How Does Machine Espresso Work?
The machine espresso is made using precise pressure and filtering system that is awe-inspiring to create the coffee you love. What exactly does it work?
Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.
The Head of the Group
As the name implies, the group head is where you put your portafilter in when making espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are many different kinds of group heads each with its own advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. Some include a combination like the E61. This is a very popular choice for baristas as it provides a variety of benefits in one package.
As you can see in the image above The group head features several notches to place your portafilter before twisting it by hand to secure it. A gasket made of rubber is positioned within the notches to make a seal when you insert your portafilter. The notches allow for an exact placement of the portafilter. This is crucial to ensure a consistent extraction.
Aside from allowing you to easily place your portafilter in, the group head is responsible to ensure that the temperature remains even. This is achieved by cycling hot water around the portafilter, and through the brew-basket, making sure that the temperature is constant to extract the coffee. This is crucial, since even a few degrees can make the difference between excellent 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 that provide the nine atmospheric bars of pressure necessary 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 than piston-driven models, and they tend to last longer, however both types of machines could be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, which could increase the cost of even simplest models.
Some espresso machines make use of steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since the boiler that produces steam also warms the water to boil. In addition these machines are often required to rebuild their pressure between cups, which takes time and energy.
A majority of espresso machines utilize the rotary or vibration pump. A vibration model utilizes the vibrating disk to create pressure, while a Rotary model pushes hot coffee through the ground at high speed. Both models can make a great espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what will heat the water to a temperature that is ideal for extraction. The steam created reaches the portafilter, which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process, the steam causes pressure to push through the grounds of the coffee. This results in a crema on the top of the espresso. This is one of the hallmarks of a great espresso.
There are three kinds of espresso maker s, which differ in the kind of pump they use and how hot the coffee is. There are various ways to control the brew as well as the size of cup that can be produced by the machine.
The earliest espresso machines were steam-based. They used one boiler to create both steam and brew, however, the pressure they could produce was not very high - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you grind the beans and then tamp them by hand, but the pump controls the flow of water and pressure. This is a great compromise between the human touch and mechanized accuracy.
The Filter
Typically, espresso machines use a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating.
It also aids in flavor, as it lets you enjoy a longer bloom time. This allows the beans to let their nuances out, and improves extraction.
However, it is important to remember that even a good filter could result in a bad cup of coffee, as the quality of the beans and extraction are important.
This is where the magic happens, it's what makes espresso taste good. The grouphead, often referred to as the brew head, is where the portafilter (the device you put the ground coffee into) is placed when you're making espresso.
Steam-driven espresso machines use hot water heated in an airtight container to make steam. The steam then pushes hot water through the grounds of coffee under high pressure. They are less expensive and easier for the owner to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.
In recent years, compressed-air-pump-driven espresso machines have become more popular. They use an air compressor to push hot water through the grounds, and are far more portable than electric steam-driven machines.