HomeRoast Digest


Topic: OT +Low Acid Coffee (30 msgs / 1454 lines)
1) From: Leo Zick
This is an *almost* accurate definition.  PH measures the strength of the
acidity. It isn't a different type of acidity.  It never sees the basic side
of the PH scale though, that would be scary!  I don't even think its
possible to have a wine reach a PH of near 7, forget about above (basic) it!
A low ph is a higher strength TA, and a high PH is a lower strength TA.
Ideally, you want a lower PH, but too low could indicate your TA is so high
that your wine will taste like lemonade, very tart! :p
Ive never seen or tried to make charts with PH vs TA, so I don't know that
there is a linear correlation, or if a crossover point exists.

2) From: Tom Ulmer
What exactly is titratable acidity? To me this indicates some determination
of the acids present not necessarily the overall PH of the substance.

3) From: Andy Thomas
I found this definition at:http://tinyurl.com/3ytdtt• pH – the e=
quilibrium measure of hydrogen
ion concentration in a juice or wine
•=
 Titratable acidity measures the total amount
of protons available in a j=
uice or wine, and
is expressed as g/L tartaric acid equivalent
Thank=
s, Leo for the clarification. True, all wine is acidic -- usually between p=
H 3.0 and 4.0. The pH scale is logarythmic, however, meaning pH 3.0 is 10 t=
imes as acidic as pH 4.0. One of these days I will test the pH and TA of co=
ffee and try to make sense of the results. :-)
----- Original Messa=
ge ----
From: Tom Ulmer 
To: homeroast=
ias.com
Sent: Saturday, February 10, 2007 7:01:45 AM
Subject: RE: OT +L=
ow Acid Coffee
What exactly is titratable acidity? To me this indic=
ates some determination
of the acids present not necessarily the overall =
PH of the substance.

4) From: Leo Zick
I just measured some misty valley, at a C to C+ roast, with one day rest.
It has milk in it, which may skew results (slightly more basic) a bit.
PH was 5.6 at 106F.  slightly acidic, as expected from coffee.
Without milk, it should be lower, and if I roasted darker, it should raise a
bit.
A more 'sophomoric' definition of Titratable Acidity is the amount of acid
as a percentage of volume.  In wine, the dominant acid is tartaric (yep,
think cream of tarter!). Like andy said, its typically 0.55-0.75%, or
55-75g/L
So, PH is the strength of the acid, and TA is the sharpness, or taste, it
gives.
I have no desire to titrate my coffee, red wine is dark (ie, a pain) enough.
:p

5) From: raymanowen
...acidity = LOW pH number, and basicity (is that a word?) [Yes] >7
"basicity /beIsIsIti/
· n. Chemistry the number of hydrogen atoms replaceable by a base in a
particular acid."
[pH  = (-) Log of t=
he
H+ ion con (m/L)]
I know nothing- just a copy cat <http://staff.jccc.net/PDECELL/chemistry/phscale.html>On 2/10/07, Leo Zick  wrote:
<Snip>
t
<Snip>
d
<Snip>
o
<Snip>
d
<Snip>
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Might=
y
Wichita (ex- NYC Paramount) WurliTzer- 1976

6) From: Barry Luterman
This is a multi-part message in MIME format.
As in sound there is a physical world and a psychological world. We talk =
of decibels in the physical world and loudness measured in Phons in the =
psychological world. In taste the same rule applies. We speak of acidity =
in the physical world measured in Ph.

