CheapBastid Senior Member Joined: 3 Dec 2012 Posts: 62 Location: Los Angeles Expertise: I like coffee
Espresso: None Grinder: Talking myself into a LIDO Vac Pot: None Drip: Mr Coffee Roaster: None
Posted Sat Jan 19, 2013, 11:43am Subject: Re: Temperature and Immersion/Steep Brewing
Netphilosopher Said:
-Take a sample of your coffee, evaporate the water, and measure the residual mass left behind. Think of this as a more direct measurement of Total Solids - but keep in mind that if it comes from a sample that hasn't been well-filtered, it might contain a small amount of UNDISSOLVED solids too.
Yes, but the refractometer methods are calibrated to dehydration/evaporation method.
Generally, volatile oils are thought to be nearly negligible percentage of TDS mass, but yes, technically they may be part of the evaporate.
------------------------------------------ ----------------------------------------- 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
W=grams of Brew Water C=grams of Brew Coffee R = W/C
G=grams of the spent grounds P=grams of Produced Coffee
A="Assimilation" ratio. This is defined as (W-P)/C, or G/C-1 (neglecting evaporation losses, or assuming that W+C = G+P)
S=Strength, or defining T=grams of Total Dissolved Solids in the produced coffee, S=T/P. S (Strength) is the reading you get from a refractometer. In other words, you need a strength measurement, and you need the grams of produced coffee to get TDS (T = S*P)
For percolation methods:
E = S * (R - A), which is basically saying the same thing as E = (S * P) / C
However, for immersion methods the produced coffee is only part of the whole amount of coffee, the rest of what is in the grounds is also coffee too at that same strength.
E (immersion method) = (S * R) / (1 - S)
In your case, if I understand correctly:
W=185g (the water you poured in) C=12g
R=15.417
I'm not sure where you got TDS - this is not a direct reading that you can get unless you did a dehydration (which has its own issues). What you didn't post is P and G - but you need these for a correct calculation. For immersion methods, TDS is only the stuff in your cup, and you're missing the TDS in the grounds. These are negligible for percolation methods, but are very significant for immersion methods, and especially so for immersion methods that produce very wet grounds (mathematically large A, or where G is really heavy).
Now, if your CCD is like mine, then A~2.3 or so, so if your brew water was 185g, your P will be around 157g or so.
If you determined TDS=1.275g, then 1.275/157 is a really low strength of 0.81%. This back calculates to something around 12.6% extraction. Even yield-based calculation doesn't seem right (1.275g TDS / 12g Brew Coffee is only a bit more than 10% extraction).
So, check your numbers, repost, and I'll correct this post.
------------------------------------------ ----------------------------------------- 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
squaremile Senior Member Joined: 6 Jan 2011 Posts: 39 Location: Portlandia Expertise: Just starting
Posted Mon Jan 28, 2013, 8:20pm Subject: Re: Temperature and Immersion/Steep Brewing
So when I look at Vince's talk and slides from NBC2012, here is what you would get from my readings from an immersion brewer like the CCD:
Brew Water: 185g Dose: 12g TDS: 1.27 Bev Wt: 155g ------------------------- Liq Retained: 30g (Water - Bev Wt) Solute in Bev: 1.96 (TDS*Bev Wt) Solute in Ret: .38 (TDS*Liq Ret) Total Solute: 2.35 (Sol in Bev + Sol in Ret, or Brew Water*TDS) Ext Yield: 19.58% (Total Sol/Dose)
Your formula with my numbers gives 19.58 as well in the numerator, but the denomenator being there at all doesn't make sense "/(1-S)" because 1 - 1.27 = -.27. Therefore 19.5/-.27 is a meaningless number (-72.22). What am I missing?
Also if I'm looking at your numbers, I think you have a mistake where you are dividing the TDS by the weight of brewed beverage, rather than multiplying. It doesn't make sense to have a total dissolved solids reading and then divide that number by the water, you should be multiplying to know the total solute in the beverage.
Also since in immersion brewing you don't even need to calculate the liquid retained to get the Extraction Yield because ALL of the brew water is technically brewed coffee. So it therefore goes back to the formula I was running: TDS*Brew Water/Dose or 1.27*185/12=19.58.
jpender Senior Member Joined: 11 Jul 2011 Posts: 428 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Mon Jan 28, 2013, 8:58pm Subject: Re: Temperature and Immersion/Steep Brewing
"Liq Retained: 30g (Water - Bev Wt)" -- that is the error.
You need to consider both the water and the coffee in each step. From your own calculation the beverage contains 2 grams of solubles in 155 grams total. So there is 153 grams of water and 2 grams of coffee solubles in the beverage. From the initial 185 grams of water that means there is 32 (185-153) grams of water is in the grounds. So the "liquid retained" cannot be 30 grams. It's 32 grams plus approximately 1.27%, roughly 32.4 grams.
Work through the math again, carefully, and you'll see where the 1/(1-s) factor comes from.
squaremile Senior Member Joined: 6 Jan 2011 Posts: 39 Location: Portlandia Expertise: Just starting
Posted Tue Jan 29, 2013, 12:20am Subject: Re: Temperature and Immersion/Steep Brewing
OK that makes sense. However, if I recalculate the numbers based on what you are saying, I get this:
Brew Water: 185g Dose: 12g TDS: 1.27% Bev Wt: 155g -------------------------------------- Liquid Retained: 32.37 (Brew Water - Bev Wt + Sol in Bev + Sol in Ret) so (185 - 155 + 1.97 + .41) Solute in Bev: 1.97 (Bev Wt * TDS / 100) so (155 * 1.27 / 100) Solute in Ret: .41 ((Brew Water - Bev Wt + Sol in Bev) * TDS / 100) so ((185 - 155 + 1.97) * 1.27 / 100) Total Solute: 2.38 (Sol in Bev + Sol in Ret) so (1.97 + .41) Ext Yield: 19.83% (Total Sol / Dose * 100) so (2.38 / 12 * 100)
Which is a difference, so thank you, but it is somewhat small and does not explain the denomenator. If you check Vince's calculations on his slides from NBC2012, for immersion brewing extraction yield you can see him do 13.7/60*100=22.8 in the over-extracted cup, and then 13.7/68.2*100=20.08 for the properly extracted. For mine that would be 2.38/12=19.83%. Why do I need /1-S?
It's true that this is only about 1% difference (for this brew) over assuming that TotalLiquid = BrewWater. But it's an easy 1%. Why measure TDS% so precisely and then toss some of that away? Speaking of which, your numbers make it appear that you are measuring water, dose, and beverage weights to a resolution of only 1 gram. If true that would be a much bigger problem.
Posted Tue Jan 29, 2013, 11:29am Subject: Re: Temperature and Immersion/Steep Brewing
squaremile Said:
So when I look at Vince's talk and slides from NBC2012, here is what you would get from my readings from an immersion brewer like the CCD: ... TDS: 1.27...
Unless you mean that TDS is 1.27%... Then this is starting to make more sense.
Keep in mind that the refractometer reads out in TDS%, not TDS. TDS is "total dissolved solids" and is a mass, not a percentage. TDS% is the same thing as "Strength".
Sorry if I misunderstood.
Re-posted corrections.
------------------------------------------ ----------------------------------------- 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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