Adsorption Properties of Cholesterol-Reduced Egg Yolk Low-Density Lipoprotein at Oil-in-Water Interfaces

The adsorption properties of cholesterol-reduced egg yolk low-density lipoprotein (CR-LDL) at oil-in-water interfaces were studied. The CR-LDL was prepared by absorbing cholesterol to β-cyclodextrin (CD). The CR-LDL formed larger emulsion particles at low protein concentration. Concentration of protein at the interface was greater for emulsions made by CR-LDL when compared to the control LDL at pH 7.0 and 3.5, a result attributed to formation of lipoprotein aggregates by removing the cholesterol in LDL. The emulsion stability of CR-LDL at low protein concentration was lower at pH 7.0 than at pH 3.5, whereas the LDL emulsions showed considerable stability during aging for 1 month. Electrophoretic analysis of the adsorbed polypeptides revealed the preferential adsorption of LDL polypeptides at the interface. Increase in protein concentration resulted in higher phosphatidylethanolamine (PE) and lower phosphatidylcholine (PC) levels at the interface, whereas the opposite trend was observed at pH 3.5. Time-dependent polymerization of lipoproteins through hydrophobic interaction at the interface was detected by SDS−PAGE analysis. Removing the cholesterol from egg yolk LDL caused changes in phospholipid−protein interactions at the interface, which could be explained the instability of CR-LDL emulsion.