Over the millennia, this ancient theory remained largely unquestioned. The tongue was seen as a mechanical organ in which the qualities of foods were impressed upon its papillaed surface. The discovery of taste buds in the nineteenth century gave new credence to this theory. Under a microscope, these cells looked like keyholes into which our chewed food might fit, thus triggering a taste sensation. By the start of the twentieth century, scientists were beginning to map the tongue, assigning each of the four flavors to a specific area. The tip of the tongue loved sweet things, while the sides preferred sour. The back of the tongue was sensitive to bitter flavors, and saltiness was sensed everywhere. The sensation of taste was that simple.

Unfortunately for Ikeda, there seemed to be no space left on the tongue for his delicious flavor. Umami, these Western scientists said, was an idle theory that related solely to Japanese food, a silly idea concerned with something called deliciousness, whatever that was. And so while cooks the world over continued to base entire cuisines on dashi, Parmesan cheese, tomato sauce, meat stock and soy sauce (all potent sources of L-glutamate), science persisted in its naive and unscientific belief in four, and only four, tastes.

Despite the willful ignorance of science, Ikeda’s idea gained a certain cult following, and with time other pioneers began investigating their local cuisines and found their own densities of L-glutamate. Everything from aged cheese to ketchup was rich in this magic amino acid. Umami even seemed to explain some of the more perplexing idiosyncrasies of the cooking world: Why do so many cultures, beginning with ancient Rome, have a fish sauce? (Salted, slightly rotting anchovies are like glutamate speedballs. They are pure umami.) Why do we dip sushi in soy sauce? (The raw fish, being raw, is low in umami, since its glutamate is not yet unraveled. A touch of soy sauce gives the tongue the burst of umami that we crave.) Umami even explains (although it doesn’t excuse) Marmite, the British spread made of yeast extract, which is just another name for L-glutamate.

Of course, umami is also the reason that meat—which is nothing but amino acid—tastes so darn good. If cooked properly, the glutamate in meat is converted into its free form and can be tasted. This also applies to cured meats and cheeses. As a leg of prosciutto ages, the amino acid that increases the most is glutamate. Parmesan, meanwhile, is one of the most concentrated forms of glutamate, weighing in at more than 1,200 mg per 100 g. (Only Roquefort cheese has more.) When we add an aged cheese to a pasta, the umami in the cheese somehow exaggerates the umami present elsewhere in the dish. (This is why tomato sauce and Parmesan are such a perfect pair. The cheese makes the tomatoes more tomato-like.) A little umami goes a long way.