Daitokuji Nattō (大徳寺納豆, Kyoto salt-fermented soybeans)

Ingredients

Equipment Needed

• •Seiro (bamboo steamer), or a lidded steamer insert
• •Kōji-buta (shallow cedar kōji tray), or a shallow food-safe tray with a clean cotton cloth
• •Kitchen thermometer
• •Clean crock or glass jar with a small fermentation weight
• •Bamboo zaru, or a fine mesh drying rack with a protective cover
• •Dehydrator set to low heat, only if the weather is too damp for outdoor drying

Instructions

1. 1

   Soak the beans

   Pick over the soybeans and rinse them until the water runs clear. Soak them in plenty of cool water for 12 to 18 hours, until they have swollen fully and split cleanly when pressed. A dry center will not cook evenly, and kōji cannot do good work in a hard bean.

2. 2

   Cook until tender

   Drain the beans and cook them in a seiro or lidded steamer for 3 to 4 hours, adding water below as needed, until a bean crushes easily between your fingers but the skins mostly hold. Steaming keeps the soybean flavor concentrated and leaves the surface drier than boiling. Wet beans invite trouble later, and this preserve gives you no sauce to hide it.

3. 3

   Cool and inoculate

   Spread the hot beans on a clean tray and cool them to about 35 C. Mix the tanekōji with the roasted flour if your starter needs a carrier, then dust it evenly over the beans and turn them gently with clean hands. If the beans are hotter than 40 C, you weaken the kōji; if they are cold, the bloom starts slowly and the wrong organisms get a head start.

   Do not use sticky nattō as the starter. That is Bacillus subtilis, a different organism and a different food.
4. 4

   Grow the kōji

   Pile the beans 3 to 4 cm deep in a shallow tray, cover with a clean damp cloth, and keep them at 30 to 32 C for 36 to 44 hours. Turn them once after about 18 hours to release heat and give the mold air. They are ready when the beans are webbed with a clean white bloom and smell nutty, sweet, and a little like fresh miso.

   The kōji makes the enzymes that break soybean protein into deep savor. Salt later stops the mold from growing, but those enzymes keep working slowly.
5. 5

   Salt and pack

   Dissolve the sea salt in the boiled and cooled water to make a strong brine. Pack the mame-kōji into a clean crock or glass jar, pour in enough brine to cover it completely, and set a small clean weight on top. No bean should sit above the liquid. The salt is not decoration here; it protects the ferment while the flavor deepens.

6. 6

   Age under brine

   Cover the vessel and keep it at cool room temperature, about 15 to 22 C, for 4 to 6 weeks. Once a week, open it with clean hands and press the beans back below the brine. The liquid will darken and the smell should move toward miso, soy sauce, and roasted nuts. Pink, orange, or fuzzy black growth is not part of the dish; discard the batch if you see it.

7. 7

   Dry in the sun

   Drain the beans well and spread them in a single layer on a bamboo zaru or fine drying rack. Set them in clear sun during dry weather, covered with fine mesh, and bring them inside at night. Turn them once a day. Continue until they are black-brown, wrinkled, glossy, and firm but not brittle, usually 10 to 20 sunny days spread over several weeks. If the weather is damp, use a dehydrator at 35 to 40 C until the same texture appears.

8. 8

   Cure and serve

   Pack the dried beans into a clean jar and cure them in a cool dark place for 4 to 8 more weeks, shaking the jar once a week. Time rounds the salt and brings the miso-like depth forward. Serve two or three beans beside rice, drop a few into ochazuke, or mince one into a dressing for tofu or greens. Use a dry spoon and store the finished nattō refrigerated.

Chef Tips

• •For dried soybeans, shun means current crop. Choose beans that are even in size, pale yellow, and not cracked to dust. Old beans cook unevenly, and no amount of patience will make a hard center hospitable to kōji.
• •The clean white bloom is the first secret. It should smell warm and nutty, never rotten, sharp with ammonia, or dirty. When the foundation smells wrong, be firm and throw it away.
• •A dehydrator is a sensible stand-in when the weather is humid. It does the same drying work at low heat. What it cannot replace is the slow curing afterward, so don't hurry that jar.
• •Eat this as a condiment, not a side dish. Daitokuji nattō is salt-sharp by design, and three beans can season a bowl of rice. That restraint is part of the honmono.

Advance Preparation

• •Plan the work over 12 to 16 weeks: soak on day one, cook and inoculate on day two, grow the kōji for two days, age under brine for 4 to 6 weeks, then dry and cure.
• •Start this in a dry season if you want to follow the old sun-drying method. Damp weather is not romantic; it is simply bad conditions for a salty preserve.
• •Finished Daitokuji nattō keeps for about 6 months refrigerated in a clean jar. White salt crystals are fine. Colored fuzz, a rancid smell, or a slimy surface means it should be discarded.

Frequently Asked Questions

Nutrition Information

1 serving (about 10g)