In this study, we aimed to prepare stable water-in-oil (W/O) nanoemulsions loaded with a
phenolic-rich aqueous phase from olive cake extract by applying the response surface methodology
and using two methods: rotor-stator mixing and ultrasonic homogenization. The optimal nanoemulsion formulation was 7.4% (w/w) of olive cake extract as the dispersed phase, and 11.2% (w/w) of
a surfactant mixture of polyglycerol polyricinoleate (97%) and Tween 80 (3%) in Miglyol oil as the
continuous phase. Optimum results were obtained by ultrasonication for 15 min at 20% amplitude,
yielding W/O nanoemulsion droplets of 104.9 ± 6.7 nm in diameter and with a polydispersity index
(PDI) of 0.156 ± 0.085. Furthermore, an optimal nanoemulsion with a droplet size of 105.8 ± 10.3 nm
and a PDI of 0.255 ± 0.045 was prepared using a rotor-stator mixer for 10.1 min at 20,000 rpm. High
levels of retention of antioxidant activity (90.2%) and phenolics (83.1–87.2%) were reached after
30 days of storage at room temperature. Both W/O nanoemulsions showed good physical stability
during this storage period.
