HomeRoast Digest


Topic: thermometer differential question (160 msgs / 4371 lines)
1) From: John Abbott
Cathy,
We Wok roasted last night. It wasn't as smoky as I had anticipated. We did
the roasting on the patio and the cool evening breeze (81 degrees) was
enough to keep the smoke from building up and carried the chaff away. One
can certainly hear the snaps clearly! My neighbor came over with a bowl of
rice - to poke fun at me. But decided it wasn't a bad way to roast after we
finished. He thinks BLACK is the right color for roasts - so we burned a
small load for him. He had his this morning for breakfast and claimed it was
good (the man lacks character!) and we'll try ours tomorrow. Knowing now how
well it can turn out - I include our wok as a legitimate backup roaster. 
Question - How big a load have you successfully done in the wok?
John
--

2) From: John Abbott
Lacking any data I did what most guys do - guesses. I used 200 grams for =
the
test - seemed to work (wok) well. It'll be a bit before I wok again becau=
se
I'm a little ahead on roasted beans. But I'll step right up to the 250 gr=
am
load next pass.  I just cheated an made a press from the roast last night=
 -
better than the standard FR but not quite up to the drum roaster.
Thanks for the guidance.
John
--

3) From: John Abbott
Only on THIS list could we begin a discussion of a bean profile and generate
lessons in thermal dynamics, and a few other laws of physics. I sense a
discussion coming now of EMF, hi/lo mu, left and right hand rules.
I am unscientific in my roasting in that I work backward from the result to
determine my next best effort. I cannot control the bean roast beyond the
movement of the beans in a heated chamber. I can control the heating cycle
and measure the results. If I had my lab at Boeing Aerospace at my disposal
I don't believe I could better control the bean - my limitation. I'm not
sure that a great deal of my satisfaction from the HotTop stems from a very
acceptable as-is result. Can it be improved? Certainly! Could I pick a
better bean to roast? Probably. But I'm extremely happy with what I'm
drinking.
I wouldn't trade this list for anything. I absolutely love all this science
and near-science that makes me think constantly. And I get to laugh a LOT! 
I am so glad you are all here!!
John - wandering deep Southern Texas
--

4) From: John Abbott
What intensity of purple would a full city roast be??     Now THERE's a
topic!!
John - got to run - or be late for church.
--

5) From: Kevin DuPre
I have a question regarding a thermometer placed in
the roasting chamber to monitor bean temperature. I
have one of the dial thermometers sold by Sweet
Marias, and the probe is placed through a small
drilled hole in the top of my Fresh Roast with a
spacer on the outside to adjust the level of the probe
tip to be at the top of the "fill to here" band. This
position puts it approximately in the middle of the
expanding/expanded beans through the critical
landmarks of the roasting process.
I have noticed from a number of publications both Tom
& Marias roasting guide and Kenneth Davids "roasting
book" specific temperatures at specific degrees of
roast.
These temperatures are documented as INTERNAL bean
temperatures. However since I can't put the probe
inside the beans, I have to assume that there will be
a temperature differential between the interior of the
bean and the exterior where I am making the
measurement. 
I have run a cycle of the roaster with a "dry" chamber
and observed a peak temperature of around 350 degrees,
370 with the vents open (mfg. states that opening the
vents will increase heat by about 20 degrees so this
observation is consistent with the  design of the
roaster).  I have also run about 47 batches through
the roaster and observed temperatures up to about
460-470 degrees with beans at a full-city style so I
assume the increase is due to the exothermic phase of
the roast after 1st crack.
What I have observed is that a Kenya AA roasted to a
light full city occurs with a reading on the
thermometer of around 460 which is around 20 seconds
into a 'rolling' second crack.
However the published temps for Full City on the light
side cite 415-425. Let's say 420 for discussion's
sake. This would mean that the thermometer is off by
40 degrees...or there is a 40 degree HIGHER temp
outside the beans than internal  bean temperature.
I have checked the thermometer against a 220 degree
thermometer and it registers within a degree or two
from room temp to a rolling boil all the way through
this range, so unless there is high non-linearity
beyond 220 I have to assume that the thermometer is
within about 5 degrees of the actual temperature it is
measuring.
Has anybody observed similar differential using such
thermometers, and if so, how much?
Regards,
Kevin
=====
--
Kevin DuPre
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6) From: Jim Schulman
A roast chamber thermometer measures the temperature of the air around the 
beans, and perhaps on the surface. The readings are not consistent from 
roaster to roaster or thermometer to thermometer. However, the same set up 
is consistent from roast to roast. So if you want to repeat a roast, the 
temperature reading is more precise than a timer.
In my case, my nose and eye is more accurate then the thermometer, but 
mine isn't that good.
Jim
On 27 Aug 2002 at 19:48, Kevin DuPre wrote:
<Snip>
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7) From: Rick Farris
Kevin wrote:
<Snip>
Actually, Kevin, I think that the reason for the higher temperatures when
the roaster is loaded is because the beans slow down the air, allowing it
(and the beans) to absorb more heat energy from the heating element, hence a
higher temperature.  There may be *some* exothermic component, but I'm
betting on simple thermodynamics.
Another effect is that adding more beans shortens roasting time and less
beans lengthens roasting time, for the same reason.
-- Rick
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8) From: Kevin DuPre
Rick, Dan and Jim,
Thanks for the replies on the thermo differential.  I
kind of thought that's what was happening (on all
three of your replies).
When I tried strictly roasting to the thermometer and
the "published" temps, the roasts were too light.
The other night when I roasted the Kenya AA, I decided
to roast to my observation of the beans, in smell,
color and amount of oil as indicators (which is a much
better one - the eyes and nose), and THEN observe the
temperature at which these things occur.
Sounds like I'll have to make my own temperature table
and use that based on my setup.
The purpose of using the thermometer (and a stopwatch)
is as one of you said, for consistency.  I have also
noticed that the first roast in a roasting session
takes longer to develop the roast, I'm assuming
because everything is cold and once I've done that
first batch things warm up quicker for subsequent ones
(subsequent roasts in a session are typically within
3-5 minutes of each other).
Thanks again for your insights on this.
Kevin
=====
--
Kevin DuPre
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9) From: Dan Bollinger
Kevin,  Measuring bean temperature in a small roaster is tricky.  Measuring
bean temperature in a hot air roaster or fluid bed roaster is tricky.
Combine the two and you are in for some large differences like you are
seeing.
You may have to calibrate the roasts you want to the readings you are
getting.  Keeping the probe away from the air stream will help. Dan
<Snip>
in having new eyes -- Marcel Proust"
<Snip>
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10) From: R.N.Kyle
This is a multi-part message in MIME format.
Kevin wrote HI have checked the thermometer against a 220 degree
thermometer and it registers within a degree or two
from room temp to a rolling boil all the way through
this range, so unless there is high non-linearity
beyond 220 I have to assume that the thermometer is
within about 5 degrees of the actual temperature it is
measuring.
Has anybody observed similar differential using such
thermometers, and if so, how much?
hey Kevin, I roast with FR+ with the small dial therm. from SM and find =
the same temps as you are talking about. at rolling 2nd crack about 465, =
2nd crack starts at about 450. I to was wondering if this is outside =
temp and if the inside was cooler?
Ron Kyle
a coffee roaster from South Carolina
rnkyle

11) From: Kevin DuPre
If we consider basic thermodynamic principles and that
the beans are in exothermic phase due to pyrolysis
following first crack one would think that the
INTERNAL bean temperature is much higher than its
exterior temperature.
From my measurements of empty chamber which is
approximately 100 degrees cooler than a chamber with
beans, it would seem the pyrolysis contributes to the
bean's roast-chamber environment.  However there are
other factors to consider as someone previously
discussed - an empty chamber has the highest airflow
and no constriction to speak of relative to a full
chamber of expanding/expanded beans so it will cool
faster, consistent with a chamber temp 100 degrees
cooler than the same chamber with beans. The beans
tossing and tumbling in the chamber constrict the
airflow and make the exit path of air from the heating
element very complex. Heat BUILDUP is a given, I
think.  I think that we can draw a conclusion that
pyrolysis is contributing to the buildup in addition
to constricted airflow.  
That the pyrolysis contributes to the overall temp is
a given. How much will be difficult to determine.
However you can draw a conclusion from my observation
- stopping the roast at the "correct" [published]
temperature consistently resulted in a roast that was
too light and in which the body was not fully
developed. This would indicate that the INTERNAL bean
temperature was significantly LOWER than that measured
on the exterior of the tumbling beans as the roasting
process had not yet progressed to the visual and
olfactory cues. (I'm drawing new conclusions with each
batch roasted as the mechanics and chemistry of
roasting unfolds to me).
This is also consistent with my last espresso blend in
which each component was roasted at its "optimal"
[Tom's published] roast temp, but 2 of the components
never reached 2nd crack and while the espresso blend
pulled at about 20 seconds, 195 degrees and 15 bar
pump pressure produced excellent crema and was good
straight it petered out and became "lost" when used in
a latte' or cappucino.
There is a calibration factor involved but I don't
have enough data draw a conclusion. The exterior temp
appears to be higher than the internal bean temp and
consistently so.
Upon my observations the other night, it is about 40
degrees - i.e. "published" temp + 40 degrees =
thermometer temp at a given roast, but that needs more
data from additional batches of different coffees at
different degrees of roast to fully draw a conclusion.
I not doubting the accuracy of the reading on the
thermometer. I don't think I ever was (based on other
tests I've done and Tom and Maria's thorough approach
to quality that is, if the thermometers were bad they
wouldn't sell 'em!).  Now it's just a matter of more
data to draw the conclusion...for a Fresh Roast
roaster that is. It will obviously change with another
roaster brand owing to design differences.
Kevin
<Snip>
=====
--
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12) From: Rick Farris
Kevin wrote:
<Snip>
There are two ways to ensure consistency from roast-to-roast.  The first way
is to allow the roaster to cool off between roasts.  The other way is to try
to run your roasts as close together as possible.
Because I'm always doing about six roasts at a time, I go for the latter.
I've noticed from my logs that the first roast is about 20% and the second
roast is about 10% longer than subsequent roasts.
I can't say often enough that I get much better results if I do several
roasts of the same coffee in a row.  Recently I tried doing a couple of
roasts of several different coffees, and I didn't achieve nearly as good
results as when I stick to one coffee.  After three or four roasts, I
absolutely know when first crack is over, when second is about to begin, how
dark the beans will be at second, etc.
-- Rick
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13) From: Charlie Herlihy
--- Kevin DuPre  wrote:
<Snip>
 
