Posted Tue May 15, 2012, 5:01am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
andys Said:
<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.
Percolation methods use the normal brew chart. Espresso, as I've been told multiple times (and is not my area of expertise) is a different animal - since you don't know what the brew ratio is.
Immersion methods use the full brew mass. The normal brew chart can be hand-waved as sufficiently close enough for brew ratios in the 5.5-6.5% range.
The difference is exactly what you mentioned - whatever is stuck in the puck is not important for percolation methods. Whatever is stuck in the puck for immersion methods is part of the coffee you just made - it's completely important.
It's the difference between using a running faucet to wash dried salt out of a washcloth, vs. getting a bucket, putting the washcloth in, and later pulling it out. One of these will be "cleaner" in the end - and it ain't the one immersed.
It's also why even you had trouble "overextracting" an AeroPress using 8:00 and a fine grind. You did overextract it but your calculated extraction wasn't correct for the method.
See, the trouble was in small quantities and high brew ratios, I had the hardest time getting a 19% or 20% extraction using immersion methods. And even when I achieved the "magic 19%" new sweet spot - it tasted like CRAP. Over extracted. Bitter. On Guats and Costa Ricas the brightness was overwhelmed by bitterness. Kenyas - forget brightness. Buried in overextraction.
That's why I decided to map out the brew space. I kept getting 5.5% brew ratios that tasted good (if not slightly weak) at 1.05% strength (underextracted - 12g coffee : 220g water, yielding 200g @ 1.05% TDS = 17.5% extraction)
I kept getting 10% brew ratios that taste GREAT at 1.85% initial strength (24g : 240g, yields 205-215g of coffee at 1.85% -> 16.1% extraction? No way).
When I took a 10% brew ratio and went beyond reason to achieve the "sweet spot" of 19% extraction, long before I got there I was getting some pretty nasty tastes. By the time I "achieved" it - I knew the old brew charts weren't even in the ballpark for the brew ratios used in diluted AeroPress brew methods. Some of the nastiest stuff was 24g:240g, Yielding around 200-210g of coffee at 2.2-2.25% TDS - (210*2.2)/24g)=19.5% but it tasted clearly bad - even when diluted to normal drinking strength.
Yet, when I got the drip machine out, and also tried some pourovers, I found that same brew ratios yielded higher strengths with much more reasonable grinds. When overextracted (technically) the drips coming out of the grounds were very low strength - on the order of 20% of the final produced coffee concentration, and they were some pretty knarly tasting stuff. Sweet-spot brews seem to be more like 35% or so (ones that back calculate to 18-19.5% extraction).
I've now done enough to answer the original question - just wondering if anyone else had done similar. For immersion brews, if you count the grind and the contact time as defining the "extraction parameters", it tastes to me like the brew ratio is fairly independent of extraction. This ISN'T the answer you get if you use the original brew chart or the yield method to calculate extraction. At low brew ratios it's sufficiently good enough to get you in the ballpark, close enough that you can say it is error - at high brew ratios the error is significant.
------------------------------------------ ----------------------------------------- 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 Tue May 15, 2012, 5:43am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
From before, for percolation methods:
From the simple concept of: Coffee Produced = Brew Water - (Absorption X Coffee)
and defining Brew Ratio = Coffee/Brew Water Strength = TDSg/Coffee Produced, or TDSg=Coffee Produced X Strength, (Strength aka %TDS) and Extraction = TDSg/Coffee
Coffee Produced is still the same, but Absorption is only a physical attribute, and dependent on the method. Gravity methods of filtering will still be in the 1.5-2.0 range, AeroPress can vary from 0.95-1.9, depending on how hard you press (or not). I average about 1.2 personally.
Coffee Produced = Brew Water - (Physical Absorption * Dry Coffee)
If you use 20% ± 2% for extraction, it's easy to project the expected strength for this target extraction.
