That reminds me of the days when we had to mass out dry ice in analytic chemistry.

another_jim wrote:I of course am very much interested in using a brix meter for its simplicity. I'm just wondering if Terroir is selling water by the river, particularly your and maybe Alan the Aerobie guy's river, given that you were doing brix readings on coffee a while back.

It was difficult to get any sort of overall correlation between dosing and extraction using the baked puck method. Each grinder, basket, machine, and coffee combo produced a different slope for dose, timing, volume etc and extraction. A fast reading brix meter could be invaluable for mapping the prep variables into extraction.

The $30 ebay brix refract is pretty difficult to read. But with a lot of practice, the results aren't bad. You have to be really motivated, though -- many people would probably get frustrated and give up.

Alan uses the $300 Atago digital. It gives an unequivocal digital reading, which inspires confidence, even if it's not accurate! But you'd be crazy to buy the Atago now instead of waiting a little while longer for the more accurate Terroir refractometer.

There's a lot of work to be done here, and it will be difficult. But in the end I think we're going to learn a LOT.

AndyS wrote:I know there are a lot of experienced coffee people who are skeptical of this sort of numerical approach to coffee and espresso. "Screw the numbers," they snort. "I go by my taste buds."

Obviously, the numbers can't possibly replace taste buds. They can only augment them, aid in quality control, and help in the diagnosis of problems. But I do know this: I have had many mediocre coffees at shops run by these snorting, experienced skeptics. And once their "golden taste buds" walk out of the shop, employees with less developed taste buds are left in charge. The results aren't always so golden. With the proper use of objective measurements, quality control at these shops could be greatly enhanced.

I'm in full-agreement with everyone that this sort of tool can be super-useful.

My main concern with people employing quantitative analyses on espresso extractions (and often with brewed coffee) is that measuring a quantity of solubles is a far cry from measuring the quality of those solubles. In other words, nailing a 20.0% extraction only tells you how much was squeezed out of the coffee grounds. It doesn't tell you whether those solubles were the (predominantly) kind that you want, vs. the kind you don't want. In most quantitatively-measured situations, you can have a severely unbalanced extraction and still nail the numbers.

Just trying to further the discussion. What says you, Schecter? Just how augmented ARE your tastebuds?

AndyS wrote:I'm using a .01g scale. I believe Terroir does work at .001g or .0001g.

One has to work quickly. Even with the .01g scale, a hot cup of espresso scrolls through the numbers losing weight through evaporation!

What if you put on a tared cover at shot completion?

Nick wrote:measuring a quantity of solubles is a far cry from measuring the quality of those solubles. In other words, nailing a 20.0% extraction only tells you how much was squeezed out of the coffee grounds. It doesn't tell you whether those solubles were the (predominantly) kind that you want, vs. the kind you don't want. In most quantitatively-measured situations, you can have a severely unbalanced extraction and still nail the numbers.

I'm not sure that any of that is really true, Nick. The way extractions often seem to work is that the sour flavors come out early, then sweeter flavors, and then eventually bitter flavors. That's not an ironclad rule, but it seems to be a general tendency having to do with the relative solubility of the various components.

So if you don't get a high enough extraction numerically, you're probably getting a cup that's pretty sour. If you hit it right, you're getting a nice balance of sweet and sour. And if you run too far, you get dilution and a tendency towards bitterness.

If one worked at it deliberately (channeled puck, temperature way off, grind uneven, etc.), it would undoubtedly be possible to produce a bad tasting cup that measured "right." But using good technique and reasonable brew parameters, I think a fairly narrow band of extraction percentage really does correlate with flavors that most people consider nicely balanced.

cafeIKE wrote:What if you put on a tared cover at shot completion?

I'm doing that but the cover has to come off to remove samples for refractometer measurements and of course, to taste!

AndyS wrote:I'm not sure that any of that is really true, Nick.

AndyS wrote:If one worked at it deliberately (channeled puck, temperature way off, grind uneven, etc.), it would undoubtedly be possible to produce a bad tasting cup that measured "right."

A little contradiction, no?

Deliberate or not, that's sort of my point. Question is, what are the relevant thresholds? Just how "bad" can that "measured-right-cup" taste?

I'm just hypothesizing though. One of these days, I'll plunk down for the system and play with it myself.

Nick wrote: In most quantitatively-measured situations, you can have a severely unbalanced extraction and still nail the numbers.
...Just how "bad" can that "measured-right-cup" taste?

Instead of trying to dream up weird theoretical situations where the measurements fail, you need to get some actual experience with this system and note how it succeeds. IMHO.

Nick wrote:Question is, what are the relevant thresholds? Just how "bad" can that "measured-right-cup" taste?

At least as far as drip coffee goes, you could talk to Carl Staub, since he used to play with these ideas a few years ago. He'd take a batch of underextracted coffee and mix it with a batch of overextracted coffee to come up with "correct" coffee that tasted bad.

As for espresso, I think you could taste the results in a mildly channeled shot, where part is overextracted and part underextracted.

AndyS wrote:Instead of trying to dream up weird theoretical situations where the measurements fail, you need to get some actual experience with this system and note how it succeeds. IMHO.

I don't think talking about uneven extraction and its impact on a measurement system really qualifies as "weird theoretical situations". The question that I think Nick is getting to is "how does the system hold up in the real world?" instead of how it has performed under controlled testing. If Barista Jane pulls a 25-second 30ml shot which has suffered transient channeling, how will that compare in measurement to a 25-second 30ml shot which doesn't channel, recognizing that there will probably be subtle changes in dose, tamp, and/or grind between shots?