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Topic: Grinder heating - was:Hand crank grinders vs. burr (19 msgs / 377 lines)
1) From: Mike Koenig
I use the term "firmly believe" because I wont' say anything
conclusively unless i have data, and haven't gotten around to jamming
a thermoucouple into my grinder yet.  I'm relying on my knowledge of
physics and thermodynamics here.
--mike
On Fri, Dec 5, 2008 at 6:57 PM,   wrote:
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2) From: peterz
If you have used a bench grinder, one of those electric motors with an 
abrasive wheel on either side, to grind ferrous metal, you may have 
noticed sparks coming off.
If you look closely where the metal contacts the stone, there is quite a 
glow from which the sparks are flying. The sparks do not seem all that 
hot, and a quick touch to the stone does not seem to produce much heat, 
but I wonder about the point of contact.
Sure looks like heat there!
Could this coffee grinding be the same kinda thing?
The bean gets hot where it is fractured and this has an affect on taste?
Maybe some of those little coffee particles are turning into "sparks".
Not sure, as I can't tell the difference between hand ground, whirly 
ground or Mazzer ground.
Maybe some of you can.
Happy holidays,
PeterZ
Mike Koenig wrote:
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3) From: Angelo
I'm sure there is some heat. Doesn't any friction, or even just 
motion, produce heat?
However, for beans about to be bathed in ~200F water in another 
minute, I fail to see the justification for  slower-turning burrs. I 
like conical burrs for other reasons, but so far, no one has 
convinced me that the "heated" grounds should be a reason...
Years ago, I studied astrology.. Maybe I should investigate whether 
the planets and/or moon phases have an effect on the taste of various 
beans... hmmmm...
A
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4) From: Mike Koenig
Burrs in a coffee grinder shouldn't be touching (unless you like your
coffee fortified with Iron).  You only grind for 20-30 seconds at a
time,  and any given portion of coffee is in contact with the burrs
for a few seconds at most.  The only way you are going to do any
tastable harm to the beans is if the burrs get hot enough to scorch
the coffee as it's grinding.
It's probably time to go all "Mythbusters" on this issue and stick a
thermocouple in my burrs just after grinding to see how hot they get.
Maybe tomorrow.
--mike
On Sat, Dec 6, 2008 at 11:15 AM, peterz  wrote:
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5) From: Jim Gundlach
Depends on the grinder.   On the Mazzer Major if the burrs touch the  
non-grinding flat tops are all that touch.
     pecan jim
On Dec 6, 2008, at 5:02 PM, Mike Koenig wrote:
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6) From: Alchemist John
Thank you Mike.  This is what I was going to bring up.  Back a number 
of years ago, I had an extensive conversation with the owner of 
Veralab.  Long story short, he had solid conclusive evidence that 
grounds heating was occurred after significant time (hours) and was a 
result of the shaft heating via motor heat.  What they saw as a 
result of the heating was virtually a complete lack of ability for 
the grounds to produce crema in a shot, and a severe taste and aroma 
impact in all brewing methods.  Once they had this hypothesis, they 
tested it out, reproduced it repeatedly and then fixed it by using a 
belt to indirectly drive the burr shaft from the motor.  Up to a 
ludicrous 12000 rpm test, the ground never showed more than a 10-20 
rise in temperature, and no noticeable impact on crema, flavor or aroma.
How's that for myth buster data?
At 04:40 PM 12/6/2008, you wrote:
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7) From: Joseph Robertson
John,
Many thanks for this post. I knew there was an end some where out there for
this, "what I always believed to be a myth" line of thinking.
I knew there had to be some professionals/labs out there that have done
testing on this issue.
Cheers,
JoeR
On Sun, Dec 7, 2008 at 9:24 AM, Alchemist John wrote:
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8) From: Malcolm Staudinger
Make sure not to conflate heat and temperature. It's not exactly clear 
which one we're really concerned about in this thread.
Malcolm
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9) From: Angelo
For some this might be considered a myth busted, but for me I see 
that there IS some heat transferred to the beans.. In keeping with 
the nature of many folks on this list, it would probably be best to 
keep my Rocky and my beans in the fridge overnight so that there will 
be a minimum of heat transference during the 15-20 seconds it takes 
to grind my ~20 grams for my morning cup.... After all, 10-20 degrees 
is not nothing, ya know...
A
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10) From: raymanowen
If I chuck up a burr cutter in my 30000 rpm 1500watt router motor, coffee
beans will not willingly enter between the spinning burr and the permanent
orphan upper burr from my former Solis Maestro grinder.
