HomeRoast Digest


Topic: Exothermic and envirnoment vs bean mass (5 msgs / 172 lines)
1) From: miKe mcKoffee
Like I said, think coffee roasting doesn't involve exothermic stages
ignoring the professionals who have in fact done endless testing and
documenting over the years.
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"... because when coffee goes exothermic during 1st crack,..."
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#3)...All of these warm-up stages leading up to first crack are part of an
endothermic process, as the coffee takes on heat, leading to the first
audible roast reaction, the exothermic 1st crack."
#8)... Since first crack is an exothermic reaction, the beans are giving off
heat in first crack, but the quickly become endothermic, meaning that a
roaster that is not adding enough heat to the process will stall the roast
at this point ...not a good thing."
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roasting: an art form and much more." By Cipolla, Mauro Caffe D'artehttp://www.allbusiness.com/manufacturing/food-manufacturing-food-coffee-tea/652288-1.html
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heat in the form of an exothermic reaction...
Many more sources dicussing coffee roasting and exothermic reactions out
there. Do your homework rather than speculation.
Pacific Northwest Gathering VIhttp://home.comcast.net/~mckona/PNWGVI.htmKona Kurmudgeon miKe mcKoffee
www.mcKonaKoffee.com
URL to Rosto mods, FrankenFormer, some recipes etc:http://www.mckoffee.com/Ultimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
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2) From: Floyd Lozano
Coffee professionals aren't necessarily chemists.  I said correct me
if I am wrong.  So thank you for those that have stated the basis for
which the reaction is considered 'exothermic', which is as Ed Needham
states, basic science - the process of breaking the bonds in the
hydrocarbons and forming alternate compounds.  Of course, for this
reaction to occur, energy is required, in this case in the form of
heat.  So you're saying the 'reaction' is endothermic up to the point
where the hydrocarbon bonds are broken and the reaction which forms
the products (h2o?  co2? I'm not a chemist, just a curious guy) is
then 'exothermic' as the energy in the chemical bonds is lost as heat
and the atoms realign into other molecules with a total energy less
than that from which they came?   Is exothermy then simply defined as
'any reaction that results in energy being released, regardless of the
energy it required to get that energy to be released?  From my
'homework', I saw no analysis of the complete system - nobody measured
the heat capacity of the roaster, the drum, and how much is there.
Nobody is measuring the heat output of the gas flame.  I don't see a
comparison of in vs out, simply a measure of air and an approximation
of bean mass temperature.   So, perhaps I am confusing things, and
it's possible to have an 'exothermic reaction' as a part of a system
which is itself not exothermic.
I continue to be curious, despite attempts to blunt my curiousity with
a curmudgeon bludgeon.  I didn't find a satisfactory explanation of
'exothermy' and my chemist wife wasn't around to ask ;)  Sure, if a
chemist says 'oh yeah, anything that puts out heat is exothermic,
cause that's what it means' then yes, I will believe it, but I'm not
one to believe everything out of the mouth of Wikipedia or a
professional of anything other than their profession.  So I ask the
questions!
-F
On Tue, Apr 22, 2008 at 10:14 AM, miKe mcKoffee  wrote:
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3) From: Floyd Lozano
Ok, spoke to my phd chemist wife, which I should have done before to
prevent the harsh rebuke here (should have done my 'homework',
literally!)
An exothermic reaction is determined by comparing the energy of the
reactants to the energy of the products.  The difference is released
as heat.   The energy of the system as a whole is constant (that's
basic thermodynamics, I guess you'd say) where the system is defined
as 'the universe and everything else'.  And all of this is
irrespective of the activation energy needed to bring about the
reaction about which causes reactants to go to products, apparently.
The reaction is still considered exothermic if the energy of products
< energy of reactants.
Im still curious as to what constitutes the system here though.  Is
the energy produced by carmelization of the sugars contained in a lb
of green beans enough to account for the spike in temperature you see?
 I didn't see anything that indicated whether the Maillard reaction
was typically exothermic in my limited reading.
-F
On Tue, Apr 22, 2008 at 11:49 AM, Floyd Lozano  wrote:
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4) From: Dave Kvindlog
So back to the original question (as I remember it)...at what temperature
can a roast be called "cool", the temperature at which the beans are not
going to continue to roast (unless as part of a planned rampdown profile)?
The "cool" temp is not the point at which the beans switch from exothermic
to endothermic, because at just below that point the beans would continue to
bake.  It must be at some temperature between that point and ambient.  Food
can bake at 200F, so I suspect it's somewhere below that temp.
How cool is cool?  (That's a cool thing to know!)
-- 
Dave Kvindlog
iHomeroast
Cedar Rapids, Iowa
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5) From: raymanowen
I know nothing, but I suspect the sugars involved in the Maillard reaction
and caramelization  in the coffee bean are not the C12H22O11 that melts and
caramelizes when I pop Kettle Corn in my Stir Crazy 8.
Just looking at the C12H22O11 formula, it could break bonds to form 12
Carbon atoms and 11 water molecules, but I'm not even sure of that. Breaking
bonds would take energy- endothermic.
Then, maybe the free carbon atoms could combine with atmospheric O2 --> CO2,
the perfect combustion of carbon?
Cheers, Mabuhay -RayO, aka Opa!
See? Composed on a Box of 1's and 0's, with buttons. Degree is 20 C
On Tue, Apr 22, 2008 at 10:13 AM, Floyd Lozano  wrote:
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-- 
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