How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to make the coffee we love. What exactly is it that makes it work?
To make 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
As the name implies, the group head is where you put your portafilter in when brewing espresso. It is responsible for dispersing water into the portafilter and espressomachines then controlling the pressure of the resulting extraction. There are many different kinds of group heads, each with their unique advantages and drawbacks. Some are designed to provide temperature stability while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some have a combination, such as the E61. This is a very popular choice for baristas as it provides a variety of advantages in one package.
As you can see in the picture above, the group head is equipped with several notches. It is possible to place your portafilter in these notches and then twist the head to lock it. There is also a gasket of rubber that is a part of the notches and helps create a seal when you insert your portafilter into the machine. The notches allow for the precise placement of the portafilter. This is vital for an efficient extraction.
Apart from allowing you easily connect your portafilter, the group head is also responsible for maintaining an even temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level for extraction. It is important to realize that even a slight deviation can make the difference between a good and excellent travel espresso maker.
The Pump
The motorized pumps used in espresso machines that rotate provide the nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines which use levers. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee inside the group head.
Pumps are typically less expensive than piston-driven machines, and they tend to last longer, however both types of machines may become damaged due to excessive use and poor cleaning. They also add mechanical complexity which can result in an expensive price for even the simplest models.
Some espresso machines eliminate the pump completely and make use of steam pressure to make espresso. The drawback is that the boiler that produces steam also raises the temperature of water to the point of boiling which could lead to excessive extraction. Additionally, these machines frequently have to restore their pressure between cups, which requires time and energy.
A majority of espresso machines utilize an rotary or a vibration pump. A vibration model makes use of an oscillating disk to create pressure, whereas the rotary model pushes hot water through the ground at a high speed. Both types of machines can produce an excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the component that heats water to an optimal temperature for extraction. The steam produced is then directed to the portafilter, which holds the espresso grounds. The steam is then channeled into the cup. During this process, the steam creates pressure to push 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 machines, each with a different type of pump and the temperature of the brew. There are different ways that the brew can be controlled, as well as the dimensions of the cup the machine can make.
The first espresso machines were steam type. They employed one boiler to make both brew and steam, however, the pressure they could create was minimal – two bars of atmospheric pressure maximum. This led to the coffee tasting burnt and bitter. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most commonly used espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine, you must grind the beans and tamp them by hand. However, the pump controls the flow of water and pressure. This is an excellent combination of human control and mechanised reliability.
The Filter
Typically, espresso machines have a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also an important part of the temperature control system, since it helps prevent the machine from overheating.
It also improves flavor, as it lets you enjoy a longer bloom time. This allows the beans to release their nuances, and improves extraction.
It is important to remember that even the best filter could result in a poor cup of coffee. The quality of the beans, and the extraction, remain vital.
This is where the magic happens. It’s what makes espresso taste good. The grouphead (also known as the brewhead) is where you put the portafilter, the device used to place the coffee grounds in, while making espresso.
In a steam-driven espresso machine hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds with high pressure. These types of machines tend to be less expensive and simpler to maintain than pump-driven models. However, they are limited in their capacity to create the perfect conditions for brewing, as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.
In recent years, compressed air-driven espresso machines have been gaining popularity. They use an air compressor to force hot water into the ground, and are more mobile than electric steam-driven espresso machines.