Soy Beans Recipe

Soak soybeans

Rinse 4 cups dry soybeans under cold water and remove debris. Place beans in a large bowl and cover with at least 3–4 times their volume of cold water. Soak for 12–18 hours at room temperature until beans have swollen and are soft to the bite.

Cook soybeans

Drain soaked soybeans and transfer to a large pot. Add fresh water to cover by 2–3 inches (about 2–3 liters). Bring to a boil, then reduce heat and simmer 1.5–2 hours until beans are easily mashed between fingers. Alternatively, pressure-cook for 30–45 minutes. Drain, reserving cooking liquid if desired for flavor; cool the beans to about 35–40°C (95–104°F).

Prepare wheat

If using whole wheat berries, toast lightly in a skillet until aromatic and slightly browned, then cool and crush coarsely. If using flour, skip to next step. Combine 2 cups crushed toasted wheat with the warm, cooked soybeans and mix thoroughly to create a moist but not wet mash.

Inoculate with koji starter

Ensure the soybean-wheat mash is around 30–35°C (86–95°F). Sprinkle 1 tsp koji starter evenly over the mash and mix well to distribute. Spread the inoculated mash in a shallow, clean tray to a depth of 2–3 cm to allow air flow. Cover with a breathable cloth.

Ferment koji

Maintain the tray at 30–35°C (86–95°F) with high humidity for 48 hours. Turn or mix the mash gently every 12 hours to ensure even mold growth. Within 48 hours you should see white, fluffy koji (Aspergillus mycelium) colonizing the mash and a sweet, nutty aroma. If black or green mold appears, discard and start over.

Make the brine

Dissolve 600 g non-iodized salt in about 3–3.5 liters of water to make a saturated brine. Adjust total brine volume so that when combined with koji mash it will allow the mixture to be submerged in a fermentation vessel with headspace. Cool brine to room temperature.

Combine koji and brine

Transfer the fully colonized koji mash to a clean, food-safe fermentation vessel (ceramic crock or food-grade plastic). Pour the cooled brine over the koji so the mash is completely submerged or at least mostly submerged. Press down the mixture to remove large air pockets. If using kombu or dried shiitake, tuck them into the moromi now for additional umami.

Primary moromi fermentation

Cover the vessel with a breathable lid (cloth and loose lid) to keep out dust while allowing gases to escape. Store at 20–25°C (68–77°F). For the first month, stir the moromi once every 3–7 days to redistribute microbes and salt. Check for unusual odors or surface contaminants; skim any surface scum if needed.

Extended fermentation

Allow the moromi to mature for 6 months to 12 months (traditional soy sauce fermentation). Over this period the mash will darken, liquefy, and develop deep savory flavors. Stir or gently mix monthly. Longer fermentation (up to 18 months) yields darker, more complex sauce.

Separate liquid

After the desired fermentation time, strain the moromi through a fine mesh, cheesecloth, or a pressing bag to separate solids from the liquid. Press or squeeze firmly to extract as much liquid as possible. This liquid is raw soy sauce.

Clarify and pasteurize (optional but recommended)

To improve shelf life and clarity, gently heat the strained soy sauce to 70–80°C (158–176°F) for 10–15 minutes (do not boil vigorously). This pasteurizes and halts fermentation. Skim any foam, then cool to room temperature.

Adjust and bottle

Taste the sauce. If desired, add up to 1 tbsp mirin or 1 tsp sugar to round flavors. Transfer soy sauce into sterilized bottles or jars, leaving minimal headspace. Seal tightly. Store unopened bottles in a cool, dark place; refrigerated after opening for best quality.