Low-Energy Emulsification of Edible Nanoemulsions

Abstract

Keywords: Nanoemulsion(s); Extra virgin olive oil; Surfactant; Cosurfactant; Emulsification

Objectives: Nanoemulsions are attractive for use in many food applications. The composition in the formulation should have an ability to form stable nanoemulsions and must be in food grade. The aim of this study was to characterize edible nanoemulsions incorporating extra virgin olive oil prepared by a low energy approach.

Methods: Oil-in-water nanoemulsions were prepared at different concentrations of extra virgin olive oil, polyoxyethylene sorbitan monolaurate or Tween^® 20 (surfactant) and glyceryl monocaprylate or Imwitor^® 308 (cosurfactant). Briefly, after being weighed, the mixture was heated up to 70-75 °C for 10 min before cooling down to the ambient temperature with stirring. The freshly prepared samples were characterized for the size and size distribution using dynamic light scattering technique. The linear regression analysis was used to analyse the correlation between concentration of surfactants and particle sizes in order to forecast the droplet size at infinite dilution. Moreover, nanoemulsions were examined for refractive index and viscosity.

Results: The refractive indices (RI) of nanoemulsions were approximately 1.3-1.4 while the higher values of RI were found with increasing oil and surfactant concentrations. Nanoemulsions were found to be slightly more viscous than the dispersed aqueous phase. For the particle size measurement, nanoemulsions formed in conjunction with a cosurfactant clearly showed the smaller particle size than the systems without it. Increasing amount of oil led to larger particle sizes. Most of the nanoemulsions presented the polydispersity index of less than 0.7 indicating the rather narrow size distribution of the preparations. The results indicated the requirement of the cosurfactant and sufficient amount of surfactant for the formation of nano-size of emulsion droplets. The calculated particle size at infinite dilution of nanoemulsions indicated the droplet sizes of less than 100 nm when assumed that the particles are spherical or near-spherical in shape and monodisperse.  

Conclusion: The edible oil-in-water nanoemulsions with sufficiently small particles could be formed using a low-energy emulsification method. The compositions, namely oil, surfactant and cosurfactant, were controllable in order to optimize the formation of such nanoemulsions.