Coffee Data Science
Low Fan during Drying Phase Improves Coffee Roasting
More fan manipulation
Previously, I looked at the fan speed during the drying phase, and I found a lower exhaust fan speed improved flavor. So I expanded my test set across a few more roasts, and the results consistently point to a lower fan speed improving the roast.
Post-Roast Metrics
I looked at four roast pairs, and their post-roast metrics didn’t show much difference between baseline and low fan dry (LF Dry).
Most importantly, this was true for coffee color. This allows for a fair comparison between the baseline and low fan dry.
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
I pulled 16 shot pairs, and only one shot pair showed that the baseline was better.
The taste panel also showed a consistency over all the taste metrics I use in terms of an improvement.
TDS and EY remained roughly the same.
Using a two-tailed paired t-test, all the differences seen in taste were statistically significant.
I’m excited to learn a bit more about the drying phase, and I’m going to see how much lower I could drop the fan speed across the beans using the internal fan setting.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
