Intrinsic-extrinsic protein complexes as biomimetic interfacial barriers in artificial oil body systems: 1H NMR-guided mechanistic insights into oxidation resistance.

Abstract

Oil bodies (OBs) are native lipid storage organelles in plant seeds that form highly stable natural emulsification systems stabilized by intrinsic proteins (IPs). However, the poor water solubility of IPs limits their practical application in food systems. Herein, a stable two-protein complex was constructed by the simultaneous folding and co-assembly of IPs with extrinsic proteins (EPs). The co-assembly significantly improved the dispersibility of IPs and reduced their particle size, yielding a nanocomposite with a hydrophobic core that formed an OB-inspired interfacial barrier partially mimicking the interfacial composition and protective function of natural OBs, thereby enabling the formation of stable artificial oil body (AOB) emulsions under mechanical force. Structural analyses revealed that EP addition modulated the secondary and tertiary structures of the protein complex in a concentration-dependent manner, inducing partial unfolding and structural rearrangement, while stabilization was primarily governed by hydrogen bonding and hydrophobic interactions. Turbiscan Stability Index and microstructural analyses demonstrated that the composite rapidly adsorbed at the oil-water interface, forming a dense and robust interfacial film that effectively suppressed droplet aggregation through steric hindrance and electrostatic repulsion, thereby enhancing emulsion stability. Notably, 1H NMR results showed that the interfacial barrier formed by IPs and EPs at a 1:1 ratio markedly reduced lipid oxidation by inhibiting both primary and secondary oxidation pathways at the interface. Overall, this study establishes a facile biomimetic strategy for constructing interfacial barrier-based anti-oxidation system with promising applications in food emulsions.