HomeRoast Digest


Topic: My first good "dark" roast (4 msgs / 123 lines)
1) From: Ken Mary
I was wondering if my tastes were really different from most other 
roasters', since I could not get a dark roast even one snap into second
crack without what I describe as an overroast or burnt flavor. During my one
year of homeroasting, I thought I had tried all possible profiles and times
from 3 minutes to 30 minutes. I did some research looking through Sivetz'
site and found this graph:http://www.sivetzcoffee.com/images/roastdegree1.jpgI figured it was just a schematic, but I decided to follow the linear
temperature vs. time as close as possible. The Brazil Cerrado Monte Carmelo
went through first crack from 4.4 minutes to 6.6 minutes. Second crack began
at 7.4 minutes at a rate of 2 to 4 snaps per second until the roast was
stopped at 8.0 minutes. The linear temperature increase was maintained at
the prescribed 6C per minute (beginning at exactly 203C at the 3 minute
mark) by frequent adjustments of the airflow. Adjustment was stopped when
second crack began and the temperature remained constant at 232-233C until
the end. I should have continued the increase but decided to err on the safe
side. The bean volume increase was 87% and matched the graph within
experimental error. The aroma and flavor curve on the graph is at its
maximum at about 7.5 minutes which coincides with the start of my second
crack. There was no oil on any bean, even on resting overnight. Weight loss
was not measured (no scale).
After 3 brews, the first a few hours post roast and the next two the
following morning, I can detect no burnt or overroast flavors. All cups were
very smooth and slightly sweet from start to finish, and quite enjoyable.
However, the degree of roast removed the complexity and brightness that I
prefer.
--
Ken Mary - Aromaroast, Popper - whirlyblade - decanter
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

2) From: Bluedog
Congratulations on your successful roasts and discoveries. Most 
interesting report indeed, and definitely worth many experimental
roasts.
I did have a few questions and observations that came to mind, though.
You mentioned that you maintained the prescribed increment to temp per
minute via "adjustments to the airflow". Can you be a little more 
specific on this? And how were you able to maintain such an accurate
handling of the temp throughout the roast?
Sivetz mentioned that the drum roasters had attempted to do this, 
but had failed. He then went on to say that temperature control 
and measurement were an integral part of his fluid bed roasters, but
failed to elaborate on how he managed this.
I also noticed that his chart had number of minutes as part of the
information, but failed to mention what the starting batch size was
that was being roasted. I have to believe that the size of the batch
is going to directly dictate the number of minutes that it would 
take to get x amount of beans up to x temperature.
Nonetheless this does look to be very intriguing information - from
both Sivetz's graph, and your own roasting experiments. I can't wait
to find a thermometer that will measure that high so I can give 
it a go myself.
Bluedog
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3) From: Ken Mary
<Snip>
<Snip>
I use an old Melitta Aromaroast, but a popper can also be modified with
either an adjustable airflow control or a dimmer to change the fan speed.
You also need a digital thermometer that uses a fine bead thermocouple
probe. This eliminates any lag time in temperature readout. The probe is not
positioned *in* the beans but just *above* the actively mixing beans. You
might say this is wrong, but it gives the most stable readout. It does
measure the hot air temperature, but at this short distance, the air
temperature nearly matches the bean temperature. If the probe is in the
beans, it will see alternating hot air and cold beans.
<Snip>
I did not go into the Sivetz design in much detail, but I believe his
temperature probe is in a mass of hot beans that is not in the direct flow
of hot air.
<Snip>
Fluid bed roasters of different sizes are similar in design characteristics
because of the mechanics of "fluidizing" a bed of beans. A 2 ounce roaster
can be made to "behave" like a 2 pound or even a 200 pound roaster. So the
heating and roasting profiles can be identical.
From my previous roast records, I knew what bean volume to use, and what air
flow was required to reach 203C at the 3 minute mark. This should easily be
achieved with any popper or hot air roaster. The 6C per minute ramp begins
at this point.
<Snip>
Check the many online electronics suppliers. Read the list archive for some
recommendations and links. There was a recent discussion.
BTW I am drinking the last brew as I write this. It is remarkably consistent
in flavors over the 2 days. There is still no surface oil on the beans.
--
Ken Mary - Aromaroast, Popper - whirlyblade - decanter
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

4) From: Spencer W. Thomas
I found the "palatable taste range" to be quite humorous, as it excludes both
"Italian" and "French" roasts.  Clearly the residents of those countries find
this roast degree to be "palatable."  I think he's also saying that the Brits
make unpalatable coffee, with which I'd have to generally agree. :-) ;-)
=Spencer in Ann Arbor, MI
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