How Does Machine Espresso Work?
The machine espresso utilizes precise pressure and filtering system that is awe-inspiring to make the coffee you enjoy. What exactly is it?
Espresso is created by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.
The Head of the Group
The name implies the group head is where you insert your portafilter when making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the extraction. There are a variety of group heads each with its own advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. There are also some that have a combination of features, like the E61, which is considered the classic choice among many baristas for its ability to offer multiple benefits in a single package.
As you can see in the above photo the head of the group is fitted with several notches. It is possible to place your portafilter inside these notches, and then turn the head around to secure it. A gasket made of rubber is positioned in the notches to create a seal as you insert your portafilter. The notches on the head allow for an exact placement of the portafilter, which is vital for an even extraction.
The group head is not just able to allow you to insert your portafilter easily however it also keeps the same temperature. 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 important to realize that even a slight differences can make the distinction between a great and a great espresso.
The Pump
The motorized pumps in rotary espresso machines provide the nine atmospheric bars of pressure required for espresso extraction. This differs from manual piston machines which use a lever. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps are typically less expensive and last for longer than piston-driven machines. However, coffee espresso machine of machines can deteriorate because of frequent use and inadequate cleaning. Pumps are also more complex mechanically, which can raise the cost of even the simple models.
Certain espresso machines do away with the pump entirely and make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. They also have to continually rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of an rotary or vibrating pump, with a vibration model that uses a vibrating disc to create pressure and the rotary model pushing hot water through the grounds at high speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to break.
The Boiler
The boiler is the part which heats the water to the optimal temperature to extract. The resultant steam then reaches the portafilter that contains ground espresso beans and gets funnelled down into the cup. In this process, the steam creates pressure and pushes through the coffee grounds. This results in a layer crema that is then poured over. This is one of the hallmarks of a good espresso.
There are three types of espresso machines, each having a different type of pump and the temperature of the brew. There are also different ways that the brew can be controlled as well as the size of the cup that the machine can make.
The first espresso machines were steam type. They had one boiler to create steam and brew, however, the pressure they could generate was low - only two bars of atmospheric pressure at the most. The coffee tasted bitter and burned. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso machine is a semiautomatic model with an electric pump. These are the images people have when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself while the pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized quality.
The Filter
Espresso machines typically have a filter that separates the grounds of coffee from hot water. The filter is also a vital part of the temperature control system as it keeps the machine from overheating.
It also aids in flavor, as a filter can allow for a longer bloom phase. This lets the beans release their flavor and allows for better extraction.
However it is crucial to keep in mind that even a high-quality filter can produce a bad cup of coffee as the quality of the beans and extraction are essential.
It's in this area that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead, also referred to as the brew head, is the place where the portafilter (the container you place the ground coffee in) is located when you're making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds at high pressure. These kinds of machines tend to be less expensive and simpler to maintain than pump-driven models. They are however limited in their ability for creating the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent times, espresso machines powered by a compressed air compressor have become increasingly popular. They use an air compressor to push hot water through the grounds and are significantly more portable than electric steam-driven machines.