[From January Issue 2013]
Katsuobushi, also called dried bonito, is a smoked fermented fillet of skipjack tuna. An essential ingredient in Japanese cuisine, shaved dried katsuobushi is one of the main ingredients in dashi, a broth that forms the base of many soups, including miso.
First the head of the fish is removed and the flesh is deboned. The fatty belly area is also removed. The fillets are then put in a basket and simmered for an hour to an hour and a half. Bones from the ribs are then removed and the fish is smoked. This action is repeated many times and the process can take up to a month.
The last step of the process is to cover the fillets with mold and let them dry. The fermentation stage in the process is essential for breaking down the long molecules of the natural fat in the bonito into shorter ones, and this creates the so-called umami flavor. Artisan katsuobushi makers repeat the fermentation stage multiple times until all of the fat has been converted. A katsuoboshi master knows when this has occurred from the softness of the surface of the whole katsuobushi, as well as from the sound it makes when struck.
A katsuobushi block has the appearance of very hard, dry wood and is less than 20% of its original weight, containing only 18 ~ 20% water. Production takes from three to six months. In spite of its external dull brown color, once broken, the katsuobushi block is a beautiful ruby red inside. When sold in thin shavings it has a soft color somewhere between pink and light brown.
Katsuobushi is mostly found shaved into very thin pieces and is mainly used for making dashi stock. However it does come in other shapes and sizes: thicker shavings with a richer flavor can be used for salad or as a substitute for smoked ham in a variety of different dishes. You can also buy whole katsuobushi blocks and shave it yourself for a fresher taste. Thin katsuobushi shavings are often used as a topping for dishes such as okonomiyaki or cold tofu. When used on hot dishes it is also called “dancing fish flakes,” because the flakes move in the steam.
Before shaved katsuobushi was sold in strong plastic bags, every household had a special bowl for katsuobushi and it was often the job of the children in the house to shave the katsuobushi before meals. Elderly people associate the sound of katsuobushi being shaved with pleasant childhood memories.
The katsuo fish itself has been consumed in Japan ever since the Jomon period (12,000 ~ 4,000 years ago) but dried bonito was not consumed until later and its appearance and taste have evolved over the years to become the product you can find in stores nowadays.
Katsuobushi is very low in calories but contains lots of protein, thus making it very good for the health. It is considered to be a diet food and useful for fighting stress. Interestingly, outside of Japan it is also widely sold as a gourmet treat for cats.
Text: Nicolas SOERGEL