Posted Wed Dec 12, 2012, 3:28pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
jpender Said:
That's what Glenn was objecting to, the way these quantities are mixed together. It works just fine but it's not the most intuitive approach. And while it isn't explicit in the definition your method assumes that there is a slight positive correlation between extraction yield and water absorbed. That could be true, who knows. But it looks like you've tacked that on in order to make the math simpler, not because of a physical model of Absorption Assimilation or data that demonstrate this.
Actually, the reason I just used a constant for Absorption Assimilation as a function of the original coffee is specifically because that's what I saw in the data, and what I've observed in real life. I reasoned that there must be an effect with dissolution (again, there may be) but one of the reasons I kept with the simplified version is:
-Experiment data with large variations in extraction show a fairly constant difference between brew water and produced coffee if normalized by coffee. This implies insensitivity to extraction. -Variation in this normalized mass difference is much greater than anything that can be accounted for with "extraction" or "dissolution". (the AP can vary by more than 0.2, for example) -Using a "guess" at extraction just adds noise to the prediction of produced coffee. -Coffee contains some water already - and that isn't accounted for unless you really want to go nutz. -I originally thought that if there was a consistent, measurable effect, then we could use this difference as a PROXY for extraction without having to rely on a refractometer or dehydration. The experiment shows that you can't use the difference between brew water and produced coffee and any normalization of brew coffee to even roughly estimate extraction. They are completely unrelated with normal brewing of coffee. If you can't use it to forward predict (holding all variables going in as constant or known) then it can't have much of an effect.
My concept of Absorption Assimilation isn't me tacking on terms to make the math simpler - it is a physical description that works. I suppose I could require not only a term for extraction, grind fineness, but also require the user to know their moisture content (another 1-6% of the coffee mass/density) and lipid content (another 2% variation) as well. But then, what would our new "brew coffee" term become?
I measure out 25g of coffee, but it contains 3.5% moisture. Is my brew ratio now different by that mass difference? Does the moisture get counted in the brew calculations? Isn't that water, too? What about blooming new coffee, or older off-gassed coffee (which I've measured up to 2.5% difference in density over a 2 week period in a sealed container for freshly roasted coffee)?
I just use it to predict the produced coffee - and it's accurate enough without having to add terms that a typical user (or even myself - heck, I don't know the true moisture content of my coffee) would not know ahead of time.
------------------------------------------ ----------------------------------------- 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
Please excuse the interruption, since I haven't been closely following this discussion. I hope the following isn't overly repetitious.
I have no qualms with whatever internally consistent math scheme you want to use, and when I've played around with your "absorption" term in place of the "water retained ratio," I found it did in fact simplify the algebra.
But I really don't care for the name you are using, "absorption." That word has a common, everyday meaning which is understood by every lay person: the amount of water absorbed by the grounds. You use it differently (incorrectly, most people would say) since -- as I understand it -- your "A" is really absorption minus extraction.
The difference between the two isn't huge, but it's a key difference: the whole science of making coffee hinges on that extraction term. We are trying to educate people about how the extraction process works; you are, too, but you're being sloppy and/or stubborn (IMHO) with your terminology.
In technical education I think proper terminology matters. Being sloppy does not advance the cause. I'm not sure what you should be calling your "A" term, but absorption isn't it.
Posted Thu Dec 13, 2012, 7:47am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
andys Said:
Hi Steve:
Please excuse the interruption, since I haven't been closely following this discussion. I hope the following isn't overly repetitious.
I have no qualms with whatever internally consistent math scheme you want to use, and when I've played around with your "absorption" term in place of the "water retained ratio," I found it did in fact simplify the algebra.
But I really don't care for the name you are using, "absorption." That word has a common, everyday meaning which is understood by every lay person: the amount of water absorbed by the grounds. You use it differently (incorrectly, most people would say) since -- as I understand it -- your "A" is really absorption minus extraction.
The difference between the two isn't huge, but it's a key difference: the whole science of making coffee hinges on that extraction term. We are trying to educate people about how the extraction process works; you are, too, but you're being sloppy and/or stubborn (IMHO) with your terminology.
In technical education I think proper terminology matters. Being sloppy does not advance the cause. I'm not sure what you should be calling your "A" term, but absorption isn't it.
If we're talking terms, then when it comes to immersion brewing, we are NOT really calculating "extraction". We are estimating "solvation percent" or "dissolution percent". We just can't use the yielded leachate to estimate "dissolution" like we can with percolation. With cupping - there is no "extraction", just "solvation".
For leaching processes, "extraction" happens when you separate out the leachate from the organic solid. In coffee brewing, extraction is the point where the produced coffee is separate from the grounds.
As for the term for describing the physical difference between Brew Water and Produced Coffee normalized by the Brew Coffee, or the term that describes the change of the mass of the grounds after brewing normalized by the brew coffee - I'm open to suggestions.
This parameter is also the same thing as the difference of the Water Brew Ratio and the Yield Ratio (both of which are terms normalized by Brew Coffee):
R = W/C Y = P/C
Example: W=2000g C=120g
R=16.67
P=1760g
Y=14.67
In the above case:
W-P = 240g G = 360g
C = 120, G-C = 240g
This "A-Term" is:
(W-P)/C = (G/C)-1 = R-Y = 2
I will point out that I am not the only one who uses this term "sloppily" Click Here (www.marco.ie)
How do you interpret the language in the SCAE description of the Gold Cup Brewing Mathematics?