Kevin, I really don't think that there is any great differance
between the actual internal and external bean temp. by the end
of a roast. Theoretically this could be measured, but I doubt
it's being done anywhere. Whatever your thermometer says when
you've found the right degree of roast you want-use that reading
and ignore whatever's been written by someone measuring bean
temps by a different method. Then, if you like, you can write an
article stating what you believe to be the correct bean temps
using your roaster and thermometer. Personally, I have three
thermometers that all give different readings of the roaster's
temp. but by now I know when to raise or lower my roasters temp
to get a perfect roast using them. After the beginning of second
crack I just care that it's below 425 degrees on all of them and
falling. I'm hoping to get a fluke thermocoupler for instant
bean temp readings so that I can can have someone take over for
me when I have to be away for a month because I expect it would
be less confusing, but I'll go by the readings it shows when the
smell of cookies almost ready to leave the oven starts(just
before first crack) and the readings it gives when first crack
stops, the readings at the first snaps of second crack, and so
forth to a nice Viennese.I'll write them down. If those readings
are the same as those given on a web site or roasting manual
then ,cool, but if not I sure won't worry about it. ;o) You
obviously care enough that you'll get it, and really, let us
know the temps that work with that thermometer and roaster
combo.  Saluditos,
Charlie 
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14) From: Ken Mary
The temperature reading you get is somewhere in the range of the hot gas and
the bean surface, including the "delay" in the thermometer sensor. If you
put the room temperature thermometer in ice water and time it until it
reaches 32F, you will get an idea of the response time. So the reading you
see is what actually happened that long ago.
There is no way to measure internal bean temperature. IMO "internal bean" is
a misprint in Davids' book, and should mean the bean environment
temperature. You can estimate the internal bean temp after the fact by
breaking one open to see the color of the interior.
--
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15) From: Jim Schulman
On 29 Aug 2002 at 19:07, Dan Bollinger wrote:
<Snip>
This sounds like a great technique. Thanks, Jim
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16) From: David Westebbe
On Wed, 28 Aug 2002, Kevin DuPre wrote:
<Snip>
I'm not so certain.  One reason fast roasts may taste different from slow
roasts is that the beans are not roasted all the way through to the same
degree of doneness.  My guess is that the surface temp in a fast hot roast
is greater than the core temp, like a thick steak cooked over hot coals.
If this is true, the core internal temp may be lower.
<Snip>
It seems counter-intuitive to me to assume otherwise.  If the beans throw
off heat from internal chemical reactions, the heat must either exit or
build up.  My guess is that both occur to some degree, based upon the
vewlocity of the airflow.  My thermistor-based digital thermometer maxes
out at 392, so I am unable to confirm that the temp jumps during first
crack.  Anybody with a better measurement device could attest to whether
the temp jumps quickly when the cracking commences.
<Snip>
I think you are on solid ground here.
<Snip>
Bean density and size, combined with the length of the roast are other
factors which may need to be accounted for.  I would think that at one
extreme, aged peaberries which are slooooowly increased in temp would have
much less difference, while big giant dense beans roasted in extreme high
heat would have significantly more.
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17) From: David Westebbe
On Thu, 29 Aug 2002, Ken Mary wrote:
<Snip>
But only if the temp differential is the same.  It may take 20 seconds to
change 50 degrees, but it will take only a fraction of a second to change
1 degree.
Then again, if I understand basic thermodynamics, the rate of transmission
of heat from a hot material to a colder one depends in part on the
differential.  That is why ice melts faster on a hot day.
Putting these two dynamics together, I don't think that
"ambient-to-freezing" is a good proxy for all possible response times.
But I ain't no engineer...
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18) From: Paul Goelz
<Snip>
Or use an infrared pyrometer.  Should work fine as long as you can get a 
clear shot of the beans direct and not through any glass.  I would love to 
see I/R used in a roaster, but I'm not sure how to deal with the smoke and 
deposits without an air purge and regular maintenance.
Paul
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19) From: Dan Bollinger
'Internal Bean Temp' is not a myth, but a processing goal.  Since roasting
is a thermo process, and that process takes place inside the bean, this is
the most important temperature in processing. This is what you want to
measure, or try to measure, All heating chamber temperature measurements are
really an attempt to discover what is going on inside the bean .  There are
some tricks to getting close.  Once you are close (and consistent) you can
calibrate the equipment and adjust for any differential.
You can get a feeling for the internal temp with this test:  During a roast,
at say 'rolling 2nd crack', pour the beans into a pre-warmed thermos bottle
with thermocouple.  Cap the bottle and watch the temperature reading.  It
should stop fluxuating soon.  When it does, this is going to be quite near
the internal bean temperature you had in the roasting chamber.  If you knew
the chamber's temperature during that 'rolling crack', then you could
calibrate your chamber measurements for internal bean temp.  Oh, and then
cool those beans quickly so you don't waste them!  Dan

20) From: R.N.Kyle
This is a multi-part message in MIME format.
I think the same as you on this David, I've always gone by sound site =
and smell, then I added a thermometer and found when my eyes, nose ears =
said the roast was right, the thermometer always said it was to hot. =
according to Tom's chart my thermometer is always about 40 degrees =
higher then the recommended roast temps.
Ron Kyle
a coffee roaster from South Carolina
rnkyle

21) From: Ed Needham
I doubt any of us has a sensing device sensitive enough to measure an
exothermic reaction in coffee beans as they roast.  What I have noticed as I
roast, is the need for less roaster heat as the bean mass becomes heat
saturated, and is no longer efficiently absorbing heat.  I would not call
that an endothermic reaction though, which by definition involves the organic
substance actually creating it's own heat as a result of internal chemical
reactions.  I'm not convinced a true endothermic reaction even occurs until
the beans reach 'near combustion' (shudder!).
(I'll add quite a few disclaimers here...not a scientist, not a chemist, not
a pyrolysis expert...blah, blah, blah...never done any experiments related to
endothermic or exothermic reactions...had to look up definitions to assure I
knew what they were)
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

22) From: EskWIRED
<Snip>
I'm not sure about that (and I hope that I'm understanding your point).  No
matter how much heat is present, it is transferred from a hotter material to
a cooler one, and once the cooler one reaches the higher temp, the heat
transfer stops.  If you had a huge block of stone, weighing several tons,
heated up to 100 degrees, you would have a huge amount of heat.  But a
kettle of water sitting on top would never exceed 100 degrees, no matter
what.  Even though there is plenty of heat in the stone block, it would
never ever cause the water to boil.  If one were to substitute a larger
kettle, it would "absorb more heat energy from the heating [stone]", but it
still would never exceed 100 degrees in temperature.
I think that what is happening is that the beans slow down the air, which in
turn does not carry so much heat out of the system, allowing the coils to
attain a higher temperature.  I think the real effect at work is that the
coils are not cooled to a lower temperature.
If one were to slow down the air in an empty popper using any method, such
as blocking the inlets or outlets with tape, or simply turning off the fan,
the temperature would rise in the coils, despite there being less "heat
energy", compared to a popper full of a mass of beans.
<Snip>
Again, I think the reason is different, and based solely on how quickly the
hot air is lost from the system.  If one were to put no beans, or a few
beans into a popper, almost all the air whooshes out the top and almost all
the heat is lost.  If one puts enough beans in to slow the air, the coils
reach a higher temperature quicker, and the beans attain a higher
temperature quicker.  But all other factors (like air velocity) being equal,
more beans equals more time.
Think about a popper so full of beans that the air escapes slowly.  The
beans on the bottom will get very hot, very fast. If the beans mix readily,
they all get hot.  But once you plug up the system with beans, adding more
will make the roast go slower (all other factors being equal).  More and
more and more beans will NOT make the roast faster, after a certain point.
The trick is to use the correct amount of beans, given the limiting factor,
whether that factor is airflow or BTU output from the coils.  Too few beans
will allow more heat loss, resulting in a slower temperature rise, but too
many beans will slow the roast as well, because the extra mass takes longer
to absorb the limited amount of BTUs.
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23) From: EskWIRED
<Snip>
Why do you think that the temperature rise during first crack is so slight?
I have no idea of how much or how little heat is produced via the chemical
reactions.
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24) From: Rick Farris
All your points were very logical, David, but they were based on a false
premise, namely that "once the cooler one reaches the higher temp, the heat
transfer stops."  You're implying that the air is reaching the temperature
of the heating element.  It isn't.  ;-)
-- Rick

25) From: EskWIRED
<Snip>
That's a very, very interesting point, and you're right, I did make that
assumption.  I need to think through the implications.
I suppose that the air will NEVER be as hot as the coils, except in a
closed, insulated system (which is pretty much the opposite of a system
which spews heat out the top under pressure, like a popper).
I wonder how much the moving air cools the coils, and what the coil temp is
at various air flow rates?  Has anybody ever used a thermocouple directly on
the coils?  Do they glow red with the fan on?  Or do they not get hot
enough?  Just out of curiosity, I might try running my popper without the
bean cup, in the dark, so I can see the coils, and whether they get red hot
or white hot or what, at various fan speeds.
<Snip>
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26) From: AlChemist John
Sometime around 20:02 9/5/02, EskWIRED typed:
<Snip>
It is not that we don't have a sensitive enough measuring device but that I 
doubt anyone has the data about exactly how much heat is being pumped into 
the roasting system and how much is being lost since none of these roasters 
are really insulated.
I believe it would take a bomb calorimeter to get this data. It would make 
for a  good high school of college project.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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27) From: Jim Schulman
On 6 Sep 2002 at 8:22, EskWIRED wrote:
<Snip>
I've never measured the coils themselves. But on my FR at normal 
voltage, the air coming off the coils is at 510F. In an empty roaster, 
it drops to 460F an inch up, and is down to 370 at the top of the 
chamber, even after its fully heated. Once a load of beans have passed 
the first crack, they're above 400F, putting out heat themselves, and 
slowing down the airflow, so the top of the chamber gets up into the 
mid 400s too.
I've been thinking about using two temperature sensors, one at the 
bottom and one at the top of the chamber, and seeing if the temperature 
difference may be a more accurate way of inferring what the beans are 
doing than a contact probe. But it hasn't amounted to anything yet.
Jim
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28) From: EskWIRED
<Snip>
Interesting thought.  It's also interesting that the air cools down so much,
so quickly, from traveling from the bottom of the chamber to the top.
I wonder how much of a role radiant and conductive heat from the hot metal
bean cup plays in the process of heating up the beans?
I've really gotta get a TC.  My thermistor-based Polder doesn't cut it at
the temps we're discussing.  It tops out at 392 degrees.
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29) From: Ben Treichel
Jim Schulman wrote:
<Snip>
Presuming that the chamber isn't leaking hot air (pretty safe) and 
ignoring conduction and radiation (maybe 10% or more - but constant in a 
warm system) you should be able to see the heat transfer into the beans 
over time because of the temperture differences. After that, you will 
have to look at the data and see if there is some meaning to it.
Ben
<Snip>
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30) From: Ed Needham
As I said in the same post, to a point, the bean mass absorbs heat, and the
temperature rise (with the same heat input) is slow.  At a point near first
crack, the bean mass is at or near equilibrium with the output temperature
and are not able to absorb as much heat, then the measured heat begins to
rise.  Cutting back on the heat allows the roasting temp to remain stable (or
lower, as some prefer).  I am not convinced that an exothermic reaction even
takes place under normal roasting conditions, assuming that point would be
the actual beginning of combustion.  Maybe a more refined definition of
'exothermic' would prove me wrong, but as I understand it, the beans actually
have to begin 'generating' heat to be considered exothermic, and I don't
think that happens.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

31) From: Cathy M.
Ed Needham wrote:
<Snip>
I agree with that Ed.  There are very few truly exothermic chemical reactions
yielding edible results that I can imagine.  The beans absorb heat until first
crack which is the point that the bean's internal and external temperature are
equal, and the bean is unable to act as a heat sink any longer without
alteration to it's physical composition - hence the "crack". When the beans
become "saturated with heat" the external heat, if applied at the same constant
rate, will cause a rapid rise in external temperature - perhaps giving the false
impression of a sudden exothermic activity.  I find, even in the wok, that
backing off the heat a bit, to slow down the first crack, then backing off quite
a bit between the end of first crack and the beginning of second, produces a
roast with better body and a richer flavor than using the FR+ in its normal
cycle.  Also there is almost no "scorching" of the beans if adequate agitation
is provided.
-- 
Regards, Cathy
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32) From: Ken Mary
Read Illy and Viani, "Espresso Coffee..." page 88. I believe the authors 
know more than all of us put together.
--
----------
<Snip>
<Snip>
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33) From: EskWIRED
<Snip>
Ed Needham wrote:
<Snip>
I am not convinced that an
<Snip>
<Snip>
According to Coffee Research.org:
------
The second step, often called the first crack, occurs at approximately 205
?C (400 ?F) in which the bean doubles in size, becomes a light brown color,
and experiences a weight loss of approximately 5%.  The corresponding Agtron
number for this color is between 95-90 (Davids, 68-69).
In the next step the temperature rises from 205 ?C to approximately 220 ?C,
the color changes from light brown to medium brown (Agtron # 60-50), and a
weight loss of approximately 13% occurs (Davids, 68-69).  The resulting
chemical process is called pyrolysis and is characterized by a change in the
chemical composition of the bean as well as a release of CO2.
The second step is followed by a short endothermic period which is followed
by another exothermic step called the second crack.  This second pyrolysis
occurs between 225-230?C, and the roast color is defined as medium-dark
brown (Agtron #50-45) (Davids, 68-69).  The second pop is much quicker
sounding and the beans take on an oily sheen.http://www.coffeeresearch.org/espresso/roasting.htm----------
I have no real personal knowledge, nor do I know anything about organic
chemistry..
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34) From: Andrew Thomas
--- "EskWIRED"  wrote:
<Snip>
I can see the coil glowing through the vents in my Poppery (Mk 1) as I preheat before the first roast of each session.   Andy
Free e-mail!  you
A service of www.WallaWallaGuide.com
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35) From: Cathy M.
John Abbott wrote:
<Snip>
About 1/2 lb produces the best results in my small 13 inch wok, which is made of
very heavy gauge anodized aluminum (at least 3/16 in thick).  I have done 3/4
lb, but I don't think the roast was as well controlled. 1 cup of greens is a
good way to start.
-- 
For the conservation of the Tibetan Lhasa Apso,
Regards, Cathy http://lists.sweetmarias.com/mailman/listinfo/homeroast">http://www.lhasa-apso.orghomeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

