HomeRoast Digest


Topic: altitude (2 msgs / 56 lines)
1) From: Doug Sammons
Yes its Doug, sorry,my Eudora allows different boxes and I accidently was 
sending from my daughters.
Dave I know some guys at Chem Abstracts and I'm a 82 alumni from OSU but 
anyway why haven't you straightened these guys out about the boiling point.
For most of us water boils at about 212F because its about one atmosphere 
of pressure, the higher the altitude, less pressure, so water boils at a 
lower temperature maybe as much as 20F lower depending on your 
altitude.  Remember no matter how much heat you add boiling water stays at 
the same temperature until the waters gone.
So what, well during the roast the water has to boil off or evaporate and 
when it does it cools the beans, a little anyway and so the temperature 
curve has to have a modest plateau while the water is evaporating, when its 
gone the temp will continue to rise.  So does the major flavor chemistry 
happen before or after the water leaves? if it happens during then 
prolonging the boiling time will help.  But of course the temp this happens 
at dictates the kind of chemistry that can happen and at higher altitudes 
this is a lower temperature.  So, do beans roasted at higher altitudes make 
better coffee? Will hydrating the beans a little before roasting help?, I 
understand they are dry at about 10% moisture which is pretty dry, what if 
you bring it up to 15% by keeping open in a frig where they can pick up 
some humidity (just before they are roasted so they don't spoil)?
With all those extra beans no wonder some of the Farms are trying to sell 
their beans directly on the internet, especially if they have already 
auctioned off the good ones and need to sell the rest?
Doug
At 09:01 AM 9/25/03 -0400, you wrote:
<Snip>

2) From: Ken Mary
<Snip>
Coffee probably has water in 3 conditions. Free water (which will boil off
at its normal bp for your elevation), adsorbed or surface bonded (which
needs temps higher than the bp to drive it from the surface), and trapped in
the cells (which needs a higher temp just to break the cell wall to release
the water). My guess is that there is very little free water, that is why we
do not see a plateau at the bp. Some of the remaining water may be present
at pyrolysis temps and able to affect the flavor chemistry.
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