How to Make Black soybeans
Fermented black soybeans are a probiotic-rich preparation of black soybeans through lacto-fermentation. They offer earthy, tangy flavors distinct from Chinese fermented black beans.
Category: Legumes & Soy · Method: Fungal/Mold · Time: 1-6mo · Difficulty: 3/5 · Yield: varies · Temp: 18-22°C
History
Black soybeans have been prized in East Asia for millennia. While douchi (fermented with mold) is traditional, lacto-fermentation offers a different flavor profile with probiotic benefits.
Ingredients
- 2 cups Dried black soybeans — Soaked 12-24 hours and rinsed
- 25-30g Sea salt — Calculated at 2.5-3% of total weight of beans + water
- 1 quart Filtered water — Chlorine-free is essential
- 1/4 cup Starter culture — Raw whey, sauerkraut juice, or liquid from a previous ferment to ensure rapid acidification
Equipment
- Glass jar
- Weight
- Cloth cover
- Pot
Instructions
Soak and Prep
Soak black soybeans for 12-24 hours in plenty of water. Drain and rinse thoroughly to remove anti-nutrients and debris.
Time: 12-24 hours
Tip: Change the soaking water once or twice if possible.
Cook until Tender
Boil the beans in fresh water until they are tender but not falling apart. This typically takes 60-90 minutes depending on the age of the beans.
Time: 1-1.5 hours
Tip: Skim off any foam that rises to the surface during boiling.
Cool to Room Temperature
Drain the cooked beans and allow them to cool completely to below 30°C (86°F). Adding hot beans to the brine will kill the probiotic bacteria and starter culture.
Time: 45 min
Tip: Spread them on a baking sheet to speed up the cooling process.
Brine and Inoculate
Dissolve the salt in the water. Place the cooled beans in a clean jar, add the starter culture (whey or veggie juice), and pour the brine over the beans until submerged by at least 1 inch.
Time: 10 min
Tip: Using a starter culture is a critical safety step for cooked legumes to jumpstart the pH drop.
Primary Fermentation
Weight the beans down to keep them submerged. Seal with an airlock. Ferment at 18-22°C until the brine is cloudy and the beans have a pleasant, tangy aroma. Check pH after 7 days; it must be below 4.6 for safety.
Time: 2-4 weeks
Tip: The brine will turn a deep, beautiful purple-black color.
Fermentation Timeline
- Day 1-3: Start — Fermentation initiates.
- Day 4-10: Active — Deep tang develops.
- Day 11-14: Ready — Earthy, sour black beans.
Signs of Success & Spoilage
Good signs
- Dark purple brine
- Tangy aroma
- Firm beans
- Active bubbles
Warning signs
- Mold
- Ammonia smell
- Mushy beans
- Off colors
Troubleshooting
- Too firm
- Cause: Under-cooked before ferment Solution: Cook beans longer before brining; the fermentation process will not significantly soften the beans further.
- Ropy or viscous brine
- Cause: Pediococcus or other slime-producing bacteria Solution: Usually harmless but unappetizing. Ensure higher salt concentration and cooler temperatures next time. If the smell is pleasant, it is often safe, but discard if it smells putrid.
- White film on surface
- Cause: Kahm yeast due to oxygen exposure Solution: Scrape off immediately. Ensure the weight is keeping all solids submerged and check the seal on your airlock.
- pH remains above 4.6
- Cause: Insufficient starter culture or low temperature Solution: If the pH does not drop below 4.6 within the first 5-7 days, discard the batch to avoid the risk of pathogens like C. botulinum.
Storage
Refrigerate Keeps 4-6 months. The flavor continues to mellow and develop in the fridge. Always use a clean utensil to scoop beans out.
Health Benefits
- Anthocyanins
- Protein
- Probiotics
- Fiber
- Iron
Serving Suggestions
- Stir-fry addition
- Rice topping
- Salad ingredient
- Taco filling
- Buddha bowls
Related Legumes & Soy Ferments
Other Fungal/Mold Ferments
- Miso — Condiment
- Douchi (black beans) — Legumes & Soy
- Furu (tofu cubes) — Legumes & Soy
- Tempeh gembus — Legumes & Soy
- Stinky tofu — Legumes & Soy
- Blue cheese — Dairy
- Brie — Dairy
- Camembert — Dairy