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November 30, 2009

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mike P

forgive me if what follows is not as well formed of a thought as it should be but your touching on somehting I have been thinking about for a bit... You mention that compounds in coffee extract at different rates making coffee that is brewed quickly taste different from coffee that has an extraction time stretched longer. then after that you mention that golden rule of 20% that people have been speaking about lately. does this imply that you can potentially get 20% extracted from the same amount of beans using multiple times/grind settings that will all taste differeent? If so then which 20% is the magic one? Am I way off base on this?

Daniel Humphries

Mike:

I've wondered about that too. My speculation — and my anecdotal experience — suggests that, no, not really. You can't get different 20%'s (percentseses?) that all taste different out of one coffee. Maybe there's some difference at the margins. I think that with radical differences in temperature, you sometime get surprisingly different tastes from an espresso that aren't necessarily "classically" under- or over-extracted tasting. Maybe those are instances of taking out different proportions of different solubles while still taking out the same overall amount of solubles.

However, I'd be surprised if this is anything other than a marginal phenomenon. Caffeine, for example, dissolves almost instantly in water. I don't think that changing grind size or temperature or dwell time or pressure or anything else is going to change that, and I suspect most of the compounds have similar "set extractions."

But I haven't seen data one way or the other. What you need is a spectrometer and the ability to do trace analysis, and then a team of expert cuppers to cup blind several times to see if there is (a) any difference in which 20% is coming out and (b) if it actually makes a tasteable difference or if this is all just wasteful nerdery. Sounds like a vacation to me, actually!

But this is the kind of thing you are talking about, right?

joe hoppy

I went to ZtarBucks in Plano Texas on Legacy Dr. and my coffee is very soapy looking for over 5 minutes?? WTF? is that normal??

Daniel Humphries

Joe:

I can't picture exactly what you are talking about, but if you are talking about an oily-looking sheen on the surface of the liquid, in a cup of black coffee, those are oils that naturally occur in the coffee bean. The darker a coffee is roasted, and sometimes also the staler it is, the more visible the oils will be. Maybe it was that.

Michael

I know I'm a bit late commenting on this post, but it was mentioned that to help get a higher extraction rate "the water needs to spend more time with the coffee". So, for someone brewing at home, would using two filters help? Or am I off base with that one?

This was exactly the post that I was looking for, thank you.

Daniel Humphries

Michael: First try increasing the water temperature. Then try using more finely-ground coffee. Using a double filter isn't really a good long-term solution as it doesn't address the root of the problem.

If you have an automatic machine that doesn't let you control the water temperature, considering upgrading (for much less money!) and getting a hand pour-over system. If you are using pre-ground coffee, invest in a nice burr grinder. You won't regret it!

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