Nano-Emulsions; Emulsification Using Low Energy Methods

Nano-emulsions are emulsions with droplet sizes from 20 nm up to 200-500 nm, thermodynamically unstable, and appear transparent or translucent to the naked eye. Nano-emulsions are very useful in many industries; such as food, pharmaceutical, cosmetic, and chemical. Forming nano-emulsions using a method that requires energy input from a mechanical device is known as a 'high-energy method', while a method using chemical energy stored in the components is referred to as a 'low- energy method'. The low-energy method can be classified into three categories: the Phase Inversion Temperature method, Phase Inversion Composition method or Emulsion Inversion Point method and the Spontaneous Emulsification method. To study nano-emulsification using the low-energy methods, phase diagrams are used to determine the phase behavior of the components and specify the temperature and concentrations at which various structures exist at equilibrium with desired properties. Most research focuses on droplet size and polydispersibility of nano-emulsions, because these properties influence physicochemical properties, appearance and stability of nano-emulsions. There have been many studies on the effect of composition and the major determining factors in the emulsification process on droplet size and polydispersibility of nano-emulsions such as surfactant type, concentration, location, oil type, surfactant-to-oil ratio, salt, stirring speed, and temperature.