pvblack Senior Member Joined: 20 Oct 2012 Posts: 2 Expertise: Just starting
Posted Sat Oct 20, 2012, 12:56am Subject: AeroPress Solubles Concentration
After my friend sold me on it, I bought a shiny new AeroPress the other day. I've searched a lot, and I've seen one or two studies on pushing the envelope of extraction numbers with an AeroPress (including one on here), but there just doesn't seem to be that much good data out there.
My question is this: What is the practical limit to the TDS concentration in coffee brewed with an AeroPress? I've mostly read about people using relatively low brew ratios (15g of coffee/270g of water), but I've also read about and tried much higher brew ratios (24 g of coffee/120g of water). At these higher brew ratios, does extraction fall off?
I'd love to be able to press, say, 60g of water through 20g of coffee at 20% extraction. Accounting for water trapped in the puck, this is likely to yield a final volume of about 40g or so, leading to a final TDS concentration of about 10%. Something tells me there has to be some limit, some reason this won't work. What is the limit, and how do I push this limit?
Thanks for your help. I'm not just completely new to brewing my own coffee—I'm completely new to drinking coffee at all. I never liked it when I was younger because I never knew you could get stronger concentrations of coffee. All I ever knew was my parents' standard black drip coffee, which I never really like. Then I recently discovered espresso when I was trying to stay awake on a long drive. I still don't really find coffee palatable unless it is at that concentration or close to it, and I'm trying to find a relatively inexpensive means of producing that thick, black, super-concentrated sludge. (*salivating*) If anyone could tell me how to get close to this at home on the cheap, I'd be most grateful.
jpender Senior Member Joined: 11 Jul 2011 Posts: 406 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Sat Oct 20, 2012, 6:08pm Subject: Re: AeroPress Solubles Concentration
pvblack Said:
My question is this: What is the practical limit to the TDS concentration in coffee brewed with an AeroPress? I've mostly read about people using relatively low brew ratios (15g of coffee/270g of water), but I've also read about and tried much higher brew ratios (24 g of coffee/120g of water). At these higher brew ratios, does extraction fall off?
I'd love to be able to press, say, 60g of water through 20g of coffee at 20% extraction. Accounting for water trapped in the puck, this is likely to yield a final volume of about 40g or so, leading to a final TDS concentration of about 10%. Something tells me there has to be some limit, some reason this won't work. What is the limit, and how do I push this limit?
With an infusion brew method the "water trapped in the puck" will actually be coffee at about the same strength as what you press into your mug. So in estimating the strength you have to take that into account. In your example of 20g of coffee at 20% extraction and 60g of water you'd expect a strength of about 6.7% (0.20*20g/60g). So to maximize strength you'd want to maximize the brew ratio. Your yield would suffer horribly and you might have problems attaining 20% extraction with so much coffee and so little water. It begs the question why you would want to maximize strength like this in the first place. It certainly can't be to save money on coffee!
Posted Sun Oct 21, 2012, 11:43am Subject: Re: AeroPress Solubles Concentration
Huh? Whaa? Someone called?
LOL
------------------------------------------ ----------------------------------------- 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 Sun Oct 21, 2012, 11:56am Subject: Re: AeroPress Solubles Concentration
So, here's the general rules that I work with regarding the AP:
Grind, temperature, and infusion time determine extraction. This holds well all the way up to 5.5 water brew ratio (that's something like 180g coffee per liter).
(technically, Grind, Temperature, Time and brew ratio determines strength, very predictably, which is used to determine "extraction". We never measure "extraction" directly - only by inference which requires accurate strength, water mass, and coffee mass).
Here's an experiment summary I did that supports the thinking. "Re: Coffee Extraction Discussion, Questions for the membership:" I tasted these runs (the thread is long and involved - beware) and personally found very consistent taste profiles when they were diluted to same basic strength (about 1.15% to 1.25% when possible).
The linear nature is only possible if the solubles concentration is involved with ALL of the brew water. The classic brew charts don't apply to immersion/infusion brewing, for the very explanation the JPender gave.
