Posted Tue Jul 10, 2012, 11:10am Subject: Coffee Brewing Method Absorption/Assimilation - A few notes
I've had a couple of inquiries into how I've come to define "absorption". Some suggest that actual "absorption" is only the water in the spent grounds (and is dependent on extraction), others don't like the way it is parsed.
[EDIT - Re-defining the physical description of the transfer of brewing mass as "Assimilation" to distinguish it from the term "Absorption" or "Liquid Retention Ratio"]
Here's the simple as I think I can get it explanation:
Brewing coffee is a recipe. The two components of this recipe are ground coffee and water. Most brew methods specify how much coffee and how much water to use.
When you're done brewing coffee, the amount of coffee you get is always, without exception, less than the amount of brew water you used.
A typical brew recipe might be:
37.5g of medium ground coffee 600g of fresh brew water.
Add coffee to brew basket and insert into the brewer. Add water to the reservoir. Turn on the brew switch to brew the coffee. When the coffee stops dripping into the pot, serve in individual cups. Makes approximately two 270g mugs (approx 9 fl oz each) or three 175g coffee cup servings (approx 6 oz each). Serve warm and consume within 20 minutes.
Every brew method yields less coffee than the mass of the brew water. The question is: "what governs this difference"?
If, for any recipe, you measure the difference between the brew water and the coffee produced, you can check this difference to see if there is a correlation to any of the brewing parameters. You can do this by varying the amount of coffee (but keep the brew water the same), varying the amount of brew water (but keep the coffee the same), or changing the grind, or changing the brewing temperature (if your brew method allows it) or changing the amount of brewing time. You can even use the same parameters but change the brew method.
When you do this you find:
Brewing temperature (not cold brewing, I'm talking temps above 160°F) - No effect Amount of brew water - No effect Grind - very small to inconclusive effect, not predictable
Amount of coffee - The difference is linearly proportional to the amount of coffee used. This linear coefficient is what I call "Absorption Assimilation".
Brew Method - every brew method/configuration has a typical Absorption Assimilation ratio, but is still linearly related to amount of coffee used.
Given the following: C = grams of coffee W = grams of brew water Cp = grams of coffee produced A = this new Absorption Assimilation coefficient
W - Cp = (A * C)
A is different for different brew methods, but is a constant for a particular brew method, regardless of the coffee. For most drip methods, this coefficient can be estimated to be ~2.0, my little brewer is more like 1.7 very consistently, whereas my CCD is around 2.1-2.25.
This also means that given how much coffee we want to use, and a given brew method, we can predict how much coffee we get from a given amount of brew water:
Cp = W - (A * C)
We also know that the difference between the total mass (C + W) is equal to the mass of Cp + the spent grounds. So, we then know the spent grounds have a mass of
G = (A * C) + C
When we have the measurements of a particular brew method and brew recipe, Absorption Assimilation is calculated by either:
A = (G - C) / C (neglecting any mass losses during brewing)
or
A = (W - Cp) / C
Hope that helps!
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 8:47am Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
Regarding Absorption Assimilation - the definition of Absorption Assimilation I use is merely a physical description of the mass difference between the produced coffee and the brew water, as a function of the mass of the coffee.
It comes from the original model of production of coffee: Given W, C, and P, Absorption Assimilation is simply the description of the produced coffee mass as a function of original brew water mass and the coffee.
This can be measured simply with a scale, and does not correlate to extraction. If this "LRR" encompasses mass of extracted solids and if it really mattered, then I'd expect to see a correlation with extraction.
Don't believe me, measure it yourself. Or check somewhere on marco.ie (iirc) - as far back as 2007, the "mathematics of the gold cup" are pretty clear.
Their example: C = 120g W = 2.0 liters (at room temperature, this is essentially 2000g)
1g coffee absorbs 2ml water: – 120g absorbs 240ml of water – 1760ml coffee brewed
A = 2
P = W - (A * C) = 2000 - (120 * 2) = 1760.
No mention of extraction, or dissolved solids in the Absorption Assimilation - they just talk about it in ml - which for the range of room temperature to high temperature is ~5% error.
That's why I've adopted the definition of Absorption Assimilation that I use - it's just a physical description to predict how much produced coffee you get. It's also highly useful to determine the yield ratio, and it works regardless of the extraction.
Of course, any hypothesis or theory is open to revision, falsification, and correction.
I welcome anyone to brew up 9 brews, with three different recipes, plot the strengths and extractions vs. brew ratio and recipe - and plot extraction vs. Absorption Assimilation or "liquid retained" mass (difference between W and P). See if there is an actual correlation with extraction. I didn't find one, and haven't been able to tease one out of the hundreds of measured cups of coffee I've done - but who knows.
