Coffee Data Science
Intentionally Double Roasted Coffee
Change from accidental to intentional
I have accidentally dropped a few coffee roasts before the first crack. Each time, I was quite frustrated, and I was left with the option to re-roast the coffee or throw it away. I chose re-roasting figuring I could use the coffee for milk drinks if all else fails. I have been surprised that the roasts were pretty tasty.
Therefore, I decided to intentionally double roast on the Roest. I aimed to drop the coffee at 200C right before the first crack. After the coffee cooled, I put it back through the roaster.
Post-Roast Metrics
The double roasted coffee had more weight loss but a similar density.
Moisture was similar for both.
Roast color was very close, so hopefully that means the main differences in taste are due to the roast not the development time.
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
A small sample of data showed the double roasted coffee tasted better. This was an interesting result.
The resulting taste didn’t seem attributed to extraction efficiency.
This initial test suggests more investigation should be done. Traditionally, roasting quickly is better for production coffee roasting in terms of time efficiency, but for home roasting, there is an opportunity for optimized roasts where time is not as important as quality.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
