Umami's food-to-brain protocol varies in certain ways from that of other tastes, starting with the receptor cells. The sensory cells that recognize sweet and bitter tastes and umami are called G protein-coupled receptors, or GPCRs. Sour and salty taste components in contrast, are thought to pass through ion channels, based on positive- and negative-charged molecules [source: Monell].
Three types of receptors cells are known to respond to the combination of inosinate, guanylate and MSG; there are likely more. It's theorized that these receptors not only sense these compounds but also "hold on" to them longer than receptors that target other tastes [source: Marcus]. This would explain umami's ability to reveal nuances of other tastes when experienced together – to make a sweet food not merely sweeter, for instance, but differently sweet. Think of apple pie topped with cheese, prosciutto-wrapped figs or chocolate-coated bacon.
Another remaining question concerns umami's evolutionary role. It's generally accepted that before humans knew anything about health or nutrition, tastes were a guide to which things were good to eat and which ones could kill them. People like sweet tastes because sweet foods, such as fruits and some vegetables, provide carbohydrates and vitamins that can only be obtained by eating them. The umami sensation is provided by proteins, a vital nutrient. But the one amino acid most closely associated with umami, glutamate, is readily made in the human body [source: Geiling].
Other proteins that aren't produced in the body are equally important, however. These are the essential proteins, so named because it's essential that they are included in the diet. Protein itself has no taste. It's the amino acids that, when "freed" from the protein molecule, register on the taste buds. Free amino acids result from processes that break down protein, such as cooking, drying and fermenting [source: Koetke].
Freeing amino acids also starts their digestion and metabolization in the body and some anthropologists suggest this is why humans have advanced beyond other species in brain power (as far as we know). Cooking speeds the breaking down and thus the digestion of amino acids and other nutrients, which enabled human brains to develop more and more quickly [source: Kiger].
The food industry has long known of the profits of using umami. Read on to see how it's popping up everywhere, from fast food to fine dining.