How Does Machine Espresso Work?
The machine espresso makes use of precise pressure and filter technology that is awe-inspiring to create the coffee you love. How exactly does it work?
Espresso is made by forcing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.
The Head of the Group
The group head is the portafilter you insert when brewing espresso. It distributes water into the portafilter and controls the pressure of the extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are designed to provide temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. Some come with a combination of both, like the E61. This is a favorite among baristas due to the fact that it has multiple advantages in one package.
As you can see in the above image the group head is made up of several notches to place your portafilter and then twist it with your hands to secure it. There is also a gasket of rubber in the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches permit an exact placement of the portafilter. This is essential for a consistent extraction.
The group head does not just allow you to put in your portafilter easily but also maintains the same temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, making sure that the temperature is at the right level to extract the coffee. This is important, as even a small difference in temperature can mean the difference between good and excellent espresso.
The Pump
The motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure needed for espresso extraction. This differs from manually operated piston machines that employ a lever. The pressure is built 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. However, both types of machines could become damaged due to excessive use and poor cleaning. They also add mechanical complexity which can result in costly prices for even the most basic models.
Some espresso machines use steam pressure instead of a pump in order to brew espresso. This can cause over-extraction because the boiler that makes steam also causes the water to boil. They also have to continually rebuild their pressure between cups. This requires energy and time.
Many espresso machines make use of either a vibration or rotary pump. A vibration model utilizes a vibrating disk to generate pressure, while a rotary model pushes hot water through the ground at a fast speed. Both types of machine can make a great espresso, but the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to an optimal temperature to extract. The steam that is produced reaches the portafilter, which contains the espresso coffee grounds. The steam is then channeled into the cup. During this process, the steam causes pressure to push through the coffee grounds. This results in a layer crema on top. This is a sign of a good espresso.
There are three kinds of espresso makers. They differ in the kind of pump they use and how hot the brew is. There are a variety of ways to control the strength of the brew and the size of cup that can be produced by the machine.
The first espresso machines were steam-types. The first espresso machines were steam types. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they think of these machines. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the water flow and pressure. This is a perfect combination of human control and mechanized accuracy.
The Filter
Espresso machines typically have a filter that separates the grounds of the coffee from hot water. The filter is also an important component of the temperature control system, because it stops the machine from overheating.
A filter also helps with flavor as it allows for a longer flowering period. This allows the beans to release their flavors, and also allows for better extraction.
It is important to keep in mind that even the best filter can produce a bad cup of coffee. The quality of the beans as well as the extraction, remain vital.
It's in this area that the magic happens. This is what makes espresso taste so delicious. espresso coffee machines (also known as the brewhead) is where you put the portafilter - the thingy that you use to put the coffee grounds into, while making espresso.
Steam-driven espresso machines use hot water heated in an airtight container to create steam. The steam then pushes hot water into the grounds of coffee at high pressure. These types of machines tend to be less expensive and simpler to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing as they only 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 utilize an air compressor to push hot water through grounds and are significantly more portable than electric steam-driven machines.