Umami rich ingredients
(Dried Bonito Flakes)

What is Katsuobushi?

Katsuobushi, the most important ingredient in dashi at Japanese cuisine


Katsuobushi is made of katsuo or bonito, skipjack tuna, a saltwater fish. Bonito is rich in protein. If unprocessed, it has a 25% protein content, and if used to make katsuobushi, its protein content increases to 77%. It is also rich in inosinate, an important umami substance; the umami is multiplied many times over when combined with glutamate.
This is the mechanism behind ichiban dashi (“first soup stock”) in Japanese cuisine.

Katsuobushi is not just about smoking fish; the creation process is a tradition that has been handed down for over nearly 400 years. Making katsuobushi involves drying katsuo, introducing beneficial mold that triggers fermentation, and creating a deeper, richer flavor. The process takes many months, and the end result is a surprisingly hard, richly flavorful food product. The finished katsuobushi is shaved using a box grater.
The resulting flakes are used mainly for making dashi (stock). This method can use other kinds of fish, such as tuna, mackerel, and sardine.

The Making of Katsuobushi

The process of making katsuobushi begins with filleting fresh bonito (skipjack tuna) into three pieces referred to as kame bushi (“turtle block”). The large piece is then further split into two halves—called mebushi (belly) and obushi (back)—that make up the honbushi (“main block”). The blocks are placed in a woven tray in hot water, carefully arranged to ensure uniform flavor in the end product, and simmered for 60 to 90 min in a step known as shajuku, sealing in the inosinate. The skin and bones are then removed. The blocks are called namaribushi at this point. The next step is baikan (“smoke-drying”). The namaribushi undergo prolonged smoking to remove water content and prevent spoilage. After the first round of baikan, the cracks and cavities are repaired using a paste made from the head and nakaochi (tuna scrape), followed by over a dozen more rounds of baikan to remove even more water, kill harmful bacteria and prevent them from taking hold, and block oxidation. The baikan process transforms the namaribushi into arabushi.


Honkarebushi, a higher grade of katsuobushi, is made by putting the arabushi through a process known as kabitsuke (“mold application”). A coating of beneficial mold seals in aroma. The spores draw out the last of the moisture from deep inside the block; they also break down triglycerides, giving clarity to any soup stock eventually made from that honkarebushi. Around 2 weeks later, the block is temporarily removed from its tub, sun-dried, and individually dusted to remove the surface mold. These steps are repeated for around 4 months. It is through this long-drying process that katsuobushi, known as the hardest food in the world, is created.


Katsuobushi and Inosinate

Katsuobushi contains extremely high levels of the umami substance inosinate. In fact, the baikan and kabitsuke processes boost the inosinate level over what is found in fresh bonito. Shaving katsuobushi using the box grater increases the surface area and makes it easier to prepare stock. The paper-thin shavings also allow inosinate, which dissolves easily in water, to be quickly extracted while preventing other, less dissolvable amino acids from releasing their flavor or clouding the stock.


Katsuobushi and Dashi

Katsuobushi is shaved using a box grater before being used to prepare stock. The simple, rich dashi made from unfermented arabushi is also a popular part of Kansai cuisine. The obushi (back) of honkarebushi produces refined stock low in fat, whereas the mebushi (belly) yields a dashi with more richness. Ichiban dashi (first stock) made from a combination of glutamine-rich kelp and inosinate-rich katsuobushi represents a cooking method that makes the most effective use of umami synergy. This is why ichiban dashi is the bedrock of Japanese cuisine. High-end establishments, such as a ryōtei, will also use magurobushi (bluefin tuna) at times instead of katsuobushi, for a dashi with a refined and clean flavor.

  • Wipe the kelp
  • Put the kelp in the pan
  • Soak kelp in water
  • Boil the kelp at a temperature of 60 degrees
  • Take out the kelp
  • Stop the fire and put the bonito
  • Bonito sank down
  • 綿布を通してだしを濾す

Dashi most commonly utilizes a combination of kombu (kelp seaweed) and katsuobushi (dried bonito flakes), but other ingredients used to make dashi are shiitake mushrooms and niboshi (small dried fish). Dashi-making has evolved over a long period of time. Boiling is known to have been used in Japanese cooking since the Jomon period (c. 13,000–300BC), and the stock from shellfish and fish-bones was used to flavor other dishes.

What is Dashi?

Umami Synergy in Ichiban Dashi

Ichiban Dashi

Ichiban dashi (first brewed) is made by adding lots of katsuobushi to kombu dashi when it comes to a boil. Ichiban dashi is then strained using a strainer covered with a thin cloth on top. Although katsuobushi is added to kombu dashi for only a few minutes, the umami taste of ichiban dashi is more pronounced than that of kombu dashi. The fragrance of katsuobushi then increases. Inosinate is a key substance in the umami taste of katsuobushi. Moreover, the umami taste of dashi is greatly enhanced when the glutamate found in kombu meets the inosinate of katsuobushi. Adding katsuobushi to kombu certainly has a wonderful synergic effect.

Ichiban dashi Ichiban dashi Ichiban dashi

Japanese Cuisine with Delicious Umami

By the seventh century, a dashi using kombu and katsuobushi had developed. This was refined further and has become Japan’s most indispensable cooking stock, generally used in two forms – ichiban (primary) dashi and niban (secondary) dashi. Despite its hidden role, dashi could be said to be the heart of Japanese cuisine, not because of the prominence of its own flavor but because of the way it enhances and harmonizes the flavors of other ingredients. The secret of Japanese cuisine is the art of enhancing and harmonizing.

What is Dashi?

A great variety of fresh food ingredients is available in Japan, with its regional diversity, clearly differentiated seasons, and fertile soil. Washoku, Japanese cuisine, has a tradition of cherishing each season. With umami, chefs bring out the flavors of those seasonal ingredients. Keeping to tradition, they devote themselves to innovation. Please enjoy their umami dishes.

Umami in Washoku

What is Umami?

Umami is the fifth taste, joining sweet, sour, salty and bitter. These are unique tastes that cannot be created by mixing other tastes, and are known as the basic, or primary tastes. Umami is a general term used mainly for substances combining the amino acid glutamate, and/or the nucleotides inosinate and guanylate, with minerals such as sodium and potassium.

What is Dashi?

Whether something tastes good or not is a comprehensive yet subjective evaluation determined by elements such as taste, aroma, texture and temperature, besides other factors such as appearance, color and shape, as well as one’s physical condition, surrounding environment, cultural background, and previous experiences. Of these various elements, umami in balance with the other basic tastes (sweet, sour, salty, and bitter) plays an important role in determining the deliciousness of a dish.

What is Dashi? What is Umami