You might find a post or two from me if you search on the forum... ;^D
------------------------------------------ ----------------------------------------- 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
Well, I was expecting Netphilosopher to have a ready answer to this question.
As the coffee/water ratio goes up the brew temperature will fall off which will affect the extraction. So the optimal brew ratio to maximize strength is likely something less than an Aeropress packed tight with finely ground coffee and a minimal amount of boiling water poured into it.
The recipe for the strongest Aeropress coffee -- maybe you could offer a prize and make it into a contest?
Posted Sun Oct 21, 2012, 6:54pm Subject: Re: AeroPress Solubles Concentration
jpender Said:
Well, I was expecting Netphilosopher to have a ready answer to this question.
As the coffee/water ratio goes up the brew temperature will fall off which will affect the extraction. So the optimal brew ratio to maximize strength is likely something less than an Aeropress packed tight with finely ground coffee and a minimal amount of boiling water poured into it.
The recipe for the strongest Aeropress coffee -- maybe you could offer a prize and make it into a contest?
It all depends on the definition of "practical". For single step brewing with the AeroPress, it depends on how much brew coffee and how much produced coffee you consider "practical". Is 15g of coffee produced enough? That's some ristretto territory - 28ml of espresso that's almost half crema.
Digging back to beginning of the year, I found a single-step steep brew fine grind as follows:
12 minute steep (inverted, preheated AeroPress) very fine grind (Hario Mini Mill Slim, near talc) 40g brew coffee 90g Boiling brew water Produced about 22g of high strength something. (this was a bit higher for absorption than normal - around 1.7)
R = 2.25 S measured about 10% (9.94, according to my note).
Yield based (incorrect but "standard) extraction was ~9g/40g = 22.5, but this brew tasted like sh... crap. Pretty badly overdeveloped, bitter and yuck.
Good tasting (implied properly extracted) practical limit for very teeny yields I would consider around 8% TDS - that's using 40g of coffee to 90g brew water, getting somewhere around 2 tablespoons of coffee (yep - that's about 30g) concentrate at fairly correct extraction. It IS NOT espresso, but it is approaching espresso like strength. That yield does make a decent 150g cup of coffee when diluted.
The Yield Ratio (the ratio of produced coffee to brew coffee) is simply (R - A). At no time can A be greater than R, or your yield ratio becomes 0.
In the above, A ~1.7, R ~ 2.25, so yield ratio was 0.55, or 40g*0.55 = 22g of produced coffee.
If you know your absorption, and you know how much coffee concentrate you want (say, 20g) you can back calculate this "practical limit".
Understand that 20g is only about 1 1/3 TABLESPOONS of coffee. It ain't much. Errors creep in like crazy, you need a scale that reads to the hundreth of a gram if you're trying to measure extraction.
Theoretically, you might be able to do: 80g Brew Coffee 120g Brew Water
R = 1.5, if you're lucky and your absorption is around 1.25 - you'll get around 20g of produced coffee. If you extracted it to 20%, you might be able to achieve 11.5% strength. But really, how practical is that? 80g is enough to make about 1.2 LITERS (1200g) of normal coffee in a drip coffee maker, or 1 liter of same strength coffee in a press pot.
The temperature dropping is fairly minimal effect on equilibrium strength for an extremely long steep - it just takes a little longer to reach (temperature acts like a scalar on the time axis for extraction for the steep methods).
------------------------------------------ ----------------------------------------- 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
That's where NetPhilosopher simmered his coffee at near-boiling (probably about 205°F) for about 2 minutes. I don't see this as "impractical". It's only slightly more trouble than brewing inverted for 2 minutes, provided one has a gas stove (not an electric—more fine heat control). And it's certainly less trouble than using a real espresso machine. But this method yields what seemed to me to be bitter and overextracted results. Perhaps I got a little too close to the boil.
