Value Village ／ Everyday know-how
This answer is a draft. It stays unpublished until legal review and source verification are complete.
A tub of fermenting rice bran in the kitchen, stirred daily by hand, turning cucumbers and aubergines into pickles overnight — the nukadoko is one of the oldest pieces of Japanese household fermentation still in daily use, and one of the most misunderstood abroad.
| Element | Detail |
|---|---|
| The bed | Rice bran (nuka) + salt (about 13% of the bran weight) + water to a miso-like consistency; kombu, chilli, and a piece of bread or vegetable scraps to start |
| Microbes | Lactic-acid bacteria and yeasts from the bran and air; the bed is ready in 1–2 weeks of daily stirring with "starter" vegetables |
| Daily care | Stir by hand once or twice a day from the bottom — aerates the bed and keeps surface yeasts (which cause off-smells) in check |
| In the fridge | Stir every 2–3 days; fermentation slows; a fridge-kept bed is how most working households manage it |
| Pickling times | Cucumber 4–12 h, aubergine 12–24 h (with a nail or alum for colour), carrot 1–2 days, daikon 1–2 days |
| Salt | Add a little salt and bran as the bed dilutes with vegetable water |
| Signs | White surface film = yeast (stir in or remove); pink, green or black spots = mould (remove with margin, or discard); alcohol smell = over-fermented (add salt, stir, rest) |
[Verify] Salt ratios and times are traditional ranges; food-safety guidance with MHLW's pickle hygiene standards.
A healthy bed smells sour and nutty. Bad smells mean neglect: surface yeast or over-fermentation, fixed by stirring, salt and a day's rest.
At room temperature, yes, in summer even twice. In the fridge, every 2–3 days is enough; for a holiday, cover the surface with a thick layer of salt and refrigerate.
White film is yeast, not mould — stir it in or scrape it off. Coloured mould is a problem: remove generously; if it recurs, start again.
Aubergine, daikon, carrot, celery, turnip, okra, boiled eggs, tofu, cheese, avocado — anything firm. Meat and fish are pickled in a separate small batch and the bran discarded.
The fridge made it urban. Ready-made beds in resealable bags are sold in supermarkets; the daily stir takes 30 seconds and a bed the size of a lunchbox serves a couple.
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https://www.maff.go.jp/j/keikaku/syokubunka/
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/shokuhin/
https://www.mext.go.jp/a_menu/syokuhinseibun/mext_00001.html
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
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