Formulation and optimization of emulsions based on bitter fennel essential oil and EO/BO block copolymer surfactant

Abstract

The influence of EO/BO block copolymer surfactant concentration in the range (1–5% (m/m)) and emulsification time on the emulsion stability and droplet size distribution of bitter fennel essential oil-in-water emulsions has been studied.

Essential oils are promising material to be used for emulsion formulation with applications in cosmetics, food industry and agrochemicals. In the latter field these emulsions may be used as matrices for pesticides, where essential oils play the role of an eco-friendly solvent.

A two-factor central composite design was conducted in order to optimize the emulsion formulation and processing. Emulsion stability has been studied as function of ageing time, by multiple light scattering (Turbiscan Lab-expert, Formulaction) and laser diffraction (Mastersizer X, Malvern). The surface response methodology allowed us to obtain a formulation comprising minimum droplet size and maximum stability by using a single step rotor/stator homogenization process.

Creaming turned out to be the main destabilization mechanism. In order to improve emulsion stability the influence of high pressure homogenization (M110P, Microfluidics, MA, USA) and addition of a weighting agent (rosin gum) was studied. Although lower droplet sizes were obtained in both cases (D3,2 were in the range 0.30–0.35 μm), emulsions were more unstable maybe due to Ostwald ripening phenomena.