Optimization of water in olive oil nano-emulsions composition with bioactive compounds by response surface methodology

Nano-emulsions are increasingly used in various products in order to incorporate easily degradable bioactive compounds, protect them against oxidation and increase their bio-availability. However, achieving stable emulsion formulations with desirable properties, poses a challenging goal. In this study the composition of water in extra virgin olive oil nano-emulsions incorporating two bioactive compounds (ascorbic/gallic acid) was optimized using Response Surface Methodology (RSM). The selected composition variables were the emulsifier and bioactive compounds ratio and the examined properties were the emulsion stability, mean droplet diameter, polydispersity and turbidity. The study showed that the characteristics of the water-in-oil nano-emulsions were significantly influenced by both composition variables. The optimal formulation for producing w/o nano-emulsion with desirable characteristics incorporating ascorbic and gallic acid was provided by the same combined levels of emulsifier and bioactive compound ratio (1% w/w bioactive compound and 4% w/w Tween 20). Experimental and predicted values were in close agreement.