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.

In order to reveal the protective mechanism of hydrocolloid on wheat dough gluten during freezing, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to investigate the secondary structure, microstructure, disulfide bond content and water-binding capacity of gluten obtained from frozen-thawed wheat dough added with different amounts of flaxseed gum (FG) or Artemisia sphaerocephala Krasch. gum (ASKG). Results showed that freezing-thawing treatment destroyed the ordered network structure of gluten, while FG and ASKG could crosslink with the gluten protein network structure to form a stable cross-linked structure. Upon the addition of FG or ASKG at 0.4%, the gluten network structure was most uniform and dense. The addition of FG and ASKG increased the content of disulfide bond and the relative content of α-helix in gluten, making the gluten structure more stable under repeated freeze-thaw cycles. In addition, the addition of FG and ASKG reduced the surface hydrophobicity and consequently led to an increase in the waterbinding capacity of wheat gluten. The highest water-binding capacity was obtained at an addition level of 0.4% for both FG and ASKG, 1.46 and 1.43 times higher than that of the control group without added hydrocolloid undergoing repeated freezethaw cycles, respectively. All these results showed that FG and ASKG could interact with gluten to form a stable cross-linked structure, thereby enhancing the water binding capacity of gluten protein and exerting a cryoprotective effect on it.