jpender Senior Member Joined: 11 Jul 2011 Posts: 404 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Thu Jun 28, 2012, 6:00pm Subject: Re: Compare and Contrast: Strength and Brew Method
Netphilosopher Said:
So, my press pot extraction on my last brew was 900g : 56.25g Coffee. Strength was 1.21%
If I just pour one cup at 350g, then my extraction is only 7.5% (assuming I just tossed the rest)
If I pour my big mug at 550g, then my extraction is about 11.8% (assuming I left the rest with some small amount of dregs)
If I pour two of my small mugs and get as much as the press pot will allow (absorption 3.3 or so), my extraction is 715g*1.21% / 56.3g = 15.3%. That's it, all my press pot will pour out without coercion.
But, if I scrape up the grounds and put them into my Aeropress and press out some more stuff, (another 100g), my total extraction has now approached 17.5%. Well, maybe a bit more because I think the average strength for that stuff was 1.22% or so.
In a press pot, there would be ZERO correlation of taste to yield-based extraction. Both mugs tasted pretty decent to me, and definitely not underextracted by any stretch. I think the pressings were a bit cloudy and had some fines but other than that it tasted about the same (but cooler - I did not reheat it)
Up until the point where you used coercion, you could make the same claim about a drip brew: throw some of the coffee out the window and claim that yield doesn't correlate with strength or taste -- or anything really. But that's taking it too far.
You have a point that immersion brews are different than percolation in that the retained liquid is at a higher concentration of solubles. But the relationship between strength, yield, and water lost is still the same. The difference is that as yield goes up in your example, it's "a" that changes instead of the strength.
Of course you can declare absorption invalid or redefine it for immersion brews if you like. It's just convention.
Posted Fri Jun 29, 2012, 7:30am Subject: Re: Compare and Contrast: Strength and Brew Method
jpender Said:
Up until the point where you used coercion, you could make the same claim about a drip brew: throw some of the coffee out the window and claim that yield doesn't correlate with strength or taste -- or anything really. But that's taking it too far.
You have a point that immersion brews are different than percolation in that the retained liquid is at a higher concentration of solubles. But the relationship between strength, yield, and water lost is still the same. The difference is that as yield goes up in your example, it's "a" that changes instead of the strength.
Of course you can declare absorption invalid or redefine it for immersion brews if you like. It's just convention.
I don't think it's the same thing at all. At the end of a perc extraction, the stuff in the grounds is extremely weak, tastes like a combination of liquid smoke and lemon juice and a dash of alum. On a standard 20% extraction (mostly independent of brew ratio between 5% and 8.5%) the strength of the grounds liquid is about 25%-30% of the end strength of the beverage, at least that's what I'm finding.
(and yes, I have pressed the grounds at the end of a drip brew, and I can get right around 1.3 Absorption, meaning I can get another 20g of very weak liquid out of the grounds with a Wb=600g:C=48g brew)
The definition of yield-based extraction for perc methods has absorption baked into it - and for the most part I think it's mostly valid. It's because the liquid absorbed is the hottest and most extracted liquid - but it's also adding dissolved solids at a slower rate while diluting the end strength of the beverage.
Example would be one of the last drip brews I did: 615g brew water (becomes 600g because I lose 15g to evaporation with my BCM-4C) 48g Coffee
About 5 minute drip time on a medium-coarse grind.
Strength from initial grounds drips (3.2g): 0.50-0.52%
Aeropress results: extra 18.2g, with 0.78g in filter, essentially same strength, 0.51-0.53%, remaining grounds weigh 106.5g (final Calc A = 1.22)
I know some of the grounds were subject to evaporation, too.
So, if I have a cup of coffee 520g and strength of 1.80%,
BUT I know the grounds have some liquid at 0.51% strength - assume that all of the water in the grounds is in solution as coffee at this strength, or 92.83g of coffee at 0.51% strength. If I could magically get this into the pot:
I get 520g @ 1.8% being diluted by another 92.83g @ 0.51%, or 612.8g @1.6% strength.
New calculated extraction would be 20.4% - the method itself doesn't create as great an error because the strength of the coffee absorbed in the grounds is substantially weaker than the produced coffee. Coercing more out of the grounds simply dilutes the produced coffee.
Maybe perc methods have by default been undercalculating extraction all this time - but it doesn't make much of a difference because one can always argue you can't tell the difference between 19.5% and 20.5% extraction, and it is impractical to sample the end coffee AND the drippings from the grounds just to find another 0.75-1% extraction - imagine especially what a pain that would be when all you can get from the grounds is a handful of drops and all you have is a brand new 1961 dehydration oven - you couldn't even BEGIN be able to know the strength of the coffee in the grounds. It's only now with a fairly accurate instrument that only needs small samples that we can start to understand the meaning of "extraction".
