Emulsification

Ever wondered why a mixture of oil and water appears the way it is? Or why do cream and buttermilk not mix? The answer to these naturally occurring phenomena is emulsification.

Let us try to understand emulsification much more deeply and learn about its several properties.
The process of formation of phases in a liquid-liquid mixture that leads to the formation of emulsions is known as emulsification. Emulsification always takes place when one immiscible liquid is mixed with another immiscible liquid.

The immiscible liquid usually contains bioactive compounds, due to which it is dispersed in the other immiscible liquid using either electrostatic or hydrogen bonding interactions. It has to be noted that emulsion always occurs in a liquid-liquid mixture or when two immiscible liquids are mixed. Some common examples of emulsions are:-
1. Egg yolks
2. Milk
3. Butter
4. Cream
5. Buttermilk

Other examples also include latex, hand cream, vinaigrettes, cutting fluid, etc. There also exist several types of emulsions. They are as follows:-

1. Simple Emulsions

Emulsions formed by mixing oil in water, water in oil, etc., are known as simple emulsions. Examples of simple emulsions are water in oil emulsion, oil in water emulsion, etc.

2. Complex Emulsions

Emulsions that contain complex systems such as oil in water and water in oil coexisting together are called complex emulsions. These emulsions are also called multiple emulsions, and they are often stabilized as surfactants. Examples of complex emulsions are water in oil in water emulsion, oil in water in oil emulsion, etc.

Several properties of emulsions include certain aspects such as cloudy appearance, variable size of particles that are immersed due to difference in solution, the appearance of colors in the dispersed solution, and the ability to demonstrate the Tyndall effect. It has to be noted that both the emulsion phases may be separated if they are kept undisturbed for quite some time or in the absence of an emulsifying agent.

There are several methods due to which the process of emulsification can take place. They are as follows:-
1. By reducing the interfacial tension present between the dispersed phase and the dispersed medium, we can conclude that emulsification occurs. This is based on the surface tension theory.
2. The repulsion theory also states a significant way in which emulsification can take place. According to the theory, the repulsive force present between the dispersed particles causes them to maintain their state in the dispersed medium. The catalytic agent generates a film over a single phase that makes the globules of the phase and repel each other.
3. Emulsification can also occur when we introduce an emulsifying agent that increases the viscosity of the dispersed medium. Due to this increase, the particles, i.e., globules of the dispersed phase, maintain the dispersion in the medium.

What is an emulsifier?

Now, as we know that emulsification is a process where two immiscible liquids form an emulsion. Hence, we need the help of an external agent if the immiscible liquids do not mix.

An emulsifier helps in the process of emulsification by stabilizing the emulsion. It coats the droplets and keeps them separate from each other. If the emulsifier is not used, the droplets would be clumped together, which would cause the emulsion to separate.

Examples of emulsifiers in our day-to-day life include surfactants or surface-active agents like detergents, mustard, diacetyl tartaric acid ester of monoglyceride, lecithin, soy lecithin.

Uses of emulsification and emulsions

The most common example is the cleansing action of regular soaps, detergents, etc., on the formation of an oil-water emulsion on clothes, crockery, dishes, etc. Specific other applications of emulsification and emulsions include:-

1. Food industries widely use emulsions such as mayonnaise (oil in water emulsion mixed with an egg yolk), Ganache or chocolate with cream(milk fat and cocoa fat in sugar solution emulsion), vinaigrettes (oil in vinegar emulsion), pesto, several soups, and sauces.
2. Metalworking processes also use emulsions such as cutting fluid. It is used as a type of coolant or lubricant.
3. Other applications of emulsions are used in hair creams, gels, vaccines, personal hygiene, cream, balms, ointments, etc.
4. Nano-emulsions are also found to be used on surfaces as a type of disinfectant.
5. Various drugs that contain a high concentration of oil are also formed as emulsions.
6. Certain operations such as the building of roads, construction of buildings, etc., use emulsion. For example, asphalt emulsified in water is leveraged in the entire process of building roads. This helps to reduce the cost of melting asphalt.