Effects of koji production and saccharification time on the antioxidant activity of amazake

Abstract

Amazake was prepared using yellow-Koji (Aspergillus oryzae) or white-Koji (Aspergillus kawachii). In both cases, when rice-koji and water were mixed in a ratio of 1: 2, saccharification was completed in 6 h and reducing sugar was formed. Changes in antioxidant activity were investigated for each amazake sacchariflcation process. In both amazake preparations, DPPH (l,l-diphenyl-2-picrylhydrazyI) radicalscavenging activity increased for the first 2 h of the sacchariflcation period, and then gradually decreased. The lipid peroxidation inhibitory activity with β-carotene, however, did not change with saccharification time in either amazake preparation, and the antioxidant activity was roughly constant during sacchariflcation. Next, both types of amazake were prepared by saccharifying for 6 h at 55°C, with the respective rice-koji obtained with different koji production times (42, 48 and 54 h). Antioxidant activity was then compared. It was found for both types of rice-koji that longer koji production time yields amazake with higher DPPH radical-scavenging activity and lipid peroxidation inhibitory activity.