Coffee Data Science
Super Refined Charge Temperatures for Coffee Roasting, Part 3
Super Charging forward!
Previous charge tests showed a higher temperature was better for taste. I initially look at 100 C, 191 C, and 300 C. Then I refined to 150 C, 191 C, and 250 C, which showed 250 C improved performance. Is there a more refined temperature between 191 C and 250?
So I modified the range of charge temperatures to test:
- 191 C (baseline)
- 230 C
- 250 C
Post-Roast Metrics
The roast metrics were pretty similar.
The color was a bit lighter for the 250 C roast than I wanted, but it is close enough for this small test.
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 shot sets, and both 230 C and 250 C are better than the baseline. Additionally, there is a trend of 250 C being better than 230 C.
Re-organizing by set, the added variable of time shows each set having a slight decrease.
EY had a slight effect, a slight increase for higher charge temperature.
This feasibility test showed 250 C is a pretty good point. I could potentially try 275 C, but there was a loss of benefit at 300 C. For now, I will proceed with a larger test set comparing 191 C and 250 C to better confirm this feasibility finding.
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