Strength Range at 4% BR: For Percolation: 0.77-0.95%, For Immersion: 0.71-0.87% Strength Range at 4.5% BR: For Percolation: 0.88-1.08%, For Immersion: 0.8-0.98% Strength Range at 5% BR: For Percolation: 0.99-1.21%, For Immersion: 0.89-1.09% Strength Range at 5.5% BR: For Percolation: 1.1-1.34%, For Immersion: 0.98-1.2% Strength Range at 6% BR: For Percolation: 1.21-1.48%, For Immersion: 1.07-1.3% Strength Range at 6.5% BR: For Percolation: 1.32-1.61%, For Immersion: 1.16-1.41% Strength Range at 7% BR: For Percolation: 1.44-1.76%, For Immersion: 1.24-1.52% Strength Range at 7.5% BR: For Percolation: 1.56-1.9%, For Immersion: 1.33-1.62% Strength Range at 8% BR: For Percolation: 1.68-2.05%, For Immersion: 1.42-1.73% Strength Range at 8.5% BR: For Percolation: 1.8-2.2%, For Immersion: 1.51-1.84% Strength Range at 9% BR: For Percolation: 1.92-2.35%, For Immersion: 1.59-1.94% Strength Range at 9.5% BR: For Percolation: 2.05-2.51%, For Immersion: 1.68-2.05% Strength Range at 10% BR: For Percolation: 2.18-2.67%, For Immersion: 1.77-2.15% Strength Range at 10.5% BR: For Percolation: 2.32-2.83%, For Immersion: 1.85-2.26% Strength Range at 11% BR: For Percolation: 2.46-3%, For Immersion: 1.94-2.36% Strength Range at 11.5% BR: For Percolation: 2.6-3.17%, For Immersion: 2.03-2.47% Strength Range at 12% BR: For Percolation: 2.74-3.35%, For Immersion: 2.11-2.57% Strength Range at 12.5% BR: For Percolation: 2.88-3.53%, For Immersion: 2.2-2.68% Strength Range at 13% BR: For Percolation: 3.03-3.71%, For Immersion: 2.29-2.78% Strength Range at 13.5% BR: For Percolation: 3.19-3.9%, For Immersion: 2.37-2.88% Strength Range at 14% BR: For Percolation: 3.34-4.09%, For Immersion: 2.46-2.99% Strength Range at 14.5% BR: For Percolation: 3.5-4.28%, For Immersion: 2.54-3.09% Strength Range at 15% BR: For Percolation: 3.67-4.48%, For Immersion: 2.63-3.19% Strength Range at 15.5% BR: For Percolation: 3.84-4.69%, For Immersion: 2.71-3.3% Strength Range at 16% BR: For Percolation: 4.01-4.9%, For Immersion: 2.8-3.4% Strength Range at 16.5% BR: For Percolation: 4.19-5.12%, For Immersion: 2.88-3.5% Strength Range at 17% BR: For Percolation: 4.37-5.34%, For Immersion: 2.97-3.61% Strength Range at 17.5% BR: For Percolation: 4.55-5.56%, For Immersion: 3.05-3.71% Strength Range at 18% BR: For Percolation: 4.74-5.8%, For Immersion: 3.14-3.81% Strength Range at 18.5% BR: For Percolation: 4.94-6.03%, For Immersion: 3.22-3.91% Strength Range at 19% BR: For Percolation: 5.14-6.28%, For Immersion: 3.31-4.01% Strength Range at 19.5% BR: For Percolation: 5.34-6.53%, For Immersion: 3.39-4.11% Strength Range at 20% BR: For Percolation: 5.56-6.79%, For Immersion: 3.47-4.21% Strength Range at 20.5% BR: For Percolation: 5.77-7.06%, For Immersion: 3.56-4.32% Strength Range at 21% BR: For Percolation: 6-7.33%, For Immersion: 3.64-4.42% Strength Range at 21.5% BR: For Percolation: 6.23-7.61%, For Immersion: 3.73-4.52% Strength Range at 22% BR: For Percolation: 6.46-7.9%, For Immersion: 3.81-4.62% Strength Range at 22.5% BR: For Percolation: 6.71-8.2%, For Immersion: 3.89-4.72% Strength Range at 23% BR: For Percolation: 6.96-8.5%, For Immersion: 3.98-4.82% Strength Range at 23.5% BR: For Percolation: 7.21-8.82%, For Immersion: 4.06-4.92% Strength Range at 24% BR: For Percolation: 7.48-9.14%, For Immersion: 4.14-5.02% Strength Range at 24.5% BR: For Percolation: 7.75-9.48%, For Immersion: 4.22-5.11%
You'll notice that at ~10% brew ratio, the minimum of percolation method is the maximum of immersion method. This means that it only matters if you care about the difference between 18% extraction to 22% extraction.
Good news for espresso is that the percolation method (or yield version of it) is fine for calculating extraction.
------------------------------------------ ----------------------------------------- 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 Tue May 15, 2012, 6:04am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Percolation, for clarity, refers to a general class of leaching/extraction where fresh solvent (brew water) is continually introduced to the bed of solids which contain the desired solutes. I've always thought that percolation is gravity-driven, where wash is kind of "forced" (either through pressure or vacuum) percolation - the key being fresh solvent at the top, the solution after the filter.
Immersion (aka infusion) is mixing the solids and solvent together, letting it steep, and then separating the desired solution at the end of extraction.
Percolation methods would include:
Automatic Drip Pourovers (Chemex, Hario, etc., but NOT Clever Coffee Dripper) Espresso (forced percolation, or wash method) Moka (forced percolation, or wash method)
The characteristic of percolation extraction method is that the concentration of the solution in the spent grounds declines over the extraction as the solute is dissolved, and theoretically at the end of extraction contains only undesired solution. Filtering and separation of the solution from the grounds is continual or semi-continual.
Immersion methods would include: Cupping The Percolator (yes, it has a basket, but it's a misnomer, in the end the continual recycling of coffee through the grounds makes it act like immersion) French Press or Press Pot Clever Coffee Dripper AeroPress Clover VacPot Cowboy Coffee (actually could be decoction, depending on how you make it - if you boil it).
The characteristic that distinguishes immersion from percolation is the the filtering or grounds separation happens after a steeping time, at a particular point. The concentration of the solution at the point of grounds separation is essentially the same throughout the mixture. When complete, the concentration of the solution left in the solids is essentially unrecovered coffee at similar strength as the yield beverage.
One could also classify the various methods depending on whether you add energy during the extraction or not. AutoDrip is percolation with added energy. Pourover is percolation without. Press Pot is immersion with no added energy, whereas Cowboy Coffee decoction and Percolator are immersion methods that adds energy during the extraction.
------------------------------------------ ----------------------------------------- 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 Tue May 15, 2012, 6:08am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Again - classic definition of extraction would use the yield method most of the time:
(Produced Coffee * Measured Strength ) / Original coffee Mass = Extraction.
If you use the classic brew control chart to determine extraction, knowing the brew ratio, then you're using:
Extraction = Measured Strength * ((1/Brew Ratio) - Absorption), where Absorption is approximately 2.06
If you want a slightly more accurate version and you use brew ratio as a ratio of masses (not volume), then use the above with Absorption = 1.76
------------------------------------------ ----------------------------------------- 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
Can you explain how you arrived at this value? I think you mean 1.36 but I'm not positive.
Netphilosopher Said:
If you use 55g/1 liter of hot water, and achieve 1.24% strength, your calculated extraction is 20% on the classic brew chart. This is actually the same thing as using 55g/962.5g of hot water.
BUT if you use 55g / 1000g of hot water and achieve 1.24% strength, your calculated extraction is only 19.2% (because you achieved the same strength but used a higher brew ratio relative to volume to get there). On the chart, it's the same thing as using a brew ratio of 57g/1 liter and achieved 1.24% strength.
jpender Senior Member Joined: 11 Jul 2011 Posts: 400 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Tue May 15, 2012, 1:35pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
I like this idea. How well does it work in practice?
I trust you've experimented with Aeropress, drip, and pourover. What about other methods? To what extent does the absorption constant have to be tweaked with change in method or parameters?
I wonder how well this works with the lowly moka pot. You list it under forced percolation, along with espresso. But the brew ratio is known in advance for moka. Are you suggesting extraction can be estimated with e = s*(1/b - 2.06)? Or is moka also in a category not covered here?
Posted Tue May 15, 2012, 2:50pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
In practice, so far really well. Pourover, drip (just the Melitta BCM-4C), press pot, stovetop simmering. And of course, the I-AeroPress.
