Coffee Data Science
Coffee Grinders: Momentem vs SPK58
A small comparison
While traveling, I brought my Momentem grinder, and I compared it to an SPK58 over a few weeks. The Momentem had a slight improvement, and I wonder if that was simply from the chaff collector. The more I consider the Momentem grinder, the more I suspect the chaff collector is the defining feature.
Caveat: the data set is very small, only 14 shots using 6 roasts.
Result: Momentem outperformed the SPK58.
I previously compared the Rok hand grinder to the Niche, and the Rok won out.
Tasting Equipment/Technique
Espresso Machine: Kim Express, Thermal Pre-infusion
Coffee Grinder: SPK58 and Momentem
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 had 14 paired shots of espresso, and there were a few shots where the Momentem seemed not to be as good. The challenge with shot comparisons is often time of day and what I had been eating.
Looking at the averages, the Momentem does slightly better.
Looking at statistics, in terms of taste, the Momentem does not have a statistically significant difference according to a two-tailed paired t-test.
There were two large outliers, and I could remove those two outliers just to see.
This showed a bigger gap for taste except for sour and bitter.
This gap seems to be statistically significant, and at the very least, I have a feeling more shots would improve this difference.
In terms of extraction efficiency, the Momentem was better. This could have been partially attributed to chaff being removed, or some chaff being removed. It is unclear how chaff effects extraction efficiency.
I feared when buying a hand grinder, that I would be compromising on shot quality. How could I be so sure my effort in grinding by hand would impact the cup? These results plus prior results comparing the Momentem to the Niche seem to show the Momentem is at the very least as capable as these electric grinders.
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Further readings of mine:
My Second Book: Advanced Espresso
My First Book: Engineering Better Espresso
