For centuries, humanity lived with the concept of sweet, salty, bitter and sour – but another flavour was hiding on the sidelines, writes Veronique Greenwood.
Kikunae Ikeda had been thinking a lot about soup.
The Japanese chemist had been studying a broth made from seaweed and dried fish flakes, called dashi. Dashi has a very specific flavour – warm, tasty, savoury – and through laborious, lengthy separations in a chemistry lab, Ikeda had been trying to isolate the molecules behind its distinctive taste. He felt sure that there was some connection between a molecule’s shape and the flavour perception it produced in humans.
But as it was just a few years past the turn of the 19th Century, there was not yet a great deal of evidence to support the idea.
Eventually, Ikeda did manage to isolate an important taste molecule from the seaweed in dashi: the amino acid glutamate, a key building block of proteins. In a 1909 paper, the Tokyo Imperial University professor suggested that the savoury sensation triggered by glutamate should be one of the basic tastes that give something flavour, on a par with sweet, sour, bitter, and salt. He called it “umami”, riffing on a Japanese word meaning “delicious”.
But more than a hundred years later, scientists around the world now acknowledge that umami is real, and just as much a basic taste as the others. It’s not just found in seaweed: we get a hit of umami from tomatoes, meat, broths, cheeses, and many other foods. How did this enigmatic yet brash taste, hidden in plain sight for so many years, finally achieve recognition?
Over the decades, scientists began to put together how umami works. Each new insight brought the claim put forth by Ikeda into better focus. For instance, researchers identified two other molecules that could trigger the sensation: inosinate, behind the umami of bonito fish flakes, and guanylate, behind the umami of dried shitake mushrooms.
Looking closer at nerves sending messages from the mouth to the brain when umami was tasted suggested that it and salt were operating via different channels
And interestingly, the effect of having two of these molecules in the same dish is synergistic. You get way more umami from a broth containing both bonito flakes (inosinate) and seaweed (glutamate) than you get from either alone. You get a similar effect from cooking beef (inosinate) with tomatoes (glutamate).
Some people suggested that perhaps umami was just a kind of saltiness. After all, it often occurred in concert with that sensation. But taking away an umami-triggering substance really did dramatically change perception, researchers found. Looking closer at the nerves sending messages from the mouth to the brain suggested that umami and salt were operating via different channels.
The story of umami might make you wonder, are there other basic tastes out there that we just haven’t gotten around to noticing? Some researchers believe we may have a sixth basic taste for fat. There are some good candidates for fat receptors in the tongue, and it is clear that the body responds strongly to fat’s presence in food.
However, by the time fat levels are high enough that we can actually taste them consciously, we tend not to like the flavour very much. So the question becomes, can something be a basic taste if we don’t really taste it, per se? How much of taste is about encouraging or discouraging us to eat something, and how much of it is the body, unbeknownst to us, keeping track of what’s coming down the chute?
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Further deepening the mystery of flavour, Japanese scientists have introduced the idea of kokumi to the wider world. “Kokumi means a taste that cannot be expressed by the five basic tastes, and also includes marginal tastes of the basic tastes, such as thickness, growth (or mouthfullness), continuity, and harmony,” reads the site of the Umami Information Center (UIC), a group for the promotion of umami research. Triggered by a trio of linked amino acids, the kokumi sensation adds to the pleasure of certain kinds of foods, most of them savoury.
Harold McGee, the food writer, had a chance to try some kokumi-inducing preparations of tomato sauce and cheese-flavoured potato chips at the 2008 Umami Summit in San Francisco under the auspices of the UIC. He wrote, in terms that pique the imagination of anyone curious about new taste sensations: