Welcome to a special episode of Weird Coffee Science,
and it's special because it's got
actual coffee science in it this time.
Now, you might have noticed that the internet
has lost its mind a little bit
over a new paper published in "The Matter Journal".
Now, you might've read it, but more likely,
you've seen one of those ridiculous headlines
where journalists try to just out dramatic each other
for a title.
Anyway, the actual paper is interesting,
and the actual paper is definitely worth reading.
It's titled "Systematically Improving Espresso:
"Insights from Mathematical Modeling and Experiment".
Now, the title does give away
the key things to understand here,
and the first thing is modeling.
So a group of scientists and mathematicians got together
and created a mathematical model
of how espresso extraction should work,
and should is really the key thing here.
Now, the maths involved is comfortably
above my pay grade or comprehension,
but I don't think you need to necessarily
understand the maths,
you just need to trust that the people doing it
understand the maths involved.
Now using this model, they could predict
how something like extraction
would change with grind setting,
or how extraction might change
if you change the constant pressure for the puck,
and that's interesting.
So they have their model of how espresso should work.
Now, the model shows things that are pretty predictable.
If you grind your coffee finer,
you increase the surface area,
and also you make it more difficult
for the water to flow through.
Therefore, for a constant pressure,
you should see an increase in extraction
the finer that you go.
So far, so obvious, right?
Makes total sense,
but then they tested the model in the real world,
and this is where things got interesting.
Instead of seeing a constant increase in extraction
as they went finer and finer and finer,
instead, they saw extraction begin to decrease
as you went finer and finer and finer.
So at very fine grind settings,
they had much lower extractions than they did
at coarser grind settings,
and this was a little unexpected.
Now at this point, I needed a quick kind
of caveat or side note on extraction in general.
What they were able to do,
and what many people can now do
is take a cup of coffee and see how much
of the soluble material from the grounds
ended up in the cup of coffee, right?
And from that, you can calculate a total extraction,
and broadly speaking, extraction is linked to quality,
but extraction is kind of the end result.
It doesn't tell you how you got there.
You would have a scenario, let's say,
where you have very high extraction
of a very small portion of the grounds,
and a very low extraction of a lot of the grounds.
Well, that might have a similar total strength
in the cup of total extraction
as a much more even extraction
that's a little bit lower, right?
So it tells you what you got,
it tells you how much came out,
but it doesn't tell you whether or not
it was evenly extracted or unevenly extracted.
Therefore, it's not a perfect indicator of quality.
So back to the paper.
That drop an extraction seems counter intuitive,
but they did have an explanation.
At very fine grinds, you're inevitably gonna get channeling.
Water cannot pass evenly through that cake of coffee,
and so some water, quite a lot of water,
is going to flow through just a little bit of coffee
where a channel formed.
You'll have a very high flow rate through a channel,
and the coffee around that channel won't see as much water.
It won't be extracted as much,
and this is causing this drop in total extraction.
You've now got two competing factors
in espresso brewing, right?
You've got grind size, which determines,
on the one hand, total surface area,
and the finer you grind,
the more coffee you should be able to extract,
but the coarser you grind,
the more evenly it's likely that the water
will flow through the cake.
And so what you're looking for
is kind of a crossover point,
a point that's the best of both
where you're going as fine as possible
for an even flow rate.
so far, not so shocking.
This just sounds like dialing in espresso,
but it turns out that during the experiment,
this crossover point was producing espresso brew times
of between seven and 15 seconds,
and this is considered an absolute no-no
in the world of espresso brewing.
No one would tell you you can get good espresso
in 15 seconds.
So I read the paper, hopefully like many of you,
And I thought, okay, this sounds interesting,
a little weird.
I should replicate that.
And so I could replicate a reasonable amount
of what was in the paper.
They were using a Mahlkonig EK43 grinder with coffee burrs.
I had one of those lying around at Square Mile.
They were, I think, we're using an Opera espresso machine,
but they weren't doing anything particularly distinct
to that machine's technology.
They were just brewing at six bars, flat profile,
and I had an espresso machine
that I could put to six bars and that was fine.
And the six bars is interesting and notable.
Traditionally, we brew at about nine bars
of pressure at the pump,
and there's a couple of explanations for that.
The first is the kind of myth version of it,
which is that nine bars was considered
to be the kind of average pressure
of an old school lever shot.
Not sure how true that is, but it's a nice story.
The second version is that you tend to see
a peak of flow at around nine bars.
Below nine bars, if you're grinding very fine for espresso,
the flow rate is a little bit lower
because it's just less pressure pushing the water through.
Above nine bars, your flow rate slows again,
because you compress the cake so much
that it's very hard for water to get through.
And nine bars around about is a kind of peak of flow.
