Dried Skipjack Tuna Shavings
Katsuobushi (pronounced KAHT-su-o-BU-shee) is a form of prepared skipjack tuna, and an essential ingredient in Japanese cuisine.
Katsuobushi is extremely rich in inosinic acid, a glutamine-based compound that creates a highly savoury umami flavour. Along with kombu, it is one of the key ingredients in the Japanese stock dashi.
Katsuobushi production is complex and time-consuming, which contributes both to its complex flavour and to its price tag. In general, the process involves trimming the lean portion of the loin, then gently simmering, wood-smoking, and fermenting it with Aspergillus mold. The fermentation stage is often skipped today, but is technically necessary to create ‘true’ katsuobushi.
The fish used to make katsuobushi is traditionally the skipjack tuna, Katsuwonus pelamis. In some cases, a less expensive relative called bonito (Sarda spp.) is used in place of skipjack tuna. Confusingly, skipjack tuna is also sometimes referred to as bonito. This confusion is further compounded by the fact that katsuobushi is often translated into English as ‘bonito flakes,’ despite the fact that katsuobushi made with true bonito is considered to be an inferior product. Because of this linguistic confusion, most English packaging will say ‘bonito’ on it, despite the fact that skipjack is still used most of the time.
Traditionally, katsuobushi was kept as a solid block and shaved off with a specialized tool as needed. Today, most katsuobushi is sold pre-shaved and ready for use.