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Date: 09 Jun 2006 11:23:54
From: jim schulman
Subject: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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This has been cited as one of the perfidious things mass roasters do
to make Robusta palatable. Usually the implication is that steaming
will kill all the taste, which is an improvement as far as robusta is
concerned. But the real story is a bit different ...
How about the oft repeated fact that pH, sourness, and tasters acidity
have little in common. Here the implication is that acidity, as
enjoyed or cursed by us drinkers is not measurable by scientific
means.
I recently dug up a coffee science book at Powell's, the local 2nd
hand bookstore, "Coffee: Recent Developments," Clarke & Vitzthum
editors. This is not as good as the Illy book, but it does a much
better job of linking chemistry and technology with taste. I haven't
slogged through the hard parts yet, but here's some good stuff from
the kindergarden sections.
Steaming green coffee was developed as a way of speeding up the early
roast. The drawback was that it **raised** the acidity of the beans to
beyond acceptable levels. So now it is mainly used for Robustas, where
extra acidity is a bonus. Roasting coffee with high temperature steam
remains an active area of research.
And acidity ... pH does not correlate well with acidity ratings by
cuppers. However, this is because there's enough buffers in coffee to
make pH a bad measure of acidity. Measuring acidity by titration to
endpoint pH 6 * correlates with cupper's acidity very well (R-square
of 0.91). And more acidity will always taste more sour, but can be
transformed into pleasantly tart by a swet coffee.
* add a solution to coffee that changes color at pH 6, then drip in an
alkali and measure how much it takes to get to the color change. Just
like hardness tests, titration is more accurate than using a test
strip.
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Date: 12 Jun 2006 02:14:33
From: DavidMLewis
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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Brewer Bob wrote:
> Thanks for the info Jim, but what does it all mean?....
>
> "RO water will make even robusta look bad.
> Does that mean Robusta has a higher acidic level on a pH level and needs
> the alkaline(Residual Alkalinity versus temporary hardness which are
> mainly composed of bicarbonates) buffering agents in harder water to
> balance the acidity to mellow their percieved acidity?
>
> "The Silvia is not a commercial machine, no matter how hard you owners
> pretend"
>
> Well I try not to pretend about anything and you can take me pretty much
> at face value but, please explain this statement... I value your input.
>
Jim, you should be aware, wrote the "Insanely Long Water FAQ". To give
you the short form: R/O, or any other water that's too pure, doesn't
extract either coffee or tea very well, for reasons I'm not sure anyone
fully understands. What is clear is that the coffee will taste flat.
The best levels seem to vary somewhat with the taster, but fall in the
range of 150 ppm hardness and 250 ppm or so TDS. That's enough to scale
a machine slowly, and commercial machines are a pain to descale, so
people with commercial machine usually compromise with water at about
50 ppm hardness (which you can supply, by the way, by putting a calcite
filter after your R/O system). With the Sylvia, descaling is fairly
easy, so you can use water that's closer to the ideal hardness, if you
can easily get it, without worry.
Best,
David
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Date: 12 Jun 2006 00:17:09
From: anthony
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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And forgot to mention:
The Illy book is available here:
http://www.sweetmarias.com/prod.book.poster.misc.shtml
This includes a link to a downloadable version of the book's intro.
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Date: 12 Jun 2006 07:20:43
From: Brewer Bob
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus
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Thanks Anthony!
Brewer Bob
anthony wrote:
>And forgot to mention:
>The Illy book is available here:
>http://www.sweetmarias.com/prod.book.poster.misc.shtml
>This includes a link to a downloadable version of the book's intro.
>
>
>
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Date: 12 Jun 2006 00:06:54
From: anthony
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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>
> RO water will make even robusta look bad. The Silvia is not a
> commercial machine, no matter how hard you owners pretend, and It only
> takes about an hour a year to keep it descaled. Just run 50% lemon
> juice or the citric acid equialent through it 4 times a year.
>
And what is RO water? I'm using plain tap water, letting it stand
overnight to remove chlorine though air-contact, and it tastes just
fine. I guess I should get a PH tester, but I suspect the water here in
the Blue Mountains (New South Wales, Australia, just a couple of hours
from Sydney) is pretty soft. Anyone have a quick way to gauge water
hardness/softness outside of a chemical lab?
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Date: 12 Jun 2006 09:30:21
From: Tony Verhulst
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus
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> And what is RO water?
Reverse Osmosis. Think of it as distillation without having to boil the
water. It's an excellent way to remove impurities. Much of bottled water
you buy has been run though RO.
Tony V.
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Date: 12 Jun 2006 06:23:09
From: Brewer Bob
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus
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jim schulman wrote:
>This has been cited as one of the perfidious things mass roasters do
>to make Robusta palatable. Usually the implication is that steaming
>will kill all the taste, which is an improvement as far as robusta is
>concerned. But the real story is a bit different ...
>
>How about the oft repeated fact that pH, sourness, and tasters acidity
>have little in common. Here the implication is that acidity, as
>enjoyed or cursed by us drinkers is not measurable by scientific
>means.
