Coffee Data Science
How Can One-way Valve Coffee Storage Tubes be Bad?
I really want to know
After some testing showed single dosed coffee improved taste, I bought the Normcore single does tubes with a one-way valve. My hypothesis was that the one-way valve would not improve taste performance beyond tubes without a one-way valve. I was wrong in that I assumed the performance would be the same: one-way valves performed worse.
Initially, I just wanted to show that the added cost of these tubes was unnecessary, and now I’m down a different rabbit hole to understand what went wrong.
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 collected 21 shot pairs over multiple roasts and bean origins. The one-way valves under-performed and by a lot.
Every taste category was affected.
TDS and EY were not affected.
All the taste differences were larger than the taste differences of the baseline tubes vs no tubes. The differences in taste between the one-way valve and baseline were all statistically significant using a two-tailed paired t-test.
This experiment defied my expectation, and for my next trick, I will try to root cause the failure of these one-way valves.
If you like, follow me on 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
