Do ultra precise brew temperatures really matter? - Page 3

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RapidCoffee
Team HB

#21: Post by RapidCoffee »

Much more interesting (at least to me) is the related question: is a flat temperature profile more desirable than the humped temperature profile produced by many HX machines? I'm sure that brew temperature differences can be tasted in the cup. But do you get a better extraction when the temperature is varied slightly during the shot?

Unfortunately a much more complicated hypothesis to test...
John

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hbuchtel

#22: Post by hbuchtel »

With regards to Chris (Malachi) 's quote about the GS3, there are two different questions, right? One is whether Chris or people in general are able to distinguish such small temp differences, and the other question is how well the little glowing number represents the temp of the water hitting the puck...

It doesn't seem unreasonable for a person to be able to distinguish between slightly different temps, especially when using a blend one is familiar with. In a familiar situation we can detect quite small changes... what is missing, what is new, etc.

I would love to see a long-term blind taste testing... a year or so of a couple blind shots a day would do it ;)

Henry
LMWDP #53

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AndyS (original poster)

#23: Post by AndyS (original poster) »

HB wrote:That is my exactly my point: Unless it can be demonstrated in a blind taste test, such statements should be treated with skepticism on the basis of a "thought experiment" alone.
OK, we surely agree. I'd just add what I said previously: almost all the interesting and surprising stuff has been the result of real experiments. The so-called thought experiments normally add nothing more than a lot of boring, obvious commentary.
-AndyS
VST refractometer/filter basket beta tester, no financial interest in the company

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luca
Team HB

#24: Post by luca »

Hey kids,

As you say Ken, these things are all a massive PITA. I have done a bunch of cuppings, blend testings, etc, but I haven't ever tried to make anything statistically significant. In that regard, I have a lot of respect for Jim and yourself.

There is a very small chance that my local LM distributor might be able to help us out on this one. I haven't asked yet, but they usually have a few machines sitting around and a swift and they're usually quite accomodating. The swift doesn't quite get the same sweetness into a shot that you would get from a Robur, but it does get you consistent shots quickly. I figure that if I could borrow a swift and something like an FB80 and a GS3 or whatever they have around, then get a few volunteers, I might be able to organise some sort of a test. Obviously it would be a very narrow test, but at least it would be something.

Thoughts?

Cheers,

Luca
LMWDP #034 | 2011: Q Grader Exam, Brewer's Cup #3, Australian Cup Tasting #1

DavidMLewis
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#25: Post by DavidMLewis »

When we're talking about something like temperature, even without getting into temporal variations during a shot or spatial variations within the puck, three things are important to distinguish: precision, accuracy, and repeatability. The first, precision, refers to how fine or coarse are the available measurements or settings. These may be different: my scale has grams on it to two digits after the decimal point, so it can display 0.01 g increments. It only does in fact display in 0.05 g increments, though, so that's its precision. Accuracy refers to how closely those measurements correlate with a standard, and in this case that's where the "current crop of probes and digital thermometers" fall down a bit. The third, which I contend is more important to the discussion, is repeatability: how closely can I get, with a given setting and ritual, to the same temperature every time? On my machine, for instance, I have no particular reason to believe that its output temperature is what Reneka tells me it is. But the probes are fast-responding RTDs, which drift slowly in their response to a given temperature. The circuitry is set by 1% metal-film resistors, which also drift slowly. And the ritual is fairly consistent because like many on this site I've learned to make OCD work for me as a vital component of my lifestyle. So if I change the temperature by what Reneka claims is 1° C, the precision, I figure it's changed by something fairly close to 1° C, even though I don't have any idea what it changed from or to (the accuracy). And when that change produces a far-from-subtle taste difference, over many SO coffees and many years, and when that taste changes less between shots than between temperature changes (the repeatability), then I conclude that I can taste a difference due to a 1° C, or so, temperature variation. Of course I can always be fooling myself, but I'd be happy to repeat the test for any H-B participant who cares to stop by my house, and over time come closer to a consensus. Note that I'm not saying anything here about the original question, which was at what point, for most people, these difference cease to become apparent or fall below the available repeatability in other aspects of pulling the shot.

Best,
David

Ken Fox

#26: Post by Ken Fox »

DavidMLewis wrote:
. . . . I conclude that I can taste a difference due to a 1° C, or so, temperature variation. Of course I can always be fooling myself, but I'd be happy to repeat the test for any H-B participant who cares to stop by my house, and over time come closer to a consensus. Note that I'm not saying anything here about the original question, which was at what point, for most people, these difference cease to become apparent or fall below the available repeatability in other aspects of pulling the shot.

Best,
David
A resolution of 1 degree Celsius is almost 2 degrees F.

Any of us who have equipment whose brew temperature we know how to adjust, has certainly had the experience of how some coffees taste differently with temperature adjustments. I myself have played around with this in the last couple of days with a particular coffee I roasted that I'm not very fond of, by changing the brew temp from about 198 to about 201F (it tasted differently, but I still didn't like it). So, I'm not doubting the thesis that brew temperature changes induce taste changes. What I'm doubting is the reliability and repeatability of this with SMALL changes, both as regards equipment limitations and the limitations of human tasting apparatus.

2 degrees F is probably a range that many or even most espresso tasters could detect, and certainly at least some of the current crop of equipment can deliver repeatable shots with that degree of temperature difference.

