What is the fine-grained topic of the following text: Gesser gave a hands-on demonstration of how his fair-trade coffees are roasted, in the almighty Sivetz roaster, which accurately measures ideal bean temperature as it uses a fluid-bed roasting system which takes the raw green coffee beans and roasts them in nearly a third of the time as a drum machine. Only return the topic.
Demonstration of fair-trade coffee roasting process