How Does Machine Espresso Work?
Machine espresso uses precision pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly does it work?
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 Head of the Group
The group head is the portafilter that you put in when making espresso. It disperses the water into the portafilter and regulates the pressure during the extraction. There are numerous kinds of group heads, each with its own advantages and drawbacks. Some are designed to provide stability of temperature while others are designed to handle pre-infusion. Some are designed to control the lever. Some include a combination like the E61. This is a popular choice among baristas since it provides multiple benefits in one package.
As you can see in the above photo the group head is fitted with a variety of notches. The portafilter is placed in these notches, then turn the head around to secure it. A rubber gasket is located inside the notches to help create a seal while you insert your portafilter. The notches on the head permit a precise location of the portafilter which is vital for an even extraction.
In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew container and around the portafilter, making sure that it is always at the right temperature for extraction. It is important to realize that even a few degree difference can make the difference between a good and a excellent espresso.
The Pump
The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines which use levers. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger prior to being shot through the ground coffee inside the group head.
Pumps tend to be cheaper and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and poor cleaning. Pumps are also more complex mechanically, which can raise the cost of even simplest models.
Certain espresso machines can eliminate the pump entirely and employ steam pressure to create espresso. This can lead to over-extraction as the boiler that makes steam also heats the water until it comes to a boil. In addition the machines often have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines use the rotary or vibration pump. A vibration model employs a rotating disk to generate pressure, whereas a circular model pushes hot liquid through the ground at a high speed. espresso coffee machines of machine can produce an excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the one that heats the water to the right temperature to extract. The steam produced reaches the portafilter, which holds the espresso grounds. It is then poured into the cup. The steam creates pressure that pushes through the coffee grounds. This creates a crema on the top of the espresso. This is a hallmark of a great espresso.
There are three different types of espresso machines, each with distinct pumps and brew temperature. There are also different ways that the brew can be controlled as well as the size of the cup the machine can produce.
The first espresso machines were steam-based. The first espresso machines were steam types. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they think of these machines. Semi-automatic machines require you to grind and tamp your beans yourself while the pump controls the water flow and pressure. This is an excellent compromise between human touch and the mechanized accuracy.
The Filter
Typically, espresso machines employ filters to separate the grounds of coffee as they move through the hot water. The filter is also a crucial element of the temperature control system, as it keeps the machine from overheating.
It also helps with flavor, as a filter allows for a longer bloom time. This lets the beans let their nuances out, and improves extraction.
However it is crucial to remember that even a great filter can make a terrible cup of coffee, as the quality of the beans and extraction is still important.
This is where the magic happens, it's what makes espresso taste great. The grouphead (also known as the brewhead) is where you put the portafilter, the device which you put the coffee grounds into, while 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 grounds of coffee at high pressure. These kinds of machines tend to be less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, compressed-air-pump-driven espresso machines have become more popular. They use an air compressor to push hot water through the grounds and are more portable than steam-driven electric machines.