another_jim wrote:Since you announced this, I've been trying to think of ways that would allow one to characterize more precisely how pressure variations affect taste and mouthfeel. After a lot of thought, I think the best route might be to find a coffee or roast that is undrinkable when done with a straight profile, and tasty when done with the pressure profile you like. If you can find one like that, it would be fairly clear how the profile affected the taste.
Jim and I both have some prior experience in doing research in our earlier lives, and frequently discuss innovations and research attempts we see written about here and in other online venues. We are, in fact, planning to do an article sometime soon on the entire topic of performing coffee research at the enthusiast or small entrepreneur level.
A large corporation, like for example a drug company, can afford to hire legions of lower level researchers to do "basic science" research where interesting ideas are played with, without any specific goal, with the hope that they might stumble upon something. Even so, when a company like for example, Pfizer, has problems and they "reorganize," laying off thousands, who do you think are among the first people to be let go? Let me guess . . . . .
As individuals without unlimited time or resources, we are forced to be VERY focused in our work, or, our work will likely come to nothing.
If you look at the stuff that Jim and I have written up over the last few years, the "success" that it has achieved has been due primarily to choosing relatively small questions that can be answered in straightforward ways. I'd of course like to think that we are genuises and that this has allowed us to study rotary pumps and vibe pumps and preinfusion and freezing -- but the truth is that we asked simple questions and studied them in very simple ways. For example, if you take the freezing study, it was designed to prove or disprove the notion that freezing ruins coffee and or does not preserve it. Testing that is a very straightforward proposition, as opposed to testing what impact altering all aspects of the extraction pressure curve might do.
If you take temperature stability, another topic that has been debated A LOT, it has now been achieved to one degree or another on a number of different machines, either factory (Aurelia; maybe GS3) or with mods (Greg's modified Linea, my Juniors), yet no one has tested in a convincing way what impact the shape of the temperature profile has on espresso shot taste, or whether the whole exercise has much merit beyond knowing one has less variable brew temperatures.
As to pressure, I would submit that what you are trying to test, Greg, is an order of magnitude, maybe two, more complex, and it suffers from the problems in tasting temperature cure importance, in addition. As a result, unless your work becomes VERY focused, I think it is going to be very hard for you to conclude much of anything.
Adjusting and calibrating things like temperature and pressure are interesting, and they should be important, however they are coming at espresso making much in the way that basic science drug research comes at solving medical problems. You don't have enough time, enough lives, enough other people to do this stuff with, enough physical and monetary resources, to do enough testing with the variables you are presenting yourself with to have much hope of getting anywhere other than to say, "I changed this and that and the other thing and so and so was over and we both thought the shots were better." I hope I am wrong, but I don't see that sort of work going very far.
My suggestion would be to start with some very specific issue in espresso extraction, a problem, something you think can be fixed with one significant change in pressure profiling, then test that. I think this latter approach has the chance of bearing some fruit.
Good luck.
ken