What You Need to Know
During the koji stage, Aspergillus oryzae amylases hydrolyze starches into fermentable sugars while proteases cleave proteins into amino acids and peptides. Subsequent alcoholic and bacterial fermentation convert sugars into alcohols and acids, and Maillard reactions between reducing sugars and amino acids generate a complex array of flavor volatiles. The resulting matrix of glutamates, nucleotides, and aroma compounds defines the characteristic umami profile of shōyu.
The Science
Primary Reaction
Amylase‑mediated saccharification and protease‑mediated proteolysis leading to amino acids, nucleotides, and volatile aroma compounds