Nano-emulsions are a centre of attention for many industrial applications in different fields such as pharmaceutical, cosmetic, food and agriculture due to their interesting physical properties such as transparency, larger surface area to volume ratio and long-term physical stability. This PhD project focuses on the preparation of stable nano-emulsions using different emulsification methods with an attempt to find the optimum formulation to produce stable nano-emulsions for food and healthcare applications. The emulsification methods studied in this project were rotor-stator homogeniser (Ultra-Turrax), Phase Inversion Temperature (PIT), dead-end and cross-flow membrane emulsification methods. The model system soybean oil/water/Brij 97 was used to investigate the emulsification methods. However, in the case of two membrane emulsification methods, it was decided to use Tween series surfactants as Brij 97 didn't work for our experiments. Our study showed that stable nano-emulsions containing 10 % (w/w) oil phase ratio can be produced by Homogeniser, PIT and dead-end membrane emulsification methods with droplet sizes in the range of 9 - 90 nm depending on the employed method, surfactant concentration and various experimental conditions. Cross-flow emulsification method failed to produce stable nano-emulsions in this study. PIT method yielded the smallest drop sizes in the range of 9 – 19 nm and lowest energy consumption (200 - 280 J g-1). However, for producing stable nano-emulsions by this method, the minimum amount of surfactant required were found to be 10.5 % (w/w). Dead-end membrane emulsification was also found to be a promising method for producing stable nano-emulsions with using surfactant concentration as low as 4 % (w/w) in oil, bearing also in mind that Tween series surfactants are more biocompatible than Brij 97. The only drawback for this method is its higher energy consumption than PIT method as Ultra-Turrax was used to prepare the premix. If a more energy efficient method for mixing the emulsion components is employed, this method could be a more suitable option than PIT method for food and healthcare applications. Nevertheless, PIT method could still be considered as the favourable choice when shear sensitive materials are used.
|Date of Award||18 Dec 2015|
|Supervisor||Tom Arnot (Supervisor) & Pawel Plucinski (Supervisor)|