The Science of Satisfaction
A Japanese gourmand discovers the fifth element of taste.
The question seemed simple enough: what does this soup taste like? Kikunae Ikeda, a Japanese chemist, asked himself this question while eating one of his favorite dishes, a broth called dashi. He considered each of the four basic components of taste in turn—sweet, bitter, salty, sour. But to his surprise none of them quite fit. He could taste something more in dashi, something beyond the usual quartet. But what? This small, nagging question would soon revolutionize the scientific understanding of taste—and transform the palates of human beings around the globe.
Ikeda came from a refined family—part of an ancient samurai clan—that had fallen on hard times in the late 1800s. He had to sell his bed to scratch together enough money for college, and he taught classes on Shakespeare, in English, for spare cash. He was also a bit of a gourmand, and as he advanced in his science courses, he became tantalized by the chemistry of taste, especially that unsalty, unsour, unsweet, unbitter quality he sensed in dashi.
Dashi’s main ingredient is a variety of kelp called kombu; when Ikeda became a professor of chemistry at Tokyo University, he decided to break kombu down to its compounds and isolate the dashi taste. He started in 1907 by boiling down 90 pounds of kelp into a tarry resin. He then stripped out various salts and organic compounds over the next few months until he’d harvested a single ounce of brown crystals. They looked like grains of sand, but as soon as he sampled one—pow! That ineffable dashi flavor exploded in his mouth. Analysis revealed the crystals to be glutamate (glutamic acid), and Ikeda called this new taste umami, Japanese for “scrumptiousness.”
Over the next decade Ikeda continued to explore different aspects of umami. First he searched for glutamate in foods besides kelp. Sure enough, he found high concentrations in meat and fish; cheeses, especially parmesan cheese; and even breast milk. (He also found it in certain plants, such as tomatoes and asparagus.) This discovery made sense: adding even small amounts of these foods to dishes makes them taste more satisfying and filling.
This work led Ikeda to wonder why we taste umami in the first place. All the other basic tastes alert us to something good or bad in food. In general, sweetness means carbohydrate energy; saltiness means mineral nutrition; sourness means acids, which are common in fermented or rotting food; and bitterness means alkaline compounds, which are common in poisonous plants. So what did umami signal? Proteins. Glutamate is an amino acid, one of the building blocks of proteins. So by developing a taste for umami, human beings could detect this scarce resource. In fact, we can taste glutamate at concentrations 6 and 16 times lower, respectively, than sugar or salt, indicating just how important finding protein was to our ancestors. (Oddly, most of the other amino acids taste either sweet or bitter to us, making glutamate the best choice as a protein proxy.) Scientists in the early 2000s finally put Ikeda’s insight onto firm footing by locating specialized glutamate receptors on the human tongue.
Ikeda set out to commercialize his discovery. Most Japanese people at the time scratched out a hard living as farmers, and their meals consisted largely of just rice and vegetables. Ikeda thought that creating a seasoning based on glutamate would make their food taste more satisfying.
For some reason Ikeda decided not to use kelp; instead he used wheat to mass-produce glutamate. It was messy, labor-intensive work, but by March 1909, just two years after starting his research, Ikeda had isolated crystals of 85% purity. Workers then smashed them with hammers, sprinkled in some salt, and packaged the powder for sale. Ikeda named the seasoning Ajinomoto, Japanese for “at the origin of flavor.”
Today we know Ajinomoto by a different name, monosodium glutamate, or MSG. It’s one of the most popular seasonings in the world: human beings consume five billion pounds per year around the globe, nearly a pound per person. (Most MSG is produced nowadays using bacterial fermentation.) And no wonder it’s so popular. As Ikeda sensed, umami satisfies a hunger deep within us. Many schoolchildren even today learn that there are only four distinct tastes. But pass them a piece of cheese or a cup of soup, and their tongues will tell them differently.