Deciphering interaction mechanisms in heat treatment time-modulated whey protein isolate-Lycium barbarum polysaccharide complexes: perspectives from structural-functional evolution

This study investigated the temporal evolution of the structure-function relationship in whey protein isolate-<i>Lycium barbarum</i> polysaccharide (WPI-LBP) complexes during 95 °C heating to identify optimal processing windows and underlying interaction mechanisms. The degree of grafting (DG) peaked at 60 min (37.43 %), confirmed electrophoretically. Solubility, emulsifying activity index (EAI), and thermal stability rose then fell with heating, while surface hydrophobicity (H₀) and free sulfhydryl (SH) content were inversely correlated, with critical points at 30 and 60 min. Circular dichroism (CD) and X-ray diffractometer (XRD) analysis showed time-dependent changes in secondary and crystal structures. Microscopy revealed and water state analysis showed that moderate heating for 30 min produced complexes with smooth surfaces and uniform aggregates. Moreover, the results suggest that WPI-LBP complexes formation is primarily driven by covalent bonds and hydrophobic interactions, supplemented by hydrogen bonds and electrostatic forces. These findings offer theoretical guidance for utilizing WPI-LBP complexes in food applications.