Why TDS/extraction yield measurements are not a good way to evaluate taste profile/quality? - Page 2

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jpender

Postby jpender » Mar 12, 2019, 11:40 am

This is so weird to read. Didn't this conversation take place years ago?

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another_jim
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Postby another_jim » Mar 12, 2019, 12:20 pm

Maybe it did; but people are still doing extraction yield bragging. In any case, now that there's cheap gear like the Niche getting high yields; I have a feeling that extraction bragging might go away for entirely unscientific reasons.
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RyanJE

Postby RyanJE » Mar 12, 2019, 12:29 pm

I haven't seen this yet, maybe I just missed it. Isnt the TDS and EY just the average extraction of all the particles that were in the brewed coffee?

If one were to use grinder that produces a very wide particle distribution and get a 22% ey with 1.4TDS and use a grinder that produces all the same size particle to get the same EY and TDS it would of course taste different, no?

Is it possible that what Samuellaw is really seeing between the two grinders is a result of different particle distributions? Hence the reason the big conicals taste better than his other grinder at the same EY.
I drink two shots before I drink two shots, then I drink two more....

happycat

Postby happycat » replying to RyanJE » Mar 12, 2019, 1:50 pm

So... you could use sieving to compare two doses from diff grinders with same EY?

And then relate taste to those distributions? Perhaps by reconstructing the whole dose piece by piece from the sieved grinds?

I am clueless so feel free to ignore :D
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OldNuc

Postby OldNuc » replying to happycat » Mar 12, 2019, 2:19 pm

Even if it worked what would be the practical application?

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Peppersass
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Postby Peppersass » Mar 12, 2019, 2:29 pm

another_jim wrote:This is what has me scratching my head about what exactly a refractometer is measuring, especially for espresso.

%TDS. That is all. I don't agree that %TDS measurements are inconsistent for a particular coffee, grinder, basket, prep technique, etc. In my experience they're quite consistent, though they might not agree precisely with calibration solutions or drying done under lab conditions. Sure, %TDS isn't necessarily consistent across grinders and baskets, but that's exactly what I'd expect -- different particle distribution, different extraction and so forth. Why should refractometer readings be consistent when those things change?

And like I said, %TDS only tells you about concentration, which is roughly correlated with strength. IMHO, strength plays a lesser role in taste, and strength preferences vary wildly from one person to the next.

We can use %TDS, dose weight and beverage weight to compute %EY. I'm not sure what softness/angularity mean, but I don't agree that %EY computed from scale and refractometer readings don't correlate with acidity/bitterness. In my experience, they most certainly do. However, the measurement is only useful as a relative measure for a particular combination of coffee, grinder, basket, prep, etc., etc. I think you can use it to compare the level of extraction when grinder, basket or prep is changed, but it's not meaningful at all if you change the coffee. And, most important, the level of extraction, and the associated level of sourness/bitterness, don't describe the full gamut of taste.

This is why the current practice of evaluating grinders by %EY seems odd to me. It's simply not the case that the more you extract, the better the taste. It may be true that grinders that average higher %EY might be better for light roasts, but does that mean they're better for medium and dark roasts?

So what does the refractometer measure? Well, if you compare %EY for two different extractions, it'll give you a good idea which one extracted more and which one extracted less, which one is likely to taste more sour and which one is likely to taste more bitter. When you're not a super-taster, or when your tongue is exhausted by tasting many cups, or when you're troubleshooting or evaluating the change of one variable (like the grinder), it can be quite helpful as an adjunct to taste, which is of course the final arbiter.

And again, let's not blame the messenger (i.e., the refractometer.) We have the same lack of correlation with taste if we get the %TDS measurement by drying pucks.

While I normally don't use the refractometer to dial-in, %EY comparative readings can be quite helpful for newbies learning how to dial in a balanced shot. I wish I'd had the refractometer when I was struggling with that, as well as inconsistent equipment. I'd have gotten a much better understanding of the dynamics of extraction, and would have upgraded the grinder much sooner.

another_jim wrote:In other words, we can work the taste much more easily and predictably than we can measure it. So what gives?

