People taste umami through
taste receptors that typically respond to
glutamates and
nucleotides, 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).[6][7][8] 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.[1][9]
A
loanword from Japanese (うま味), umami can be translated as "pleasant savory taste".[10] This
neologism was coined in 1908 by Japanese chemist
Kikunae Ikeda from a
nominalization of umai (うまい) "delicious". The compound 旨味 (with mi (味) "taste") is used for a more general sense of a food as delicious.[11][12][13] There is no current English equivalent of umami; however, some close descriptions are "meaty", "savory", and "broth-like".[14]
Background
Scientists have debated whether umami was a basic
taste since Kikunae Ikeda first proposed its existence in 1908.[15][16] In 1985, the term umami was recognized as the scientific term to describe the taste of
glutamates and
nucleotides at the first Umami International Symposium in Hawaii.[17] Umami represents the taste of the
amino acidL-glutamate and 5'-
ribonucleotides such as
guanosine monophosphate (GMP) and
inosine monophosphate (IMP).[14] It can be described as a pleasant "
brothy" or "
meaty" taste with a long-lasting, mouthwatering and coating sensation over the tongue.
The sensation of umami is due to the detection of the
carboxylate anion of
glutamate in specialized receptor cells present on human and other animal
tongues.[18][19] Some 52
peptides may be responsible for detecting umami taste.[20] Its effect is to balance taste and round out the overall flavor of a dish. Umami enhances the palatability of a wide variety of foods.[21] Glutamate in acid form (glutamic acid) imparts little umami taste, whereas the
salts of
glutamic acid, known as
glutamates, give the characteristic umami taste due to their ionized state. GMP and IMP amplify the taste intensity of glutamate.[22]
Adding salt to the free acids also enhances the umami taste.[23]
Monosodium
L-aspartate has an umami taste about four times less intense than MSG, whereas
ibotenic acid and
tricholomic acid (likely as their salts or with salt) are claimed to be many times more intense.[23]
Discovery
Glutamate has a long history in cooking.[24] Fermented fish sauces (
garum), which are rich in glutamate, were used widely in ancient Rome,[25] fermented barley sauces (
murri) rich in glutamate were used in medieval
Byzantine and
Arab cuisine,[26] and fermented
fish sauces and
soy sauces have histories going back to the third century in China. In the late 1800s, chef
Auguste Escoffier, who opened restaurants in Paris and London, created meals that combined umami with
salty,
sour,
sweet, and
bitter tastes.[9] However, he did not know the chemical source of this unique quality.
Umami was first scientifically identified in 1908 by
Kikunae Ikeda,[27][28] a professor of the
Tokyo Imperial University. He found that
glutamate was responsible for the palatability of the broth from kombu seaweed. He noticed that the taste of kombudashi was distinct from sweet, sour, bitter, and salty and named it umami.[16]
Professor Shintaro Kodama, a disciple of Ikeda, discovered in 1913 that
dried bonito flakes (a type of tuna) contained another umami substance.[29] This was the ribonucleotide
IMP. In 1957, Akira Kuninaka realized that the ribonucleotide GMP present in
shiitake mushrooms also conferred the umami taste.[30] 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.[14]
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.
Properties
Umami has a mild but lasting aftertaste associated with salivation and a sensation of furriness on the tongue, stimulating the throat, the roof and the back of the mouth.[31][32] By itself, umami is not
palatable, but it makes a great variety of foods pleasant, especially in the presence of a matching aroma.[33] Like other basic tastes, umami is pleasant only within a relatively narrow concentration range.[31]
The optimum umami taste depends also on the amount of salt, and at the same time, low-salt foods can maintain a satisfactory taste with the appropriate amount of umami.[34] 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.[35] 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.[36][37]
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.[38] Some evidence exists to show umami not only stimulates appetite, but also may contribute to
satiety.[39]
Foods rich in umami components
Many foods are rich in the amino acids and nucleotides imparting umami. Naturally occurring glutamate can be found in meats and vegetables.
