Coffee Data Science
Dropping Some Pulses during Coffee Roasting
Examining the beginning and ending
Diving into thermal pulsing, I have been removing parts from the roast profile to better understand how it works. Initial tests in dropping some of the pulses entirely were interesting. So I explored with taste.
Thermal Pulsing Variants
Here is the baseline Bean Temperature/Inlet Temperature (BT/IT) profile and thermal pulsing.
I dropped the last two pulses, but it looks like I just dropped one; it just went flat.
This dropped the first two pulses, but it looks like there is an extra pulse because of the second half starting on a drop in temperature.
Roast Statistics
Most of the post-roast measurements showed similar readings except for water activity.
Weight loss was pretty similar.
Moisture didn’t move much.
Water activity was very different. I’m not sure what exactly that means or rather if it is predictive or not.
Color level was on point.
The same was true for density.
Tasting Equipment/Technique
Espresso Machine: Decent Espresso Machine, Thermal Pre-infusion
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Pre-infusion: Long, ~25 seconds, 30 second ramp bloom, 0.5 ml/s flow during infusion
Filter Basket: 20 Wafo Spirit
Other Equipment: Acaia Pyxis Scale, DiFluid R2 TDS Meter
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).
Data
I pulled four shots for each roast, which is enough to give some intuition at how the different changes affect taste. My goal is to understand what is the most important in a thermal pulsing profile.
EY was about even across the shots.
These tests suggest dropping pulses doesn’t necessarily help. If you squint, it looks likes dropping pulses negatively effects taste, but really, the difference doesn’t look like much. I should try dropping the middle two together and separately. I also want to test the maillard reaction because I suspect I am elongating the reaction, but I would like to do that in a more controlled way (or maybe just less complicated).
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
