Oxidative modification of malondialdehyde influences the structure and emulsification properties of egg yolk high-density lipoprotein

Malondialdehyde (MDA) represents secondary active oxidation products in lipid peroxidation. This research used MDA to establish a simulated oxidation system to study its effects on egg yolk high-density lipoprotein (EYHDL) structure and emulsifying properties. It was shown that incubation of EYHDL with MDA resulted in protein carbonylation and a gradual reduction in the sulfhydryl content. Fourier transform infrared spectroscopy (FT-IR), and fluorescence spectroscopy indicated that MDA oxidation would destroy the ordered structure of EYHDL and the structural stability of the protein. Oxidation might result in the intermolecular cross-linking of EYHDL and the formation of oxidized aggregates, leading to a reduction in surface hydrophobicity. For the EYHDL emulsion modified by MDA oxidation, it could be seen that the emulsion stratification was evident at the macroscopic level, and the grain diameter of the EYHDL emulsion was observed to increase with the MDA concentration by inverted fluorescence microscopy. The emulsification activity (EAI) and emulsification stability (ESI) of EYHDL were decreased by malondialdehyde oxidation modification, which may be due to the decrease of protein surface hydrophobicity and oxidation aggregation.