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Topic: Roast Profiles (6 msgs / 149 lines)
1) From: Robert Wolfe
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David, thanks for all your info. It's exactly the kind of info I'm looking 
for now.
Becaue of several requests, I'm posting some of the specs of my homemade 
roaster (even though it has not yet seen use).
I'm using a hot tub air jet blower that produces 1 hp and up to 25" of head 
pressure at 100 cfm, manually controlled continuously variable output. It's 
connected to a commercial grade air process inline heater, which looks like 
a 1/2" stainless steel pipe about 8" long. It uses 240v, draws 4 kw, and 
can raise 100 cfm of air from ambient to 1500 F under 150 psi. It's quite a 
little beast. I'm using a thermocouple and PID device operating with a 
solid state relay to control the heater. I think it will do the job.
The hot air goes into a pyrex glass roasting vessel that was produced for 
me by a technical glassblower. That vessel is the same diameter as the HWP 
roasting chamber, so that I can use an HWP chaff collector on top.
I'll post more specifics as they occur. Please post more roast profile 
info!  Thanks, all.
Robert Wolfe
Oregon Pinot Noir Club
816 Nantucket Ave.
Eugene, OR 97404
800-847-4474
Locals Only line: 607-1745
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2) From: Robert Cantor
You already know that different tastes will require different profiles, and
worse, different equipment will yeild different answers to to the same
questions.  I typically got first crack at 385 for fresh green, up to 410
for older green, and didn't like the coffee if it took longer than 4 min to
first crack.  So for me, having only tested a 2 stage model with manual
controls in a hot air popper, I liked to get to first crack in 3.5 - 4 min
max, then slow the roast so it got to second crack in 11 min.  I've gotten
good results as fast as 7 min, but that was very acidy - too acidy for most
coffees.  No coffee ever gave me a bad taste at 11 min to second crack and
end of roast.  But my second crack was always between 445-455.  I rarely
went beyond 455, although I've tried up to 470.
Bob C.
rcantor

3) From: Steven Dover

4) From: Glenn Vonk
Another benefit of longer roast profiles might be that
they favor bimolecular reactions -- like the Malliard
reaction.  This is because two molecules have to
diffuse into contact with each other for the reaction
to occur.  While diffusion will also increase with
temperature, the slower temp ramp allows more time for
diffusion and bimolecular processes before the
unimolecular (single molecule) decompositions occur. 
Intuitively, it seems the slower profile will give
more complex product profiles.  It would be
interesting to test this with an HPLC or other
analytical instrument.  Or better, I imagine its all
known is some book...  Anyone know where to find it?
Glenn
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5) From: Ken Mary
Yet another benefit of longer roast profiles is that the electricity 
suppliers make more money.    8^)
I am familiar with Illy & Viani, "Espresso Coffee". There is a discussion of
roast reactions. Here is a brief excerpt, "Roasting time may take as long as
40 minutes...or as short as 90 seconds...longer roasting periods produce
bitter and not very aromatic kinds of coffee, but permit the use of low
quality beans since most of the volatile products, good or bad, are lost.
Very short roasting periods may be insufficient for the completion of all
the pyrolytic reactions..."
There is no doubt an optimum roast time, but trial and error, rather than
calculation of reaction rates, may be the fastest and best way to determine
it.
I am working on the short end of the time spectrum. At present I am stalled
at about 2 minutes to second crack for a 100 cc batch.
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6) From: James Gundlach
On Sunday, October 6, 2002, at 09:11 AM, Ken Mary wrote:
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My own trial and error method has me looking for 15 to 17 minute 
roasts.  I also try to change level of heat rather than length of time 
to vary degree of roast.
Jim Gundlach
roasting over pecan wood fires
in La Place, Alabama
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