36) From: Rick Farris
And also consider that most of the air doesn't even *touch* the heating
coil...  :-)
-- Rick

37) From: Ed Needham
I have no doubt that they are both very intelligent and informed men.  They
also put their pants on the same way I do, and can make assumptions and
errors the same way I do.  I rarely put anyone on a pedestal quite as high as
where you infer these men should be, although, sometimes I'm arrogant like
that.  My guess is that, although both are very highly respected as coffee
and roasting experts, either of these men could probably learn something
useful on this homeroast list from time to time.  We are not a group of
uninformed, uneducated or unscientific bumblers, but rather those at the top
of the consumer ranks, which sometimes puts us above many commercial folk.
We are represented here with doctors, lawyers, and a ton of technical people
who know their way around controls, chips, scientific method and coffee.  I
don't think we should underestimate ourselves.  I think some of the greatest
brains in coffee reside on alt.coffee and this homeroast list.
BTW...What does page 88 say? 
Ed Needhamhttp://www.homeroaster.comed
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**********************************************

38) From: Ed Needham
Definitions
Pyrolysis
Webster's:  py.rol.y.sis  n : chemical change caused by the action of heat
(c)2000 Zane Publishing, Inc. and Merriam-Webster, Incorporated.  All rights
reserved.
**********************
*pyrolysis-- the second stage of ignition during which energy causes gas
molecules given off by a heated solid fuel to vibrate and break into pieces.
**********************
*Pyrolysis-- is the process in which organic substances are reduced by
subjecting a material to heat in a reduced oxygen environment. This process
has also been referred to by other terms, such as thermal distillation or
retort conversion.
*********************
*oxidation-- the loss of one or more electrons by an atom, molecule, or ion.
**********************
*exo.ther.mic-- adj : characterized by or formed with evolution of heat
(c)2000 Zane Publishing, Inc. and Merriam-Webster, Incorporated.  All rights
reserved.
**********************
*en.do.ther.mic-- adj : characterized by or formed with absorption of heat
(c)2000 Zane Publishing, Inc. and Merriam-Webster, Incorporated.  All rights
reserved.
Of course Webster's is a very general and lacks detail.  Other definitions
say that true pyrolysis needs to occur in an oxygen free or almost oxygen
free environment.  So even the term pyrolysis may not be what we want to use
as a descriptor for roasting.
Endo and Exo thermic seemed fairly consistent in the definitions I
saw...'Endo' meaning heat absorption, and 'Exo' meaning creation of heat.
Fairly simple. (I think)
One question I have about an exothermic reaction is... What if the heat
source is removed or reduced?   Is the stored heat that radiates out
considered exothermic?
The way I understand it is like this... A log on a fire is endothermic
(absorbing heat) until the chemicals within the log begin a reaction to form
more heat than is being absorbed.  At such a time, exterior heat can be
removed and the log continues to put off heat above and beyond what it had
already absorbed due to combustion (exothermic).  It would continue to put
off heat 'on it's own' until the chemical reactions are spent.  Clearing up
the definition would be helpful.
An interesting article referenced by coffeeresearch.org on the Sweetmaria's
site leads me to believe that exothermic may refer to any radiated heat, and
not created heat.http://www.sweetmarias.com/roast.carlstaub.htmlAll of that aside, the problem, as I see it is that one 'authority' uses a
term, and everyone jumps on it and assumes it is correct, tested, and
generally treat it as 'gospel'.  It may, in fact just be opinion.  Maybe a
good opinion, but it also could be flat out wrong.  I'm not a scientist in
the field of thermodynamics, but I don't think it's wrong to challenge coffee
'authorities' from time to time when something doesn't make sense.
I wonder what research supports the assertions 'coffeeresearch.org' has
boldly stated as fact in that quote?  None are given.  I bet it's just
opinion, or based on someone else's expert opinion.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

39) From: Ken Mary
Page 88 cannot really say anything, being an inanimate object.    8^)
It describes the roast process as going through endothermic and exothermic
phases. I thought this was common knowledge.
Chemical reactions almost always either generate heat or consume heat. As we
proceed along the roast curve, we may find that some reaction consumes heat,
therefore in order to maintain the proper rise in temperature, we must add
more heat by increasing the temperature of the hot air or drum, and vice
versa. The amount of this heat corresponds directly to the amount of
chemical substance reacted. In a particular time interval there may be both
endo and exo reactions occurring, so what we see is the net result.
I believe those people with credentials do know more about their particular
field of endeavor than we (in general) do. However, that is not proof that
what they say is correct without corroboration from others. In many cases
where I have the expertise to do so, I will try to determine the truth for
myself. If some of us had access to the necessary lab equipment, I am sure
we could determine the facts of the matter as did Illy and Viani.
--
----------
<Snip>
<Snip>
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40) From: Dan Bollinger
Please, enlighten us!
<Snip>
the
<Snip>
first
<Snip>
temperature
<Snip>
to
<Snip>
stable (or
<Snip>
even
<Snip>
be
<Snip>
actually
<Snip>
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41) From: Angelo
Ed,
I have to agree with you on this one... Many great inventions came from 
non-experts in the field. Remember those bicycle repairmen?
It's the experts who can't seem to come up with a satisfactory home 
roaster. Maybe, if they would incorporate some of the ideas proffered by 
those on this list, we would all be using a "set it/forget" it roaster...
I don't  trust "experts", self-proclaimed or otherwise....As a matter of 
fact, when I hear that appellation, my critical antennae go up , 
immediately...Call me suspicious, if you wish. :-)
A-
<Snip>
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42) From: Ed Needham
I think defining these terms and understanding what specific substances do
within the bean at various temperatures, and how they interact with each
other can help us define roast profiles and get us better roasts.  The
article I mentioned on the Sweetmaria's web site mentions making sure the
ramp up to first crack does not allow the beans to exotherm by reducing the
heat too much and allowing the beans to put off heat.  His reason was that
this causes desirable interactions among chemicals to go haywire and interact
incorrectly with the wrong substances.http://www.sweetmarias.com/roast.carlstaub.htmlThere is a lot in this article, and if it is true, we have quite a bit of
calculating and discussion ahead of us to use this information for improving
our roasts.  Any comments or insights on what you read there?
I think a timeline of chemical reactions of the top ten substances, comparing
them and how they interact would be a start.  Anyone with a project manager
software package that can do timeline comparisons?
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

43) From: Ed Needham
Illy does have a sophisticated lab.  They showed part of it on a TV special a
few months ago on the 'Food Network', if I remember correctly.  I have yet to
see research though proving an exothermic reaction in the roasting process.
He says it happens.  He may be right.  Maybe it's out there, or maybe it's a
carefully guarded part of the R&D research of Illy or some other huge
roasting operation (Folgers?).
I'd love to get into the nuts and bolts of the chemistry of roasting.  Maybe
some of us can take this on a project for the benefit of the homeroast group.
I can also post interesting information on my web site if we dig up anything
new.  Do a well constructed write up, and I'll throw it up there for the
benefit of homeroasters.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

44) From: Jim Schulman
On 7 Sep 2002 at 14:56, Ed Needham wrote:
<Snip>
The article you referenced in your previous post contains this"
<Snip>
If I can make out the content in the somewhat overblown "US-Tech-Exec" style, he's either 
saying the beans loose heat if the ambient temp drops below 400, or become chemically 
exothermic. It seems the first, exotherm being used as bogus greek for "give off heat", since 
I'm unfamiliar with any reaction that becomes exothermic as triggering temperatures drop. Of 
course, if anyone lights fires by putting the logs in the freezer, I'd love to hear about it.
Anyway, does this odd turn of phrase explain all instances of people taking about exothermic 
roasts?
Jim
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45) From: Ed Needham
My point exactly, Jim.  The terms pyrolysis, exotherm, endotherm seem to be
tossed around in a general way, not paying attention to the accurate
definitions of those terms.  I saw that and posted concerning my question
about an accurate definition of the term exotherm, and whether it encompasses
putting off stored heat (I think not).  What he said in the article was part
of the stimulus for my post.  I don't think the roasting process gets to the
point of 'exotherm' reactions.  I'd like to see proof otherwise (and not just
comments from published 'authorities'.  Hard research.  I don't think it's
there.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

46) From: Jim Schulman
My TC is a dual channel model. I'll run a few roasts, hold the inflow temp 
(bottom of the FR) constant after the 1st crack starts, and see if the outflow 
(top of the FR) ever goes higher. If it does, it would prove that a true 
exothermic reaction is happening. If it doesn't, it won't prove anything either 
way.
On 7 Sep 2002 at 19:03, Ed Needham wrote:
<Snip>
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47) From: Ed Needham
I think usage of the word in the SM article is just incorrect.  Endotherm and
endothermic have got to be the same thing, or I need to go back to basic
English language class.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

