Posted Tue Jun 5, 2012, 5:42pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
jpender Said:
According to Illy the total solids in espresso are typically 90% soluble. So a target soluble extraction of 18-21% would imply a solids yield of about 20-23%. Does that mean further testing showed that the following line from that Home-Barista post turned out to be not quite true?
The proportion of soluble to insoluble solids in espresso may vary a lot. I would accept Illy's figure as an average of Italian espresso prepared using typical Italian baskets manufactured with indifferent quality control. (One of the design goals for VST filter baskets was keeping the insoluble solids around 4-5% or less of the total solids).
Plug for VST baskets aside, if I get espresso soluble extraction yields above ~20.5%, the shots often develop a bitter tinge. My best shots are usually around 18.5% - 19.5% solubles yield. Every once in a while a 17% shot will taste really good and intriguing -- don't ask me why!
Posted Wed Jun 6, 2012, 5:56am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
andys Said:
The proportion of soluble to insoluble solids in espresso may vary a lot. I would accept Illy's figure as an average of Italian espresso prepared using typical Italian baskets manufactured with indifferent quality control. (One of the design goals for VST filter baskets was keeping the insoluble solids around 4-5% or less of the total solids).
Plug for VST baskets aside, if I get espresso soluble extraction yields above ~20.5%, the shots often develop a bitter tinge. My best shots are usually around 18.5% - 19.5% solubles yield. Every once in a while a 17% shot will taste really good and intriguing -- don't ask me why!
Aren't your strengths in the 9%+ range? (High EBR)
Do you ever dilute (Americano-ize) your coffee to more normal strengths?
Reason I'm asking is that I find (again, taste is highly personal, so this is just stuff I've observed) is a personal preference for lower extraction (drip-brewing) with higher brew ratios. If I work a brew ratio around 18% with a pourover, and produce stuff that's 4.9% strength, I find that I tend to prefer this over same brew ratio at 5.30-5.35% - backcalculated extractions are ~19% for the former, ~>20% for the latter. When I start pushing strengths with this brew ratio approaching 5.5%, I get what you're finding - a bitter tinge and some increased astringency. I find it easier to distinguish this when tasted at the higher strengths, and when diluted to ~1.2% strength the differences become more subtle.
However, same coffee produced with a 10% brew ratio instead, I find decent taste from 2.15 to as high as 2.45%, and the bitter tinge doesn't start coming in until I start pushing strengths above 2.55 or so. This kinda indicates a preference more toward the middle of the old traditional sweet spot.
(produced with a pourover method, as the auto drip brewer isn't that flexible).
I do wonder if the prolonged times to achieve the higher strengths are part of this, though, and may not be a suitable analogy to espresso. It's easier to achieve higher strengths (i.e. more extraction) in less time with a pourover and lower brew ratios. The bed depth with fine grind makes for a pretty darn slow percolation.
As we know, prolonged time at heat produces bitter taste compounds.
------------------------------------------ ----------------------------------------- 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 Thu Jun 7, 2012, 4:29am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Ha!
And just like that, you get a scratch-yer-head brew or three.
I went and brewed a handful of cups, and was bewildered by what I was getting - but in a rush and unable to do much more than get the samples checked and cleanup.
So, running grinder setting at D+4 and 7.5% brew ratio, 3:00 produces (usually) a great tasting cup of coffee at 1.41-1.44% strength. The last couple have been strangely "on the edge" of bitter. In the mornings, I'm usually drinking the coffee as I eat breakfast while the strength samples cool - then I measure them while cleaning up in between temperature stabilization (30-45 seconds) with the refractometer.
Since I'm usually later going over the data, I just write 'em down as I see 'em and figure I'll let the data tell me what's going on... later (and maybe jot a tasting note down).
This morning, I noticed the strength had popped above 1.52% - big question mark. Went back in my history, and the last three have been like that, and I've got a note of "bite?" on the brews...
...so I went back over everything and turns out the last three have actually been done at grinder setting D+2. I know exactly why (in the process of doing some other brews with varied grinder setting, and forgot to reset to normal D+4 setting).
And the approximate extraction is pushing 20.5%+ (using the immersion method - again, traditional is nowhere near correct).
This would tend to validate the target extraction zone more like 18% - 20% with a centralized target of ~19%.
I have some other stuff I will be looking into - I found out last week that even at a decent 19% extraction at the end, if my strike temp is higher, I do seem to have a tendency to have a slight bitter edge. This isn't always, it's just an observation, and it's fairly subtle.
------------------------------------------ ----------------------------------------- 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 Thu Jun 7, 2012, 6:56pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
If I work a brew ratio around 18% with a pourover, and produce stuff that's 4.9% strength, I find that I tend to prefer this over same brew ratio at 5.30-5.35% - backcalculated extractions are ~19% for the former, ~>20% for the latter. When I start pushing strengths with this brew ratio approaching 5.5%, I get what you're finding - a bitter tinge and some increased astringency.
------------------------------------------ ----------------------------------------- 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 Thu Jun 14, 2012, 4:47am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
So - does anyone know the solution saturation concentration for coffee TDS?
Just for fun, I brewed a cup of coffee (~1.5% TDS). Then I used that coffee as brew water, same brew ratio, freshly ground coffee, and overbrewed a 2nd cup.
