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Fish and seafood from Japan

Konka-iwashiこんかいわし

Konka-iwashi is Ishikawa's sardine pickled first in salt and then in rice bran ("konka"). Headed and gutted sardines are layered in a barrel with a bran bed of salt, miso, soy sauce and chilli, pressed under a lid and weight, and left through the hot, humid summer for about half a year. Lactic fermentation in the bran gives a very salty, savoury fish.

Fully documentedFish and seafood6 months

Recipe

No fixed amounts recordedThe MAFF and Kanazawa city descriptions give the ingredients but no amounts; each maker uses its own proportions.
Sardines, head and guts removed[maff]
Salt, for the first salting and the bran bed[maff]
Rice bran[maff]
Miso, soy sauce and red chilli, mixed into the bran[maff][kanazawa]

Total time across the recorded steps: 6 months

Start
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Close-up: salt moving into a piece

What changes: Salt draws water and blood out of the headed, gutted sardines

Step 1 of 4
Head, gut and salt the sardines
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented

Salting holds back spoilage bacteria, firms the flesh and draws out blood.

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

At a glance

Konka-iwashi is Ishikawa's sardine pickled first in salt and then in rice bran ("konka"). Headed and gutted sardines are layered in a barrel with a bran bed of salt, miso, soy sauce and chilli, pressed under a lid and weight, and left through the hot, humid summer for about half a year. Lactic fermentation in the bran gives a very salty, savoury fish. Made in 4 steps over 6 months. The longest step, ferment through the Hokuriku summer, takes 6 months (MAFF Japan). Salt is 10–15 % (Kuda T 2001). Halophilic lactococci, the main bacteria in Ishikawa fish nukazuke does most of the fermenting.

Key numbers
Main step6 monthsReported[maff][kanazawa]Ferment through the Hokuriku summer
Salt10–15 %Reported[kuda2001]Ferment through the Hokuriku summer

What makes this one different

Konka-iwashi is the sardine form of Hokuriku fish nukazuke. It is ripened for about half a year in a bran bed seasoned with miso, soy sauce and chilli; the Yamagata nuka-iwashi can be eaten from two weeks.

Related ferments

Safety

Salting first holds back spoilage bacteria in the flesh (MAFF). A study of 34 Ishikawa fish nukazuke products from 13 factories measured 10–15 % salt and 0.1 to 1.7 g/100 g lactic acid, and bacteria and acid differed between factories and fish (Kuda et al. 2001). Its abstract reports no pathogen or toxin tests. A later paper says histamine above 1,000 mg/kg occasionally builds up in salted fermented fish, made by halophilic lactococci, and some strains from fish nukazuke form it (Kuda et al. 2012). FDA says histamine cannot be removed by heat or freezing once it has formed, so grilling does not clear it.

Hazards the sources name: Histamine-forming Tetragenococcus halophilus, halophilic lactococci from fish nukazuke, a related salted fish in rice bran: 13 of 200 isolates made over 200 µg/ml histamine in lab broth, and in a challenge test 10 % salted sardine inoculated with one strain reached 2,800 µg/g in 30 days at 20 °C.

History and sources

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

MAFF gives two stories. One credits Noto sake brewers who brought home sake lees that fishermen tried with bran; the other dates it to the Tenpō famine (Tenpō 4–10, the 1830s). It was a winter and lean-season protein and a cash product for fishing villages.

Starter
The sources we found do not say how its fermentation begins.
  1. [maff] MAFF Japan, Nippon dentōshoku zukan (Traditional Foods in Japan), Konka-iwashi (Ishikawa)gov
  2. [kanazawa] Kanazawa City, Kanazawa food culture sheet 15, Konka-iwashigov
  3. [ishikawa-std] Ishikawa Prefecture, Ishikawa furusato food certification standard 2-(2), Gyokairui komenuka-zuke (konka-zuke) (2009, revised 2015)spec
  4. [kuda2001] Kuda T., Miyamoto H., Sakajiri M., Ando K., Yano T. 2001, Microflora of fish nukazuke made in Ishikawa, Japan, Nippon Suisan Gakkaishi 67(2):296-301 (abstract)paper
  5. [kuda2012] Kuda T., Izawa Y., Ishii S., Takahashi H., Torido Y., Kimura B. 2012, Suppressive effect of Tetragenococcus halophilus, isolated from fish-nukazuke, on histamine accumulation in salted and fermented fish, Food Chemistry 130:569–574 (abstract)paper
  6. [fda-ch7] US FDA, Fish and Fishery Products Hazards and Controls Guidance, Chapter 7, Scombrotoxin (histamine) formationgov