Percentage of extraction: Surprising if true!

The following comments are from Barista Hustle

5 months ago

Matt, this series is amazing. We (Triangle Coffee in Somerville MA) are brewing way better coffee because of it, so first off, thank you.
Now for the question: One thing we are trying to do at the moment for our espresso is fix both our dose and the yield and adjust only the grind setting if we want to extract more or less. What I’m having trouble thinking through is how the tamp comes into the picture. If you tamp harder or softer will that change your extraction and therefore change the yield you want for ideal extraction?
For example, we are dosing 18 grams of espresso grinds and shooting for a 27 gram yield of espresso (we’re using Blue Bottle’s Retrofit espresso blend). Lets say you get in in the morning and dial in and get super tasty sweet shots that are taking about 35 seconds to pull. Then for whatever reason you tamp harder on one shot and it takes 40 seconds as opposed to 35 seconds on a normal tamp to get to the desired 27 gram shot. Does this mean you extracted more in the harder tamp 40 second shot? In that case would you ideally want to watch for the blonding point and cut it a bit earlier to make sure you don’t over extract?
Thanks again for everything,
Ottavio at Triangle Coffee

Jon from Black Oak Coffee Ottavio Siani

5 months ago

Otto: in our testing with a refractometer and a robur E grinder we found that we werent able to get much higher than 16.5% extraction with a recipe of 18g in and 27g out (1.5 : 1) brew ratio. The extraction percentage just doesn’t get higher with longer pulls. We found that if you have a shot longer than 22 seconds you generally get the same extraction % up to a 40 second shot. The taste is different, but the extraction is about the same. I’ve never played with the Retrofit, so I’m not sure where it would fall given that recipe.
You really need to use more water to get higher extractions with espresso, assuming you have equipment suitable to the job. This can vary depending on solubility of the extraction, however, with a lighter roasted coffee you tend to need longer shots to get a higher extraction. At least from our testing.

Author: korkiley

Systems Administrator at University of Vermont (retired as of 7/1/2012) Married Favorite Activities: Condor Glider Online Competition, Developing web sites, making espresso, and keeping a blog

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