Removal of starch granule-associated lipids from normal and waxy wheat starches: Effects on properties, retrogradation, digestion, and molecular mechanisms.

The amylose/amylopectin ratios and starch granule-associated lipids (SGALs) between normal (NS) and waxy wheat starches (WS) influenced their physicochemical properties, retrogradation behavior and in vitro digestibility. WS had a rougher surface with more crystallized structure than NS. It swelled with higher pasting viscosity and lower gelatinization temperatures. The relative crystallinity, gelatinization enthalpy, and viscosity were decreased in defatted-NS (DNS), whereas DWS showed an opposite increase. The relative crystallinity and retrogradation enthalpy of all retrograded starch samples increased and were more significantly in DWS. The digestibility of WS was much higher than NS which was further improved by removing SGALs. Molecular dynamics simulations revealed that amylopectin had a stronger binding affinity to the active site of α-amylase than amylose (-44.45 and -24.69 kcal/mol respectively) by hydrogen bonds and van der Waals forces. However, SGALs could compete with starch molecules for binding to the active site (-23.46 kcal/mol).