Today we're gonna talk about crema, that beautiful red-brown
foam that sits on top of any well-made espresso. We're gonna talk about
what it is, why it exists. Is it good, is it bad? Should you skim it off? Should you leave it on? All of this and more we shall
answer in today's video. So let's start with the name, because the name is
initially kind of confusing. Crema comes from the Italian for cream, but this is a foam, this isn't cream. Why did it get its name? It goes back to 1948 to 1950. Achille Gaggia has got
this new espresso machine. It's brewing at much,
much, much higher pressures than anyone has brewed with before and the espresso coming out of his machine has this weird foam on top. And initially people are like, "What's wrong with the scummy
foam on top of your coffee?" And he turns a negative into a positive. He starts to advertise his machines as having crema cafe naturally naturale. Natural cream coffee or natural
coffee cream, I don't know. This is a wonderful stroke of
branding genius in my eyes. He names one of the great
things about espresso and further cements his reputation or place in history as
a father of espresso. So the name sticks. At no point, do we really ever argue it and at some point that Italian
word becomes an English word to represent the foam on an espresso. So why does it happen? Why is it unique to espresso,
what's going on here? Crema begins in the roasting process. When you roast coffee, you generate CO2. It's a kind of by-product
to some of the reactions that go on inside the coffee
bean as it goes brown. Things like the Maillard reaction or the Strecker degradation. They produce CO2 as a by-product. That CO2 is trapped inside the coffee bean and if your coffee bean is fresh, there'll still be lots and lots inside it when you come to put it in your grinder to make yourself some coffee. So you grind your espresso nice and fine. You tamp it down, you put
it in and you brew it. That hot water comes
into your brewing chamber and hits that coffee. Now, one of the properties of water is that the higher the pressure
that water is under, the more CO2 that it can dissolve. So that's what's kind of happening here. As the water is passing
through those grounds at nine bars of pressure, any CO2 that's in them that is available is getting dissolved into the water. Essentially you're kind
of force carbonating your brewing liquid at this point using the CO2 in the ground coffee. The moment, however, that
the coffee leaves the basket and it goes from being in
a pressurized environment to an atmospheric environment, right, there's no more pressure
on the coffee anymore. Well, the water has become
super saturated with the CO2 and it can't keep hold of it anymore. It can't keep it dissolved and so it comes out of
solution as a bubble. I'll give you a brief visual
explanation of this one to hopefully make a bit more sense. We're gonna need two things here. This, not particularly
full bottle of espresso. This is old espresso, it's
brewed a little while ago. It's got no crema on it
whatsoever, but it is espresso and what I'm gonna do, is carbonate it. I'm gonna sort of mimic the
espresso brewing process. From that perspective, I'm
gonna force carbonation into the liquid and it'll
be done so at high pressure, and when we get rid of that pressure, well something interesting should happen. So to force carbonate it, I obviously need a tank
of CO2 like this one. So I'm gonna use this, I'm gonna just push some air out of here, 'cause
air inhibits carbonation and then... So it might not look like it, but the excess CO2 is dissolved
now into the coffee below, just like when you're brewing espresso. And so when I release the pressure... And look, just like on any soft
drink that you might expect, a layer of foam has formed. Now with espresso, the
carbonation is kind of different. It's not as intense as it
would be in a soft drink. You wouldn't get as
bigger, coarser bubbles coming out of solution as
you would do in espresso. The foam in espresso is
much, much, much finer, but the principle is really the same, which begs the question,
why does coffee foam? In order to explain this, very quickly we need to
talk about why things foam in the first place. Generally speaking, a foam is a bunch of air bubbles trapped in a liquid and something in that liquid
is called a surfactant, a surface active agent. It's something that wraps
itself around a bubble of air and it makes that bubble strong. Now, the reason it wraps
itself around a bubble of air, more often than not, is that part of that
thing really hates water, while the rest of it quite likes water. So it's desperate. It's sort of repelled by water. It's desperate to find
anything that isn't water. A gas bubble is a wonderful thing, because all the bits that
hate water can face the gas, all the bits that like
water can face the water. Now, in espresso there are
a lot of different compounds that are surfactants. In fact, caffeine at a
high enough concentration will act as a surfactant, but it isn't really playing a role here. There's been a lot of
research done on this and broadly speaking, they
think the active surfactants in espresso are probably
things like melanoidins, a protein derived, roasting byproducts. There are other things in coffee that do play a role in foaming, but they may not be the
