Fluid-Bed/Convection Coffee Roasting In Layman's Terms

Fluid bed coffee roasting is a method of roasting where the coffee beans are suspended on a bed of hot air currents which work to both agitate and heat the bed of coffee. It allows for the heat transfer to occur via convection rather than conduction. In a traditional coffee roaster the beans are “cooked,” by a heat source directly underneath a spinning drum. The hot metal of the spinning drum heats the air inside the drum and the beans which make contact with the side of the drum imparting thermal energy to the beans. A fluid bed roaster transfers heat evenly to the whole bean using the surrounding air and convection instead of through a point of contact with a hot surface. This makes for much more gentle heat transfer which is most pivotal for a phase of roasting called development time.

We refer to “cooking,” the inside of the bean as development. This happens after a point in the roast called first crack where the build up of oxygen inside the bean from the evaporation of the moisture overcomes the cellulose structure of the bean causing it to burst open. At this point the air can get inside the bean and this allows the inside to cook. We are then trying to get the inside of the bean to cook as much as we can before the outside starts to develop unpleasant charred or burning flavours. This is where the fluid bed roaster shines: the efficiency and evenness of the heat transfer allows the roaster to apply a more gentle heat and delay the onset of these negative flavours relative to the development of the inner bean.

So the fluid bed roaster was invented with one mission in mind: to allow for complete development of the inner bean whilst maintaining a lighter roast on the outside of the bean. What does this mean in practice? When you buy a coffee from a Roastery using fluid bed technology the coffee has the potential to be sweeter with cleaner origin characteristics whilst maintaining less bitterness or negative flavours that mask the incredible flavours of the coffee. Interested? Why not try out a bag from our shop and see what we are all about!

Footage of our typhoon roaster!