How Does Machine Espresso Work?
espresso coffee machine uk makes use of precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. What exactly does it work?
To make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However, it is the pressure that makes the main difference.
The Group Head
The group head is the portafilter you place in the espresso maker when making it. It disperses the water into the portafilter, and then regulates the pressure of extraction. There are various kinds of group head each with its own advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. Some have a combination of features, such as the E61, which is considered the classic choice among many baristas due to its capacity to provide multiple benefits in a single package.
As you can see in the photo above, the group head has many notches in which you can place your portafilter and then twist it by hand to lock it in. There is also a gasket of rubber in the notches to help create a seal when you insert your portafilter into the machine. The notches on the head permit a precise placement of the portafilter, which is essential to ensure a consistent extraction.
In addition to allowing you to easily insert your portafilter, the group head is responsible for maintaining a consistent temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is always at the right level to extract the coffee. It is crucial to keep in mind that even a small difference can make the difference between a good and a great espresso.
The Pump
Contrary to manual piston machines that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure that are required for espresso extraction. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be cheaper than piston-driven machines, and they tend to last longer, but both types of machines could degrade with overuse and insufficient cleaning. They also make mechanically complex which can result in an expensive price for even the most basic models.
Certain espresso machines remove the pump completely and utilize steam pressure to make espresso. This can result in over-extraction because the boiler that produces steam also heats the water until it comes to a boil. The machines must also continually rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of a vibration or rotary pump, with a vibrating model using a vibrating disc to create the pressure and rotating models that push hot water through the grounds at high speed. Both types of machine can make a great espresso, but Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler heats the water to the perfect temperature for extraction. The resultant steam then reaches the portafilter, which contains the ground espresso and gets funnelled down into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This creates a foam on the top of the espresso. This is the hallmark of a great espresso.
There are three kinds of espresso makers, which differ in the type of pump they employ and how hot the coffee is. 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 type. The earliest espresso machines were steam types. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso maker is a semi-automatic one with an electric pump. This is what people envision when they imagine an espresso machine. If you have a semi-automatic machine you grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is a great compromise between human control and mechanised accuracy.
The Filter
Typically, espresso machines have filters that separate the grounds of the coffee as they go through the hot water. The filter is also an essential part of the temperature control system because it stops the machine from overheating.
It also helps with flavor, as it allows for a longer bloom time. This allows beans to release their flavor and gives an opportunity for better extraction.
However, it is important to keep in mind that even a top filter can result in a poor cup of coffee, because the quality of the beans and extraction is still crucial.
It's here that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead (also known as the brewhead) is where you put the portafilter, the device which you put the coffee grounds into, while making espresso.
In a steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds with high pressure. These machines are less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to produce the perfect conditions for brewing, because they operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.
In recent years, compressed air-driven espresso machines have been gaining popularity. They make use of an air compressor to force hot water through the ground, and are more mobile than electric steam-driven espresso machines.