>
>I recently dug up a coffee science book at Powell's, the local 2nd
>hand bookstore, "Coffee: Recent Developments," Clarke & Vitzthum
>editors. This is not as good as the Illy book, but it does a much
>better job of linking chemistry and technology with taste. I haven't
>slogged through the hard parts yet, but here's some good stuff from
>the kindergarden sections.
>
>Steaming green coffee was developed as a way of speeding up the early
>roast. The drawback was that it **raised** the acidity of the beans to
>beyond acceptable levels. So now it is mainly used for Robustas, where
>extra acidity is a bonus. Roasting coffee with high temperature steam
>remains an active area of research.
>
>And acidity ... pH does not correlate well with acidity ratings by
>cuppers. However, this is because there's enough buffers in coffee to
>make pH a bad measure of acidity. Measuring acidity by titration to
>endpoint pH 6 * correlates with cupper's acidity very well (R-square
>of 0.91). And more acidity will always taste more sour, but can be
>transformed into pleasantly tart by a swet coffee.
>
>
>* add a solution to coffee that changes color at pH 6, then drip in an
>alkali and measure how much it takes to get to the color change. Just
>like hardness tests, titration is more accurate than using a test
>strip.
>
>
Hey Jim,
This is fascinating. I'm mostly a lurker but, really enjoy the plethora
of info from all of you veterans. I am also a brewer of beer and very
intimate with water chemistry. I almost feel guilty with using RO water
in my new PID'd Silvia(Thanks Dave) but, I have medium hard water here
in Livermore(S.F. East bay area) so I want to avoid scale build up in
the boiler.
You are talking about the Illy book and I've been to their website and
can't find it(the book) so, any direction with that would be cool.
I also got a pound of Indian Robusta from SM's a while back to blend
with my dry processed Brazils and I can't tell the difference in crema
when I use it at ~ 15%. What gives?
And speaking of pH ...I guess I should break out my pH meter and test
my espresso. What is an acceptable pH level range?
Brewer Bob
http://www.geocities.com/bob_girolamo
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Date: 12 Jun 2006 01:45:15
From: jim schulman
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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On Mon, 12 Jun 2006 06:23:09 GMT, Brewer Bob
<bob-girolamo@nospam.sbcglobal.net > wrote:
>You are talking about the Illy book and I've been to their website and
>can't find it(the book) so, any direction with that would be cool.
>I also got a pound of Indian Robusta from SM's a while back to blend
>with my dry processed Brazils and I can't tell the difference in crema
>when I use it at ~ 15%. What gives?
RO water will make even robusta look bad. The Silvia is not a
commercial machine, no matter how hard you owners pretend, and It only
takes about an hour a year to keep it descaled. Just run 50% lemon
juice or the citric acid equialent through it 4 times a year.
>And speaking of pH ...I guess I should break out my pH meter and test
>my espresso. What is an acceptable pH level range?
The chem book said it's a waste of time, since the readings don't
correlate well with anything in the taste -- but it should be around 5
to 5.5, iirc
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Date: 12 Jun 2006 07:18:54
From: Brewer Bob
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus
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Thanks for the info Jim, but what does it all mean?....
"RO water will make even robusta look bad.
Does that mean Robusta has a higher acidic level on a pH level and needs
the alkaline(Residual Alkalinity versus temporary hardness which are
mainly composed of bicarbonates) buffering agents in harder water to
balance the acidity to mellow their percieved acidity?
"The Silvia is not a commercial machine, no matter how hard you owners
pretend"
Well I try not to pretend about anything and you can take me pretty much
at face value but, please explain this statement... I value your input.
Brewer Bob
jim schulman wrote:
>On Mon, 12 Jun 2006 06:23:09 GMT, Brewer Bob
><bob-girolamo@nospam.sbcglobal.net> wrote:
>
>
>
>>You are talking about the Illy book and I've been to their website and
>>can't find it(the book) so, any direction with that would be cool.
>>I also got a pound of Indian Robusta from SM's a while back to blend
>>with my dry processed Brazils and I can't tell the difference in crema
>>when I use it at ~ 15%. What gives?
>>
>>
>
>RO water will make even robusta look bad. The Silvia is not a
>commercial machine, no matter how hard you owners pretend, and It only
>takes about an hour a year to keep it descaled. Just run 50% lemon
>juice or the citric acid equialent through it 4 times a year.
>
>
>
>>And speaking of pH ...I guess I should break out my pH meter and test
>>my espresso. What is an acceptable pH level range?
>>
>>
>
>The chem book said it's a waste of time, since the readings don't
>correlate well with anything in the taste -- but it should be around 5
>to 5.5, iirc
>
>
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Date: 12 Jun 2006 16:30:59
From: jim schulman
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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On Mon, 12 Jun 2006 07:18:54 GMT, Brewer Bob
<bob-girolamo@nospam.sbcglobal.net > wrote:
>>"RO water will make even robusta look bad.
>Does that mean Robusta has a higher acidic level on a pH level and needs
>the alkaline(Residual Alkalinity versus temporary hardness which are
>mainly composed of bicarbonates) buffering agents in harder water to
>balance the acidity to mellow their percieved acidity?
