Morphologies and gelatinization behaviours of high-amylose maize starches during heat treatment

The granule morphologies and gelatinization behaviours of high-amylose maize starches during heating treatment were investigated by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Maltese crosses demonstrated that the high-amylose maize starches maintained a granular structure even at 120 °C. The granules of high-amylose maize starches swelled slightly at 100 °C and swelled remarkably at approximately 120 °C. The destruction of the starch structure began at the centre and expanded rapidly to the periphery. The intense fluorescence of high-amylose maize starch granules gradually became feeble, and the darker region spread outward during heating at 130 °C for 30 min, indicating that the amylose component may have been damaged and shifted. The starch granules treated at 140 °C were substantially destroyed, and the CLSM, normal light microscopy (NL) and SEM images displayed no discernible granules, which indicated that the original starch granules formed a continuous integrated matrix.