turns out, Parmigiano-Reggiano is one of the richest foods in glutamic acid. Per 100 g serving size, Parmesan cheese has 1200 mg of free glutamates, while beef has only 33 mg.

This explains why Parmesan rinds add so much to a vegetarian soup stock. It also explains why people like me gravitate so readily to fermented foods. It's all about the umami!