Impact of ethanol shock on the structural change and emulsifying capacity of bovine lactoferrin

The current study was focused on the structural change and emulsifying property of bovine lactoferrin (bLF) shocked by diverse ethanol levels (0%, 15%, 30%, 45%, 60%, and 75%, v/v). The fraction of β-sheet conformation was around 38.0% and dominated the bLF secondary structural component with the ethanol level from 0% to 75% (v/v). Both Try and Trp residues were involved in the interaction between bLF and ethanol. Hydrophobic effects and hydrogen bonds played crucial roles in the associations between bLF and ethanol molecules. Morphological observation revealed that the individual microstructures of bLF shocked by different levels of ethanol were irregular nanoparticles, worm-like structures, and short bars. The result of emulsifying capacity suggested that the bLF emulsion was stable at the ethanol level of 45% (v/v). Interfacial tensions were significantly decreased from 17.28 ± 0.27 to 1.78 ± 0.05 mN/m for single aqueous ethanol solutions, and from 13.58 ± 0.41 to 0.39 ± 0.01 mN/m for the bLF-E solutions with the ethanol level from 0% to 75% (v/v). Droplet size distribution results and confocal laser scanning microscopy images evidenced that ethanol molecules were adsorbed at the oil-water interface, and bLF molecules escaped from the interface with the ethanol levels from 0% to 60% (v/v). As the level of ethanol was increased from 0% to 60% (v/v), the bLF surface load was significantly decreased from 98.44 ± 0.81 to 0.06 ± 0.06 mg/m2. The findings facilitated an understanding of the impacts of the structural variation of bLF and the concentration alteration of ethanol as a co-emulsifier on the emulsifying capacity of bLF.