Trommelroaster

A Trommelroaster, or drum roaster, is a device used to roast coffee beans by heating them inside a rotating drum. The beans tumble as the drum turns, promoting even heat exposure and development of aroma and flavor.

Drum roasters consist of a metal drum that rotates on bearings, usually driven by an electric motor. The drum is heated by a gas burner or electric elements, and hot air is exhausted through an outlet. Some designs use a perforated inner drum to improve air flow, while others rely on direct contact with a heated surface. A cooling tray and controls for charge size, drum speed, and heat input are commonly included.

During roasting, green beans are loaded after preheating. The beans expand and darken as they are heated, and audible cracks signal development stages. Operators monitor temperature and roast color to reach the desired level. Drum roasters are favored for even heat distribution and can support nuanced flavor development, especially for light to medium roasts. They range from small home units to large commercial installations.

Advantages include uniform heat, flexibility in roast profiles, and longer development times that help create balanced flavors. Limitations include slower heat-up, higher energy use, a larger footprint, and more maintenance than some other methods. The Trommelroaster is associated with traditional coffee roasting and remains in use among specialty roasters that prioritize control and repeatability.