7) From: Leo Zick
This is a multipart message in MIME format.
Isn't this what I said?
Thanks for re-iterating J
From: raymanowen [mailto:raymanowen] 
Sent: Saturday, February 10, 2007 5:09 PM
To: homeroast
Subject: Re: OT +Low Acid Coffee
...acidity = LOW pH number, and basicity (is that a word?) [Yes] >7
"basicity /beIsIsIti/
. n. Chemistry the number of hydrogen atoms replaceable by a base in a
particular acid."
[ pH   = (-) Log of
the H+ ion con (m/L)]
I know nothing- just a copy cat
On 2/10/07, Leo Zick  wrote:
This is an *almost* accurate definition.  PH measures the strength of the
acidity. It isn't a different type of acidity.  It never sees the basic side
of the PH scale though, that would be scary!  I don't even think its 
possible to have a wine reach a PH of near 7, forget about above (basic) it!
A low ph is a higher strength TA, and a high PH is a lower strength TA.
Ideally, you want a lower PH, but too low could indicate your TA is so high 
that your wine will taste like lemonade, very tart! :p
Ive never seen or tried to make charts with PH vs TA, so I don't know that
there is a linear correlation, or if a crossover point exists.

8) From: raymanowen
Indeed, you did, Leo.
I was just remembering the titrations we did using Litmus paper to determin=
e
the pH of a solution. When I was an instrument tech, it blew my mind that I
was calibrating lab pH meters that gave reliable readings of 4 or 5
significant figures.
The highest quality probes were tender, but a 5 mL sample was easy to read.
It would have been all but impossible to titrate such a tiny sample with
that alleged precision.
Cheers and 73 -RayO, aka Opa!
Titratable Acidity- Not in my coffee you don't!
On 2/10/07, Leo Zick  wrote:
<Snip>
f
<Snip>
t
<Snip>
d
<Snip>
o
<Snip>
d
<Snip>
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Might=
y
Wichita (ex- NYC Paramount) WurliTzer- 1976

9) From: Leo Zick
This is a multipart message in MIME format.
Litmus is a great quick tool, a broad measurement, right?  Needless to say,
I could never ever get a good reading on red wine with it :p
From: raymanowen [mailto:raymanowen] 
Sent: Saturday, February 10, 2007 8:16 PM
To: homeroast
Subject: Re: OT +Low Acid Coffee
Indeed, you did, Leo.
I was just remembering the titrations we did using Litmus paper to determine
the pH of a solution. When I was an instrument tech, it blew my mind that I
was calibrating lab pH meters that gave reliable readings of 4 or 5
significant figures. 
The highest quality probes were tender, but a 5 mL sample was easy to read.
It would have been all but impossible to titrate such a tiny sample with
that alleged precision.
Cheers and 73 -RayO, aka Opa!
Titratable Acidity- Not in my coffee you don't!
On 2/10/07, Leo Zick  wrote: 
Isn't this what I said?
Thanks for re-iterating J 
From: raymanowen [mailto: 
raymanowen] 
Sent: Saturday, February 10, 2007 5:09 PM
To: homeroast
Subject: Re: OT +Low Acid Coffee
...acidity = LOW pH number, and basicity (is that a word?) [Yes] >7
"basicity /beIsIsIti/
. n. Chemistry the number of hydrogen atoms replaceable by a base in a
particular acid."
[   pH = (-) Log of
the H+ ion con (m/L)]
I know nothing- just a copy cat
On 2/10/07, Leo Zick  wrote:
This is an *almost* accurate definition.  PH measures the strength of the
acidity. It isn't a different type of acidity.  It never sees the basic side
of the PH scale though, that would be scary!  I don't even think its 
possible to have a wine reach a PH of near 7, forget about above (basic) it!
A low ph is a higher strength TA, and a high PH is a lower strength TA.
Ideally, you want a lower PH, but too low could indicate your TA is so high 
that your wine will taste like lemonade, very tart! :p
Ive never seen or tried to make charts with PH vs TA, so I don't know that
there is a linear correlation, or if a crossover point exists.

