A comparative study of covalent and non-covalent interactions between zein and polyphenols in ethanol-water solution

This study investigated the interactions of zein with (−)-epigallocatechin gallate (EGCG), quercetagetin (Q) and chlorogenic acid (CA) in ethanol-water solution (70%, v/v). Zein-polyphenol conjugates and mixtures were characterized in terms of their physical, structural, thermal, and morphological properties, as well as their antioxidant activity. The formation of zein-polyphenol conjugates was verified using GPC, SDS-PAGE and grafting efficiency determination. Zein interacted more strongly with EGCG and Q than with CA. The polyphenols could form both covalent and non-covalent complexes with zein, and their structural and functional properties depended on the nature of the complexes formed. Covalent zein–EGCG complex exhibited higher thermal stability and stronger antioxidant activity than non-covalent ones. The morphology of zein nanoparticles formed when the alcohol was evaporated also depended on the nature of the interaction and polyphenol type. This study provides useful information for the design of zein-based colloidal delivery systems for encapsulation and protection of bioactive components.