What You Need to Know
During fermentation, Aspergillus oryzae secretes proteases that hydrolyze soy proteins into free amino acids, especially glutamate, while amylases convert residual starches into sugars. Lactic acid bacteria further ferment sugars to lactic acid, lowering pH and inhibiting spoilage microbes. The resulting biochemical milieu creates the characteristic umami flavor and preserves the paste.
The Science
Primary Reaction
Proteolysis of soy proteins and starch hydrolysis by Aspergillus oryzae and lactic acid bacteria, coupled with acidification by lactic acid