glutamic acid

In 1908 the Tokyo chemist Kikunae Ikeda worked out the taste of a kombu and dried bonito broth and proposed a fifth basic taste alongside sweet, sour, salty and bitter, writing that he wished "to call this taste umami for convenience." The taste was free glutamate, and this library serves it constantly: cooked out of beef in abo shalhoob, drawn from lentils in harak osbao, concentrated by salt and time in lamb guanciale, and stacked three ways at once, from pecorino, parmesan and cured lamb, in the carbonara.

Glutamic acid is C₅H₉NO₄, an amino acid with a second acid group on its side chain, and it is the free form, unbound from any protein, that the tongue registers. Cooking and fermentation are what set it loose: proteolysis breaks proteins down into peptides and free amino acids, and in an inoculated soy sauce moromi, glutamate content rose from 215.9 to 509.4 milligrams per hundred millilitres over ten days. In a hard Italian cheese the same process runs slowly enough to read like a clock: pyroglutamic acid, the cyclised form of glutamic acid, climbs to about half a gram per hundred grams in Grana Padano and Parmigiano Reggiano, tracking the wheel's age with an R-squared of 0.94.

Glutamate alone does not taste of much; it wants sodium alongside it, and salt's real trick in a savoury dish is not adding flavour but clearing the bitterness out of glutamate's way, giving it, in one Journal note's phrase, a clean run. That is what a spoonful of Parmesan, a splash of soy sauce or a long-simmered broth is doing to a pot. In this library it is the savoury backbone of seven recipes, from the beef and lentils of two skillet dishes to the broths behind a mansaf and a molokhiya, the salt-cured lamb of a guanciale, and the three stacked sources apiece in a carbonara and a Japanese curry.