In 1907, while enjoying a bowl of soup made with dashi broth and kombu seaweed, the Japanese chemist Kikunae Ikeda had a perspective that would change the culinary world. He noticed a taste that was not sweet, salty, sour or bitter. Ikeda gave this salty taste an indescribable name – umami – and went on to identify the specific amino acid that triggered it.
Scientists in Europe and the United States have remained skeptical that umami was truly a taste until a receptor for it was discovered on the tongue nearly a century later, in 2000. Today, it is considered to be in agreement. by most scientists and chefs, but interest is now growing in another taste first detected in Japan.
The newer taste, kokumi, is even harder to describe than umami, but it is potentially just as important to understanding how and why we enjoy food. In Japanese, the term koku describes foods that have a kind of “thickness” full of mouth, often imparted by fats – what English speakers might describe as rich. “It feels like a physical sensation,” says culinary scientist Joshua Evans. It works “covering the mouth and becoming more intense and extended over time.” When asked what foods koku has, Japanese food experts list wild boars, adult wasps, duck eggs and aged sake, as well as long-cooked and fermented dishes.
Koku reflects a sensory experience most closely allied to touch, influenced by flavors and textures. Adding the Japanese suffix -me, ie taste, highlights the specific taste detected by the tongue. The precise nature of kokumi remains the subject of much debate among sensory scientists and cooks, in part because it cannot be detected on the palace by itself; rather, it modifies other tastes and flavors.
The earliest studies of kokumi focused on the contribution of garlic to food. In 1990, Japanese scientist Yoichi Ueda discovered that if he added diluted garlic to two types of soups, the people who ate them would describe that they had more sensations associated with kokumi. Subsequent research isolated amino acids from garlic that appeared to cause the effect, including glutathione.