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Nukanishin is Hokkaido herring coated in salted rice bran and left under a weight to ferment. Traditional batches were salty and fermented for a long time, one long-fermented product for a year, soured by salt-loving lactic bacteria. Most products today are lower in salt and fermented for a short time, so they taste less sour.
Fully documentedFish and seafood10 days – 12 months
Recipe
No fixed amounts recordedThe sources give no fixed amounts; the bran-bed ratio in the steps comes from a Hokkaido research institute trial.
Spring herring, scaled, headed, gutted and tailed, with the red lateral muscle removed
Too little salt shortens the keeping time; too much makes it too salty[maff-nukanisin]
Starter
spontaneous traditionally; a Tetragenococcus halophilus starter in a 2025 trial
Total time across the recorded steps: 10 days – 12 months
Start
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What changes:The herring is cleaned down to the pale flesh and rinsed
Step 1 of 4
Clean the herring
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
T. halophilus
T. muriaticus
Lactic acid bacteria
Scales, head, guts and tail come off, and the red muscle between back and belly is pulled out with chopsticks so the bones do not prick the hands. Output: cleaned herring (semi-dressed), or fillets in the 2025 trial.
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
Nukanishin is Hokkaido herring coated in salted rice bran and left under a weight to ferment. Traditional batches were salty and fermented for a long time, one long-fermented product for a year, soured by salt-loving lactic bacteria. Most products today are lower in salt and fermented for a short time, so they taste less sour. Made in 4 steps over 10 days – 12 months. The longest step, ferment, takes 6 days – 12 months (Takahashi Y. 2025) and runs at 20 °C (Takahashi Y. 2025). Salt is 12 % (Takahashi Y 2025). Tetragenococcus halophilus, a salt-requiring lactic acid bacterium isolated from nukanishin fermented for a year and Tetragenococcus muriaticus, also isolated from long-fermented nukanishin do most of the fermenting.
Nukanishin ferments cleaned herring in salted rice bran. Its sourness comes from salt-loving Tetragenococcus, and low-salt modern versions ferment far less than the old year-long kind.
Low-salt sweet nukanishinA modern, less salty product with a milder taste.
Starter nukanishin filletsFillets fermented 6 days at 20 °C with a T. halophilus starter (research trial).
Safety
Fish bran pickles can carry histamine. In a survey funded by Japan's health ministry, 7 of 12 retail fish bran pickles, a set that included two herring products, held over 400 µg/g histamine, more than the Codex fish-sauce cap of 40 mg per 100 g (400 ppm). One held about 200 µg/g and 4 almost none. The US FDA says that in fish prone to histamine it can build up unless they are properly chilled, so keep the herring cold before salting. Japan's farm ministry (MAFF) warns that too little salt stops the pickle keeping long. Heating does not remove histamine once formed, so grilling will not fix a bad batch.
Hazards the sources name: Histamine-forming bacteria; 7 of 12 retail fish bran pickles held over 400 µg/g histamine (the 12 included two herring products); Some Tetragenococcus halophilus strains from fish bran pickles, which form histamine.
Nukanishin is said to date from the Edo period, when bran pickling let herring survive the long ship voyage from Hokkaido to Hokuriku and Kansai. Otaru's catch collapsed in 1950; fry releases from the late 1990s helped it recover.