You can. Not all of us are able to do that as well. Measurement tools benefit some, but not all.

happycat

Postby happycat » Mar 12, 2019, 4:42 pm

OldNuc wrote:Even if it worked what would be the practical application?


Identify the possibility flavour contribution from the different parts of the grinds distribution.

Given the same EY you could predict flavour based on the distribution. What is the contribution of each.

In Jim's review, we fall back on subjective descriptions of flavour being different, round, angular.

At one point the biggest fuss was conical or flat. Then how big in mm. Then temperature impact. Then ghost or cutting burr. But at some point all the scienctism ends up in the swamp of subjective taste. The Sette punches above its weight. So does the Niche, I get pretty lost.

We're not even using the SCAA flavour wheel (which is tuned to American grocery store items as flavour references?)

As I say, I am clueless so enjoy a teaspoon of salt
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another_jim
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Postby another_jim » Mar 12, 2019, 6:11 pm

happycat wrote:But at some point all the scienctism ends up in the swamp of subjective taste.


No need for a contest between scientism and subjective taste swamps. If you salt your food, it tastes saltier; if you add sugar, it tastes sweeter. So what happens to the taste of coffee when you grind finer? I call it "softer" Call it "finier" if you like; but it's just as consistent as adding salt and things tasting saltier. There's nothing scientistic or subjective about it; it's a repeatable action leads to the same change each time.

Of course, it helps to know what change to look for when doing a particular action. Here's my suggestion for TDS and EY (after playing with the brew ratios of well extracted shots).

Bitter/sours diminish more quickly than sweetness as the concentration of the coffee is lowered. This makes evolutionary sense: our starving ancestors would go for sweet in any concentration, while bitter and sour were toxicity warnings that could be ignored at lower concentrations, but not higher ones. This means a poorly extracted coffee might taste great at low TDS, and be a sink shot at high TDS, while a highly extracted one (with lots of buffers and starchy compounds mellowing the bitters and sours), will be much the same at any TDS level.

See, this idea is really easy to falsify, therefore eminently scientific, yet all about "subjective taste."
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Peppersass
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Postby Peppersass » Mar 13, 2019, 12:29 am

another_jim wrote:Bitter/sours diminish more quickly than sweetness as the concentration of the coffee is lowered.

Hmmm. Could this explain why very light roasts often taste better (less sour) when I pull them Lungo?

But is it because there was more contact time, and greater extraction, or because the concentration is lowered?

Wait! Let me get my refractometer and I'll find out... :D

samuellaw178
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Postby samuellaw178 » Mar 13, 2019, 6:55 am

Thanks everyone for the thoughtful input!

jpender wrote:This is so weird to read. Didn't this conversation take place years ago?


Perhaps we did. :oops: But somehow not all of the discussion points got through to me. From the past conversation, I knew we concluded that EY% doesn't work as a proxy for taste, if the conditions were different. But I had been working under the assumption that if you have the same coffee same extraction flow rate same water etc, there is a high chance the same EY% will taste the same. Apparently not.

On the bright side, it is a good refresher/reminder for us (read: me) who are forgetful. :oops: Plus, there are a couple new interesting points raised by Jim & Dick so it's not all in vain. :lol:


RyanJE wrote:If one were to use grinder that produces a very wide particle distribution and get a 22% ey with 1.4TDS and use a grinder that produces all the same size particle to get the same EY and TDS it would of course taste different, no?

Is it possible that what Samuellaw is really seeing between the two grinders is a result of different particle distributions? Hence the reason the big conicals taste better than his other grinder at the same EY.


I am with you for the first part. No doubt they will taste different.

For the second part, I was working under the assumption that, different particle distribution would contribute to different levels of EY%, at the same extraction parameters (same extraction time, same brew ratio). High uniformity=higher extraction yield and low uniformity=low EY%. That's why EY% may be used to indirectly access how *uniform* the particle distribution is.

By extrapolating that concept, similar EY% = similar particle uniformity, which should in theory taste similar (because we are extracting from the same coffee that has the same set of chemical molecules). At least that was what I thought before this thread.