Tea polyphenol-induced macadamia nut peptide complexes: molecular interaction mechanisms and improved emulsifying properties.

BACKGROUND: Macadamia nut peptides (MNPs) have attracted increasing attention as functional food ingredients, but their aggregation and limited interfacial activity can restrict their application in emulsion systems. Tea polyphenols (TPs) can interact with peptides and proteins through non-covalent interactions and thereby modify their structural and functional properties. This study aimed to elucidate the interaction mechanism between TPs and MNPs and to evaluate the potential of the resulting complexes as emulsion stabilizers. RESULTS: Among the tested TPs, epigallocatechin gallate (EGCG) bound to MNP, primarily through non-covalent interactions, acting as a molecular bridge to promote peptide aggregation. At an optimal 2:1 MNP-to-EGCG ratio, significant changes in particle properties and thermal stability were observed. In emulsion systems, adding 12 g kg-1 EGCG (relative to MNP mass) markedly enhanced emulsifying activity and stability, achieving improved emulsifying activity and stability at a 55% oil phase fraction. Emulsifying activity index and emulsifying stability index reached 67.60 ± 0.43 m2 g-1 and 68.70 ± 0.55 min, respectively. EGCG reduced droplet size, increased viscosity, and improved the emulsion's resilience to storage, heat, pH, and ionic changes by modulating MNP amphiphilicity. CONCLUSION: EGCG can regulate the molecular assembly and interfacial behavior of MNP through peptide-polyphenol interactions, thereby enhancing the emulsifying performance and physicochemical stability of MNP-stabilized emulsions. The optimized MNP-EGCG system provides a promising approach for developing stable functional food emulsions. © 2026 Society of Chemical Industry.