primary drivers of foaming. And so that's how we get crema. We've got our espresso, you dissolve in the melanoidins, some other compounds too, CO2 gets dissolved in as well, leaves the basket, CO2
can't stand solution, appears as a bubble inside the espresso and then gets trapped, wrapped up in all these lovely surfactants and made strong as a foam. But somehow crema retains
more of a mystique than say, the head on a pint of beer, but they're basically the same thing. They've happened for the same reasons. But what is it about crema that
just gets people so excited? Now firstly, it might be the color. Crema looks stunning. Now the color is tied
to a couple of things. It's primarily tied to the
color of the liquid down below. Now, espresso looks like it's just one very dark
brown color, but it's not. A less extracted or a weaker espresso will produce a less brown
foam, stands to reason, but it isn't just concentration, because roast level
also plays a role here. The darker you roast coffee, the darker the color of
that liquid is gonna be and therefore the darker
the foam is gonna be. In addition, the darker
that you roast coffee, the more CO2 that you produce
and it isn't just roast. Traditionally in Italy, robusta plays role in
many espresso blends. Now leaving aside the debate on whether we should call it
robusta or Coffea canephora, we'll come back to that
another time maybe, the presence of robusta
has been kind of desirable to many Italian roasters for a long time, not just because it's cheap and not just because it has
low acidity and high body, but because it gives you more crema. In fact, studies suggest that robusta typically has about twice the
CO2 content after roasting than Arabica, which is super interesting. But it comes with one more twist. Robusta typically has
less oil, less lipids, less fats in it than Arabica. Now you might've made meringue and at some point you might've learned that getting a little bit of
egg yolk in your egg white is a no go for foaming, because in that particular foam, the fat in the egg yolk
provides an alternative to the air bubble for the
proteins in the egg white, which means you have a much,
much, much less stable foam, because there are choices in a way. It can go for the fat,
it can go for the air. Same is true, kind of in espresso. If you're brewing coffee with Arabica, chances are your emulsion, those little tiny droplets of oil that pressure have emulsified
in the liquid below, well those oil droplets
are actually working against your crema. The higher the lipid
content of the coffee, the less stable the foam is gonna be and that's been backed up
by quite a lot of research. Now people will talk about
crema as if the emulsified oil in the crema is a really
important part of it and what makes it good. Yes, there is emulsified oil in the crema, but only because there's emulsified oil in the espresso liquid and
the liquid made the foam, but it's working against
the crema's lifespan by being there and as a side
note, you might then wonder, if I paper filtered my espresso, if I got rid of the oils in my espresso, would I have longer lasting crema? That's a good question. We ran a little test. We pulled two shots side by side. One of which had been paper filtered using an Aeropress filter
at the bottom of the basket. Both of them had nice crema. Both of the cremas lasted as long as you would want them to and certainly longer
than the sort of lifespan in which you would typically want to drink an espresso within. So not worth the extra
step from that perspective. Now, one more little aspect
that came up a few times in the papers, and this goes
back to how espresso looks is, is tiger flecking or tiger stripes or whatever you wanna call that flecking that you'll often see on
the top of an espresso. This is very common
when you brew with a lot of different coffees, they're
typically more of a kind of medium to medium dark or dark roasts, very light roasts, you won't
get as much flecking on there, because these flecks are
little tiny pieces of coffee. They're just tiny
particles of ground coffee that have made it through the basket that are stuck in the foam. These look beautiful. They look really good, both in the cup and under
a microscope too, actually. They look kind of
interesting there as well. There is speculation in
the scientific community that these tiny pieces of coffee actually help stabilize the foam. It's kind of an interesting idea. Having read a bunch of papers,
I'm not necessarily sure I truly understand why
that might be the case and I'm not sure that I've
seen that in the real world. Interestingly, they did note that robusta doesn't really produce that much in terms of the kind of tiger
striping or flecking on top, which I just thought was an
interesting little side note. Now all of this leads us to what I think is the most
important question, which is, is crema good, is it desirable? Is it helpful, is it necessary? Before I answer that, I wanna talk about two other quick things. Firstly, this video has an ad in it and therefore it has a coffee giveaway. If you are out of work,
you've been laid off, if you're struggling for money and you can't access great coffee, click the link in the description,
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sponsor, which is Squarespace. If you need a website or a domain then I would recommend using Squarespace. I've been using Squarespace for years now and it has made building
