Katsuobushi: Fermented Fish Flavoring Japan's Favorite Foods
Japanese cuisine is full of fermented ingredients, from soy sauce and miso to pickles and sake. Preserving foods through fermentation is a centuries-old tradition that continues to this day. These fermented foods help to season and bring umami-rich flavors to dishes that otherwise lack those strong flavors.
One of the most essential, but possibly lesser-known, fermented ingredients is katsuobushi. Also known as bonito flakes, you may have seen them dancing on top of a piping hot okonomiyaki or hiyayakko, a cold tofu dish, or seasoned and stuffed inside an onigiri. Katsuobushi is also an unseen helper in the Japanese kitchen, as it lends a greater umami depth to dashi stock where there is no meat to help give it an extra punch. Before katsuobushi can dance on top of warm rice or boost a soup stock, it must first go through a long fermentation journey to become the powerhouse that it is.
Katsuobushi is made from skipjack tuna and starts as simple filets, with the skin and guts removed. The excess fat, which is concentrated around the belly of the fish, doesn’t ferment well and can lead to spoilage so it is also removed. Once the filets are trimmed, they are arranged in baskets and simmered at a temperature just below boiling for anywhere between an hour and an hour and a half. Next, the rib bones are removed from the fish so that they are ready for smoking!
This next part of the process can take an entire month in which time the filets are smoked using oak, pasania, or castanopsis wood for six hours at a time. They are then rested until the next day when they are fired and smoked, which can be repeated 12-15 times. This process gradually removes moisture from the fish until it is hard and resembles a burnt log more than a piece of tuna! Now that the fish has been smoked, the outer layer of tar and fat built up throughout the process must be ground off.
Some of these filets end their journeys here, but they aren’t true katsuobushi! Without the final fermentation, these are known as arabushi, which are often found sold pre-shaved and packaged in stores.
The last fermentation process involves coating the smoked filets in a bacterial culture and rotating them between a cultivation room and the outdoors. The mold growth and sun-drying help draw out extra moisture until the filets are less than 20% of their original weight! Katsuobushi that repeats this process twice is called karebushi; when repeated three or more times it is honkarebushi. These filets look more like a piece of wood than fish, and sound almost metallic when tapped together. When they’re shaved, however, the dull wood-like exterior is contrasted by the deep ruby red of the interior.
Katsuobushi can be easily found in grocery stores throughout Japan with varying thicknesses but can also be purchased as whole filets and shaved at home with special boxes called katsuobushi kezukiri. These boxes have wooden planes built into the top which can be adjusted to shave your katsuobushi to your desired thickness. Thicker shavings are typically used when making dashi, as they lend a deeper, more even flavor, while thinner shavings are generally used as garnishes.
However you use it, katsuobushi is an essential ingredient in Japanese cuisine, from home cooking all the way to high-end cuisine. Its rich, smoky umami flavor can’t be replicated or beat!
About the author:
Kevin Kilcoyne
The spark that lit Kevin Kilcoyne’s interest in Japanese culture began in elementary school through a friendship with his then classmate Keisuke. Since then, that passion has evolved and bloomed to encompass more than just video games and manga, leading Kevin to live in Japan as a participant of the JET program. During his time in Japan, Kevin sought out as many foods as he could, the experiences and taste memories lingering long after they had gone. Now he is forging a path to link his passions for Japanese food, history, and visual culture and is planning for his return to live in Japan once again. For now, you can find Kevin on Instagram (@waruishouten) where he posts his photography and illustration work. Keep an eye out for more posts and updates as Kevin delves more deeply into his passions for writing and food.
