How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and incredible filter technology to produce the coffee we love. How exactly does it work?
Espresso is produced by pushing hot water under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.
The Head of the Group
The group head is the portafilter that you put in when making espresso. It disperses the water into the portafilter, and then regulates the pressure during the extraction. There are various kinds of group head, each with their unique advantages and disadvantages. Some are specifically designed for temperature stability while others are designed to handle pre-infusion. Others are built to control the lever. Some come with a combination of both, such as the E61. This is a popular choice among baristas as it provides a variety of benefits in one package.
As you can see in the image above the group head comes with several notches to place your portafilter before twisting it by hand to lock it in. A gasket of rubber is situated inside the notches to help make a seal when you insert your portafilter. The notches on the head permit an exact placement of the portafilter, which is necessary for a consistent extraction.
Aside from allowing you to easily connect your portafilter, the group head is responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is at the right level to extract the coffee. It is important to note that even a small difference can make the difference between a good and great espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure required to extract espresso. 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 frequent use and insufficient cleaning. They also increase the complexity of mechanical systems, which can result in a high price tag on even the simplest models.
Some espresso machines remove the pump completely and utilize steam pressure to make espresso. The drawback of this is that the boiler that produces steam also increases the temperature of water until it reaches boiling, which can lead to excessive extraction. Additionally, these machines frequently have to restore their pressure between cups, which requires time and energy.
Many espresso machines use a rotary or vibration pump. A vibration model employs an oscillating disk to create pressure, whereas the rotary model pushes hot water through the ground at a rapid speed. Both machines produce great espresso, however rotary machines are quieter, more durable and less likely to break down.
The Boiler
The boiler will heat the water to the perfect temperature to extract. The resulting steam is then transferred to the portafilter, which contains ground espresso beans and gets funnelled down into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This results in a crema on the top of the espresso. This is a hallmark of a good espresso.
There are three kinds of espresso machines, each having a different type of pump and brew temperature. There are different ways to control the brew and the size of the cup that can be made by the machine.
The earliest espresso machines were steam types. The first espresso machines were steam-type machines. The coffee tasted bitter and burned. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most popular espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they picture these machines. coffeee.uk Semi-automatic machines require you to grind and tamp the beans on your own while the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized consistency.
The Filter
Espresso machines usually use filters that separate the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temperature control, since it helps to prevent overheating.
It also enhances flavor, as it allows for a longer bloom phase. This allows the beans to release their flavor and gives an opportunity to improve extraction.
However, it is important to remember that even a top filter can result in a poor cup of coffee, as the quality of the beans and extraction are important.
This is where the magic happens, it's what makes an espresso really taste great. The grouphead, also referred to as the brew head, is where the portafilter (the device you put the coffee grounds into) is located when you're making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through the grounds of the coffee under pressure. These kinds of machines are generally less expensive and simpler to maintain than pump-driven models. However, they are limited in their ability to create the perfect conditions for brewing, since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.
In recent years, compressed air pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push hot water through grounds and are more portable than electric steam-driven machines.