Btw, I'm not trying to save coffee lol. If I wanted to get the most coffee for my buck, I'd just use a French Press. I like very strong, thick, sludgy, ristretto-esque coffee (though I'm certainly not full enough of myself to ask a barista for a ristretto). I was wondering how to get the shortest, most concentrated "pull" out of an AeroPress.
If I could reproduce NetPhilosopher's stovetop-simmer method without scalding the brew, I'd say NetPhilosopher would have to take the prize for strongest AeroPress coffee recipe. His method solves the problem of insufficient thermal mass at higher brew ratios. But I figured at some point the water has a limit to how much solute it can take on at (slightly above) atmospheric pressure. If you go too high on the brew ratio, at some point your extraction percentage must drop off, as NetPhilosopher observed in his/her earlier experiment.
So, it all comes down to "extraction" (or really something implying "dissolution" - a topic I'm putting together for discussion at a later date). We'll just go with "extraction" - but there's two different governing equations depending on the method.
The typical yield-based extraction is used for percolation. Immersion methods use a different calculation because of the constant strength throughout the brew slurry.
Since percolation (introducing clean brew water at the beginning of contact and collecting the produced solution once the water has passed through the grounds) is a continuous process where the strength of the stuff in the cup is stronger than the stuff coming out of the grounds, the end result is sufficiently close to all of the TDS that has been dissolved. The calculation of "extraction" is based on YIELD, which is based on the ingredients and the method absorption.
Given E=Extraction S=Strength R=Water Brew Ratio (ratio of brew water to brew coffee) A=Absorption
E=S*(R-A), all unitless.
Immersion/Infusion brewing calculated "effective" or as Vince calls it "normalized" extraction is independent of absorption. All you need to know is the water brew ratio and the strength:
In that experiment where I ground coffee to powder, then simmered it and then pressed the result, I was purposefully trying to produce an overextracted brew to prove to myself that the percolation method (yield-based calculation) of extraction was no longer applicable.
Back then, strength was assessed with home-dehydration, which will overstate fine grind by some margin (because I am assessing uncentrifuged coffee that contains both dissolved and undissolved solids in the produced coffee).
Even so, assuming I had R=3.07 (92.2/30), and produced 54.9g of coffee (this does make sense, 1.24 for A is well within my range for AeroPress absorption), here's how the two calculations come out:
S=9.7% (probably on the high side, but we'll go with it, as a dehydration measurement) R=3.07 P (Produced Coffee) = 54.9g A=1.24
So - once I got my refractometer, that's where I began to understand why this was way out of whack. In fact, many of my fine-ground measurements using dehydration (unfiltered) look to be on average 17%-20% higher than measured with refractometer.
Assuming my real strength on that particular experiment was closer to 7.75%:
E (Yield) = 14.2% E (Imm) = 25.6%
I expect that my taste notes are evidence of cognitive bias on my part - it seemed that no matter what I did I simply could not produce an overextracted brew. Since there is no way some noob like me could be correct and all the literature (yield-based extraction) was less than accurate, I must have been simply tasting coffee and telling myself it was not overextracted. That's about where I started giving my wife coffee in single-blind nature, and REALLY paying attention when we didn't agree. Damned if her taste buds have an amazing correlation to the traditional extraction ranges!
Getting at why I have such an error with dehydration and the refractometer was yet another problem - here's a decent description of what I did to determine the majority of this error is undissolved solids (which the refractometer will not measure) "Re: Coffee Extraction Discussion, Questions for the membership:"
I've also done other simmer brews (again, trying to make overextracted brews on purpose) which are definitely overdone. In the intervening year or so from that original post to getting the refractometer, I've learned a bit.
Personally, I think you need to talk not about just solubles concentration - but highest strength with extraction within target (18% to 22%).