48) From: Jim Schulman
On 8 Sep 2002 at 19:42, Dan Bollinger wrote:
<Snip>
If anyone has one lying around, I'll gladly let them do the test. 
Although I'm skeptical about actual exothermy in the roast, I do know that one 
really has to brake the heat very hard at the first crack onset to slow the 
roast down after that point. So from a profiling point of view, it feels like 
the roast is self heating and running out of control.
I have a feeling that Blackbear's observation that the bean's moisture and 
ability to absorb excess heat really falls off at this point may be a better 
account for this roasting observation. That certainly squares better with the 
way other vegetable foodstuffs suddenly start to brown rapidly and scorch 
after they dry out enough in an oven or pan.
Jim
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49) From: Rick Farris
Ed wrote:
<Snip>
I agree with you, Ed, and let's not forget that those published
"authorities" are *coffee* authorities, not people with PhDs in
thermodynamics.  In the field of thermodynamics they may be no more
educated/experienced than many on this list.
-- Rick
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50) From: Rick Farris
Jim wrote:
<Snip>
I don't think that's true, Jim.  I'll have to think about it a little bit,
but let's not mistake "heat energy" and "temperature."
Hmm.  I still can't figure it out.  I think I'd have to make some drawings
and write some equations...
-- Rick
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51) From: Ryuji Suzuki -- JF7WEX
From: "Ed Needham" 
Subject: Re: +Re: thermometer differential question
Date: Sat, 7 Sep 2002 19:03:10 -0400
<Snip>
Whether roasted bean goes through processes that result in overall
release of heat at some moment is a question that needs to be
tested. Logically speaking if it is exothermic even a tiny bit, it is
exothermic. But I agree in the sense that even if it is exothermic for
a brief moment it won't be anything significant, as I kept saying in
this list in the past. If you need to lower the heat it is probably
for different reasons.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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52) From: Jim Schulman
On 7 Sep 2002 at 21:56, Rick Farris wrote:
<Snip>
If the inflow temperature is constant or rising, and the outflow temperature rises 
above the inflow temperature, the beanmass must be warmer than both, that is warmer 
than the inflow temperature ever was. So some chemical heat source must be in play. 
If I had previously dropped the inflow temp, it would of course prove nothing that 
the outflow was higher (except that heat is stored).
Of course, I could be wrong (or the TC insulation could be burning)
Jim
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53) From: Rick Farris
Jim wrote:
<Snip>
I guess I'm thinking of a voltage doubler, with voltage corresponding to
temperature and heat energy corresponding to current flow.
In other words, I know that it is possible to make a higher voltage without
a generator, but I can't figure out how to carry the analogy through with
heat/temperature.
-- Rick
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54) From: Ryuji Suzuki -- JF7WEX
From: "Ed Needham" 
Subject: Re: +Re: thermometer differential question
Date: Sat, 7 Sep 2002 14:23:26 -0400
<Snip>
[...]
<Snip>
I will narrow to the point related to browning of sugar.
Browning of nearly pure sugars, as they say, initially require
relatively high heat into the reaction, and it tends to continue by
itself for some time. Combustion is obviously one form of exothermic
reaction and one popular demonstration for college chemistry is
combustion of sugar cubes. Right, we all know it will burn. If we burn
sucrose, what we get is not the same as browned sugar, which consists
of hundreds of substances many of which we don't quite understand yet.
One important thing missing in that article is that "how" sugar is
stored in coffee beans. If many sucrose molecules are packed tightly
in absence of impurities then we need to worry about getting into
browning process that is so quick that it goes out of control. If on
the other hand sugar is suspended in different substances that are
relatively stable in the range of temperature where sugar gets brown,
then we have much better control of the browning process by raising
the temperature evenly and slowly. Indeed coffee bean is full of
moisture and cellulose so sugar shouldn't get burnt out in the way
they are warning about.
When they say how many per cents of bean is sugar, they grind up the
bean and do the assay. Instead, we need a thin (tens of microns) slice
of dry bean which is then selectively stained for sugar or other
substances that indicate the presence of sugar and examine such
preparations under microscope. Have you seen one of those pictures?
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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55) From: Ryuji Suzuki -- JF7WEX
From: "Rick Farris" 
Subject: RE: +Re: thermometer differential question
Date: Sat, 7 Sep 2002 22:53:59 -0700
<Snip>
There won't be exact analogy because voltage is exerted between points
(or against reference point) not one point.
However, adiabatic (isentropic is the preferred term though)
compression will raise temperature with non-heat work input.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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56) From: Jim Schulman
On 7 Sep 2002 at 22:53, Rick Farris wrote:
<Snip>
Like in a heatpump/ac? -- compress the air, and the temperature rises -- but even 
if the air outlet gets partially blocked by chaff, the the inlet temperature sensor 
is downstream of the fan, so it would also register the rise.
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57) From: Dan Bollinger
Ed,  I think you've nailed down endo- and exothermic definitions.  As I
understand it, pyrolysis is any decompostion due to heat.  It can be endo-
or exothermic.
Your log analogy is a good one, but lacks an important, small area.  There
is a point at the beginning of the exothermic phase, while the log is still
being heated with an outside heat source, where, if the heat source was
removed, the exothermic reaction ceases.  In other words, the log burning
stalls. This is important, I think, our goal here isn't to burn coffee
beans, but to roast them. ;)
Wood is a good substance to use as an analogy since it share a lot of the
same chemicals as a coffee bean does, cellulose and organic volatiles. A
better wood analogy might be woodburning.  If you take a heated branding
iron to wood, it causes pyrolysis at different stages depending on the
amount and temperature of heat applied.
1.If you take a moderately heated branding iron to wood volatiles are
evaporated but it doesn't leave much of a mark. (endothermic)
2. If you take a not-quite-glowing heated branding iron to wood it leaves a
'full-city' brown mark, but when the iron is removed the wood does not
continue to burn.  (non-sustainable exothermic)
3. If you take a white-hot iron to wood it immediately bursts into flames,
and when you remove the iron it continues to burn. (sustainable exothermic)
To me, #2 is our goal in roasting. The wood enters an exothermic reaction
phase, but is not producing enough heat to sustain the reaction when the
iron is removed. I don't have any proof of this, I'm just making an
observation based on comparing two similar experiences and knowing that some
subtances burn (are exothermic) but only in the constant presence of a
flame.
Dan
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58) From: EskWIRED
<Snip>
<Snip>
I thought his method was sound.  I think he needs to bring the heat source
to a temp just short of first crack, and then hold it there until the beans
are stable at that temp.
Once they are there, he can raise the heat source to a higher temp., and
stabilize it.  The beans will gain heat, and rise in temperature.  If they
exceed the input temp while cracking, they are producing their own heat.
Unless they themselves produce heat, they cannot exceed the input
temperature.
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59) From: EskWIRED
<Snip>
The critical point is that heat is transferred only from a hotter
temperature material to a cooler one.  If the beans are hotter than the air
ever was, then the air is not responsible for their higher temperature.  If
his results confirm that the beans are hotter than the air, we can conclude
that an exothermic reaction is taking place inside the beans, or that
another component of the system is hotter than the air.
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60) From: Jeffrey A. Bertoia
Dan Bollinger wrote:
<Snip>
Dan
You can't double electricity...  But you can double voltage as you describe.
Analogously you can double temperature (in our situation) in much the 
same way.
Since the heating element is much hotter than the ambient air and even 
much hotter than
the output air, we simply reduce the air flow for a higher temperature.
This is actually almost exactly the same as doubling voltage in a 
transformer since the
current capability is then halved.
In other words it's not heat that is analogous with voltage it's 
temperature.
jeff
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61) From: Ed Needham
It's about time you chimed in.  Where have you been?  Did you ask permission
to take a vacation from the list? 
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

62) From: DJ Garcia
For what it's worth, from a Google search, apparently taken from A
Dictionary of Science, Oxford University Press, (c) Market House Books =
Ltd
1999:
endotherm (homoiotherm)   
An animal that can generate and maintain heat within its body =
independently
of the environmental temperature. Mammals and birds are endotherms; they =
are
often described as being warm-blooded. See homoiothermy
 . Compare ectotherm =
 ;
heterotherm  .
Cheers!
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63) From: dewardh
Jim:
<Snip>
onset to slow the
roast down after that point. So from a profiling point of view, it feels like
the roast is self heating
Well, that certainly *sounds* "exothermic" . . . temperature rise independent 
of external heat input.  And it's the reasonable interpretation of the 
"calorimetric roasting curve" on page 89 of the oft mentioned book by Illy and 
Viani.  The quick release of energy associated with the "cracks" is one clue . 
.. . the evolution of CO2 (which indicates a chemical reaction of some 
significance is occurring) is another.  The cracks are not "steam explosions" 
(as with popcorn), but are pretty clear evidence of an exothermic chemical 
reaction (brought to its activation temperature by externally applied heat).
I'm finding myself in general agreement, btw, with your observation that 
extending the time between first and second crack improves "body" and produces 
a generally better cup (at the expense, perhaps, of some "brightness"), and 
that it is necessary to substantially reduce heat input early in the first 
crack to accomplish the delay in the second (confirmation of the exothermic 
nature of the first crack at least).
Deward Hastings
Ps.  > foodstuffs suddenly start to brown rapidly and scorch after they dry out 
enough
It's not the drying that does it . . . it's reaching the activation temperature 
of the Maillard reactions responsible for browning.  Reaching that temperature 
is delayed by the heat loss from water evaporation (which is why there is a 
connection with drying).
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64) From: dewardh
Ryuji:
<Snip>
Yes.
<Snip>
a brief moment it won't be anything significant
The "cracks" and CO2 evolution are not "significant"?
Deward
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65) From: dewardh
Ryuji:
<Snip>
But with roasting coffee we are not talking about the "browning of sugar".  We 
are talking about (to quote Illy):
"Free amino acids, peptides and proteins with free amino groups, react with 
reducing sugars to form glycosylamines and/or aminoaldoses and/or aminoketones 
by condensation".
In other words, the Maillard reaction . . .
Deward
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66) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +Re: thermometer differential question
Date: Sun, 08 Sep 2002 11:22:38 -0700
<Snip>
How do you know CO2 and cracks are exclusively attributable to the
exothermic process?
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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67) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +Re: thermometer differential question
Date: Sun, 08 Sep 2002 11:30:27 -0700
<Snip>
<Snip>
<Snip>
That article on the SM web page (which Ed mentioned) discusses
exothermic stuff in relation to the heat related reaction of sugar and
does not link to amino acids and proteins. That is the same thing as
browning of sugar.
If you still think your quote is appropriate, I would like to know how
you know any of the reactions between sugar and amino acids, in
protein or liberated forms is exothermic enough to drive the whole
roasting process exothermic for any brief moment.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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68) From: Ryuji Suzuki -- JF7WEX
From: "Ed Needham" 
Subject: Re: +Re: thermometer differential question
Date: Sun, 8 Sep 2002 12:26:08 -0400
<Snip>
What makes you think that I wasn't silently improving my Turbo Crazy
design? After my repeated experiments and challange to bigger batch
size my Stir Crazy is getting old quickly... need to find a replacing
technique.
# My summer tea season is almost over... but at the same time I found
  an excellent green tea from Yunnan (deep China) this season.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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69) From: dewardh
Ryuji:
<Snip>
exothermic process?
CO2 is the most fully oxidised state of carbon.  How do you get there (from 
less oxidised carbohydrates) without an exothermic reaction?  Calorimetric data 
shows a sudden increase in heat at the time of the cracks.  What source do you 
propose for this heat if not exothermic chemistry?
Deward
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70) From: Ryuji Suzuki -- JF7WEX
From: "Dan Bollinger" 
Subject: Re: +Re: thermometer differential question
Date: Mon, 9 Sep 2002 07:36:30 -0500
<Snip>
First of all, patents do not make any judgment about its feasibility
or technical or scientific correctness. Patent in general is filled
with B.S.
<Snip>
[...]
<Snip>
Acceleration of time-temperature curve's steepness does not mean that
the bean is releasing heat. It includes the possibility that bean does
not require as much heat to raise unit temperature above 400F compared
to below that line. Assuming what is stated in the quote above is
true, in order to arrive at exothermic conclusion, you must further
exclude this possibility.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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71) From: dewardh
Ryuji:
<Snip>
exothermic stuff in relation to the heat related reaction of sugar and
does not link to amino acids and proteins. That is the same thing as
browning of sugar.
The carmelization of sugars may or may not be exothermic . . . I don't know. 
 The oxidation of sugars, either directly with O2 (combustion) or the partial 
oxidation of the Maillard reaction, is exothermic.
<Snip>
you know any of the reactions between sugar and amino acids, in
protein or liberated forms is exothermic enough to drive the whole
roasting process exothermic for any brief moment.
It certainly is appropriate . . . (unless you wish to claim that no Maillard 
reaction or other oxidative reaction is occurring),  Each step in the oxidation 
of carbon is exothermic.  Do you have a non-exothermic reaction that produces 
CO2 from carbohydrates in mind ? ? ?
Deward
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72) From: Dan Bollinger
<Snip>
I assume that the curve is true.  Sivetz has roasted more beans with
thermocouples and chart recorders hooked up than all of us combined.  I will
agree that it neither proves nor disproves an exothermic reaction during
roasting.  Dan
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73) From: dewardh
Ryuji:
<Snip>
the bean is releasing heat. It includes the possibility that bean does
not require as much heat to raise unit temperature above 400F compared
to below that line. Assuming what is stated in the quote above is
true, in order to arrive at exothermic conclusion, you must further
exclude this possibility.
Since it is you making the extraordinary claim (that the specific heat of 
coffee beans changes dramatically at 400F) the burden of proof rests with you . 
.. .
Deward
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74) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +Re: thermometer differential question
Date: Sun, 08 Sep 2002 12:28:41 -0700
<Snip>
<Snip>
I am afraid this does not answer my question.
<Snip>
The roaster is putting the heat in. How much of it is used in various
reactions in the course of roasting must be investigated first.
<Snip>
<Snip>
  Maillard reaction or other oxidative reaction is occurring), Each
  step in the oxidation of carbon is exothermic.  Do you have a
  non-exothermic reaction that produces CO2 from carbohydrates in mind
  ? ? ?
You are changing the point of focus from the overall roast to specific
one reacion which may be one of many other reactions going on during
roasting.
Oxidation of carbohydrates itself is exothermic but varies greatly in
efficiency depending on the path of actual reaction and since we are
talking about the roasting process as a whole we cannot just take
carbohydrate oxidations and conclude roasting is exothermic.
My point throughout is that you can't say "first crack is exothermic
reaction" without further evidences. All I saw so far is quotes from
authorities and "hopeful" explanations. I am also saying it doesn't
matter whether it is endothermic or otherwise. Even if the roast
reaction is indeed exothermic, we still need to push in some heat as
activation energy to continue the reaction if the exothermic reaction
in question is not efficient enough to provide activation energy of
subsequent reactions, which is likely.
Reduced need of heat input is a different question. It simply means
reduction of heat necessary to increase unit temperature no matter
what the underlying mechanisms are.  How do you roast differently if
the roasting is indeed slightly exothermic for a moment? It would make
negligible difference unless you are roasting a huge quantity in a
well insulated chamber with a heater that is capable of very high heat
flow. This is because as the chamber temperature increases, so does is
the temperature difference from ambient air and therefore heat leaking
out of the chamber also increases. Since the chamber wall and
surrounding air has some heat capacity it would make little difference
overall.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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75) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +Re: thermometer differential question
Date: Sun, 08 Sep 2002 13:14:18 -0700
<Snip>
<Snip>
I am not making extraordinary claim. I am simply pointing out logical
possibilities and also pointing out there are holes in some of the
popular theories around here.
I am also not narrowing down to reduced specific heat in the way I
said above if you read carefully. The way I said includes the
possibility of cessation of other endothermic reactions at about 400F.
Making assertive statement based on partial facts and hopeful theories
is what I object. Especially because it doesn't affect how
homeroasting devices should work in practice.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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76) From: Dan Bollinger
<Snip>
Maillard
<Snip>
oxidation
<Snip>
produces
<Snip>
Well I'm curious as hell what is going on inside my beans.  Here's a few
things I found online. Either everyone is misquoting a common misconception
(a good possibility), or coffee roasting is indeed exothermic as some point.
I've added their URL below the quotes. Dan
"Green Mountain Coffee Roasters... had been experiencing several [power
outages] a month... Safety was also a priority, because the roasting process
has an exothermic stage and can be a fire threat if the machinery shuts
down."http://www.northernpower.com/pages/sub3_gmcr.html"In addition, two distinct cracking sounds can be heard from the coffee
roasting drum as dark roasted coffee passes through phases of the roasting
process: the first as moisture inside the bean cracks open the center of the
bean; and the second as an exothermic reaction within the bean creates tiny
explosions of gas and hot oil."http://www.abettercup.com/Coffee_Roasting.aspSTAGES OF ROASTING:
FIRST STAGE
Also known as the Endothermic stage during which the green beans begin to
slowly yellow and begin to smell like toast.
SECOND STAGE
This is referred to as the 'First Crack'.   At this stage, at approximately
375o F, the beans will actually double in  size while losing about 5% of
total weight loss.   The coffee beans will be a light brown in color; as the
temperature rises the bean color darkens to a medium brown and loses about
13% of their weight.   A chemical change in the composition, known as
pyrolysis, results as well as the release of CO2.
THIRD STAGE
A 'Second Crack' , or the exothermic stage, occurs when the temperature
reaches about 410o F.   The coffee beans at this point the oils within the
coffee bean begin to surface.  Roasting much further into this stage can
strip away the aromatic compounds of the coffee.http://www.strawhousecoffee.com/aboutcoff.htm"As the roast nears completion, strong exothermic reaction produce a rapid
rise in temperature, usually accompanied by a sudden expansion, or puffing
of the beans, with a volume increase of 50-100%."http://lists.sweetmarias.com/mailman/listinfo/homeroast">http://www.ensia.inra.fr/~courtois/fidel/Lisbon/flaves/sec3/coffee.htmlhomeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

