I don’t brew pour-over coffee, but I thought I could do a hack to test the technique. It was fascinating to me because the academic results weren’t out yet.
So I used a massage rock made of basalt and put it in the freezer.
The first few tests were so successful that I didn’t want to do regular paired photos. But I did it for the sake of learning.
Coffee Maker: A decent coffee maker
Coffee grinder: Zero niche
Coffee: Home Roasted Coffeemedium (First crack + 1 minute)
Shot Preparation: Staccato Tamped
Preinfusion: long, ~25 seconds
Infusion: pressure pulsation
Filter basket: 20g VST
Other equipment: Atago TDS meter, Acaia Pyxis scale
To evaluate the differences between techniques I used two sets of metrics: Final Score and Coffee Extraction.
Final result is the average of a scorecard of 7 metrics (edged, wealthy, syrupy, sweet, sour, bitter, and aftertaste). These ratings were of course subjective, but they were calibrated to my tastes and helped me refine my shots. There is some variation in the results. My goal was to be consistent across each metric, but sometimes the granularity was tough.
Total Dissolved Solids (TDS) is measured using a refractometer and this number, combined with the output weight and input weight of the coffee, is used to determine the percentage of coffee in the cup, called Extraction Efficiency (EY).
Intensity Radius (IR) is defined as the radius from the origin on the control chart for TDS vs EY, so IR = sqrt( TDS² + EY²). This metric helps normalize shot efficiency across the entire output efficiency or brewing ratio.
I tried 8 coffees out of 20 paired samples. I found that the chilled shots tasted better. The readings showed a slightly higher TDS/EY, but that could be because the sample was colder.
