Effect of Emulsifiers on Physical Properties and Stability of Oral Rice Bran Oil Nanoemulsions

Abstract

The objective of this research was to investigate the effects of emulsifier types and concentrations on the physical properties and stability of rice bran oil O/W nanoemulsions for oral administration. The nanoemulsions were formulated by using 10% of rice bran oil (RBO) as an oil phase and either single emulsifier (1,3,5% sodium caseinate (SC) or 4,6,8% polysorbate 80 (P80)) or mixed emulsifiers (1,3,5% SC and 4,6,8% P80). The nanoemulsions were prepared by Microfluidizer® at 1,500 bar for five cycles and evaluated for droplet size, polydispersity index (PDI), zeta potential, pH, and viscosity. Their physical stability was tested under heating-cooling cycles for six cycles. The results indicated that the nanoemulsions with SC (162.50-163.48 nm) had a larger droplet size than those with P80 (90.11-105.94 nm). The concentration of SC had no significant effect on the droplet size, whereas increasing the P80 concentration resulted in a significant decrease in the droplet size. For the formulations with mixed emulsifiers, an increase in the concentration of the second emulsifier leaded to a decrease in the droplet size. All nanoemulsions had narrow size distribution (PDI < 0.2), negative charge, neutral pH value, and low viscosity. The nanoemulsions with alone SC showed a larger negative charge value as compared to those with alone P80 and mixed emulsifiers. All formulations with a single emulsifier were physically stable under heating-cooling cycles for six cycles, whereas the nanoemulsions with mixed emulsifiers showed good stability for only those with the low SC concentration (1%). The rice bran oil O/W nanoemulsions obtained from this study could be developed as oral delivery systems for further applications in the pharmaceutical and food industries.