I can predict press pot with 10% brew ratio, and fully predict my AeroPress brews over a very wide range of brew ratios and taste. So much so that my D+3 setting and 3 minute contact time is pretty much repeatable within 0.02% TDS.
It also explains why when I try my best to overextract with a high brew ratio, I just can't "technically" get there with the standard brew chart - but I'm pretty darn sure that this method works well because of the correlation of the breakpoint in taste (it's sort of a rapid decline as I approach 21.5% extraction - but 23%+ is definitely a known overextraction).
Enough to know that fresh Ethiopia Yirg at City+ tends to extract about 0.5% less than Colombia or Tanzania at FC - very consistently, with same brew ratios (which is fine because I like it slightly less extracted anyway).
I don't own a moka pot, but I've had coffee made from it and it's surprisingly good. That's next on my list, but I suspect it will follow the percolation method pretty well. I've been lucky, I've heard it's really easy to under-dose a moka pot and end up overextracted. But yes, I'm expected the extraction would follow the formulae with 1.76 for Absorption.
That is one point seven six - the optimization point required to get the brew charts to match the strengths and extractions generated by the adjusted brew ratio based on brew water mass (not hot water volume). I arrived there by optimization.
Try it yourself, use same brew parameters (grind and contact time) for an immersion method, and do 3 different brew ratios. Or pick one brew ratio and vary the grind up and down the scale - and see which calculation of extraction correlates with your taste.
I'm getting well on a couple dozen measured brews with the AP that work very well and were pre-predicted - it's what I've been making sure I validate before posting. The other implication is that if you consider the upper limit of extraction about 26% for extraordinary measures in brew parameters (absurdly fine grind and long hi-temperature exposure), the highest strength you might get for immersion brew at 12% brew ratio is only around 3.0% TDS. Yet for an overextracted 12% brew ratio using percolation, you might be up around 4%TDS.
I've gotten to 2.8% TDS with 8 minutes contact time, agitation, and a very fine grind. Very fine grind, extending the contact time by turning off the drip brewer every 45-60 seconds for a few (and also necessary because of the fine grind to allow the water to percolate) I was able to get 3.88% TDS. (I had to extend the brewing time because the brew basket is close to max at 45g of coffee, so the brew water had to be around 375grams, which would have brewed in about 3:30 without "pausing" the brew cycle and allowing the basket to drain).
Both tasted like crap. One back calculates to only 19.5% extraction, the drip backcalculates to 25% plus. But use the new immersion method and the AP brew is more like just over 24%.
It explains a lot to me.
It's a different claim - that brewing methods can be separated into two main classes, and they require different methods to back calculate extraction.
------------------------------------------ ----------------------------------------- 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: 400 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Tue May 15, 2012, 4:40pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
That is one point seven six - the optimization point required to get the brew charts to match the strengths and extractions generated by the adjusted brew ratio based on brew water mass (not hot water volume). I arrived there by optimization.
jpender Senior Member Joined: 11 Jul 2011 Posts: 400 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Tue May 15, 2012, 4:44pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
I don't own a moka pot, but I've had coffee made from it and it's surprisingly good. That's next on my list, but I suspect it will follow the percolation method pretty well. I've been lucky, I've heard it's really easy to under-dose a moka pot and end up overextracted. But yes, I'm expected the extraction would follow the formulae with 1.76 for Absorption.
For the few I've measured the wet grounds were about twice the weight of the initial dry coffee. I think by your definition that is an absorption of about 1.0. It will be interesting to see what you get.
Netphilosopher Said:
if you consider the upper limit of extraction about 26% for extraordinary measures in brew parameters (absurdly fine grind and long hi-temperature exposure)
I initially took the the points on the brew chart, and developed a large set of data points (3D). These would be extraction, brew ratio with converted fluid oz to ml (it's actually easiest to use the European brew chart, since it's in Coffee(g)/Liter) to percentage, and strength.
Then, I set up data points using extraction and brew ratio to calculate extraction, using 2.0 as a starting point for absorption. I was surprised, but shouldn't have been, when I found that a constant works fine for absorption.
