Coffee Data Science
Steaming a Double Roasted Coffee
More weird experiments
I did some intentional double roasts in the past, and I have also added moisture to green coffee. I decided to try some double roasts with adding moisture in between the two roasts just to see what happens. All roasts were done on the Roest.
Roasts:
- Baseline
- Double Roast: first roast dropped right before the first crack.
- Steamed Baseline using an instant pot with water at 93 C, setting coffee on a metal pan.
- Steamed Double Roast, doing the same as the steamed baseline after the first roast but before the second.
Post-Roast Metrics
The weight loss was different for the double roasts because of the double part. However, the density was the same for most.
Moisture was higher for the steamed but only slightly. Coffee color was very close for the first two, but the last two had very different end colors.
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 four shots, and these represent only a feasibility. I didn’t find much change in taste aside from the steamed roast, which was also lighter than the rest (higher Agtron color).
Resorting the data by roast, the conclusion seems the same.
EY didn’t show much except for a lot of variations on the last shot set.
These results suggest steaming might be interesting to look at again, but other than that, the double roasts were not interesting in either a good or a bad way. A better control on end roast color may have helped better isolate variables.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
