Insights into ball milling treatment promotes the formation of starch-lipid complexes and the relation between multi-scale structure and in vitro digestibility based on intermolecular interactions

Abstract

This study aimed to investigate the changes in the physicochemical properties, multiscale structure and in vitro digestibility of the corn starch (CS)- lauric acid (LA) complexes under ball milling treatment to elucidate the correlation between structure and digestibility based on intermolecular interactions. The findings showed that the apparent viscosity of CS decreased significantly with the increasing of ball milling time from 0 min to 60 min, and the average molecular weight decreased from 561.96 kDa to 274.66 kDa, which laid the foundation for the subsequent experiments. Scanning electron microscopy (SEM) results indicated with increasing ball milling time, the surface morphology of the CS-LA complexes became more and more rough and agglomerated. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) findings indicated that the CS-LA complexes prepared by ball milling exhibited higher thermal stability, better short-range ordering and a compact V-shaped crystal structure. In terms of digestibility, the rapidly digested starch (RDS) content of the CS-LA complexes decreased by 15.93% and the resistant starch (RS) increased by 14.96%, reducing the digestibility of the starch. Density functional theory (DFT) calculations showed that the ordered structure and intermolecular interactions between LA and CS were mainly composed of hydrogen bonds and hydrophobic interactions. We tentatively established the interconnection between multi-scale structure and digestibility through correlation analysis, which provided technical support for further exploitation of starch resources.