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

Posted Tue Apr 23, 2013, 3:37am
Subject: ...
 

...
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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 699
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Tue Apr 23, 2013, 12:32pm
Subject: Re: Aerobie Aeropress
 

AlanAdler Said:

The amount of brew trapped in the grounds is exactly known:

Posted April 22, 2013 link

It wasn't known (by me) until you provided more details.

AlanAdler Said:

Trapped brew = input water wt - brew wt

Posted April 22, 2013 link

For the brews you are talking about your formula underestimates the trapped coffee by about 20%.

I was interested in your calculation of the extraction. You still haven't given us a specific example but I'll take it for granted that you measured what you measured. Have you ever checked your PAL-1 against a more accurate instrument? The accuracy is specified as 0.2% Brix which would translate to 0.17% TDS. For your brews that would mean 1.6% extraction, so a calculation of 25% extraction might really be closer to 23.5%. Still high though.

I have never tried to brew exactly the way you suggest. But I have some dark roasted coffee in the freezer so maybe I'll give it a try later.
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paulbel
Senior Member
paulbel
Joined: 26 Apr 2008
Posts: 152
Location: Vancouver, BC, Canada
Expertise: I love coffee

Espresso: aeropress
Grinder: conical burr (cuisinart)
Drip: sometimes
Posted Tue Apr 23, 2013, 1:37pm
Subject: Re: Aerobie Aeropress
 

jpender Said:

I have never tried to brew exactly the way you suggest. But I have some dark roasted coffee in the freezer so maybe I'll give it a try later.

Posted April 23, 2013 link

I'd be really interested in the results.   (Imagine, following the instructions. How boring is that?)

Though, honestly, I don't care about the numbers so much as I care about the flavour.
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AlanAdler
Senior Member
AlanAdler
Joined: 31 Dec 2005
Posts: 708
Location: Palo Alto, Calif
Expertise: Professional

Espresso: AeroPress
Grinder: Baratza - Virtuoso
Roaster: Fresh Roast SR-500
Posted Tue Apr 23, 2013, 4:05pm
Subject: Re: Aerobie Aeropress
 

jpender Said:

It wasn't known (by me) until you provided more details.



For the brews you are talking about your formula underestimates the trapped coffee by about 20%.

Please explain. -- Alan

I was interested in your calculation of the extraction. You still haven't given us a specific example but I'll take it for granted that you measured what you measured. Have you ever checked your PAL-1 against a more accurate instrument? The accuracy is specified as 0.2% Brix which would translate to 0.17% TDS. For your brews that would mean 1.6% extraction, so a calculation of 25% extraction might really be closer to 23.5%. Still high though.

I have never tried to brew exactly the way you suggest. But I have some dark roasted coffee in the freezer so maybe I'll give it a try later.

Posted April 23, 2013 link

I tested my PAL-1 against a Brix meter used by Randy Pope, a chemist at Bunn.  I don't know the maker of his meter.  Randy is the man who came up with the 0.85 factor.  Our readings on some Brix 1.5 brew were identical.  I've also tested it against some optical sight meters with good agreement.

One other consideration.  My meter reads low for a hot sample.  I press the read button approximately once per minute.  When two consecutive readings repeat, I accept that number.  That's about one or two minutes after putting a very shallow sample on the window.  But it takes longer for a deep sample, which holds more heat.

Alan
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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 699
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Tue Apr 23, 2013, 5:16pm
Subject: Re: Aerobie Aeropress
 

AlanAdler Said:

Please explain. -- Alan

Posted April 23, 2013 link

You're leaving out part of the mass balance.
In both the brewed coffee and trapped coffee there are both water and dissolved coffee, not just water.

You're saying: brew_water = trapped_coffee + brewed_coffee

But it's really more like: dry_coffee + brew_water = dry_grounds + trapped_coffee + brewed_coffee

If you rearrange that and remember that (dry_coffee - dry_grounds) is just the extracted coffee in an immersion brew and equal to (strength X brew_water) brew_water X strength/(1-strength), then you get:

trapped_coffee = (1 + strength)*brew_water - brewed_coffee
trapped_coffee = (1 + strength/(1-strength))*brew_water - brewed_coffee


AlanAdler Said:

I tested my PAL-1 against a Brix meter used by Randy Pope, a chemist at Bunn.  I don't know the maker of his meter.  Randy is the man who came up with the 0.85 factor.  Our readings on some Brix 1.5 brew were identical.  I've also tested it against some optical sight meters with good agreement.

