Learn the science behind:
Do you drink your coffee while walking, from a cup with a plastic lid on top (American), from a small espresso cup while standing at the bar (Italian) or do you take it slowly while sitting down, from a small narrow cup (Turkish) How you drink your coffee likely says a lot about where you’re from or where you’re at.
There are a lot of different styles of coffee in this world that all work just slightly differently. Italian espresso is made quickly, using high pressures to shoot hot water through coffee and drunk quickly. American coffee tends to be more diluted and made through filter brewing (although Starbucks has changed this considerably). Turkish coffee, as opposed to the other types, is not filtered at all, it still contains the coffee grounds and is boiled slowly in a hot source.
So what makes a Turkish coffee a Turkish coffee? And why and how is it different from all those other styles? There’s actually quite some science involved! Which is exactly what we’ll be discussing here.
Coffee as a drink has been around for centuries. The Ottoman empire, part of which is now Turkey, was actually one of the first to make it part of daily life. By now, coffee is an essential part of Turkish culture and there are coffee houses everywhere. From the Ottoman empire, coffee spread around the world, changing slightly everywhere it went.
All coffee types, whether it’s Turkish, American or Italian, start out as a berry on a coffee plant. There are various coffee plant types, the most prevalent ones being the Arabica and Robusta variety.
After harvest, the coffee berries are dried, fermented and roasted. The type of bean as well as the roasting process will all impact the flavour of the coffee. For instance, Robusta tends to be a bit more bitter and a darker roast will make a more intense, bitter coffee than a lighter roast (thanks to the Maillard reaction). However, nor the type of bean, nor the roasting process determines which type of coffee you’re making, although Turkish coffees do seem to use more heavily roasted beans in general. The coffee differences only come into play once you convert your roasted bean into coffee!
Before we can discuss the characteristics of Turkish coffee, we need to know how coffee making itself works. Just as is the case for tea leaves, you don’t actually drink coffee beans. Instead, when you’re making coffee you extract the flavour from the coffee bean into the water. Luckily, you can extract coffee flavours very well using warm or hot water.
In order to extract the right amount of flavour, most coffee preparation techniques grind down the freshly roasted coffee beans first (remember that packaging is very important to keep the roasted beans fresh & vibrant). The size of the grind will impact the strength of the coffee. The smaller the size of the coffee bean powder the larger the surface area of those powders. As a result, water has more access to the coffee flavour and will be able to extract it more easily. A smaller grind thus tends to lead to a stronger coffee.
Next up is the actual extraction process, the coffee making itself. When you make coffee you pour hot water over the ground coffee. The water extracts the flavour molecules as it flows past. You can either leave the coffee beans in the water for a long time (Turkish coffee!) or do it very rapidly at high pressures and temperatures (Italian coffee). The time you take as well as the temperature of the water all determine the final flavour and consistency of your coffee.
Time to have a look at the Turkish coffee again.
What is Turkish coffee?
Turkish coffee starts distinguishing itself as soon as you grind your coffee. Turkish coffee is ground very finely, most finely of all coffee types. It has a particle size of the coffee particles of roughly less than 1 mm. As a result, there is a lot of available surface area of the coffee particles. Using a high temperature and high pressure system such as espresso making would likely make too bitter a coffee. The Turkish preparation method though relies on this finely ground coffee and works well with it.
Once the coffee is ground, you place it in a small beaker with a handle (see image on top of post) called a cezve or ibrik. A cezve will only contain a small volume of water (not the liters of a filter coffee pot). If you want more coffee, you simply take another one. To the coffee you add water and sugar (to taste). The addition of sugar to the coffee at this point, instead of afterwards, is characteristic of Turkish coffee as well. You then heat the small beaker slowly, stirring regularly to ensure the coffee gets into good contact with the increasingly warm water.
From here on a lot of different variations exist and there is no one correct method. A core component though is to try and form a foam on top of the coffee. You do this by bringing the coffee + water mixture to the boil. The mixture will expand and rise and just before it spills over the beaker, you take it from the heat. Some methods do this heating and boiling process and few times. Others pour some liquid out at this point and continue cooking. Core component though is to bring it to the boil and form this foam. The foam is what makes the coffee more creamy than you would expect with there being no added dairy.
Once it’s done you pour it in small serving cups and it’s ready to drink!
Why does coffee foam?
Have you ever boiled a pan of water and pasta and have had the water boil over drastically? If not, have you managed to boil over a pot of milk? Both of these foam a lot when heated close to the boiling point of water, just like coffee. So what happens here?
Scientists aren’t yet completely sure what makes coffee foam so well, but there are a few common threads. Coffee contains a lot of large molecules such as proteins and polysaccharides and it contains small droplets of fat. While extract the coffee flavour from the coffee powder, a lot of these molecules come out as well.
When you bring water to the boil small bubbles are formed at the bottom of the pan. These are evaporated water. They raise up, expanding as they go. If there are not other molecules in there except for the water they would just rise up and escape again. This is why you won’t see plain water boil over. It can’t really hold onto those air bubbles. However, if there are these large molecules present in your water, they can hold onto some of that air. They will make it harder for the air to escape. As a result, the air bubbles build up and the whole liquid expands and foams. As soon as you take it off the heat though, it collapses again. This is because no gas bubbles are formed anymore and because the large molecules aren’t that good in holding onto the gas bubbles for long so they escape again into the air.
In the case of coffee those large molecules can hold onto some of those gas bubbles for some extended period of time. This is what results in that slight foamy layer. It will not be there forever though, it will disappear slowly over time. It is also the reason why some methods involve several steps of cooking and pouring. They are trying to build more of that foam!
Those large molecules in coffee that help to stabilize the foam? Those are surfactants and are also kep for making foamy Dalgona coffee.
Role of carbon dioxide
Apart from this mechanism, there seems to be another important factor in coffee foam (Illy, E., 2011). Roasted coffee beans contain carbon dioxide. This gas, which is naturally present in the air, is fixated in the beans. It is thought that during coffee brewing some of this carbon dioxide releases from the beans, into the drink. Again, those larger molecules then stabilize the resulting foam.
Drinking Turkish coffee
Once the coffee has been made and poured into your cup, it’s time to drink it. However, don’t drink it immediately, nor completely! The coffee still contains its grounds. They will sink to the bottom if you wait a while (thanks to sedimentation). However, this does take a little while, which is why drinking Turkish coffee slowly truly is the best way to go. That way, you can leave those grounds behind in your cup (and have your future read!).
Engin Akin, Essential Turkish Cuisine, 2015, section on Turkish coffee, link
Chris Arnold, Coffee Grind Chart, Sep-7 2015, I need coffee, link
Mehmet Efendi (various articles), Turkish coffee manufacturer, link
Ralph S. Hattox, Coffee and coffeehouses – The origins of a social beverage in the medieval near east, University of Washington Press, 1985 ; a great book if you’d like to learn more about the history of coffee in Turkey and its surrounding countries
Illy, E., Navarini, L., Neglected food bubbles: The espresso coffee foam, Food Biophysics (2011) 6: 335, link
Sympatec, Know the particle size and shape of your coffee grounds for a perfect coffee taste, link