The Guardian: Maths experts zero in on secret to perfect espresso
theguardian.com/food/2020/jan/22/maths-expert...Posted Jan 22, 2020, 4:15 PM UTC
1118
theguardian.com
Here's the journal article in question for those that are curious (open access): https://www.cell.com/matter/fulltext/S2590-2385(19)30410-2
5
My experience with the is that combination of more coffee, less water, coarser grind works well. I'm usually about 15 grams coffee and just under an oz. of water. I don't get too excited if the extraction is faster. If it's only 10 seconds and tastes good, fine with me.
I prefer that it cling to the side of the cup though. Then I know it's not too weak.
3
This article was the actual experiment if i'm not mistaken: Matter
3
I’m just a layperson, but interested in what you industry folks think of this: "If you use 15 grams instead of 20 grams of coffee and grind your beans coarser, you end up with a shot that runs really fast but tastes great. Instead of taking 25 seconds, it could run in 7 to 14 seconds. But you end up extracting more positive flavors from the beans, so the strength of the cup is not dramatically reduced. Bitter, off-tasting flavors never have a chance to make their way into the cup." Would it bother you to pull a 10 sec. shot?
2
To be honest, it's been a long time since I've used more than 15g espresso doses as it's been common knowledge in specialty coffee circles that lower doses and pressures give higher extraction yields for many years (we run 5-5.5 bars).
However, I have done a lot of experimenting with coarser grinds/fast shots and finer grinds/slower shots. I typically start with around a 1:3 brew ratio because I prefer filter roasts made as espresso and they need a bit more water to make the EY high enough.
The coarse/fast shots have great flavor clarity and really highlight the acidity of the coffee. There is some good sweetness. This was at 5-5.5 bars, but typically with quite short pre-infusion (5 seconds or so).
The fine/slow shots are terrible unless very long/gentle pre-infusion is used, followed by the low pump pressure. The long pre-infusion helps prevent the partial clogging that the paper talks about. I much prefer the sweetness of the fine/slow shots. I also feel like they have more body even though TDS can be very similar. It's also worth noting that I can hit much higher EYs with the fine/slow shots.
Maybe I'm out of the loop but I don't really understand why they started with this assumption that everyone is grinding too fine already. Really, the whole thing boils down to the same stuff it always does: grind finer until you get astringency (and maybe bitterness depending on roast level), then back off a little. That is basically always optimal.
There was some discussion of the fact that 22% EY on one side of the peak tastes better than 22% on the other side, but not a whole lot. For sure it is better to be on the coarser side of the peak so you don't have the partial clogging which is what gives those sour and astringent flavors at the same time. So I guess that is why they kind of summarize by pushing grinding coarser, but if you care about flavor, you should do super long pre-infusion and super low pressure shots with super fine grinds (as fine as possible without the clogging). The only downside is that the shots take forever - it actually makes me want like a 4 group machine. Gives you a little more time to chit-chat with a customer, which is what makes most of them come back anyway.
All that said, it's nice to see some legit science match up with experiment in the coffee world. It's been a little while since I've done PDE's but they made it reasonably easy to follow for those that have learned something about them.
3
Maybe I'm out of the loop but I don't really understand why they started with this assumption that everyone is grinding too fine already.
It's coffee-people cultural bullshit + outside world press. I love Hendon, but those portions are 100% the coffee wonks involved.
Coffee people really love to take down other coffee people; and "everyone except me is doing it wrong" is how the majority of progress in our field has been presented for the last ten years or so. By way of example, look at how the overwhelming bulk of Rao's recent work has been prefaced with "everyone else sucks at coffee, let me explain why my method doesn't..."
While the outside world finds us, our ways, and our practices both alien and irritating, so they love opportunities to point out that 'coffee people don't know as much as they think they do.'
The two combined within the press coverage of the science itself to this rather insufferably smug lede that's been on repeat throughout the press.
The only major exception to that norm is Australia, where they are instead doing Peak Australia Things and stressing the contributions of Australians to the science (you'd easily get the impression that the entire study and its research team were wholly Australian), the superiority of Australian coffee compared to the rest of the world, and how great it is that Australians are providing leadership to the rest of the coffee world. Which is, honestly, pretty much expected par for anything where Australians talk about Australian coffee.
