Coffee Data Science
Reusing Coffee in Espresso
Another weird thing to try
I have been working through an experiment set for a single shot to see if I could use a screen and a spring to pull a good single shot. In the middle of these experiments, I messed up my puck preparation resulting in a channel straight down the center. Out of curiosity, I wanted to see if I could prepare the puck again and extract the rest of the coffee.
Quantitative Metric
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).
Equipment/Technique
Espresso Machine: Decent Espresso Machine
Coffee Grinder: Niche Zero
Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)
Shot Preparation: Staccato Tamped
Pre-infusion: Long, ~25 seconds
Infusion: Pressure Pulsing
Filter Basket: 20g VST
Other Equipment: Atago TDS Meter, Acaia Pyxis Scale
First Shot
The first shot was 6g in, 18g out, and it channeled a lot. It was 4% TDS at 12% EY.
When I opened the puck, it was a mess, but I got to thinking. Could it be saved?
I mixed the puck, and I got it into a good shape. I measured the liquid at 8.25% TDS, so there was still a bit of solubles to extract.
Reused Coffee
I put it in, and I pulled the shot. It went far too long, but it pulled pretty evenly.
Afterwards, the puck looked a lot better and solid.
The coffee measured 25g out at 3.5% TDS. This meant around 14% EY. So it was definitely recoverable.
This test was an interesting one-off to see what would happen. I tasted the shot, and it was missing a lot like the first shot’s worth of goodness. But nonetheless, had I kept the first shot around and recombined it, it could have actually made a good drink.
This is also useful to consider if you greatly mess up your puck, and it is having wild channeling, you could stop the shot, redistribute, and continue to pull the shot. It probably wouldn’t make the best neat espresso, but it could still mix well with milk.
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