Coffee Data Science
Higher Charge for Better Yemen Coffee Roasting
Fixing mistakes!
I love Yemen coffee. It is funky and different, but it is hard to roast. I got some recently, and I was having some trouble. Hiver at Chromatic Coffee told me to use a higher charge temperature. So I went home and got to roasting.
Charge temperature is the inlet temperature before the start of the roast. I had done some experiments on it, but I hadn’t quite found the groove. So I started with Yemen, and I also did some other charge experiments. I want to focus on Yemen coffee just for this experiment to highlight how special it is.
Post-Roast Metrics
After roasting on the Roest, I didn’t get as close based on final bean temperature (212 C) as I had wanted. Weight loss was fine, but density had a difference.
Bean color was a little bit different, so I was worried because 230 C was a little darker (lower Agtron color is darker, higher number is lighter).
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 did 4 shot pairs, so this is still in the realm of feasibility data. However, in these shots, the 230 C charge was the clear winner. This is interesting especially because based on coffee color, the higher charge coffee was darker yet better tasting.
EY did not see any effect, but I report it just the same.
I’m excited because I think I’m getting closer to the maximum potential of the Yemen coffee. I’m also excited that this experiment is part of a larger set of experiments to explore optimal charge temperatures.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
