Coffee Data Science
Spiked Coffee Roasting
A renewed effort to make a bad roast
My experimental philosophy has been that experiments to try to worsen coffee roasts are as important as experiment to find improvements. The bad roasts tell how much effort it takes to make a bad roast or a truly terrible roast.
Initially, I wanted to look at coffee tipping with this spiked inlet temperature experiment, but in initial measurements, the rates of tipping were the same for both. So the experiment wasn’t able to speak to tipping well, but it could still inform later experiments.
I designed this profile to spike the inlet temperature and the fan speed at the same time. Otherwise, the fan speed would be low.
Post-Roast Metrics
The two roasts had similar metrics.
There was a slight difference in coffee color. The Baseline final bean temperature was 214 C compared to 211 C for the Spiked, which explains why the Spiked roast was a little 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
Across four shot pairs, the baseline was better across the board, but only by 2 points. I thought it would have been worse. The spiked coffee tasted muted.
EY didn’t show much difference.
In my mind, the difference between a good roast and the best roast should be noticeable and difficult to achieve. I didn’t think making a really bad roast would require more effort. It is possible the low fan speed in-between spikes is providing a benefit that counteracts some of the temperature spikes.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
