An improved enzymic method for the determination of native and modified starch

Abstract

Abstract An improved method for the determination of starch by sequential hydrolysis with thermostable bacterial α‐amylase and fungal amyloglucosidase is described. Glucose was determined colorimetrically by a glucose oxidase‐peroxidase‐chromogen system at pH 7. Native normal and waxy starches, and distarch phosphate, gave quantitative yields of glucose with a high degree of precision (coefficient of variation less than 1%). Acetylated distarch phosphate, high‐amylose starch and retrograded amylose were initially treated with 1M NaOH for 30 min, then neutralised and analysed successfully as normal starch. Oxidised starch did not give a quantitative yield of glucose because of the presence of dicarboxylic groups in the polymer. For samples containing normal and waxy starch the analysis was carried out in about 4 h. The method was applied to a range of starch‐containing foodstuffs and the results are reported.