Coffee Data Science
Improving Travel Espresso using Thermal Pre-Infusion
Heating on my mind
I typically bring my own coffee setup when I travel to insure I get good coffee. However, this has always been a challenge. My travel espresso is never as good as my home espresso, and I have tried all the tricks. After working on thermal pre-infusion, I started thinking how I could implement this concept while traveling.
Thermal pre-infusion brings the coffee grounds temperature closer to the brew water temperature, and this is key for high coffee extraction. Water temperature is already volatile close to the boiling point and drops quickly when not in a pressurized system.
Luckily, travel mugs offer a great solution. Travel mugs are insulated to maintain the temperature (hot or cold) of the liquid inside. So I thought I could utilize this feature to heat my coffee grounds and get effective thermal pre-infusion.
First, I pour boiling water into a travel mug. Then I use a Kompresso, and I sit it on top of the mug. I wait for a few minutes and then pour water in the top to start the brew.
You can also pull the pump up during the thermal pre-infusion to draw in the steam coming off of the boiling water.
I did a quick test with spent grounds inside the transparent part of Kompresso, and I could see moisture forming inside. This verifies that the steam is penetrating the coffee as desired.
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
I didn’t do an extensive data collection, just two shots. So this is a feasibility study at most. The difference in performance was very noticeable.
There is a clearer difference in the EY. The TDS is lower because the output was a little higher for the second shot, but the IR shows a better outcome using Thermal PI.
While the data was small, it holds promise for improving travel espresso with the tools that are easily portable. Heat loss has always been my major concern, and thermal PI can help mitigate my travel woes.
If you like, follow me on Twitter, YouTube, and Instagram where I post videos of espresso shots on different machines and espresso related stuff. You can also find me on LinkedIn. You can also follow me on Medium and Subscribe.
Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
