Coffee Data Science
Slow Maillard for Coffee Roasting: Fan Optimization
Quacking to the finish
Initial experiments showed slowing the fan down during the Maillard process benefited espresso taste. I expanded on this feasibility experiment to see if this result was a fluke or something I should use regularly in my profile.
As a refresher, the Slow Maillard adjusted the fan down slowly starting at 150 C, and then the fan speed was ramped back up to 75% at 200 C.
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 over 4 pairs of roasts. The data had strong signal that slow fan during the Maillard was better.
Individual taste components show the biggest increase in sweetness.
TDS/EY showed about the same performance.
The taste metrics for Sweet, Sour, and Final Score had statistically significant (two tailed paired t-test) improvements while Bitter and Aftertaste were close to the 0.05 threshold of statistical significance. This is due to the two outliers, and a larger dataset would help verify. At the moment, I’m aiming to repeat some of these tests as other variables become more clear.
I switched my baseline profiles to use the slow fan during the Maillard process as a result of these tests. I suspect I will have to revisit these findings as I optimize other parameters.
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
