O-1/W/O-2 nanoemulsions and emulsions based on extra virgin olive oil produced by ultrasound-assisted homogenization process: Characterization of structure, physical and encapsulation efficiency
Oil-in-water-in-oil (O-1/W/O-2) emulsions and nanoemulsions based on extra virgin olive oil were produced combining high-speed and ultrasonic homogenizer. Droplet size distribution, encapsulation efficiency, kinetic stability, and their structure were studied as a function of homogenization time, dispersed volume fraction, emulsifier type, and composition of the inner O-1/W nanoemulsion. The ultrasonic-assisted homogenization was beneficial for the formation of O-1/W/O-2 nanoemulsion, as the intensity of the ultrasound did not destroy the double structure. The inner O-1/W nanoemulsion with the lowest droplet size, surface tension, and viscosity resulted in double nanoemulsion with the minimum droplet size (432 +/- 5 nm). Increasing the dispersed volume fraction resulted in higher particle size, gravitational separation, and high oiling off values. The DSC thermograms showed samples with the low droplet size presented also low encapsulation yield. The microscopic analysis demonstrated that all O-1/W/O-2 samples showed similar structures with distinctly visible phases and spherical aqueous droplets with a broad distribution.
