Non-Covalent Interactions Between Quercetin and Rice Bran Protein: Mechanisms and Functional Properties

Rice bran protein (RBP) is an important plant protein, but its functional properties are reduced due to the presence of disulfide bonds in the structure. Polyphenol modification is an effective strategy to improve protein functional properties. However, the interactions between quercetin (Que) and RBP have not been well-studied. In this study, we explored the mechanism of non-covalent interactions between RBP and Que and systematically evaluated the improvement of functional properties of the RBP-Que complex. The results revealed that the addition of Que can significantly affect the particle size, ζ-potential and protein flexibility of the RBP-Que complex, and the non-covalent interactions significantly altered the secondary structure (α-helix content decreased to 20.28%, β-sheet decreased to 22.02%, β-turn increased to 29.30% and random coil increased to 28.40%) and the tertiary conformation of RBP. Spectroscopic data showed that static quenching occurred. Thermodynamic parameters showed that ΔG, ΔH, and ΔS were negative, revealing that the binding process was spontaneous and exothermic and the main reactive bonds were the hydrogen bond and the van der Waals force. When the Que concentration was 120 μmol/g, the emulsifying and foaming properties were improved by 57.72% and 71.88% compared with the RBP, respectively. The study will expand the application of RBP in the food and beverage processing industry.