Katsuobushi (鰹節 or かつおぶし?) (Chinese: 柴魚; chai2 yu2; lit. "firewood fish"), is the Japanese name for a preparation of dried, fermented, and smoked skipjack tuna (Katsuwonus pelamis, sometimes referred to as bonito). Katsuobushi and kombu (a type of kelp) are the main ingredients of dashi, a broth that forms the basis of many soups (such as miso soup) and sauces (e.g., soba no tsukejiru) in Japanese cuisine. It is today typically found in bags of small pink-brown shavings, looking somewhat like cedar shavings used to line the cages of pet animals, or the shavings of a plain wooden pencil. Larger, thicker shavings, called kezurikatsuo (削り鰹; けずりかつお), are used to make the ubiquitous dashi stock. Smaller, thinner shavings, called hanakatsuo (花鰹; はなかつお), are used as a flavoring and topping for many Japanese dishes, such as okonomiyaki. Traditionally, large chunks of katsuobushi were kept at hand and shaved when needed with an instrument called a katsuobushi kezuriki, similar to a wood plane, but in the desire for convenience this form of preparation has nearly disappeared. Katsuobushi, however, retains its status as one of the primary ingredients in Japanese cooking today.
Katsuobushi's umami flavor comes from its high inosinic acid content. Traditionally made katsuobushi, known as karebushi, is deliberately planted with fungus (Aspergillus glaucus) in order to reduce moisture.
When hanakatsuo is added as a topping to a hot dish, the heat has the effect of making the flakes move as if dancing; because of this, katsuobushi topping is also known as dancing fish flakes.
Other than the main ingredient of dashi stock, other popular uses of katsuobushi include:
- As a stuffing for rice balls (onigiri).
- As a seasoning for cold tofu (hiyayakko, 冷奴) along with grated ginger and Welsh onion (a type of spring onion.)
- As a topping for rice (called furikake).
- Sprinkled with sesame seeds and chopped nori atop cold soba noodles (zarusoba).
- As a topping on takoyaki and okonomiyaki.
- As a seasoning on century egg along with sesame oil and soy sauce.
- As a high-protein treat for cats sold at pet stores.
- Video of dancing fish flakes
- an interesting description of katsuobushi seen in the Tsukiji fish market