How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to make the perfect cup of coffee. What exactly does it work?
Espresso is made by pushing hot water 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 insert when brewing espresso. It distributes water into the portafilter, and then regulates the pressure of extraction. There are several different types of group heads each with its distinct advantages and drawbacks. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. Some include a combination such as the E61. This is a popular choice among baristas as it provides a variety of benefits in a single package.
As you can see from the picture above, the group head is fitted with several notches. The portafilter is placed in these notches, then twist the head to lock it. There is also a rubber gasket that is a part of the notches, which helps create an airtight seal when you insert your portafilter into the machine. The notches permit precise placement of your portafilter. This is crucial to ensure a consistent extraction.
The group head not only allows you to put in your portafilter easily however it also keeps an even temperature. It does this by cycling hot water through the brew container and around the portafilter, making sure that it's always at the correct temperature to extract. This is vital, because even a small difference in temperature can mean the difference between good and excellent espresso.
The Pump
In contrast to manual piston machines which use a lever to pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be cheaper than piston-driven machines, and tend to last longer, however both types of machines could degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which could increase prices of even most basic models.
Certain espresso machines eliminate the pump completely and employ steam pressure to create espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling and can result in excessive extraction. Additionally these machines typically have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines utilize a vibration or rotary pump, which is a vibration model using a rotating disc to create pressure and a rotary model pushing hot water through the grounds under high speed. Both types of machine can produce an excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the part that heats the water to the ideal temperature to extract. The resultant steam then reaches the portafilter containing ground espresso beans and is then pumped down into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This results in a layer crema on top. This is one of the main characteristics of a good espresso.
There are three different types of espresso machines, each having a different type of pump and brew temperature. There are different ways that the brew may be controlled, as well as the dimensions of the cup the machine can produce.
The first espresso machines were steam-types. The first espresso machines were steam-type machines. This resulted in the coffee tasting burnt and bitter. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most popular espresso maker is a semi-automatic device with an electric pump. This is what people envision when they imagine an espresso machine. With a semi-automatic espresso machine, you must grind the beans and tamp them by hand, but the pump regulates the flow of water and pressure. This is an excellent compromise between human control and mechanised accuracy.
The Filter
Espresso machines usually use filters that separate the coffee grounds from the hot water. The filter is also an essential part of the temperature control system as it prevents the machine from overheating.
It also enhances flavor, as a filter allows for a more prolonged bloom time. This helps the beans to release their flavors and provides an opportunity for a better extraction.
It is important to remember that even the finest filter could result in a poor cup of coffee. The quality of the beans and the extraction process, remain vital.
This is where the magic happens, and it's what makes espresso taste great. The grouphead, often referred to as the brewhead, is where the portafilter (the thing you put the ground coffee in) is located when you're making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight container to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. However, they are limited in their capacity to create the perfect conditions for brewing, because they operate at 1-1.5 bars of pressure. However, Our Home Page requires 9-10 bar.
In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water through the ground and are much more mobile than electric steam-driven espresso machines.