Storage Conditions and Screening of Koji Molds for Starch Hydrolysis in Dried Unripe Apple Pulp

抄録

In this study, we investigated the use of koji molds for starch hydrolysis in unripe apples. During preliminary assessments of storage conditions, starch was completely broken down within 2 weeks at room temperature. However, in dried unripe apple pulp, starch remained after 7 months of storage at room temperature. Furthermore, we examined the abilities of various Aspergillus species to hydrolyze starch in dried unripe apple pulp; A. oryzae showed greater hydrolysis ability than A. awamori or A. awamori var. kawachii. Subsequently, various A. oryzae were inoculated into agar plate medium containing dried unripe apple pulp powder as the only nutritional source. Among the tested koji molds, A. oryzae AOK 139 showed the greatest growth, presumably because of its comparatively high cellulase expression. Because the starch in apples is located within walled cells, we conclude that hydrolysis requires the use of koji molds with high cellulase activity and productivity.