Fabrication of ultrafine edible emulsions: Comparison of high-energy and low-energy homogenization methods

Emulsions containing ultrafine droplets (r < 100 nm) have a number of potential advantages over conventional emulsions for the encapsulation and delivery of lipophilic substances in foods and beverages: high optical clarity; high physical stability; increased bioavailability. These ultrafine emulsions can be fabricated from high-energy or low-energy homogenization methods, which each have advantages and limitations. In this study, we compared a high-energy method (microfluidization) with a low-energy method (spontaneous emulsification) for forming oil-in-water emulsions from food-grade ingredients (medium chain triglycerides and Tweens). The influence of surfactant type (Tween 80, Tween 85, and Tween 80/Tween 85) and surfactant-to-oil ratio (SOR = 0.1–5) on the formation of emulsions was examined. Both the low- and high-energy methods were able to produce emulsions with ultrafine droplets (r < 100 nm). The microfluidization method required high-energy inputs and dedicated equipment, but could produce ultrafine emulsions at much lower surfactant-to-oil ratio (SOR < 0.1). On the other hand, the spontaneous emulsification method only required simple mixing, but it needed much higher surfactant-to-oil ratios (SOR > 0.5) to produce droplets with r < 100 nm. This study has important implications for the development of food-grade delivery systems to encapsulate lipophilic substances, such as flavors, colors, vitamins, and nutraceuticals.