Structural characteristics and foaming properties of ovalbumin-Caffeic acid complex

In this study, we investigated the effects of different caffeic acid (CA) concentrations on the ovalbumin structure and foaming properties. When the concentration of CA was 0.18 mg/mL, the surface hydrophobicity of ovalbumin decreased from 705.37 to 542.79, the sulfhydryl content decreased from 4.15 mu mol/g to 2.26 mu mol/g, and the foaming ability and stability increased by 72% and 71%, respectively. We observed that hydrophobic interactions represented the main binding force between CA and ovalbumin. Using circular dichroism spectroscopy (alpha-Helix increased from 7.2% to 13.9%) and endogenous fluorescence spectra (Reduction of fluorescence intensity and redshift), it showed that CA affected the secondary and tertiary ovalbumin structure, thus increasing the flexible structure. The increase in particle size Increased from 10.26 nm to 65.97 nm indicated that CA acted as a crosslinking agent between the ovalbumin molecules and increased the viscosity of the system through hydrophobic interactions. Although the increase in ovalbumin aggregation and the decrease in hydrophobicity were not conducive to the foaming properties of ovalbumin solutions, the increase in solubility, absolute potential, and flexible molecular structure contributed to the improvement of the foaming properties. All results showed that CA could improve the foaming properties of ovalbumin, a potential food-grade foaming agent.