What I don't know is whether current equipment can reliably produce shots at repeatable temperature differences of 1 degree F. That would absolutely need to be established before any tasting studies could go forward. Assuming the equipment can do this, then one could test the potential of some tasters to detect this difference. Any brew temperature difference below 1 degree F probably cannot be accomplished with current equipment on a repeatable basis, and you'd have to count me as a doubter on that until I am proven wrong (which I'll acknowledge when I am).

ken
What, me worry?

Alfred E. Neuman, 1955

Ken Fox

#27: Post by Ken Fox »

luca wrote:Hey kids,

As you say Ken, these things are all a massive PITA. I have done a bunch of cuppings, blend testings, etc, but I haven't ever tried to make anything statistically significant. In that regard, I have a lot of respect for Jim and yourself.

There is a very small chance that my local LM distributor might be able to help us out on this one. I haven't asked yet, but they usually have a few machines sitting around and a swift and they're usually quite accomodating. The swift doesn't quite get the same sweetness into a shot that you would get from a Robur, but it does get you consistent shots quickly. I figure that if I could borrow a swift and something like an FB80 and a GS3 or whatever they have around, then get a few volunteers, I might be able to organise some sort of a test. Obviously it would be a very narrow test, but at least it would be something.

Thoughts?

Cheers,

Luca
Hi Luca,

I don't want to repeat what I typed in my response to David Lewis, so please read that response in addition to this one.

I welcome your willingness to look at this, which as you state, will not be an enjoyable experience. Before doing anything, however, I think we need to try to avoid the possibility of doing a study that gives an apparent but false result, which could happen if, say, shot curves overlap even though numerical readouts suggest high precision.

As a very first effort I would take a Scace device with a good digital datalogger and plot out, say, 25 shot curves taken at one intended temperature, then do another 25 at a temperature which you think will not produce curves overlapping with the first set. One would have to know to what degree the shot temperature curves are in fact distinct and not overlapping. My guess is that you would have to get the intended shot temp curves close to one degree C apart in order to have separation. If this is true, the hypothesis would not be worth testing because most of us would probably accept that many tasters could detect that degree of temperature difference, and you would just be "proving the obvious."

I have recently posted this set of shot curves from my old vibe Cimbali Junior:



While I did not do 25 shots at each temperature, I was just trying to establish what the degree of imprecision is, not the ability of the equipment to produce very fine temperature distinctions, which it is obvious that it CANNOT. What I can say on the basis of THIS graph is that, as I am using it, the machine can produce shots within about 1 degree F of either side of the temperature I would like to have, e.g. the shots occur within a "band" of about 1 degree C. This degree of precision is not adequate to test the hypothesis that we are discussing, e.g. the ability to produce and detect differences in shots at small incremental temperature differences.

If you can get reliable separation of the curves, without overlap of the temperatures, on the order of (say) 0.5 degree C, then the hypothesis would be worth testing and the results would be interesting.

Good luck!

ken
What, me worry?

Alfred E. Neuman, 1955

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Tristan

#28: Post by Tristan »

This is an interesting thread. This discussion makes me think of a quote from an Italian humanist who lived in the 14th century named Petrarch. He said, "It's better to will the good than to know the truth." I'm not sure the truth will inspire us to make better coffee drinks.

I think sometimes dwelling too much on science can interfere with the enjoyment of the coffee. I think this is especially true if you don't have a pro-sumer set up (like me!). Still a noobie here :D , so I'm trying to stay as consistent as possible with my routine! Ignorance might be bliss!

This being said I would still be interested in the outcome of such a blind tasting study to determine if precise temperatures really make a significant impact on the final product. Maybe this will further the merit of higher end machines or possibly validate the use of PIDs?

Ken Fox

#29: Post by Ken Fox »

Tristan wrote:This is an interesting thread.

I would still be interested in the outcome of such a blind tasting study to determine if precise temperatures really make a significant impact on the final product. Maybe this will further the merit of higher end machines or possibly validate the use of PIDs?
I don't think there is any remaining need to "validate" the use of PIDs. If you take the most basic example, for example the use of them in a machine like a Silvia, they merely compensate for a very poor stock method of boiler temperature control on that machine, something that most would find simply unacceptable. The thermostat that comes with that machine is so poor that people have to "temperature surf" just in order to get a drinkable shot.

As to the use in more expensive machines, in lieu of a pressurestat, PIDs have obvious value that extends beyond the ability to make a "better" shot. Having PID'd my two single group Cimbali machines, I don't think I have ever claimed that having done so produces "better" shots. What I have said, and what has been said by others, is that with a PID one can better control the temperature of what is being controlled (the boiler in my machines) by eliminating the hysteresis of a pressurestat. One can also change temperatures easily, on the fly, something one cannot do with a pressurestat. Finally, pressurestats don't tend to last very long, with the typical Maters and CEMEs lasting at most 2 years. A PID installation should last a much longer time, another fairly obvious benefit.

ken
What, me worry?

Alfred E. Neuman, 1955

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Tristan

#30: Post by Tristan »

Ken Fox wrote:I don't think there is any remaining need to "validate" the use of PIDs.
Apologies, I should chosen my words more carefully. My overall "newbie-dumb" haunts me :lol:

You've sold me on the merit of PIDs! I didn't realize they had so many other benefits!