10) From: Justin Marquez
"alkalinity" is probably the word you seek
On 2/10/07, raymanowen  wrote:
<Snip>
he
<Snip>
)
<Snip>
hat
<Snip>
a
<Snip>
and
<Snip>
 no
<Snip>
nd
<Snip>
ted
<Snip>
<Snip>
hty
<Snip>
-- 
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)

11) From: gene nandrea
I have no idea what acids are present in coffee other that carbonic acid
from the CO2. But going back to my wine making days and looking at some old
references I see that for instance, the pH of 0.1 M Tartaric acid is 2.2 and
that of 0.1 M Lactic is 2.4. The total titratable acid is the same for the
same volume of each acid but the percieved "bite" will be greater for the
Tartaric. This is because the Tartaric ionizes more completely that the
Lactic acid. If I were asked to drink something lower in acid I would guess
that both, lower pH and total acidity would be important. BTW the pH
of 0.1M carbonic acid is
3.8 and stomach content is pH 1.0 - 3.0 (Handbook of Chemistry and Physics).
On 2/10/07, Tom Ulmer  wrote:
<Snip>

12) From: JanoMac
<Snip>
this format, some or all of this message may not be legible.
From: "Justin Marquez" 
"alkalinity" is probably the word you seek
While alkalinity is a technically ³correct² term for the level of basic pH,
that term can also mean the buffering capability of water. Because of the
increased presence of papers and discussions of environmental chemistry
these days, alkalinity is most often used in the latter manner.
So...most folks I know in Chem & Biology do use the term ³basicity;² that
is, if they wander away from simply using the term pH.
Kirk (resident proton pump inhibitor)

13) From: gene nandrea
Doing a google of "coffee chemistry" gave a wealth of information. Looking
at the sitehttp://www.coffeeresearch.org/science/sourmain.htm, is a good
start to answering some questions on coffee acidity.
On 2/10/07, Leo Zick  wrote:
<Snip>

14) From: Brett Mason
Gene - great to see you out here!
  How's the espresso?
Brett
On 2/11/07, gene nandrea <1genen> wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

15) From: Andy Thomas
Yes, a greater wealth of information than I know what to do with. Apparentl=
y the acids in coffee are much more complex than those in wine.
---=
-- Original Message ----
From: gene nandrea <1genen>
To: home=
roast
Sent: Sunday, February 11, 2007 5:46:52 PM
=
Subject: Re: OT +Low Acid Coffee
Doing a google of "coffee chemistry" =
gave a wealth of information. Looking at the sitehttp://www.coffeeresearch=.org/science/sourmain.htm , is a good start to answering some questions on =
coffee acidity. 
On 2/10/07, Leo Zick  wrote: =
This is an *almost* accurate definition.  PH measures the strength of th=
e
acidity. It isn't a different type of acidity.  It never sees the basic=
 side 
of the PH scale though, that would be scary!  I don't even think i=
ts
possible to have a wine reach a PH of near 7, forget about above (basi=
c) it!
A low ph is a higher strength TA, and a high PH is a lower strengt=
h TA. 
Ideally, you want a lower PH, but too low could indicate your TA i=
s so high
that your wine will taste like lemonade, very tart! :p
Ive ne=
ver seen or tried to make charts with PH vs TA, so I don't know that
ther=
e is a linear correlation, or if a crossover point exists.
-----Origin=
al Message-----
From: Andy Thomas [mailto:adt0611]
Sent: Satu=
rday, February 10, 2007 12:16 AM 
To: homeroast
S=
ubject: Re: +Low Acid Coffee
I don't know the answer to Jerry's orogin=
al question about low acid coffee,
but in winemaking there are two kinds =
of acidity: pH and titratable acidity. 
(BTW: acidity is represented by a=
 LOW pH number, and basicity (is that a
word?) by a high number. So pH of=
 3.5 is more acid than pH of 5.5.) TA and
pH usually correspond somewhat =
-- that is, a wine with low pH will usually, 
but not always,  have high =
titratable acidity and vice versa. TA does
correspond to an acidic flavor=
 in wine, whereas low pH may not.  I have no
idea whether any of this app=
lies to coffee or not.
----- Original Message ---- 
From: Sam Tregar=
 
