Effects of Ultrasonic Operating Parameters and Emulsifier System on Sacha Inchi Oil Nanoemulsion Characteristics

The objective of this study was to investigate the effect of ultrasonic operating conditions, i.e., ultrasonic mode, amplitude, total ultrasonic duration time, and emulsifier system in producing an optimum oil-in-water of sacha inchi oil nanoemulsions (SIO-NEs). Physicochemical characteristics (including average droplet size, polydispersity index (PDI), zeta potential, and viscosity) were the evaluated response variables. Smaller droplet size was obtained from SIO-NEs prepared by ultrasonic pulse application (15s ON and 10s OFF) with an ultrasonic amplitude level of 60%. In contrast, excess energy produced by ultrasonication amplitudes of more than 60% resulted in larger average droplet size and PDI. A decrease in the absolute value of zeta potential and a lower viscosity of SIO-NEs were also observed in conjunction with the high amplitude level of the ultrasonication process. An ultrasonication duration time of longer than 10 minutes did not significantly reduce the droplet size. Five emulsifier systems were evaluated in this study, including Pluronic^®L-31, Brij^®C-10, Tween^®80, Tween^®80/Pluronic^®L-31, and Brij^®C-10/Pluronic^®L-31. The results revealed that the Brij^®C-10/Pluronic^®L-31 mixture produced the smallest droplet size (148 nm) with the lowest PDI (0.210), viscosity (3.35 cPs), and zeta potential (－31.09 mV). The concentration of the Brij^®C-10/Pluronic^®L-31 mixture, used as an emulsifier of SIO-NEs, varied from 1.5% to 9%. Based on the present findings, the most suitable concentration of mixed emulsifier used was deemed as 3% (w/v). The selected SIO-NEs were stored under room temperature to determine their droplet size stability, with the constant slightly increasing within 90 days of storage.