Vitamin E-enriched nanoemulsions formed by emulsion phase inversion: factors influencing droplet size and stability

There is considerable interest in using nanoemulsions as delivery systems for lipophilic bioactive ingredients, such as oil-soluble vitamins. Nanoemulsions can be fabricated using either high-energy or low-energy methods, but the latter offer advantages in terms of low cost, higher energy efficiency, and simplicity of implementation. In this study, the emulsion phase inversion (EPI) method was used to produce food-grade nanoemulsions enriched with vitamin E acetate. The EPI method simply involves titrating water into a mixture containing oil and surfactant, which initially leads to the formation of a water-in-oil emulsion that then inverts into an oil-in-water emulsion. Oil composition, surfactant type, and surfactant-to-oil ratio (SOR) were all found to influence the particle size distribution of the systems produced. Nanoemulsions with a mean particle diameter of 40 nm could be produced at a final system composition of 2 wt% MCT, 8 wt%vitamin E acetate, and 20 wt% Tween 80. The EPI method was shown to be unsuitable for producing nanoemulsions from label-friendly surfactants, such as Quillaja saponin, whey protein, casein, and sucrose monoesters. The EPI method was more effective at producing nanoemulsions at high SOR than microfluidization, but much less effective at low SOR.