What You Need to Know
Koji inoculates steamed rice to produce amylases (breaking starch into glucose) and proteases; subsequent alcoholic fermentation by yeast (e.g., Saccharomyces cerevisiae) precedes acetobacter-driven oxidation to acetic acid.
Imparts a delicate sweetness and umami depth absent in industrial vinegars, critical for sushi rice, sunomono, and marinades.
Key Parameters
Temperature
28°C
15°C - 38°C
Time
3 months
3 weeks - 1 year
Equipment
Wooden koji trays (hinoki preferred)Earthenware pots (for anaerobic phases)Cheesecloth for aerobic phases
Steps
- 1.
Sushi-su (Edo-period Tokyo): Balances pH for fish preservation while tenderizing starches
The Science
Primary Reaction
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂ (yeast) → CH₃COOH + H₂O (acetobacter)