What You Need to Know
During the koji stage, Aspergillus oryzae secretes proteases and amylases that hydrolyze proteins into glutamyl‑glutamine peptides and starches into fermentable sugars. Lactic acid bacteria then ferment these sugars, producing lactic acid that lowers the pH and preserves the product while further releasing free amino acids such as glutamate that contribute to umami.
The Science
Primary Reaction
Proteolysis and amylolysis by Aspergillus oryzae followed by lactic acid fermentation by Lactobacillus spp.