How Does Machine Espresso Work?
Machine espresso uses precision pressure and mind-blowing filter technology to create the perfect cup of coffee. What exactly does it work?
Espresso is created by forcing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee. However the pressure is the main 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 before controlling the pressure that results from the extraction. There are various kinds of group heads each with its unique advantages and drawbacks. Some are designed to provide the stability of temperature while some are built to handle pre-infusion. Some are designed to control the lever. Some have a combination, like the E61. This is a popular choice among baristas due to the fact that it has multiple advantages in one package.
As you can see from the picture above, the group head has a number of notches. You place your portafilter inside these notches, and then twist the head to lock it. A rubber gasket is located inside the notches to help create a seal when you insert your portafilter. The notches on the head allow for an exact position of the portafilter which is essential to ensure a consistent extraction.
In addition to allowing you to easily connect your portafilter, the group head is also responsible to ensure that the temperature remains even. It does this by cycling hot water through the brew container and around the portafilter, making sure that it's always at the right temperature to extract. It is important to realize that even a tiny differences can make the distinction between a good and a great espresso.
The Pump
Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines that rely on a lever. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pumped through the ground coffee inside the group head.
Pumps are generally cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade because of excessive use and insufficient cleaning. They also create mechanical complexity which can result in the cost of even the most basic models.
Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. This can result in over-extraction because the boiler that makes steam also causes the water to boil. The machines also need to continually rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of the rotary or vibration pump. A vibration model makes use of an oscillating disk to create pressure, while the rotating model pushes hot water through the ground at a high speed. Both types of machine can make excellent espresso, but Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the one that makes the water warm to a temperature that is ideal to extract. The steam that is created is then directed to the portafilter, which holds the espresso grounds. The steam is then channeled into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This results in a crema on top of the espresso. This is one of the main characteristics of a good espresso.
There are three distinct types of espresso machines, each with different pumps and brew temperature. There are many ways to control click here the strength of the brew and the size of cup that can be produced by the machine.
The earliest espresso machines were steam-based. They had only one boiler to make steam and brew, however, the pressure they could produce was not very high - two bars of atmospheric pressure at the most. This resulted in the coffee tasting burnt and bitter. 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. These are the images people have when they think of an espresso maker. If you have a semi-automatic machine you grind the beans and tamp them by hand. However, the pump controls the flow of water and pressure. This is a fantastic compromise between human control and mechanized consistency.
The Filter
Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also a vital element of the machine's temperature control, as it helps prevent overheating.
A filter can also help with flavor, as it permits a longer flowering phase. This lets the beans release their flavors, and improves extraction.
However it is crucial to keep in mind that even a high-quality filter can produce a bad cup of coffee, as the quality of the beans and extraction is crucial.
It's in this area that the magic happens. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you place the portafilter, which is the thingy that you put the coffee grounds in, when making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight container to produce steam. The steam then pushes hot water through the grounds of the coffee under pressure. These types of machines are typically less expensive and simpler to maintain than pump-driven models. They are however limited in their ability for creating the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, compressed air pump-driven espresso machines have become more popular. They utilize an air compressor to push hot water through the ground, and are more mobile than electric steam-driven espresso machines.