>
No, low mineral water creates slime in the puck and interferes with
extraction and crema formation. This effect disappears at around 30 to
40 TDS, and if your RO's rejection rate is set hiugher than that it
won;t occur. However, ROs are usually set to fully demineralize the
water. This effect is independent of the the effect of minerals on
taste; here, 30 to 40 TDS would still taste pretty thin and bright
(ans using Robusta would actually help), and the optimum is 100 to 150
TDS.
> "The Silvia is not a commercial machine, no matter how hard you owners
>pretend"
I wasn't referring to you specifically. Silvia owners tend to adopt
procedures designed to accomodate the large boilers and complex water
paths of commercial machines. While the Silvia has commercial parts,
it is a home machine with a small boiler and a simple water path. One
can descale it by filling the tank with descaler, and running the pump
until it is empty; there is no need for water treatments. One can
clean it by doing the same with a detergent (always rinsing
afterwards), and there is no need to backflush it.
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Date: 13 Jun 2006 01:13:32
From: Brewer Bob
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus
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Yeah, I figured that RO water was best just to keep the boiler free from
scale. My water profile here in Livermore(S.F. East Bay) is ~ 150 PPM
of hardness. I got good results with this in my Solis SL-90 and now will
switch back to my filtered tap water for my PID'd Silvia. I did notice
using RO water that my crema really suffered.
What machine are you using Jim? Just curious.
Brewer Bob
jim schulman wrote:
>On Mon, 12 Jun 2006 07:18:54 GMT, Brewer Bob
><bob-girolamo@nospam.sbcglobal.net> wrote:
>
>
>
>>>"RO water will make even robusta look bad.
>>>
>>>
>
>
>
>>Does that mean Robusta has a higher acidic level on a pH level and needs
>>the alkaline(Residual Alkalinity versus temporary hardness which are
>>mainly composed of bicarbonates) buffering agents in harder water to
>>balance the acidity to mellow their percieved acidity?
>>
>>
>>
>
>No, low mineral water creates slime in the puck and interferes with
>extraction and crema formation. This effect disappears at around 30 to
>40 TDS, and if your RO's rejection rate is set hiugher than that it
>won;t occur. However, ROs are usually set to fully demineralize the
>water. This effect is independent of the the effect of minerals on
>taste; here, 30 to 40 TDS would still taste pretty thin and bright
>(ans using Robusta would actually help), and the optimum is 100 to 150
>TDS.
>
>
>
>>"The Silvia is not a commercial machine, no matter how hard you owners
>>pretend"
>>
>>
>
>I wasn't referring to you specifically. Silvia owners tend to adopt
>procedures designed to accomodate the large boilers and complex water
>paths of commercial machines. While the Silvia has commercial parts,
>it is a home machine with a small boiler and a simple water path. One
>can descale it by filling the tank with descaler, and running the pump
>until it is empty; there is no need for water treatments. One can
>clean it by doing the same with a detergent (always rinsing
>afterwards), and there is no need to backflush it.
>
>
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Date: 12 Jun 2006 20:25:33
From: jim schulman
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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On Tue, 13 Jun 2006 01:13:32 GMT, Brewer Bob
<bob-girolamo@nospam.sbcglobal.net > wrote:
>What machine are you using Jim? Just curious.
An Isomac Tea, a small HX machine. Desclaing these is more of a chore
than home machines, but it still can be done with straight flushing,
not disassembly.
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Date: 13 Jun 2006 00:17:57
From: Marshall
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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On Mon, 12 Jun 2006 16:30:59 -0500, jim schulman
<jim_schulman@ameritech.net > wrote:
>On Mon, 12 Jun 2006 07:18:54 GMT, Brewer Bob
><bob-girolamo@nospam.sbcglobal.net> wrote:
>
>>>"RO water will make even robusta look bad.
>
>>Does that mean Robusta has a higher acidic level on a pH level and needs
>>the alkaline(Residual Alkalinity versus temporary hardness which are
>>mainly composed of bicarbonates) buffering agents in harder water to
>>balance the acidity to mellow their percieved acidity?
>>
>
>No, low mineral water creates slime in the puck and interferes with
>extraction and crema formation. <snip>
Beyond espresso, I recall Joseph Rivera and/or Dave Beeman saying that
certain minerals bonded with flavor elements in the coffee and were
necessary for their extraction in any kind of brew.
Marshall
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Date: 12 Jun 2006 17:34:14
From: anthony
Subject: Re: Coffee Science Tidbits: Steaming Green Coffee and Acidity versus Sour
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Marshall wrote:
> Beyond espresso, I recall Joseph Rivera and/or Dave Beeman saying that
> certain minerals bonded with flavor elements in the coffee and were
> necessary for their extraction in any kind of brew.
>
> Marshall
I've found this thread really fascinating. It makes me quite happy to
stick with my tap-water, leaving it overnight for some chemical
dissipation, before topping up my Pavoni lever.
Re the comments about no need to backflush Silvia - would I be right in
presuming the same applies to an ECM Botticelli, which I'll be
acquiring soon? I think that unit is virtually identical in specs and
performance to the Silvia, apart from its the Botticelli's slightly
larger boiler.
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