Role of lysozyme on liquid egg white foaming properties: Interface behavior, physicochemical characteristics and protein structure

Lysozyme separated from egg white has high economic value and plays an important role in biochemistry, medicine and other fields. The role of lysozyme in the foaming properties of egg white was investigated in this study. After lysozyme being removed, the foaming ability (FA) and the foaming stability (FS) of egg white decreased by 45.1% and 35.3%, respectively, while restored again with lysozyme rejoining. In the absence of lysozyme, the particle size decreased and electrostatic repulsion increased, which resulted in a reduction of the protein adsorption on the interface of foam. Meanwhile, FTIR analysis showed the decrease on the protein secondary structure of α-helix and β-sheet. The reduction of hydrogen bonds played an adverse effect on the formation of stable interface. The decreased viscosity indicated the break of ovomucin-lysozyme complex, which was not conducive to the formation of viscoelastic film and leading to a reduction in FS. Furthermore, in the absence of lysozyme, the high surface tension value of the protein was harmful to the adsorption, stretching and rearrangement of protein molecules on the interface. This research provided a new opinion into the effect of lysozyme on the foaming properties of egg white.