Some other things I've learned: -All immersion brews approach an equilibrium strength. Even if you let them sit for 12 minutes. Even if you re-heat them. Even if you let them sit and cool on the counter, then in the morning 12 hours later re-heat it and then press it. -The equilibrium strength is dependent on the water brew ratio and the grind size (coarseness/fineness). -There is a grind level coarse enough that will prevent overextraction at equilibrium. (I haven't tested this for simmering >10 minutes) -Temperature seems to have little or no effect on equilibrium strength. It controls the time to reach the equilibrium strength. The exception is if the brew water never goes above about 135°F - then you're probably cold brewing and do not have enough heat to pull out some of the triglycerides/fatty acids/oils(waxlike) lipids.
For immersion brewing, temperature is truly a lot less of an issue than people make it out to be. I think that people are confused by inconsistent results, and rather than understanding all of the parameters, they assume something and it becomes gospel.
Temperature is CRITICALLY important for time-sensitive brewing. Espresso is the penultimate example: where +/-9 seconds can make a huge difference, so correct (and high enough) temperature is so very important.
Temperature and brewing time in auto-drip are intimately entwined. You can increase brewing temperature by increasing the brew water temperature in the reservoir - but this shortens the brew time!
But if you know that immersion brewing reaches an equilibrium... all that higher temperature will do is make you get there quicker. So, temperature will affect your result if there are a couple of things that are not satisfied:
-If you're climbing the extraction curve, then higher temperature will help you climb it faster. If the grind is fine, then you will need to terminate before the dissolution goes too far. -If you have coarsely ground coffee, then a lower temperature may stretch the time to reach proper extraction and you may find yourself terminating the brew too early.
pvblack Said:
Yes, I have since studied the gospel according to NetPhilosopher.
I know you mean this in jest, but the statement I do find a bit bothersome. I have no "gospel" - everything I post is done with the knowledge that anyone - even myself - can prove the hypothesis false at any time. It isn't doctrine, you're witnessing a theory of coffee extraction develop before your very eyes. But someone can, at any time, write a paper that makes it all open to reinterpretation.
This is just scientific method - and doctrine or thinking that is suddenly unquestionably true is certainly not part of the method. Even the theory of general relativity - subject to falsification (tho not likely) BUT the only way to falsify an established theory is to replace it with another theory (model) that explains not only the phenomenon in question but also why it is different and better. The Theory or General Relativity is so expansive, for example, that it explains and predicts alterations to Newton's Laws of Motion.
It also doesn't mean that more factors makes it a better theory. In string theory, you shouldn't use 36 collapsed dimensions when 8 or 11 will suffice to explain all current natural phenomenon.
Such is the immersion calculation for extraction - now backed up by hundreds of brews. It's a working model of how immersion brewing is controlled, and it is DIFFERENT from percolation. It uses three basic parameters. (Brew Ratio, Extraction, Strength)
pvblack Said:
...
Btw, I'm not trying to save coffee lol. If I wanted to get the most coffee for my buck, I'd just use a French Press. I like very strong, thick, sludgy, ristretto-esque coffee (though I'm certainly not full enough of myself to ask a barista for a ristretto). I was wondering how to get the shortest, most concentrated "pull" out of an AeroPress.
If I could reproduce NetPhilosopher's stovetop-simmer method without scalding the brew, I'd say NetPhilosopher would have to take the prize for strongest AeroPress coffee recipe. His method solves the problem of insufficient thermal mass at higher brew ratios. But I figured at some point the water has a limit to how much solute it can take on at (slightly above) atmospheric pressure. If you go too high on the brew ratio, at some point your extraction percentage must drop off, as NetPhilosopher observed in his/her earlier experiment.
So, note above that the extended boiling and heat is really not needed. Just hit it with hot water on the finest grounds you can get, and let it sit. After 5 minutes, when you press it, you're GOING to overextract if the grind is fine enough. Even with my Bodum Bistro Grinder, if I grind to -2, I'll achieve overextraction in about 1minute and achieve severe overextraction (about 25%) at 3 minutes. At a setting of about 1, (one dot past the pourover icon), I get to about 22% extraction (regardless of brew ratio) in about 3 minutes.
------------------------------------------ ----------------------------------------- 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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