Emulsions: Meaning, Types, Properties and Examples

Emulsions are biphasic liquid systems that are made up of two immiscible liquid phases. These immiscible liquid phases are available in such a way that one phase is called dispersed in the other continuous phase. Emulsions are the type of a more common class of two-phase systems of matter called Colloids. Although at times the terms colloid and emulsion are often used interchangeably. The word emulsion can be used only when both of the phases are in a liquid state. Examples of emulsions include mayonnaise, milk, lotions, etc. 

Keyterms: Emulsion, Colloids, Liquid State, Emulsifier, Surface Tension, Protein

---

Introduction about Emulsion

[Click Here for Sample Questions]

An emulsion can be illustrated as a colloid consisting of two or more non-homogenous parts of liquids wherein one of the liquids contains the dispersion of the various form of liquids.

Also Read:

---

Types of Emulsions

[Click Here for Sample Questions]

Emulsions can be classified based on the properties of the dispersed phase and the dispersion medium.

There are two types of Emulsions:

1. Oil in water (O/W) Emulsion
2. Water in oil (W/O) Emulsion

Oil in water (O/W) Emulsion: In the Oil in water emulsion, the oil will be in the dispersed phase and water will be the phase or aspects of the dispersion medium. An excellent example of Oil in water is milk. In milk, the fat globules (which act as the dispersed phase) are put up in water (which acts as the dispersion medium).

Water in oil (W/O) Emulsion: Water in oil emulsion is in contrast to the Oil in water, which means in this type of emulsion, water will be in the dispersed phase and oil will be the dispersion medium. An excellent example of Water in Oil emulsion is Margarine that is a spread used for flavoring, baking, and working.

---

Emulsifier / Emulsifying agent

[Click Here for Sample Questions]

These are the materials which are added to emulsions for stabilization purpose. The various attributes of emulsifiers are as follows:

1. They are substances that have a hydrophilic end (polar) and a hydrophobic end (non-polar).
2. Emulsifier / Emulsifying agents are soluble in both water and oil.
3. Emulsifiers build a layer between the dispersed phase and the dispersion medium, thereby preventing the dispersed phase particles to come into the league to build larger particles and separate. Also, it can be cationic, anionic, or even non-polar.
4. It’s not just the percentage of water and oil that determines whether it is oil-in-water or a water-in-oil emulsion. It depends mainly on which amidst water and oil can solvate the emulsifier to a larger extent.
5. If the emulsifier is more soluble in water then the water turn into the dispersion medium and oil is converted into the dispersed phase and hence we get oil in the water emulsion.
6. On the other hand, if the emulsifier is more soluble in oil, then oil develops into the dispersion medium and water turns into the dispersed phase.
7. The generally used emulsifiers for Oil in water emulsions are proteins, gums, soaps, etc.
8. Some commonly used emulsifiers for the Water in oil emulsions are the long-chain alcohols, heavy metal salts of fatty acids, etc.
9. Some of the most common examples of emulsifiers are egg yolk, mustard, sodium phosphates, DATEM, Mono and diglycerides, cellulose, soy lecithin, etc.

---

Properties of Emulsions

[Click Here for Sample Questions]

1. Emulsions contain both immiscible liquid phases i.e. a continuous and the dispersed with the boundary coming in between the phases, that is called “interface”.
2. Emulsions have a cloudy presence due to so many phase interfaces scattering light moving through the emulsions.
3. Emulsions occur in white color when the light is dispersed in equal proportions.
4. If the emulsion is dilute, then higher-frequency and the low-wavelength type of light will be scattered in more fractions, and this type of emulsion will be converted to a blue color. This is also known as the Tyndall effect.

---

Mechanisms of Emulsification

[Click Here for Sample Questions]

Several various chemical and physical processes and mechanisms can be contained in the procedure of emulsification.

Surface tension theory – According to the theory of surface tension, emulsification takes place through the reduction of the interfacial tension that exists in the middle of the two phases.

Repulsion theory – The theory states that the emulsifying agent makes a film over one of the phases that result in the formation of globules that repel each other. This repulsive force produces them to remain suspended in the dispersion medium.

Viscosity modification – Certain emulgents such as acacia, tragacanth, carboxymethylcellulose, polyethylene glycol, etc raise the viscosity of the medium, which helps to develop and maintain the suspension of globules of the dispersed phase.

Conclusion

Emulsions are considered very essential in everyday life. A vast number of products from food to cosmetics deal with emulsions such as mayonnaise, milk, butter, creams, shampoos, and so many other daily products. This evaluation focused on the study of emulsion types, stability of the emulsion, and stability mechanisms. Based on the revised articles, it was found that emulsions stability is related to so many aspects such as phase ratios, surfactant concentrations, agitation, temperature, and other existing compounds in the system. It is also recognized that in a stabilized emulsion done by a surfactant, the surfactant monomers surround the droplets like a thin film and prevents them from the mechanism of coalescence. 

Also Read: