jpender Senior Member Joined: 11 Jul 2011 Posts: 408 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Mon Jun 4, 2012, 2:51pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
The latest folly I think may answer the question of "what's left in the puck?"
I thought that if I brewed some coffee with immersion method (inverted AeroPress), then run a 2nd stage "rinse" of the wet grounds with known amount of water, I may be able to tease out roughly how much of the dissolved TDS is in solution vs. how much is just not removable due to the absorption of the grounds.
You may have missed my post on it. I didn't include details because it appeared at the time that rinsing with cold water extracted a large amount of additional solids making the experiment useless. Well if you missed that it's probably just as well because when I went back just now to see why my results differed so much from yours I discovered I'd made an error. When I corrected for that I got something in the same ballpark as you did. Not exactly the same but the measurement error wasn't small. Basically, I had diluted by about 20 to 1 and the second press extracted about 2/3 as much as your original hypothesis predicted (with emphasis on "about").
jpender Senior Member Joined: 11 Jul 2011 Posts: 408 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Mon Jun 4, 2012, 2:59pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
Nope you're not misunderstanding it at all. VST/mojo is NOT an EXTRACTION measurement device. It measures %TDS - in fact, that's ALL it measures (internally, it measures refractive index of a filtered liquid, and then converts and reports this in %TDS - but it does not display the actual nD).
As far as I know, there really is no way to measure "extraction" per se directly - everything is by measured inference. Either you're keeping track of solids transferred to the beverage, or you're backcalculating from strength.
Moka - just use the solids yield. That's as accurate as it gets, since it's a wash method (forced percolation). How much coffee did you use? How much coffee beverage did you produce? What's the strength of the beverage?
E = S Cp/C where E=Extraction S=Strength Cp=Coffee Produced C=Initial Dry Ground Coffee
But the strength is dissolved solids concentration. Solids yield is a measure of total solids. So how does mojo start with a measure of dissolved solids and determine total solids like on Andy Schecter's espresso control chart?
GlennV Senior Member Joined: 27 Oct 2011 Posts: 28 Location: UK Expertise: I love coffee
Posted Mon Jun 4, 2012, 3:35pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
Results:
25.00g = Coffee 199.73g = Brew Water 0.57g = Cap retained 54.83g = Spent Grounds 168.64g = Coffee Produced 2.61% = Strength ... but when I add 34.86g of water it becomes 1.19% strength.
So, this suggests using a water loss ratio of 0.25 (g water/ g of dry coffee) for immersion brews:
With this number Free water left in cap+puck at end = 199.73 - 25*0.25 - 168.64*(1-0.0261) [water in coffee produced] - 0.69 [evaporation, presumably] = 28.55g
The big question then, I suppose, is whether a drip and an immersion brew from the same grind of the same beans, made with water at the same temperature, and at the same strength and yield (as calculated their respective ways) and similarly filtered, taste the same - or at least more similar than when the yields are different.
Posted Mon Jun 4, 2012, 5:44pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
jpender Said:
But the strength is dissolved solids concentration. Solids yield is a measure of total solids. So how does mojo start with a measure of dissolved solids and determine total solids like on Andy Schecter's espresso control chart?
You're right, the espresso "control chart" that I posted on Home-Barista was based on Total Brew Solids (dissolved and undissolved) rather than Total Dissolved Solids. Subsequently, testing by Vince, the Terroir folks, and others suggested that TDS correlated better with flavor balance than did TBS. So ExtractMoJo and Mojotogo are based solely on TDS.
GlennV Senior Member Joined: 27 Oct 2011 Posts: 28 Location: UK Expertise: I love coffee
Posted Tue Jun 5, 2012, 2:56am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
OK, according to experiments reported in
"Role of Water State and Mobility on the Antiplasticization of Green and Roasted Coffee Beans" Pietro Rocculi, Giampiero Sacchetti, Luca Venturi, Mauro Cremonini, Marco Dalla Rosa, and Paola Pittia Journal of Agricultural and Food Chemistry 2011 59 (15), 8265-8271 (page 8269)
roasted coffee beans can hold about 20% by weight of "unfreezable water", "(usually considered as water bound to the macromolecular matrix with a mobility so limited that it cannot freeze)". This is at the upper end of previous results they reference.
That's 20% water and 80% dry coffee - so 0.25g water/g dry coffee!
This is at equilibrium. I don't think grinding would change things much apart from the time to equilibrium. Anyway, that's good enough for me for now.
It's a pity, I think, that David Walsh's big study hasn't asked contributors to record brew method - as this might have revealed a preference for different yields with different methods whenever a blanket 2g water/g dry coffee is used.
Thanks Netphilsopher - here's looking forward to more results on grind size, temperature and time!
Posted Tue Jun 5, 2012, 4:29am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
GlennV Said:
OK, according to experiments reported in
"Role of Water State and Mobility on the Antiplasticization of Green and Roasted Coffee Beans" Pietro Rocculi, Giampiero Sacchetti, Luca Venturi, Mauro Cremonini, Marco Dalla Rosa, and Paola Pittia Journal of Agricultural and Food Chemistry 2011 59 (15), 8265-8271 (page 8269)
roasted coffee beans can hold about 20% by weight of "unfreezable water", "(usually considered as water bound to the macromolecular matrix with a mobility so limited that it cannot freeze)". This is at the upper end of previous results they reference.
