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Topic: observations on roasting (18 msgs / 327 lines)
1) From: C. Marley
Going back to a previous thread on "exothermic" reactions, I recently
roasted some batches of coffee in the wok, using a glass cover to assess
the water release from the beans.  In every case, there was a great deal
of water released as vapor up to the first crack.  As soon as first
crack commenced, the amount of steam on the glass cover became
negligible.  My theory is that the phase change of water in the beans
"used up" a great deal of the heat applied, and caused a surge in
temperature when the available water was depleted, accounting for the
"exothermic" reaction observed through temperature measurements..
-- 
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

2) From: EskWIRED
My theory is that the phase change of water in the beans
<Snip>
I'm sure that you are aware that such a temperature rise would NOT be due to
an exothermic reaction, and that is why you put the word in quotation marks.
Other than your observation, what evidence do you have for your theory that
no true exothermic reaction takes place during first crack?
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3) From: Ed Needham
Cathy, that is truly an interesting experiment and observation.  So maybe it
infers that the period before first crack involves heating and dissipating
most of the moisture.  The rest of the reactions take place in a basically
moisture free environment.
An email reply from Carl Straub might be interesting to some here...
(posting with his permission) Thursday, September 19, 2002
Basically, I asked him for his definition of 'exothermic', and suggested that
it was one that produces heat.
"Mr. Needham, You are correct, an exothermic reaction is one that "produces
heat." Relative to roasting, about 8% of the mass of Arabica coffee is
sucrose. This is a complex sugar that fractures at its melting point. In pure
crystal form, that melting point is about 180 degrees C. In coffee, however,
that melting point can vary due to alkaloid concentrations and levels of
other related constituents. Once the sucrose fractures into its root sugars,
provided there is sufficient energy to maintain a positive kinetic function
for balance of the endothermic mass, the fractured monosaccharides are
subject to polymerization, which is an exothermic reaction. As 8% of the
charge mass (the monosaccharides) becomes endothermic in nature, the mass
in-total does require less energy to maintain a constant kinetic function.
This is something that is measurable. Carl Staub / Agtron Inc."
Ed Needhamhttp://www.homeroaster.comed
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4) From: Dan Bollinger
<Snip>
Ed, Actually, it is not an experiment, but a test.  An experiment requires a
control group.
<Snip>
Yep.  Many roasting websites call this the 'drying stage'.
<Snip>
function
<Snip>
Good job contacting Carl, Ed!  When it doubt, go to the source. Carl repeats
what my step-daughter, the biologist, said -- and I believe I mentioned it
here -- "decomposing sugar is exothermic, it is releasing the energy that
was stored to make the sugar in the first place."    Dan
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5) From: Ed Needham
Poor choice of word on my part.  Engage head, then type.
Ed Needhamhttp://www.homeroaster.comed
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6) From: C. Marley
EskWIRED wrote:
<Snip>
None.  But in science, one does not have to prove that something does
NOT happen. It is incumbent on the other hand to prove that something
DOES happen.  According to Occam's razor, the simplest explanation is
usually the correct one (and requires the least proof.)  I have yet to
see a convincing experiment to document a true exothermic reaction in
coffee beans at first crack.  And a simple water to steam state change
could account for the observed phenomena.  I was simply adding the
observation that the first crack coincided with the cessation of water
vapor release from the beans, adding weight to the theory that the state
change is what probably accounts for the observed rapid rise in
temperature.
-- 
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

7) From: C. Marley
Ed Needham wrote:
<Snip>
At 8% I doubt that the energy release would be substantial enough to
cause the gross changes in temperature that are measurable with nothing
but a "macro" thermometer.  Whether the energy release by the fracture
of sucrose "provided there is sufficient energy to maintain a positive
kinetic function for balance of the endothermic mass" would be
measurable by gross methods is questionable.  Additionally, Mr. Staub
mentions that there is variability due to variations in "alkaloid
concentrations and levels of
other related constituents". But the "exothermic event" under
examination is not variable at all, but occurs every time coffee
undergoes a first crack.  Application of Occam's Razor suggests that the
variable, complex, exothermic reaction of sucrose, while it may indeed
occur, and may be measurable in the laboratory, is not likely to be
responsible for the phenomena usually assigned to it. 
-- 
Regards, Cathy http://lists.sweetmarias.com/mailman/listinfo/homeroast">http://www.lhasa-apso.orghomeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

