How Does Machine Espresso Work?
The machine espresso is made using precise pressure and filter technology that is mind-blowing to make the coffee you enjoy. How exactly does it work?
Espresso is made 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 Head of the Group
As the name implies, the group head is where you place your portafilter when brewing espresso. It disperses the water into the portafilter and regulates the pressure during the extraction. There are numerous kinds of group heads each with distinct advantages and drawbacks. Some are specifically designed for temperature stability while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some include a combination such as the E61. This is a favorite among baristas since it provides multiple benefits in one package.
As you can see in the photo above the group head comes with several notches to place your portafilter and then twist it manually to secure it. There is also a gasket of rubber in the notches to help create the seal when you insert your portafilter into the machine. The notches on the head allow for a precise placement of the portafilter, which is necessary for an efficient extraction.
The group head does not just allow the portafilter to be inserted easily, but it also maintains a constant temperature. This is achieved 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 vital, because even a few degrees can mean the difference between excellent and great espresso.
The Pump
In contrast to manual piston machines that use a lever to pressurize water, rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure that are required for espresso extraction. 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 tend to last longer, but both types of machines may become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which can increase prices of even simpler models.
Some espresso machines use steam pressure instead of a pump in order to brew espresso. This can result in over-extraction because the boiler that makes steam also causes the water to boil. Additionally the machines often have to restore their pressure between cups, which takes time and energy.
Many espresso machines make use of an rotary or vibrating pump, which has a vibration model that uses a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds at high speed. Both machines can make excellent espresso, but rotary machines are more quiet, durable and less likely to break.
The Boiler
The boiler is the element that heats the water to the ideal temperature for extraction. The resulting steam reaches the portafilter, which contains ground espresso beans and is then pumped into the cup. During this process, steam creates pressure and pushes through the grounds of the coffee. This results in a whipped-up top of the espresso. This is the hallmark of a good espresso.
There are three kinds of espresso machines, each having different types of pumps and brew temperature. There are a variety of ways to control the brew as well as the size of the cup that can be produced by the machine.
The first espresso machines were steam-types. coffeee.uk utilized one boiler to create both 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 burnt and bitter. This is why Milanese makers 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 imagine these machines. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the flow of water and pressure. This is an excellent combination of human control and mechanised accuracy.
The Filter
Espresso machines typically use a filter that separates the grounds of coffee from hot water. The filter is also a crucial component of the temperature control system, as it prevents the machine from overheating.
It also aids in flavor, as it allows for a more prolonged bloom phase. This allows beans to let their nuances out and provides an opportunity for better extraction.
However it is crucial to keep in mind that even a top filter can result in a poor cup of coffee, because the quality of the beans and extraction is essential.
It's here that the magic occurs. This is what makes espresso taste so good. The grouphead, also called the brewhead, is where the portafilter (the thing you put the coffee grounds into) is located when you're making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to make steam. The steam then moves hot water through the coffee grounds under high pressure. These types of machines are typically cheaper and easier to maintain than pump-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, espresso machines driven by a compressed air pump have become increasingly popular. They use an air compressor to push hot water through grounds and are much more portable than steam-driven electric machines.