Variation in the structure and emulsification of egg yolk high-density lipoprotein by lipid peroxide

To further clarify the effect of the oxidation of egg yolk high-density lipoprotein (EYHDL) on the protein structure and emulsification, 2,2'-azobis (2-methylpropionamidine) dihydrochloride (AAPH) was selected as a representative lipid peroxidation-derived peroxyl radical. The results of Raman spectroscopy indicated that, with the increase in the concentration of AAPH, the EYHDL carbonyl content increased significantly and the free sulfhydryl content declined sharply. Circular dichroism spectroscopy and intrinsic fluorescence indicated that exposure of EYHDL to AAPH led to destruction of the orderly structure and reduction of the structural stability. The particle size distribution and zeta potential indicated that the peroxyl radical caused molecular aggregation. Moderate oxidizing conditions can enhance the emulsification of EYHDL, and high-intensity oxidation decreased emulsification. The research results indicated that EYHDL made a significant change in the oxidation system and led to a change in its structure and emulsification, providing a theoretical basis to clarify the EYHDL oxidation mechanism. PRACTICAL APPLICATIONS: Egg yolk powder is prone to emulsification degradation during storage. The emulsification of egg yolk powder is mainly derived from high-density lipoprotein in egg yolk. Moreover, egg yolk powder contains a large amount of lipids, and, during the processing and storage of egg yolk powder, many lipid peroxyl radicals are inevitably generated. Therefore, it is desired to combine the lipid peroxyl radicals generated during the storage of egg yolk powder with the decrease in emulsifiability. In this paper, we first investigated the effects of peroxyl radicals on the structure and emulsifying properties of high-density lipoproteins and provided a theoretical basis to solve the problem that the emulsifiability of egg yolk powder is significantly reduced during storage.