Today we talk again of the much-loved Italian espresso, but in a different guise: let’s discover the structure of the espresso machine, so as to better understand the incredible drink it produces.
So here is the article that explains the Structure of the Espresso Machine!
If you want to find out more about the world of espresso:
Also watch the video on the history of the espresso machine!
The Structure of the Espresso Machine
The espresso coffee machine is a real jewel of Italian engineering, admired and copied all over the world.
The structure is very similar for both the professional machines that we find in bars and for domestic machines. We will see the exact difference at the end of the article.
Professional machines are generally more performing.
The parts that interest us the most are:
- Water heater;
- Boiler pressure gauge;
- Heat exchanger;
- Electric pump;
- Brew group, filter holder and filter;
- Hot water tap;
- Steam launch.
1. The boiler
The boiler is usually made of steel, copper or brass and is used to dispense hot water, heat the water for coffee extraction and create steam for the steam wand.
The water deriving from the water mains passes through a softener or purifier, which precisely eliminates the substances unsuitable for the preparation of the espresso, such as limestone, chlorine, etc.
At this point it arrives “clean” inside the boiler, where it is heated and kept at the right temperature for the entire required duration of service.
In the boiler, the water arrives at temperatures of around 110-120°C and with a pressure between 1.1 and 1.4 bar.
Furthermore, as can be seen in the image, the boiler is never completely full, because in the upper part, thanks to the high temperatures, steam is formed which the barista will then use to heat and froth the milk for cappuccino or macchiato.
2. The pressure gauge in the boiler
The pressure gauge is precisely that part of the machine visible to the operator which allows you to check the correct or incorrect pressure inside the boiler, which as we have just said must be between 1.1 and 1.4 bar.
3. Heat exchanger
The heat exchanger is the system that allows you to heat the water needed to extract the espresso.
In fact, to prepare the coffee we do not use the water present in the boiler for two reasons:
- The temperatures are too high. The water in the boiler reaches over 110°C, while to extract a coffee we should stay between 90 and 95 degrees;
- The water in the boiler is stagnant. It is true that it comes from the purifier and therefore has no more limestone or other substances, but it remains in the boiler for a long time at very high temperatures and unpleasant bacteria or sediments could therefore form.
That’s why the heat exchanger is used!
You have to imagine a small pipe, usually made of copper, which carries the purified water from the water mains.
This tube, passing through the boiler, allows the heating of the water inside it.
The water for making the espresso is therefore always purified, sweetened and fresh!
4. The Electric Pump
It is the tool capable of “squeezing” the water against the ground coffee stick with very high pressure, generally around 9 atmospheres.
This is what makes espresso so!
In fact, espresso is a very concentrated, dense coffee-based drink with a creamy surface. What allows the creation of the cream, combined with other factors, is precisely the pressure. Without the pressure, the cream would not be able to form in the cup.
In fact, let’s think of the moka: even with the best moka in the world and using the same coffee that we use for the espresso, we will never get the exact same crema of the espresso, precisely due to the lack of this great pressure!
If you want to know the difference between espresso and capsules, click below:
5. The brew group, the filter holder and the filter
The dispensing unit is the part to which the filter holder is attached, i.e. the arm that the operator attaches and detaches to insert the ground coffee and make a new coffee.
It has a shower, which distributes the water evenly on the ground, and from the gasket, which allows the total adherence of the filter holder.
The filter holder, on the other hand, is, as we have said, the arm that we hold in our hand with the filter that contains the ground coffee inserted inside. The latter, being perforated on the bottom, lets the infused drink come out.
6. The hot water tap
This component is the one from which the hot water comes out to prepare tea, for example.
In this case, in most espresso machines, the hot water comes directly from the boiler, not from the heat exchanger as in the case of espresso.
Only in a few machines of the latest generation does the water come out with the heat exchanger system.
7. The Steam launch
And we have arrived at the last part of the structure of the espresso machine, namely the steam wand: the tool that allows the steam to escape in order to froth the milk.
This then draws the steam from the boiler and lets it out.
Operation of the espresso machine
So:when we press the coffee extraction button, the machine draws a small amount of water from the water mains, passes it through the coil, i.e. the heat exchanger, to heat it, and after a few seconds of pre-infusion the electric pump forces the water with great pressure through the ground ball, extracting the substances and aromas of the coffee in a very energetic way.
Difference between a bar machine and a home espresso machine
The difference between a home machine and a bar machine lies in the dimensions.
The boiler in domestic ones is smaller and has more difficulty in keeping the water hot enough and at a constant temperature for extraction, as well as providing even less steam to froth the milk.
Furthermore, the structure of the coffee machine is heavier and more robust, allowing better pressure retention to extract the espresso to its full potential.