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How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and incredible filter technology to produce the coffee we love. But how exactly does it work?
To make espresso, hot water is pushed under 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 group head is the portafilter you insert when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure that results from the extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some are designed for stability in temperature, while others are built to handle pre-infusion. Others are built to control the lever. espresso coffee machines come with a combination of both, such as the E61. This is a favorite among baristas as it provides a variety of advantages in one package.
As you can see from the picture above the group head is fitted with a variety of notches. It is possible to place your portafilter into these notches and twist the head to lock it. There is also a gasket made from rubber that is a part of the notches, which helps create a seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is crucial for an accurate extraction.
The group head not only allows you to place your portafilter easily, but it also maintains a constant temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it is always at the right temperature to extract. This is important because even a few degrees can mean the difference between good and great espresso.
The Pump
In contrast to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure needed to extract espresso. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are generally less expensive and last longer than piston-driven machines. However, both kinds of machines can degrade due to overuse and insufficient cleaning. They also make mechanically complex which can result in an expensive price for even the simplest models.
Certain espresso machines utilize steam pressure instead of a pump to brew espresso. This could lead to over-extraction since the boiler that makes steam also heats the water until it comes to a boil. These machines also have to constantly rebuild their pressure between cups. This requires energy and time.
A large majority of espresso machines employ a rotary or vibration pump. A vibration model uses a vibrating disk to generate pressure, while a rotary model pushes hot water through the ground at a rapid speed. Both types of machine can make excellent espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the part that heats the water to the optimal temperature to extract. The steam produced is then directed to the portafilter, which is a container for espresso grounds. It is then funneled into the cup. The steam is able to create enough pressure to push the grounds of the coffee through. This creates a layer crema that is then poured over. This is one of the main characteristics of a good espresso.
There are three different types of espresso machines, each with different types of pumps and brew temperature. There are many ways to control the amount of brew, as well as the size of cup that can be produced by the machine.
The first espresso machines were steam types. The earliest espresso machines were steam types. The coffee tasted bitter and burned. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic device with an electric pump. This is what people envision when they think of an espresso machine. If you have a semi-automatic machine you grind the beans and tamp them by hand, but the pump provides regulated water flow and pressure. This is a great compromise between the human touch and the mechanized accuracy.
The Filter
Espresso machines typically use a filter that separates the grounds of coffee from hot water. The filter is also an essential component of the machine's temp control, since it stops overheating.
A filter can also help with flavor because it allows for the beans to flower for a longer period of time. This allows the beans to release their flavor and gives the chance for better extraction.
It is important to remember that even the best filter can produce a bad cup of coffee. The quality of the beans and the extraction, are still crucial.
It's in this area that the magic happens. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you place the portafilter - the thingy that you use to put the grounds of your coffee into when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds under high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing since 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 been gaining popularity. They use an air compressor to push hot water across the ground and are much more mobile than electric steam-driven espresso machines.