In this study, wheat and flour were chosen as raw starch materials to investigate the effect of roasting on soy sauce koji-making. Indexes including activities of protease, aminopeptidase, amylaseand cellulose enzyme, NSI and other physiochemical indexes were compared between kojis of the roasted wheat and original wheat, as well as between that of the roasted flour and original flour. All the compassions were conducted under the optimum roasting time, which was determined by conversion rate of total sugars and protein recovery of kojis hydrolyzates. The optimum roasting time for both wheat and flour was 20 min, under which the enzyme systems and physiochemical indexes of kojis were well influenced. The activities of protease, aminopeptidase and cellulose enzyme, spore and NSI of koji gained from roasted wheat increased by 13.06%, 12.58%, 9.92%, 37.04% and10.46%, respectively when compared with that from original wheat. The activities of protease, aminopeptidase, cellulose enzyme, spore and NSI of koji gained from roasted flour were increased by 32.88%, 28.17%, 18.07%, 13.04% and 10.79%, respectively. The amylase activities of kojis cultivated with roasted wheat and flour both decreased a little. In conclusion, the use of both the roasted wheat and flour can improve the quality of kojis, thus starch material roasting can be an alternative way to improve the enzyme systems and physiochemical indexes of kojis.
