How Does Machine Espresso Work?
The machine espresso is made using precise pressure and filtering technology that is amazing to create the coffee you enjoy. How does it work exactly?
Espresso is produced by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.
The Group Head
As the name suggests, the group head is the place you insert your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure that results from the extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion features, and others are designed to control the lever. Some come with a combination of both, such as the E61. This is a popular choice among baristas as it provides a variety of advantages in a single package.
As you can see in the image above the group head comes with several notches where you place your portafilter and then twist it with your hands to lock it in. A rubber gasket is located inside the notches, which helps create a seal while you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is essential for an efficient extraction.
In addition to allowing you effortlessly insert 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 always at the right level to extract the coffee. It is important to realize that even a slight differences can make the distinction between a good and a great espresso.
The Pump
Contrary to manual piston machines which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to provide the nine atmospheric bars of pressure required for espresso extraction. The pressure is created by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be less expensive than piston-driven models, and they tend to last longer, but both types of machines can degrade with overuse and insufficient cleaning. They also add mechanical complexity, which can result in the cost of even the most basic models.
Some espresso machines make use of steam pressure instead of a pump to make espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of the water to the point of boiling which could lead to over-extraction. These machines also have to continuously rebuild their pressure between cups. This requires energy and time.
Many espresso machines use the rotary or vibration pump. A vibration model uses a vibrating disk to generate pressure, whereas the rotating model pushes hot water through the ground at a high speed. Both machines produce great espresso, but rotary machines are quieter, more durable and less likely to break down.
The Boiler
The boiler is what makes the water warm to the right temperature to extract. The resulting steam is then transferred to the portafilter which holds ground espresso beans and is then pumped into the cup. During this process, steam causes pressure to push through the coffee grounds. This results in a layer crema on top. This is one of the main characteristics of a good espresso.
There are three types of espresso machines, each having a different type of pump and brew temperature. There are various ways that the brew may be controlled as well as the size of the cup that the machine is capable of making.
The earliest espresso machines were steam type. espresso coffee machine were steam types. This led to the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso maker is a semi-automatic machine that has an electric pump. This is what people envision when they think of an espresso machine. 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 solution that combines human control with mechanized accuracy.
The Filter
Espresso machines usually use filters that separate the grounds of the coffee from hot water. The filter is also an essential element of the temperature control system as it prevents the machine from overheating.
Filters also aid in flavor since it allows for a longer flowering phase. This allows the beans to let their nuances out, and also allows for better extraction.
However, it is important to remember that even a high-quality filter could result in a bad cup of coffee as the quality of the beans and extraction is still important.
This is where the magic happens, it's the thing that makes espresso taste great. The grouphead, sometimes called the brewhead, is where the portafilter (the thingy you put the coffee ground into) is placed when making espresso.
In the steam-driven espresso machine hot water is heated in an airtight container to create steam, which then pushes the hot water through the grounds under high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. They are however limited to create the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to push hot water through the ground. They are also more mobile than steam-driven electric espresso machines.