How Does Machine Espresso Work?
The machine espresso uses precision pressure, and a filtering system that is awe-inspiring to create the coffee you enjoy. What exactly does it work?
In order 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 primary difference.
The Head of the Group
The group head is the portafilter that you put in when making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are several different types of group heads, each with their distinct advantages and drawbacks. Some are focused on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. There are also some that have a combination of features, like the E61 one, which is the classic choice among many baristas due to its ability to offer multiple perks in one package.
As you can see in the picture above the head of the group is fitted with a variety of notches. You can place your portafilter inside these notches, and then turn the head around to secure it. There is also a gasket made of rubber in the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of the portafilter. This is crucial for a consistent extraction.
In addition to allowing you to effortlessly insert your portafilter the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket, and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is vital, because just a few degrees could mean the difference between 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 for espresso extraction. This differs from manual piston machines that rely on a lever. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are typically less expensive than piston-driven models, and they tend to last longer, but both types of machines may degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which can raise the cost of even simpler models.
Some espresso machines can eliminate the pump entirely and use steam pressure to brew espresso. This can lead to over-extraction as the boiler that makes steam also causes the water to boil. Additionally these machines are often required to restore their pressure between cups, which requires time and energy.
A majority of espresso machines utilize a rotary or vibration pump. A vibration model uses the vibrating disk to create pressure, while a circular model pushes hot liquid through the ground at a rapid speed. Both types of machines can make a great espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what makes the water warm to a temperature that is ideal to extract. The resulting steam reaches the portafilter which holds the ground espresso coffee, and gets funnelled down into the cup. During this process the steam is able to create enough pressure to push the grounds of the coffee through. This results in a layer of crema that is then poured over. This is a sign of a good espresso.
There are three kinds of espresso machines, each having distinct pumps and the temperature of the brew. There are different ways to control the brew as well as the size of the cup that can be made by the machine.
The first espresso machines were steam-type. The first espresso machines were steam-type machines. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso machine is a semiautomatic one with an electric pump. These are what people imagine when they coffee for espresso machine think of an espresso maker. 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 an excellent compromise between human touch and mechanized accuracy.
The Filter
Typically, espresso machines have filters that separate the grounds of the coffee as they go through the hot water. The filter is also a vital part of the machine's temperature control, since it helps to prevent overheating.
A filter also helps with flavor because it allows for a longer flowering phase. This helps the beans release their flavors and provides an opportunity for better extraction.
However, it is important to remember that even a good filter can result in a poor cup of coffee, as the quality of the beans and extraction are important.
It's in this area that the magic happens. This is what makes espresso taste so delicious. The grouphead, sometimes referred to as the brew head, is where the portafilter (the device you put the coffee grounds into) is placed when you're making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to make steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. However, they are limited in their ability to produce the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.
In recent years, compressed air pump-driven espresso machines have been gaining popularity. They use an air compressor to push hot water through the grounds and are significantly more portable than steam-driven electric machines.