That's 20% water and 80% dry coffee - so 0.25g water/g dry coffee!
This is at equilibrium. I don't think grinding would change things much apart from the time to equilibrium. Anyway, that's good enough for me for now.
It's a pity, I think, that David Walsh's big study hasn't asked contributors to record brew method - as this might have revealed a preference for different yields with different methods whenever a blanket 2g water/g dry coffee is used.
Thanks Netphilsopher - here's looking forward to more results on grind size, temperature and time!
Very intriguing. This would imply A in the region of 0.2, but then it would only be based on "spent" coffee (minus extracted solids) so would have to be reduced (to be more representative) by extraction (1-E, actually).
Since extraction seems to range around 0.2, then a good estimate for A=0.16 (actually the (A*(1-E))) for immersion brews.
------------------------------------------ ----------------------------------------- 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 Jun 5, 2012, 5:13am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
GlennV Said:
... The big question then, I suppose, is whether a drip and an immersion brew from the same grind of the same beans, made with water at the same temperature, and at the same strength and yield (as calculated their respective ways) and similarly filtered, taste the same - or at least more similar than when the yields are different.
Unfortunately, I don't have an objective "taste" machine.
ROFLOL!
I can only give you my personal opinion. Your posed question is what started all of this - why could I get "overextracted" that tasted "overextracted" with auto drip, and NEVER achieve "overextracted" even though it tasted like it with immersion method (press pot, contact brew with AP filtering, AP inverted - it didn't matter, always calculated low).
What I've tried so far is working so that I can dilute everything to roughly the same strength (targeting around 1.2%). Similar filtering is not easy or even really possible. Temperature is in the same ballpark - the temp profile is different for an auto drip method and an immersion brew.
In the under-extracted range (as calculated by respective methods), both taste underdeveloped. Similar to what you would expect - hint of sour, primarily coffee flavor with little extra character, quickly develops elements of bitterness with time.
In range of 18% - 21+%, overall character is also very similar. Slightly more body with emphasis on the "chocolate/nut" side of the flavor profile with immersion, slightly brighter and maybe a bit more edge with percolation. Immersion gives the impression of being "richer", or more "full flavored", even more "balanced". I can see why press pot has such a huge following.
Because of the filtering of most immersion brews (except for clever) mine contain more fines and therefore have less clarity. Taking jkalpin's comments about "micro mud" into account, I do wonder if this is contributing to the body and the perception of more chocolate/cocoa elements.
Above this is where the two methods start to diverge (slightly).
Over extracted percolation is immediately apparent. Bitter, harsh, elements of alum, lots of heavy smoky roast flavor. I find these flavors start to creep in around 21.5% or more extraction. Above 23% it's wince-inducing. Approaching 24%+ it's nearly undrinkable, bitter and goes really nasty as it cools or is maintained at a mid-high temperature.
Immersion brews seem to be more tolerant of overextraction (IMO). at 22-23%, there are some elements of harshness and bitterness that creep in but are muted by the increasing impression of body. I think of it as whatever is emphasizing the "dark brown" good flavors with immersion is sort of "buffering" the bad elements. Above 23.5% or so, it definitely takes on a bad balance of flavor character, bitterness and creosote are represented in spades, and an overall "boiled" (can't think of anything else that represents this flavor) character takes over. These hi-extraction brews tend to have some weird sourness at times, and if allowed to cool begin to take on a character that is closest to brewed clearly stale coffee, or "office swill left on the burner for an hour" flavor. (and of course, using the brew control chart these brews are either borderline underextracted or approaching the "ideal" 20% or only slightly higher)
These are, of course, my opinions.
------------------------------------------ ----------------------------------------- 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: 408 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Tue Jun 5, 2012, 11:45am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
andys Said:
You're right, the espresso "control chart" that I posted on Home-Barista was based on Total Brew Solids (dissolved and undissolved) rather than Total Dissolved Solids. Subsequently, testing by Vince, the Terroir folks, and others suggested that TDS correlated better with flavor balance than did TBS. So ExtractMoJo and Mojotogo are based solely on TDS.
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?
For instance, rather predictably, espresso extracted on the low side of solids yield (say 15-16%) tastes sour for many light-roasted coffees and "green" for many darker-roasted coffees. Espresso extracted on the high side (say 20-23%) begins to taste harsh or bitter.
jpender Senior Member Joined: 11 Jul 2011 Posts: 408 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Tue Jun 5, 2012, 11:49am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
-Surprisingly, cone filtration through a Melitta filter works pretty well. Less so if you filter the coffee only, better if you dump the slurry into the cone. I think this is helped by "cake filtration" of the grounds, but there's the initial amount of the coffee that went through the filter without percolating through the grounds bed - and it will carry fines with it.
I tried this with moka coffee produced with a medium grind. I poured 150g of cooled coffee into a #2 Melitta and it quickly clogged. It took over 3 hours to drain and the filtered coffee was still opaque.
If you use the spent grounds as a filter how could you be certain that only undissolved solids were filtered out?
jpender Senior Member Joined: 11 Jul 2011 Posts: 408 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Tue Jun 5, 2012, 11:54am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Netphilosopher Said:
Very intriguing. This would imply A in the region of 0.2, but then it would only be based on "spent" coffee (minus extracted solids) so would have to be reduced (to be more representative) by extraction (1-E, actually).
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