So, using about a dozen data sets: Extraction Brew Ratio Absorption = 2.0 Strength
I compared them to the complimentary data sets using the calculated strength. Then, I used a linear-iterative macro (tho in retrospect I suppose that the solver in excel works too - darn, I do things too hard sometimes LOL ) to minimize the √(Σ(E^2)), where E (error) is the difference between the calculated strength based on extraction, brew ratio and absorption - using absorption as the optimization variable.
Then, to translate this to mass-based, I simply changed the brew ratio (of the target datasets, taking the brew chart at face value) by altering the denominator to grams assuming a temperature of 94°C, or 0.9625 g/cc.
For a single point, from the SCAE chart: 21% Extraction 5.5% (by volume, 55g/liter) 1.30% (plus a smidgen - approximate on the chart, that's why I used several data pairs picked off the chart)
Before optimization, with Absorption = 2.0 Str = .21/((1/0.055) - 2.0) = 1.298% strength.
After optimization, Absorption = 2.068 Str = .21/((1/0.055) - 2.068) = 1.303% strength. (this is closer to the chart)
Then, I overlaid the graphic of the chart to the resulting reconstructed chart and it's basically line to line.
Then, I translated the brew ratios (for example point): 21% Extraction 5.71% (by mass, at 55g/liter, by mass it's 55g/1000g at 4°C, but 55g/962.5 at 94°C) 1.30% (plus a smidgen - approximate on the chart, that's why I used several data pairs picked off the chart)
At Absorption = 2.068, 21% extraction, 5.71% brew ratio: Str = 1.36% (where it should be 1.30 plus a smidgen)
After reoptimization, absorption = 1.76 (over the range of 13% to 26% extraction and 0.9 to 1.65% strength). At this particular point, it's off by a bit (1.33% strength), but fits the entire design space well.
Adding nonlinear terms as extraction or brew ratio dependent terms did not improve the fit enough to justify the increase in algebraic complexity.
For example, one could have absorption be a multi-term extraction and brew ratio dependent term, where
Total Absorption might be = Constant + Extraction term * (Extraction) + Brew Ratio Term * (Brew Ratio) + Ext-BR Term * (Extraction * BR) + Extsquared term * (extraction)^2 + BRSquared term * (BR)^2 + Ext-BRSquared Term * (Extraction*BR)^2
When I do that, however, the terms for everything except the constant are very small - indicating that a linear approximation is fine and a single constant is acceptable. I know I can't taste the difference between 1.303 and 1.33% - but it's likely I can start to detect the difference between 1.30 and 1.36%. It's also a beeee-yotch to algebraically invert (to get extraction given strength and brew ratio).
The absorption term is fairly sensitive to higher brew ratios (probably because that's where the equation for extraction based on BR and Str for a given absorption becomes more nonlinear), so is favored to fit the higher brew ratios of 9% (the highest on the chart) because of the numerical weighting - but it's an error that we have had for a long time now (since 1957) so I'm willing to carry it.
jpender Said:
For the few I've measured the wet grounds were about twice the weight of the initial dry coffee. I think by your definition that is an absorption of about 1.0.
It's about as high as I've been able to achieve with fairly extraordinary brew parameters. If I brew a pot of coffee in the drip machine, then keep the grounds in and brew another pot, yes, technically I can approach 28 or 29%, but I don't think I can get that in any normal sense of brew settings (i.e. in a single 8 minute or less high-temperature percolation method brew). That 2nd pot of weak crap is pretty darn bad, too. I shudder even now thinking about how it tastes. I was reminded of alum on the tongue - that's pretty close. Yuck!
Use 750g+15g water, 45g coffee finely ground - get about 665g of coffee at 1.68% (that 24.8% extraction), and the 2nd pot was around 735g at 0.24% strength (that TDS added to the previous TDS is something around 28.8%).
In full immersion brewing, I think that getting to 26% is REALLY hard - there's some sort of saturation limit for full immersion brewing - I thought it would be based on brew ratio, but even at low brew ratios I can't get much above 25%. Most of the extraction happens in the first 4 minutes, and then it doesn't seem to want to go higher even with agitation and near-talc grind.
------------------------------------------ ----------------------------------------- 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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