How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and mind-blowing filter technology to create the perfect cup of coffee. What exactly does it work?
To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.
The Group Head
As the name implies, the group head is where you insert your portafilter when brewing espresso. It distributes water into the portafilter, and then regulates the pressure of the extraction. There are various kinds of group heads, each with their own advantages and disadvantages. Some focus on temperature stability, some on pre-infusion features, and others are designed to control the lever. Some come with a combination of both, such as the E61. This is a very popular choice for baristas due to the fact that it has multiple advantages in a single package.
As you can see in the above photo the group head is made up of many notches in which you can put your portafilter, then twist it with your hands to lock it in. A gasket made of rubber is placed inside the notches, which helps create a seal while you insert your portafilter. The notches allow for precise placement of your portafilter. This is vital for an even extraction.
The group head not only allows you to insert your portafilter easily however it also keeps the temperature at a constant level. This is accomplished by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is constant to extract the coffee. This is important because even a small difference in temperature can make the difference between a excellent and great espresso.
The Pump
Contrary to manual piston machines that use a lever to pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure necessary to extract espresso. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be more affordable and last longer than piston-driven machines. However, espresso machine uk of machines can degrade because of excessive use and insufficient cleaning. They also make mechanically complex, which can result in costly prices for even the simplest models.
Some espresso machines eliminate the pump entirely and use steam pressure to brew espresso. This could lead to over-extraction since the boiler that produces steam also heats the water until it comes to a boil. The machines also need to continually rebuild their pressure between cups. This requires energy and time.
Many espresso machines utilize a vibration or rotary pump, with a vibrating model that uses a vibrating disc to generate the pressure and a rotary model pushing hot water through the grounds under high speed. Both models can produce an excellent espresso, but Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats the water to the optimal temperature for extraction. The steam that is produced reaches the portafilter that contains the ground espresso and gets funnelled down into the cup. During this process the steam causes enough pressure to push the grounds of coffee through. This creates a layer crema on top. This is one of the hallmarks of a great espresso.
There are three distinct types of espresso machines, each having different pumps and brew temperature. There are various ways that the brew may be controlled and the dimensions of the cup the machine can produce.
The first espresso machines were steam-types. The earliest espresso machines were steam types. The coffee tasted bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular espresso machine is a semiautomatic that has an electric pump. These are the images people have when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own The pump, however, regulates the flow of water and pressure. This is a great compromise between the human touch and the mechanized accuracy.
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 an essential element of the machine's temperature control, as it prevents overheating.
It also enhances flavor, as a filter lets you enjoy a longer bloom phase. This allows beans to release their flavors and provides an opportunity to improve extraction.
However it is crucial to remember that even a high-quality filter can produce a bad cup of coffee, because the quality of the beans and extraction is still vital.
This is where the magic happens. It's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you put the portafilter - the thingy that you use to put the coffee grounds into, while making espresso.
Steam-driven espresso machines use hot water heated in an airtight container to produce steam. The steam then pushes hot water through the coffee grounds under high pressure. These machines are cheaper and easier for the user 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 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 steam-driven electric espresso machines.