Effect of Carrier Oil and Co-Solvent on the Formation of Clove Oil Nanoemulsion by Phase Inversion Technique

Abstract

Development of nanoemulsion is gaining considerable attention for use in delivering hydrophobic constituents such as clove oil in foods and agriculture system. The small size of the oil droplets in the nanoemulsion system offers many advantages such as high stability, optical clarity, and improved water solubility and bioactivity. This research was aimed at investigating the effect of incorporation of carrier oil and co-solvent on the formation of clove nanoemulsion. Clove oil-loaded nanoemulsions were prepared by a low energy-phase inversion technique involving a carrier oil (medium chain triglyceride/MCT), at different ratios to the clove oil (1:2, 1:1, 2:1), a co-solvent (glycerol) at ratios of 0 and 1:1 to the mixture of clove oil and MCT and a non-ionic surfactant (Tween 80)at a ratio of 1:1, with two concentration levels of mixture of clove oil and MCT (5% and 10%). The formation and characteristics of nanoemulsion were evaluated including particle size, polydispersity index, zeta potential, and freeze-thaw stability, as well as their possible mechanisms of destabilization. Particle sizes ranged from 45.98 to 220 nm with narrow ranges of polydispersity index (0.072-0.286) and zeta potentials (-12.8 and-22.6 mV). Incorporation of carrier oil at low proportions gave smaller size of oil droplets, and the presence co-solvent enhanced nanoemulsion stabilization. Creaming accompanied by oiling-off was found upon destabilization of nanoemulsion with different rate and appearance as influenced by nanoemulsion composition. This study provides important information about stabilization of nanoemulsion by incorporating carrier oil and co-solvent suitable for foods and agrochemical formulation.