How to Rice Koji Inoculation

What You Need to Know

Koji inoculation involves growing A. oryzae mycelium on parboiled rice, where it secretes α-amylase (EC 3.2.1.1), glucoamylase (EC 3.2.1.3), and acid protease (EC 3.4.23.18). The rice medium provides optimal surface area (100-300 m²/kg) for hyphal penetration. In miso/doenjang production, these enzymes hydrolyze soybean proteins into glutamic acid (umami) and oligosaccharides.

Proper koji develops a chestnut-like aroma and white mycelial bloom. Korean nuruk traditionally includes wild microbes, while Japanese kōji uses pure A. oryzae strains. The inoculated rice is mixed with cooked soybeans at 1:4-1:5 ratio for miso, or 1:1 for doenjang, then fermented 3-36 months.

Key Parameters

Steps

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The Science

Primary Reaction

Starch → Maltose + Glucose (amylolysis); Proteins → Amino acids (proteolysis)

Common Mistakes