How Is Dry Milk Made?
Dry milk is made by evaporating the water from milk, so that only the dry milk solids remain. The purpose of drying milk is to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Another purpose is to reduce its bulk for economy of transportation.
The most common way of drying milk is through a process called spray drying. About half the water in milk is first removed by heating the milk in a special vacuum cooker.
The thickened milk is then sprayed as a fine mist into a large drying chamber where heated air is blown from the other end. Drafts of hot air evaporate the remaining water in the milk, leaving a dry powder. When water is added, dry milk is as nourishing as fresh milk, but can be kept a long time without spoiling.
The last step in the process is to package it and send it to the customer. Powdered milk is frequently used in the manufacture of infant formula, confectionery such as chocolate and caramel candy, and in recipes for baked goods where adding liquid milk would render the product too thin.