Effects of Autoclaving Treatment Modifications on Multi-scale Structure and Physicochemical Properties of Yellow Rice Starch

To investigate the effect of autoclaving treatment modifications on the multi-scale structure and physicochemical properties of yellow rice starch, a comparative analysis of the multi-scale structure (morphology structure, crystal structure, and molecular chain structure) and gelatinization characteristics were conducted on the pre- and post-modified starch using high-performance anion exchange chromatography, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and rapid viscosity analyzer. The results showed that autoclaving treatment modifications did not significantly alter the total starch content of yellow rice starch. However, the content of amylose increased from 7.46% to 8.28%. In comparison to the original starch, the modified yellow rice starch exhibited an increase in the proportion of short chains, while the proportions of medium and long chains significantly (P<0.05) decreased. The weight-average molecular mass, radius of gyration, and polydispersity index of starch significantly (P<0.05) increased, while the Mn value significantly (P<0.05) decreased. The microstructure of yellow rice starch underwent significant changes from its original granular form to a flaky form with a rough surface and pore-shaped depressions after autoclaving treatment modifications. The results of infrared and X-ray diffraction patterns indicated that new functional groups were not generated in the autoclaved yellow rice starch compared to the original starch. However, the crystal structure of yellow rice starch was destroyed with a transition from the A-type to an amorphous configuration. In comparison to the original yellow rice starch, the autoclaved yellow rice starch exhibited enhanced heat stability, shear resistance, and cold paste stability, and it was less prone to retrogradation and aging. After autoclaving treatment modifications, the porosity of yellow rice starch decreased, and the glass transition temperature range narrowed. The autoclaving treatment modification has a significant impact on the multi-scale structure and gelatinization characteristics of yellow rice starch, providing a theoretical basis for further deep processing of yellow rice.