Drum drying removes moisture from food products using heated, rotating drums to create flakes or powder that can be rehydrated. It is commonly used for potato chips, dry milk, baby food, and dehydrated soup mixes. Different types of drum dryers are used depending on the food product, and vacuum drum drying is a more expensive but less damaging method. Spray drying is a newer technique that allows for temperature adjustments and particle size control.
Drum drying defines a process used in the food industry to remove moisture from pastes, purees and liquids with heated, rotating drums. The procedure converts wet food products into flakes or powder that can be rehydrated by the consumer. Drum drying uses a precise combination of steam pressure, temperature, rotational speed and product thickness to retain flavor and color.
Food manufacturers typically use drums to make potato chips, dry milk, baby food, dehydrated soup mixes, and some breakfast cereals. The process could also convert the apples into applesauce, but drummed nuts pose a challenge due to their high sugar content. Drum drying retains ample starch, along with additives and stabilizers, in the production of instant mashed potatoes.
The potatoes are washed and peeled as the first step in the dehydration process. They are then cut and cooked to create a paste. The puree is applied to the outer surface of an internally heated drum to remove most of the water content. Usually, the moisture evaporates within seconds, allowing the final product to be removed from the drum using scrapers.
Equipment used for drying typically employs one or two stainless steel or cast iron cylinders resting on a frame. Depending on the intended use, dryers can be purchased with single, double or twin drums. Single and double drum dryers are most commonly used in the dehydration of fruits and vegetables.
Single drum drying, usually used for potatoes, feeds the mash outside the drum. Double drum drying employs two cylinders that rotate towards each other and is commonly used to make tomato paste. The distance between the drums determines the thickness of the food layers. The twin drum dryers rotate away from each other, controlling dust during the food drying process.
A vacuum drum dryer works in a similar way, but uses lower temperatures for foods that could be damaged by extreme heat. The drums on this type of equipment are sealed inside a vacuum chamber and are a form of dehydration that is considered expensive. Steam drum drying is a more efficient method of dehydrating food products.
Drum drying came into use in the 1990s before the development of spray drying techniques. Spray drying exposes high-moisture foods to hot air inside a machine that quickly removes the water. These newer machines allow for temperature adjustments for different types of food and desired particle size.
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