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TonyVan
Senior Member


Joined: 24 May 2010
Posts: 276
Location: Pacific Northwest
Expertise: I love coffee

Espresso: GS/3, La Pavoni
Grinder: Macap M7K, Rocky
Drip: Kone
Posted Sun Jun 3, 2012, 4:00pm
Subject: Re: Calling All VST Refractometer Owners - A Brewing Challenge:
 

andys Said:

...Have you tried a dark roast? Starbucks might have just what you need. I think it is fairly easy to get extraction numbers much higher with a dark roast compared to your typical bleeding edge light roast.

Posted May 17, 2012 link

Andy, do you have a sense how much of this difference might be explained simply by lower moisture content - therefore lower relative mass - possibly in dark roasts?  I can remember a couple very dark roasts where, given the same measure in grams, the volume of the beans is noticably greater than lighter roasts.  

If the heavy roasting bakes out more water, there is actually more "coffee matter" per gram of some dark versus light roasts.  If true, then using a given mass of such a dark roast would essentially mean you're using more coffee matter and therefore the extraction ratio could be higher for that reason alone - with less or even nothing to do with true extraction characteristics themselves.
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andys
Senior Member
andys
Joined: 10 May 2003
Posts: 845
Location: NY
Expertise: Just starting

Espresso: Speedster, Londinium 1
Grinder: EK-43,Robur, HG One, M3
Vac Pot: Yama
Drip: various
Roaster: PIDed Popper
Posted Sun Jun 3, 2012, 8:21pm
Subject: Re: Calling All VST Refractometer Owners - A Brewing Challenge:
 

TonyVan Said:

Andy, do you have a sense how much of this difference might be explained simply by lower moisture content - therefore lower relative mass - possibly in dark roasts?  I can remember a couple very dark roasts where, given the same measure in grams, the volume of the beans is noticably greater than lighter roasts.  

If the heavy roasting bakes out more water, there is actually more "coffee matter" per gram of some dark versus light roasts.  If true, then using a given mass of such a dark roast would essentially mean you're using more coffee matter and therefore the extraction ratio could be higher for that reason alone - with less or even nothing to do with true extraction characteristics themselves.

Posted June 3, 2012 link

I believe the moisture content of roasted beans is quite low -- two or three percent for medium-roasted beans, according to Illy.

If medium roasts contain 2.5% moisture, and dark roasts 1.5% moisture (just making up possible numbers), that difference would produce very little change in the computed extraction yields. I once asked Vince if any of the previous coffee scientists (such as Lockhart) had felt it necessary to compensate for bean moisture content. To his knowledge, they had not.

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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Netphilosopher
Senior Member


Joined: 14 Jan 2011
Posts: 1,602
Location: USA
Expertise: Just starting

Posted Mon Jun 4, 2012, 5:55am
Subject: ...
 

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Netphilosopher
Senior Member


Joined: 14 Jan 2011
Posts: 1,602
Location: USA
Expertise: Just starting

Posted Fri Aug 17, 2012, 8:27pm
Subject: ...
 

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