Alkaline Dissolution of Starch Facilitated by Microwave Heating for Analysis by Size-Exclusion Chromatography

A rapid, straightforward starch dissolution method was developed to facilitate analysis of starch by size-exclusion chromatrography (SEC). Soft wheat starch was dispersed in 6 M urea and 1 M KOH and subjected to heating for 35, 45, or 60 s in a microwave oven as a potential means of starch dissolution. An increase in microwave heating time enhanced starch solubility but resulted in a steady decrease in amylopectin peak area and a consequent, artifactual increase in the amylose peak area due to molecular degradation. However, microwave heating for 35 s afforded a reasonable separation of starch fractions by SEC while minimizing molecular degradation of starch in comparison to a traditional starch dissolution procedure. This procedure provides a fast (<30 min), simple, and reproducible starch dissolution method for preparation of starches for SEC analysis and represents the first successful report of direct dissolution of granular starch via microwave heating.