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Fermentation Atlas

Fish and seafood from Japan

Katsuobushi (karebushi, honkarebushi)鰹節

Skipjack fillets are simmered, deboned and smoked over hardwood again and again until rock hard, which gives arabushi. For karebushi, the fillets are scraped and covered with Aspergillus mould, sun-dried and brushed clean, about four times over six months. The moulds break down fat and draw out the last water. Made in 6 steps over 6.3 months. The longest step, grow mould, sun-dry and brush off, about four times, takes 6 months (Takenaka S) and runs at 27 °C (Takenaka S). Aspergillus chevalieri and Aspergillus pseudoglaucus, A. amstelodami, A. ruber and A. montevidensis do most of the fermenting.

Key numbers
Main step6 monthsReported[takenaka-ifo][maff]Grow mould, sun-dry and brush off, about four times
Temperature27 °CReported[takenaka-ifo]Grow mould, sun-dry and brush off, about four times
Fully documentedFish and seafood6.3 monthsMore fish and seafoodMore from Japan

Recipe

No fixed amounts recordedTraditional process with no added ingredients except smoke and mould.
Skipjack, headed, gutted and cut into four loin pieces[maff][buma2024]
Hardwood for smoking[eu2015]
Mould starter (Aspergillus glaucus group), sprayed at the start of moulding[buma2024]
Starter: defined mould spray or house mould (Aspergillus glaucus group)

Total time across the recorded steps: 6.3 months

Start
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What changes: The skipjack is headed, gutted and cut into four loins

Step 1 of 6
Head, gut and cut into loins
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Aspergillus

Output: four loin pieces per fish.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

What makes this one different

Katsuobushi is cooked and smoked before it is fermented, and the ferment is a dry surface mould, not a brine. Arabushi stops after smoking; only karebushi and honkarebushi are moulded.

Related ferments

Variants

  • ArabushiSmoked and dried only, not moulded.
  • HonkarebushiMoulded several times; the highest grade.

Safety

Repeated smoking over wood leaves polycyclic aromatic hydrocarbons. Because Japanese data showed lower levels were not achievable with good smoking practice, the EU set katsuobushi limits of 5.0 μg/kg benzo(a)pyrene and 30.0 μg/kg for the sum of four PAHs. Low water activity (0.62 in karebushi) keeps it shelf-stable.

History and sources

Every number is labelled with how it is known. How this atlas is made

Dried bonito appears in the Taiho Code (701) and Engishiki (905). The modern method began in Kii Province in 1674, and Mori Yahei brought it to Makurazaki in 1707.

  1. [maff] Ministry of Agriculture, Forestry and Fisheries (MAFF), にっぽん伝統食図鑑 (Japan traditional foods), かつお節 (Kagoshima)gov
  2. [takenaka-ifo] Takenaka S., かつお節かび付け工程で働く好乾性糸状菌の分類と菌叢解析に関する研究 (classification and flora of xerophilic moulds in katsuobushi moulding), Institute for Fermentation, Osaka research report poster P-2paper
  3. [kadooka2020] Kadooka C., Nakamura E., Kubo S. et al. 2020, Analysis of the fungal population involved in katsuobushi production, Journal of General and Applied Microbiologypaper
  4. [takenaka2020] Takenaka S., Nakabayashi R., Ogawa C. et al. 2020, Characterization of surface Aspergillus community involved in traditional fermentation and ripening of katsuobushi, International Journal of Food Microbiologypaper
  5. [buma2024] Buma S., Urayama S.I., Suo R. et al. 2024, Mycoviruses from Aspergillus fungi involved in fermentation of dried bonito, Virus Researchpaper
  6. [fitri2022] Fitri N., Chan S.X.Y., Che Lah N.H. et al. 2022, A comprehensive review on the processing of dried fish and the associated chemical and nutritional changes, Foods 11(19):2938paper
  7. [eu2015] Commission Regulation (EU) 2015/1125 of 10 July 2015 amending Regulation (EC) No 1881/2006 as regards maximum levels for PAHs in katsuobushi (dried bonito) and certain smoked Baltic herringgov