Coffee Data Science
Wave vs SSP Burrs for Espresso, Part 1
Can you taste the difference?
I bought the Wave burrs to see how much they could impact espresso on the hope that they would improve flavor over the SSP burrs I currently use. I waited until I had seasoned the burrs, and then I started a comparison of many shots and a few grind settings to better understand the differences in taste. One set of burrs was a clear winner. My primary comparison was to the SSP burrs (Multi-purpose) in the Zerno Grinder.
These were the Wave Burr 64mm Espresso set.
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 preface these findings with these two caveats:
- These are my taste scores only; so others could have other experiences.
- I prefer a 1:1 shot ratio, which is not the general preference of espresso drinkers.
I pulled 31 shot pairs across multiple roasts, and I found the Wave burrs almost always under-performed the SSP burrs.
No particular coffee origin had a pattern either.
I thought maybe I was off on the grind setting for the Wave. I keep my grind setting the same and adjust the dose to make sure there is no headspace instead of adjusting the grind setting to dial in a coffee. So I varied for a few shots to go a bit coarser thinking the grind setting could contribute to the differences in performance.
The Wave grind setting is negative because I didn’t adjust the zero value for the SSP burrs. The zero setting was around -375 for the Wave. -225 is the finer setting, and -175 is the coarser setting.
I didn’t see evidence from this data that I had the wrong grind setting.
SSP burrs were better across all taste metrics.
With respect to TDS/EY, the Wave burrs also under-performed on average.
In terms of general statistics, a two-tailed paired t-test showed all the differences across all the metrics were statistically significant.
This is a curious result for me because I thought or hoped the Wave burrs would be better. Now I want to investigate from particle distribution and particle shape to better understand what aspect causes such a difference in taste and extraction.
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
Collection of Espresso Articles
A Collection of Work and School Stories
Correction
I originally used this image in the article, but the SSP burrs here are the High Uniformity. Those are not my daily burrs.
