What it is

Katsuobushi is skipjack tuna that has been cooked, smoked, dried, and, in traditional forms, repeatedly fermented and dried before shaving. Thin flakes carry smoke, cured-fish aroma, and inosinate. Inosinate works synergistically with the glutamate in kombu, which is why combining the two creates a dashi that tastes fuller than either ingredient alone.

Using the flakes

For first dashi, add flakes to hot kombu stock, steep briefly, and strain without pressing hard if clarity is important. A longer second extraction can reuse the kombu and flakes for simmered dishes where delicacy matters less. Katsuobushi is also effective directly on tofu, rice, greens, and okonomiyaki, where heat makes the thin shavings move and releases their aroma.

Storage and alternatives

Keep opened flakes sealed, dry, and away from heat; refrigeration or freezing helps preserve volatile smoky aromas after opening. Discard them if moisture, mold, or rancid odors develop. Vegetarian dashi can replace fish with dried shiitake, but the flavor changes because mushrooms provide guanylate and earthy aromas rather than cured-fish character.