Development of extra virgin olive and olive pomace oil nanoemulsions (o/w and w/o) enriched with surface‐active phenolic compounds

The present study explored the potential use and the effectiveness of extra virgin olive oil (EVOO) and olive pomace oil (OPO) for water in oil (w/o) and oil in water (o/w) nanoemulsion preparations. Nonionic food grade emulsifiers were examined in the formulation of the nanoemulsions and the incorporation of polyphenols extracted from olive kernel on their physicochemical properties was also investigated. The effect of the dispersed phase and the incorporated bioactive compounds was evaluated based on the mean droplet diameter (MDD) and polydispersity index (PDI), turbidity and viscosity, MDD growth, surface tension, and total phenolic content of the nanoemulsions during storage. Results were statistically evaluated using analysis of variance and Duncan's test was performed where applicable. The most effective type and the optimum ratio of the emulsifier was determined in each system (o/w–w/o, EVOO–OPO). The nanoemulsions produced presented desirable properties, in terms of kinetic stability, MDD, PDI, and viscosity and they demonstrated satisfactory physical and chemical stability during storage. MDD and PDI values were minimum in the case of o/w nanoemulsion prepared with 4% Tween 40. The stability of the nanoemulsion was enhanced by polyphenols while their retention reached ~80% being higher in o/w nanoemulsions. It was concluded that it is possible to prepare fine o/w and w/o nanoemulsions using both EVOO and OPO. The incorporation of bioactive compounds can significantly affect the nanoemulsions' properties, improving their kinetic and chemical stability. PRACTICAL APPLICATIONS: Although olive oil has been thoroughly studied for nanoemulsion preparations, there is still limited study on olive pomace oil applications. Hence, this present study was designed to compare the effectiveness of extra virgin olive oil and olive pomace oil on the formation of o/w and w/o nanoemulsion enriched with phenolic compounds extracted from the olive kernel. The novelty of work is highlighted in the following: both extra virgin olive and olive pomace oil can be suitable for the preparation of o/w and w/o nanoemulsions with good physical stability and without excessive droplet growth upon storage. These nanoemulsions can be used as a suitable means for the incorporation and protection of bioactive ingredients, such as polyphenolic compounds, and serve as an excellent delivery system as they exhibit satisfactory retention during storage.