katsuobushi Japanese term for a hard fillet of katsuo (bonito) that has undergone an extensive process involving cooking, drying, salting, smoking, and sometimes fermenting. Katsuobushi is the ideal exemplar of an ingredient that has great quantities of inosinate, which interacts synergistically to elicit umami. There are two main types of katsuobushi: arabushi, which is not fermented and has a milder taste, and karebushi, which is fermented and harder. There are also two types of karebushi: On one the red side of the fillet is kept and on the other (chinuki katsuobushi) it is cut off. The second type has a milder, less bitter, and more delicate taste.