Well established among contemporary espresso enthusiasts. An actionable version of the published research is at https://strivefortone.com/2020/09/19/lo ... -espresso/

The journal article can be found at https://www.cell.com/matter/pdfExtended ... 19)30410-2

Outgrowth of work using DE1 is discussed at https://pocketsciencecoffee.com/2022/05 ... actamundo/

In short, if you are willing to abandon traditional shot parameters, there's a lot of extraction space that can produce arguably better espresso with lower variance. This is especially valuable with coffees that are more challenging to extract well.

Manny are also finding that lower temperatures as well as declining temperature profiles during the shot can improve the flavor of the espresso produced.

HBchris wrote:Or if you guys have any thoughts on this.

Meh. Chasing extraction yields without a real input for taste, especially when taste preference is very subjective, is something I'm not interested in at all.

When extraction yields vary by less than 10% and people tey to portray it as a huge difference maker, it is hard for me to believe.

And as far as temperature, I would say that it is highly dependent on coffee too.

One coffee I tried tasted less bitter and dry when brewed at a lower temperature. Not sure how the extraction yield was, but considering it was a medium dark roasted coffee, it would make sense that a lower EY would taste better here.

Jeff wrote:Manny are also finding that lower temperatures as well as declining temperature profiles during the shot can improve the flavor of the espresso produced.

Jeff, does this specify a roast level by chance? It would make sense to me that a darker roasted coffee would benefit from this. Lower temp, less extraction, better taste for that.

For light coffees it might work opposite of it.

I have zero evidence to go by. Just a reasoning thought for me.

It's been really surprising for those of us who have been playing around with this for several years. The DE1 has some advantages for exploration as it is temperature agile both between shots and to some extent during shots. One of the things that is surprising is that the DE1's "normal" temperature setting for a conventional profile is lower than you would expect. Rather than 201° F or 94° C, it is probably closer to 89° C. Even taking that into account, temperatures in the mid or low 80s seem to be able to produce well extracted, better tasting shots from medium light and lighter coffees than more traditional temperatures.

Taking this a step further, setting the machine up for the 3 to 6° C temperature drop it could achieve during a shot also seemed to often improve the in-cup result.

Initially, this surprised a lot of us! There was quite a bit of talk about it several years ago among the more adventurous. There's some thought that the high temperatures may not be needed due to what we are now calling high-extraction burr sets, as well as intentional pressure/flow profiling both during the soak phase and extraction.

Jeff wrote:Taking this a step further, setting the machine up for the 3 to 6° C temperature drop it could achieve during a shot also seemed to often improve the in-cup result.

Can you elaborate on this please? Curious what you guys discovered. Was the cup just better balanced? Less bitter/sour? Less astringency?

To tie this back to the original post, if generally people think of astringency when tasting espresso and this is allegedly caused by over extraction, wouldn't a higher extraction yield more astringency therefor making a worse result in the cup?

Smoother, better balanced, still with clarity and crispness

It is really hard to "overextract" a good medium or lighter roast. Certain burr sets can take a light-roast coffee into astringency very close to where you are able to get a balanced cup, If you're lucky with one of those grinders, it is just after you can get balance, not just before. If you've got a balanced cup with a good, medium-light or light roast coffee, even with one of those grinders, you can extend the ratio and you usually just get watered-down espresso rather than a significant shift in flavor (including astringency as a tactile part of flavor).

Measuring EY, for me, is a big help in tuning technique (either reducing shot-to-shot variance or the indication that a lower EY is often associated with uneven extraction), or seeing if there is a measurable difference between two setups. Maximizing EY doesn't always maximize the quality of the espresso. Some light-roast coffees taste better if not pushed quite as hard, especially with some of the "high-extraction" burr sets like the 64 MP or 98 HU. For my tastes, I would not want to push the extraction of an espresso blend too hard as it tends to bring out flavors that I don't enjoy. Others might push it harder as those flavors can be the ones that "cut through milk" and make for an enjoyable drink.

For me, which is perhaps different than what a Q Grader might say, I'm looking for balance at two levels. The first is that the subtle flavors are present and harmonious. My preference, if the coffee supports it, would be extracting a (now mythical) Ethiopian that was perceived as sweet with a moderate blueberry note and an accent of bergamot over an in-your-face "blueberry bomb". The second part is how does the overall experience come together. Is there a smooth transition from the first sip through the finish?