Umami ( from ), or savoriness, is one of the five basic tastes. It is characteristic of and cooked meats.
People taste umami through that typically respond to Glutamic acid and nucleotide, which are widely present in meat broths and fermented products. Glutamates are commonly added to some foods in the form of monosodium glutamate (MSG), and nucleotides are commonly added in the form of disodium guanylate, inosine monophosphate (IMP) or guanosine monophosphate (GMP). Since umami has its own receptors rather than arising out of a combination of the traditionally recognized taste receptors, scientists now consider umami to be a distinct taste.
Foods that have a strong umami flavor include meats, shellfish, fish (including fish sauce and preserved fish such as Maldives fish, katsuobushi, sardines, and anchovies), dashi, , Edible mushroom, hydrolyzed vegetable protein, meat extract, yeast extract, kimchi, , and soy sauce.
In 1908, Kikunae Ikeda of the University of Tokyo scientifically identified umami as a distinct taste attributed to glutamic acid. As a result, in 1909, Ikeda and Saburōsuke Suzuki founded Ajinomoto which introduced the world's first umami seasoning: monosodium glutamate (MSG), marketed in Japan under the name "Ajinomoto." MSG subsequently spread worldwide as a seasoning capable of enhancing umami in a wide variety of dishes.
In 2000, researchers at the University of Miami identified the presence of umami receptors on the tongue, and in 2006, Ajinomoto’s research laboratories found similar receptors in the stomach.
Umai can also be written as , leading to the alternative form , also pronounced umami. While the forms are often used interchangeably, in the 1980s Japanese researchers suggested that should be used for the flavor while is a more general sense of a food being delicious.
Specialized taste bud cells detect the chemical species perceived as umami by humans. Glutamate in acid form (glutamic acid) imparts little umami taste, whereas the salts of glutamic acid, known as , give the characteristic umami taste due to their ionized state. GMP and IMP amplify the taste intensity of glutamate. Adding salt to the free acids also enhances the umami taste. It is disputed whether umami is truly an independent taste because standalone glutamate without table salt ions (Na+) is perceived as sour; sweet and umami tastes share a taste receptor subunit, with salty taste blockers reducing discrimination between monosodium glutamate and sucrose; and some people cannot distinguish umami from a salty taste.
Monosodium L-aspartate has an umami taste about a quarter as intense as MSG, whereas ibotenic acid and tricholomic acid (likely as their salts or with salt) are claimed to be many times more intense. Peptides can also generate an umami taste, with 52 of them being known to do so as of 2017 (20 of them are questionable).
Umami was first scientifically identified in 1908 by Kikunae Ikeda, (partial translation of ) a professor of the Tokyo Imperial University. He found that glutamic acid was responsible for the palatability of the broth from kombu seaweed. He noticed that the taste of kombu dashi was distinct from sweet, sour, bitter, and salty and named it umami.
Shintaro Kodama, a disciple of Ikeda, discovered in 1913 that Katsuobushi (a type of tuna) contained another umami substance. This was the ribonucleotide IMP. In 1957, Akira Kuninaka realized that the ribonucleotide GMP present in shiitake mushrooms also conferred the umami taste. One of Kuninaka's most important discoveries was the synergistic effect between ribonucleotides and glutamate. When foods rich in glutamate are combined with ingredients that have ribonucleotides, the resulting taste intensity is higher than would be expected from merely adding the intensity of the individual ingredients.
This synergy of umami may help explain various classical food pairings: the Japanese make dashi with kombu seaweed and dried bonito flakes; the Chinese add Chinese leek and Chinese cabbage to chicken soup, as do Scots in the similar Scottish dish of cock-a-leekie soup; and Italians grate the Parmigiano-Reggiano cheese on a variety of different dishes.
The optimum umami taste also depends on the amount of salt, and at the same time, low-salt foods can maintain a satisfactory taste with the appropriate amount of umami. One study showed that ratings of pleasantness, taste intensity, and ideal saltiness of low-salt soups were greater when the soup contained umami, whereas low-salt soups without umami were less pleasant. Another study demonstrated that using fish sauce as a source of umami could reduce the need for salt by 10–25% to flavor such foods as chicken broth, tomato sauce, or coconut curry while maintaining overall taste intensity.
Some population groups, such as the elderly, may benefit from umami taste because their taste and smell sensitivity may be impaired by age and medication. The loss of taste and smell can contribute to poor nutrition, increasing their risk of disease. Some evidence exists to show umami not only stimulates appetite, but also may contribute to satiety.
Generally, umami taste is common to foods that contain high levels of glutamic acid, IMP and GMP, most notably in fish, shellfish, cured meats, , Edible mushroom, (e.g., ripe , Chinese cabbage, spinach, celery, etc.), green tea, hydrolyzed vegetable protein, and fermented and aged products involving bacterial or yeast cultures, such as , , fish sauce, soy sauce, natto, nutritional yeast, and such as Vegemite and Marmite.
Studies have shown that the amino acids in breast milk are often the first encounter humans have with umami. Glutamic acid makes up half of the free amino acids in breast milk.
Furthermore, single glutamate (glutamic acid) with no table salt ions (Na+) elicits sour taste and in psychophysical tests, sodium or potassium salt cations seem to be required to produce a perceptible umami taste.
Sweet and umami tastes both utilize the taste receptor subunit TAS1R3, with salt taste blockers reducing discrimination between monosodium glutamate and sucrose in rodents.
If umami doesn't have perceptual independence, it could be classified with other tastes like fat, carbohydrate, metallic, and calcium, which can be perceived at high concentrations but may not offer a prominent taste experience.
Receptors mGluR1 and mGluR4 are specific to glutamate whereas TAS1R1 + TAS1R3 are responsible for the synergism already described by Akira Kuninaka in 1957. However, the specific role of each type of receptor in taste bud cells remains unclear. All three receptors work together to produce the taste sensation.
The ATP released by the "Type II" cell is detected by P2X receptors on nearby afferent gustatory nerve fibers and P2Y receptors on adjacent taste cells. P2X appears to be indispensable for the transduction of umami, so this is probably the main route for umami signals. "Type III" cells, which directly connect to the nerve synapses, also respond to the released ATP by releasing neurotransmitters. One of these neurotransmitters, serotonin, regulates the release of ATP by the type II cells.
The Tas1r1-Tas1r3 receptor of mice is activated by a wide range of free L-amino acids, but not acidic ones such as glutamate.
The lineage of aquatic mammals including dolphins and sea lions have no functional Tas1r1, and neither do giant pandas. They cannot generate a functional Tas1r1-Tas1r3 receptor as a result.
Taste receptors
These receptors are also found in some regions of the duodenum. A 2009 review corroborated the acceptance of these receptors, stating, "Recent molecular biological studies have now identified strong candidates for umami receptors, including the heterodimer TAS1R1/TAS1R3, and truncated type 1 and 4 metabotropic glutamate receptors missing most of the N-terminal extracellular domain (taste-mGluR4 and truncated-mGluR1) and brain-mGluR4."
Downstream signaling
TAS1R1 + TAS1R3
mGluR1 and mGluR4
Beyond the tongue
In other animals
Consumers and safety
Background of other taste categories
See also
Further reading
External links
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