Abstract
Japanese Industrial Standards of amylase for industrial use (JIS K-7001) were revised on September 1, 1990. As for the assay method for starch-liquefying activity of a-amylase, the viscosimetric method was continued though some devices were adapted to improve the accuracy and the precision and to reduce variation in results among assayers. On this revision, the starch-liquefying activity of one and the same α-amylase preparation was assayed at 7 laboratories according to the revised JIS method, 5 times per lot of substrate, using 6 and the same lots of potato starch as substrate. The results were as follows : 1) This method requires skill ; In the case of skilled assayers, coefficients of variation (CV) were about 2 to 3% ; 2) Variations of quality as substrate were significant among the lots of potato starch ; 3) The levels of assay value varied significantly among the laboratories.
