Generation and Stabilization of Whey-Based Monodisperse Nanoemulsions Using Ultra-High-Pressure Homogenization and Small Amphipathic Co-emulsifier Combinations

Ultra-high-pressure homogenization (UHPH) was used to generate monodisperse stable peanut oil nanoemulsions within a desired nanosize range (<100 nm) (DNR) stabilized using combinations of whey protein concentrate (WPC), sodium dodecyl sulfate, Triton X-100 (X100), and zwitterionic sulfobetaine-based surfactants differing in hydrophobicity. For WPC [2.0% (w/v)], the dispersed-phase fractions (φ) of 0.05 and 210 MPa significantly reduced the mean globule size (dvs) but the grouped frequency distribution was bimodal and larger than that of DNR. Addition of co-emulsifier sulfobetaine 3-10 (SB3-10) [7.5% (w/w) WPC] gave particles within DNR (dvs of 73 nm) though still in a bimodal distribution. Circular dichroism prior to UHPH showed little disruption of the secondary structure of proteins in WPC by SB3-10, whereas X100 obliterated it. A WPC/SB3-10 mixture retained some periodic structure even when mixed with X100 [10% (w/w) WPC] and remarkably gave a narrow monomodal distribution within DNR with the highest stability reflected by a lack of creaming after storage for 30 days (22 °C).