Coffee Data Science
Do Silicone Rings on Top Help Espresso? Part 2
Previously, I found a silicone ring of the coffee puck improved extraction yield on some test coffee. The challenge was that the test coffee was a few months old. What about a few other fresher coffee roasts? Would I continue to see an improvement?
I used the thinnest silicone ring I had, and I started some paired tests with arabica and robusta. The robusta coffees didn’t have taste scores, but the arabica ones did.
Equipment/Technique
Espresso Machine: Decent Espresso Machine, Pump & Dump Profile
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Shot Preparation: Staccato Tamped
Pre-infusion: Long, ~25 seconds
Filter Basket: 20 Wafo Spirit
Other Equipment: Acaia Pyxis Scale, DiFluid R2 TDS Meter
Metrics of Performance
I used two sets of metrics for evaluating the differences between techniques: Final Score and Coffee Extraction.
Final score is the average of a scorecard of 7 metrics (Sharp, Rich, Syrup, Sweet, Sour, Bitter, and Aftertaste). These scores were subjective, of course, but they were calibrated to my tastes and helped me improve my shots. There is some variation in the scores. My aim was to be consistent for each metric, but some times the granularity was difficult.
Total Dissolved Solids (TDS) is measured using a refractometer, and this number combined with the output weight of the shot and the input weight of the coffee is used to determine the percentage of coffee extracted into the cup, called Extraction Yield (EY).
Intensity Radius (IR) is defined as the radius from the origin on a control chart for TDS vs EY, so IR = sqrt( TDS² + EY²). This metric helps normalize shot performance across output yield or brew ratio.
Data
For the 9 pairs with taste data, I didn’t see some massive improvement.
Overall, the average taste components seem too close to call.
In terms of extraction, the results were also mixed.
Zooming-in on just TDS and EY, there was a big mix in performance.
At a statistical level, everything was a wash. No differences were statistically significant.
On one hand, I should have collected more data, but on the other hand, I would need a lot of samples to prove anything good. It is quite possible I needed to use a thicker ring, so I’m going to test that next. But the good news is that the silicon ring did not make anything worse. No regressions is a good thing.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
