Investigation on morphological structure and crystal transition of maize starch gelatinized in pure glycerol

The gelatinization phenomena and crystalline structure of maize starch gelatinized in pure glycerol were investigated using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Starch granules were firstly treated in water system, CLSM and SEM micrographs displayed that they were completely broken and the characteristic birefringence of the starch granules disappeared at 70 °C. As for pure glycerol system, the starch granules swelled but maintained granular shape with the increasing of temperature. The crystalline structure of starch granules was partially destroyed at 130 °C and completely destroyed at 140 °C. The DSC thermogram showed that the gelatinization temperature of starch in glycerol started at 123.7 °C, peaked at 128.4 °C, and concluded at 135.2 °C. The X-ray diffractograms indicated that the crystalline structure of maize starch was partially destroyed at 130 °C and completely destroyed at 140 °C. Thus, glycerol served an alternative solvent to destroy crystalline structure of maize starch, which may be helpful for hydrolysis of starch granules by amylase in food industry.