Effect of Molecular Interaction between Ovalbumin and Chlorogenic Acid on Protein Structure and Emulsion Stability

Polyphenols and proteins are important material sources that constitute a complex food system. Molecular interactions between polyphenols and proteins would change the structure of proteins and improve emulsion stability. It has become a research hotspot in the current food processing field. In this experiment, the interaction between ovalbumin (OVA) and chlorogenic acid (CA) was studied by fluorescence spectroscopy, synchronous fluorescence spectroscopy, circular dichroism, and infrared spectroscopy. The OVA-CA complex was used to prepare high stable emulsion. The experimental results showed that OVA and CA were 1:1 binding. The binding site is closer to the position of the tryptophan residue in the OVA molecule. The quenching mechanism of CA to OVA‛s endogenous fluorescence was static quenching, and the main force of the combination was hydrophobic interaction. The addition of CA would change the protein secondary structure of OVA. Among of them, the content of !-helix increased, and the content of β-sheet gradually decreased with the increase of CA concentration. The ratio of CA and OVA was optimized according to the particle size of the emulsion. The results showed that the particle size was the smallest when the ratio of CA and OVA was 1:0.1. The particle size was (755.13±140.29) nm. Compared with OVA emulsion, OVA-CA emulsion remains stable for 7-day at room temperature, while the pH value and salt ion (0-0.125 mol/L) stability of OVA-CA emulsion were significantly improved. This research will provide a theoretical basis for improving the functional properties of egg white protein and expand the application of egg white protein in food processing. © 2022 Chinese Institute of Food Science and Technology. All rights reserved.