To: homeroast
Sent: Friday, Feb=
ruary 9, 2007 2:30:00 PM
Subject: Re: +Low Acid Coffee 
On Fri, 9=
 Feb 2007, Tim Smith wrote:
> If Tom describes it as "bright" then odd=
s are it's fairly acidic.  However
I
> think it has to do with the roas=
t level, too.  A darker roast will tend to 
> subdue the acidity and give=
 you a little mellower flavor.  In my limited
> experience that works bet=
ter for some beans than for others.  Is he a
> City/City+ guy or does he =
go more toward the Vienna end of the range? 
I wonder if what we call =
acidity in terms of flavor is actually
correlated to low pH, which is pro=
bably what the doctor meant by
"low acid."
-sam= 
homeroast mailing listhttp://lists.s=weetmarias.com/mailman/listinfo/homeroast
To change your personal list se=
ttings (digest options, vacations, 
unsvbscribes) go tohttp://sweetmar=ias.com/maillistinfo.html#personalsettings=
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ng for earth-friendly autos?
Browse Top Cars by "Green Rating" at Yahoo! =
Autos' Green Center.http://autos.yahoo.com/green_center/=homeroast mailing listhttp://lists=.sweetmarias.com/mailman/listinfo/homeroast
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Finding fabulous fares =
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Let Yahoo! FareChase search your favorite travel sites to find =
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16) From: gene nandrea
On 2/11/07, Brett Mason  wrote:
<Snip>
I have been using the TV or vac pot lately beacuse the cold and snow have
kept me inside since I have not had a safe place to roast; I have been using
non-SM beans given at Christmas. Yesterday was warm and snow free so I did
my first roast since mid-December. The Rocky and Silvia are all cleaned and
ready to go.
Gene

17) From: Andy Thomas
For what it's worth, I tested some coffee at work today for pH and TA:  pH =
= 5.37, TA = .052 g/100ml. I'm confident the pH reading is accurate. I =
used a pH meter, properly calibrated and compensated for temp. For the TA t=
est, I did a standard titration as for wine, which measures as tartaric aci=
d evquivalent. Since coffee has little or no tartaric, the result may be me=
aningless. If it is meaningful, coffee has about 1/10th the TA of a typical=
 wine. Judging by the information in the link Gene provided below, it seems=
 the acidity of coffee is not well understood. If any of you happens to be =
an Alchemist, maybe you could clarify. :-)
----- Original Message -=
---
From: Andy Thomas 
To: homeroast=
as.com
Sent: Sunday, February 11, 2007 10:19:48 PM
Subject: Re: OT +Low=
 Acid Coffee
Yes, a greater wealth of information than I know what =
to do with. Apparently the acids in coffee are much more complex than those=
 in wine.
----- Original Message ----
From: gene nandrea <1genen@=
gmail.com>
To: homeroast
Sent: Sunday, February 1=
1, 2007 5:46:52 PM
Subject: Re: OT +Low Acid Coffee
Doing a google o=
f "coffee chemistry" gave a wealth of information. Looking at the site http=
://www.coffeeresearch.org/science/sourmain.htm , is a good start to answeri=
ng some questions on coffee acidity. 
On 2/10/07, Leo Zick  wrote: 
This is an *almost* accurate definition.  PH measur=
es the strength of the
acidity. It isn't a different type of acidity.  It=
 never sees the basic side 
of the PH scale though, that would be scary! =
 I don't even think its
possible to have a wine reach a PH of near 7, for=
get about above (basic) it!
A low ph is a higher strength TA, and a high =
PH is a lower strength TA. 
Ideally, you want a lower PH, but too low cou=
ld indicate your TA is so high
that your wine will taste like lemonade, v=
ery tart! :p
Ive never seen or tried to make charts with PH vs TA, so I d=
on't know that
there is a linear correlation, or if a crossover point exi=
sts.

