Physicochemical properties of whey protein, lactoferrin and Tween 20 stabilised nanoemulsions: Effect of temperature, pH and salt

•Formation of nanoemulsions using different types and concentrations of emulsifiers.•Whey protein isolate or lactoferrin produced smaller droplets than Tween 20.•Lactoferrin nanoemulsions had good stability to heat treatment, pH and salt.•Tween 20 nanoemulsions were unstable to high temperature at 90 °C for 15 min.•Whey protein isolate nanoemulsions unstable at pH 4.5–5.5 and at >30 mM CaCl2.

Oil-in-water nanoemulsions were prepared by emulsification and solvent evaporation using whey protein isolate (WPI), lactoferrin and Tween 20 as emulsifiers. Protein-stabilised nanoemulsions showed a decrease in particle size with increasing protein concentration from 0.25% to 1% (w/w) level with Z-average diameter between 70 and 90 nm. However, larger droplets were produced by Tween 20 (120–450 nm) especially at concentration above 0.75% (w/w). The stability of nanoemulsions to temperature (30–90 °C), pH (2–10) and ionic strength (0–500 mM NaCl or 0–90 mM CaCl2) was also tested. Tween 20 nanoemulsions were unstable to heat treatment at 90 °C for 15 min. WPI-stabilised nanoemulsions exhibited droplet aggregation near the isoelectric point at pH 4.5 and 5 and they were also unstable at salt concentration above 30 mM CaCl2. These results indicated that stable nanoemulsions can be prepared by careful selection of emulsifiers.