How Does Machine Espresso Work?

Machine espresso employs precise pressure and incredible filter technology to produce the perfect cup of coffee. How exactly does it work?

Espresso is made by forcing hot water under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the major difference.

The Head of the Group

As the name suggests the group head is the place you put your portafilter in when making espresso. It disperses water in the portafilter, and regulates the pressure of extraction. There are a variety of group heads each with their own advantages and drawbacks. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some have a combination of features, like the E61 one, which is to be the most popular among baristas for its ability to offer multiple perks in one package.

As you can see in the image above the group head comes with several notches to place your portafilter and then twist it manually to secure it. A gasket made of rubber is placed in the notches to create a seal when you insert your portafilter. The notches on the head permit an exact position of the portafilter which is essential for an efficient extraction.

Apart from allowing you effortlessly insert your portafilter the group head is responsible to maintain an even temperature. It does this by circulating hot water through the brew basket, and around the portafilter, making sure that it's always at the correct temperature for extraction. It is important to remember that even a slight deviation can make the difference between a good and excellent espresso.

The Pump

The motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure required to extract espresso. This is different from manually operated piston machines that employ levers. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior it is shot through the ground coffee in the group head.

Pumps tend to be more affordable and last longer than piston-driven machines. However, both types of machines may degrade due to excessive use and insufficient cleaning. They also create mechanical complexity and can lead to an expensive price for even the simplest models.

Certain espresso machines utilize steam pressure instead of a pump to brew espresso. The downside is that the same boiler that produces steam also increases the temperature of the water until it reaches boiling which can cause over-extraction. They also have to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines use an rotary or a vibration pump. A vibration model employs an oscillating disk to create pressure, while a Rotary model pushes hot coffee through the ground at a high speed. Both machines can produce excellent espresso, however rotary machines are more stable, quieter and less likely to break down.

The Boiler

The boiler is the part that heats the water to the optimal temperature for extraction. The steam that is created reaches the portafilter, which contains the espresso coffee grounds. The steam is then channeled into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This results in a whipped-up top of the espresso. This is a hallmark of a good espresso.

There are three types of espresso machines, each having a different type of pump and brew temperature. There are a variety of ways to control the brew as well as the size of the cup that can be made by the machine.

The first espresso machines were steam-based. They had one boiler to make both steam and brew however the pressure they were able to create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

https://www.coffeee.uk/categories/espresso-coffee-machines used espresso machine is a semiautomatic one with an electric pump. These are the things people think of when they think of an espresso maker. With a semi-automatic espresso machine, you grind the beans and tamp them by hand, but the pump provides regulated water flow and pressure. This is a great compromise between the human touch and the mechanised accuracy.

The Filter

Typically, espresso machines have filters that separate the grounds of coffee when they pass through the hot water. The filter is also a crucial element of the temperature control system, since it helps prevent the machine from overheating.

It also helps with flavor, as it lets you enjoy a longer bloom phase. This allows beans to let their nuances out and provides an opportunity for a better extraction.

It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, remain crucial.

This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead, also called the brew head, is where the portafilter (the container you place the ground coffee in) is placed when you're making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight container to create steam, which is then pushed through the grounds with high pressure. These types of machines are usually less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing since 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 the grounds and are significantly more portable than steam-driven electric machines.