18) From: raymanowen
Imagine: take a carbonated beverage or sparkling water and heat a cup of th=
e
drink to 180°F and leave it at that temperature for a few minutes. Now ha=
ve
a drink.
I admit freely that a small glass of Dr. Pepper warmed in the microwave for
a few seconds is a treat. Notice that the CO2 is coming out of solution in =
a
hurry. If you drink it at the right time, it will be a pleasant temperature
and not so Battery Acid tangy. Later, it will have all the essence of melte=
d
Jell-O.
Solutes usually dissolve more completely with agitation and elevated
temperature. CO2 is just the opposite.
Prove this. Go to the grocery. Withdraw a 2 liter Dr. Pepper from the shelf=
.
Shake the Hell out of it and unscrew the top...
"Wet cleanup in aisle 9"
Who thinks the brightness of the cup is due to dissolved CO2? Every one
would be the same, in that case.
Cheers -RayO, aka Opa!
"...the great enemy of truth is very often not the lie--deliberate,
contrived and dishonest--but the myth--persistent, persuasive--of our
forebears. We enjoy the comfort of opinion without the discomfort of
thought."* **- -**John F. *Kennedy*, Yale, 6-11-1962*

19) From: Floyd Lozano
i'm not a chemist but allow me to talk out of my backside until one comes
along and says otherwise!  it could well be that there is something else in
the coffee to which CO2 likes to bind that keeps it in solution more readil=
y
than say, dr pepper, where it appears to be simply pressure that keeps the
gas in solution.  i can't prove that of course, but this is the internet, i
don't have to!
On 2/12/07, raymanowen  wrote:
<Snip>
Now
<Snip>
on
<Snip>

20) From: Larry Johnson
CO2 in solution also is pretty bitter. Try this for an experiment: find one
of those whipped cream makers that uses the little NO2 cartridges. Instead
of the NO2, use one of the CO2 cartridges intended for BB/pellet guns (they
are the same size, etc. At least they once were.). Make some whipped cream
with the CO2 instead of the NO2. You will find it too bitter to be
palatable.
-- 
Larry J (Lilboybrew)
"The truth does not change according to our ability to stomach it."
  - Flannery O'Connor
On 2/13/07, Floyd Lozano  wrote:
<Snip>
in
<Snip>
ily
<Snip>
e
<Snip>
 i
<Snip>
f
<Snip>
. Now
<Snip>
tion
<Snip>

21) From: Justin Marquez
On 2/12/07, raymanowen  wrote:
<Snip>
  ...or... jon the way home from the store just have one to get loose
from those stupid plastic bags they use at Kroger and roll around
there in the trunk and then have your spouse open it a few minutes
later at home...
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)

22) From: Cameron Forde
Hi Larry, Floyd, and Ray,
As you describe it, this is a soda siphon, and not at all too bitter
to drink.  They are used to make carbonated water for mixed drinks
(eg., scotch and soda).  For a 1L soda siphon, the little CO2
cartridges are 8g instead of the 12g used for BB guns.  Floyd is right
when he says that it is mainly the pressure that keeps the CO2 in
solution, though there is some acid-base chemistry going on, too.  The
CO2 combines with water to form carbonic acid, which exists mostly as
bicarbonate anion (HCO3-) around pH5.  Ray is right when he says that
the solubility of in water drops as the water is heated.  This is a
general property of all gases in solution.  If your espresso is
tickling your nose, your coffee is too fresh!
Cameron
On 2/13/07, Larry Johnson  wrote:
<Snip>
ne
<Snip>
d
<Snip>
ey
<Snip>
m
<Snip>
es
<Snip>
in
<Snip>
ily
<Snip>
e
<Snip>
 i
<Snip>
 of
<Snip>
Now
<Snip>
ve
<Snip>
on
<Snip>
ne
<Snip>
-- 
-- ceforde

