Sweet, bitter, sour, salt… and umami. The fifth taste.
Psychophysicists have long suggested the existence of four taste ‘primaries’, referred to as the basic tastes. Umami is now accepted as the fifth basic taste, exemplified by the non-salty sensations evoked by some free amino acids such as monosodium glutamate.
Umami is a Japanese word meaning savory, a “deliciousness” factor deriving specifically from detection of the natural amino acid, glutamic acid, or glutamates common in meats, cheese, broth, stock, and other protein-heavy foods. The action of umami receptors explains why foods treated with monosodium glutamate (MSG) often taste “heartier”.