What You Need to Know
The process begins with the enzymatic conversion of amylopectin into glucose and maltose by Aspergillus oryzae (koji) at 20–30 °C, yielding a sugar concentration of 10–15 % (w/v). These sugars are then metabolized by Saccharomyces cerevisiae at 20–25 °C to produce ethanol, CO₂, and flavor‑contributing compounds such as acetaldehyde and fusel alcohols. Precise temperature and pH control are essential to prevent off‑flavors, stuck fermentation, and mold contamination.
The Science
Primary Reaction
Saccharification of amylopectin to glucose/maltose by Aspergillus oryzae, followed by alcoholic fermentation of sugars to ethanol by Saccharomyces cerevisiae