How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to create the perfect cup of coffee. What exactly is it that makes it work?
Espresso is made by forcing hot water under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.
The Group Head
As the name implies the group head is the place you place your portafilter while brewing espresso. It disperses water into the portafilter and controls the pressure of the extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are focused on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. There are also some that contain a variety of features, like the E61 that is the most popular choice among baristas due to its ability to offer multiple perks in one package.
As you can see from the above photo, the group head is equipped with several notches. The portafilter is placed into these notches and twist the head to secure it. A gasket of rubber is situated inside the notches to help create a seal when you insert your portafilter. The notches on the head permit an exact placement of the portafilter, which is crucial to ensure an even extraction.
Aside from allowing you to effortlessly insert your portafilter the group head is also responsible for maintaining an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is always at the right level for extraction. This is crucial, since even a few degrees can make the difference between a excellent and great espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps that provide the nine atmospheric bars of pressure required for espresso extraction. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be cheaper and last longer than piston-driven machines. However, both types of machines are susceptible to degrading due to excessive use and poor cleaning. They also create mechanical complexity, which can result in a high price tag on even the most basic models.
Some espresso machines use steam pressure instead of a pump to brew espresso. The drawback is that the boiler that produces steam also raises the temperature of water until it reaches boiling which can cause excessive extraction. Additionally these machines are often required to restore their pressure between cups, which takes time and energy.
A large majority of espresso machines employ an rotary or a vibration pump. A vibration model makes use of the vibrating disk to create pressure, whereas a rotating model pushes hot water through the ground at high speed. Both models are capable of producing excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to an ideal temperature for extraction. The steam that is produced gets to the portafilter which holds the espresso grounds. It is then pumped into the cup. During this process, steam causes pressure to push through the coffee grounds. This results in a whipped-up the top of the espresso. This is one of the main characteristics of a good espresso.
There are three kinds of espresso makers, and they differ in the type of pump they use and how hot the espresso is. There are various ways in which the brew could be controlled, as well as the size of the cup that the machine can make.
coffee machine espresso were steam types. They had a single boiler to make both steam and brew however the pressure they were able to generate was low - only two bars of atmospheric pressure at the most. This resulted in the coffee tasting burnt and bitter. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most well-known espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic machine, you need to grind the beans and tamp them yourself but the pump is able to regulate the flow of water and pressure. This is a perfect solution that combines human control with mechanized consistency.
The Filter
Espresso machines typically have a filter that separates the grounds of coffee from hot water. The filter is also a vital element of the machine's temperature control, since it stops overheating.
Filters also aid in flavor since it allows for a longer flowering period. This helps the beans to release their flavor and gives an opportunity to improve extraction.
However, it is important to keep in mind that even a good filter could result in a bad cup of coffee, since the quality of the beans and extraction are important.
This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead (also known as the brewhead) is where you put the portafilter, which is the thingy which you put the grounds of your coffee into while making espresso.
In the steam-driven espresso machine hot water is heated in an airtight container to create steam. Steam then pushes the hot water through the grounds under high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to force hot water into the grounds, and are far more portable than steam-driven electric machines.