77) From: dewardh
Dan:
<Snip>
Certainly a reasonable assumption, since it agrees with the curves provided by 
Illy.  Buth are in general agreement that it is not until the bean is dry 
enough ( the end of the "drying phase") that the bean temperature reaches the 
point where the changes in chemistry that we call "roasting" occur . . . first 
crack and beyond.  Illy devotes 20 pages of "Espresso Coffee" specifically to 
those chemical changes.
It all supports Jim's observation that the rate of heating before first crack 
is (relatively) unimportant, and that it is control of the roast in the "active 
chemistry" phase (first crack to end point) that makes the most difference in 
the end result.
Deward
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78) From: dewardh
Ryuji:
<Snip>
reaction" without further evidences. All I saw so far is quotes from
authorities and "hopeful" explanations.
Am I correct in concluding that you have not yet read "Espresso Coffee", by 
Illy and Viani?
Deward
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79) From: R.N.Kyle
This is a multi-part message in MIME format.
This is one heck of a discussions, getting as good as the vacuum =
sealing. I'm not a scientist on in that sense a highly educated man, but =
I do pay attention to things as they occur. I found in my limited =
experience, that the beginning of 1st. crack about 400 degrees ( with my =
thermometer) if I introduce a cooling by cutting the heater off the bean =
temps go down fairly quick, but somewhere in the middle to the end of =
1st crack say about 425 degrees I can introduce cooling and the roast =
does not drop it takes about 3 times as long to drop If I cut the heater =
off ( usually 3 sec) it will stay at 425 to 430 until the 1st crack is =
complete, when I see it start to drop when I cut the heat off I let it =
drop to 400 and cut the heat back on and let it go on to 2nd. crack.
Therefore somewhere between the middle of 1st crack and continuing to =
the end of 1st crack there seems that the beans begin to produce there =
own heat. 
Is this exothermic I have no idea, I just know what I see.
Ron Kyle
a coffee roaster from South Carolina
rnkyle

80) From: dewardh
<Snip>
possibility of cessation of other endothermic reactions at about 400F.
I have not yet seen your proposed endothermic reactions which ends abruptly at 
400F . . . (or any explanation of why the ending of such reactions would 
produce CO2 or the "first crack").
<Snip>
is what I object.
Well, yes, so, what are you doing?
<Snip>
homeroasting devices should work in practice.
But it does.  It has a lot to do with managing roast profiles, and deciding 
when and how to modify heat input.  It is, granted, a long way from stirring 
beans in a wok, or turning a drum over a wood fire, but for those experimenting 
with roast profiles in an air roaster capable of fine control of heat input 
understanding what's going on can matter.  Many of us have wondered about the 
strange roast profiles of small drum roasters like Alpenrost and Hot Top, and 
why they spend so much time drying the beans and so little in the actual roast 
phase (first to second crack).  Their inability to rapidly change heat input 
(roaster internal temperature), combined with the heat input from the 
(exothermic ) first crack, explains the relatively short time between first 
and second crack in such machines, and suggests that users of those machines 
may find it more difficult to control roast profile than users of the more 
responsive air machines.
Deward
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81) From: dewardh
Ron:
<Snip>
degrees ( with my thermometer) if I introduce a cooling by cutting the heater 
off the bean temps go down fairly quick, but somewhere in the middle to the end 
of 1st crack say about 425 degrees I can introduce cooling and the roast does 
not drop it takes about 3 times as long to drop If I cut the heater off ( 
usually 3 sec) it will stay at 425 to 430 until the 1st crack is complete, when 
I see it start to drop when I cut the heat off I let it drop to 400 and cut the 
heat back on and let it go on to 2nd. crack.
Therefore somewhere between the middle of 1st crack and continuing to the end 
of 1st crack there seems that the beans begin to produce there own heat.
Is this exothermic
You've given about as good a description of the effect of an exothermic first 
crack as we are likely to see (apart from the fully instrumented experiments of 
Illy and Seivetz).
Deward
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82) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +Re: thermometer differential question
Date: Sun, 08 Sep 2002 14:10:28 -0700
<Snip>
<Snip>
Here's one possibility:
Bean moisture is not zero even if you roast very dark. At the point of
first crack, there's still significant amount of moisture left in the
bean, but at this temperature it must be tightly enclosed in rather
rigid structure. At first crack this stress may lead to local
destruction of cellulose matrix that was not preiously
compromised. This leads to crack.
This crack may be partially initiated by heat released by sugar
reaction. If you roast very slowly up to the point where you expect
first crack, the first crack will be much muted in loudness, widely
distributed in time, and high in pitch, somewhat similar to second
crack in more normal roasting profile. It also accompanies with darker
than usual appearance for the given temperature.  If you ignore
everything but cellulose matrix, moisture, sugar reaction (including
amino acids and proteins) from the model, this pre-first-crack
influence to the crack suggests that sugar reaction itself is not
spontaneous, or not exothermic enough overall to provide the
activation energy for its own subsequent reaction and other
surrounding reactions.  That is, the roast relies on external heat as
its activation energy.
In the process above, building up mechanical stress and release of
some moisture as vapor through cracks require heat input. However,
until the cellulose builds up further stress with this moisture
reduced beans, it will not require as much heat as before.
I am not claiming this is true. This is just one plausible alternative
hypothesis, as yuo requested. I have previously mentioned that slower
ramp leads to softer cracks and darker color, and some people tried
for themselves and agreed with my observation. You can try yourself if
it leaves questions.
I remind you that I am not negating other explanations. I am simply
saying none of these explanations is good enough to be stated as if
it were a fact. I wouldn't say a thing if otherwise.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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83) From: Dan Bollinger
Something I've been thinking about is the use of endotherm versus
endothermic reactions.    From what I can tell they are not synonyms. I
began thinking about this after reading the article in S-M.  I think
endotherm means anything that is hotter than its environment and is giving
off that heat.  I know for a fact that an exothermic reaction is one that
produces heat during the chemical process.  Like a burning log or MEKP
catalyst in promoted polyester resin.  Dan
<Snip>
be
<Snip>
encompasses
<Snip>
part
<Snip>
the
<Snip>
just
<Snip>
become
<Snip>
love
<Snip>
taking
<Snip>
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84) From: Dan Bollinger
That might work.  I look forward to seeing your results. I believe such
tests are usually done with a calorimeter.
<Snip>
outflow
<Snip>
either
<Snip>
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85) From: Ed Needham
Deward...I believe it is due to the heatsink properties of the bean mass
being saturated, and not due to spontaneous heat generation.
I see absolutely no scientific evidence to show spontaneous heat generation
until near burning.  Dan's Scientific American article does define exothermic
reaction to include...
"Those that require heat to occur are described as endothermic, and those
that release heat as exothermic."  And it went on to also include stored heat
being released as an exothermic reaction.  So, by that definition, beans can
be exothermic if the surrounding heat source is reduced and stored heat is
actually emitted rather than absorbed.  That is a change in definition for
me.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

86) From: Charlie Herlihy
--- dewardh  wrote:
<Snip>
 
 Hi, I just want to jump in here for a moment to remark on
something I don't need a collage degree to comment on. In
batches larger than the couple of ounces roasted in popcorn
poppers the roasting profile prior to first crack is very
important as  it determins how well you CAN control what
follows. The Black Bear site also mentions how they ramp way up
to the most agressive heating of the roast then(before first
crack) but lower the heating before first crack begins. Now,
direct knowlage aside and impressions and guessing after much
roasting- I always assumed based only on what I'd read, that the
reason that my oven temp. increases around the time of first
crack without me adding any extra heat was due to the exothermic
chemical reactions that occur in roasting coffee beans. It's
dramatic to watch because my brick oven is a substancial bit o'
mass. After following this discussion I'm more likely to guess
that the beans have just stopped absorbing heat. The temp. in
the oven does drop a fair bit just after I put the 4 1/2 lbs of
beans into it.  Just as an interesting footnote, sustainable
exothermic reaction takes place at a very high temp., higher
than my 650 degree thermomiter can read, and coffee oil seems a
fairly clean and hot burning fuel with lots of caloric energy.I
watched a 5 lb. batch burn for 5 minutes before I got bored and
dumped water on it as it looked like it wanted to continue
burning for quite a while longer. A coffee warehouse fire would
be very difficult to put out.
 Charlie
<Snip>
=====
Do You Yahoo!?
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87) From: Ben Treichel
Ryuji Suzuki -- JF7WEX wrote:
<Snip>
It was stated previoulsy that the bean loses mass during the first 
crack, if that mass has 'left the system' then given the same amount of 
heat input, the temperature could rise faster, due to the lower bean mass.
<Snip>
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88) From: Ed Needham
Is there scientific evidence of CO2 before first crack?  After first crack?
Where?
Oh, by the way, here's a good definition of the Maillard reaction...http://www.homeroaster.comed">http://www.orst.edu/food-resource/color/maillard/reaction_a.htmlEd Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

89) From: Jeffrey A. Bertoia
Ryuji Suzuki -- JF7WEX wrote:
<Snip>
Ryuji
Not being a chemist perhaps I'm a little out of my league but that's 
never stopped me before. :-)
I am however a controls designer and have a lot of experience with 
controling many different
processes.  I have also had a tremendous derire for a set it and forget 
it roaster.
Since nothing has been available I've been looking into it myself.  I've 
critically watched a number
of roasts and done a little experimenting.  I have discovered (on my 
own) that at certain points
the process seems to go into a positive feedback situation.  To me that 
'feels' like the overall reaction
becomes exothermic.  I know that when I remove beans from heat during 
the second crack I
must actively cool them in order to terminate the crack.  If I am 
roasting in a pan and just pull
it off the fire the crack doesn't even think about slowing down.  This 
is definately more pronounced
with larger masses of beans (probably due to the reduced surface area 
per unit volume of the mass).
Go to your local roaster and watch what happens when he dumps a 12 KG 
roast.  If you dump it at
the second crack the roast continues on its own.  To me this says 
exothermic.
I guess what I am saying is that my empirical observations agree with 
Sivetz, Illy and the others.  If
it looks like a duck, walks like a duck and quacks like a duck it's 
probably a duck. :-)
jeff
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90) From: Ed Needham
You thought about trying to find a West Bend "Crazy8" popper, the Stir
Crazy's big brother?  I wonder if it is a bit heftier.  I see new ones on
Ebay every now and then.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

