Nukadoko: How to Make Japanese Fermented Rice Bran Pickles

Nukadoko is a fermented mixture of rice bran, salt, and water used to make nukazuke, or Japanese pickled vegetables. This naturally vegan and gluten-free fermentation method, named after nuka (rice bran) and doko (bed), ferments for one to three weeks, resulting in the growth of beneficial Lactobacillus (lactic acid bacteria).

Once you’ve prepped the pickling bed, you can bury any vegetable in the rice bran mixture to make Japanese pickles. In Japan, popular nukazuke vegetables include carrots, cucumbers, daikon radish, eggplant, turnips, cabbage, burdock root, nagaimo yam, and ginger. The resulting crunchy, probiotic-rich pickles have a uniquely briny, salty, sour, and pungent taste unlike any other variety of pickles.

Here’s how to make your own Japanese-style rice bran fermentation bed at home:

1. 1. Select your ingredients. Three base ingredients make up every nukadoko: nuka (rice bran powder), salt, and purified water. However, home cooks customize nukadoko with a range of aromatics and flavors, such as dried kombu (Japanese seaweed), ginger, dried red chili peppers, dried shiitake mushrooms, shaved fish, garlic, veggie scraps, and more. You can also add beer or breadcrumbs to the nukadoko to speed up the fermentation process.
2. 2. Toast the rice bran. To create the nuka bed, begin by toasting four cups (or two pounds) of rice bran in a large frying pan until it just starts to brown. Allow the toasted nuka to cool to room temperature before adding it to your nukadoko fermentation/storage vessel.
3. 3. Prepare the salt water. Prepare the water and salt by bringing four cups of water to a light boil and stirring in four to five ounces of salt until it completely dissolves. Remove the water from the heat and stir in the breadcrumbs or beer (if using). Allow the water to cool to room temperature.
4. 4. Add the water to the rice bran. Drizzle the water slowly over the rice bran and use clean hands to stir the mixture until it reaches the texture of wet sand. At this point, add the additional aromatics, seasonings, or vegetable scraps of your choice and stir them into the mixture.
5. 5. Dry the nukadoko. Use your hands to pack down and level the nukadoko, eliminating air pockets. Place a lid over the top of the container, keeping it slightly cracked, and place the vessel in a cool, dry place (ideally, around seventy to seventy-five degrees Fahrenheit) out of direct sunlight. Allow the nukadoko bed to rest for about ten to twenty days (adding bread or beer will decrease the overall fermentation time), stirring the bran mixture and packing it down once a day. After day ten, close the lid fully in between mixings.
6. 6. Make the pickles. When the nukadoko bed is ready for pickling, the rice bran paste will emit a slightly funky, fermented, miso-like scent and have a briny, somewhat sour flavor when tasted. To make nukazuke pickles (also known as tsukemono), bury the vegetables of your choice in the rice bran bed, patting down the bran with your hands to eliminate air pockets.
7. 7. Wait for the pickles to mature. The total time required to pickle each vegetable will vary based on the size, cut, and type of veggie; the minimum pickling time is twelve hours, but the average pickling time is between one and two days. Once pickled, remove the vegetables from the nukadoko, brush off the excess rice bran back into the bed, and rinse the Japanese rice bran pickles under cool water before serving.

Keep your active nukadoko in a lidded container in a cool, dry place out of direct sunlight. Here’s how to care for it:

1. 1. Use the right vessel. Potential nukadoko storage vessels include a lidded glass baking dish, plastic tub, stockpot, pickling crock, or other closed vessel.
2. 2. Stir frequently. Stir your nukadoko a minimum of three times a week (or, ideally, every day) for proper maintenance. Stir nukadoko more frequently in the hot summer months, up to a few times a day. Use clean hands or a kitchen spoon to stir the bran gently. After stirring, compress the bran back down to eliminate any air pockets.
3. 3. Make pickles and refresh the bed. The nukadoko will also benefit from burying vegetables in the bran at least twice per week. Occasionally, incorporate more rice bran and salt into the nukadoko as needed, as vegetables will release moisture into the bran during the fermentation process, diluting the mixture.
4. 4. Refrigerate the nukadoko when you leave. If you have to leave your nukadoko for more than a few days (and no one can stir the bran on your behalf), top the nukadoko with a layer of mustard powder followed by a layer of salt and cover it with a clean tea towel. Place the nukadoko in the refrigerator to keep for up to a month. When you’re ready to revive your nukadoko, carefully remove the salt and mustard layers and bury some vegetables in the bran for a week.

Once you get the hang of this simple fermented food, the sky’s the limit when it comes to tasty pickled vegetables. Use these tips to make the most of your nukadoko.

1. 1. Use a nukadoko kit. For an easy entry into the world of nukadoko, pick up a premade nukadoko kit from a Japanese or Asian market, which typically just requires the addition of water to begin the fermentation process.
2. 2. Try wheat bran. If you’re having difficulty finding rice bran in your local supermarket, wheat bran is a suitable alternative. While the flavor will be slightly different from a rice bran nukadoko, the pickling effect will be the same.
3. 3. Be vigilant about maintenance. Once you’ve successfully crafted a nukadoko bed, you must maintain the mixture. If you don’t stir the fermented rice bran bed at least every few days, the nukadoko will spoil.
4. 4. Gift your nukadoko. Much like a sourdough starter, once you have a thriving nukadoko, feel free to give portions of your nukadoko to friends to start their own nukadoko beds. Learn how to make a sourdough starter.