What You Need to Know
During fermentation, Aspergillus oryzae secretes proteases that break down soy proteins into peptides and free glutamate, while amylases convert starches into sugars that feed lactic acid bacteria. The lactic acid bacteria lower the pH from ~6.5 to ~4.5, stabilizing the product and enhancing umami flavor. Proper control of salt, temperature, and time is essential to avoid spoilage and achieve the desired flavor profile.
The Science
Primary Reaction
Fermentation of soybeans by Aspergillus oryzae and lactic acid bacteria, involving proteolysis, amylolysis, and acidification.