91) From: Ed Needham
Going higher and exceeding the input temperature are two different things.
If only a rise in output heat is measured, then it could be from decreased
absorption by the beans.  If, in fact the output heat is 'greater' than the
input heat, then it could be safely said that the beans are producing heat.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

92) From: Ed Needham
On my BBQ Grill roaster, I set up the flame so the roaster can maintain an
environment temperature of around 500F, put the beans in and walk away for
about 5 minutes at a time.  Each time the thermometer remains stable at 500F.
At about 15 minutes, a heavenly smell is emitted and 30 seconds later I hear
the first pops of first crack. Around that time, I also see the thermometer
creep up, and I have to set both burners lower to maintain the same temp into
second crack.  At first hint of second, I can turn off one burner and open
the lid and the cracks continue.  Into a full rolling second crack, smoke is
evident, and I stop the roast (many times before this point).  The beans may
be close (within a minute or two) to combustion.  If I totally take the heat
away, the beans cool and don't continue self sustained heat output beyond
what is stored within the beans.
My guess is that the bump at first crack is due to bean mass heat saturation.
The bump at second 'may' be the 'beginnings' of a self sustained exothermic
reaction.
per Dan's reference to Scientific American's definition of exothermic, the
beans are indeed exothermic when they radiate heat.  I don't believe the
beans self generate heat on their own at normal roasting temperatures.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

93) From: Dan Bollinger
<Snip>
and
<Snip>
You are probably right, Ed, but 'endothermic reaction' is something else
entirely, I think.  I think what the article is saying is that once the
sugar starts converting, about 365, that the roast should never fall below
400 (endotherm) because the roast will stall and you'll end up with baked
flavors.  They say 'endotherm' where I would say 'cool' or 'drop below.' Dan
<Snip>
giving
<Snip>
that
<Snip>
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94) From: Dan Bollinger
<Snip>
one
<Snip>
the
<Snip>
like
<Snip>
better
<Snip>
the
<Snip>
Jim,  I checked, I lent my last calorimeter to a buddy and he hasn't
returned it. :(  Never lend tools!  You might be right about BB's
observation.  It would certainly explain what is going on.  From a technical
standpoint I'd like to know what is going on in my roasts.  From a practical
standpoint it really doesn't matter.  I know that I have to be careful and
watch the temperature during 1st crack and that is enough information to
make good roasts.  For instance, I'm enjoying a cup of La Berlina this
morning roasted two days ago to Full City over 11 minutes.  Mellow, rich,
great body and it still has it's 'honeyed tea' characteristic flavor.  Dan
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95) From: Dan Bollinger
<Snip>
temperature rises
<Snip>
is warmer
<Snip>
in play.
I think you have to measure 'outflow' with the beans in a sealed container
with the heat flowing around it, not through it. Otherwise any number of
variables would confound the results.  Maybe I'll try this today.  ;)
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96) From: Dan Bollinger
<Snip>
without
<Snip>
You can double electricity easily since it is first converted to
magnetism -- a force, not energy -- in the transformer's coils and then
reverted to a greater (or lower) voltage.  The analogy is a simple lever.  A
force can be doubled by altering the length of the lever arms as measured
from the pivot.  Doing that with heat is going to be very difficult and the
losses so great...  Dan
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97) From: Dan Bollinger
<Snip>
Here is what Sivetz' patent says on the subject.  He uses the term
'pyrolitic bump'.
" FIG. 9 sets forth in graphical format the detectable thermal rises or
bumps occuring within each coffee bean undergoing roasting in accordance
with the present invention. During approximately the first 12 minutes of
heating of coffee beans 24 the bean temperature rises gradually and
virtually linearly from about 100.degree. to 400.degree. F. During this
initial stage, the coffee beans are drying; they are not being roasted.
Starting at about 400.degree. F., true bean temperature, pyrolitic chemical
reactions begin to occur within each bean and the bean temperature climb
rate accelerates, resulting in the charted thermal bumps A, B and C of FIG.
9. These thermal bumps A, B and C may be detected during roasting to enable
precise roast time control. In addition it has been found that the magnitude
of the thermal bump indicated the nature of coffee beans being roasted and
the flavor of the coffee beverage ultimately produced therefrom.
In FIG. 9 the charted bump A indicated that new crop wet processed mild
coffee grades are being roasted. Curve B is indicative of roasting of wet
processed older crop milds. Curve C indicates dry processed Brazils, and
Curve D, having virtually no thermal bump, is indicative of the low grade
dry processed Robusta coffee beans.
If the roasting process is terminated before the pyrolysis bump occurs, the
beans will not have developed their peak flavors. If heating stops during
the thermal bump, only some of the flavor will have been developed. If
heating of the beans continues more than about 3 minutes after completion of
the thermal bump period, the flavor and aroma producing aldehydes, etc.,
will be altered and driven off and the resultant beans will produce a dark
roast taste which is lacking in aromatics.
A heat cut off point within the range between point E and point F on the
curve of FIG. 9 may be selected to control the flavor characteristics of the
final coffee product. Cutting off the heat at point E produces a light
medium roast whereas cut off at point F results in a dark or Italian roast."
I've attached Fig. 9.  This may not pass through the homeroast server
filters.  You can also view it at:
www.claycritters.com/misc/coffee_roasting_temperature_measurements.jpg
Dan
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98) From: EskWIRED
<Snip>
<Snip>
What do you mean by "going higher"?
<Snip>
I don't think we can measure output heat.  However, we can measure output
temperature.  I'm not sure that output heat is even relevant, as it could be
increased by a mere increase in air speed.
 then it could be
<Snip>
I was thinking of measuring the difference in temperature, not heat.  If the
output temperature is greater than the input temperature, then the beans
must be responsible, and we can conclude that they generate heat independent
of the input.
<Snip>
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99) From: EskWIRED
<Snip>
 I don't
<Snip>
But then you disagree with every published report anybody here has ever come
across.  Why?  What makes you think that Illy and Davids and Sivetz and the
other half-dozen quoted sources are all uniformly incorrect? Can you point
to anyone or anything to support your opinion?
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100) From: AlChemist John
Sometime around 13:36 9/8/02, Dan Bollinger typed:
<Snip>
Mind you, I haven't weighed in on this conversation yet, ( I want to do 
some research at work) but most of those quotes sound like they could well 
be misquotes of "common knowledge".
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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101) From: AlChemist John
Sometime around 14:07 9/8/02, R.N.Kyle typed:
<Snip>
Considering that "they" say the exothermic reaction is at 2nd crack, not 
first, I would be inclined to attribute this observation to a change in 
heat capacity of the bean.  Once the majority of the water is out of the 
system, I would expect it to take less input of energy to maintain a given 
temperature.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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102) From: Cathy M.
EskWIRED wrote:
<Snip>
The nature of science is not authoritarian.  I need not supply any proof in
order to be skeptical or to challenge the "authority".  It is up to the
authority to prove his case subject to scrutiny of his methods and materials,
the design of his experiment, and the validity of his conclusions.
The question I would have is: how do the "authorities" prove that there is an
"exothermic reaction in coffee during the roasting process? And are we talking
about an exothermic chemical reaction such as combustion or mixing sodium
hydroxide and water, or are we actually referring to an "event" such as a
release of stored heat (fresh cow pie?)
Resolution of this dilemma can only be found by 
1. defining terms (experts have evidently not done that or there would be none
of this confusion.)
2. presenting repeatable experimental evidence which conclusively proves the
theory. 
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103) From: Cathy M.
EskWIRED wrote:
<Snip>
Temperature is not identical to heat.  Heat is measured in the number of units
required to raise a known mass of something a specified number of degrees of
temperature.  Measuring temperature alone will not tell you anything about heat
unless the other variables are standardized.  In your example, all you will know
is that the temperature within the bean chamber is rising faster than it was
rising previously.
-- 
For the conservation of the Tibetan Lhasa Apso,
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104) From: Dan Bollinger
<Snip>
an
<Snip>
talking
<Snip>
<Snip>
Uh, not the greatest of examples, a fresh cowpie is an exothermic reaction
AND an exothermic condition (event).  It releases stored heat from the cow's
body as well as creating heat by the continued decomposition of grass.
After doing a lot of reading on the subject I can now say with 'authority',
"A sidewalk heated by the sun and giving off heat at night is not an
exothermic reaction, but it is exothermic."   Can I prove it?  Not today!
Dan
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105) From: AlChemist John
Sometime around 12:28 9/8/02, dewardh typed:
<Snip>
How about an exothermic "step".  From my point of view, what appears to be 
occurring is that the beans are going through endothermic reactions 
and  thus gaining energy.   The cracks are the response of the beans not 
being able to store the energy they have accumulated.  The matrix breaks 
down and physically releases heat in an exothermic step, not reaction.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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106) From: EskWIRED
<Snip>
<Snip>
That is why I made the distinction.  I said that I proposed measuring
temperature, in response to your comment about measuring heat.
Heat is measured in
<Snip>
Which variables are you referring to?
 In your
<Snip>
I disagree.  I don't propose measuring the rate of temperature change.  I
instead propose equalizing the temperature of the input and the beans below
first crack, so that there is no change, and then raising the input temp
slightly.  If the beans attain a higher temperature than the input
temperature, then I conclude that they produce heat.
If one were to get these results, do you have any other explanation?
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107) From: Ben Treichel
AlChemist John wrote:
<Snip>
This raises an interesting question, when does the bean lose its mass? 
Is it all moisture before the first crack? When it cracks? Some of both?
Ben
<Snip>
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108) From: Dan Bollinger
<Snip>
describe.
Jeffrey,  Yes, I meant voltage. Voltage was what Rick was talking about.
Dan
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109) From: Dan Bollinger
I sense a discussion coming now of EMF, hi/lo mu, left and right hand rules.
John
EMF?   Hmmmm.......  Now where did Rebecca put her EMF meter......   No
matter, I'll just take a Kirilian photo before and after roasting.  That
should tell us everything we need to know.  Right?     ;)    Dan
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110) From: Jim Schulman
On 9 Sep 2002 at 9:46,  Cathy M. wrote:
<Snip>
The experiment is to run my roaster with constant input 
temperature and air volume, measure the temperature at 
the inflow and just above the bean mass. If the 
temperature of the bean mass ever exceeds the inflow 
temperature, an exothermic reaction has taken place. If 
it doesn't, nothing is proved either way (the 
exothermic heat could have been lost through the glass, 
for instance).
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111) From: EuropaChris
I think this reasoning is flawed.  Reason is that the fast moving airflow 'prevents' the bean mass from generating it's own heat (unless it actually catches on fire).  The mass volume of air (say at 440F) will remove the heat generated by the beans so quickly, that you'll never see it with thermometers.
The only way you'll reliably see an exothermic bean is to heat it in a closed chamber with a supply of oxygen.  You will eventually reach a point where the bean generates it's own heat.  However, I feel that this will be the start of combustion, and by then it's way too late for coffee.  Pyrolysis is NOT combustion, but a chemical breakdown of the bean structure.  Wood undergoes pyrolysis as it heats up in a fireplace or stove.  Wood can also undergo this process at much lower temperatures over long periods of time.  Highly pyrolized wood can catch on fire at much lower temperatures due to the absence of any moisture and the modified chemical structure.
Coffee undergoes this same process during roasting.  I just don't know where the reaction becomes self generating.  Any chemists here that can run some tests in closed, heated containers and measure input vs. output heat?
Chris
"Jim Schulman"  wrote:
<Snip>
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112) From: dewardh
Ed:
<Snip>
being saturated
If you can turn that into a coherent "theory" (i.e. pretty much re-write all of 
thermodynamics) you'll become famous far beyond coffee roasting circles . . .
Deward
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113) From: dewardh
Cathy:
<Snip>
theory.
Illy et. al. and Seivets have both done that, and published results of 
(reasonably) well controlled experiments.  Their results, and the resulting 
conclusions, are essentially undisputed in the commercial roasting trade, 
undisputed by the very people who have both a compelling interest in and the 
resources to verify those conclusions.  Others here have reported, albeit 
without careful instrumental monitoring, corroborative results.
A small number here have different "beliefs", but *no* controlled (and properly 
instrumented) experiments to support those beliefs.  They offer no coherent 
theory to explain their beliefs, and no experimental evidence to support them. 
What one chooses to "believe" is, of course, one's own business . . . (but it's 
not "science").
Deward
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114) From: Irene and Lubos Palounek
Deward wrote: "...if you can turn that into a coherent "theory" (i.e. pretty
much re-write all of
thermodynamics) you'll become famous far beyond coffee roasting circles..."
Remember that, in a quite different field, in four papers between 1950 and
1953, John Nash made seminal contributions to both non-cooperative game
theory and to bargaining theory. At that time, his contributions were quite
opposite to the widely accepted knowledge. He pretty much rewrote the theory
of non-cooperative games and the bargaining theory. And he became famous far
beyond the circles of mathematicians.
However, he had to wait until 1994 before the Nobel Price in Economics was
awarded jointly to him, John Harsanyi, and Reinhard Selten for their
pioneering analysis of equilibria in the theory of non-cooperative games.
Regards, Lubos
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115) From: EskWIRED
<Snip>
Sounds good to me.
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116) From: Jim Schulman
On 9 Sep 2002 at 11:36, Chris Beck wrote:
<Snip>
My in-roaster test could prove that the reaction has gotten exothermic (by seeing a higher 
temp), but granted, it probably won't.
A closed system calorimeter style test would only prove that beans do burn under some conditions 
at some temperature. The results may not apply to any actual roaster.
If I had the right equipment, I'd roast a single bean and measure its internal temperature 
development. Repeat that enough times at different temperatures, air flow rates, heat transfer 
methods, bean varieties etc., and one would actually know what was happening thermally during a 
roast. After each roast, I'd test the beans for the amount of sugars and the Maillard 
sugar/amino acid compounds whose name I can't recall.
Jim
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117) From: C. Marley
EskWIRED wrote:
<Snip>
The mass of the mass whose temperature is being raised and measured, and
the other variables that attend the measurement - possible heat loss by
various routes related to the specific composition of the mass in
question etc.
<Snip>
<Snip>
What do you mean by "equalizing the temperature of the input and the
beans".  You cannot input temperature.  Heat is what is input, and what
raises temperature, and that can only be measured in calories or BTU's 
If a substance has the ability to store heat but physically it can only
do so up to a point, then if we apply a constant heat source to it in a
closed system, the temperature will rise but not linearly, because the
substance is storing heat.  When the capacity to store heat is exceeded,
we would predict an accelerated rise in temperature with the same rate
of heat application.  In fact even if we removed the heat, we could
expect a brief continued rise in temperature by release of stored heat,
due to a lag in achieving equilibrium, followed by a gradual decline in
temperature.
-- 
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118) From: dewardh
Lubos:
<Snip>
1953, John Nash made seminal contributions to both non-cooperative game
theory and to bargaining theory. At that time, his contributions were quite
opposite to the widely accepted knowledge. He pretty much rewrote the theory
of non-cooperative games and the bargaining theory.
That's the movie version of it, anyway . . .
It might be a bit more accurate to say that he first applied some particular 
(new) analytic tools to questions that had not been much examined before, and 
thus *wrote* the theory . . .
But neither version compares to what we have here.  The present discussion is 
more like some people asserting the belief that if you burn Hydrogen and Oxygen 
the product is H3O . . . and if you think otherwise it's because you're unable 
to think for yourself and too ready to turn to "authority" for answers . . .
Deward
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119) From: dewardh
Cathy:
When the capacity to store heat is exceeded,
we would predict an accelerated rise in temperature with the same rate
of heat application.  In fact even if we removed the heat, we could
expect a brief continued rise in temperature by release of stored heat,
due to a lag in achieving equilibrium, followed by a gradual decline in
temperature.
How peculiar . . . that's not at all how it works in my corner of the Universe. 
 Out here materials have a property called "specific heat", defined as the 
temperature rise of a constant mass for a given heat input, which remains 
relatively constant for any particular "phase" of that material.  Specific heat 
may change when a material's phase changes, and a quantity of heat may be 
"stored" in the phase transition (called "latent" heat).  The common exemplars 
are the ice/water/steam system and Glaubers salts.  Within a single phase there 
is no way for "the capacity to store heat [to be] exceeded" (except, perhaps, 
in some pretty outrageous laboratory situation), and one would not, for 
example, expect the temperature of an ice/water system to continue to rise (if 
it was rising at all ) after the removal of the heat source while the ice 
gives up some more "stored heat".
Of course things are generally acknowledged to be "different" here in Berkeley 
.. . .
Deward
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120) From: C. Marley
dewardh wrote:
<Snip>
A bean composed of cellulose, other carbohydrates and water, undergoing
pyrolysis (cooking) has more complex physical properties to consider
than ice/water/steam.  In fact one part of that process involves a phase
change of one of the components - water. During the first crack,
presumably the boiling off of the water is completed. Water has a rather
high specific heat if I recall. Sugars also undergo phase changes, 
At the first crack, the physical integrity of the bean is disrupted,
changing its capacity to store heat.  And just as a closed system
containing boiling water with a constant heat source applied will
experience a rapid rise in temperature after the last of the water has
been boiled off, a similar theory could be advanced to explain the
"exothermic event" at he first crack of roasting coffee.  Exothermic
chemical reactions are pretty drastic, and short of combustion, I can't
imagine any chemicals in a coffee bean that would engage in such a
violent reaction, and we still be able to drink the result.  So I will
stick to the theory that the rise in temperature is a physical event,
not a chemical one.  I think that would be a safe hypothesis even in
Berkeley. ;o)
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121) From: Jim Schulman
On 9 Sep 2002 at 20:22, C. Marley wrote:
<Snip>
So what you're saying that the water to steam transition, under high pressure, 
raises the temperature rapidly inside the bean. When it vents in the first crack, it 
raises the temperatures one measures above the input heat's temperature.
I joked earlier about heatpumps, but I guess this would be an instance.
If this mechanism is feasable, even higher bean temepratures couldn't prove chemical 
exothermy. There's a mechanical alternative hyporthesis.
Jim
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122) From: EskWIRED
<Snip>
I mean that the hot air, which is being input to the roasting chamber, and
the beans themselves should be the same temperature.  I propose that the
system be stable before the testing phase commences.  Then the input (air)
temperature be raised sufficiently to cause first crack.  The beans, of
course, will lag, and will take a little while to heat up.  If they heat up
to the air temp, and no further, then the result is inconclusive.  But if
they increase in temperature beyond the input (the air) temperature, then
there must be heat coming from somewhere other than from the air.
Given that everybody who has ever studied this universally tells us that the
beans undergo exothermic chemical reactions at the critical temperature, I
think we can then conclude that Illy and Sievets and Davids (and everybody
else who has ever studied the process) are correct, and that exothermic
reactions occur during first crack.
  You cannot input temperature.  Heat is what is
<Snip>
But at no time would we expect to see the beans hotter (i.e., at a higher
temperature) than the air, which is the whole point.
If the bean temperature exceeds the input temperature, then there must be a
source of heat other than the air. Given the universal agreement among those
who have carefully studied the process, we can assume that the source of
heat is exothermic reactions within the beans.
Unless you can develop another plausible explanation, perhaps.
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123) From: EskWIRED
<Snip>
Not only that, but nobody here is suggesting that Ed is schizophrenic.  :)
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124) From: Dan Bollinger
<Snip>
I can't
<Snip>
Good point, Cathy.  I don't know if sugar reactions give off heat or not
when they convert to different sugars. I don't think so.  I do know that HCL
and sugar is exothermic and quite fun to watch!
Cellulose is out since we know it doesn't combust until about oh, Fahrenheit
451 or so!  Besides, we'd know if we got a charred roast.
Perhaps some proteins?  They convert a low temperatues, but are the
exothermic?  I doubt it.
Any possible candidates are sure to be present in low percentages since
water, sugar and cellulose are the major chemicals in a bean.  Even if these
low percentage chemicals were reacting and exothermic, they'd have to be
pretty strong to make a significant temperature change in a mass that was
already 400+.
Dan
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125) From: EskWIRED
<Snip>
But ONLY if the heat source is over 212.  If it is 212, no increase in
temperature will occur.
 a similar theory could be advanced to explain the
<Snip>
But ONLY if the heat source is at a higher temperature than the beans are
while cracking.  If the heat source is at the critical temperature, and not
higher, your explanation does not work.
<Snip>
All of them?  Universally?  How much chemistry have you studied?  Are you
really qualified to make that statement?
 and short of
<Snip>
Then why is it that everybody who has closely studied the phenomenon
disagrees with the hypothesis? Are you really saying that Illy and Sievetz
and Davids and everybody else is mindlessly spewing nonsense?
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126) From: Ed Needham
<Snip>
"EskWIRED" asked Ed,
<Snip>
Ed replied: I lifted that out of the post I was replying to.  I was just
pointing out that they were comparing apples and oranges--  see below.
<Snip>
Rick quoted him and answered:
<Snip>
"EskWIRED" then remarked on my incorrect usage of the term 'heat' when I
should have used 'temperature'.  My mistake.  It was late.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

