is a method used for drying out liquids; for example, milk is applied as a thin film to the surface of a heated drum, and the dried milk solids are then scraped off with a knife. Powdered milk made by drum drying tends to have a cooked flavor, due to caramelization caused by greater heat exposure.
Compared to spray drying, drum drying is a more intense heat treatment which results in more denatured proteins. The powder is less soluble as a result. The temperature uniformity of the heated roller/drum is poor so spray drying results in better quality milk powder.