Natto (Japanese Fermented Soybeans)
This recipe guides you through making homemade natto by carefully soaking, cooking, and inoculating soybeans with a specialized starter. The process involves precise temperature and humidity control during an extended fermentation period, resulting in the distinctive sticky, pungent Japanese fermented soybeans.
Equipment
- 1 Large Pot For soaking and cooking soybeans
- 1 Pressure Cooker Optional, for faster cooking; a regular pot can also be used for longer cooking
- 1 Colander For draining cooked soybeans
- 1 Food Thermometer Essential for monitoring fermentation temperature
- 1 Fermentation Container Shallow, sterile, with a lid or cover that allows some air exchange
Ingredients
Main
- 2 cups dried soybeans 10 1/2 ounces; 300g
- Half of 1/8 teaspoon natto starter spores such as Nattomoto
Instructions
- Soak dried soybeans in water for 12-18 hours until fully rehydrated and plump.
- Drain the soaked soybeans and cook them in a pressure cooker for 30-45 minutes or in a large pot for 3-4 hours until exceptionally tender.
- Drain the cooked soybeans thoroughly and let them cool to around 104-115°F (40-46°C).
- While cooling, sterilize all fermentation equipment (container, spoon) by boiling or using a sterilizing solution.
- Dissolve the natto starter spores in 1-2 tablespoons of sterile water.
- Pour the dissolved starter over the still-warm soybeans, mixing gently but thoroughly to ensure even distribution.
- Transfer the inoculated soybeans to a shallow, sterile fermentation container, ensuring they form a thin, even layer. Cover loosely to allow air exchange.
- Ferment the soybeans in an incubator or warm spot at a consistent temperature of 100-104°F (38-40°C) for 20-24 hours.
- After fermentation, remove from the incubator and let cool at room temperature for 2-3 hours.
- Refrigerate the natto for at least 12-24 hours to allow the characteristic stickiness and flavor to fully develop before serving.
Notes
Achieving successful natto hinges on meticulous sanitation to prevent unwanted bacterial growth; all equipment must be sterilized. Proper soybean cooking to a very tender, almost mushy, consistency is crucial for the ideal sticky texture. Temperature control during fermentation (around 100-104°F / 38-40°C) is paramount for Bacillus subtilis natto to thrive. Ensure adequate humidity in the fermentation environment without condensation dripping onto the beans. After fermentation, a brief cooling period at room temperature followed by refrigeration for 12-24 hours allows the flavors and stickiness to develop fully.