127) From: AlChemist John
Sometime around 07:15 9/9/02, EskWIRED typed:
<Snip>
How are you going to know how much heat you are adding?  I don't see any 
way to add an exact amount of heat and predict what temperature it should 
produce.
Aside from that, even if you are at a steady temperature,  how are you 
going to know when you are at the cusp of an exothermic step so that "just 
a little" more energy will start the reaction?
  BTW, how much of a higher temperature would are you expecting?  I think 
it could well be rather subtle under the conditions you have described.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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128) From: Ed Needham
I DON'T necessarily think Illy, Davids or Sivetz are incorrect.  I do NOT
believe something just because someone chooses to say it, even IF it is Illy,
Davids or Sivetz or Schomer, or anyone else with credentials in coffee.  I
have NOT seen any hard science indicating an exothermic (heat generating)
reaction under typical coffee roasting conditions.  I have seen lots of
people use those terms in articles or books.  I would LOVE for someone to
show me the actual controlled tests and measurements behind those assertions.
I've not seen them yet.
I personally 'believe' (read 'theory')  the beans do not generate any heat on
their own under typical roasting conditions.  If Illy, Davids or Sivetz want
to talk to me about my doubts, they know where to find me.
I'm not trying to be a hardnose, but too many times facts are accepted
without any thought as to their validity.  I personally believe this is one
of those times.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

129) From: Ed Needham
I have found numerous, sometimes differing definitions of the term
'exothermic' and 'exothermic reaction'.
After digesting the substance of the word usage in numerous articles, I am
leaning toward this as a definition:
Exotherm or exothermic means to release heat.
Exothermic reaction means to create heat.
I'm sure, with all the confusion these terms have wrought, that several will
disagree.  That's OK.  These definitions seem to be working for me.
Coffee beans can be exothermic if they are heated and allowed to release that
heat.  Coffee beans probably don't create heat as in an exothermic reaction,
unless they are near combustion.  Deward's argument about release of CO2 as a
result of oxidation and carbonization of bean components is the best argument
I've seen yet in favor of an exothermic reaction occurring, but I still am
not sure CO2 is released as part of the roasting process.  I know it is
released after roasting, as part of the outgassing, and I have seen hard
research pertaining to that.  I think it makes sense that CO2 is probably
released during roasting, but have not seen research measuring that.
Whew.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

130) From: Ed Needham
I agree.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

131) From: Ed Needham
Not sure it has anything to do with the cell matrix breaking down.  The
perceived release of heat 'I believe' can be explained by the bean mass
slowing or stopping heat absorption, the drying of the bean, so there is less
moisture to act as a heatsink, and the reduced bean mass.  All add up so that
it seems like the beans are generating their own heat.  True, near the end of
a roast, the heat can be almost turned off and still maintain a constant
temperature, but that is true for ovens, water heaters, boiling water.  It
seems like it takes a tremendous amount of heat to bring water to boiling,
and if you watch it, it takes forever, but after it boils, you can reduce the
heat to 'warm', and it will continue boiling.  Start on warm, and it could
take hours to boil.
I think we severely underestimate the heatsink properties of a pound of green
coffee beans.  In a hundred pound 'bag' roaster, the bean mass could suck up
a lot of heat energy.  near the end of a roast of those same beans, a trickle
of flame could maintain the heat.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

132) From: Ed Needham
???

