Effect of phosphorylation and pretreatment with high hydrostatic pressure on radical processes in maize starches with different amylose contents

Waxy maize (amylopectin with trace amounts of amylose) and Hylon VII starch containing mostly amylose were phosphorylated in acidic or alkaline medium to produce mono- or distarch phosphates, respectively. The changes in the starch structure and properties occurring upon phosphorylation and high pressure treatment (650 MPa/9 min) were analyzed using X-ray diffraction (XRD), differential scanning calorimetry (DSC), polarized light microscopy (LM) and electron paramagnetic resonance (EPR) spectroscopy. Quantitative EPR measurements revealed that incorporation of phosphorus into the starch structure increased tendency of the starch to be thermally degraded with formation of radicals, the effect being more pronounced in the case of monostarch phosphates than in distarch phosphates. Pretreatment of the starch with high hydrostatic pressure resulted in diminishing of the number of radicals generated thermally in monostarch phosphates.