EPR studies of thermally treated oxidized corn starch

The formation of radicals in oxidized corn starch at 20-250degreesC in air was investigated by quantitative EPR spectroscopy. It was found that the presence of. carboxyl groups in the oxidized starch increases the starch's ability to generate radical species. Introducing CU2+ ions into the starch, as a catalyst or as an EPR probe, leads to the formation of copper-carboxyl complexes containing two carboxyl ligands. Drastic increase in the number of radical species at about 250degreesC is accompanied by a decrease in the intensity of EPR signal Of CU(2+_)carboxyl complexes, indicating that the thermal degradation of oxidized corn starch occurs with the formation of radicals, probably via breaking the chemical bonds in the carboxyl groups.