Coffee Data Science
Diluting Espresso: Taste Comparison
Let’s give longer ratios a go!
I really like a short shot of espresso, but not everyone does. A short shot is very strong and intense, but when extracted right, it is amazing. So what about a longer shot compared to a shorter shot? How could we compare the two because they will most likely have a difference in extraction?
I have been able to maintain the same extraction yield and increase output ratio by decreasing water temperature and increasing water flow. So the longer shot is less efficient, but we can compare the taste by adding water to the shorter shot.
Equipment/Technique
Espresso Machine: Decent Espresso Machine, Thermal Pre-infusion
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Shot Preparation: Staccato Tamped
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).
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.
Test Shots
For these test shots, the 1:1 had a high extraction yield, and by diluting it, you get to a similar TDS.
The larger differences comes in the taste scoring. My scoring is biased to a shorter shot, but once the ratios and output yields are the same, the 1:1 diluted has the advantage.
My primary question with this short experiment was to understand if it was better to dilute shots or run them longer for a larger output yield. The profile could have had an impact, but my immediate answer is that I would prefer to dilute a shot if I wanted more liquid in the drink.
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
