Preparation and Characterization of β-Lactoglobulin Nanoparticles Loaded with Three Polyphenols

In this study, β-lactoglobulin (β-LG) nanoparticles loaded with three polyphenols were prepared by emulsification-evaporation method. Ferulic acid, quercetin and vanillic acid were combined with heat-treated β-LG to form a three-ligand complex, and then the emulsification-evaporation method was used to reduce the particle size of the complex. The structure and morphology were investigated by dynamic light scattering, circular dichroism (CD) spectroscopy, infrared spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM). The polyphenol loading efficiency and stability were studied by ultra-high performance liquid chromatography (UPLC). The results showed that the particle size of the β-lactoglobulin-polyphenol complex was reduced from the submicron level (100–200 nm) to the nanometer level (< 100 nm) by the emulsification-evaporation method. Fluorescence, infrared and CD spectra showed that the addition of polyphenols changed the microenvironment and secondary structure of β-LG. TEM images showed that the composite was approximately elliptical in shape and evenly distributed. The loading efficiencies of ferulic acid, quercetin and vanillic acid in the composite nanoparticles were 86.78%, 75.00% and 86.40%, respectively, which were 60.11%, 37.09% and 68.93% higher than those in the three-ligand complex, respectively and the former had better stability.