Fabrication of transparent lemon oil loaded microemulsions by phase inversion temperature (PIT) method: effect of oil phase composition and stability after dilution

This research was addressed to develop transparent microemulsions as delivery system of lemon oil. To this aim, phase inversion temperature (PIT) method was employed. The effect of the surfactant Tween 80 content as well as lipid phase type and concentration (lemon oil, peanut oil and their mixtures) on microemulsion characteristics was studied. Transparent emulsions were obtained up to 1.3 and 7.5% (w/w) of lemon oil and peanut oil, respectively. Only by considering as lipid phase a mixture of lemon oil and peanut oil, it was possible to increase the delivering capacity of emulsions up to 15% of lemon oil (total oil phase 20%). Therefore, blending peanut oil rich in long chain fatty acids with lemon oil expanded the lipid phase loading capacity of microemulsions while maintaining particle size lower than 30 nm and thus system transparency. Microemulsions showed good dilutability in aqueous solutions simulating beverage formulations with different pH values.