Same story here. Why did one roast come out so spicy and another using the
same profile (but different roaster) with the same spice character totally
absent? Why should a supposedly non-spicy bean such as Peru Chanchamayo
rival a Yirgacheffe in spiciness? After thinking quite a while, the only
significant difference was the cooling rate, so there I began the project.
The only reason I could think of at the time was that all of the original
project's cooling curves intersecting this region of 200F and 2 minutes had
the highest degree of spice. But after spending time on other roast stuff
and coming back months later to the proper cooling, I had trouble repeating
More recently, I am having much better success with a 2 stage cooling. When
the desired finish temperature is reached, the heater power is reduced so
that the bean temp falls to near 300F after 2 minutes. Then the heater is
turned off and only the heat from the motor and resistor allow the temp to
fall to near 170F after 1.5 minutes. At this point the beans are dumped to
finish cooling on a tray, since the temp levels out near 160 if left longer
in the popper. I am using a factory spec 1250 watt Wearever modded with a
dimmer on the heater only, so the results may only apply to similar poppers
and similar roast profiles. These times and temperatures are more or less
dictated by my setup. I need to mod another popper to change the cooling
rates significantly, especially the fast cool to handling temperature.
BTW, all bean temps are by IR.
I am still wondering about this and it should be researched more. I have not
heard from those with the PIDed and computer controlled roasters who are
better prepared to do this work.