Japan (Makurazaki Kagoshima, Yaizu Shizuoka, and Tosa Kochi as primary production regions; technique developed from 17th century)
Katsuobushi (鰹節) — dried fermented bonito — exists on a quality spectrum defined by the number of mould cultivation cycles it has undergone. Arabushi (荒節) is the basic form: the bonito has been filleted, steamed, smoked, and sun-dried but has received no mould cultivation. It has a direct, robust, slightly smoky flavour and is the standard grade used in commercial dashi production and household dashi bags. Karebushi (枯節) has undergone at least one mould cultivation cycle: Aspergillus glaucus is applied to the surface of the dried fish, which grows across the block over 2–3 weeks, drawing out residual moisture and enzymatically breaking down proteins into amino acids. After the mould is brushed off, the process is repeated. Honkarebushi (本枯節, 'truly dried node') has undergone three or more mould cycles and has been aged for 6 months to 2 years. The result is an extraordinarily hard, dense block — like wood or stone — with a complex, deeply layered flavour profile. When shaved, honkarebushi produces translucent flakes with a refined, complex aroma and the highest inosinic acid concentration, producing the most nuanced and prized ichiban dashi.
Arabushi: smoky, direct, robust; honkarebushi: complex, layered, refined, deeply marine with no harsh smoke; the finest produces exceptionally clear nuanced dashi
{"Arabushi: no mould cycles; smoky, direct, robust — standard commercial grade","Karebushi: one mould cycle; improved depth and reduced moisture compared to arabushi","Honkarebushi: three+ mould cycles, 6–24 months aging — the premium grade; complex, layered","Mould cultivation function: removes moisture, converts proteins to amino acids, increases inosinic acid","Shaving freshness: honkarebushi shaved immediately before use produces finest dashi; pre-shaved degrades quickly"}
{"The mould-covered surface of honkarebushi (before brushing) is called 'soto-shiro' — white outside; it is normal and desirable","Invest in a quality kezuriki (katsuobushi shaving box) for home shaving — the flake freshness is transformative","Nibansen (second dashi) from honkarebushi still produces excellent stock; nothing is wasted","Regional katsuobushi: Makurazaki (Kagoshima) and Yaizu (Shizuoka) are the two primary production regions with distinct character"}
{"Using pre-shaved arabushi for ichiban dashi — insufficient depth; use honkarebushi freshly shaved","Boiling with katsuobushi — at above 90°C, inosinic acid compounds degrade; steep gently below boiling","Over-steeping — 30 seconds to 2 minutes maximum for ichiban dashi; longer extracts bitter compounds","Not storing blocks correctly — honkarebushi blocks should be wrapped airtight; moisture destroys the aging"}
Tsuji Shizuo, Japanese Cooking: A Simple Art