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Topic: CO2 Foam Density and Texture? (7 msgs / 166 lines)
1) From: sci
I have observed an interesting phenomenon lately. When I pour hot water over
the coffee grounds, the foam density and texture differs according to roast
degree. For example, City and City+ roasts produce a thick creamy luscious
foam from the release of the CO2. It is light colored with bubbles so tiny
they are invisible. At times it almost reminds me of whip cream it is so
thick and smooth.
 Contrast this with the foam that emerges from  FC+ and V roasts. This foam
is coarse and vigorous with bigger bubbles that pop quickly. There is
overall less density. It reminds me of the foam that comes from a Coke
poured over ice quickly. The process is ugly compared to the creamy texture
of the C and C+ foams.
So is there anybody here that understands this phenomenon and why the foams
have such different textures?  Have ya'll observed the same thing, or
otherwise?
 If you want to observe this try the AP inverted method with several
different roast levels.
Ivan
Coffee Animal
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2) From: Bob Hazen
Ivan,
This is timely!  In the last couple days, I've noticed this with some 
Sulawesi I roasted to C, maybe C+.  I generally roast darker and typically 
see the coarser, darker foam you describe.  The lightly roasted Sulawesi 
produced lighter colored, "creamy-looking" foam.  About the time I started 
with this batch of Sulawesi, I swapped out a single-hole spray head for the 
multi-hole sprayhead on my TV.  I had attributed the change in foam to the 
spray-head change, but I bet you're right; it's likely the roast level.  I 
feel an experiment "brewing."
Bob

3) From: raymanowen
This must be similar to the development of Crema when espresso brewing.
There has been an Old Wive's Tale that "an espresso roast is always dark-
Vienna(+)"
Not to belabor the espresso roast fiction, but if The Interesting Phenomenon
were at work, dark roasts should have long since "Outed" themselves as
counter productive of crema. My roast level of choice with the HG/BM set-up
and the Grand Slam cooler has been FC+ to V.
Maybe the cooling was so fast that the roast actually stopped before the
majority of the beans reached the roast level of the indicators I was
watching and hearing. Who'd a thunk Ray doesn't like Vienna? Don't pass it
around...
Fresh roasted (Within 10 days for Horse, et al.), fresh ground coffee beans
have always yielded almost Volcanic coffee bloom during drip brewing. Had to
be careful using the TechniVorm to brew Steinways using a conditioned basket
and dribbling boiling water into it. (Boiling = 201 F; comes with the
elevation and taxes)
Moka pot is more fun, less fussy.
Cheers, Mabuhay and Magandang Umaga -RayO, aka Opa!
Sure hope the winning candidate supports this altitude's 201 F boiling
point!
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4) From: David Martin
I never picked up on the difference in foam being related to roast
level. I have noticed that certain types of beans have the
unattractive foam you describe; in particular, Monsooned Malabar. From
this I concluded that the way the beans are processed has something to
do with it.
 -Dave
On Tue, Oct 28, 2008 at 5:36 PM, sci  wrote:
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5) From: Seth Grandeau
Just today I was making coffee in my AP, using a Vienna roasted monkey
blend, and I was noticing the darker, "rougher" textured foam, compared to
other coffees (which I roast lighter).  Good post!
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6) From: Leo Zick
so you prefer a silky foam with a super acidic mouthtaste, over something
more dense but with more chocolates, caramels, etc?
when im making an americano, i dont mind lighter roasts, but this week i
tried pulling a shot in my hx with a c+/fc- roast and it was like drinking
lemonade :p
though, this roast level works much better in my lever, it REALLY brings out
the flavors, where darker roasts just taste, well, darker.
On Wed, Oct 29, 2008 at 4:27 AM,  wrote:
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7) From: sci
Thanks for confirming this Seth.
I've been watching the foam closely. I keep light and dark roasts. The foam
density, color, texture, etc follow the profiles I mentioned before. We know
that CO2 is released. But there maybe some other gases too. It is
interesting to me that the main difference is just the roast level.
Ivan
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Date: Thu, 30 Oct 2008 14:27:49 -0400
From: "Seth Grandeau" 
Subject: Re: [Homeroast] CO2 Foam Density and Texture?
To: homeroast
Message-ID:
       <1b43ec7e0810301127y5300bb67j2b98b3fb91392ad9>
Content-Type: text/plain; charsetO-8859-1
Just today I was making coffee in my AP, using a Vienna roasted monkey
blend, and I was noticing the darker, "rougher" textured foam, compared to
other coffees (which I roast lighter).  Good post!
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