Nano Emulsion

An emulsion is a special type of mixture made by combining two liquid phases that normally don't mix (immiscible). The word "emulsion" comes from the Latin word "ēmulgēre", meaning "to milk". Emulsions usually appear opaque or white because the two (or more) phases, which, in many cases, have different refractive indexes and therefore scatter light as it passes through the phases.

Fig 1. Schematic diagram of W/O(Water-in-oil) emulsion (L) and O/W(Oil-in-water) emulsion (R)

To manufacture emulsion, amphiphilic surface-active molecules called ‘surfactants’ are added to reduce interfacial tension(σ, a force which prevents two or more phases from being easily mixed) (J. Phys.: Condens. Matter, 2006, 18, 635–666). Commonly, surfactant types can be divided into synthetic (eg. tween, span, 10-glycerol…) and natural (eg. whey protein, casein, soy protein...). They are used for emulsions considering each HLB (hydrophilic-lipophilic balance) values. Generally, if a continuous phase is hydrophilic, high HLB value surfactants are used, and if the continuous phase is hydrophobic, low HLB value surfactants are used. After adding specific surfactant, mechanical shear is needed to form an emulsifying state. In our lab, we have homogenizer, sonicator and high pressure homogenizer (HPH, microfludizer) to exert strength to physically "spread" the dispersed phase into the continuous phase.

Fig 2. Droplet size of emulsion according to the emulsifier concentrations (Soft Matter, 2014, 10, 6941–6954)

In an O/W (abbreviation for oil in water) emulsion system, oil droplets are evenly dispersed through the aqueous phase. Therefore, the system can improve physical and chemical stability of components dissolved in the oil phase against environmental factors such as light, acid, and oxygen. Especially, nanoemulsion, in which the diameter of a single droplet is no more than 200nm, has even larger droplet surface area compared to conventional emulsion, meaning it can significantly improve the bioavailability of lipid soluble active substances and enhance the storage stability from aggregation and phase separation by gravitational force.

Nanoemulsion is being applied in several industries, particularly in pharmaceutical and food. In the pharmaceutical industry, they are used to improve effectiveness by controlling dosage of active ingredients, and to provide improved aesthetics for topical drugs such as ointments. Many food products are in the form of nanoemulsions. Salad dressings, gravies and other sauces, whipped dessert toppings, peanut butter, and ice cream are also examples of emulsions of various edible fats and oils. In addition to affecting the physical form of food products, nanoemulsions impact taste because emulsified oils coat the tongue, imparting "mouth-feel". (JRank Articles, 2461, Emulsion-Uses of emulsions)

Therefore, importance of nanoemulsion in industries justifies a great deal of ongoing basic research to understand the origin of instability and to develop methods to prevent their break down. Research is needed in the area of developing highly technology oriented machinery for emulsion formation from lab scale level to pilot scale level.

The main objective of our study includes:

1. Manufacturing nanoemulsion with the useful ingredients: Development of various emulsion systems (O/W, W/O, W/O/W, O/W/O).

2. Optimization of emulsion manufacturing conditions and analyzing its physical characteristics.

3. Analysis of encapsulation efficiency and emission speed of effective components.

4. Stability analysis of nanoemulsion including functional materials: Stability of ingredients from pH, light, temperature, oxygen, etc.