17 Apr 2014

Why do we...Judge our Espresso Based on its Crema?

Sant'Eustachio coffee latte art

Crema. Since the blog video of JimSeven (James Hoffman) titled: "Crema is Rubbish", crema has been a somewhat controversial and dividing foam in the coffee industry. Whether you agree with Hoffman that perhaps crema should be either skimmed off or stirred through the espresso or americano, or not, the whole discussion did open peoples eyes.

Crema was always perceived as necessary, not only as a 'look-at-me-I'm-well-extracted', but also for flavour. After Hoffman's blog baristas across the world started to actually taste their crema and, in stead of just assuming that it should be present, started to decide to deliberately serve their coffee with or without crema.

The whole crema debacle subsided a little in my brain, after all, we are talking about a blog post from 2009. But after working more with super automated espresso machines
and visiting the Sant'Eustachio cafe in Rome, its back!

Sant'Eustachio is one of the strangest cafes I have  visited. Ever. Nothing that is happening behind the machine is visible. Absolutely nothing. The machines are shielded off on the sides with metal plates. The sides of the bar are either closed off, or closed by a high door. Even underneath the machines everything is shielded off. Everything.
As a barista, this is very frustrating. Especially when receiving an espresso with the most ridiculous amount of frothed crema. The moment the espresso is put in front of you, your whole train of thought halts. Your mind goes blank for a few seconds. And then the first thought is: "What the crema"?!
At this point I went back to the bar to see if I really could not see anything. And you really cannot see anything. After researching a bit back in our beautiful Rome apartment, I found that nobody actually knows the secret. Several newspapers have tried to find out what the mechanisms are behind the frothy several centimetres high crema at Sant'Eustachio, and as of yet, nobody knowsssss.

The espresso itself was not great. Not bad and not good, leaving it somewhere in the middle of the espresso database in my head. The crema really did not taste of much either, being mostly in the way of consuming the actual drink, resulting in me skimming it off on to a napkin on the side.

the ridiculous crema covered in mystery

So how did they create this ginormous amount of crema? As again, Hoffman explains in another blog post, crema does not consist of the oils and fats in the coffee bean, contrary to what many believe. To explain this, think of frothing up your egg whites. If you get any yolk, or if your bowl is fatty or oily in any way, you will be unable to froth up your egg whites. In other words, the oils and fats in your coffee contributes to the breaking down of the crema, not to building it. So what is crema then?

In my blog post on blooming I discussed CO2. It is the CO2 that creates the crema of an espresso. During extraction the CO2 is released, and due to the pressure used in an espresso machine the CO2 comes out as little bubbles. If you want more a scientific explanation, I highly recommend Hofmann's blog, a must read for the coffee professional anyway. So after reading this post, go there! Read and learn.

So how can you influence crema? Several factors influence crema. Firstly, roast date. The fresher the roast, the more CO2 is present in the beans, resulting in more crema.
Second, what could play a role is what type of coffee is used. Are the beans from an Arabica or Robusta plant? It is probable, if we again keep our frothed egg whites in mind, that oil causes the crema to dissipate. Hence the more oils and fats in the coffee, the quicker the crema disappears. As Arabica as about twice the amount of lipids than Robusta, Robusta usually has a stronger crema.
Thirdly, of course, we cannot forget the influence of extraction itself. A bad extraction will result in a bad crema, and a good extraction in a good crema. Underneath this blog post you can find what you should look for in a crema.
And finally, what could influence the crema, of course is actual frothing or adding something causing it to froth more. This is what super automatic machines do, and then I mean actually frothing up the coffee, not necessarily adding something. This is the reason that even liquid coffee, powder coffee or machines working without pressure, can create a coffee with a crema. In the spout just above the cup there is a rotary system that froths up the coffee, before it lands in your cup underneath. The width of the spout, the technique behind the rotary system and of course the shape of the cup, all influence the quality of this artificial crema.
Adding, for example, baking soda, can also create a frothed crema. David Lebovitz, who is living the sweet life in Paris, suspects this is secret behind the mystery of the wall of crema in the Sant'Eustachio cafe in Rome.

I suspect he is right. Why? In my utter frustration, never ending curiosity and lengthy hanging at the bar in wait, I got lucky. As one of the attending, perfectly clothed baristas stepped out from behind the bar without overlooking my prowling self, he swung open the door to the bar, and I got a glimpse. And I saw. I saw the strangest thing. I saw big RVS mixing bowls on the bar in front of the espresso machine. One bowl per group head. What they were doing there or how they were used, we will perhaps never know. Filled with baking soda? Used to froth espresso? The baristas, who saw my obvious excitement, quickly made sure the doors where closed, and during the rest of my stay, did not let me out of their sight, rather working with less behind the bar, than risking me seeing more.

The strange thing, as if brewing in absolute secrecy and ridiculous amounts of crema aren't strange enough, I did buy coffee beans to try at home. 
Now, although I have a very decent Expobar dual boiler system at home, I do not have any frothing agent. Nor was the roast very recent. And Sant'Eustachio works with 100% Arabica beans.
I did get the best crema I have ever had at home. Especially when I extended the extraction. So who knows, there could be another secret. Perhaps the roasting, or the fact they do this on wood adds an other dimension. Either that, or they actually are magicians.

What should you look for in a crema
If it hasn't been skimmed off

Crema can be an indicator that the espresso was well extracted. A well extracted espresso will have a crema that is compact, persistent and have a certain elasticity. Meaning that when you stretch the crema, by tilting your cup, or when you pull your spoon through, the crema should not break and should fall back in to place immediately.

The colour gives an indication of roast, and also of extraction. So; the lighter the crema, the lighter the roast, or the lighter the extraction. And vice versa.
If your crema has dark leopard-like spots, this does not necessarily have to mean that the extraction was not done well. What causes these spots is still up for debate. It could be over extraction, overly heated water, or it could be fine coffee grounds that slip through the filter basket. However, usually an even crema is considered to have a better espresso underneath. 

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