How Does Machine Espresso Work?
Machine espresso uses precision pressure and mind-blowing filter technology to make the perfect cup of coffee. How exactly does it work?
In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Head of the Group
The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure of the resulting extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are specifically designed for stability of temperature while others are designed to handle pre-infusion. Others are made to control the lever. There are some that come with a range of features, such as the E61 one, which is the standard choice for many baristas for its ability to offer multiple benefits in one package.
As you can see in the above image The group head features many notches in which you can put your portafilter, then twist it by hand to lock it in. There is also a gasket of rubber that is a part of the notches and helps to create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of your portafilter. This is crucial to ensure an even extraction.
The group head does not just allow the portafilter to be inserted easily however, it also keeps the same temperature. It does this by cycling hot water through the brew container and around the portafilter, ensuring that it is always at the right temperature to extract. This is vital, because even a small difference in temperature can mean the difference between excellent and great espresso.
The Pump
In contrast to piston machines that are manually operated, which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to 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 tend to be cheaper and last longer than piston-driven machines. However, both types of machines can degrade due to overuse and inadequate cleaning. Pumps are also more complex mechanically, which can increase prices of even simple models.
Certain espresso machines can eliminate the pump completely and make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that produces steam also causes the water to boil. They also have to constantly rebuild their pressure between cups. This takes energy and time.
A majority of espresso machines utilize a rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, whereas a rotary model pushes hot water through the ground at a fast speed. Both machines can produce excellent espresso but rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the component that heats the water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter, which contains the ground espresso coffee and is then pumped into the cup. During this process, steam creates pressure and pushes through the grounds of the coffee. This creates a layer crema on top. This is the hallmark of a great espresso.
There are three types of espresso makers. They differ in the type of pump they employ and how hot the coffee is. There are a variety of ways to control the strength of the brew and the size of cup that can be produced by the machine.
The first espresso machines were steam-types. The earliest espresso machines were steam types. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
professional espresso maker used espresso machine is a semiautomatic model 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 by yourself while the pump controls the water flow and pressure. This is an excellent compromise between human touch and mechanized quality.
The Filter
Espresso machines usually use a filter that separates the grounds of coffee from hot water. The filter is also a vital component of the machine's temp control, as it prevents overheating.
It also improves flavor, as a filter lets you enjoy a longer bloom phase. This allows the beans to release their nuances and gives the chance for better extraction.
However, it is important to remember that even a great filter can result in a poor cup of coffee, since the quality of the beans and extraction are important.
This is where the magic happens, and it's what makes espresso taste good. The grouphead, sometimes referred to as the brew head, is where the portafilter (the device you put the coffee ground into) is located when you're making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to create steam. The steam then pushes hot water into the grounds of coffee under high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent times, espresso machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to push hot water into the grounds and are more portable than electric steam-driven machines.