Katsuo Bushi (Bonito Flakes) 柴鱼片
Also Known as Skipjack Tuna, It’s hard to imagine that a fish could dry out in the ocean. Ocean-dwelling fish, such as salmon, have special small molecules in their flesh that keep water flowing into the fish just as quickly as the salty environment draws water out. If that balance tips, the fish can indeed dry out.
From the perspective of a fish, dehydration is death. From the perspective of a chef, however, dehydration is delicious. That’s because removing water concentrates the molecules that maintain osmotic equilibrium—and many of them have the savory taste of umami.
Japanese katsuobushi takes this concept to the extreme. For at least six hours a day, for up to two weeks, bonito fillets are smoked over oak. Then the fillets are fermented by mold while drying in the sun for months (even years). They wind up looking like a twisted, charred piece of wood. Shavings of katsuobushi are used to infuse traditional dashi with the taste of umami.