How Does Machine Espresso Work?
The machine espresso uses precise pressure and filter technology that is mind-blowing to create the coffee you love. 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 it is the pressure that makes the main difference.
The Group Head
As the name suggests, the group head is the place you place your portafilter while making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are several different types of group heads, each with their particular advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. Some include a mix of features, such as the E61 one, which is the classic choice among many baristas due to its capacity to provide multiple benefits in a single package.
As you can see from the picture above the head of the group is fitted with a variety of notches. You place your portafilter in these notches and then twist the head to lock it. There is also a gasket of rubber in the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches on the head allow for an exact positioning of the portafilter which is essential for an efficient extraction.
The group head not only lets you to place your portafilter easily but also maintains a constant temperature. It does this by circulating hot water through the brew container and around the portafilter, ensuring that it is always at the correct temperature to extract. It is crucial to keep in mind that even a few degree deviation can make the difference between a great and a excellent espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by removing tap water from a reservoir and pumping it through a heat exchanger before it is shot through the ground coffee in the group head.
Pumps are generally more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate due to excessive use and inadequate cleaning. They also add mechanical complexity and can lead to costly prices for even the most basic models.
Certain espresso machines remove the pump completely and instead employ steam pressure to create espresso. The drawback of this is that the boiler that produces steam also increases the temperature of the water to boiling which can cause over-extraction. Additionally these machines typically have to rebuild their pressure between cups, which requires time and energy.
A large majority of espresso machines employ either a vibration or rotary pump. A vibration model utilizes a vibrating disk to generate pressure, while the rotary model pushes hot water through the ground at a high speed. Both machines produce great espresso however rotary machines tend to be more quiet, durable and less likely to fail.
The Boiler
The boiler is the one that makes the water warm to a temperature that is ideal for extraction. The resultant steam then reaches the portafilter containing the ground espresso coffee and is then pumped into the cup. During this process the steam is able to create enough pressure to push the grounds of the coffee through. This results in a whipped-up top of the espresso. This is one of the main characteristics of a great espresso.
There are three types of espresso makers, which differ in the kind of pump they use and how hot the espresso is. There are also different ways that the brew may be controlled as well as the size of the cup the maker can create.
The earliest espresso machines were steam-based. They used one boiler to create both steam and brew however the pressure they were able to create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most popular espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic machine, you must grind the beans and then tamp them by hand, but the pump regulates the flow of water and pressure. This is a great compromise between the human touch and the mechanized quality.
The Filter
Espresso machines usually use filters that separate the grounds of the coffee from hot water. The filter is also an important part of the temperature control system, because it stops the machine from overheating.
A filter also helps with flavor since it allows for an extended flowering time. This allows beans to release their flavor and gives an opportunity for a better extraction.
However, it is important to remember that even a good filter can produce a bad cup of coffee, as the quality of the beans and extraction is important.
This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter, the thingy that you use to put the coffee grounds into, when making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to produce steam. The steam then pushes hot water into the coffee grounds under high pressure. portable espresso machine of machines are typically cheaper and easier to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air pump-driven espresso machines have been gaining popularity. They use an air-compressor to push hot water through the ground and are much more mobile than electric steam-driven espresso machines.