8) From: C. Marley
Dan Bollinger wrote:
<Snip>
Actually, a controlled experiment means that all the variables were
controlled. In this case, all the variables were controlled.  Heat,
vessel, cover, all identical.  Several different coffees of the same
measured weight were subjected to the same conditions, and produced the
same observations. I would be correct in calling this a controlled
experiment, however I called it an "observation".
Regards, Cathy
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9) From: EskWIRED
<Snip>
Another "negative" theory that needs no substantiation?
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10) From: C. Marley
EskWIRED wrote:
<Snip>
Without questioning and skepticism there would be no science.
Furthermore, proving a negative is often extremely difficult or
impossible because of the vast number of possibilities that must be
ruled out. Skepticism, on the other hand, need prove nothing. 
Skepticism is merely a challenge for the proponent of an assertion to
offer some sort of convincing evidence.  Measurements: how were they
made, what were they and what did they prove?  If you say that you doubt
that sunlight can cause cancer, your skepticism is valid - it is
counterintuitive.  It is up to me, then, to prove that it CAN cause
cancer, not up to you to prove it cannot.   (So there can be no
misunderstanding, scientific "proof" is not epistemological proof, but
merely reproducible preponderance of physical evidence)
So where are the measurements to be found, that prove that the 8% of
sucrose undergoing variable physical changes in the coffee bean are the
cause of the (invariable) temperature surge at first crack?  Cure my
skepticism with fact, please!
Regards, Cathy
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11) From: Dan Bollinger
<Snip>
I haven't seen one either.  Prof. Eggers, who wrote a paper for the 19th
ASIC conference is sending me his paper, which I hope will help us learn
more.  As far as proof is concerned one way is running a coffee roasting
experiment, like you said.  Another way is proving that a known, previously
proven exothermic reaction ocurrs in roasting coffee. Looking for the latter
may be more fruitful for us.  Dan
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12) From: Dan Bollinger
<Snip>
I found these sucrose texts cited online.  I won't have a chance to look
these up anytime soon.  Here they are if someone wants to take a try:
1 - Dubourg J. (1952) Sucrerie de Betteraves, J. J. Baillère et Fils, Paris
2 - Siline P. M. (1958) Technology of Beet Sugar Production and Refining,
Wyd. Piszezepromizdat Moscow .
3 - McGinnis R. A. (1982) Beet-Sugar technology, Beet sugar Development
Foundation, Fort Collins.
4 - Honig P. (1959) Principles of Sugar Technology,Vol.2 Elsevier,
Amsterdam.
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13) From: Dan Bollinger
This proves that the oxidation of sucrose is exothermic, but does not say if
the pyrolysis of sucrose is.http://soulcatcher.chem.umass.edu/chemland/calorie.html<Snip>
Paris
<Snip>
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14) From: EskWIRED
My theory is that your skepticism has no foundation.  I will offer no proof.
;)
I'm a professional skeptic. And yet, I have no doubt whatsoever that these
simple, well understood chemical reactions, which have been studied to death
for a hundred years, have yielded accurate information.  Maybe I'm just
being gullible, and the professionals who have repeatedly asserted that
first crack involves exothermic reactions are either dupes, or have a hidden
agenda, or something even more sinister.
Let's not worry about it.  It doesn't matter.  We can agree to disagree, and
remain friends.
<Snip>
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15) From: EskWIRED
  Prof. Eggers, who wrote a paper
<Snip>
Dan -
I'd love to read a copy of it.  I assume that it is not posted on the 'net,
but if I could get a photocopy, I'd be very appreciative.
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16) From: Dan Bollinger
Will do.  I just hope it is in English and not French or German.  ;)   The
articles are online for ASIC members only.  :(   Supposedley, they will sell
copies to non-members, but two attempts to purchase it failed (one in
English the other in French).  So, I went to the source and emailed Eggers.
Dan
<Snip>
'net,
<Snip>
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17) From: C. Marley
EskWIRED wrote:
<Snip>
Fair enough, but skepticism doesn't need a foundation.
-- 
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

18) From: Linda Berkoff


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