Changing coffee extraction parameters...
A few weeks ago I mentioned that I was intending to report subjective findings for my experience of espresso whilst changing a couple of extraction parameters. The two extraction parameters were grind size and brew ratio (how much water I put through the extraction relative to the amount of coffee in the portafilter). The subjective measures were: sweetness, sourness, bitterness, fruitiness, viscosity, and overall enjoyment.
One client ("MHP") bravely volunteered to be part of the experiment, referring to themselves as Beaker from the Muppets.
I'll demonstrate the findings as three separate bar charts (each bar chart dependent on the coffee grind size) and also provide some highly subjective commentary.
The findings with the relatively coarse grind were very interesting given that MHP and I both prefer ristretto style short espresso extractions. Fruitiness, viscosity and overall enjoyment all declined as the brew was shortened. These results were unexpected, with viscosity falling with shorter brews being the most unexpected! I postulate that is because the extraction yield (the amount of coffee extracted during the process as a proportion of the overall coffee shot) fell off a cliff due to the combination of coarse grind and short extraction.
Next was medium grind. Most subjective taste parameters improved as the shot became shorter. The results were much more in line with expectation.
Finally, the relatively fine grind. Almost all of the subjective outcomes improved with the shorter shots as per expectation.
If I were to run this experiment again I'd set the extraction parameters wider, particularly the grinder coarseness settings. I'd also set the different brew lengths at more extreme levels. In this iteration a short brew was 22 g of ground coffee in and 29 g of extracted coffee out, with a long brew having the same amount of ground coffee and the extracted coffee weighing about 39 g.
I come away from this with two key summary points. The first is that counterintuitive results can occur with coarser coffee grounds. The second is that MHP and I confirmed that short ristrettos put us in our happy place. Look for the return of Beaker sometime soon!
To learn about the anatomy of a coffee roaster click here
To hear about the roaster hopper click here