Abstract
(1) Proteinase activities in the soy mash juice were measured by a modification of the Anson method, and compared with those of the purely cultured soy koji digest which contained only Aspergillus proteinases.
(2) The pH-activity curves, the inhibition by specific inhibitors, acid and alkali treatments showed that the proteinases in the soy mash were almost of Aspergillus origin. Detection of bacterial proteinases was unsuccessful.
(3) The existence of a specific inhibitor was recognized in the soy mash of Aspergillus sojae strain KS, which inhibits Aspergillus proteinase, specifically at pH 8.
(4) The two peaks of activities of Aspergillus Alkaline Proteinase at pH 10.0 and at pH 7.0 had a different liberation ratio of phenolic amino acids. In some cases, the inhibition of soy mash proteinase was observed at pH 10.0 but not at pH 7.0.
(5) Bacterial viable counts of soy mash juice was not changed by heat shock. The vegetative cells of Bacilli were difficult to observe under the microscope. It is therefore considered that most of the Bacilli survive in the form of spores which had been produced in the stage of koji making, and that there are very few Bacilli growing in the soy mash.
