Effect of salts on formation and stability of vitamin E-enriched mini-emulsions produced by spontaneous emulsification.

Abstract

Emulsion-based delivery systems are being utilized to incorporate lipophilic bioactive components into various food, personal care, and pharmaceutical products. This study examined the influence of inorganic salts (NaCl and CaCl2) on the formation, stability, and properties of vitamin E-enriched emulsions prepared by spontaneous emulsification. These emulsions were simply formed by titration of a mixture of vitamin E acetate (VE), carrier oil (MCT), and nonionic surfactant (Tween 80) into an aqueous salt solution with continuous stirring. Salt type and concentration (0-1 N NaCl or 0-0.5 N CaCl2) did not have a significant influence on the initial droplet size of the emulsions. On the other hand, the isothermal and thermal stabilities of the emulsions depended strongly on salt levels. The cloud point of the emulsions decreased with increasing salt concentration, which was attributed to accelerated droplet coalescence in the presence of salts. Dilution (2-6 times) of the emulsions with water appreciably improved their thermal stability by increasing their cloud point, which was mainly attributed to the decrease in aqueous phase salt levels. The isothermal storage stability of the emulsions also depended on salt concentration; however, increasing the salt concentration decreased the rate of droplet growth, which was the opposite of its effect on thermal stability. Potential physicochemical mechanisms for these effects are discussed in terms of the influence of salt ions on van der Waals and electrostatic interactions. This study provides important information about the effect of inorganic salts on the formation and stability of vitamin E emulsions suitable for use in food, personal care, and pharmaceutical products.