How Does Machine Espresso Work?
Machine espresso uses precision pressure and mind-blowing filter technology to create the coffee we love. But how exactly does it work?
In order to make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.
The Group Head
The group head is the portafilter you put in when making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are numerous kinds of group heads each with its own advantages and disadvantages. Some are designed for the stability of temperature while some are designed to handle pre-infusion. Others are built to control the lever. There are also some that contain a variety of features, like the E61, which is considered the standard choice for many baristas for its ability to provide multiple benefits in one package.
As you can see in the picture above the group head is equipped with several notches. It is possible to place your portafilter in these notches and then twist the head to secure it. A rubber gasket is located inside the notches, which helps create a seal when you insert your portafilter. The notches on the head permit a precise position of the portafilter which is essential for an efficient extraction.
The group head does not just allow you to place your portafilter easily but also maintains the temperature at a constant level. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is constant to extract the coffee. It is crucial to keep in mind that even a slight difference can make the difference between a good and excellent espresso.
The Pump
Unlike manual piston machines, that use a lever to pressurize water, the rotary espresso machines use motorized pumps to provide the nine atmospheric bars of pressure 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 less expensive than piston-driven machines, and they tend to last longer, but both types of machines can get damaged through overuse and lack of cleaning. They also add mechanical complexity which can result in a high price tag on even the simplest models.
Some espresso machines remove the pump entirely and utilize steam pressure to make espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of water to boiling, which can lead to excessive extraction. In addition these machines typically have to rebuild their pressure between cups, which takes time and energy.
A majority of espresso machines use either a rotary or vibration pump, which is a vibration model using a vibrating disc to generate the pressure, and an rotary model that pushes hot water through the grounds at high speed. Both types of machine can make excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the one that will heat the water to the perfect temperature to extract. The steam that is created gets to the portafilter which is a container for espresso grounds. It is then poured into the cup. The steam generates enough pressure to push the grounds of the coffee through. This creates a foam on top of the espresso. This is one of the main characteristics of a great espresso.
There are three types of espresso maker s. They differ in the type of pump they use and the degree of heat that the brew is. There are different ways to control the strength of the brew and the size of the cup that can be made by the machine.
The first espresso machines were steam-types. The first espresso machines were steam-type machines. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans on your own The pump, however, regulates the water flow and pressure. This is a perfect compromise between human control and mechanized consistency.
The Filter
Typically, espresso machines have a filter to separate out the coffee grounds as they pass through the hot water. The filter is also an essential component of the machine's temperature control, as it helps prevent overheating.
Filters also aid in flavor as it allows for an extended flowering time. This allows beans to release their flavor and gives an opportunity for better extraction.
However it is crucial to remember that even a high-quality filter can produce a bad cup of coffee, since the quality of the beans and extraction are essential.
This is where the magic happens, and it's what makes espresso taste great. The grouphead, sometimes referred to as the brewhead, is where the portafilter (the thing you put the ground coffee into) sits when you're making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds with high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have been gaining popularity. They use an air compressor to push hot water across the ground. They are also more mobile than steam-driven electric espresso machines.