Fermentos
Shoyu: Soy Sauce and Its Fermentation with Koji
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Origin: Japan · Yields: ~1 liter · Fermentation time: 6-12 months · Difficulty: High
Shoyu (Japanese soy sauce) shares the same starting point as miso: koji mold (Aspergillus oryzae) initiates the fermentation of soybeans and wheat, which then continues with bacteria and yeasts for months. Read more about this mold on our Mushrooms and Medicine page.
Ingredients
- 500 g dried soybeans, soaked and cooked
- 500 g toasted and cracked wheat
- Koji-kin (koji spores) or prepared koji
- Brine (18% salt water)
Preparation
- Mix the cooked soybeans with the toasted wheat and inoculate with koji-kin; let incubate for 2-3 days in a warm, humid environment until covered with a whitish-green layer (the koji).
- Mix the resulting koji with the brine to form the moromi (mash).
- Allow to ferment in a covered container, stirring weekly, for 6 to 12 months.
- Press the moromi to separate the liquid (shoyu) from the solids.
- Gently pasteurize before bottling.
Functional note: Shoyu is traditionally associated with umami flavor profiles developed through prolonged fermentation. This information is educational and does not substitute for the advice of a healthcare professional.
Learn more on our Fermentation page.