How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and a filter technology that is mind-blowing to create the coffee you enjoy. What exactly does it work?
Espresso is made by forcing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee. However the pressure is the main difference.
The Group Head
The group head is the portafilter that you put in when making espresso. It disperses water into the portafilter, and controls the pressure of the extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are specifically designed for temperature stability while others are specifically designed to handle pre-infusion. Others are made to control the lever. Some come with a range of features, such as the E61 one, which is the classic choice among many baristas due to its ability to provide multiple benefits in a single package.
As you can see in the above image The group head features numerous notches that you can put your portafilter, then twist it with your hands to secure it. There is also a gasket made of rubber that resides inside the notches to help create a seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is essential for a consistent extraction.
Aside from allowing you to easily place your portafilter in, the group head is responsible to ensure that the temperature remains even. This is done by cycling hot water around the portafilter, and through the brew-basket, making sure the temperature is always right for extraction. This is important because even a few degrees can be the difference between a good and great espresso.
The Pump
Unlike manual piston machines, which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure that are required to extract professional espresso machine for home. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be less expensive and last longer than piston-driven machines. However, both types of machines are susceptible to degrading because of excessive use and insufficient cleaning. They also add mechanical complexity which can result in costly prices for even the simplest models.
Some espresso machines make use of steam pressure instead of a pump to brew espresso. The downside is that the same boiler that produces steam also increases the temperature of the water to boiling, which can lead to over-extraction. In addition the machines often have to restore their pressure between cups, which requires time and energy.
Many espresso machines employ the rotary or vibration pump, with a vibration model using a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds at high speed. Both machines can produce excellent espresso, however rotary machines are more stable, quieter and less likely to break.
The Boiler
The boiler is the one that will heat the water to a temperature that is ideal to extract. The steam that is produced reaches the portafilter, which contains the ground espresso coffee and is then pumped down into the cup. During this process, the steam creates pressure that pushes through the coffee grounds. This produces a layer of crema that is then poured over. This is one of the main characteristics of a great espresso.
There are three kinds of espresso makers, which differ in the kind of pump they use and how hot the coffee is. There are many ways to control the strength of the brew and the size of cup that can be made by the machine.
The first espresso machines were steam-types. They utilized one boiler to make both steam and brew however, the pressure they could create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burned. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most well-known espresso maker is a semi-automatic machine with an electric pump. These are what people imagine when they think of an espresso maker. If you have a semi-automatic machine you must grind the beans and tamp them yourself but the pump controls the flow of water and pressure. This is a fantastic solution that combines human control with mechanised accuracy.
The Filter
Beko CEP5152B Espresso Machine - 15 Bar Black machines usually have a filter that separates the coffee grounds from the hot water. The filter is also an essential element of the temperature control system as it prevents the machine from overheating.
It also helps with flavor as a filter can allow for a longer bloom phase. This lets the beans release their nuances, and improves extraction.
It is important to remember that even the best filter can make a bad cup of coffee. The quality of the beans, and the extraction process, remain vital.
It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead, often referred to as the brew head, is where the portafilter (the thing you put the ground coffee into) is located when you're making espresso.
Steam-driven espresso machines make use of hot water heated in an airtight container to make steam. The steam then pushes hot water into the grounds of the coffee under pressure. These types of machines are generally less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to create the perfect conditions for brewing, as they only operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They use an air compressor to force the hot water through the grounds and are significantly more portable than electric steam-driven machines.