In their testing, they had a lot of issues with nine bars,
so they brewed at six bars,
and actually coincidentally, six bars
is what John from Decent Espresso recommends people to use
if they don't have a high end espresso grinder
If you've got a kind of beginner, medium espresso grinder,
then then lower pressures will help
not destroy the cake and create lots of channels.
So I put my machine to six bars, very easily done,
and we kept the brewing ratio initially from the paper,
which was 20 grams of coffee in and 40 grams of coffee out.
Now, I roped Gareth from Square Mile into this
to be my co-conspirator and co-tester in this process,
and we made a whole bunch of espresso,
and we did what the paper suggests to do, right?
You start a relatively fine grind,
and you put 20 in, 40 out, and you time that shot,
and then you go a little bit coarser,
and you do the same thing.
Now, ideally, you're gonna measure the extraction
alongside tasting as you go through this process,
and what you would expect to see, according to the paper,
is that as you go coarser,
your extraction increases a little bit,
and then begins to decrease.
At that peak of extraction is your kind
of finest possible grind setting for even flow.
Now, that grind setting that you find
for peak flow for 20 in, 40 out,
that may not taste good, okay?
Don't worry about that.
What you're supposed to do then is adjust your brew recipe.
Either change your dose or change your output weight,
change your ratios, basically
to get the extraction that you want to reach,
what I believe they call the Tasty Point.
Now, I confess our sample size could have been bigger.
We could have pulled definitely way more shots of espresso,
but it seemed a bit redundant,
because we could clearly replicate
the results of their testing.
We saw a peak of extraction at a kind
of coarser grind setting than expected.
It was like a 15 second shot at that point.
It didn't taste great,
but then we played around with the recipes,
but undeniably, we saw this peak of flow,
peak of extraction kind of thing happen.
In the paper, I think that peak of flow is about 1.7
as a setting on the EK
We were 1.8, 1.85, somewhere there.
I don't think that really matters.
I can't speak to the perfect alignment of our burrs,
our coffee, all of those kinds of questions,
but there was definitely a grind setting
that produced higher extractions despite having a fast flow.
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So we've replicated the results.
This seems to be true.
Is this a big deal?
Is this flawless work?
Do I have any criticisms?
Well, maybe.
So firstly, this is for them, one coffee,
and I've done it with just one coffee.
Now, they would argue that they've done
other work on grind settings.
I think the freezing paper in 2016 was a good example,
and they saw that most of Arabica ground very similarly,
and so they would argue that this protocol
should work for any Arabica coffee,
but that's definitely something worth testing
and having more people experiment with and test.
And secondly, they talk about flow through the cake
as if it's either homogenous and even, or uneven.
And if you use a decent espresso machine
for any amount of time,
you'll see that there's often a point in an espresso
where it transitions from being more even
to less even, right?
It might be that the start of the shot is pretty even,
but once a channel opens, then it stays pretty open,
and your shot deteriorates pretty quickly.
In the Decent, you'll often see on the screen
for a fixed pressure, a reasonably fixed flow rate,
and then a sudden increase in flow.
That seems to be the point at which the kind
of resistance of the cake has given up,
channels have opened, it's falling apart,
It's not providing the same level of resistance,
and the longer you brew, the worse the shot will taste.
With the Decent, you will definitely see
a delay in that uptick of flow
if your grinder is capable of more uniform grind settings,
typically flat burrs do this better than conical burrs,
but it's not an absolute rule.
If your technique is better in terms of prepping the bed,
you will have a more even flow for longer, seemingly.
Now, I did put this point back to one
of the lead authors on the paper, Dr. Chris Hendon,
and he acknowledged that there may be a change in evenness,
but he pushed back and said, just because
you're seeing relatively stable flow,
doesn't necessarily guarantee that that's coming
from a truly even extraction,
truly homogenous flow through the cake,
and that's a fair point, too.
Now, interestingly, the paper does touch
on the real world application of this in cafes.
In fact, they did some testing in a cafe in Portland
that's kind of cool.
So the recommendations of the benefits would be like this.
If you're a cafe doing 20 grams in, 40 grams out
in 28 to 30 seconds,
that's not wildly unusual, that's pretty common,
and there's an opportunity here, in theory.
If you followed their protocols,
you would have, one, much faster shots.
You'd be brewing down at 15 seconds,
literally half the time, which is just wild,
but maybe interesting.
And you would probably be having a lower dose
of ground coffee, let's say 15 or 16 grounds,
but a much higher extraction in that 40 grams of liquid out.
You may end up actually with the same sort
of amount of soluble material in a coffee cup
than you would have done from the 20 to 40.
If you extract 20%, let's say, of 20 grams of coffee,
then you've got four grams of soluble material
in an espresso to dilute it into milk,
into a cappuccino, or a latte, or a flat white, or whatever,
but we got about four grams of that puck
is dissolved in the coffee liquid.
