Coffee Data Science
Water Temperature for Espresso: Pump & Dump
Salami’ing my profile into knowledge
I wish I could say confidently I understand why my espresso profile (the Pump & Dump profile) works so well. I think part of it was trial and error with some knowledge building along the way, but I have some way to go still in developing a deep knowledge base. One way to do that is to collect more data, and in this case, salami shots or measuring extraction at a few points during the shot.
A salami shot can be used to measure extraction as well as better understand when different taste components are extracted into the cup.
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).
I wanted to focus on temperature. I’ve been pushing the Decent Espresso machine past the maximum temperature using the calibration, but I would prefer not to. I do know I get higher extraction that way, but it is not yet clear why. I made this modification by changing the calibration to where 113 C is read at 105 C.
So let’s explore temperature changes to understand how the coffee is being extracted. I used three temperatures, and I expected a linear trend down in extraction. This happened for the first sample, but not the rest.
In looking at the cumulative EY, 113C is the highest, but 105 C and 100 C don’t appear to be much different. It almost suggests something this going on between 113 and 105, but only at some temperature in-between.
I compared the two profiles, and the trends for both were expected. 105 C in this graph is actually 113 C, and 97C is actually 105 C because of the calibration offset.
For this graph, 105 C is actually 113 C, and 92 C is 100 C because of the calibration offset.
The profile curves don’t show something that would explain why extraction evens out towards the end. I wonder what the optimal temperature is or if something above 105 C causes some other variable to be offset in a good way.
For my lever machine, the Kim Express, I have had some different experiences. Originally, I pushed the water temperature closer to 120C to get more even flow, but I have been able to bring that down to 105C after modifying the shower screen. I suspect optimal water temperature for the Decent is closely tied into water input into the puck.
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