Coffee Data Science
Exploring Dry Phase During Roasting: High/Low Inlet
Another angle
Until recently, I didn’t worry too much about the drying phase (bean temperature < 150 C), but a few experiments showed I needed to explore more. I started with the fan speed, and now I’m switching to dropping the initial pulse in thermal pulsing during the drying phase as seen below:
Post-Roast Metrics
Weight loss and density were even across the roasts.
Coffee color was a little off even though the roasts were all dropped at 212 C bean temperature. It is still not too far off, just 5 points.
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).
Shot Data
The results seemed inconclusive. I expected Low Dry might be better, and it was some times but not others. High dry was the same as the baseline at best.
In terms of EY, there weren’t many differences.
I will try this experiment again with something more in the middle, but maybe having a pulse is helpful. I should also determine that factor. Like many feasibility experiments, I’m left with a few more questions than answers.
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