If you took your dose down to say, 16,
but you could get your extraction up to say 25%,
that's a good bit higher, it's very high,
but in theory, you'd have four grams
of soluble material in that cup,
and the taste may well be better
or at least similar, certainly, in milk drinks.
So you've cut your kind of usage dramatically.
You would end up with, and this is where
a lot of people sort of get a bit upset or less interested,
you'd end up with weaker espresso, right?
At 15 in, 40 out, even with a higher yield,
that's going to be a more dilute espresso.
Once you dilute that with milk,
you couldn't tell, that's going to be irrelevant,
but if you're a straight espresso drinker,
you're gonna have shots eight, 9% strength
and many people like thick, gooier espresso
at the 10, 12, or even higher as a percentage of strength.
Now, they do acknowledge the fact
that these very fast flowing shots
that are high extraction maybe lack a little bit
of complexity compared to a more traditional espresso.
They suggest actually blending different styles and ratios,
which they admit is not hugely practical in a cafe,
but might be in more industrial sort of espresso extraction.
It's an interesting idea.
I, in my tasting, the best shots that we had
I thought were perfectly complex.
I thought they tasted quite cleanly
and clearly of the coffees in the blend.
I didn't feel like they were lacking as espresso.
They just didn't have incredible texture,
but the texture was by no means bad.
I think we were getting shots at sort
of 9 1/2 percent strength,
and those were very enjoyable.
That does bring us back to one more thing,
which is that they highlight repeatedly in the paper,
a paper where they are measuring things,
paying a lot of attention to things,
having a very scientific approach,
in all of these things, you need someone,
a barista capable of tasting and tuning a recipe
to produce the most delicious espresso possible.
This is not a recipe for automation.
This is not a recipe to remove the barista from the process.
This is more about setting goals
and targets that are measurable and tying that
into the best tasting espresso that you can get.
Let's summarize this whole thing.
And first things first, if you haven't read the paper,
please go and read the paper.
I'll put a link in the description down below.
You have my permission to skip the section
covering the mathematical equations
around modeling espresso, that's okay,
but actually, the paper itself
is written in very clear English.
I think it's perfectly understandable
to almost anyone who's willing to put
the time in to read it carefully.
I think it's a very well-written paper.
Secondly, this is an experiment.
This is one paper, this is one set of results.
I have my own set of results, but I hope there will be more.
The point of this, I think, is to start
a conversation around this,
around this idea, around this technique,
and I think it will drive us to some interesting places.
One, I think the importance of evenness of flow
will become a bigger and bigger deal.
We don't talk about that enough.
We talk about even puck prep,
but we're at the point where we can start
to measure or pay attention to evenness
in a host of different ways,
and I think that will deeply improve espresso
in a meaningful way.
I think it's a big deal if we can do a better and better job
of even extraction in espresso.
If you're angry about this, if you're frustrated by this,
if you feel that what they're doing
does not apply to what you do, that's okay,
but at least run some tests.
Now, you're gonna need a decent grinder for this.
Ideally, you're going to need something
that is capable of reasonably uniform grind settings.
I think if you're trying to replicate this
with a blade grinder,
you're not gonna have a great time,
and you need to be systematic in this.
You start fine and go a little coarser,
and little coarser, a little coarser, a little coarser,
and sort of see that sort of range
and change in that kind of bell curve of extraction.
I would like to test this on a host of other grinders.
I just replicated what they did.
I want to test it on a Mythos or a Mythos 2,
or on some other espresso grinders that are out there,
like even domestic espresso grinders.
I want to try it with the Niche.
There's a lot of testing to be done,
and this is where you come into it.
Please test this, please try this.
Do some experiments, share your findings.
To finish off properly, I'll share
a few of my own thoughts from the test.
One, I do like stronger tasting espresso.
I really enjoyed the clarity and sweetness of these shots.
I thought they were definitely interesting.
The whole thing was very surprising,
but there is still a case for stronger tasting espresso.
While we saw more uniform flow at six bars
at this coarser grind setting,
looking at a naked pod filter,
we did not achieve perfectly uniform flow.
That cake still fell to pieces at some point,
and maybe it's inevitable that this will happen.
Ideally, there's 20 plus percent less puck
than you started with.
The whole thing is being washed away quite literally.
That's the point of espresso.
And so maybe it's impossible to achieve truly
uniform espresso from start to finish?
Did science just reinvent the espresso?
Maybe, but I think there's something to think about,
and there is definitely something to test
before you dismiss this out of hand.
Try it, it will surprise you, let me know your results.
Let me know your thoughts down in the comments below.
Let me know if you've tried this,
let me know what you think of the taste,
let me know what set up you used.
Share some information with this group, with this community.
We would love to read it, but that's it from me.
So I'm going to say thank you so much for watching,
and I hope you have a great day.