Nukazuke are Japanese pickles made by burying vegetables in a fermenting bed of rice bran, salt and water called a nukadoko. A cucumber buried for half a day comes out crisp, lightly sour, salty and savory. The bed itself is a living ferment: kept and stirred daily, a nukadoko can be maintained for years, and many Japanese families pass theirs down.
How a Nukadoko Works
A nukadoko is made by kneading rice bran with salted water and fermenting it with vegetables (Sugiura et al., 2024). Lactic acid bacteria acidify a new bed within the first week, and Lactobacillus plantarum tends to dominate after a couple of months (Ono et al., 2014). In a study of 16 household beds, most were dominated by lactobacilli; beds started with fresh bran first grew other bacteria before lactobacilli took over, which is why an established bed is more stable (Sakamoto et al., 2011). Yeasts are part of the community and contribute to the aroma, and not stirring lets the upper and lower layers drift apart (Sugiura et al., 2024).
Nutrition: More Vitamin B1, and Plenty of Salt
Japan’s official food composition tables show cucumber pickled in nuka has about 0.26 mg of vitamin B1 (thiamine) per 100 g, against 0.03 mg for raw cucumber – roughly nine times more (MEXT; raw cucumber). The vitamin comes from the rice bran, which is rich in B1, moving into the vegetables; lactic acid bacteria isolated from nukazuke didn’t produce much thiamine themselves (Masuda et al., 2012).
The same tables list 5.3 g of salt per 100 g of nuka-pickled cucumber, so nukazuke is a small side, not a vegetable portion. Shorter pickling and a quick rinse keep it less salty.
Starting a Nukadoko
The full recipe is in the recipe card above. Toasted rice bran is mixed with salted water to the texture of damp sand, flavored with kombu, chili and ginger, and “trained” for about a week by burying vegetable scraps and stirring daily. The bed is ready when it smells pleasantly sour and toasty. Research beds have used a similar proportion – around 11% salt relative to the bran weight (Sugiura et al., 2024).
Daily Care
- Stir once a day (twice in hot weather), turning the bed over from the bottom with clean hands.
- Keep it damp-sand texture: add a spoonful of bran if it gets wet from the vegetables’ water; pour off pooled liquid or soak it up with a clean cloth.
- Top up with fresh bran and a little salt every few weeks as the bed is used up.
- Going away? Put the bed in the fridge; it slows right down and needs stirring only every few days. For longer breaks, sprinkle the surface with extra salt and bran and refrigerate.
What to Pickle, and for How Long
Typical times in a room-temperature bed (much longer if the bed is in the fridge). These are common starting points, not rules – taste and adjust:
| Vegetable | Preparation | Time |
|---|---|---|
| Cucumber | Whole, rubbed with a little salt | About 6–12 hours |
| Carrot | Halved or in sticks | About 1 day |
| Daikon or turnip | Halved or thick slices | About 1–2 days |
| Eggplant | Whole, rubbed with salt | About 1 day |
| Cabbage | Quarter wedge | About 1 day |
To serve, wipe off the bran, rinse briefly and slice. Nukazuke keep only a day or two out of the bed, so pickle little and often.
Troubleshooting
- White film on the surface: usually surface yeast. Mix it into the bed or scoop it off, and stir more often.
- Too sour: add fresh bran and a little salt; some cooks add a little mustard powder.
- Bland pickles: the bed may be too cold or too young; keep stirring daily at room temperature and add kombu for savoriness.
- Fuzzy colored mold, a rotten smell or pink or black spots: scoop out a thick layer; if it’s widespread or the smell stays foul, start a new bed.
Other Japanese pickles and ferments: umeboshi, kasuzuke (sake lees pickles) and shio koji. For a brine-based alternative, try fermented radishes.