I was just thinking that if I did that and the strength didn't double, it would indicate interference or saturation due to the concentration of the already-brewed coffee TDS in the following extraction.
Alas, the resulting strength was ~3% TDS. I diluted to consumption strength (for me ~1.2%) and it was pretty darn good (didn't expect that). But now I've asked the question, I'll have to find time to do this multiple times. I suspect I'll have to push further than 15% TDS before I see anything close to saturation, maybe more.
I think next cycle I'll start with a large amount in the CCD, then as the batches get smaller and smaller, I'll move to the AP...
------------------------------------------ ----------------------------------------- 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: 407 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Thu Jun 14, 2012, 10:07am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
I was just thinking that if I did that and the strength didn't double, it would indicate interference or saturation due to the concentration of the already-brewed coffee TDS in the following extraction.
Well we know coffee can be a lot stronger than 3% so you're not reaching saturation. But a high enough soluble concentration could affect extraction. At some level it might be possible to drive solubles INTO the grounds. Didn't Schulman postulate that for the initial wetting of espresso pucks?
I think the "general knowledge" is this is the case. Especially so for percolation methods, but I think that's because of the nature of percolation methods.
HOWEVER... (there's always one of those, eh?) I haven't found this to be the case with immersion/press. In the range of 5.5% to ~12% brew ratio, at least. It seems that different brew ratios, subjected to same brewing parameters (grind and contact time, and same separation/filter method) follow a predictable increase in strength with brew ratio, and is repeatable. Note that I purposefully left out extraction in this statement.
With immersion methods, grind is easily controllable. Contact time is easily controllable. The drawdown/filter phase is consistent depending on method (CCD, Press Pot, Vac Pot, or AeroPress).
This is not the case with perc methods - and I think why some folks see some variation in their pourover brews. I have some difficulty myself. Percolation requires a semi-constant brew water delivery rate for repeatability, BUT it also requires a matched percolation rate through the grounds. This means the grind must be matched for the pass-through or percolation rate - so by simply varying the brew ratio, a given setup (like a BCM-4C) may not translate without extraordinary measures, if at all.
The key in understanding this is the "all else being equal". When you alter the brew ratio without altering the grind, for percolation methods, you also alter the percolation rate - and this throws off the "all else being equal" part.
Example - I can't do a 7 minute auto drip on a 6% brew ratio, then change it to 18%, IF I'm trying to do an overextracting brew (finer grind) whilst attempting to achieve same extraction. The brew water I put in determines the cycle time, I may not have capacity to get the two comparative brews to work, and the 18% brew ratio will pool up and clog because of the depth of the grounds bed. The extra variable of the grounds percolation rate (different from the delivery rate) makes updosing a pain to do consistently.
~750g brew water: 45g of 350micron grind, that will be a cycle time of right around 6 minutes from first contact (my BCM does about 2g/second delivery with ambient temp water)
So if I want to do 18% brew ratio of same brew parameters, I'm trying to do 6 minute delivery of 750g on the SAME grind.
~750g brew water : 135 g of 350micron grind. At 2g/second, the filter overruns at minute two.
BUT - even if you get two brews to work at same (ish) brew control parameters and same grind (i.e. you actually get a 6% brew ratio and a 12% brew ratio on a medium 550micron grind to work in 6 minute delivery time), the difference in percolation just from the depth alone, and the extraction that happens during the percolation, means that the higher brew ratio just won't extract as much as the lower brew ratio.
I saw this when trying to do a variety of percolation auto-drip brew ratios and max extraction (i.e. the time is essentially unbounded - my only goal was to maximize extraction). Best I could do on first pass for extraction on 5.5% brew ratio was very good (~26.+% extraction). But for the first pass extraction on 18% brew ratio, best I could do was ~20% extraction over a delivery rate exceeding 20 minutes.
BTW, I know that it is possible to get to just shy of 27% extraction, because I continued to brew both until the resulting strength was <0.10% TDS - in the 5.5% brew ratio case, the strength was extremely low, near zero at the very first pass, but it took about 4 more passes of new brew water over same grounds for the strength to drop to near-zero for the 18% brew ratio (not to mention the time it took). Both totaled around 26.6%-26.8% extraction (IIRC) accounting for all that was extracted.
So, there's maximum extraction - which is valid for any bean any grind any brew method. You just keep brewing and measuring the produced coffee until there isn't any more produced coffee, and account for all that's extracted - there's no brew ratio, only the TDS that makes it to the cup.
Then, there's this other thing that I think of as "practical first pass extraction." For a percolation method (where there's no argument as to what extraction is defined as), this practical first pass extraction is very dependent on brew ratio, and in this method the general case is a negative practical first pass extraction correlation with brew ratio - delivery rate, delivery total time, temperature, grind held constant. But we should always be aware we've altered a hidden variable - the percolation rate - when we change the brew ratio for a given setup.
------------------------------------------ ----------------------------------------- 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
Symbols: = New Posts since your last visit = No New Posts since last visit = Newest post
Forum Rules: No profanity, illegal acts or personal attacks will be tolerated in these discussion boards. No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum. No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum. Who Can Read The Forum? Anyone can read posts in these discussion boards. Who Can Post New Topics? Any registered CoffeeGeek member can post new topics. Who Can Post Replies? Any registered CoffeeGeek member can post replies. Can Photos be posted? Anyone can post photos in their new topics or replies. Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts. Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.
= No New Posts since last visit 