Thanks for the praise.

However, my take is that the predominant opinion so far is that it's a useful tool for doing light SOs; but for normal espresso, the ding on body is too much.

Of course, I haven't begun to design and roast espresso blends for this technique yet

appa wrote:Is the distribution of solubles different in regular coffee different than in espresso (more or less heavy compounds,etc). I was under the impression that the solubles yield for espresso would be much higher cos the high pressure, etc.

The conventional wisdom before I did this paper was that a properly drawn espresso shot would be around 20% solubles yield. This was especially true if the shot was stopped at the proper point, when the color blonded. I believed this and stated it in my article on espresso on this site. I, and the conventional wisdom, were wrong. "Underextracted" and "overextracted" are judgement terms. When Abe was visiting me, he consistently preferred shots dosed around 1/2 to 1 gram higher than my favorite level, with extraction levels roughly 2% percent less. This was of very light (ultra-North Italian) roasts. Abe enjoyed the extra aromatics and flavor, while I preferred a little extra caramel. We both agreed how the taste change, but didn't agree on where the best balance was to be found.

2) How important is coffee freshness now considering the italian model of espresso making you mention in the conclusion?

I don't care how stale coffee extracts -- all the results I've quoted for my experiments and for brewing coffee are using very fresh coffee. The results given in academic papers on espresso do not mention how old the coffee was, or how it was preserved.

My intent in the conclusion was that the Italians, like almost all people, are not fussy about fresh coffee, so they could use dosers to precisely dose any weight of coffee they wanted. For people who are fussy about fresh coffee, dosing different weights does present a problem. Solving this problem by using 18 instead of 14 gram doses had the consequence, I think somewhat pernicious, of lowering the solubles extraction.

Thanks for pointing this ambiguity out. If an intelligent reader who has the courtesy to read something all the way through, misreads a point, the fault lies with the author's writing. I'll rewrite to make it clearer.

One of the things people got which wasn't in the article was that headspace is a good thing on most machines. This is not about the depth of the puck per se, but how much room is left over it. There's two effects.
-- On many machines, the puck touching the shower screen degrades the taste, so these machines have a minimum headspace, or a maximum dose for each basket, depending on its depth.
-- More headroom makes for longer dwell times (it takes longer for that space to fill up, and the puck can swell more). Longer dwell times generally allow wider latitude on leveling and tamping.

In terms of the paper's thesis, that solubles yield, controlled by varying the dose weight to filter area ratio, systematically changes the taste, this is a confounding variable. I'd need variable height baskets each with the same hole area to get around it.