How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and mind-blowing filter technology to make the perfect cup of coffee. How does it work exactly?
Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee. However, it is the pressure that makes the main difference.
The Group Head
The group head is the portafilter you insert when brewing espresso. It disperses water in the portafilter and regulates the pressure of extraction. There are various kinds of group heads, each with their distinct advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion options, and others are designed to control the lever. Some include a mix of features, such as the E61, which is to be the most popular among baristas due to its ability to offer multiple benefits in a single package.
As you can see in the image above the group head is made up of several notches to place your portafilter and twist it manually to lock it in. A gasket made of rubber is positioned inside the notches, which helps make a seal when you insert your portafilter. The notches on the head allow for a precise placement of the portafilter, which is necessary for an even extraction.
The group head is not just able to allow you to place your portafilter easily however, it also keeps the same temperature. This is accomplished by cycling hot water around the portafilter and through the brew basin, ensuring that the temperature is at the right level for extraction. This is important, as even a few degrees can make the difference between a excellent and great espresso.
The Pump
Unlike manual piston machines, which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps to provide the nine atmospheric bars of pressure needed for espresso extraction. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.
Pumps are typically less expensive than piston-driven models, and they tend to last longer. However, both types of machines may be damaged by excessive use and inadequate cleaning. They also increase the complexity of mechanical systems, which can result in an expensive price for even the simplest models.
Some espresso machines remove the pump completely and make use of steam pressure to make espresso. The drawback is that the same boiler that produces steam also raises the temperature of the water until it reaches boiling which can cause excessive extraction. Additionally, these machines frequently have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines make use of the rotary or vibration pump, with a vibration model using a vibrating disc that generates the pressure, and rotating models that push hot water through the grounds at high speed. Both types of machines can make a great espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to an ideal temperature to extract. The steam that is created is then directed to the portafilter, which is a container for espresso grounds. The steam is then channeled into the cup. During this process, the steam creates pressure to push through the grounds of coffee espresso machines the coffee. This results in a whipped-up top of the espresso. This is a hallmark of a great espresso.
There are three kinds of espresso makers. They differ in the type of pump they employ and the degree of heat that the brew is. There are various ways to control the brew as well as the size of cup that can be made by the machine.
The first espresso machines were steam-type. They used one boiler to create both steam and brew but the pressure they could produce was very low - just two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic espresso machine, you need to grind the beans and then tamp them by hand, but the pump is able to regulate the flow of water and pressure. This is a fantastic combination of human control and mechanised consistency.
The Filter
Espresso machines usually use a filter that separates the grounds of the coffee from hot water. The filter is also an essential component of the machine's temperature control, since it stops overheating.
A filter also helps with flavor since it allows for the beans to flower for a longer period of time. This allows beans to release their nuances and gives an opportunity to improve extraction.
However, it is important to remember that even a good filter can result in a poor cup of coffee as the quality of the beans and extraction are essential.
It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead, also referred to as the brewhead, is where the portafilter (the thing you put the ground coffee into) is placed when you're making espresso.
Steam-driven espresso machines make use of hot water heated in an airtight container to create steam. The steam then pushes hot water into the grounds of coffee at high pressure. These machines are cheaper and easier to maintain than pumps-driven models. They are however limited to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines driven by a compressed air compressor 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.