Russian doctor Osip Krichevsky first produced powdered milk in 1802. It is made by drying or dehydrating milk until it forms a fine white powder. This can be achieved either by spraying a fine mist of milk into a heated chamber or by adding the milk in a thin layer to a heated surface, from which the dried milk solids can be scraped off. Freeze-drying is now used because it conserves more nutrition and the milk cane be fortified to improve its nutritional value. The resulting powder can then be stored for a long periods, because the dry environment means it is less prone to bacterial contamination that would spoil fresh milk.
As well as its potential for long term storage, powdered milk has several practical advantages over fresh milk. In the developing world, its relative light weight and the fact that is does not need refrigerating mean that it is easy to transport over long distances, without the need for expensive refrigerated trucks.
Powdered milk has found an additional use in modern science in a technique for separating proteins called Western Blotting. In this process, the protein rich milk is used to block inappropriate binding of the antibodies used, and therefore produced a much clearer result experiments.