What You Need to Know
During the koji stage, Aspergillus oryzae secretes proteases and amylases that hydrolyze soy proteins into free amino acids—especially glutamic acid—and starches into fermentable sugars. In the brine aging phase, lactic acid bacteria and yeasts convert these substrates into organic acids, alcohols, and volatile flavor compounds, creating the characteristic umami, salty, and complex aroma profile.
The Science
Primary Reaction
Proteolytic and amylolytic hydrolysis followed by lactic acid and alcoholic fermentation