Wasabi
A green Japanese root whose nasal-clearing heat is a short, sharp vapour rather than a lasting burn.
Also: Wasabia japonica, Japanese horseradish, namida wasabi
Wasabi is the grated rhizome of Eutrema japonicum, a plant of cold mountain streams in Japan. Its heat is not capsaicin but allyl isothiocyanate, a volatile that hits the nose and fades in seconds. True wasabi is difficult to grow and expensive, so most wasabi served outside Japan is horseradish, mustard and green dye. Sushi chefs grate it fresh on a rough sharkskin or a metal grater, and the flavour peaks within minutes of grating. It is eaten with raw fish, noodles and rice. The leaves and stems are also eaten, pickled in the Japanese kitchen.