What is umami?

What is the taste of umami? Glutamate as a separate taste outside of food, dissolved in water, is not particularly palatable, and it is hard to define its quality. It is often described as “mouth-filling,” suggesting a texture. One of the common forms of glutamate, the flavor-enhancer mono-sodium glutamate (MSG), is somewhat salty (because of the sodium component), but it also has an additional quality. In human-behavioral studies of umami, when subjects are asked to sort a selection of taste substances into groups based on similarity, substances with an umami quality are shown to be very different from other taste qualities.⁸ Behavioural and physiological studies with animals also point to umami as a distinct taste. Thus, there are taste nerve fibers in the tongue, as well as neurons in the brain, that respond more strongly to MSG than to other taste substances. Most important, though, has been the discovery of a receptor in rodent taste buds that responds only to umami.⁹ As with similar receptors for sweet and bitter, umami receptors are the molecular mechanisms present in taste buds that convert a chemical signal into a specific electrical code that is transmitted to the taste areas of the brain.