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[[File: | [[File:Drum_Dryers.jpg|thumb|200px|right|Drum Dryers]] | ||
The Drum drying 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. | The Drum drying 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. | 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. | ||
Other products where drum drying can be used are for example starches, breakfast cereals, baby food, instant mashed potatoes to make them cold water soluble. | Other products where drum drying can be used are for example starches, breakfast cereals, baby food, instant mashed potatoes to make them cold water soluble. | ||
===Operating Principle=== | ===Operating Principle=== | ||
The '''Drum Dryers''' are basically a conduction dryer. Wet feed film (in liquid or paste form) is applied to the rotating metal cylinder inside which, a heating medium is supplied. Material film dries to the final moisture level and is scraped off. | The '''Drum Dryers''' are basically a conduction dryer. Wet feed film (in liquid or paste form) is applied to the rotating metal cylinder inside which, a heating medium is supplied. Material film dries to the final moisture level and is scraped off. | ||
===Special Features=== | ===Special Features=== | ||
* Suitable for handling liquid or pasty feeds. | * Suitable for handling liquid or pasty feeds. | ||
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* Compact installation | * Compact installation | ||
* Closed construction is possible | * Closed construction is possible | ||
===Applications=== | ===Applications=== |