It may be that there is a "true" extraction - one that includes the stuff that's dissolved in the grounds but never makes it to the cup. Maybe Lockhart's yield-based calculation of extraction preference (18% - 22%) is really more like 19%-23% TRUE extraction - we just didn't know that before because we didn't have the ability or technology to know it before.
Contrast this with a press pot brew I did back a couple weeks ago, same brew ratio, 850g water with 68g coffee. At the end of 5:30 contact and press on a true press pot grind, I get a strength of 1.62-1.65%, median reading around 1.64%.
Amount of coffee I poured was about 620 or so, for a yield calculated extraction of a whopping 620*.0164/68 = 15% extraction.
If I squeeze the grounds, I get more grams of coffee at same strength, same taste - but yield-calculated extraction increases. Scrape the grounds and aeropress them, I can get another 130+/- grams of coffee at same strength. Suddenly, my extraction increases to 18%, and I sure can tell the difference between 15% and 18% extraction - except to me it tastes more closer to edge of overextraction, or at least heading that way.
What amount of coffee you choose to call yield seems almost arbitrary.
------------------------------------------ ----------------------------------------- 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
Assuming the oil really does melt at 6.5°C you could test your idea by not only pressing cold and hot slurries but also at least one just a little above the melting temperature. If you see a dramatic difference with a small temperature change around the melting point then you're probably on to something.
Posted Sun Jul 1, 2012, 10:43am Subject: Re: Compare and Contrast: Strength and Brew Method
Well, it's never clean, is it?
LOL
A ~ 1.7 ~45°F ~1.65 ~50°F ~1.5 ~80°F and approaches ~1.25-1.3 much above 100°F
this is general, was doing this fairly quickly, but it's not an exact "melting" point per se.
Of other interest, I had a bit of Dry-Processed Ethiopia Yirg (I usually get pulp or wet), and noticed something curious - the strength of the stuff when same brew parameters were applied (grind, temp, contact time, brew ratio) seemed to be a bit light by around 5% or so (for a target of 1.25% strength, I would get ~1.19%-1.21%). I figured that maybe the total available solids were lower, so I went and did a max extraction, by successively brewing until the end strength was less than 0.05%.
And the total extraction WASN'T the roughly 26.5% that I measured on the EoC 100% Colombia. It was, oh, about 29.9%.
So, I went back and checked - sure enough the EoC 100% Colombia is still 26-26.5% max. The Ethiopia DP is approaching or exceeding a max possible extraction of almost 30%.
This kinda supports the comments from Vince F that different beans may extract differently. His point was light roasted coffee had the potential to be "underdeveloped" or "underroasted on the inside (sic)", but I run most of my roasts for Ethiopia and most of the Africa coffees pretty close to or just into 2C. I suspect that different beans, and maybe even how they are processed may affect how the coffee extracts, and may even have an effect on how much is available to extract.
------------------------------------------ ----------------------------------------- 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
Dunno. Just temperature seems to be the significant variable. Maybe viscosity of the coffee being produced, but I thought the viscosity of coffee with regard to temperature isn't much different than water.
I am wondering if the absorption "sticks". Meaning if I successfully extract whatever is preventing the absorption from being low (in the 1.2 range), and I re-brew cold - will the absorption still follow the temperature or will it stay low once it's been achieved low?
I could do a hot brew, confirm the absorption is low, then brew with fresh water and allow 12hr steep, then check extraction.
insert <shrug> here.
------------------------------------------ ----------------------------------------- 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: 404 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Mon Jul 9, 2012, 11:32am Subject: Re: Compare and Contrast: Strength and Brew Method
Netphilosopher Said:
With temperature only, same grounds?
Dunno. Just temperature seems to be the significant variable. Maybe viscosity of the coffee being produced, but I thought the viscosity of coffee with regard to temperature isn't much different than water.
I am wondering if the absorption "sticks". Meaning if I successfully extract whatever is preventing the absorption from being low (in the 1.2 range), and I re-brew cold - will the absorption still follow the temperature or will it stay low once it's been achieved low?
I could do a hot brew, confirm the absorption is low, then brew with fresh water and allow 12hr steep, then check extraction.
The viscosity of water drops by more than half over that temperature range but it's not a large change in absolute terms. The viscosity of vegetable oil changes a lot more. I sure don't have a clear picture of what's going on here, but I was wondering what else the grounds are composed of. Cellulose? Would that be more likely to retain water when its cold?
I've forgotten what it was you were trying to figure out. I think I'll have a cup of coffee.
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