Description
Enzymatic breakdown of rice starch into fermentable sugars by fungal/bacterial amylases.
Technical
Alpha- and glucoamylases from Aspergillus oryzae (koji) hydrolyze α-1,4 and α-1,6 glycosidic bonds in amylose/amylopectin, producing maltose, glucose, and limit dextrins. Optimal at pH 4.0-5.5 with zinc cofactors.
Culinary Significance
Fundamental for creating fermentable substrates in sake, amazake, and koji-based miso without external sugar addition.
Science
Primary Reaction
Hydrolysis of starch → maltose + glucose (C6H10O5)n + nH2O → nC12H22O11 → 2nC6H12O6
Parameters
Temperature
30°C optimal
20°C to 40°C range
Temperature range for optimal amylase activity
Time
1 hour
30 minutes – 2 hours
Equipment
Rice cooker or large potThermometerpH meter