"1g of coffee absorbs 2ml of water"
The brewing control chart is back calculated with a constant variable for this parameter.
When it comes to produced coffee, we don't care about keeping track of just the water, transfer of undissolved or dissolved coffee in the grounds - we just want to predict the produced coffee mass. I simply don't see the benefit for overly complicating a term when it adds zero practical value to predicting produced coffee (or predicting the after-brewing mass of the grounds). It ACTS like absorption.
But if people are objecting to the term, I think I'll change it to "Assimilation". That avoids me changing my nomenclature.
At the end of the dissolution stage of brewing, the brew water and brew coffee mixture are separated into two constituents during the extraction stage. One part is solids, regarded as a waste byproduct of the brewing process, known as the wet spent grounds (G) and the desired coffee solution, known as produced coffee (P).
Through experimentation, the mass of the waste grounds G are always more than the original brew coffee mass C, and the balance of the brewing products is the produced coffee mass which contains dissolved and undissolved solids along with a majority of the brew water.
This increase in mass of the grounds (G, at the end of brewing, and C, the Brew Coffee) is "Assimilation", and can be thought of as the assimilated liquid that is stuck in the grounds and requires methods outside the normal brewing process to extract, as a function of either the original dissolved or the undissolved coffee.
The amount of assimilation is dependent on the mass of the brew coffee, and is generally independent of brew water, water brew ratio, and dissolution or extraction yield. It has some variation from brew to brew, potential variation depending on the coffee varietal and roast level, and is also dependent on the method of extraction. It can be approximated by a constant for a given brew process.
It makes little difference to the physical meaning of the term, whether the term is normalized based on pre-brew coffee mass (brew coffee C) or coffee solids (dissolved or undissolved) that remain in the grounds. This is because the "unextracted" coffee solids (i.e. the coffee that doesn't make it to the pot) are related to the brew coffee C by extraction yield, which is ideally approximately 20%+/-2%. It is, however, important to maintain a consistent nomenclature throughout any brewing model.
Some attempts to identify "just" liquid, or "just" the water portion of the Grounds have been done, but data supports the conclusion that for purposes of predicting produced coffee, this is largely unnecessary.
Most brew systems use gravity-driven extraction, where the grounds are allowed to drain naturally with only gravity to aid the percolation process. These tend to be, on average, A=2.0 Some brew systems use forced extraction plus percolation, which can be accomplished by pressure or vacuum, and these systems will have a lower average "assimilation coefficient". These processes tend to be between A=1.1 to 1.8 Brew systems that do not depend on percolation during the extraction process can have significant variation in this parameter. Methods of this nature are French Press/Press Pot, Decoction, and cupping or other methods that depend on grounds settling.
In simple terms, it can be thought as 1g of coffee "assimilates" 2g of brew slurry mass after the extraction stage of coffee brewing for gravity percolated methods.
The term "assimilation" is only important in calculations that require prediction of produced coffee based on input ingredients of W and C.
------------------------------------------ ----------------------------------------- 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
I take it at face value: 2 grams of water absorbed per gram of coffee. It's fascinating that we see it differently.
Your approach includes an additional, albeit negligible, mass transfer. The formula works great. I'd use it. But A isn't really the absorption (ratio). It's something else. To illustrate, suppose instead of 2 g/g the water retention for coffee was a lot less, say, 0.1 g/g. Then for a 20% extraction yield we'd get this:
LRR = 0.1 g/g A = -0.1
LRR still means what it says: 0.1 g of water absorbed per gram of coffee. But a negative value for the so-called "absorption"? What does that mean?
If it were me I'd come up with some boring term like brew coefficient and continue using A or K or whatever letter fits.
Posted Fri Dec 14, 2012, 12:56pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
jpender Said:
I take it at face value: 2 grams of water absorbed per gram of coffee. It's fascinating that we see it differently.
Your approach includes an additional, albeit negligible, mass transfer. The formula works great. I'd use it. But A isn't really the absorption (ratio). It's something else. To illustrate, suppose instead of 2 g/g the water retention for coffee was a lot less, say, 0.1 g/g. Then for a 20% extraction yield we'd get this:
LRR = 0.1 g/g A = -0.1
LRR still means what it says: 0.1 g of water absorbed per gram of coffee. But a negative value for the so-called "absorption"? What does that mean?
If it were me I'd come up with some boring term like brew coefficient and continue using A or K or whatever letter fits.
G - Grounds (wet, spent) mass after brewing C - Brew Coffee Mass, before brewing
The difference is always positive for all brewers. It is normalized (like all the other parameters) by brew coffee mass. It is considered approximately constant and used to estimate produced coffee.
(I still think that if there WAS an actual factor that mattered, we could then use the grounds mass to determine extraction yield)
LRR would then be defined (from physical measurements) as what, then?
((G-C)/C) + TDS/C ?
or
((G-C)/C) - TDS/C ?
And yes, TDS is solids in the cup, TDS/C is yield-based extraction calculation - the dissolved solids that make it to the pot/cup normalized by brew coffee mass.
------------------------------------------ ----------------------------------------- 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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