Soy Sauce

Facts

Safety

• Documented risk factor — the moromi brine salinity is the single highest-stakes safety control point in this product's entire process, because the mash ferments anaerobically for months to over a year; inadequate salt concentration across that extended window is a materially serious theoretical vector for spoilage/pathogen risk, more consequential than in short-duration vegetable ferments precisely because of the much longer exposure window. Safe-practice guidance:
  (a) moromi brine must be prepared at a high salinity sufficient to suppress non-halophilic/pathogenic bacterial growth while still permitting the specifically halophilic/halotolerant LAB and yeast to function — commercial/traditional practice treats this as a load-bearing, non-negotiable parameter, though there is no single standardized numeric threshold published for this (flagged as requiring dedicated food-safety-authority sourcing);
  (b) koji-stage mold-species discrimination (as in miso) applies identically to stage 1 and is a separate, non-overlapping control point from moromi salinity;
  (c) commercial soy sauce is pasteurized as a final safety/stability step, an additional margin beyond the fermentation's own inherent salt/time barrier.

Method

Soy Sauce (Koji + Moromi Brine Fermentation)

• Dried soybeans — 500 g
• Wheat, roasted and cracked — 500 g, illustrative (roughly equal parts is the conventional shoyu proportion)
• Aspergillus koji spores (soy-sauce koji) — per the starter's dosing, illustrative
• Non-iodized salt, for a strong brine — SAFETY CONTROL, see linked Variant; proportion illustrative
• Water — enough to form the moromi mash

1. 1

   Step 1

   Soak and cook the soybeans until soft; drain.

2. 2

   Step 2

   Roast and coarsely crack the wheat.

3. 3

   Step 3

   Combine the cooked beans and cracked wheat and cool the mixture to below body temperature.

4. 4

   Step 4

   Inoculate with the koji spores and mix evenly.

5. 5

   Step 5

   Incubate aerobically for ~2–3 days, turning to prevent overheating, until well bloomed — this is the koji stage.

6. 6

   Step 6

   Dissolve the salt in water to make a strong brine — SAFETY CONTROL, see linked Variant.

7. 7

   Step 7

   Combine the finished koji with the brine to form the moromi mash.

8. 8

   Step 8

   Ferment anaerobically for months to over a year, stirring periodically, through the halophilic LAB and yeast succession.

9. 9

   Step 9

   Press the mature moromi to separate the liquid from the solids.

10. 10

    Step 10

    Pasteurize the pressed liquid, then bottle.

Frequently asked questions

What is Soy Sauce?

Condiment/liquid seasoning

Where does Soy Sauce come from?

Soy Sauce is traditionally made in China.

Is Soy Sauce safe to make at home?

Documented risk factor — the moromi brine salinity is the single highest-stakes safety control point in this product's entire process, because the mash ferments anaerobically for months to over a year; inadequate salt concentration across that extended window is a materially serious theoretical vector for spoilage/pathogen risk, more consequential than in short-duration vegetable ferments precisely because of the much longer exposure window. Safe-practice guidance:
(a) moromi brine must be prepared at a high salinity sufficient to suppress non-halophilic/pathogenic bacterial growth while still permitting the specifically halophilic/halotolerant LAB and yeast to function — commercial/traditional practice treats this as a load-bearing, non-negotiable parameter, though there is no single standardized numeric threshold published for this (flagged as requiring dedicated food-safety-authority sourcing);
(b) koji-stage mold-species discrimination (as in miso) applies identically to stage 1 and is a separate, non-overlapping control point from moromi salinity;
(c) commercial soy sauce is pasteurized as a final safety/stability step, an additional margin beyond the fermentation's own inherent salt/time barrier.

Community results

No community results published for this ferment yet.

Related library reading

• How Long Does Fermentation Take? A Timing Reference by FamilyTypical durations for vegetable, dairy, grain, legume and beverage ferments, why every range is wide, and what to measure instead of counting days.
• Natto, Thua Nao, Tempeh and Doenjang: The Two Ways Legumes FermentBacillus and mould take soybeans in opposite chemical directions. Which organism runs which ferment, and what that means for smell, texture and use.