How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and amazing filter technology to make the perfect cup of coffee. What exactly is it?
Espresso is made by forcing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the primary difference.
The Group Head
As the name suggests, the group head is where you put your portafilter in 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 types of group heads each with its particular advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. Some come with a range of features, such as the E61 one, which is the most popular choice among baristas due to its capacity to offer multiple benefits in a single package.
As you can see from the picture above the head of the group is equipped with several notches. You place your portafilter in these notches and then twist the head to secure it. A gasket made of rubber is positioned inside the notches to help create a seal while you insert your portafilter. The notches allow for the precise placement of the portafilter. This is vital for an efficient extraction.
In addition to allowing you easily insert your portafilter, the group head is responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure the temperature is always right for extraction. This is important, as even a few degrees can be the difference between a excellent and great espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, the rotary
uk espresso machine machines use motorized pumps that provide the nine atmospheric bars of pressure required for espresso extraction. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.
Pumps are generally less expensive and last for longer than piston-driven machines. However, both types of machines are susceptible to degrading because of excessive use and inadequate cleaning. They also create mechanical complexity and can lead to a high price tag on even the most basic models.
Some espresso machines employ steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since the boiler that makes steam also heats the water to boil. They also have to constantly rebuild their pressure in between cups. This requires energy and time.
A majority of espresso machines use a vibration or rotary pump, which has a vibration model using a rotating disc that generates the pressure, and the rotary model pushing hot water through the grounds at high speed. Both machines produce great
espresso coffee machines uk however rotary machines tend to be more stable, quieter and less likely to break.
The Boiler
The boiler is the element that heats water to an ideal temperature to extract. The resulting steam is then transferred to the portafilter that contains ground espresso beans and gets funnelled down into the cup. During this process, the steam causes pressure to push through the grounds of the coffee. This creates a foam on top of the espresso. This is the hallmark of a good espresso.
There are three kinds of espresso machines, each with distinct pumps and brew temperature. There are also different ways that the brew can be controlled and the size of the cup that the maker can create.
The first espresso machines were steam-type. They employed one boiler to make both steam and brew however the pressure they were able to produce was not very
high end espresso machine - two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most popular
espresso machine with milk frother machine is a semiautomatic one 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 yourself, but the pump regulates the flow of water and pressure. This is a great solution that combines human control with mechanised reliability.
The Filter
Espresso machines typically use a filter that separates the grounds of the coffee from hot water. The filter is also a vital element of the machine's temperature control, since it stops overheating.
A filter can also help with flavor, as it permits a longer flowering period. This helps the beans to let their nuances out and provides an opportunity for better extraction.
It is important to remember that even the best filter could result in a poor cup of coffee. The quality of the beans and the extraction, remain vital.
This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter, the thingy used to place the coffee grounds in, while making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds at high pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing 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 use an air compressor to push the hot water through the grounds, and are far more portable than electric steam-driven machines.