One other consideration.  My meter reads low for a hot sample.  I press the read button approximately once per minute.  When two consecutive readings repeat, I accept that number.  That's about one or two minutes after putting a very shallow sample on the window.  But it takes longer for a deep sample, which holds more heat.

Posted April 23, 2013 link

So how do you handle the sample? Do you put it hot in the sample well and then keep checking the readings until stable?

(edited 24 April to correct math)
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AlanAdler
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AlanAdler
Joined: 31 Dec 2005
Posts: 708
Location: Palo Alto, Calif
Expertise: Professional

Espresso: AeroPress
Grinder: Baratza - Virtuoso
Roaster: Fresh Roast SR-500
Posted Tue Apr 23, 2013, 7:45pm
Subject: Re: Aerobie Aeropress
 

jpender Said:

trapped_coffee = (1 + strength)*brew_water - brewed_coffee

So how do you handle the sample? Do you put it hot in the sample well and then keep checking the readings until stable?

Posted April 23, 2013 link

Math is agreed to.  But you wrote "trapped_coffee =".  How about, "trapped liquid ="?  I'll edit my prior post and change "exact" to "approximate".

Yes, I put it hot in the well and check as you have written.

Best,

Alan
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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 699
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Tue Apr 23, 2013, 8:09pm
Subject: Re: Aerobie Aeropress
 

AlanAdler Said:

Math is agreed to.  But you wrote "trapped_coffee =".  How about, "trapped liquid ="?

Posted April 23, 2013 link

That's what I meant, liquid coffee. It is possible that there is some liquid water in the grounds that contains no dissolved coffee but I don't know how much if any there is of this. So I was assuming that ALL the liquid in the grounds is coffee at the same strength as what is pressed out into your mug. That's the basis for the basic immersion extraction formula that you and VST/Mojo use.

AlanAdler Said:

Yes, I put it hot in the well and check as you have written.

Posted April 23, 2013 link

Aren't you worried that evaporation will concentrate your sample and give you a false high reading?
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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 699
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Tue Apr 23, 2013, 8:11pm
Subject: Re: Aerobie Aeropress
 

paulbel Said:

(Imagine, following the instructions. How boring is that?)

Posted April 23, 2013 link

I have taken it on faith that the Aeropress instructions are simply wrong. I believe it is established coffee dogma that 175F water will not extract very well. While I have a lot of curiosity about coffee and am willing to spend silly amounts of time measuring stuff pointlessly, I'm mostly interested in making a tasty cup o' joe each morning. Why would I waste my time doing some something as foolish as brewing at 175F? Just because the inventor of a plastic frisbee-like toy says it's a way to make "espresso"? Seriously??

And yet I have now brewed two cups at 175F, tasted them, and measured their strengths and extractions.
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paulbel
Senior Member
paulbel
Joined: 26 Apr 2008
Posts: 152
Location: Vancouver, BC, Canada
Expertise: I love coffee

Espresso: aeropress
Grinder: conical burr (cuisinart)
Drip: sometimes
Posted Tue Apr 23, 2013, 8:22pm
Subject: Re: Aerobie Aeropress
 

jpender Said:

I have taken it on faith that the Aeropress instructions are simply wrong.
......
And yet I have now brewed two cups at 175F, tasted them, and measured their strengths and extractions.

Posted April 23, 2013 link

How did they taste?
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AlanAdler
Senior Member
AlanAdler
Joined: 31 Dec 2005
Posts: 708
Location: Palo Alto, Calif
Expertise: Professional

Espresso: AeroPress
Grinder: Baratza - Virtuoso
Roaster: Fresh Roast SR-500
Posted Tue Apr 23, 2013, 8:56pm
Subject: Re: Aerobie Aeropress
 

jpender Said:

Why would I waste my time doing some something as foolish as brewing at 175F?

Posted April 23, 2013 link

Three brewings.  Each with the same beans and grind.

Water Temp      Extraction
175F                21.8%
165F                22.6%
155F                20.6%  

Best,

Alan
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