Nanocomplex of (−)-epigallocatechin-3-gallate and glycated ovalbumin based on natural deep eutectic solvents: Binding analysis and functional improvement

Natural deep eutectic solvents (NADES) are considered an efficient reaction medium for the production of glycated proteins. By optimizing the Maillard reaction conditions through response surface analysis, a glycation product (GOVA) of ovalbumin (OVA) with high grafting degree (92.2%) was prepared in choline chloride/glucose NADES. The binding information of (−)-epigallocatechin-3-gallate (EGCG) to OVA/GOVA was acquired by fluorescence spectroscopy and molecular docking. The interaction strength of GOVA + EGCG was higher than that of OVA + EGCG. Hydrogen bonding and van der Waals forces were the major driving forces in the binding process. Glycation and EGCG binding reduced the surface hydrophobicity, α-helix content and digestibility of OVA. Compared with OVA, the particle sizes of GOVA and GOVA + EGCG were increased by 54.8% and 87.7%, respectively. In addition, glycation increased the emulsifying activity index and foaming capacity of OVA by 32.6% and 20.0%, respectively, which was further increased in the presence of EGCG. The encapsulation of OVA, especially GOVA, improved the antioxidant activity, stability and bioaccessibility of EGCG. The results suggest that the glycated proteins based on NADES may provide an effective alternative for the protection and transport of bioactive ingredients in the food industries.