MODIFIED ASSAY FOR α-AMYLASE IN GERMINATING BARLEY

Abstract

The activity of α-amylase is defined as the reciprocal of the time taken by a heat-treated malt extract to reduce the iodine-colouring capacity of a solution of soluble starch to half its initial value, under standardized conditions. Reasons are given for preferring starch iodine colour to reducing power measurements for following enzyme activity. α-Amylase is extracted from grain and contaminating enzymes are largely inactivated by heating a pulverized sample in a solution of calcium acetate. Boiled extracts of coloured malt make solutions of α-amylase less stable to heat. Precautions taken to achieve accurate sampling of enzyme digests and in measuring the starch iodine colour usefully improve the precision of the method. Results are calculated graphically using standard graph principles.