Mild thermal unfolding of pea protein enhances curcumin binding and interfacial properties of the resulting complexes

This study investigated how thermal treatment (80-100 °C) alters the structure of pea protein isolate (PPI) and affects curcumin encapsulation and the interfacial properties of PPI-curcumin complexes. Heating induced progressive tertiary loosening, as shown by fluorescence red shifts, increased surface hydrophobicity, and more negative zeta potential. Treatment at 90 °C produced the most favorable structural state, yielding the highest encapsulation efficiency and loading capacity and generating smaller, more uniform nanoparticles with improved stability. FTIR and XRD confirmed that curcumin was incorporated in an amorphous form and associated with PPI mainly through hydrogen bonding and hydrophobic interactions. Fluorescence quenching revealed stronger static binding in the heated samples, particularly at 90 °C. Interfacial tension and dilatational rheology showed that H90 and its complexes formed the most cohesive and elastic interfacial films. Overall, moderate thermal unfolding enhanced curcumin binding and interfacial functionality, supporting the design of heat-modified plant protein carriers in emulsion systems.