Coffee Data Science
Initial Testing of Heat Soaking Coffee Post-Roast
More post roast processing?
I was chatting with Harry Kimoi about heat soaking coffee after the roasting. He find some of a taste difference, so I decided to try some heat soaking. Heat soaking has been used in a few ways in industry to help improve robustness.
I didn’t want to continue the roasting process, so I kept the temperature low. I did a 10 minute heat soak in a 50C instant pot. I made three roasts of the same beans, mixed them, and split them into three roasts to form:
- Baseline
- 10 minute heat soak
- 20 minute heat soak
Afterwards, I added my normal 4% moisture.
Tasting Equipment/Technique
Espresso Machine: Decent Espresso Machine, Thermal Pre-infusion
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Pre-infusion: Long, ~25 seconds, 30 second ramp bloom, 0.5 ml/s flow during infusion
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).
Shots
I was surprised at how much better the heat soaked shots were in taste.
They did not extract any higher, so I’m not sure what the mechanism is occurring.
I had thought heat soaking might help in degassing, and maybe that was the mechanism at play, but the extraction yield numbers didn’t suggest heat soaking was more efficient.
Given the feasibility experiment went very well, my next step is to make a few more roasts in a similar manner and compare a baseline to a 10 minute heat soak. 20 Minutes didn’t seem to do much more than 10 minutes, and I would prefer to keep the post-processing times to the minimum.
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
