Although according to studies Americans have been using the word “umami” for the past many years and it’s been in use in the English language since 1979, its definition remains elusive to many. If you’ll ask someone who thinks that they know what umami is, and they’ll just simply tell you it’s the “fifth taste,” after salty, sweet, sour, and bitter. It also has that deep, dark, meaty broth-like savoury intensity.
After the International Symposium, the physical and physiological studies showed that umami is independent of all the four classical tastes. Unlike classical basic tastes, umami is not a profound taste. Even a high concentration of umami substances does not bring a strong taste it harmonizes other tastes in foods and brings about mildness and deliciousness.
Definition of Umami
The Japanese define umami as “an over-all harmonious state of perfection where the ingredients come together, a rounded and harmonious dish.”
Umami, the word and its concept were coined, in the early twentieth century, by a Japanese chemist named Kikunae Ikeda.
Chemical Composition of Umami
Curious to know what was chemically responsible for the distinct and dominant flavour of dashi, the stock that’s a staple of Japanese cooking?
Ikeda examined closely the molecular composition of one of its main ingredients, a variety of seaweed. He determined that the cause was a single substance which is, glutamic acid, and he named its taste umami, from the Japanese word for delicious, umai; umami translates roughly to “deliciousness.”
Taste research from the past fifteen years has confirmed that molecular compounds in glutamic acid—glutamates—bind to specific tongue receptors; this is apparently, the reason for its distinct and unique taste. Any food in which glutamic acid occurs naturally or after cooking, ageing or fermentation is considered umami.
In crystalline form, glutamates are known as MSG(monosodium glutamate) which is nowadays also used as a flavour enhancer. Glutamate is a precursor of a protein and also a component of protein hydrolysate hence umami taste is a signal of protein.
World’s Most Important Taste
But for now, as the popular understanding of the concept discovered just over a hundred years ago continues to evolve, umami is more than just the sum of its glutamates, its a cultural cypher, a malleable, claimable standard of identity, innovation, and taste. Umami is a badge of pride, once Japanese, now universal.
Recent studies on taste physiology have been providing us with new knowledge regarding the mechanisms involved in taste reception. During eating, the taste substances, are received by the tongue receptors.
When receptors receive taste substances like, sucrose, caffeine, or glutamate, taste information is transferred to the brain, which results in the recognition the different tastes.
In 2000, some researchers in the USA discovered a receptor, metabotropic glutamate receptor type 4 variant (mGluR4), for glutamate on the tongue. Since then many researchers all around the world have found and identified new receptors for umami.
In 2006, a Japanese research team found that there were glutamate receptors, particularly metabotropic glutamate receptor type 1 variant (mGluR1), in the stomach tissue.
Other Varied Sources
The umami taste sends signals to the brain through taste nerves after activation of the tongue receptors, the umami receptors in the stomach also send signals through the vagus nerve to the brain.
5′-Inosinate from dried bonito  and 5′-guanylate from dried shiitake mushroom were also found to have the taste. Later its substances have been found universally in various foods. In humans, there is a large synergism between glutamate and 5′-inosinate or 5′-guanylate. Since glutamate and 5′-inosinate are contained in various foods, we taste it by their synergism in daily eating.
Hence it can be said that umami taste is induced by the synergism in human. Also, the dog showed a large synergism comparable to that in humans. Furthermore, mGluR1, mGluR4, and T1R1 + T1R3 were identified to be receptors for umami taste.
Other sources of the umami taste are potassium glutamate and calcium glutamate and the taste is actually due to glutamate anion. Similarly, the anion form of 5′-inosinic acid has an umami taste. In 1957, it was found that 5′-guanylate too has an umami taste. 5′-Guanylate is also a nucleotide that has phosphate residue.
Glutamate is contained universally in both plant and animal foodstuffs. Kombu and seaweed nori contain glutamate in very high content. Among vegetables, tomato and tamarillo, which is relative to tomato, contain glutamate in most high contents.
Animal foodstuffs also contain glutamate, but the contents are relatively lower than those in plant foodstuffs. Fermented foods contain a high content of glutamate brought about by the hydrolysis of proteins during fermentation. 5′-Inosinate is contained only in animal foodstuffs. Particularly, dried foodstuffs such as dried sardine and bonito contain 5′-inosinate in high content. 5′-Guanylate is contained mainly in mushrooms.
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