How Does Machine Espresso Work?
The machine espresso uses precision pressure, and filter technology that is mind-blowing to make the coffee you love. How does it work exactly?
In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to 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 into the portafilter, and then regulates the pressure during the extraction. There are many different kinds of group heads each with its own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. There are even some that include a mix of features, like the E61, which is considered to be the most popular among baristas due to its capacity to offer multiple perks in a single package.
As you can see in the above photo, the group head has several notches to place your portafilter before twisting it manually to lock it in. A gasket of rubber is situated inside the notches, which helps make a seal when you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is essential for an even extraction.
The group head not only lets you to place your portafilter easily however, it also keeps a constant temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is always at the right level for extraction. It is important to realize that even a slight difference can make the difference between a good and a great espresso.
The Pump
In contrast to piston machines that are manually operated, that use a lever to pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be cheaper than piston-driven models, and they tend to last longer, but both types of machines can be damaged by excessive use and inadequate cleaning. They also increase the complexity of mechanical systems that can lead to an expensive price for even the simplest models.
Some espresso machines use steam pressure instead of a pump to make espresso. The drawback of this is that the boiler that produces steam also increases the temperature of water until it reaches boiling which can cause over-extraction. Additionally, these machines frequently have to restore their pressure between cups, which requires time and energy.
A large majority of espresso machines employ a rotary or vibration pump. A vibration model makes use of a rotating disk to generate pressure, whereas the rotating model pushes hot water through the ground at a fast speed. Both types of machines are capable of producing excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler makes the water warm to a temperature that is ideal to extract. The steam created reaches the portafilter, which holds the espresso grounds. It is then funneled into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This creates a foam on top of the espresso. This is one of the main characteristics of a great espresso.
There are three types of espresso makers, and they differ in the kind of pump they use and how hot the espresso is. There are many ways to control the amount of brew, as well as the size of the cup that can be produced by the machine.
The first espresso machines were steam-type. The earliest espresso machines were steam types. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic with an electric pump. These are the images people have when they think of an espresso machine. If you have a semi-automatic machine you have to grind the beans and then tamp them by hand, but the pump controls the flow of water and pressure. This is a fantastic compromise between human control and mechanised reliability.
The Filter
Espresso machines usually have filters that separate the grounds of the coffee from the hot water. The filter is also a vital element of the machine's temperature control, as it prevents overheating.
It also helps with flavor, since a filter allows for a more prolonged bloom phase. This helps the beans release their flavor and gives an opportunity for better extraction.
However it is crucial to remember that even a top filter could result in a bad cup of coffee, because the quality of the beans and extraction is still crucial.
This is where the magic happens. It's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you place the portafilter, the espresso machine sale device which you put the grounds of coffee into when making espresso.
In the steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which then pushes the hot water through the grounds with high pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. They are however limited to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They make use of an air compressor to push hot water across the ground, and are more mobile than steam-driven electric espresso machines.