📝 About This Recipe
Embark on a transformative culinary journey by crafting your own traditional Japanese soy sauce from scratch. This deep, reddish-brown nectar is the result of a delicate dance between roasted wheat, protein-rich soybeans, and the magical Aspergillus oryzae mold. The result is a complex, multi-layered condiment that boasts a perfect balance of salt, sweetness, and an incomparable depth of umami that store-bought versions simply cannot replicate.
🥗 Ingredients
The Mash (Moromi) Base
- 1 kg Whole Dried Soybeans (Non-GMO, high-quality organic beans preferred)
- 1 kg Soft Red Winter Wheat (Whole berries for roasting)
- 10 grams Koji-kin (Aspergillus oryzae) (Specifically 'Shoyu-koji' spores)
- 2.5 liters Filtered Water (Chlorine-free is essential for microbial health)
- 450 grams Sea Salt (High-quality mineral salt, non-iodized)
Equipment & Sterilization
- 1 5-liter capacity Food-grade Fermentation Crock (Ceramic or glass preferred)
- 1 piece Wooden Paddle (For aerating the mash)
- 2 meters Cheesecloth or Muslin (Fine mesh for pressing)
- 1 digital Thermometer (To monitor incubation temperature)
👨🍳 Instructions
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1
Rinse the soybeans thoroughly and soak them in three times their volume of water for 12-15 hours until they have doubled in size and are plump.
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2
Steam the soaked soybeans until they are tender enough to be crushed easily between your thumb and pinky finger; this usually takes 4-5 hours in a steamer or 45 minutes in a pressure cooker.
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3
While the beans steam, toast the wheat berries in a dry cast-iron skillet over medium heat, stirring constantly until they are dark golden brown and smell nutty/popcorn-like.
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4
Coarsely crack the toasted wheat berries using a grain mill or a heavy-duty blender; you want a gritty texture, not a fine flour.
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5
Cool the steamed soybeans and cracked wheat to exactly 30°C (86°F). This temperature is critical; too hot and you kill the mold, too cold and it won't grow.
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6
In a clean bowl, mix the soybeans and wheat, then sprinkle the Koji-kin spores over the mixture, tossing thoroughly to ensure every grain is inoculated.
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7
Spread the mixture into a shallow tray, cover with a damp cloth, and keep in a warm, humid environment (28-30°C) for 48 hours. Stir at the 24-hour mark to release heat as the mold begins to grow.
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8
Prepare the brine by dissolving the sea salt into the 2.5 liters of filtered water in your fermentation crock.
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9
Once the wheat/bean mixture is covered in a fuzzy, fragrant greenish-yellow mold (this is now called 'Shoyu Koji'), crumble it into the salt brine and stir well.
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10
This mixture is now the 'Moromi.' Cover the crock with a breathable cloth and store in a cool, dark place. Stir the mash once a day for the first week, then once a week for the next several months.
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11
Allow the Shoyu to ferment for at least 6 months (for a light, sweet sauce) or up to 12-18 months (for a deep, traditional flavor). The color will darken significantly over time.
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12
To harvest, line a colander with several layers of fine muslin and pour in the mash. Let the liquid gravity-drain for several hours, then gently squeeze the cloth to extract the remaining juice.
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13
Pasteurize the extracted liquid by heating it in a pot to 80°C (176°F) for 20 minutes. This stops fermentation and stabilizes the flavor. Skim off any foam that rises to the surface.
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14
Bottle the shoyu in sterilized glass jars and store in a cool, dark place. The flavor will continue to mellow and refine for another month in the bottle.
💡 Chef's Tips
Temperature control during the first 48 hours is the most common point of failure; use a seedling mat or an oven with the light on to maintain 30°C. Always use non-chlorinated water, as chlorine can inhibit the growth of the beneficial microbes needed for fermentation. If you see black or bright red mold during the Koji phase, discard the batch; you are looking for white, yellow, or olive-green growth. Don't rush the pressing process; gravity-draining produces a clearer, more refined sauce than heavy mechanical pressing. Sterilize all equipment with boiling water or star-san before use to prevent spoilage.
🍽️ Serving Suggestions
Drizzle over fresh Sashimi or Nigiri to experience the pure, unadulterated umami profile. Mix with a touch of grated ginger and toasted sesame oil for a premium dumpling dipping sauce. Use as a finishing seasoning for a bowl of authentic Shoyu Ramen. Whisk into a high-quality butter to create a 'Shoyu Butter' for searing scallops or steaks. Pair with a dry, cold Junmai Ginjo Sake to complement the fermented salty notes.