Rice bran oil (RBO) contains naturally occurring antioxidants such as carotenoids,
tocopherol, and γ-oryzanol. The aim of this research was to formulate and evaluate the
characteristics of nanoemulsion which was prepared using RBO containing naturally
occurring antioxidants. The RBO-in-water nanoemulsion was prepared by the emulsion
phase inversion method. The oil phase of the nanoemulsion was prepared by either virgin
coconut oil (VCO) or palm oil (PO) combined with RBO with the ratio of 5:5; 4:6, 3:7,
2:8 and 0:10. Tween 80 was used as a surfactant. The surfactant to oil ratios was
predetermined at 2.5:1.0 and 3.0:1.0. The aqueous phase (80% w/w) was titrated into an
organic phase that consisted of Tween 80 and oil phase (approximately 20% w/w).
Droplet size, zeta-potential and polydispersity index of the nanoemulsion were used as the
main parameters. The results showed that the smallest droplet (<100 nm) of the
nanoemulsion was obtained when the ratio of VCO: RBO at 3:7 and the ratio of PO: RBO
at 4:6 with the surfactant to oil ratio (SOR) was 2.5. Nanoemulsion with a relatively small
polydispersity index of 0.3 was achieved when the ratio of PO: RBO was 3:7 and SOR at
3. All of the freshly prepared RBO containing nanoemulsion have good stability with zetapotential values of < -30 mV. Nanoemulsions were stable against centrifugation at 2300
rpm for 15 mins, but they were not stable against heating at 105°C for 5 hrs. The RBO-inwater nanoemulsion could be successfully prepared by phase inversion method, by
combining RBO with either VCO or PO at different ratios.
Nano-emulsion formation by emulsion phase inversion
