Study on the formation and digestibility of starch-phenolic acid complexes under ball milling treatment

In this paper, complexes of corn starch (CS) with p-coumaric acid (p-CA) and caffeic acid (CA) were prepared using ball milling for various durations. The complexes' multiscale structure, digestibility, and intermolecular interaction were explored. The ball milling treatment disrupts the orderliness of the starch double helix. Increased milling time exposes more active sites, resulting in the formation of surface-coarse complexes. The physicochemical properties and structures of the complexes varied significantly depending on the functional group and milling duration. p-CA and CA interacted with CS through non-covalent bonding to form non-inclusion complexes. Hydrogen bonding is the main driving force, and -OH and -COOH are the active sites. Phenolic acid intercalated between starch chains while wrapping the residual granules, improving the short-range ordering, thermal stability, and peak viscosity of ball-milled starch. Regarding digestibility, both phenolic acids inhibited CS digestion. However, the complexes prepared with CA, having more hydroxyl groups and longer milling times, were more effective. This study provides a basis for developing low-digestibility foods.