Changes in morphological and structural characteristics of high amylose maize starch in alkaline solution at different temperatures

In this study, high amylose maize starch(HAMS)was treated by Hydrothermal-alkali. SEM, SAXS, XRD, FTIR, LC-Raman, 13C CP/MAS NMR, GPC and TGA were used to study the changes in the granules and structure of HAMS. The results show that the granule morphology, lamellar structure, and birefringence of HAMS remained intact at 30 °C and 45 °C. With increasing temperature, the starch granules are fragmented, and the crystallinity, DD, FWHM values, molecular weight, and thermal stability of HAMS decrease. The double helical structure dissociated, and the content of amorphous regions increased, indicating the from order to the disorder of the HAMS structure. A similar annealing behavior occurred in HAMS at 45 °C, with the rearrangement of amylose and amylopectin occurring. At 75 °C and 90 °C, the short-chain starch produced by chain breakage regroups to form an ordered double helix structure. In general, the granule structure level of HAMS was damaged to different degrees at varying temperatures. HAMS showed gelatinization behavior in alkaline solutions when the temperature is 60 °C. This study expects to provide a model for the gelatinization theory of HAMS systems.