How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to make the perfect cup of coffee. How does it work exactly?
To make 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 Head of the Group
As the name suggests, the group head is the place you place your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the extraction. There are a variety of types of group head each with its distinct advantages and disadvantages. Some are focused on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. Some have a combination, like the E61. This is a popular choice among baristas due to the fact that it has multiple benefits in a single package.
As you can see in the above image The group head features several notches to place your portafilter before twisting it by hand to lock it in. There is also a gasket made from rubber which is located inside the notches, which helps create a seal when you insert your portafilter into the machine. The notches on the head permit an exact placement of the portafilter, which is necessary to ensure an efficient extraction.
The group head not only lets you to insert your portafilter easily, but it also maintains the temperature at a constant level. It does this by circulating hot water through the brew container and around the portafilter, making sure that it’s always at the right temperature to extract. It is important to realize that even a few degree differences can make the distinction between a good and a excellent espresso.
The Pump
The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure that is required for espresso extraction. This differs from manual piston machines that rely on a lever. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are generally cheaper and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading because of frequent use and poor cleaning. Pumps are also more complex mechanically, and can add to the cost of even most basic models.
Certain espresso machines remove the pump completely and instead use steam pressure to brew espresso. This can cause over-extraction because the boiler that makes steam also causes the water to boil. Additionally, these machines frequently have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines use the rotary or vibration pump. A vibration model uses a rotating disk to generate pressure, while the rotary model pushes hot water through the best ground coffee for espresso machine at a fast speed. Both models can make a great espresso, however the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is what will heat the water to a temperature that is ideal to extract. The resulting steam is then transferred to the portafilter which holds ground espresso beans and is then pumped into the cup. The steam creates pressure that pushes through the grounds of the coffee. This results in a layer crema on top. This is a sign of a good espresso.
There are three kinds of espresso makers, which differ in the type of pump they employ and the degree of heat that the brew is. There are also different ways that the brew can be controlled as well as the size of the cup that the machine can make.
The earliest espresso machines were steam types. They utilized one boiler to create both steam and brew however the pressure they were able to create was minimal – two bars of atmospheric pressure at the most. This led to the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they imagine these machines. With a semi-automatic machine you grind the beans and then tamp them by hand. The pump provides regulated water flow and pressure. This is a great compromise between the human touch and mechanized consistency.
The Filter
Espresso machines typically have filters that separate the grounds of coffee from hot water. The filter is also an essential element of the temperature control system, because it stops the machine from overheating.
It also helps with flavor, since a filter allows for a longer bloom time. This helps the beans to let their nuances out and provides an opportunity for better extraction.
However, it is important to remember that even a great filter can produce a bad cup of coffee, because the quality of the beans and extraction is still important.
This is where the magic happens. It’s what makes an espresso really taste great. The grouphead, often called the brewhead, is where the portafilter (the thingy you put the ground coffee into) sits 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 coffee grounds under high pressure. These machines espresso are less expensive and easier for the owner to maintain than pumps-driven models. However, they are limited in their ability to produce the perfect conditions for brewing, because they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars.
In recent years, espresso machines driven 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 coffee machine for home machines.