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jpender
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jpender
Joined: 11 Jul 2011
Posts: 695
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Mon May 14, 2012, 10:08am
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

andys Said:

A more intuitive (and perhaps more accurate) definition of Absorption might be:
(amount of brew water absorbed by the grounds/weight of dry grounds)

Posted May 13, 2012 link

Netphilosopher Said:

If I know it's 2.06, then I just add 2.06Xdry coffee mass to the brew water

Posted May 14, 2012 link

These each look like the same definition of absorption to me.


Netphilosopher Said:

Say I want 700g of coffee at 1.25% strength....  I want 691.25g of water in the end

Posted May 14, 2012 link

This doesn't match the formula you've been posting that ignores the mass of dissolved solids in the cup:

Strength = Extraction / ((1/Brew Ratio) - Absorption)

Have you changed your mind?
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Netphilosopher
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Joined: 14 Jan 2011
Posts: 1,602
Location: USA
Expertise: Just starting

Posted Mon May 14, 2012, 10:45am
Subject: .
 

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Chang94598
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Joined: 24 Oct 2007
Posts: 213
Location: SF Bay Area
Posted Mon May 14, 2012, 10:54am
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

My understanding for the brew formula is:

Strength= (Coffee*Extraction%) / (Total Water - Total Water * Absorption)

Dr Lockhart from the Coffee Brewing Institute used 2.086 ml of water absorbed per gram of dry coffee. In my experience of brewing single cup drip and Abid, the absorption rate is about 2.25 g (not ml) per gram of dry coffee.

The ground coffee water absorption is time and water quality dependent. Coffee will retain more softer or distilled water, and vice versa. In drip, it also varies if the paper is pre-wet or not (duh, obviously).

The decision to use volume vs weight is size. I assume in commercial settings, where large amount of coffee is needed, volume is easier. In home setting, weight is convenient.  It is only a matter of molality vs molarity, just like in a chemistry lab.
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Netphilosopher
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Joined: 14 Jan 2011
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Posted Mon May 14, 2012, 11:05am
Subject: .
 

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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 695
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Mon May 14, 2012, 12:35pm
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

Netphilosopher Said:

The drip pot: 40g coffee, 415g brew water (added 15 for evaporation), 328.1g produced at 2.75%.  Yield based extraction back calculates to 22.5%, and is in line with how it tastes (over extracted).  The spent coffee weighed 112.3g (so the absorption was around 1.808).

Posted May 14, 2012 link

Here you define absorption = (wet grounds / initial dry coffee) - 1

Netphilosopher Said:

If I know [the absorption is] 2.06, then I just add 2.06Xdry coffee mass to the brew water and I'm all set

Posted May 14, 2012 link

But this is inconsistent with that definition.

If you use that definition the extra brew water needed is not absorption * dry coffee mass.
It's (absorption + extraction) * dry coffee mass.
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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 695
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Mon May 14, 2012, 12:41pm
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

Netphilosopher Said:

What's really puzzling is when I can have the same brew ratio (say 10%)for two different methods, and obtain two different strengths.

Posted May 14, 2012 link

I think the most likely explanation is that the liquid retained in the wash through method is much weaker in dissolved solids than that of the immersion method.

Suppose that the retained liquid is of strength 0% for the filter brew and is equal to the strength in the cup of the Aeropress brew. If you could somehow wash out those retained dissolved solids the extraction yields of the two brews would be nearly identical.
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jpender
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jpender
Joined: 11 Jul 2011
Posts: 695
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Mon May 14, 2012, 1:24pm
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

Netphilosopher Said:

From the simple concept of:
Coffee Produced = Brew Water - (Absorption X Coffee)

Posted May 14, 2012 link

So there it is: absorption = (wet grounds / initial dry coffee) - 1

Dr. Lockhart specifically defined it this way?


I prefer the definition that AndyS advocates and VST uses:

absorption = retained water / initial dry coffee
which means:
coffee produced = brew water + (extraction - absorption) * initial dry coffee

This really isn't more complicated, just different, and to me at least, intuitive.


Either way, it's only a constant when it isn't varying.
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Netphilosopher
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Posted Mon May 14, 2012, 2:06pm
Subject: .
 

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jpender
Senior Member
jpender
Joined: 11 Jul 2011
Posts: 695
Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
Drip: Aeropress
Posted Mon May 14, 2012, 4:01pm
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

Netphilosopher Said:

I don't think that's inconsistent.

Posted May 14, 2012 link

It's inconsistent in the same way that 100+1=100 is. It's an approximation, albeit a pretty good one for normal conditions. Outside that range it diverges somewhat more. Isn't one of your goals to improve the predictive power of these formulas/charts? If it were me I would make approximations after I got there, not before.

But this isn't the interesting part of your question.
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andys
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andys
Joined: 10 May 2003
Posts: 850
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 Mon May 14, 2012, 5:33pm
Subject: Re: Coffee Extraction Discussion, Questions for the membership:
 

Netphilosopher Said:

In every case, however, the ONLY indicator that you have "extraction" right is by taste.

Posted May 14, 2012 link

<sigh> How are you going to explain that to Lord Kelvin?

Meanwhile, I'm expecting that you're going to put together some kind of Unified Field Theory of Coffee Extraction. On one end of the extraction spectrum you'll have espresso and pourover brews, where the liquid trapped in the grounds at the end is weak enough (the Weak Force) to be ignored. On the other end you'll have cupping, Eva Solo and perhaps French Press, where the liquid trapped in the grounds is approximately the same strength (the Strong Force) as the beverage, and will be counted in the extraction. Other methods, such as vac pot and Aeropress will fall in specific intermediate areas. They each will have their own Cosmic Coffee Constant that will offset their measurements relative to the others. In the end, 19% extraction will taste about the best for all methods.

Or not.  :)

Anyway, it's a fun thought. Happy brewing!

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