Influence of metal ions on thermal generation of carbohydrate radicals in native and modified starch studied by EPR

Influence of enrichment with ions from alkali (K), alkali-earth (Mg) and d transition (Cu, Fe) metal groups of native and modified starches on the process of carbohydrate radicals generation has been studied using electron paramagnetic resonance (EPR) spectroscopy. This technique allows following the character and amount of created radicals, as well as the changes in coordination sphere of transition metal ions incorporated into starch matrix. The main difference between transition metal ions and the ions of alkali and alkali-earth metals consisted in the character of their interactions with functional groups of starch. Transition metal ions coordinated glucose units of starch and influenced the mechanism of carbohydrate radical formation independently of the kind of starch modification. Interaction of starch, native and modified, with ions of alkali and alkali-earth metals did not change the mechanism of radical generation, however, influenced their number. Contents of total metal ions found analytically by spectroscopic methods and by EPR allowed determination of the amount of transition metal ions engaged in interactions with starch matrix, as well as the differentiating of native and modified starch in respect of their metal ions adsorptive ability.