Interesting. All links I had to any version of that talk on youtube are now dead. If you search youtube for NBC2012, you get segments for nearly every talk for the two days - except for Vince's.
Probably some "intellectual property" thing. <shrug>
------------------------------------------ ----------------------------------------- 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
The slides are still online, but I have a couple of questions for anyone who saw it.
The number for solute in liquid retained for drip is 0.0. That seems pretty incredible to me. Did Vince have any explanation of how this could be? If there are still unextracted solids in the grounds, it seems some would be extracted into the retained liquid. More generally, what was his explanation for the differences in solute in retained liquid between drip and infusion methods?
The liquid retained for both methods is 2g/g of coffee. Is this number going to hold for methods like Aeropress and syphon/vacuum, where air pressure forces liquid from the grounds? If not, will we need to recalculate dosage to account for differences in amount of liquid retained across infusion methods? E.g., maybe a press pot requires a 14% higher dose than drip to reach equivalent strength and extraction yield, but an Aeropress only requires 10%, once we account for the difference in the mass of the retained liquid.
I'm pretty certain that this is just meant to be a "good enough" approximation. Compared to the concentration in an immersion brew with drip it is effectively zero. The basic idea is that with drip you're continually washing away the solute, reducing the concentration over time, whereas with immersion you reach a maximum concentration and then simply drain some of this liquid away. That's not an exact description but it's close enough, and it's an improvement over treating immersion and drip as identical.
Lee_M Said:
The liquid retained for both methods is 2g/g of coffee. Is this number going to hold for methods like Aeropress and syphon/vacuum, where air pressure forces liquid from the grounds? If not, will we need to recalculate dosage to account for differences in amount of liquid retained across infusion methods? E.g., maybe a press pot requires a 14% higher dose than drip to reach equivalent strength and extraction yield, but an Aeropress only requires 10%, once we account for the difference in the mass of the retained liquid.
...maybe a press pot requires a 14% higher dose than drip to reach equivalent strength and extraction yield, but an Aeropress only requires 10%, once we account for the difference in the mass of the retained liquid.
For immersion brewing, this only matters if you are topping up with hot water to achieve the same final volume of coffee. For a given extraction and brew ratio the strength in an immersion brew is independent of the amount of liquid retained. More liquid retained just means you have less coffee in the cup.
Lee_M Said:
That makes sense, thanks. Do you know how much liquid an Aeropress or syphon typically retains?
I don't have a vac pot, but in an Aeropress I've seen it vary between about 1.2 and 1.7 grams of water retained per gram of initial dry coffee.
This amount of variation is inconsequential from my viewpoint. Since I use ~20g of dry coffee it means the final coffee volume varies about +/- 1 teaspoon.
For immersion brewing, this only matters if you are topping up with hot water to achieve the same final volume of coffee. For a given extraction and brew ratio the strength in an immersion brew is independent of the amount of liquid retained. More liquid retained just means you have less coffee in the cup.
Assuming 20% extraction: If Aeropress retains 1.5 g/g, it requires 74 grams of coffee per liter of 1.35 TDS brewed coffee Standard infusion requires 76 grams of coffee per liter of 1.35 TDS brewed coffee Drip requires 67 grams of coffee per liter of 1.35 TDS brewed coffee
Not a big efficiency gain for Aeropress, but it's something.
The slides are still online, but I have a couple of questions for anyone who saw it.
The number for solute in liquid retained for drip is 0.0. That seems pretty incredible to me. Did Vince have any explanation of how this could be? If there are still unextracted solids in the grounds, it seems some would be extracted into the retained liquid. More generally, what was his explanation for the differences in solute in retained liquid between drip and infusion methods?
The liquid retained for both methods is 2g/g of coffee. Is this number going to hold for methods like Aeropress and syphon/vacuum, where air pressure forces liquid from the grounds? If not, will we need to recalculate dosage to account for differences in amount of liquid retained across infusion methods? E.g., maybe a press pot requires a 14% higher dose than drip to reach equivalent strength and extraction yield, but an Aeropress only requires 10%, once we account for the difference in the mass of the retained liquid.
On average, the strength of the solution in the wet grounds at the end of drip is about 1/3 the strength of the solution in the cup/pot.
If your cup is 1.2% strength, the stuff in the grounds is around 0.4% give or take. Little lower extraction, grounds slightly stronger, little more extraction, grounds slightly weaker but the interesting thing is the produced coffee during drip is in the process of being diluted by the stuff coming out of the grounds.
