I'm currently roasting with a Gene Cafe CBR101. There is lots of discussion around whether to cool your beans externally or with the internal cooling function. I always cool externally as the built in cooling function takes 8-10 minutes, with an external fan blowing on the machine, to cool the chamber enough that the exhaust temp goes from set point (say 240C) to 60C. During this time, the roast will coast 1/2 of a degree or or more in roast level. So, if your shooting for a full city you need to start the cooling cycle while your just into a city+ roast level.

I also always believed that keeping the beans in the chamber that long would also bake the beans (I think many others on this roaster and other fluid bed roasters with internal cooling believe the same). This is because when cupping both methods side by side the internal cooling, to me, has a flat, less flavorful and complex taste. However, I was in discussion with another roaster who told me this isn't true. His stance was that once a roast devolopes it cannot bake and that all the long cooling cycle does is advance the roast development some.

So, I'm curious to others thoughts. Is it impossible to bake a properly developed roast with an extra long cooling cycle? If so, why would a side by side yield a flat, non complex cup with the same bean roasted the exact same way but cooled different?

Look forward to hearing from others on this.

You answered your own question with the side by side. Cool as fast as possible. We used to use a Whirley Pop and would cool with light spritzes of water. Just enough not too much. Or stick them in the refir.

Coffee navigated is a nice podcast with some good info. Here is a little clip about your question: https://coffeenavigated.net/podcast/sip-1-cooling/

In 2002 Carl Staub (from Agtron) did an experiment and found that the sweetness doubled when you reduced the cooling time of your roasted beans from 5 minutes to 4 minutes. I try to keep my cooling time under four minutes.

Cooling and its effect on flavor