Fast and efficient benign oxidation of native wheat starch by acidic bromate under microwave activation

A simple oxidation of starch in water by bromate was substantially improved by microwave activation. In the oxidation of native wheat starch its advantages were the highly reduced need of oxidant from 1.05 to 0.1–0.25 equiv, shortened reaction time from 2 to 5.5 h to 10 min, and moderate or high yields of oxidation content (degree of oxidation 0.22–0.55) of water-soluble products. Acidic treatment before the oxidation reaction promoted the carbonyl formation yielding higher contents of oxidized products (degree of oxidation 0.43–0.55) than without it (degree of oxidation 0.22–0.28). The pretreatment did not have similar effect on the amount of carboxyl groups. The oxidation route of acidic bromate oxidation of starch is discussed.