Who doesn't love the taste of milk powder, whether dry or dissolved in milk. Do you know that as powder, milk can be preserved for years together? Let's have a look into how it is made.
The Italian explorer Marco Polo reported that the soldiers of Kublai Khan (the Emperor of the Mongols in the 13th century) knew how to make milk powder. They would leave milk to dry in the hot sun of the Gobi desert till it became quite thick. When they needed milk, they would put some of the dry paste in water and dissolve it.
Nowadays, milk is dried quickly in factories. There are two ways. One is called 'spray drying'. Milk is sprayed into a huge chamber and heated air is blown from the other end. The droplets of the milk dry up very quickly in the hot air and fall down. The powder can then be scraped off and packed into jars or sachets.
Another way is 'drum drying'. In this, milk is sprayed onto huge drums, which are heated by electric current. The heat makes the water in the milk evaporate and the powder stays behind on the drum. Drum-dried milk is often flaky and sticky, while spray dried milk is powdery and non-sticky.
Why dry milk? It will be a common question most of us will be wondering but the reason behind it is all living things need water to survive. This is because water is the solvent in which most chemicals dissolve. The enzymes that convert the food we eat into energy work only in a wet environment. This is true for every living organism, including bacteria. If you go to a village, you will see chillies, papads, fish, grapes (to make raisins) and other things left out to dry in the sun. In a dry environment, bacteria cannot grow and multiply. If you remove moisture from food and store it in air-tight containers it will last almost, forever.