Katsuobushi is the Japanese name for fermented, smoked and dried skipjack tuna (katsuwonus pelamis). Whereas, bonito (sarda orientalis) has a similar color and texture and is sometimes used as a cheaper substitute, although all our katsuobushi are authentically produced in a traditional manner using only skipjack tuna.

The distinct umami flavor in katsuobushi comes from its high inosinic acid content which has also been shown to impart a deep “kokumi” flavour.

Skipjack tuna are first filleted and the belly trimmed away. The fatty belly flesh is not suitable for use in the production of katsuobushi. The fillets are then simmered for an hour to an hour and a half, depending on size. Then the rib bones, which are left on the fillets to stop them from breaking apart during the cooking process, are removed.

The fillets are then put through a near month long process of smoking and resting. Smoked over oak for 5 to 6 hours at a time, then left to rest for a day to allow the condensation to cover the surface, then smoked and rested again the following day. This process is repeated 15 or 16 times over the month.

At this stage the fillets are called “ara” katsuobushi” and are commonly used for sliced “kezuri” katsuobushi, however they are not true katsuobushi without the final fermentation stage.

The fillets are coated with aspergillus glaucus culture and left for 2 weeks in a closed cultivation room. They are then laid out to dry in the sun for a further 2 weeks. The resulting mold is then scraped off and the process is repeated for a minimum of 2 months to produce “kare” katsuobushi and for over two years to produce “hon-kare” katsuobushi.

The mold slowly ferments the fillets and draws out any residual moisture. When the process is complete the aged fillets are hard, dry and less than 20% of the original weight.

All of our kare and hon-kare katsuobushi are sold whole. We can also supply the ara katsuobushi and ara magurobushi in sliced forms.

Magurobushi is made from albacore tuna, (a type of “yellow fin” tuna or in Japanese “kampachi maguro”) followinging the same process as katsuobushi but without the final molding and aging process.

Magurobushi is traditionally used for Japanese clear soups because of its delicate soft taste and light colour whilst Katsuobushi has a stronger flavor and darker colour and is used in miso soups and has a multitude of other applications in Japanese cuisine.

We also stock high quality authentic Japanese katsuobushi graters called “kezuri-ki”.

Please view the items in our Cook Tokyo Shop for a more detailed explanation of each individual product.