Stabilization of vitamin E-enriched mini-emulsions: Influence of organic and aqueous phase compositions

Abstract

Oil-in-water mini-emulsions are finding increasing use as delivery systems to encapsulate lipophilic bioactive components such as drugs, vitamins, and nutraceuticals in functional food, personal care, and pharmaceutical products. Like all emulsions, mini-emulsions are thermodynamically unstable systems that breakdown over time. We investigated the influence of organic and aqueous phase composition on the thermal and isothermal stability of vitamin E-enriched emulsions prepared using ethanol as a co-solvent. Initially, these systems were highly unstable to droplet growth, which was attributed to droplet coalescence and/or Ostwald ripening (OR). Organic phase composition (varied by diluting with corn oil) and aqueous phase composition (varied by diluting with water) had an appreciable impact on the cloud point and stability of the emulsions. Addition of 15% corn oil to the organic phase increased the cloud point and long-term stability of the emulsions, which was attributed to decreased droplet coalescence and OR. Decreasing the ethanol concentration in the aqueous phase by dilution with water (2- to 3-fold) also improved emulsion stability, which was attributed to decreased droplet coalescence. Emulsions with the highest long-term stability could be prepared by adding corn oil to the organic phase, and water to the aqueous phase. This study provides important information about the effect of organic and aqueous phase composition on the stability of vitamin E-enriched emulsions suitable for use in pharmaceutical and food products.