Kikunae Ikeda has done a lot of research on soup in the human diet.
The Japanese chemist has been studying a Japanese soup (dashi) made from seaweed and dried fish fillets. Japanese dashi has a very distinctive flavor – fresh, delicious and tasty. Ikeda has been trying to isolate the molecules that give the soup its distinctive flavor from the delicious broth in a long and difficult isolation operation in a chemical laboratory. He was convinced that there was a connection between the shape of the molecules and the taste of the soup as perceived by humans.
However, since the 19th century had only just ended and the 20th century had just begun, there was not yet a great deal of evidence to support his view.
In the end, Ikeda succeeded in isolating an important flavor molecule from the seaweed in Japanese soup: glutamic acid, an amino acid. This is an important component of protein. In a 1909 paper, Ikeda, a professor at Tokyo Imperial University, suggested that this wonderful flavor produced by glutamic acid should become a basic flavor equivalent to sour, sweet, bitter and salty. He named it “umami,” a Japanese word meaning “delicious.
It cannot be said that his idea received thunderous applause from his peers around the world at the time. First of all, Ikeda’s paper had been in Japanese until 2002, when it was finally translated into English. In addition, unlike other flavors, freshness does not increase linearly with the amount of glutamate and other substances that produce freshness, unlike sweetness.
If we compare flavors to colors, ‘freshness’ is yellow and sweetness is red,” Ikeda says in his paper. But this is not the exact scientific description.
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Seaweed
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Seaweed is a key component of Japanese cuisine and is closely associated with freshness (Credit: Getty Images)
But more than 100 years later, scientists around the world now recognize that umami is real and is one of the basic flavors of food, along with several others. Freshness is not only found in seaweed, but we also find it in tomatoes, meat, soup, cheese and many other foods. For many years, this mysterious and intense flavor was hidden from view. So, how did it finally get recognized?
In the last few decades, scientists have begun to study how freshness works. Each new discovery has brought more attention to Ikeda’s claims. For example, researchers have discovered two other molecules that produce freshness: inosinic acid, which gives bonito flakes their delicious flavor, and guanosine, which gives dried shiitake mushrooms their delicious flavor.
Interestingly, the synergistic effect of putting the two flavor-producing molecules in the same dish resulted in an enhanced flavor. A soup with both bonito flakes (inosinic acid) and seaweed (glutamic acid) is much fresher than a soup with only bonito flakes or seaweed. Cooking beef (inosinate) and tomatoes (glutamate) together will produce a similar effect.
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Some people think that the freshness may just be a savory taste. After all, the two flavors are often found together. But researchers have found that removing the ingredients that produce the fresh taste does make a big difference in the taste of food. Looking further at the nerves that send information from the mouth to the brain, the researchers found that fresh and salty flavors work through different channels.
Ikeda’s point of view was finally recognized, in large part, probably because of a discovery about 20 years ago: taste buds have specific receptors to receive amino acids. Several research teams have now published their findings on these receptors. By modulation, these receptors are targeted to adhere to glutamate and other synergistic taste molecules.
Bonito Fillet
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Bonito flakes contain inosinic acid, which is thought to be one of the compounds that produce the taste (Credit: Getty Images)
At some point, it is not surprising that our bodies have evolved to be able to feel the taste of amino acids, as they are vital to our survival. The glutamic acid content of breast milk is roughly the same as the Japanese soup Ikeda studied, so we may have been familiar with the taste long before we could walk.
Ikeda found a condiment manufacturer and began producing his own line of fresh flavored condiments. “I think it’s time to revolutionize the production of this important condiment,” he wrote at the end of his 1909 essay, hoping that better-tasting food would improve people’s nutrition. Aji-No-Moto, a powdered monosodium glutamate, is still being produced today. Despite occasional rumors that too much MSG can cause headaches and other health problems, the U.S. Food and Drug Administration has found no evidence to support such claims. So far, MSG is known to do little more than make food taste better.
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The story of the freshness may make you wonder if there are other basic flavors that humans have not yet noticed. Some researchers believe that we may still have a basic sense of taste: greasiness. Some substances on the human tongue are perfectly suited to act as fat receptors, and the body apparently responds strongly to the presence of fat flavors in food.
However, when the fat content is high enough that we can taste it consciously, we tend to dislike the taste. So the question becomes, if we can’t actually taste a certain flavor, can it still be considered a basic flavor in itself? How much does taste play a role when we want to eat or not to eat something? To what extent does the human body, unbeknownst to us, control the food that goes down the human esophagus?
Japanese scientists have also introduced the concept of “kokumi” to the world, which further adds to the mystery of taste. The website of the Umami Information Center (UIC), a Japanese organization that promotes flavor research, states, “A kokumi is a flavor that cannot be expressed in terms of the five basic flavors, but contains marginal flavors of the five basic flavors, such as thick, intense (or full-bodied), persistent, and harmonious,” and is produced by three interrelated amino acids. It increases the pleasantness of certain foods, most of which are savory.
At the 2008 Umami Summit in Los Angeles, sponsored by the UIC, food writer Harold McGee had the opportunity to taste some of the ketchup and cheese-flavored potato chip preparations that produce the thicker flavors. His words stirred the imagination of all those curious about the new flavors:
“The flavors seemed amplified but balanced, like the volume was turned up but the equalizer was turned on at the same time. They seem to stick to my mouth in some way, a palpable sensation, but they last longer.”
