Coffee Data Science
Slow Mallaird during Thermal Pulsing Coffee Roasting
More pulsing experiments
Thermal pulsing during coffee roasting showed some great results, which were improved by fan pulsing. What about dropping the fan speed all together during thermal pulsing to slow the Mallaird process? Previous experiments showed this worked for a regular profile.
I looked at four variants in this experiment:
- Thermal Pulsing 4 (TP4) High Fan on Down (of the thermal pulse)
- TP4 Slow Maillard or really slow fan during Maillard reaction
- TP4 Fan Low where I drop the fan speed sharply
- Slow Maillard where the fan speed is low during the Maillard process, but the profile does not have thermal pulsing.
Their roast curves were interesting:
Rate of Rise (RoR) was difficult to compare since there was pulsing, but there was never a crash.
Post-Roast Metrics
All four roasts were similar in weight loss.
The moisture contents were also similar.
Water activity was odd, but I am starting to think the variable isn’t so helpful.
Coffee density had some variation especially for the TP4 Low Fan.
In terms of coffee color, they all came in very close to one another, which is what I aim for in these tests.
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, and nothing stood out.
Even when I reorient the roasts, I don’t see some great improve or decrease in taste. The second shot for TP4 Slow Maillard seems to be an outlier.
All roasts had a similar EY performance.
This test was not too conclusive aside from suggesting that pulsing the fan doesn’t help the roast, but dropping the fan speed during the Maillard reaction does.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
