Umami tasteThe fifth taste, known as umami, is central to Asian cuisine, and has a rich savoury flavour characteristic of cheese, cooked meat, mushrooms, soy, and ripe tomatoes.
Umami taste is common in foods that contain high levels of glutamate, inosine monophosphate (IMP) and guanosine monophosphate (GMP). Two important characteristics of umami are synergism and interactions with other tastes, e.g. the suppression of bitterness.
Since umami has its own receptor, rather than a combination of the traditionally recognised taste receptors, scientists now consider umami to be a distinct taste. Umami-tasting compounds are perceived through a G protein-coupled receptor (GPCR) heterodimer composed of TAS1R1 (taste receptor type 1, member 1) and TAS1R3 (taste receptor type 1, member 3). Although the human umami receptor is very receptive, responding to all 20 amino acids, it is particularly receptive to glutamate.
Glutamate is a naturally occurring amino acid found in many different types of food and, in the form of monosodium glutamate (MSG), food additives. MSG is used as a flavour enhancer commonly found in canned soups and vegetables, and processed meats. It can also be found naturally in many foods, including tomatoes, cheeses, mushrooms, seaweed and soy.
While some people report adverse reactions to MSG such as headaches or nausea, research has found no definitive link between MSG and these symptoms. Therefore, MSG is generally considered safe at the levels commonly found in the typical diet.