VST has their calculation, I have mine. I've defined mine, and it's consistent with a physically measured phenomenon with a simple scale (no refractometer or dehydration oven or TDS meter required), and applicable with any brew method over a broad range of brew ratio.
A = (W - P) / C
G (the mass of the spent grounds) = (A + 1) * C (neglecting losses)
Doesn't get much more simple or more useful than that.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
jpender Senior Member Joined: 11 Jul 2011 Posts: 402 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Wed Dec 5, 2012, 11:44am Subject: Re: Coffee Brewing Method Absorption - A few notes
Netphilosopher Said:
This can be measured simply with a scale, and does not correlate to extraction. If this "LRR" encompasses mass of extracted solids and if it really mattered, then I'd expect to see a correlation with extraction.
The definitions of LRR and A are such that they differ by the extraction yield. If one is not correlated with extraction then the other must be. What do your data show?
Netphilosopher Said:
I welcome anyone to brew up 9 brews, with three different recipes, plot the strengths and extractions vs. brew ratio and recipe - and plot extraction vs. absorption or "liquid retained" mass (difference between W and P). See if there is an actual correlation with extraction. I didn't find one, and haven't been able to tease one out of the hundreds of measured cups of coffee I've done - but who knows.
I did this about six months ago. I'm not sure that 9 brews is enough to see the signal through the noise, but I did get a correlation. I'm just not sure I believe it isn't merely coincidence. You have many more data than I do; what do you see?
From a practical point, the variation expected due to extraction is too small to matter, so either definition is fine; they're just a little different.
I find the idea of grams of water retained per gram of initial coffee conceptually straightforward. Whether it fits with an accurate model of coffee absorption is another matter. The LRR idea assumes coffee is like a dirty sponge, where the amount of dirt (solubles) washed out does not affect how much water the sponge (non-solubles) can hold. Is this true or does the amount of water the grounds retain depend on how much of the coffee is dissolved away?
Posted Wed Dec 5, 2012, 11:58am Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
For the multi-run experiment:
Extraction vs. (Brew Water - Produced Coffee)
No correlation.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 12:00pm Subject: Re: Coffee Brewing Method Absorption - A few notes
Grind Level vs. (W-P) (confounded with contact time - so if coarse grind is exactly and inversely correlated with contact time, this would also be the result. Unlikely but it is possible).
No correlation.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 12:01pm Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
Contact time vs. (W-P)
No correlation.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 12:03pm Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
There isn't a large variable in brew water, but I've done many levels of brew water on other brew devices to know that there isn't a correlation with this variable either. The amount of brew water you push through is not correlated to the difference between the starting brew water and produced coffee (so long as you actually GET produced coffee).
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 12:06pm Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
In fact, of contact time, brew water, grind level, and extraction (strength is confounded with brew ratio and amount of coffee, as is brew ratio itself - that's the reasoning to follow correlation to relationship), the only thing with a strong, reliable correlation is the actual mass of the brew coffee.
Independent of contact time, brew water mass, grind level, and calculated extraction.
The slope, by the way, is a ratio of 0.791 grams of coffee per gram of (W-P) difference. There is an approximate 1.8g intercept - and if you run a dry aeropress with brew water, you'll lose around 1.5g stuck in the filter.
C / (W-P) = .791
and since I defined Absorption Assimilation as the difference of brew water and produced coffee normalized by brew coffee mass:
(W - P) / C = 1/0.791 or 1.24
Technically, it should be (for this brewer and filter setup) = 1.248 * C - 1.8
Adding a term for "extraction" does nothing to improve any sort of back-calculation for Absorption Assimilation.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 12:24pm Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
The difference between using (C*A) = C* 1.16 (the average of the backcalculated A for all runs) and using (C*A) = ((1.248 * C) - 1.9) to predict produced coffee given brew water and brew coffee is small.
in the equation:
P = W - (A * C)
However, I'm finding out that the residual value (the Y-intercept) for A on the Chemex with square filters, for example, might be a bit larger, maybe 5 grams or so. That big filter holds more liquid.
Again, adding any type of factor that encompasses extraction in addition to just the coffee mass does not improve the predictability of produced coffee.
Therefore, I choose to keep my definition of Absorption Assimilation as
A = (W-P)/C or A = (G/C) - 1 (neglecting losses)
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Dec 5, 2012, 12:57pm Subject: Re: Coffee Brewing Method Absorption/Assimilation - A few notes
One thing to keep in mind, try not to confuse TDS with extraction. Extraction is normalized by brew coffee. TDS is directly related to (and therefore you will find a correlation to) brew coffee.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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