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Refractometers
I've been reading about determining total dissolved solids and extraction yield with a refractometer. It's said to make dialling in a new coffe quicker and more accrate than relyng on taste alone. Has anyone tried this procedure with their Londinium?
Matt
Matt
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with a bit of luck Frans will pop up in a few hours and share his thoughts
no doubt there are others too
it certainly doesnt give a 'number' for the optimal extraction for a given roast though as frans has run the same roast through the E8 and the R120 and achieved similar numbers from the refractometer (20.9 vs 21.1 from memory), yet vastly different levels of performance in terms of the taste in the cup
reiss.
The one from VSTlabs also has a matching iPhone app (the latest, a PRO version, with all the features of the app for desktop computers) so you will know what to do with the readings. The refractometer itself shows you the TDS in the cup and the app, when you feed it the weight of the dose of coffee in the portafilter, and the weight of the extraction, will show you how much of the coffee in the puck was actually dissolved into your cup.
It does help to know how the extraction went and you can use the outcome to find suggestions how to proceed. For instance, if the extraction is on the low side, you can decide to grind finer / dose less or extract more and then it's still up to you to taste the result and see if you were right. A low extraction could also tell you that the roasting was short or low in end temp, for instance if the bean is also a bit light in color and hard to bite if you chew one up. The coffee could even then be excellent if you dose higher, for instance 22g in a 22g VST basket extracting 40-44g espresso.
You can use the refractometer to help recognize the "mouthfeel" of an extraction. A thin mouthfeel also has a low TDS, for instance.
And you can compare tamping results. A friend (Jan van der Weel) and I are working on a series of tests with tamping pressure. Before, we did a test comparing convex and flat tampers. The flats were a little better (gave higher extraction percentages) across most measurements, but not as dramatically as someone on Twitter had reported. That person had published a "mind blowing" difference but after we sent him our results and asked for his data, he said he needed to look into it again and then fell very very silent ;-)
Also, you can use the tools to compare grinders. Jan and I recently compared the same coffee beans (roasted fairly light for espresso, measured Tonino #101), the same dose, in a grind setting that delivered the same flow and weight in the same time, but from two different grinders. The extraction percentage was practically identical but one grinder allowed a more explicit description of the taste. I compare this effect to what happens if you have a fan, the paper kind to wave cool wind into your face. You can snap the fan closed, and open it partially or complete and if there's a pattern printed on the paper or cloth, the wider you spread the wing of the fan, the better you see it and it may look totally different if only partly opened.
The E8 grinder delivered a delicious espresso and the much bigger and heavier R120 grinder delivered a delicious and more pronounced taste.
Londinium Bolivia Marcelino Katan, Tonino #101
Compak E8
18.3g in
40.2g out in 40s
9.07% TDS
20.8% extraction
well balanced espresso with a thick round moutfeel
transparent flavour is light (delicate) chocolaty, medium/ low lemony acidity
pleasant lingering aftertaste
Compak R120
18.3g in
40.65g out in 40s
9.14% TDS
21.1% extraction
well balanced espresso with a thick creamy round moutfeel
transparent flavour is light (delicate) chocolaty, bay leaves, liquorice, heavy winey, low lemony acidity
pleasant lingering aftertaste
Matt
http://kostverlorenvaart.blogspot.nl/2015/03/tamper-base-flat-or-convex-best.html
I conducted a small test to demonstrate the difference in extraction yield between various tamper designs. With the same grind setting, dose and beverage yield, I averaged 5 separate extractions from each of the 5 different tampers. Here’s their average extraction yields:
American Curve 58mm: 16.9%
C-curve 58mm: 16.8%
Flat 58mm: 17.5%
Flat 58.35mm: 17.8%
Pergtamp: 18.9%
Keep in mind that these are all average values taken across 5 shots. The C-curve sometimes dropped to 16%, and the 58.35mm did reach 18.2% once, but the Pergtamp never dropped below 18.7% or exceeded 19.1%. Consistency and a higher extraction are major factors in a tamper comparison.
This comes from his post in favour of his own commercially available tamper:
http://cargocollective.com/mattperger/Pergtamp/.Vpz1nDbfbiA
Matt
This is an article Jan van der Weel and I published about tampers (in Dutch):
[img ]http://kostverlorenvaart.nl/temp/koffie/ktc/tampen-ori.jpg[/img]