Objective To investigate the effect of complexes produced by protein-polyphenol interaction on the bioavailability of polyphenols and proteins.Methods Rutin-casein complexes are prepared using rutin and casein as raw materials. Their physicochemical and structural properties are analyzed.Results The optimal preparation conditions for the rutin-casein complexes are determined as follows: mass ratio of rutin to casein=1.89∶1.00, reaction time of 5.94 h, pH 8.5, and temperature of 50 ℃. Under such conditions, the binding degree is 40.23%. Compared with casein, the complexes exhibit a decrease in emulsifying activity index (8.47 m²/g) and emulsifying stability (9.39%). The solubility increases by 5.11%, surface hydrophobicity is significantly enhanced, and antioxidant activity markedly improves (P<0.05). Scanning electron microscopy reveals that the rutin-casein complexes display a lamellar structure with smooth surfaces, which may contribute to its functional properties. Infrared spectroscopy demonstrates peak broadening and redshifts in the amide I and II bands, and fluorescence intensity (including synchronous fluorescence) decreases due to fluorescence quenching. It indicates that rutin alters the secondary structure and conformational arrangement of casein.Conclusion Compared with the uncomplexed casein, the rutin-casein complexes are enhanced in solubility, surface hydrophobicity, and antioxidant activity.