How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and mind-blowing filter technology to create the perfect cup of coffee. But how exactly does it work?
To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.
The Group Head
The name implies the group head is the place you place your portafilter when making espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are numerous kinds of group heads each with distinct advantages and drawbacks. Some are designed to provide temperature stability while others are built to handle pre-infusion. Others are made to control the lever. There are some that come with a range of features, such as the E61 one, which is the most popular choice among baristas for its ability to provide multiple benefits in one package.
As you can see in the photo above, the group head has many notches in which you can put your portafilter, then twist it by hand to lock it in. There is also a gasket made of rubber that is a part of the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of the portafilter. This is essential for an efficient extraction.
The group head does not just allow you to insert your portafilter easily however it also keeps the temperature at a constant level. It does this by circulating hot water through the brew basket and around the portafilter to ensure that it is always at the correct temperature to extract. It is crucial to keep in mind that even a few degree difference can make the difference between a good and a great espresso.
The Pump
The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines that rely on levers. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.
Pumps are typically less expensive than piston-driven machines, and they tend to last longer, but both types of machines could get damaged through overuse and lack of cleaning. They also make mechanically complex which can result in the cost of even the simplest models.
Certain espresso machines remove the pump completely and instead employ steam pressure to create espresso. This could lead to over-extraction since the boiler that makes steam also warms the water to boil. In addition the machines often have to restore their pressure between cups, which takes time and energy.
Many espresso machines utilize either a rotary or vibration pump, with a vibration model that uses a vibrating disc to create the pressure, and a rotary model pushing hot water through the grounds under 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 that heats water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter which holds ground espresso beans and is then funneled down into the cup. During this process the steam creates enough pressure to push the grounds of coffee through. This results in a layer crema on top. This is one of the hallmarks of a great espresso.
There are three types of espresso makers, and they differ in the kind of pump they use and the degree of heat that the espresso is. There are various ways that the brew can be controlled as well as the size of the cup the machine can make.
The first espresso machines were steam-type. The earliest espresso machines were steam types. The coffee tasted bitter and burned. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic with an electric pump. These are what people imagine when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself The pump, however, regulates the flow of water and pressure. This is a fantastic compromise between human control and mechanized reliability.
The Filter
Typically, espresso machines employ a filter to separate out the grounds of coffee as they move through the hot water. The filter is also a vital element of the temperature control system since it helps prevent the machine from overheating.
A filter can also help with flavor, as it permits a longer flowering phase. This lets the beans release their nuances, and allows for better extraction.
However it is crucial to remember that even a great filter can result in a poor cup of coffee, as the quality of the beans and extraction is still essential.
It's in this area that the magic happens. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you place the portafilter, the thingy which you put the grounds of your coffee into while making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. Steam then pushes the hot water through the grounds at high pressure. These machines are less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.
In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They make use of an air compressor to force hot water into the ground, and are more mobile than electric steam-driven espresso machines.