What You Need to Know
During fermentation, Aspergillus oryzae secretes proteases and amylases that hydrolyze proteins and starches into peptides, amino acids, and sugars. Lactic acid bacteria and yeasts further metabolize these substrates, lowering the pH to 4.5–5.0 and producing organic acids. The resulting umami flavor is largely due to glutamic acid and 5′‑inosinic acid released by proteolysis, while Maillard‑type reactions generate volatile 2‑acyl‑pyridines and methyl‑thio‑sulfonates that contribute to aroma.
The Science
Primary Reaction
Proteolysis and amylolysis by Aspergillus oryzae followed by lactic acid fermentation