Production of Nano-Emulsions by Ultra-High Pressure Emulsification (Microfluidization)

Many emulsion properties such as stability, rheology, and color, depend on the emulsion droplet size1 (EDS) and size distributions. Depending on EDS, emulsions can be divided into micro- (10-100 nm), mini (nano)- (100-1000 nm) and macro-emulsions (0.5-100 μm) [1]. Because of their very small EDS and high kinetic stability, nano-emulsions have been applied in various industrial fields, for example, personal care and cosmetics, health care, pharmaceuticals, and agrochemicals.To produce nano-emulsions, either a large amount of energy or surfactant or the combination of both is required. Low-energy emulsification methods like PIT (Phase Inversion Temperature) technique have several limitations such as requiring a large amount of surfactants and a careful selection of surfactant-cosurfactant combination. On the other hand, high-energy emulsification methods such as microfluidization are applicable to industrial operations because of flexible control of EDS distributions, and the ability to produce fine emulsions from a large variety of materials. Some workers believe microfluidization is superior because, EDS distributions appeared to be narrower and smaller in microfluidized emulsions than in the traditional emulsifying devices [2, 3]. It is shown, however, Microfluidization is unfavorable in specific circumstances such as higher pressures and longer emulsification times [4].Since the energy input by Microfluidizer is very high and re-coalescence of newly formed droplets is inevitable, there should be an optimization of the process along with appropriate selection of the emulsifier type and concentration in order to reduce over-processing and produce a stable submicron emulsion with the optimum EDS and size distribution. Since our ultimate goal was nano-particle encapsulation by spray drying of submicron emulsions, which contain biopolymers and common encapsulation ingredients such as milk proteins and starches, the aim of this work was to optimize the Microfluidization process (by varying the operating pressures and cycles) and find the best conditions and compositions of the dispersed phase and the continuous phase in terms of EDS and size distribution.