jpender Senior Member Joined: 11 Jul 2011 Posts: 732 Location: California Expertise: I like coffee
Grinder: OE LIDO Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Wed May 16, 2012, 1:00pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
The thing is, it doesn't even matter what the absorption constant is so long as it matches the brew. That's why it's an input parameter in the Mojo software. Except that they use a different definition. Their "water loss" in g/g is basically your absorption constant + 0.2. So if the grounds are absorbing 2.0 g of water per gram of initial grounds then that's approximately the same as your choice of 1.76.
If I were using Mojo for my brewing I would input a lower number as I almost never see anything close to 2g/g of water retained in the grounds.
The apparent linearity of these results could be a coincidence.
If higher brew ratios (lower temperature profiles) result in lower effective extraction AND the grounds liquid is actually something less than full strength coffee then you could get a result that looks like the grounds liquid is full strength when it isn't.
For example, if the brew ratios are 6%, 12%, and 18% and the strengths are 1.3%, 2.6%, and 3.9% it looks like the grounds liquid strength equals the cup strength. That would imply an effective extraction (all the liquid) of 21.7% for each of the three brews. They might taste "okay".
But what if the strength of the grounds were actually only 50% of the cup strength? Then the effective extractions would be 20.8%, 19.8%, and 19.0%. These might all taste okay too.
The problem is that we don't know if our lone taster can reliably resolve differences of this magnitude. If he can only say "underextracted", "okay", "overextracted" with certainty it leaves a fair amount of wiggle room.
I'm not sure that your presciption for adjusting the temperature makes sense. I've spent a little time recording Aeropress temperature profiles and the concept of a "hit" temperature as a way to guarantee equal extraction profiles seems like a reach to me.
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