How Does Machine Espresso Work?
Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it that makes it work?
To make an 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 Head of the Group
As the name implies the group head is the place you place your portafilter when making espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are designed for stability in temperature, while others are designed to handle pre-infusion. Others are made to control the lever. There are even some that come with a range of features, such as the E61 one, which is the standard choice for many baristas due to its capacity to offer multiple benefits in one package.
As you can see in the image above, the group head has several notches where you place your portafilter and then twist it with your hands to secure it. There is also a gasket of rubber that resides inside the notches and helps create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact position of the portafilter which is crucial to ensure a consistent extraction.
The group head does not just allow you to place your portafilter easily however, it also keeps the temperature at a constant level. It does this by circulating hot water through the brew basket, and around the portafilter to ensure that it's always at the right temperature for extraction. This is crucial, since even a few degrees can make the difference between a good and great espresso.
The Pump
In contrast to piston machines that are manually operated, which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps to supply the nine atmospheric bars of pressure necessary for espresso extraction. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.
Pumps are generally more affordable and last longer than piston-driven machines. However, both kinds of machines can degrade because of excessive use and poor cleaning. Pumps are also more complicated mechanically, which could increase the price of even the simpler models.
Certain espresso machines eliminate the pump entirely and use steam pressure to brew espresso. The drawback is that the boiler that produces steam also raises the temperature of water until it reaches boiling which could lead to over-extraction. They also have to continually rebuild their pressure between cups. best coffee espresso machine takes energy and time.
Many espresso machines make use of an rotary or vibrating pump, which has a vibration model using a vibrating disc to create the pressure and the rotary model pushing hot water through the grounds under high speed. Both types of machine can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler will heat the water to a temperature that is ideal to extract. The steam that is created reaches the portafilter, which is a container for espresso grounds. It is then poured into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This creates a foam on the top of the espresso. This is a hallmark of a good espresso.
There are three kinds of espresso machines, each having different pumps and brew temperature. There are a variety of ways to control the strength of the brew and the size of the cup that can be produced by the machine.
The first espresso machines were steam-type. The earliest espresso machines were steam types. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic machine, you have to grind the beans and then tamp them by hand. The pump regulates the flow of water and pressure. This is a great combination of human control and mechanized consistency.
The Filter
Typically, espresso machines utilize a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also an important component of the temperature control system as it prevents the machine from overheating.
It also aids in flavor as a filter lets you enjoy a longer bloom phase. This allows the beans to release their flavors and provides an opportunity for a better extraction.
However, it is important to remember that even a good filter can result in a poor cup of coffee, since the quality of the beans and extraction is still essential.
This is where the magic happens. It's what makes espresso taste great. The grouphead (also called the brewhead) is where you put the portafilter, which is the thingy that you use to put the grounds of coffee into when making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight vessel to create steam. The steam then moves hot water through the grounds of the coffee under pressure. These machines are less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air-pump-driven espresso machines have become more popular. They make use of an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven espresso machines.