Effect of Frozen Storage on Microstructure and Physicochemical Properties of Waxy Corn Starch

In order to provide basic data for delaying quality deterioration in waxy corn, the microstructure and physicochemical properties of waxy corn starch isolated from fresh and frozen corn (stored at −18 ℃ for 10, 20 or 30 days) were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and a rapid viscosity analyzer (RVA). The results showed that frozen storage decreased the ratio between the IR peaks at 1045 and 1022 cm^-1 (R_1045/1022) and the relative crystallinity of waxy corn starch, and increased the full width at half height. After frozen storage, pits and cracks appeared on the surface of the starch granules, and their size became smaller. As frozen storage time increased, the microstructure of corn starch was damaged more seriously. After frozen storage, the gelatinization temperature, gelatinization enthalpy, peak viscosity and breakdown value of waxy corn starch decreased, while the final viscosity and retrogradation value increased, indicating that frozen corn starch was more prone to gelatinization and retrogradation. In addition, frozen storage could convert slowly digestible starch and resistant starch into rapidly digestible starch, thereby having the potential to improve the digestion rate and degree of fresh corn.