Get "MET" it pays...
- From: "TimEggers" <timeggers@xxxxxxxxxxx>
- Date: 19 Jun 2006 08:43:57 -0700
After the long and informational discussion sparked by Mr. Jim Schulman
about Maximum Environmental Temperatures per Mr. Carl Staub's writings
I have really changed my roasting approach and for the better.
Currently I roast in a BBQ with the RK Drum, and previously I was under
the flawed conception that my times should match the times most likely
produced in a commercial drum machine. My coffee was very "blah" and I
found it to be quite lacking not only in flavor but also in aroma.
I was roasting very hot (650F) pre-first crack (FC) and then cooling
the grill post FC. After several batches with a lower MET inside the
grill, not the drum, I can really appreciate the importance of MET.
With a two-pound load I can keep the MET below 520F (really around
515F) and reach FC in 12-13 minutes then I reduced the heat a little
and found Full City (a few snaps of second) at17 minutes. The coffee
an Ethiopian Wet Processed Sidamo has a very good-fruited complexity
with raisin/plum notes. More notably the aroma is really nice and
intense, both in dry bean form and brewed coffee. This is after a mere
24 hours rest. I can't wait to evaluate the coffee over the coarse of
the next several days.
Now I know the coffee is better and I am trying (in my limited mind) to
understand what I have been doing and why it has been working as well
as it appears to be. I think it has to do with matching application of
heat (BTU) to available airflow to produce the desired transfer rate to
meet roast level requirements in an optimum timeframe. Wow, did I
really spew all that? Anyway basically it means that for a bbq where
airflow is much different than a commercial drum a different
temperature has to be used (a higher MET versus batch size, after all
520F is awfully warm for a small 2lb load) but it is needed to produce
the speed of roast (rate of thermal transfer) to hit the best target
times for best coffee results. In reverse this is why a fluid bed
machine can use lower temps while still getting optimum times because
the thermal transfer is much faster due to the use of airflow.
In review in you opinion does roast success regardless of method used
mean matching application of BTU to airflow in order to produce the
optimum times (via a good thermal transfer rate)? I was trying to get
times that are too fast for a bbq set up by using a very high MET. Now
I have learned that slower times are better with a lower MET when using
a bbq because the airflow is much lower than a commercial drum machine
however at the same time because the airflow is less a higher MET in
relation to charge weight must be used to reach target times. I wonder
if a commercial machine using a 2lb batch really has to go clear to
520F MET to reach optimum times? I sure do when using a bbq setup.
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