What You Need to Know
During the koji stage, Aspergillus oryzae secretes amylases that hydrolyze starch into fermentable sugars and proteases that break down proteins into peptides and free amino acids, especially glutamate. The subsequent brine fermentation allows these enzymes to continue acting while salt and temperature control suppress spoilage microbes, leading to complex flavor development over weeks to months.
The Science
Primary Reaction
Amylase-mediated hydrolysis of starch to sugars and protease-mediated hydrolysis of proteins to peptides and amino acids, especially glutamate, generating umami