On a 4 minute drip, the ratio of strength in the drip stream vs. strength in the pot settles right around 33%-39% by about 100 seconds into the drip cycle (or where the approximate extraction in produced coffee reaches somewhere around 12%-14%). A couple of checks of diluted espresso pulls after the initial shot (pull a shot, when the barista says "done", catch the next 2-5 grams, allow to cool, dilute with exact amount of water, measure strength) implies similar ratio of strength in the stream vs. strength in the cup - BUT something like espresso has a bit more strength gradient across the puck because of the high water flow during 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
Keep in mind that the "absorption" is important for extraction calculation only for percolation methods. The water brew ratio (or what VST calls "Coffee Brewing Formula") is what is important for immersion/steep.
This all works out to a difference in water brew ratio of around 2 points, or a bit more than 10%.
Typical absorptions:
-Press Pot, 2.8-4.0 and depends highly on the dose vs. capacity, and how much you press the results and how far the brewer allows the press. More press=more sludge. -Clever Coffee Dripper, 2.2-2.4 with a #4 melitta filter. closer to 2.0 with a metal filter. -BCM-4C, 1.75 with a #2 Melitta filter. -AeroPress - 1.8 just to "hiss", 1.2-1.4 if pressed. Slight variation if you use a metal vs. paper vs. filter felt -Chemex can have some variation, somewhat filter dependent. The large square filters can be 2.6, the round ones a little lower. Metal (which I don't have) cone probably closer to 2.1 -Bunn and most flat bottom, tend to be right around 2.0 if brewed to more than half capacity. -Espresso tends to be right around 1.1
Defining P as grams of produced coffee C as grams of brew coffee (ground coffee ready to brew) W as grams of brew water (water ready to brew) R is the ratio of W:C, = W/C A is the ratio of (W-P)/C, and can be practically applied as a constant for the brewing system. T is total dissolved solids (aka "TDS") that are removed from the coffee C E is extraction, the ratio of T:C, = T/C S is strength, the ratio of T:P, =T/P, but must be careful that the "produced coffee" for immersion/steep is made from all of the brew water, not just the stuff in the cup/pot.
For percolation: E = S * (R - A)
For immersion/infusion/steep: E = (S * R) / (1 - S)
If you define Y as a yield ratio of produced coffee P to brew Coffee C, Y = P/C which also means that Y = (R-A).
So for percolation methods like espresso - or basically all percolation methods that use yield to calculate extraction: E = S * Y
and if you want to know how much coffee you'll get:
P = W - (C * A)
The brewing control charts are specific to an absorption of approximately 2, give or take, if you think of the measured volume in cold (room temperature) water. "Investigating the Brewing Control Chart"
I'll post some examples in next post.
Bottom line:
Same brew ratio, steep/infusion/immersion methods extracted to same amount will result in approximate 10% lower strength. if you set up a brew of each method, same brew ratio, extracted to 20%, if the percolation brew is 1.22%, the immersion brew will be 1.10%
To get the same strength and same approximate extraction between percolation and immersion, you need to bump the brew ratio about 10% stronger: -to get a percolation and immersion brew at 20% extraction at the same strength (say approximately 1.25%), the Percolation brew needs to be about 18, where the immersion brew needs to be about 16.
If you want to "design" a cup of coffee, determine the amount you want (in grams). Assuming you want it at 1.25% strength (a typical strength) then divide this desired amount by 16 to determine the amount of coffee you need to make it (assuming you achieve the 20% extraction) using percolation.
(example, if you want 350g of coffee, you need to use about 22g (350/16) of coffee if you do it by percolation)
Assuming you want it at 1.25% strength but you're using immersion to brew it, divide this desired amount by about 14. (example, if you want 350g of 1.25% strength coffee in your cup, you need to use about 350/14 or more like 25g of coffee).
To figure out your brew water amount, just take your desired coffee amount and bump it by 10-15%.
You want 350g of coffee, use about 390-400g of brew water.
All these are approximate, because people rarely know what their absorption is. Furthermore, people pretty much never know how much moisture or CO2 is in your brew coffee.
The difference between immersion and percolation amounts to changes of about 10 percent in the strength or brew ratio, given a particular EXTRACTION - but here's the rub:
Extraction is governed mainly by the brew recipe (NOT including the brew ratio). This is the grind level, the contact time, and the temperature. You control extraction by those three variables, but we can NEVER MEASURE EXTRACTION DIRECTLY. So these errors between "extraction" measurements are really errors in the resulting strength given similar extraction (and taste profile).
Yield-based extractions for Immersion brews are off by how much good coffee is stuck back in the grounds (as opposed to 1/3 strength coffee like in percolation) - so the error is somewhere between 10-20% for backcalculated extraction (which ALL extraction is, really). I'll show those on the next post examples.
------------------------------------------ ----------------------------------------- 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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