Inosine (
IMP) comes primarily from meats and
guanosine (
GMP) from vegetables. Mushrooms, especially dried
shiitake, are rich sources of umami flavor from guanylate. Smoked or fermented fish are high in inosinate, and
shellfish in
adenylate.[5]: 11, 52, 110 [40]
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.[42][2][5]
Most
taste buds on the tongue and other regions of the mouth can detect umami taste, irrespective of their location. (The
tongue map in which different tastes are distributed in different regions of the tongue is a common misconception.)
Biochemical studies have identified the
taste receptors responsible for the sense of umami as modified forms of
mGluR4,
mGluR1, and
taste receptor type 1 (
TAS1R1 +
TAS1R3), all of which have been found in all regions of the tongue bearing taste buds.[8][6][43] These receptors are also found in some regions of the
duodenum.[44] 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."[18]
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. They are
G protein-coupled receptors (GPCRs) with similar signaling molecules that include
G proteins beta-gamma,
PLCB2 and
PI3-mediated release of
calcium (Ca2+) from intracellular stores.[45] Calcium activates a so-called transient-receptor-potential cation channel
TRPM5 that leads to membrane
depolarization and the consequent release of
ATP and
secretion of
neurotransmitters including
serotonin.[46][47][48][49]
Cells responding to umami taste stimuli do not possess typical
synapses, but ATP conveys taste signals to gustatory nerves and in turn to the
brain that interprets and identifies the taste quality via the
gut-brain axis.[1][50][51]
Consumers and safety
Umami has become popular as a flavor with food manufacturers trying to improve the taste of low sodium offerings.[52] Chefs create "umami bombs", which are dishes made of several umami ingredients like
fish sauce.[2][9] Umami may account for the long-term formulation and popularity of
ketchup.[53] The United States
Food and Drug Administration has designated the umami enhancer
monosodium glutamate (MSG) as a safe ingredient. While some people identify themselves as
sensitive to MSG, a study commissioned by the FDA was only able to identify transient, mild
symptoms in a few of the subjects, and only when the MSG was consumed in unrealistically large quantities.[54] There is also no apparent difference in sensitivity to umami when comparing Japanese and Americans.[55]
Background of other taste categories
The five basic tastes (saltiness, sweetness, bitterness, sourness, and savoriness) are detected by specialized taste receptors on the tongue and
palateepithelium.[56] The number of taste categories in humans remains under research, with a sixth taste possibly including spicy or pungent.[57]
^Kawamura Y, Kare MR, eds. (1987). Umami: A basic taste. New York: Marcel Dekker.[page needed]
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^Smriga M, Mizukoshi T, Iwata D, Sachise E, Miyano H, Kimura T, Curtis R (August 2010). "Amino acids and minerals in ancient remnants of fish sauce (garum) sampled in the "Garum Shop" of Pompeii, Italy". Journal of Food Composition and Analysis. 23 (5): 442–46.
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^Nakamura E (July 2011). "One hundred years since the discovery of the "Kawamura_2016" taste from seaweed broth by Kikunae Ikeda, who transcended his time". Chemistry: An Asian Journal. 6 (7): 1659–63.
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^Roininen K, Lähteenmäki L, Tuorila H (September 1996). "Effect of umami taste on pleasantness of low-salt soups during repeated testing". Physiology & Behavior. 60 (3): 953–8.
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^Huynh HL, Danhi R, Yan SW (January 2016). "Using Fish Sauce as a Substitute for Sodium Chloride in Culinary Sauces and Effects on Sensory Properties". Journal of Food Science. 81 (1): S150-5.
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^Agostoni C, Carratù B, Boniglia C, Riva E, Sanzini E (August 2000). "Free amino acid content in standard infant formulas: comparison with human milk". Journal of the American College of Nutrition. 19 (4): 434–8.
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^Clapp TR, Yang R, Stoick CL, Kinnamon SC, Kinnamon JC (January 2004). "Morphologic characterization of rat taste receptor cells that express components of the phospholipase C signaling pathway". The Journal of Comparative Neurology. 468 (3): 311–21.
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