What You Need to Know
During the koji stage, Aspergillus oryzae secretes amylases that convert starch into maltose and proteases that hydrolyze proteins into free amino acids, notably glutamic acid, which imparts umami. In the subsequent lactic fermentation, Tetragenococcus halophilus lowers the pH by producing lactic acid, while Maillard reactions between reducing sugars and amino acids generate melanoidins that deepen color and flavor.
The Science
Primary Reaction
Amylolysis, proteolysis, lactic acid fermentation, and Maillard browning of soybeans