Ferrichrysin

Ferrichrysin is a type of cyclic peptide produced by yellow koji mold (Aspergillus oryzae). It is basically colorless, but it turns reddish-brown when it binds with iron. Because of this property, if iron is present in sake, ferrichrysin can act as a coloring component and give the sake as a whole a tint. Ferrichrysin is regarded as one of the important components affecting the flavor and color of sake, and its presence plays a significant role in the sake brewing process.