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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the perfect cup of coffee. But how exactly does it work?

barista espresso machine is produced by pushing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee but the difference is in the pressure.

The Group Head

The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter before controlling the pressure of the extraction. There are several different types of group head, each with their particular advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. Some come with a combination of both, like the E61. This is a very popular choice for baristas since it provides multiple advantages in a single package.

As you can see in the above photo, the group head has a number of notches. The portafilter is placed in these notches, then turn the head around to secure it. There is also a gasket made from rubber which is located inside the notches to help create an airtight seal after inserting your portafilter into the machine. The notches on the head allow for a precise positioning of the portafilter which is essential to ensure an efficient extraction.

The group head is not just able to allow you to put in your portafilter easily however, it also keeps an even temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket, making sure the temperature is always right to extract the coffee. This is important because even a few degrees can be the difference between a good and great espresso.

The Pump

The motorized pumps used in rotary espresso machines provide the nine atmospheric bar pressure that is required to extract espresso. This is different from manual piston machines that rely on a lever. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven machines and tend to last longer, although both types of machines may degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, which can raise the cost of even most basic models.

Certain espresso machines eliminate the pump completely and instead use steam pressure to brew espresso. This can result in over-extraction because the boiler that makes steam also warms the water to boil. These machines also have to continuously rebuild their pressure between cups. This takes energy and time.

Many espresso machines make use of a rotary or vibration pump. A vibration model makes use of a vibrating disk to generate pressure, whereas a rotary model pushes hot water through the ground at a high speed. Both models can make a great professional espresso machine for home, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the one that is used to heat the water to a temperature that is ideal for extraction. The steam that is created reaches the portafilter, which is a container for espresso grounds. It is then pumped into the cup. During this process the steam causes enough pressure to push the grounds of coffee through. This results in a layer crema on top. This is one of the main characteristics of a great espresso.

There are three kinds of espresso machines, each having distinct pumps and brew temperature. There are a variety of ways to control the brew and the size of the cup that can be made by the machine.

The first espresso machines for home machines were steam-types. They utilized a single boiler to make steam and brew, however the pressure they were able to produce was very low - just two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most common espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic machine, you need to grind the beans and then tamp them by hand, but the pump provides regulated water flow and pressure. This is a fantastic compromise between human control and mechanised reliability.

The Filter

Typically, espresso machines employ filters that separate the coffee grounds as they pass through the hot water. The filter is also an essential element of the machine's temperature control, as it prevents overheating.

Filters also aid in flavor, as it permits a longer flowering phase. This lets the beans release their flavors, and improves extraction.

It is important to keep in mind that even the finest filter could result in a poor cup of coffee. The quality of the beans and the extraction process, are still very important.

It's here that the magic happens. This is the reason why espresso tastes so good. The grouphead, also referred bean to cup espresso machine as the brew head, is the place where the portafilter (the thingy you put the coffee ground into) is placed when making espresso.

Steam-driven mini espresso maker (Additional Info) machines make use of hot water heated in an airtight container to produce steam. The steam then pushes hot water through the grounds of the coffee under pressure. These machines are cheaper and easier to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal conditions for brewing because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.

In recent years, compressed-air-pump-driven espresso machines have been gaining popularity. They use an air compressor to push hot water across the ground and are much more mobile than electric steam-driven espresso machines.