Coffee Data Science
Comparing My Espresso to Publicly Available Data
How do other espresso shots look?
I have collected quantitative data like Total Dissolved Solids (TDS) and Extraction Yield (EY) on close to 2,000 espresso shots. I haven’t compared this data to other people’s shots in great detail because the experiments were from varying designs. However, I thought I could for a few hundred of my most recent shots compared to all publicly available data just for fun.
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.
Publicly Available Data
For years, I have been scraping any data or experiment on espresso where TDS/EY metrics were made available. Often, I would plot the data, and I was very curious into how different conclusions could be reached.
So I put together data from roughly 10 sources, and a lot of the data were multiple test series comparing different techniques or devices. I ended up with 1,320 shots of data.
Comparison
I split out my previous shots and my recent shots using a paper star because there was such a huge jump in performance. I added a line representing the 1:1 shot where TDS = EY. Most of the comparison shots were at a 2:1 output to input ratio.
I remade this chart with some guiding lines for IR at 20%, 24%, and 26% to help show the ranges of shots if you diluted my shots to a similar ratio, but if I had pulled the shot longer, the EY would have also increased.
With a modified control comparing IR to EY, we can see some trends.
This data shows that my espresso shots are in a different range entirely. One can always argue about taste being king, but once EY increases by 1 or 2 points, the taste also noticeably improves.
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