133) From: Ed Needham
My point exactly.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

134) From: Ed Needham
Deward, you are backhandedly insulting me and others on this list, of course,
without mentioning any names.
My questioning has been fair and reasonable.  Attempting to more clearly
define terms that 'I believe' have been loosely tossed around by
'authorities' is not a crime.  I am not asserting anything.  I am not
authority bashing.  I do have an opinion, and I have shared that on this
list.  I have clearly stated it as opinion.
Aside from defining the term 'exothermic' and 'exothermic reaction', I am
also asking to see measured evidence of these, which to date, I have not
seen.  Lots of mention of it happening, but no measured, controlled
experiments showing it exists.
If you want to sit on the sidelines and take potshots at me or others, I
guess that's your prerogative, but it won't win any points with me.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

135) From: Ed Needham
If the beans are cooler than the 'surrounding environment', they will absorb
heat until they are at an equilibrium with their environment.  At that point,
they are functionally saturated, 'in relation to their environment' and will
not absorb more heat.
Raise the temp of the environment, and they will reach an equilibrium again.
Raise the temp enough, and the beans will absorb enough heat and may combust.
It's not that complicated.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

136) From: Ed Needham
You can suggest it, but we will deny it. 
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

137) From: Eric Fesler
I am no expert here but it seems silly to doubt that
somewhere in coffee roasting there are exothermic reactions.
The vast majority of reactions are either exothermic or
endothermic.  (Few chemical reactions have exactly the same
energy state before and after)  Coffee has 100's (1000's ?)
of reactions.  At some stages in roasting it is likely to
lean towards endothermic and at other times exothermic.
Since it ends with charcoal burning which we know is
exothermic doesn't it seem likely that it would lean more
towards exothermic as this extreme is aproached??
Cheers,
Eric

138) From: James Gundlach
On Tuesday, September 10, 2002, at 01:36 AM, Eric Fesler wrote:
<Snip>
This is the kind of perspective that can change minds.  I am no longer 
an agnostic.  Count me as an exothermic believer.
Jim Gundlach
a producer of unmeasured exothermic reactions.
in La Place, Alabama
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139) From: Dan Bollinger
<Snip>
Ed, that jives with what I've learned, too. Dan
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140) From: EskWIRED
<Snip>
I don't understand your objection.  If the beans and the air are both at the
same temperature, and the air is raised in temperature somewhat, and the
beans then get hotter than the air, then what difference does it make "how
much heat you are adding"?  What am I missing?
Once the beans reach the air temp, the air will not raise the bean temp any
longer (correct?).  If the bean temp continues to rise, I would conclude
that there is an exothermic chemical reaction within the beans, or that some
unknown source of energy exists.
<Snip>
By knowing the temperature that a particular type of bean enters first
crack.  My understanding is that the critical temp is around 400F.  I can't
do this experiment, because I can't measure the temp of the air entering my
roast chamber, and I can't measure any temp above 392 with my Polder cooking
thermometer.
But it seems to me that if one were to ever so slowly raise the air temp, so
that at no point is it significantly hotter than the beans, one could
measure the critical temp fairly accurately when first crack commences.
<Snip>
I have no idea.  I too think it could be rather subtle, but because I don't
know diddly about organic chemistry, I hold out hope that it would be
measurable.
Hell - Schomer and Illy, et.al. and Davids and everybody else claim that
there are exothermic chemical reactions within the beans during first crack.
I have no doubt whatsoever that they are correct, but for some reason, there
are those here who are absolutely convinced that these careful researchers
are all, to a man, full of hot air.
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141) From: AlChemist John
Sometime around 17:45 9/9/02, Jim Schulman typed:
<Snip>
Exactly.  This is and has been a grand discussion, but I do not think that 
any amount or type of data we could produce here can conclusively prove 
that there are exothermic reactions going.  Just from heat and temperature 
measurements I don't see how you could tell an exothermic reaction from a 
change in bean heat capacity.
Both would/could show a temperature rise suddenly, but from radically 
difference sources.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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142) From: AlChemist John
Sometime around 21:01 9/9/02, Ed Needham typed:
<Snip>
Agreed.  That is actually closer to what I meant.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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143) From: AlChemist John
Sometime around 05:49 9/10/02, EskWIRED typed:
<Snip>
 the
<Snip>
I missed back in the original post that a dual channel TC would be used to=
 
measure air temperature before and after the roasting chamber.  I read 
(incorrectly) that just the output temperature would be read.
<Snip>
 some
<Snip>
Or the heat capacity of the beans is lowering due to chemical changes 
occurring in the bean.
<Snip>
 cooking
<Snip>
I've been meaning to bring this up.  Where did you find the critical  temp=
 
is 400F and/or at first crack.  A few posts have mentioned first but all I=
 
have found is the following:
The second step is followed by a short endothermic
period, which is followed by another exothermic (beans
release heat) step called the second crack. This
second pyrolysis occurs between 225-230C, and the
roast color is defined as medium-dark brown (Agtron
#50-45) (Davids, Roasting, 68).
<Snip>
I am skeptical it would be much, but upon seeing data, I will happily back=
 
peddle .  I have a feeling though that if you do happen to be at the 
appropriate exothermic point in these controlled conditions, the other 
beans are just going to absorb the energy release and no temperature rise 
will be noted.  Just me being pessimistic.
<Snip>
 crack.
See above about 1st crack.
<Snip>
 there
<Snip>
Actually, I am simply of the position that I would like to see conclusive 
data.  Maybe the class of reactions that are exothermic or something of the=
 
like. Not just little temperature/time bumps.  I do not believe these prove=
 
an exothermic reaction (if they were even meant to).
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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144) From: EskWIRED
<Snip>
A sudden increase in the amount of heat released into the output air could
be explained by that. But could that really explain the beans attaining a
higher temperature than the air they are exposed to?
How could that be possible?
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145) From: EskWIRED
 I do
<Snip>
If the beans are hotter than the constant temperature of the air entering
the chamber, then why would this not show that the beans themselves are
producing heat?
I'm not talking about the amount of heat, nor any temperature delta over
time.  I'm talking about the following (as an example.  Change the specific
temps mentioned to anything you want, so long as the beans are hotter than
the air entering the chamber):
HEAT SOURCE:  Rock steady 410 degrees.
BEANS:  400, ... 403, ... 408, 409, 410, ... 420, ... 435...
How can the beans possibly get hotter than the air entering the roasting
chamber, absent an exothermic reaction within the beans?
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146) From: EskWIRED
<Snip>
<Snip>
How do you reconcile these two statements?  They seem to be opposites to me.
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147) From: EskWIRED
<Snip>
Bingo.
<Snip>
400 is sloppy shorthand.  "A little higher than 400" is likely closer to
correct.
IME, I can slowly raise my beans to 392, at which point my thermometer
reaches the limit of its abilities.  If I then turn down my fan speed a
slight amount, the first crack commences quickly.  My assumption is that the
temp is somewhere near 400, or a little higher.
From Coffee Research Org:
"The second step, often called the first crack, occurs at approximately 205
C (400 F)..."
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148) From: Dan Bollinger
I've been meaning to bring this up.  Where did you find the critical  temp
is 400F and/or at first crack.  A few posts have mentioned first but all I
have found is the following... John
John,  I found one of the references.  It was talking about the temperature
required to convert sugars.  It said that the critical temperature was 365,
but this varied somewhat between beans.  So, they said that the roast, once
it hit 400 should never drop below 400 or the sugar conversion would stop
and the  roast would stall.  You could probably and safely drop below 400,
but it sounds like they wanted to pad in a safety margin.  Dan
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149) From: dewardh
<Snip>
Most, if not all, Human metabolic processes are exothermic chemical reactions . 
.. . we don't normally regard any of them as "pretty drastic" . . .
Deward
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150) From: dewardh
Jim:
<Snip>
Big "if" . . . (especially absent *any* supporting, let alone confirming, 
experimental evidence).
Deward
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151) From: Ed Needham
I've not seen any evidence that the beans actually attain a higher temp than
the air they are exposed to.
Ed Needhamhttp://www.homeroaster.comed
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152) From: Ed Needham
I am not 'confident' that Illy, Davids or Sivetz are incorrect. (I just don't
want to take what they say 'carte blanche' without research to back it up).
I personally 'believe' (read 'theory')  the beans do not generate any heat on
their own under typical roasting conditions.
Sorry.  My first statement was poorly constructed.
Ed Needhamhttp://www.homeroaster.comed
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153) From: EskWIRED
<Snip>
You mean, other than the extensive literature on the subject by Illy,
Sievetz and Davids?
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154) From: AlChemist John
Sometime around 07:57 9/10/02, EskWIRED typed:
<Snip>
I can't readily see any other way.
More to what I was meaning was that I don't think we have the equipment to 
produce data that would show conclusive data.  I would expect data 
produced  to look like:
Heat source: 410
Beans:  400, 401, 402,...409 ,410...410...410...410.1, 410.0.,410.1, 
410.0  huh, was that exothermic or not (scratching one's head)
or even more likely
Heat source:    410
Beans           400
                 402
                 404
                 405 actual exothermic reactions occur helping temperature 
to rise to 406+
                 406
                 408
                 410,  410,  410
Without working on this for quite some time, I think there are just to many 
unknowns and variable for US to produce exothermic data.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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155) From: AlChemist John
Sometime around 08:34 9/10/02, EskWIRED typed:
<Snip>
 the
<Snip>
Let me rephrase.  Where did you find that first crack was exothermic?  I 
have only found 2nd crack.
"The second step is followed by a short endothermic
period, which is followed by another exothermic (beans
release heat) step called the second crack. This
second pyrolysis occurs between 225-230C, and the
roast color is defined as medium-dark brown (Agtron
#50-45) (Davids, Roasting, 68)."
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

156) From: AlChemist John
Sometime around 07:43 9/10/02, EskWIRED typed:
<Snip>
The beans, no. the surrounding area where you are taking your measurements, 
yes, I believe it can, to a small degree, while the system attempts to 
maintain the input temperature equilibrium.
You can measure input temperature(air) and output temperature (air and 
beans) but not just the beans.  Regardless, the beans would not be going to 
a higher temperature in any case.  They are releasing heat so that they can 
maintain a constant temperature.  Thermodynamic equilibrium is temperature 
based not heat/energy based.
BTW, I not really advocated a heat capacity change to explain what is 
really happening, I just brought is up as an option.  It MAY contribute 
though in the roasting process ( and probably does as water is driven off) 
but not much at to temperatures we are discussing
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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157) From: EskWIRED
<Snip>
Between 338 and 392 degrees F, carmelization begins. It is at this point
that water and carbon dioxide fracture and out-gassing begins causing the
first mechanical crack. These are the chemical reactions, occurring at
approximately 356 degrees F, that are exothermic.http://lists.sweetmarias.com/mailman/listinfo/homeroast">http://www.sweetmarias.com/roast.carlstaub.htmlhomeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

158) From: EskWIRED
<Snip>http://www.sweetmarias.com/roast.carlstaub.htmlBetween 338 and 392 degrees F, carmelization begins. It is at this point
that water and carbon dioxide fracture and out-gassing begins causing the
first mechanical crack. These are the chemical reactions, occurring at
approximately 356 degrees F, that are exothermic.
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159) From: Ed Needham
I mean measurable evidence.  Not literature.  Can you show me where the bean
temperature is measured as higher than the heated environment temperature?
In Illy?  Davids? Sivetz?  Not words.  Not opinion.  Measured data.  I've not
seen it.
Ed Needhamhttp://www.homeroaster.comed
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160) From: Ed Needham
I have only one problem with that.  Mr. Staub didn't cite references to
research backing his claim.  Without a citation, it's just his opinion.
Why can we not locate hard research to show an exothermic reaction?
Ed Needhamhttp://www.homeroaster.comed
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