Multi-scale structural and digestion resistibility changes of high-amylose corn starch after hydrothermal-pressure treatment at different gelatinizing temperatures

•The HP treatment temperature influenced the starch digestion resistibility.•The starch molecules with M of 4 × 105-4 × 106 g/mol contributed to a higher RS content.•The ordered helical complexes of higher thermostability led to the RS formation.•The higher crystallinity and enthalpy of the B + V type crystal resulted in less RS.•More ordered new repeat structure and mass fractal structure led to more RS.

The effects of gelatinizing temperature on the starch enzymatic digestion resistibility and the changes in the multi-scale structures (molecular molar mass and its distribution, molecular ordered structure, crystalline structure, lamellar structure, and granular fractal structure) of a high-amylose corn starch induced by hydrothermal-pressure (HP) processing were investigated, and the gelatinizing temperature - starch structure - digestion resistibility relationships were revealed by the combination of GPC-MALS, ATR-FTIR, XRD, DSC, and SAXS techniques. The results indicate that the short-range orders on the granular surface, the crystallinity, and the total enthalpy should not be the ultimate determinants of the resistibility against enzymatic digestion of the HP-treated starch. The degraded starch molecules with the molecular molar mass between 4 × 105 to 4 × 106 g/mol, a higher degree of the helical ordered structures of the complexes between the degraded amylose molecules and the lipid and of the complexes between the degraded amylose molecules, a newly formed repeat aggregation structure with about 18-15 nm thickness, a great amount of the ordered amylopectin crystalline lamellae, and a mass fractal structure in the length scale of 18.5 < d < 78.5 nm, all contributed to the greater resistibility against enzymatic digestion of the HP-treated starch. It was the more ordered starch molecular aggregation architecture which came from the multi-scale structural changes after the HP treatment that could be more difficult for starch enzymes to attack the active sites of starch molecules, resulted in a higher content of resistant starch.