Stability of Mexican Oregano Essential Oil Double Emulsions Obtained by Ultrasound Formulated With Whey Protein Concentrate and Tween 80

Water-in-oil-in-water (W/O/W) emulsions have a great potential use for food applications because they can protect sensitive compounds, such as essential oils. The aim of this study was to determine the effect of ultrasonic homogenization parameters: intensity (42 or 54 µm) and time (5 or 7.5 min); and formulation: oil phase proportion (20 or 30%) and emulsifier concentration (0 or 0.3%); on the physical and stability properties of Mexican oregano essential oil (OEO) in double emulsions. The emulsions were made in a two-step process, primary emulsions (W/O) containing OEO in the oil phase and ascorbic acid solution in the water phase, were stabilized with lecithin; while secondary emulsions were stabilized with 6% (w/w) of whey protein concentrate (WPC) and with or without Tween 80 (T80). Creaming, viscosity and droplet size distribution were measured to determine the stability of the W/O/W emulsions; as well as other physical properties like density and pH. The prepared W/O/W emulsions had droplet sizes between 2.89(±0.589) µm and 4.123(±0.964) µm. The most stable emulsions, with no creaming developed after 25 days of storage, were the ones formulated with WPC with T80, and additionally, 30% of the primary emulsion. Besides, higher intensity and longer time of ultrasonic homogenization conditions applied enhances W/O/W stability. Empirical models were developed for viscosity and creaming properties of W/O/W emulsions, with 99.7% of correlation coefficients, finding optimum values for specific homogenization conditions and formulation. Further studies are suggested to evaluate OEO in W/O/W emulsions as controlled release systems in food.