Even when I slow it with a dimmer, I'm busted because the Solis and all
derivative (there are MANY!) grinders use two stage comical burrs. My burr
cutter was not comical and had no second stage, so no adjustment.
The grind adjustment tends to be controlled by the speed but it is very
erratic.
Wercs the heat testing- just flash freeze the beans and make cold grounds,
right into your filter.
The Mazzer Major draws about 600 watts when grinding, and energy can be
neither created nor destroyed in the grinder. It's the reason chips are
smoking when cut by a lathe or broach machining a part.
Big wood saws are often belt driven and create a tremendous draft when
spinning. Cut a 4X4, stop the blade and feel the teeth. The heat didn't come
from the motor or drive shaft.
Cheers, Mabuhay and magandang Gabi -RayO, aka Opa!
Why test anything, when you already know the results? Figures don't lie,
but...
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11) From: Luis Zaman
I think I need to go ask some of my Physicist friends to clarify this  
a bit!
There are several contributing factors to the heat, it is true.  
Obviously there is the motor running, and the friction incurred when  
cutting the bean.
The interesting points raised here are if the bean has potential  
energy in its structure, like little bubbles exploding when they are  
poked that contribute to the heat produced. And of course, if the  
burrs are incurring enough heat that it is transfered to the bean. The  
other possibility is that the above case is causing the grinds to heat  
up without attributing it directly to the burrs.
I wonder if physicists would even be able to help, given all these  
possibilities!
Interesting points continue to be brought up though!
Luis
On Dec 7, 2008, at 6:16 PM, raymanowen wrote:
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12) From: Mike Koenig
My only conclusion after reading all the comments on the Home-Barista
thread is that I can no longer risk degrading my coffee by grinding
it.  I will get a hydraulic press, and put 14g of whole beans in my
portafilter, and press them into a puck instead.
--mike
On Sun, Dec 7, 2008 at 6:08 PM, Angelo  wrote:
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13) From: Barry Luterman
One can chew the beans. However, remember to chew slowly to reduce friction
On Mon, Dec 8, 2008 at 8:01 AM, Mike Koenig  wrote:
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14) From: Alchemist John
Sure, 10-20 degrees may not be nothing, but on the other hand, is it 
something?  If there is no perceptible taste difference with 20 F, 
why bother with worrying about heating of the grounds?  Compounds are 
degrading or changing when the grounds are severely overheated but 
would be completely stable with mild heating.  They would not mildly 
degrade.  Kinetics just doesn't generally work that way.
Going the other direction, I would hazard a guess that it could even 
be beneficial to heat the grounds slightly, or more to the point, not 
chill them.  If you chill them, you will have cold beans, which will 
have to warm up even more when sub-boiling water hits them, making 
the first extraction water too cool.  Slightly warmer beans will 
instead have less distance to travel temperature wise to reach proper 
extraction temperature.
So, 10-20 may be something - if on the brewing end of the cycle.
Just food for thought.
At 03:08 PM 12/7/2008, you wrote:
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AlChemist at large
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15) From: Mike Koenig
Agreed...  If coffee was so fragile that we'd be causing degradation,
or other detrimental effects with a 10-20 deg. rise,  then brewing
would have to be kept as short as possible,  and 4 minute french press
brews at 200F would always produce flavorless dreck.
(I think Angelo was being sarcastic though).
--mike
On Tue, Dec 9, 2008 at 7:49 AM, Alchemist John
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16) From: Joseph Robertson
We here on this list, including me, tend to get too propeller head on the
science of coffee. If we would / could use our taste buds more i.e. right
brain and less of the left side of reason I think answers would be easier to
come by.
Less is more. Use the cup. Test by taste. etc. etc. It's all been said
before here.
JoeR
On Tue, Dec 9, 2008 at 5:39 AM, Mike Koenig  wrote:
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17) From: Joseph Robertson
I know RayO,
What is the fun in that..........................
Joe
On Tue, Dec 9, 2008 at 8:38 AM, Joseph Robertson wrote:
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18) From: Angelo
Moi? Sarcastic?... Well, a little I guess . I thought the bit about 
consulting the  stars/planets should have given it away. I guess I 
should have used the "irony alert" (i!)...
But, really, I was kinda making fun of the people who take what 
should be an enjoyable activity and make it into an obsessional 
search for the Holy Grail. I suppose that's the enjoyable part for 
them. Oh, well...
A
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19) From: Alchemist John
Damn, I completely missed the stars/planets bit.  Yes, (i') next time. :)
At 09:24 AM 12/9/2008, you wrote:
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