Formation, optical property and stability of orange oil nanoemulsions stabilized by Quallija saponins

Nanoemulsions have the potential to deliver insoluble materials and yet provide a transparent appearance in clear beverage applications. The influence of oil phase composition, phase viscosity and homogenization conditions on the formation, stability and optical properties of orange oil-based nanoemulsions was investigated. The nanoemulsions were formed using Quillaja saponins (QS) and homogenization accomplished using Microfluidization®. The results indicated oil phase composition and viscosity ratio between phases are key parameters determining the mean droplet diameter (MDD) of the prepared nanoemulsions. Orange oil nanoemulsions stabilized by QS showed MDD as small as 67 nm corresponding to turbidity of 71 NTU at dispersed phase concentration of 0.5 mg/g. Lipid phase refractive index showed no effect on turbidity of orange oil nanoemulsions at MDD < 150 nm, while MDD was linearly related to the turbidity with MDD ranging from 60 nm to 120 nm. Ostwald ripening was identified as main destabilization mechanism of orange oil nanoemulsions stabilized by QS at the early stage of storage. The rate of Ostwald ripening was reduced with increasing amounts of medium chain triglycerides (MCT) in the dispersed phase. An insoluble material, e.g., ester gum or MCT, was required to form stable orange oil-based nanoemulsions.