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off any website or domain. Thanks to Squarespace for
sponsoring this video. I will put a lot of links to
different scientific papers up on my particular website. There'll be a link in the description to that particular page. If you wanna get deeper into the science, there's one particular paper
I would recommend strongly as a starting point and I'll put in a few little supplemental references that you might find interesting too. But let's talk about, is crema good? And from a scientific
perspective, it's interesting. It's not as clear cut as you might think. Now, crema is a great piece of feedback. It says you've brewed
the espresso pretty well. It doesn't say if the
coffee was good or bad, if it was well roasted or badly roasted, but it says you've brewed
fresh coffee slow enough to produce a good dense
foam, you've done okay. Or you can think of it another way, if you brew a shot that
doesn't have good crema, something has definitely gone wrong. But does it really enhance
the sensory experience? And here it's interesting, because broadly speaking the
answer is kind of, but no. Now, years ago I got myself
in trouble with the internet for advocating skimming off
the crema for an espresso. It wasn't even my idea. It had come from the coffee
collective in Denmark who've been doing it for americanos, I did it with an espresso
and was astounded by the difference that it made. Try it for yourself, brew an espresso, get a couple of teaspoons and
skim off a layer of crema, stir and drink the shot and you'll find a substantial
reduction in the bitterness and kind of roasty
quality of that espresso. It might also be lacking
and you might argue that it's more effort than
it's worth and life is fine. You can just stay and drink your espresso and you can have a nice time. And I won't argue with you there, but this has been backed
up by proper research too. There was a paper published
by Dr. Britta Folmer and others, I think she talked
about it in a Rico talk, that sort of said that
varying the amount of crema, essentially varied the
presence of the roasted note, I think was their language, the kind of roastiness
essentially of the coffee, more crema gave a more intense, kind of a roasty quality to it. Now that paper did also talk about how the sort of perception
or very top level, flighty aromatics varied with
different levels of crema. Essentially they were more
perceptible with more crema, but did also say that broadly speaking, from a sensory perspective, there were not strong
differences in the taste profiles of the espresso, based on
how much foam they had, outside of this roasted note that really varied across all of them. For me, skimming espresso
massively reduces the bitterness. And I think in part, because
all of those fine pieces of ground coffee that
are trapped in the foam, well they get whipped out and taken away and you don't have to taste them. If you've ever ended up
with any amount of grounds in your mouth for whatever reason, you know that they're not a fun time. We enjoy, we taste with
more than just our mouth and our noses, how
things look has an impact and a great looking crema does enhance the joy, the pleasure of
espresso, even if it doesn't do it in that kind of objective way. I'd like to think crema plays a role in the kind of tactile aspect, but I'm not sure in a blindfold if I could tell the difference between one that had lots of crema and one that kind of didn't. The texture of espresso
primarily comes from the concentration of the liquid, as well as the particular
compounds that you've dissolved, which is kind of down to the coffee that you started with. Now, I did wonder if
you could actually cheat and get more crema somehow. So I did try force
carbonating coffee beans. Essentially, I put a bunch
of coffee beans in a bottle, squeezed out as much air as I could and then aggressively carbonated them. Didn't really seem to make any difference, even if I held it under
pressure for a little while. So in case you're curious,
I tried it for you, not the biggest result. Such is life. So a quick summary, Arabica produces less crema than robusta, but darker roasts produce more
crema than lighter roasts. Fresher coffee will give you more crema. The color of crema is about
how dark the roast was to start with and how strong the espresso that you've made it and that's kind of it. Crema is beautiful, but
you don't need to chase it. You don't need to worry about it. Eking out a little bit more may not necessarily give
you better tasting coffee. I'm interested to hear
your thoughts though. What didn't we discuss? What should we have talked
about that we didn't? Did you go down a rabbit hole of chasing as much crema as you possibly could and then find that
things maybe don't taste as good as they could? Let me know your thoughts
down in the comments below, but for now I'll say thank
you so much for watching and I hope you have a great day. Lots of you have been asking
about the French Press poster. It's now available. We worked with an incredible artist, Ashley Elander Strandquist and
she's done a beautiful job. She even put me in here,
which I kind of love, as well as a few of our friends, I think, which is kind of cool. So you can check that
out now, it's available. Link down in the description below. It's available for a limited time. Hope you like it.
