Influence of heating time and pressure treatment of potato starch on the generation of radicals: EPR studies

The influence of heating time and pressurizing time under pressure of 1 GPa on radicals generation in potato starch polymer was investigated by EPR. Potato starch was heated at two temperatures: 413 +/- 2K (140 degrees C) and 473 +/- 2 K (200 degrees C) for 15, 30, 60, 120, 180, 240, 270 and 300 min and subdued to pressurizing under pressure of 1 +/- 0.002 GPa for 6, 60, 300 and 1440 min. In starch heated at 413 K (140 degrees C) a decrease in the relative intensity of the EPR signal as a function of the pressurizing time can be observed, whereas in starch heated at 473 K (200 degrees C) such a decrease is not observed. The EPR spectra analysis indicates that they are powder spectra due to the paramagnetic centers leading to Lorentzian line shapes with weak spectroscopic splitting factor g anisotropies and linewidth anisotropies. We have shown that pressurization of starch causes a decrease in the number of radicals in a temperature range in which the polymer is not yet disintegrated. The results of the EPR investigations indicate the existence of a carbon radical center situated at the carbon Cl of the glucose ring. In the EPR spectra of the samples heated with no oxygen access, the hyperfine structure is poorly visible. In the registered EPR spectra of the samples heated with oxygen access, the hyperfine structure is not observed. Published by Elsevier Ltd.