Why TDS/extraction yield measurements are not a good way to evaluate taste profile/quality? - Page 4

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ds

Postby ds » Mar 15, 2019, 4:29 pm

samuellaw178 wrote:Same/similar grinder, same TDS/EY, same coffee, same extraction metrics (contact time, brew ratio, and what have you), and the TDS/EY is likely still not a good predictive indicator that the shots will taste the same (in relation to the 'standard/control shot' with the same parameters).


At least in case of Niche, Niche will have noticeably different enough particle size distribution just because of all the play in shaft and outer burr carrier. And its not little play, its visible by the eye play. So the burrs will "walk" around as they are grinding and bell curve of particle size distribution will be stretched out. Conical burrs don't self center, but rather "walk" and wobble unless they are constrained and you can see that in action if you have hand grinder with radial play in center burr.

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another_jim
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Postby another_jim » Mar 15, 2019, 6:09 pm

Balthazar_B wrote:Perhaps you've run across this document already?


Not me, thanks. Looks like the principle components summary of the analysis can ID the different coffees. That would be a fairly huge deal for Kona and Blue Mountain growers, since they are both plagued by fakes. But the result is not the same as previous reports of using GC/MS analysis on coffee. These could pick out the compounds, but not reliably distinguish different types of coffee.
Jim Schulman

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another_jim
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Postby another_jim » Mar 15, 2019, 6:13 pm

ds wrote:At least in case of Niche, Niche will have noticeably different enough particle size distribution just because of all the play in shaft and outer burr carrier. And its not little play, its visible by the eye play. So the burrs will "walk" around as they are grinding and bell curve of particle size distribution will be stretched out. Conical burrs don't self center, but rather "walk" and wobble unless they are constrained and you can see that in action if you have hand grinder with radial play in center burr.


Somewhat OT, n'est pas? And if you're referring to the screw on the conical burr, they visibly "wobble" on all grinders; just like my :roll: Otherwise I congratulate you on your sharp vision noticing the actual center burr wobble.
Jim Schulman

ds

Postby ds » replying to another_jim » Mar 15, 2019, 7:05 pm

Not really. You can visibly move center and outer burr on Niche by hand so they will "walk" once they start grinding...

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Balthazar_B

Postby Balthazar_B » Mar 15, 2019, 10:56 pm

another_jim wrote:Not me, thanks. Looks like the principle components summary of the analysis can ID the different coffees. That would be a fairly huge deal for Kona and Blue Mountain growers, since they are both plagued by fakes. But the result i not the same as previous reports of using GC/MS analysis on coffee. These could pick out the compounds, but not reliably distinguish different types of coffee.


Scientists have been doing DNA analysis on coffee varietals for nearly 20 years. Pretty interesting stuff; mostly they've been studying how genotypes and hybrids can be traced from coffee's original species. Now if specific varietals/cultivars have distinct markers, I suspect this testing -- which is getting faster and less expensive by the month -- could be leveraged to confirm authenticity of Kona, etc.

Lots of papers/abstracts online if you google for them. Many (most?) will be coherent only to geneticists and molecular biologists. :)
- John

LMWDP # 577

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NelisB

Postby NelisB » Mar 16, 2019, 4:14 am

Thanks for your post! It makes a lot of sense to me.

But why is this? Did I miss your explanation?
Jake_G wrote:Conversley, the wider spread will taste better than the tight spread at low extraction yields

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Jake_G
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Postby Jake_G » Mar 16, 2019, 10:30 am

Yeah, my post was real bad :oops:

I hit submit before I meant to and then put an edit there to help clarify but even that was bad :lol:

I'll work on a response to your question, but it might be a little while. The general idea is that since the flow rate in any puck is optimized for the average particle size, larger and smaller particles will extract more or less that the target particles. The amount of solids that they contribute to the whole should be based on the amount of their combined surface area. Smaller particles have more surface area per gram than big ones, so they'll give up more solids (per gram) than bigger ones. Likewise, the bigger particles will give up fewer solids than the smaller particles.

If you were to do EY% for each particle size, you would find a gradient of high extraction yield for small particles to low extraction yield with large particles with the average EY% being close to the extraction yield of the average sized particles.

I still think that contact time and concentration gradient leads to the boulders being the offensive party here that makes wider particle distribution shots taste over extracted at lower extraction yields than tighter spreads, but I need to collect my thoughts and compose something that is actually intelligible. Gimme a little time on that front :wink:

Cheers!

- Jake

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NelisB

Postby NelisB » Mar 16, 2019, 11:51 am

I don't see how short shots would benefit from a wider spread particle size distribution. I would say that a tighter distribution works better for all extraction lengths.

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Jake_G
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Postby Jake_G » Mar 16, 2019, 12:24 pm

Sorry, poor wording.

If you were to take a wider distribution grinder through the range of EY% from very low (short shots with coarse ground coffee) all the way to very high (long shots with very finely ground coffee), my assumption (given my rambling talk of particle distribution and flow rates and contact time, etc...) is that the flavor would be best (tasting neither under, nor over extracted) for this particular grinder and coffee at a lower extraction yield than it would if the same experiment were carried out on a grinder with a tighter distribution.

Does that make sense?

This is my take on the whole "EK43s taste under-extracted at anything under 21%" sort of thing. It's not that the wider distribution grinder at lower EY% will taste better in absolute terms than a tight distribution grinder, but the relative maximum for balanced flavor for a wider distribution grinder should occur at a lower EY%.

As I said before, I should have spent more time putting my first post together...

Cheers!

- Jake

OldNuc

Postby OldNuc » Mar 16, 2019, 1:16 pm

For consideration.
A refractometer is a device that is intended to respond to the change in the refractive index of an unknown mixed solution compared to the refractive index of pure water. It only works with a solution, any particulate in the solution distorts the results in an unanalyzed manner.

Particulate concentration in water is determined by using a turbidity measuring instrument and it is eliminated or reduced by filtration.

TDS instruments are just measuring conductivity that is the result of the total contaminates in solution. The particulate results in the scattering of the light beam that the refractometer is utilizing to project onto a CCD or scale.

Unless all particulate is removed from the sample the results will likely be random and unrepeatable.

In a post above Almico mentioned several more causes of non-repeatable results.
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