How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to create the perfect cup of coffee. 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 major difference.
The Group Head
As the name suggests the group head is where you put your portafilter in when brewing espresso. It disperses water into the portafilter, and regulates the pressure during the extraction. There are many different types of group heads each with their own advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. There are also some that contain a variety of features, such as the E61 one, which is the classic choice among many baristas for its ability to provide multiple benefits in a single package.
As you can see from the above photo the head of the group is equipped with several notches. You can place your portafilter inside these notches, and then twist the head to secure it. A gasket made of rubber is positioned inside the notches, which helps make a seal when you insert your portafilter. The notches permit precise placement of the portafilter. This is crucial to ensure a consistent extraction.
Apart from allowing you easily insert your portafilter, the group head is responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is constant to extract the coffee. It is important to remember that even a few degree difference can make the difference between a good and excellent espresso.
The Pump
Motorized pumps in professional espresso machine machines rotary provide nine atmospheric bars of pressure required for espresso extraction. This differs from manually operated piston machines that employ levers. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are generally less expensive than piston-driven models, and they tend to last longer, but both types of machine can become damaged due to excessive use and poor cleaning. They also create mechanical complexity that can lead to an expensive price for even the most basic models.
Some espresso machines make use of steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since the boiler that makes steam also warms the water to boil. Additionally, these machines frequently have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines make use of a vibration or rotary pump, which is a vibration model using a rotating disc to generate the pressure, and the rotary model pushing hot water through the grounds at high speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to fail.
The Boiler
The boiler will heat the water to the ideal temperature to extract. The resulting steam is then transferred to the portafilter containing the ground italian espresso machines (made my day) coffee and is then pumped into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This produces a layer of crema on top. This is one of the main characteristics of a good espresso.
There are three types of espresso makers. They differ in the kind of pump they use and the degree of heat that the brew is. There are various 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 had one boiler to make steam and brew, however the pressure they were able to generate was low – only two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most common espresso machine is a semiautomatic model 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, but the pump regulates the flow of water and pressure. This is a great compromise between the human touch and the mechanised accuracy.
The Filter
Typically, espresso machines use a filter to separate out the coffee grounds as they pass through the hot water. The filter is also a crucial element of the temperature control system, as it prevents the machine from overheating.
It also helps with flavor, as it can allow for a longer bloom time. This lets the beans let their nuances out, and also allows for better extraction.
However it is crucial to remember that even a good filter could result in a bad cup of coffee, since the quality of the beans and extraction is essential.
This is where the magic happens, and it’s what makes espresso taste great. The grouphead, also referred to as the brew head, is the place where the portafilter (the thing you put the coffee ground into) is placed when making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to create steam. The steam then pushes hot water through grounds of coffee at high pressure. These types of machines are typically cheaper and easier to maintain than pump-driven models. They are however limited in their ability for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air-compressor to push hot water through the ground. They are also more mobile than steam-driven electric espresso machines.