Trumtorkning

Trumtorkning is a drying process used in industrial production, especially in the food and ingredients sector. It refers to the technique of spreading a liquid or slurry as a thin film on the surface of a rotating heated drum. Heat transfer causes moisture to evaporate from the film, and the resulting dried layer adheres to the drum surface. A scraper then removes the dried coating, which is often ground or milled into powders, flakes, or granules for packaging and storage.

Equipment and operation in trumtorkning centers on drum design and heat source. Drums can be direct-fired or steam-heated, and the process is controlled by drum temperature, line speed, film thickness, and the viscosity or solids content of the feed. In many installations, multiple drums or a double-drum arrangement is used to increase throughput and product quality. The method is continuous, capable of handling relatively viscous feeds, and suitable for producing rehydratable products.

Applications and product characteristics vary by material. Trumtorkning is used for dairy components (such as milk or whey powders), fruit and vegetable pastes, certain starch derivatives, and other ingredients requiring dry, shelf-stable powders. Benefits include relatively simple equipment for moderate production volumes and the ability to produce uniform powders with good rehydration properties. Limitations include the potential for heat-related degradation of sensitive components, surface cracking or case hardening of the dried film if not properly controlled, and generally higher energy use for certain feeds compared with alternative drying methods.

See also: drum dryer, spray drying, food processing techniques.