Description
A two-stage fermentation process where koji mold (Aspergillus oryzae) saccharifies rice starch, followed by acetic acid bacteria converting sugars into vinegar.
Technical
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.
Culinary Significance
Imparts a delicate sweetness and umami depth absent in industrial vinegars, critical for sushi rice, sunomono, and marinades.
Science
Primary Reaction
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂ (yeast) → CH₃COOH + H₂O (acetobacter)
Parameters
Temperature
28°C optimal
15°C to 38°C range
Time
3 months
3 weeks – 1 year
Equipment
Wooden koji trays (hinoki preferred)Earthenware pots (for anaerobic phases)Cheesecloth for aerobic phases