luca wrote:Great point, Andy. For all of the mucking around that I'm sure that everyone has done, I can't remember any blind tasting experiments off the top of my head. Doubtless this is because we're all usually too busy adjusting the temperature to make the shot taste better!
I might be able to get some people, machines and coffee together at some stage. If I, or anyone else, could, what do you think that it would actually take to make a blind tasting experiment legitimate? Obviously there's only so much tasting that is practically going to happen ...
As one of the only two people I know of (myself and Jim Schulman) who has actually pulled off simultaneous paired blind tasting espresso experiments such as this, I can tell you that the effort involved would be considerable. I'll try to summarize:
(1) First you would have to decide what magnitude of temperature variation it is that you want to test. At the current state of equipment, I think it would be overly optimistic to try to get the shot temperatures being tested closer than 1 degree F. apart. Even that would be a challenge to pull off, and you would want some real-time validation that you were actually accomplishing this on a shot by shot basis. The result would be to add one more variable that could cause you to pitch the two shots produced, in addition to the likely occurrence of shot pairs with one substandard shot in them, requiring the tossing of both shots and repeating.
(2) There are very many different sorts of shot profiles produced by different types of equipment, everything from a typical humped heat exchanger profile varying several degrees F over the time duration of the shot, vs. something ultra flat, and everything in between. Although some in the marquee cafe crowd might like to assume that drinkable espresso only comes out of an LM or Synesso, others (including myself) would beg to differ. Can you extrapolate findings from a flat profiled Synesso to a Cimbali or E61 HX machine? I don't think so.
(3) What kind of coffee are you going to use and at what shot temperatures? If you picked something regarded as finicky, like one of Schomer's MM containing blends, would the findings with this coffee at 203F (or thereabouts) mean anything whatsoever to the sorts of coffees most people seem to prefer? My reading of various posts on this website and others leads me to believe that most people seem to prefer most coffees between maybe 198F and 200F. I think this would obligate you to test at least 2 or 3 different coffees or blends, and with more than one set of temperature differences for each coffee. I'm not as concerned as Dave with the issue of the coffee aging and having multiple tasters; I think you could balance for that in the study design, but you would want to conduct the tastings over a period of 2-4 days, maximum (for a given coffee), incorporating the time when the coffees could be anticipated to be at peak, after roasting.
(4) The mechanics of doing such a study would require two identical espresso machines and grinders, with experienced operator(s) and hopefully, tasters. Having done this sort of thing a number of times now, I can tell you it would be overly optimistic to expect to get more than 8 paired shot comparisons per taster per day. You would need to get at least 5 or 6 comparisons of each condition (coffee and temperature) to have much chance of statistically meaningful results. You'd have to plan it all out, but I'd guess you'd need a minimum of 6 tasters for 3-4 days. This is assuming that you would be testing each of 3 coffees at each of 2 or 3 different temperature variations. Each day's tasting session would last 2 or more likely 3 hours, after you had gotten the machines and grinders all set up and ready to go.
(5) what I am describing would really just be a comparison of two identical machines, and given the differences in shot temperature profiles, the conclusions you could reach would be very narrow and hard to extrapolate to other machines with much different shot temperature curve shapes.
This sort of study is a huge PITA to actually execute. To say it is not fun is to underestimate the aggravation involved for both those who pull the shots and those who taste them. I would not volunteer to be in a study like this, that much is for sure.