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How Does Machine Espresso Work?
The machine espresso uses precise pressure and filter technology that is awe-inspiring to make 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 making drip coffee, but the major difference is in the pressure.
The Group Head
The name implies the group head is where you place your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are many different kinds of group head, each with their own advantages and disadvantages. Some are designed for stability of temperature while others are designed to handle pre-infusion. Others are made to control the lever. Some have a combination, like the E61. This is a favorite among baristas as it provides a variety of advantages in one package.
As you can see from the photo above, the group head is equipped with several notches. The portafilter is placed inside these notches, and then twist the head to lock it. There is also a gasket made from rubber that resides inside the notches to help create a seal when you insert your portafilter into the machine. The notches permit precise placement of the portafilter. This is crucial for an even extraction.
The group head not only allows you to insert your portafilter easily but also maintains a constant temperature. This is accomplished by cycling hot water around the portafilter and through the brew basin, ensuring the temperature is always right for extraction. This is important, as even a few degrees can mean the difference between excellent and great espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure that are required to extract espresso. 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 machines and tend to last longer, although both types of machine can be damaged by excessive use and inadequate cleaning. They also increase the complexity of mechanical systems which can result in costly prices for even the most basic models.
Some espresso machines employ steam pressure instead of a pump to brew espresso. This could lead to over-extraction since the boiler that produces steam also warms the water to boil. The machines also need to constantly rebuild their pressure between cups. This takes energy and time.
Many espresso machines use either a vibration or rotary pump. A vibration model utilizes an oscillating disk to create pressure, while the circular model pushes hot liquid through the ground at a rapid speed. Both types of machines are capable of producing excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats water to the optimal temperature to extract. The resulting steam reaches the portafilter containing the ground espresso coffee and gets funnelled down into the cup. The steam causes pressure to push through the coffee grounds. This creates a layer crema that is then poured over. espresso machine uk is one of the hallmarks of a great espresso.
There are three different types of espresso machines, each having a different type of pump and the temperature of the brew. There are various ways to control the brew and the size of the cup that can be made by the machine.
The first espresso machines were steam types. They utilized a single boiler to make steam and brew, however the pressure they were able to create was minimal - two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most commonly used espresso machine is a semiautomatic model with an electric pump. These are what people imagine when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a great combination of human control and mechanised reliability.
The Filter
Espresso machines typically use filters that separate the coffee grounds from the hot water. The filter is also a vital component of the machine's temperature control, as it prevents overheating.
It also improves flavor, since a filter allows for a more prolonged bloom time. This helps the beans to release their flavors and provides an opportunity to improve extraction.
However it is crucial to remember that even a great filter can produce a bad cup of coffee, because the quality of the beans and extraction is crucial.
This is where the magic happens. It's what makes espresso taste great. The grouphead, often referred to as the brewhead, is where the portafilter (the thingy you put the coffee ground into) is placed when making espresso.
In a steam-driven espresso machine hot water is heated in an airtight tank to create steam, which then pushes the hot water through the grounds under high pressure. These kinds of machines are typically cheaper and easier to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the ideal conditions for brewing because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.
In recent years, espresso machines driven by a compressed air compressor have become increasingly popular. They use an air compressor to force hot water through the ground, and are more mobile than steam-driven electric espresso machines.