How Does Machine Espresso Work?
The machine espresso is made using precise pressure and filter technology that is awe-inspiring to make the coffee you love. But how exactly does it work?
To make an espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.
The Head of the Group
The name implies the group head is where you put your portafilter in when making espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are many different types of group heads each with its own advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. There are also some that contain a variety of features, like the E61 one, which is the most popular choice among baristas for its ability to offer multiple perks in one package.
As you can see in the image above, the group head has several notches where you place your portafilter before twisting it manually to secure it. A rubber gasket is located in the notches to create a seal as you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial to ensure an even extraction.
The group head is not just able to allow the portafilter to be inserted easily but also maintains a constant temperature. It does this by circulating hot water through the brew pan and around the portafilter, making sure that it is always at the correct temperature to extract. This is vital, because even a small difference in temperature can make the difference between a good and excellent espresso.
The Pump
The motorized pumps that are used in espresso machines that rotate provide the nine atmospheric bars of 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 before being pushed through the ground coffee in the group head.
Pumps are generally less expensive than piston-driven machines, and tend to last longer, although both types of machine can degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which can increase prices of even most basic models.
Some espresso machines use steam pressure instead of a pump for brewing espresso. The drawback of this is that the boiler that produces steam also increases the temperature of the water until it reaches boiling which could lead to over-extraction. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines make use of the rotary or vibration pump. A vibration model uses an oscillating disk to create pressure, whereas the Rotary model pushes hot coffee through the ground at a high speed. Both types of machines are capable of producing excellent espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is what makes the water warm to the ideal temperature for extraction. The steam that is created reaches the portafilter, which is a container for espresso grounds. The steam is then channeled into the cup. During this process, the steam creates pressure that pushes through the grounds of the coffee. This results in a whipped-up the top of the espresso. This is a hallmark of a great espresso.
There are three kinds of espresso makers. They differ in the kind of pump they use and the degree of heat that the espresso is. There are a variety of ways to control the brew and the size of cup that can be made by the machine.
The earliest espresso machines were steam types. They employed a single boiler to make both brew and steam, however the pressure they were able to produce was not very high - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the flow of water and pressure. This is a perfect combination of human control and mechanised reliability.
The Filter
Typically, espresso machines employ a filter to separate out the coffee grounds as they pass through the hot water. The filter is also a vital element of the machine's temperature control, as it helps prevent overheating.
Filters also aid in flavor because it allows for a longer flowering phase. Coffeee helps the beans to release their nuances and gives an opportunity to improve extraction.
However it is crucial to remember that even a top filter can result in a poor cup of coffee as the quality of the beans and extraction is vital.
It's in this area that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you put the portafilter - the thingy that you put the coffee grounds into, when making espresso.
Steam-driven espresso machines use hot water heated in an airtight vessel to create steam. The steam then moves hot water through the grounds of the coffee under pressure. These kinds of machines tend to be less expensive and simpler to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect conditions for brewing, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.
In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They use an air compressor to force hot water through grounds, and are far more portable than electric steam-driven machines.