The Impact of High-Pressure Processing on the Structure and Sensory Properties of Egg White-Whey Protein Mixture at Acidic Conditions

This study aims to unveil the impact of high-pressure processing (HPP) on the structure and sensory properties of the mixture of egg white and whey protein at acidified conditions. Under HPP treatment, we hypothesized that egg white protein can form gel structures and encapsulate or crosslink with the whey protein, thus masking the interaction sites of whey protein with salivary protein and reduce its astringency at pH 3.5. Various characterization techniques, including turbidity measurements, zeta size, optical and scanning microscopy, native and sodium dodecyl sulfate polyacrylamide gel electrophoresis, and Fourier transform infrared spectroscopy, were used to illustrate the structural changes of the proteins and the interactions between the egg white and whey proteins. The results show that HPP treatment at 450 MPa and 600 MPa can induce significant changes to the egg white-whey protein mixture in terms of size, microstructure, secondary structure, and crosslinking. We also confirmed by electrophoresis that the egg white and whey protein form complexes through covalent bonding that feature a molecular weight of ~ 90 kDa under HPP treatment at a pH value of 3.5. Although the egg white forms microgel and may partially encapsulate the whey protein, sensory studies showed such complexation does not reduce the astringency of whey protein at acidified conditions (control astringency score = 9.0). On the contrary, the HPP-treated samples showed a higher astringency (astringency score = 11.1–11.3), possibly due to the exposure of more hydrophobic sites on the proteins.