Katsuobushi smoking and drying equipment

What it is

Katsuobushi is made in a chain of stages rather than in one box. Bonito is cooked, then smoked and dried repeatedly until it becomes a hard block, which is the product called arabushi. For the mould-treated grades, the block is inoculated with mould and dried again in cycles.

The equipment therefore has separate parts for cooking, for repeated smoking and drying, and, for some products, a controlled maturation stage. The brief describes a process chain, not a single appliance, and it rates the design as a high-complexity research case rather than a first build.

How the stages work

Smoking uses hardwood, and the sources name oak as typical. The fish must be moved within the smoking chamber so that it dries evenly. MAFF distinguishes smoked arabushi from the mould-treated karebushi and honkarebushi, so the design depends on which grade is made.

Grades are set by the number of mould cycles. According to one source, two cycles make karebushi and three or more make honkarebushi, and honkarebushi takes more than six months in total. The mould is named as Aspergillus glaucus or Eurotium herbariorum. Smoked bonito is not automatically mould-matured, and the page does not encourage growing unidentified mould.

Open questions

Which named product uses which stages, which cultures are authorised, and what histamine and smoke-contaminant controls apply are not settled in the consulted sources. The brief lists complete specialist validation as a requirement before any build is published as a method.