Bonito or skipjack tuna (Katsuwonus pelamis), a medium-sized fish in the tuna family, is a fundamental to Japanese gastronomy, and is known in Japanese as katsuo.
The lean fillets of this fish are used to make a number of dried and smoked products that are collectively called katsuobushi, and which impart umami flavor to various dishes.
Thin shavings of katsuobushi are used as a condiment or as one of the base ingredients for the broth known as dashi.
One of the origins of Japanse bonito soup stock (dashi) is shio-katsuo (Bonito preserved in salt: also on Ark of Taste), which is salted but un-smoked bonito. Its history spans over 1300 years.
Katsuobushi has been made for about 350 years. It is different from shio-katsuo production method, and is produced through a lot of time and various processes.
Different types of katsuobushi are distinguished based on how they are processed: The most basic and widespread type, arabushi, is smoked and dried, while karebushi is smoked, dried, and fermented several times with Aspergillus glaucus mold, which grows on the surface of the fillets, preventing the growth of unwanted microorganisms, drawing out any remaining moisture, preventing oxidation, and sealing in the umami flavor. This fermentation technique was introduced during the Edo Period. The very finest karebushi, fermented more than 3 times, is known as honkarebushi, and is produced in just a few places in Japan.
Tagobushi is a particular kind of honkarebushi from Tago, a village in the town of Nishiizu on the Izu peninsula in Japan’s Shizuoka Prefecture. The process for making tagobushi involves more than 30 steps and takes about 6 months: First, each fish is gutted, the head is removed, and the lean portion of the fillet is separated from the fatty belly before being simmered in water. After simmering, the bones and skin are removed, and the fillets are smoked over an open flame at a temperature of about 130°C. This firing technique, known as tebiyama, originated in Tago about three centuries ago and is the distinguishing feature of tagobushi (other kinds of katsuobushi are typically smoked at a temperature of about 80°C); it helps to seal as much flavor as possible inside the fillet and extends the product’s shelf life. Following this initial smoking, the fillets are smoked another 10 times or so to enhance flavor and remove moisture.
The smoking fires are fueled exclusively with locally harvested oak and cherry logs. Following smoking, the fillets are sprayed with mold and fermented for 20-30 days, before being scraped (so that the mold does not penetrate too far into the fillet) and dried in the sun for a day.
This process is then repeated another five times (most other honkarebushi is fermented a total of three or four times). By the end of the 6-month production process, the fillets are less than one sixth their original weight and have the appearance and texture of dried wood.
All of the byproducts that result from tagobushi production are also used: The organs and belly of the fish are salted and eaten; the wood ash from the smoking fires is used as fertilizer or to make lye (which is important in the traditional production of konnyaku); and the bones may be used as fertilizer or, along with the heads and other trimmings, to make a concentrated liquid condiment known as katsuo irori (also an Ark of Taste product).
During the Edo Period (1603-1868), the Izu peninsula was one of three leading regions for the production of dried bonito products, and Tago had an important fleet of bonito fishing boats. Until the mid-20th century, there were a few dozen shops in Nishiizu that sold dried bonito products, but today the local artisanal fishing and processing industry has declined, and Izu tagobushi is an extremely rare product, due in large part to the laborious, time-consuming manual processes involved. The remaining producers source frozen whole bonito from the nearby city of Yaizu, and sell their tagobushi almost exclusively within Japan. Production takes place year round, though demand is highest between October and January. Given its long history, strong link with the local territory, the sustainable use of byproducts and unique reliance on the tebiyama method, and its incredible flavor profile, Izu tagobushi must be protected and promoted.