By Ted Dobek
Most people know that coffee starts out green and turns brown in a roaster.
I do it with hot air. Here’s how it works.
What is air roasting?
Picture a stream of hot air moving upward through a bed of coffee beans. With enough airflow, the beans lift and circulate. They float. That moving bed of beans is the “fluid bed.”
The air does two jobs at once. It carries heat into the coffee and also keeps the beans moving.
How is it different from drum roasting?
In a drum roaster, a rotating drum tumbles the beans. Heat reaches them through hot air and contact with hot metal.
In my Sivetz, hot air does the work of heating and moving the coffee.
Neither design automatically makes better coffee. The equipment gives you a set of tools. You still have to make good decisions with them.
What are the advantages of fluid bed roasting?
Even heat. The beans circulate through the hot air rather than relying on contact with a heated drum. That movement helps distribute heat evenly and reduces the risk of scorching from hot surfaces.
Control. My main control is inlet temperature, the temperature of the air going into the roast chamber. I can adjust that input immediately, without waiting for a heavy drum to heat up or cool down. The beans still take time to respond, but I can change the heat reaching them right away.
Clean cups. That combination of movement and responsive control gives me the tools to roast for sweetness and clarity. My goal is to develop the coffee without covering up what makes it interesting.
Consistency. I track every roast in Rostoc. I compare each batch against the roasts that tasted best and use that data to guide my adjustments. A graph can’t tell me whether the coffee tastes good, but the data helps me understand and repeat what happened.
So the next time you pick up a bag from us, just remember: we really are full of hot air.
Filed under: Roasting
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