I think it will decrease with increasing brew ratio.
Ignoring possible temperature effects, as the brew ratio increases there will be a larger proportion of liquid retained in the grounds. Regardless of brewing method there will be some amount of solubles trapped in that liquid so the extraction will decrease.
The brewing control chart assumes a constant ratio of liquid retained per unit measure of initial coffee, something around 2.3. This results in the prediction that as the brew ratio approaches 1/2.3 (about 43%) the extraction will approach zero as all the liquid is retained in the grounds. I'll bet that's not too far from the truth.
But when you ask what extraction should do I think you're after something else, some other metric that corresponds to optimal extraction for a given set of parameters. Maybe there's a nice way to do that, maybe we end up with a bunch of different charts. Consider the guy who sieved his grounds to obtain a very narrow grind profile. His optimal extraction for a given set of brewing parameters changed significantly. What should his extraction have done?
The answer seems obvious, which makes it seem like you're probably asking a trick question. If so, I can't figure out the trick.
Anyway, I would definitely say that as the coffee-to-water ratio increases, the extraction yield decreases. This would be true whether you calculate Extraction Yield (beverage mass x %TDS / coffee dose) or "Adler Yield" (brew water x %TDS / coffee dose).
Chang94598 Senior Member Joined: 24 Oct 2007 Posts: 213 Location: SF Bay Area
Posted Thu May 10, 2012, 8:57am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
Extraction is not linear. On coffee particle sizes =>1mm, the center never becomes hydrated.
Imagine a single coffee ground particle. At the microscopic level, at the periphery, the coffee flavor is extracted, the fibers swell, and form a semipermeable lattice which also traps water. Solvent water then has a difficult time diffuse into the center. So technically, the periphery is over extracted, and the center is never, or under extracted. This was confirmed via electron microscopy on brewed coffee at atmospheric pressure, not espresso nor Aeropress, btw.
In my experience, with the Abid at least, even at 5 minutes, the drink does not taste too much different then 2.5 minutes.
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