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Topic: more slow cooling, was Re: +Getting the chaff out (5 msgs / 117 lines)
1) From: Ken Mary
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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.
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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
the results.
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.
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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.
--

2) From: Bob Yellin
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When
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so
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is
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to
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to
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longer
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a
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poppers
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less
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cooled in
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then
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for my
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 not
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I never thought much about ramping the cooling phase of the roast before =
I
had PID control of my air roaster, but now that I have 3 or 4 ramp/soak
segments to spare (out of a total of 8) after the roast is complete, I =
can
play with the cooling. I'm open to any suggestions relative to the
approach, but if none are offered, I guess I'll just take a bean I have =
in
sufficient quantity for a series of roasts (Yirgacheffe 4453 or Guat
Antigua, for example) and run some comparisons, keeping the ramp-up the
same and just varying the cooling. I can get to about 160 from 440 in a
minute-and-a-half with my fan going full blast and the heater off, so =
that
should give a good range for cooling trials. Any suggestions?
Bob Yellin

3) From: Ken Mary
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You have a starting point with my cool to 300F in 2 minutes, then to 170 in
another 1.5 minutes. My thinking is that nothing important happens below
300F at least on the cooldown. Choose some ramps and elapsed times, then
taste the results. It would be important for all roasts to be from the same
lot of coffee. However, I found the results to be nearly universal across
coffee origins, so you are looking for an obvious flavor difference, not
just some nuance that needs a trained taster or blind cupping.
--

4) From: Bob Yellin
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that
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 in
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same
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across
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OK - I'll do some roasting on Thursday and report next week.

5) From: Felix Dial


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