Coffee Data Science
Conical vs Flat Burr Coffee Grinders
Niche Zero vs ODE+SSP
A borrowed a ODE with SSP multi-purpose burrs from a friend, and I took a series of pairs shots to compare it to the Niche. I’ve been particularly interested in comparing flat burrs to conical burrs.
I didn’t notice a big difference in taste, and it is hard to say any differences are due to grind distribution rather than some other property difference of flat and conical.
I started out comparing the particle distributions of both, and once I dialed in the Ode, it was more or less similar to the Niche. It wasn’t as unimodal as I thought it would be, and part of that is due to the burrs not being aligned, which is the main caveat of this experiment.
Equipment/Technique
Espresso Machine: Decent Espresso Machine
Coffee Grinder: Niche Zero and Fellow Ode with SPP Burrs
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Shot Preparation: Staccato Tamped and and Staccato
Pre-infusion: Long, ~25 seconds
Infusion: Pressure Pulsing
Filter Basket: 20g VST
Other Equipment: Atago TDS Meter, Acaia Pyxis Scale
Metrics of Performance
I use two 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).
Intensity Radius (IR) is defined as the radius from the origin on a control chart for TDS vs EY, so IR = sqrt( TDS² + EY²). This metric helps normalize shot performance across output yield or brew ratio.
Paired Shots
I compared 29 pairs of shots over 15 roasts across multiple days of the roast resting. I didn’t notice a great taste difference, but in terms of EY, flat burrs seemed to extract slightly more.
I broke this down further by Regular (Staccato Tamped in this case, but not sifted coffee) and Staccato (three layer sifted). I had 20 Regular shot pairs and 9 Staccato shot pairs.
Again, I didn’t see a big difference in taste. EY seemed slightly higher, but I couldn’t taste it in the cup.
I looked at the individual taste scores as well to see if the Ode gave something different.
I split these results by regular and staccato, and the results seemed mixed.
The difference in Rich and Syrup scores aren’t statistically significant over the 20 pairs with p-values in two-tailed pair t-test of 0.231 and 0.302 respectively which is well over 0.050 for statistical significance. None of the initial taste score differences are statistically significant.
I looked at the overall statistics, and the EY is just over the statistical significant threshold.
I’m sure there are better flat burr grinders and conical burr grinders to compare; both of these performed very similar to one another. The Ode had a slight edge on extraction yield, but with respect to taste, they seemed about the same.
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