Extrusion-formed starch-phenolic acid complexes: Physico-chemical properties and in vitro digestibility.

Extrusion processing was employed to prepare starch-phenolic acid complexes using three starch types (A-type corn, B-type potato, and C-type pea) and two phenolic acids (ferulic acid, FA; gallic acid, GA). The resulting complexes exhibited high complex indices (65.73-96.83%), with corn starch showing superior complexation ability and GA demonstrating higher inclusion efficiency. Structural analyses (XRD, FTIR) confirmed the formation of V-type crystalline structures with enhanced short-range order, and TGA indicated improved thermal stability. Molecular docking revealed that hydrogen bonding and van der Waals interactions primarily drove complexation. In vitro digestion experiments revealed an increase in resistant starch content ranging from 8 to 21%, with the corn starch-GA complex exhibiting the lowest digestibility-attributed to its high complex index (∼100%), highest relative crystallinity (13.09%), and elevated short-range order. Complexes formed layered spherulites that became hollow shells, sterically hindering enzymes. This study establishes extrusion as an effective strategy for preparing highly resistant digestible starch-phenolic acid complexes, highlighting the critical roles of starch source and phenolic acid structure in modulating the properties of the complexes.