Fluid Bed Coffee Roasting

Have you ever had a coffee leave you with a sour stomach and an unpleasant jittery feeling, or one that tastes burnt and bitter? You would probably assume the problem is poor quality coffee beans, but in many cases, the roasting equipment is the real culprit.

The vast majority of coffee roasters, small and large, typically use drum-style roasting machines. Many of these machines trap smoke from the roasting process inside the drum, transferring the smoke flavour to the coffee beans.

Additionally, food chemist Michael Sivetz discovered that drum roasters have very little oxygen present during the roasting cycle. This leads to the development of bitter tasting acids due to an effect known as pyrolysis. 

Smoke and Coffee Should't mix! - A Traditional Drum-Style Roaster

Sivetz went on to design and patent a coffee roaster based on the fluid bed principal which is commonly used in industrial applications, including coal-fired power plants and food drying.

The fluid bed process adapted to coffee roasting uses large volumes of heated (oxygenated) air to lift and heat the coffee slowly and evenly. (Think hot-air popcorn popper on a large scale). High oxygen levels and slow, even roasting ensure the coffee oils do not pyrolyze, which is the process that creates bitterness.