O₁/W/O₂ nanoemulsions and emulsions based on extra virgin olive oil produced by ultrasound-assisted homogenization process: Characterization of structure, physical and encapsulation efficiency

Abstract

Oil-in-water-in-oil (O₁/W/O₂) 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 O₁/W nanoemulsion. The ultrasonic-assisted homogenization was beneficial for the formation of O₁/W/O₂ nanoemulsion, as the intensity of the ultrasound did not destroy the double structure. The inner O₁/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 O₁/W/O₂ samples showed similar structures with distinctly visible phases and spherical aqueous droplets with a broad distribution.

Graphical Abstract

Keywords:

• O₁/W/O₂ nanoemulsions
• extra virgin olive oil
• CLSM
• DSC
• encapsulation stability
• ultrasound homogenization

Acknowledgement

We would like to thank Dr. Evangelia Xingi for her help with image acquisition.

Disclosure statement

All authors have no conflict of interest to declare, also they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data availability statement

Author elects to not share data.

Funding

This research received no external funding.

Author contributions

All authors have read and agreed to the published version of the manuscript.” Maria Katsouli: Methodology (lead); writing – review and editing, Conceptualization, Data curation, Writing - original draft, methodology, formal analysis. Constantina Tzia: Supervision, Validation, project administration.