Why is milk white and not red, green or transparent?
Milk, the first food every single one of us have, the most recommended liquid food by doctors and health officials, the liquid food that is capable of strengthening the defence system of our body immune system and so goes on the list of reasons why milk is a very important part of our daily life.
In one way or the other milk I consumed by us at least once a day. Even if we are someone who hates milk, we are forced to intake it at least once a day by our peers right? Even though you are someone who hates how milk tastes, its complete white look and smell, nothing will stop your parents or peers from making you drink it. There is a reason for that and that is undoubtedly its amazing nutritional qualities.
But have you ever wondered why milk is white and not some other colour or transparent like water? If you haven’t then you will be wondering now and would want to find out why! Read on to find the answer to that and learn the reason what gives milk its white colour or how it got it.
Milk the mother of liquid foods
Before going into why milk has the colour it has, let us look why milk has the importance it has. Milk like we know is a product produced by mammals especially when they are pregnant or when they just gave birth to an offspring. Milk is a nutrient rich liquid food produced by the mammary glands of mammals.
Milk acts as the primary source of nutrients to every offspring before they can intake any solid food. So, it is like milk is what lays the foundation of nutrients and proteins in our body. Milk is also key to strengthen the immune system because of the presence of the content called colostrum which contains antibodies.
Since it is the storehouse of abundant nutrients, proteins and lactose, human beings started consuming milk after the infancy age as well by extracting them from other mammals like cows or goats. This is how the demand for dairy milk and other dairy products is always high. It is said that Dairy farms produce thousand million tonnes of milk every single year. Studies also say that more than six billion people consume milk and milk products. This is how important milk is for each and every household and considering the high nutritional value of milk this is not surprising.
The white colour of milk
You must be now curious to find out why milk is white in colour and not some other colour. If you are thinking there is some pigment that gives milk its white colour, then there is nothing of that sort. If you know what all constitutes in milk then you can notice that none of them acts as a pigment like role. Milk consists of water, sugar, fats, and several vitamins and minerals.
None of these components can act as a pigment thus there comes the question of why milk has a colour at all instead of being transparent. Chemistry is what that can give you an answer as to why milk has its white colour.
Even though milk appears to be a simple substance which is white in colour, it actually has a complex chemical nature. Milk, like mentioned earlier, is composed of water, small amounts of fat, protein, minerals, vitamins and some other compounds.
Fatty acids like palmitic, oleic, stearic and myristic acids can never mix with water and in milk with the presence of these fatty acids, the fats and water together form an emulsion. Fat has a lower density than water is why fat will never dissolve in water. If you are unaware of what an emulsion is, it is defined as a fine dispersion of very minute droplets of one liquid over another in which the former liquid is not soluble and here fat is not soluble in water and thus an emulsion gets formed.
Along with fat, there are several proteins too which are insoluble in water thus making milk a suspension of different proteins and fats floating in water. Proteins are what give milk its white colour due to their long structure, chain-like molecules formed from smaller amino acid building blocks. A suspension gets formed when there are several particles floating in a mixture without dissolving which is what is the case in milk. Casein is the main type of protein in milk and it clusters together with calcium and phosphates.
Thus, in milk, these proteins together form structures called micelles. This formation grows from small clusters of calcium phosphate, which helps in holding them together. These protein micelles are on average about 150 nanometres in diameter and this very small size gives them the ability to scatter light that hits them.
This scattering of light by the huge number of micelles in milk is why milk looks white. Yes! We could say that the colour milk has is an optical illusion and not because of any sort of pigmentation or colouring! Very interesting right? You might now be thinking why you didn’t know about such an interesting characteristic ever before.
The colour milk adapts thus because of a very interesting reason unlike other products. The many scattered light that enters the mixture gives out the white light caused due to the scattering of light by colloidal particles in the emulsion which is what gives the white colour to the milk when most of you always believed that the colour of milk was the result of some pigments.
The other colours formed during the scattering is absorbed by the white colour and thus milk is white and not any other colour or colourless. Our nature is completely filled with many interesting facts like this which can never fail to surprise us. Let us get out there and find ourselves the secrets of the world which are waiting to get unravelled like how we learned now how milk got its white colour.