Effect of emulsifiers and local gums on the formation, some physical and rheological properties of orange peel essential oil nanoemulsions

In the present study, the influence of various emulsifiers (Tween 80, Tween 60, Tween 20, Sodium caseinate, WPC and WPI), ratio of emulsifier (Tween 80) to oil phase (orange peel essential oil) at eight levels (1, 1.5, 1.75, 2, 2.25, 2.5, 2.75, and 3:1), and the possibility of using complete form, soluble and insoluble fractions of the two native gums (Persian gum and gum tragacanth) individually and combined in the formulations on the formation and some properties of orange peel essential oil nanoemulsions was evaluated. Ultrasonic emulsification technique was used to produce nanoemulsions and the mean droplet diameter (Z-average), polydispersity index, viscosity, flow behavior, physical stability of selected formulations during storage (up to 90 days at 25˚C), as well as the total input energy during process was evaluated. Our results showed that surfactant-to-oil ratio (SOR) had a significant effect on the mentioned properties (P< 0.0001) where the lowest Z-average was observed at SOR=2. Meanwhile, none of the local gums and proteins were able to form nanoemulsions in the absence of emulsifier (Tween 80). Moreover, their soluble fractions (individually and combined at reasonably low concentration) showed significant effect (P< 0.0001) on the measured properties in the presence of emulsifier. Furthermore, the flow behavior of nanoemulsions was Newtonian, and the effect of storage time on the Z-average value was significant (P< 0.0001).