Introduction:
To understand the colour of the Emulsions, first, we must know what exactly Emulsions are. Where have you most commonly heard the word Emulsion? Usually to paint walls. But did you know that you have eaten food or used emulsion as a part of your skincare too? To give you a better explanation of your amusement, let’s find chemistry experiments from your everyday life. Whenever you are cooking something in your kitchen and you try to mix oil with water, what will happen? You will not be able to mix it. As some products are immiscible or in other terms, unblendable. Generally, when you put two substances together and observe their results, you are basically operating your own real-life, chemistry lab in your own home, in your own kitchen!
Mixing is the most common technique for different ingredients to join and create a new product. Most of the cuisines that we enjoy are the result of mixing different ingredients. However, some ingredients are immiscible. Even though we know that Oil and Water don’t mix, there are numerous food items and items in daily use in which they do get mixed together. Items like Mayonnaise, milk, hand lotions and hair conditioners. These examples represent a distinctive class of mixture known as Emulsions.
Definition:
The emulsion is a mixture of two or more liquids that are commonly immiscible. In more accustomed terms, the particles of one liquid (also known as the dispersed phase) are suspended throughout another liquid (also known as the continuous phase) to make an emulsion. This stage does not last for more than a few minutes on its own. And, the process of mixing liquids to form emulsions is known as Emulsification.
Types of Emulsions:
Emulsions can be classified generally into two types – on the basis of the properties of the dispersed phase and the dispersion medium.
- Oil in Water (O/W) :
In this type, Oil is the dispersed phase and water is the dispersion medium. Milk is the best example of this kind of Emulsion because the fats, which act as the dispersed phase, are suspended in water that acts as a dispersion medium.
- Water in Oil (W/O) :
In this type, Water is the dispersed phase and oil is the dispersion medium. For example, Cod Liver Oil consists of Particles of Water dispersed in oil. Some more common ones are Butter and Margarine.
Understanding Colours in Emulsion:
Taking the reference from the book “Colour Quality of Fresh and Processed Foods”, the author has explained that the Emulsion colour depends on their scattering (which is determined by Droplet characteristics like size, concentration, aggregation and relative refraction index) efficiency and absorption (which is decided by dye characteristics – absorption spectra and concentration) efficiency. The lightness of an emulsion is correlated to the scattering efficiency of droplets.
The colour of an Emulsion (a – and b – values) is mainly determined by the Dye type (red, green, Blue) and concentration (0-0.1wt%). Experiments showed that emulsion lightness increased steeply between 0 and 5wt%, and increased slightly at higher concentrations (5 – 20wt%). It also increased with decreasing droplet diameter (30 – 0.2 microns) and increasing refractive index between the two phases.
Appearance and Properties:
The influence of droplet characteristics on the optical properties of emulsions containing different types of dye was similar. Droplet Flocculation did have an impact on emulsion appearance.
Emulsions contain a dispersed and a continuous phase, with the boundary between the phases called the “Interface”.
So to answer our Question, ‘Emulsions tend to have a cloudy appearance because the many interfaces scatter light as it passes through the emulsion. Emulsions appear white when all light is scattered equally.’
If the emulsion is dilute enough, high-frequency light will be scattered more and the emulsion will appear blue in colour. If the emulsion is concentrated enough, the colour will be distorted towards comparatively longer wavelengths and will appear more yellow (for example – skimmed milk).
Emulsifiers / emulsifying agents:
An emulsifier is a substance that stabilizes an emulsion by increasing its Kinetic stability. They are part of a broader group of compounds also known as ‘Surfactants’. They are substances which have hydrophilic ends (polar) as well as hydrophobic ends (non-polar). Emulsifiers form a layer between the dispersed phase and the dispersion medium, thereby preventing the dispersed phase particles to come together to form larger particles and separate out.
Some common examples of emulsifiers are proteins, gums, soaps, egg yolk, mustard, sodium phosphate, soy lecithin, etc. Since there are different processes and mechanisms involved in the process of emulsification, there are several theories that accompany it. The most used ones are – Surface tension theory and Repulsion theory.
Application & Uses of Emulsion:
Emulsions are famous in various fields of science. It is used in tanning and dyeing industries, the manufacturing processes of plastics and synthetic rubber, and also used in cosmetics, and pharmaceuticals. Microemulsions are used to deliver vaccines to kill various microbes, and different food items like – mayonnaise, homogenised milk, butter, margarine, etc. Emulsifying agents are effective at extinguishing fires on small, thin-layer spills of flammable liquids – making it a kind of firefighter. And also used in chemical synthesis.
So here we learnt about why and how the appearance of Emulsion is white in colour. We also gained good knowledge about the usage and application of Emulsion and Emulsifiers. We would be glad to have feedback from our readers. It helps us to give better output every time when we get connected to our viewers. Keep viewing and stay connected with us.