How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and a filtering system that is awe-inspiring to create the coffee you enjoy. But how exactly does espresso machine uk work?
Espresso is created by forcing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.
The Head of the Group
As the name implies the group head is the place you place your portafilter when making espresso. It disperses water in the portafilter, and then regulates the pressure of extraction. There are a variety of types of group head, each with their own advantages and drawbacks. Some focus on temperature stability, others on pre-infusion features, and others are designed to control the lever. Some include a combination like the E61. This is a very popular choice for baristas since it provides multiple advantages in one package.
As you can see in the image above the group head is made up of several notches to place your portafilter before twisting it by hand to secure it. There is also a rubber gasket in the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head permit a precise position of the portafilter which is vital for a consistent extraction.
Apart from allowing you easily connect your portafilter, the group head is responsible for maintaining an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it is always at the correct temperature to extract. This is important because even a few degrees can mean the difference between good and excellent espresso.
The Pump
The motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure needed for espresso extraction. This is different from manual piston machines that use levers. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be more affordable and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading because of excessive use and insufficient cleaning. They also increase the complexity of mechanical systems that can lead to a high price tag on even the simplest models.
Some espresso machines employ steam pressure instead of a pump in order to brew espresso. The drawback is that the boiler that produces steam also increases the temperature of water to boiling which can cause over-extraction. The machines also need to continually rebuild their pressure between cups. This requires energy and time.
A majority of espresso machines utilize a rotary or vibration pump. A vibration model uses an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at high speed. Both types of machines can make excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the part which heats the water to the ideal temperature to extract. The steam created reaches the portafilter, which holds the espresso grounds. It is then pumped into the cup. The steam generates enough pressure to push the grounds of the coffee through. This results in a whipped-up top of the espresso. This is a sign of a good espresso.
There are three types of espresso machines, each having different pumps and brew temperature. There are many ways to control the amount of brew, as well as the size of the cup that can be made by the machine.
The first espresso machines were steam-type. They used only one boiler to make both steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure at the most. The coffee tasted bitter and burned. This is why the Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most commonly used espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they picture these machines. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the water flow and pressure. This is a great solution that combines human control with mechanized consistency.
The Filter
Espresso machines typically have a filter that separates the grounds of the coffee from the hot water. The filter is also a crucial part of the temperature control system, because it stops the machine from overheating.
A filter also helps with flavor, as it permits the beans to flower for a longer period of time. This lets the beans release their flavor and improves extraction.
However it is crucial to keep in mind that even a top filter can produce a bad cup of coffee, since the quality of the beans and extraction are essential.
It's here that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead, often referred to as the brewhead, is where the portafilter (the thing you put the ground coffee into) is placed when making espresso.
Steam-driven espresso machines use hot water heated in an airtight container to make steam. The steam then pushes hot water into the grounds of the coffee under pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to push hot water through grounds and are more portable than steam-driven electric machines.