What You Need to Know
During incubation, Aspergillus oryzae secretes α‑amylase, converting starches into maltose and glucose, while proteases hydrolyze proteins into free amino acids such as glutamic acid. The fungal metabolism also generates organic acids that lower pH to ~5.0, suppressing bacterial growth. The resulting enzymatic activity establishes the flavor precursors for sake, miso, and soy sauce.
The Science
Primary Reaction
Starch → glucose/maltose + Protein → amino acids (e.g., glutamic acid)