2
This was the first submission of this topic - to prevent clutter, we'll remove duplicates.
Here are some other versions -
ArsTechnica, Phys.org, actual study: Cell, Eurekalert, Telegraph, Vice, Today.
As ever, science journalism likes hyperbole. "Perfect" has been thrown around a lot regarding this study, where the authors and actual impacts are much more modest "we learned a little more about how espresso works" and in ways that both confirm and challenge conventional wisdoms around espresso.
The science here is super cool, but not terribly surprising - like most good science. Less coffee generally makes for a more predictable, more nuanced, and more approachable coffee; for all that there's a load of other reasons to use more coffee in a shot - repeatability and ease, for instance, being huge ones. A bigger puck might be more vulnerable to problems, but is also less demanding as far as even distribution and tamp.
1
[deleted]
1
Whoops, I submitted an ars link and saw this shortly after. Do remove mine!
1
This is an interesting article. I wish they had given some information about the exact grind they used. Was that coffee shop just using extremely fine grinds?
1
Check out the actual study: https://www.cell.com/matter/fulltext/S2590-2385(19)30410-2
2
That was interesting, but I couldn't find the actual grind size in there.
1
Not sure what you mean by actual grind size. There isn't a uniform measurement of grind size.
They do list the extraction time as a function of ek43 settings in figure 3 and 4.
Then nearly every other set of data uses the same ek43 settings. Figure 7 is probably the most interesting graph as it talks about subjective flavour to ek43 setting to reproducibility which is probably what you are after.
They also have a whole section on distribution of particle size if you want to get even further (and if you happen to have some spare sieve analysis machines on your bench :D)
3
I'm curious - any shops planning on trying this out?
1
Despite the tone of the various press around it - there are lots of shops who were already doing very similar things prior to this article. Hendon's core finding of "fine until it chokes, then back off" is SOP for dialling in almost everywhere, as of maybe four or five years ago; the lower pressure of six bars has had adoption and abandonment repeated on and off since variable-pressure machines hit the market ten or fifteen years ago; and things like Perger's coffee shot as well as various variations on actual espresso with coarser/lower dose have seen intermittent vogue in competitions and cafe dial for easily that long or longer.
And the fact that anyone who now speaks up about doing it is going to get somewhat labelled as "doing that study" rather than doing their own thing, already, is probably not going to be an asset to adoption.
The study formally and methodologically confirms a bunch of things that a solid chunk of the industry was already doing, or aware of, as "good" and puts some scientific method towards repeatability and shot consistency - but is very little new material. The biggest genuinely new thing is the amount of inconsistent extraction their model predicts within a 'conventional' shot.
2
Any mention of what they determined as the optimal particle size? It's all well and good to say "you're grinding too fine because physics", but how about practical numbers to try and aim for? Could a really good grinder + sieving out dust allow you to use fine grinds without the blockages they theorise?
Also, the bit about using less coffee might be more interesting than it sounds. We know there's a tendency to underextract in fancy coffee circles, and it could also be the case that pulling a smaller shot with a shallow grounds-bed allows for more even extraction than a large or double shot at the same ratio.
0
I think the point was not the best possible espresso, but rather the most reproducible decent espresso. My understanding of the article was basically "You are more likely to mess up when you do a fine grind with more coffee than a coarse grind with less coffee." So basically, the espresso equivalent of an ISO-compliant cup of tea
I think you're misinterpreting it. It was about consistency, but also quality. The two go hand in hand with almost a 1 to 1 correlation: a recipe that makes a great shot 1/10 times is making a pretty mediocre shot.
But also, the study mapped out a variety of variables to hone in on your preference, and achieve it consistently. The "less coffee, less water, shorter pull" was for a consistent highly regarded shot, but it had suggestions for tweaking around specific variables. The take away there is largely that brew time seems to make almost no difference.
Dammit. Now I want my own cup of ISO-3103 tea, if only to serve to my engineer siblings.