23) From: Larry Johnson
Or, try this: Take two equal 2-liters of the same soft drink. Chill one and
leave the other at room temp. Open each and notice which one makes the
louder hiss.
<Snip>
The one at room temp, because the colder one will have allowed more CO2 into
solution and will outgas less when opened. CO2 dissolves more readily into
cold liquid than into warm liquid. This is the reason you should chill your
2-liter beverages before opening; they last longer before going flat. It's
also why I think there's little or no CO2 in brewed coffee.
How about someone brew some coffee with a toddy and compare to some brewed
hot?
-- 
Larry J (Lilboybrew)
"The truth does not change according to our ability to stomach it."
  - Flannery O'Connor
On 2/13/07, Justin Marquez  wrote:
<Snip>

24) From: Leo Zick
This is a multi-part message in MIME format.
im going to have to disagree.
a popular method of decaffeination is via blasting co2 laden water over =
the
beans. if its so happy binding with them, why doesnt it do so during =
this
process?
 
simple explanation - i think the roasting process causes a reaction that
releases simple carbohydrate bonds which produce co2 into the =
atmosphere.
 
carbon and oxygen create carbohydrates.  (hence, duh, hydrated-carbo).
remember, coffee is a plant, and it uses co2 for photosynthesis.  some =
co2
may remain within the bean (we dont expell ALL our oxygen do we? some =
stays
in the blood, keeps it alive), and when the bean is roasted, the excess =
co2,
some in the form of a gas, and some in the form of stored carbs, are
released, both during roasting (gas) and after (broken down carbs).
 
this may also be why, if you freeze roasted beans with too much air =
around
them, they appear to frostbite.  frozen co2 is, as we know it, dry ice.
 
so, yes, im sure there is something else in the coffee bean that co2 =
likes
to bind to, its 'lungs'. :p  
From: Floyd Lozano [mailto:fplozano] 
Sent: Tuesday, February 13, 2007 8:47 AM
To: homeroast
Subject: Re: OT +Low Acid Coffee
i'm not a chemist but allow me to talk out of my backside until one =
comes
along and says otherwise!  it could well be that there is something else =
in
the coffee to which CO2 likes to bind that keeps it in solution more =
readily
than say, dr pepper, where it appears to be simply pressure that keeps =
the
gas in solution.  i can't prove that of course, but this is the =
internet, i
don't have to! 
On 2/12/07, raymanowen  wrote: 
Imagine: take a carbonated beverage or sparkling water and heat a cup of =
the
drink to 180°F and leave it at that temperature for a few minutes. Now =
have
a drink. 
I admit freely that a small glass of Dr. Pepper warmed in the microwave =
for
a few seconds is a treat. Notice that the CO2 is coming out of solution =
in a
hurry. If you drink it at the right time, it will be a pleasant =
temperature
and not so Battery Acid tangy. Later, it will have all the essence of =
melted
Jell-O. 
Solutes usually dissolve more completely with agitation and elevated
temperature. CO2 is just the opposite. 
Prove this. Go to the grocery. Withdraw a 2 liter Dr. Pepper from the =
shelf.
Shake the Hell out of it and unscrew the top... 
"Wet cleanup in aisle 9"
Who thinks the brightness of the cup is due to dissolved CO2? Every one
would be the same, in that case.
Cheers -RayO, aka Opa!
"...the great enemy of truth is very often not the lie--deliberate,
contrived and dishonest--but the myth--persistent, persuasive--of our
forebears. We enjoy the comfort of opinion without the discomfort of
thought." - - John F. Kennedy, Yale, 6-11-1962   

25) From: Leo Zick
This is a multi-part message in MIME format.
or just do the infamous pepsi and mentos trick. got me what it has to do
with coffee, but since we are talking soda here..  
From: Larry Johnson [mailto:lilboybrew] 
Sent: Tuesday, February 13, 2007 1:19 PM
To: homeroast
Subject: Re: OT +Low Acid Coffee
Or, try this: Take two equal 2-liters of the same soft drink. Chill one and
leave the other at room temp. Open each and notice which one makes the
louder hiss. 
 
