Recent Insights into Protein-Polyphenol Complexes: Molecular Mechanisms, Processing Technologies, Synergistic Bioactivities, and Food Applications

Modifying proteins through grafting with polyphenols has received much attention recently due to its immense application potential. This stems from the formation of protein-polyphenol complexes, altering the structural and functional properties of the constituent molecules. In food systems, the interaction between proteins and polyphenols, including covalent and non-covalent binding, represents a green, simple, and effective strategy to transform difficult-to-process protein sources into high-value functional ingredients. In addition, the complexes formed can increase stability, biological activity, and bioavailability of polyphenols, thereby expanding their applications. Gaining insight into protein-polyphenol complexes is essential for developing novel complexes, formulations, and other applications utilizing protein and natural polyphenols. Thus, this review outlines the binding affinities and interaction mechanisms, explains factors affecting complex formation, revisits structural modulation of protein, modern processing technologies, and systematically discusses the synergistic bioactivities of the resulting complexes. We also discuss strategies to address the applications of protein-polyphenol complexes for developing functional food products with prolonged shelf life. These applications can be expanded to other industrial areas, such as pharmaceuticals and material engineering, contributing towards better nutritional quality, beneficial healthy aspects, and sustainability.