In 1907, while enjoying a bowl of soup made with dashi broth and kombu seaweed, Japanese chemist Kikunae Ikeda had an insight that would change the culinary world. He noticed a taste that was not sweet, salty, sour, or bitter. Ikeda named this hard-to-describe savory flavor – umami – and went on to identify the specific amino acid that caused it.
Scientists in Europe and the US remained skeptical about whether umami really was a taste, until a receptor for it was discovered on the tongue almost a century later, in 2000. Today it is taken for granted by most scientists and chefs, but interest is now growing in a different flavor that was first discovered in Japan.
The newer flavor, kokumi, is even harder to describe than umami, but understanding how and why we enjoy food is potentially just as important. In Japanese, the term is koku describes foods with the kind of mouthful “thickness” often caused by fats – what English speakers might describe as rich. “It feels like a physical thrill,” says culinary scientist Joshua Evans. It works “by covering the mouth and getting more intense and lengthening over time.” When asked what food koku has, Japanese food experts mention wild boars, adult wasps, duck eggs and aged sake, as well as long-braised and fermented dishes.
Koku reflects a sensory experience most closely related to touch, influenced by aromas and textures. Add the Japanese suffix -me, meaning taste, emphasizes the specific taste detected by the tongue. The precise nature of kokumi remains the subject of great debate among sensory scientists and chefs, in part because it cannot be detected in the mouth by itself; rather it modifies other tastes and tastes.
The earliest kokumi research focused on the contribution of garlic to foods. In 1990, Japanese scientist Yoichi Ueda found that if he added diluted garlic to two types of soups, people who ate them would describe having more sensations associated with kokumi. Later research isolated amino acids in the garlic that appeared to cause the effect, including glutathione.