<Snip>
The one at room temp, because the colder one will have allowed more CO2 into
solution and will outgas less when opened. CO2 dissolves more readily into
cold liquid than into warm liquid. This is the reason you should chill your
2-liter beverages before opening; they last longer before going flat. It's
also why I think there's little or no CO2 in brewed coffee. 
 
How about someone brew some coffee with a toddy and compare to some brewed
hot?
 
-- 
Larry J (Lilboybrew)
"The truth does not change according to our ability to stomach it."
  - Flannery O'Connor 
On 2/13/07, Justin Marquez  wrote: 
On 2/12/07, raymanowen < raymanowen
 > wrote:
<Snip>
shelf. 
<Snip>
...or... jon the way home from the store just have one to get loose
from those stupid plastic bags they use at Kroger and roll around
there in the trunk and then have your spouse open it a few minutes 
later at home...
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)

26) From: Floyd Lozano
good question!  From what I have read, this process is called 'supercritica=
l
CO2 decaffeination'.  At high pressure (200-300 times atmosphereic) CO2 act=
s
as a supercritical fluid, which i guess means, both like a fluid and a gas.
it can get in deep into the bean and attract the little caffeine molecules
out but leave the larger flavor compounds intact.
here's a slightly better (hah) description of the processhttp://www.chemistry.org/portal/a/c/s/1/feature_ent.html?id=416ac19ece171=1d5f2944fd8fe800100
On 2/13/07, Leo Zick  wrote:
<Snip>
2
<Snip>
ys
<Snip>
o2,
<Snip>
d
<Snip>
s
<Snip>
in
<Snip>
ily
<Snip>
e
<Snip>
 i
<Snip>
f
<Snip>
. Now
<Snip>
tion
<Snip>

27) From: Cameron Forde
Hi Leo,
Not entirely sure that I know what it is you are disagreeing with, but
I'll try my hand at explaining how CO2 acts as a solvent to draw the
caffeine from the coffee bean and not remain bound.  The key is the
supercritical part: under the right conditions of temperature and
pressure CO2 can be made to behave like a fluid (not quit a liquid and
not quite a gas).  The properties of the fluid (eg nonpolar and small
size) make it a good solvent for removing caffeine (among other
things) from the coffee bean.  The nice thing about this solvent is
that by returning to atmospheric pressure it all boils away (unlike
the methylene chloride or ethyl acetate extractions).  The CO2
released after roasting coffee doesn't come from this process but from
degradation (aging) that carries on after the roasting is complete.
This is the part where my understanding of the chemistry stops.  I
know that some carboxylic acids will decarboxylate (give off CO2) when
heated, but I don't understand why this or similar processes continue
after roasting.  I'm sure there are papers in the literature that
explore this, and if I find some time I'll have a look.
Cameron
On 2/13/07, Leo Zick  wrote:
<Snip>
-- 
-- ceforde

28) From: Leo Zick
I agree with you. I was using co2 decaffeination as an example that there
isnt 'something in coffee that co2 likes to bind to, and that's why its
there', per Floyd's comment.

29) From: Justin Marquez
On 2/13/07, Floyd Lozano  wrote:
<Snip>
Supercritical fluids are at pressures and temperatures above the
"critical point" - that point being a temperature above which you
can't make it be a real liquid and the pressure accompanying that
temperature that made it a liquid just slightly cooler.
Supercritical fluids are still somewhat compressible (like a gas) and
are as dense as a liquid phase.
Supercritical CO2 is a phenomenal solvent, particularly for oils.  It
is widely used in some areas of the country (West Texas) for enhanced
oil recovery from near-dead oil wells. It reduces the viscosity of the
oil and flushes it out of the underground rock.
There was at one time a process for removing cooking oil from potato
chips using supercritical CO2. I think it has been replaced by baking
the chips.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)

30) From: Leo Zick
I think its also used on offshore wells


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