Blue starch is a colored insoluble starch covalently labelled with a colored substance, Cibachron Blau F 3 G-A. The enzymatic hydrolysis of such insoluble starch yields soluble starch split products carrying the colored marker. The blue starch is commercially available.
1) A rapid and simple determination of a-amylase activity of rice-koji was established. Enzymes in 10g rice-koji was extracted with 100m
l of O.5% NaCl solution containing 5m
l of O.1 M acetate buffer of pH 5.0, homogenizing it for 4 min. In a test tube, 1.5 m
l of the enzyme solution and 4.5 m
l water were taken and prewarmed at 30°C. After addition of O.1 g blue starch preparation, the reaction mixture was stirred well and then stood still for 15 min at 30°C. Reaction was stopped by addition of 1
N NaOH solution (0.5m
l) followed by stirring. Blue color of the filtrate was measured at 620 nm.
2) Activities measured by the blue starch method were well correlated with α-amylase and the overall saccharogenic activities measured by the ordinary method; coefficient (γ) was 0.937 for α-amylase and 0.967 for the overall saccharogenic activity (sample number =35).
3) Sake was added with either heat labile or heat stable α-amylase and then pasteurized. The sake added with the heat labile a-amylase lost its activity by heating at 55°C for 1.0 min or above 60°C. Amylase activity, however, was still alived by heating at 60°C for 2.0 min in the sake added with the stable α-amylase; It was lost by heating at 65°C for 1.0 min. Therefore, it will be possible to control the pasteurization of the bottled sake checking the a-amylase actvity by the blue-starch method.
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