HomeRoast Digest


Topic: Grinder heat generation (4 msgs / 90 lines)
1) From: Jack Berry
Cupping is the only sure way, but I found this interesting.
According to a product comparison chart on one of the equipment sites the
faster speeds produce the lowest temperatures when comparing these 3
grinders. Does it mean anything about cup quality; who knows?
Grinder		Rocky		Innova Flat		Mazzer Mini
Burr speed		1725		700			1600
Temp w/beans	77		83			76
Temp no beans	61		73			62

2) From: Ken Mary
Maybe a more correct analysis of this data is to assume the "no beans" temp
is the starting temp, and use the temp *change* as the value of interest.
This yields the following:
Burr speed    700    1600    1725
temp change   10     14      16
Faster speed produces a higher temperature change. If there is any effect on
cup quality, it may be a greater loss of volatiles using a higher speed
grinder if the grounds are left in the hopper, rather than brewed in a few
minutes or less.
--
----------
<Snip>
<Snip>
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

3) From: Dan Bollinger
Good eyes, Ken!  Apparently, the higher speed results in more heat
transferred.  This is inline with the formula F=mV(2) if we assume that the
applied mechanical force is eventually converted into heat.  If the overall
temperature of the bean is due to higher speed grinding, then what is the
increase in temperature where the bean meets the grinder edge?  I would
expect it to be an even greater temperature difference.  The question still
remains, is this going to effect the cup?  Dan
<Snip>
temp
<Snip>
on
<Snip>
the
<Snip>
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

4) From: Dan Bollinger
<Snip>
Interesting.  Someone thought it was important enough to measure. Again,
this measures the overall temperature, and not the cutting temperature.  I
assume that the beans were the same temperature before the test?  Notice
that the Innova is a hotter running machine. The motor must run hotter or be
nearer the grinding compartment. This means that the heat is coming from the
Innova's motor and not from the grinding.  These temperatures don't bother
me.  After all, the highest temperature is only 83.  Some kitchens are this
temperature!  What I'm more concerned about is the high pressure/energy
imparted at the contact point of blades and bean. The Rocky (at 1725 rpm)
imparts over 6 times the energy to the bean than the Innova (700 rpm).
F=mV(2)  What does this do to volatiles in the region of the impact?  I
don't know!  Dan
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast


HomeRoast Digest