How Does Machine Espresso Work?
The machine espresso utilizes precision pressure, and a filter technology that is awe-inspiring to make the coffee you love. How does it work exactly?
To make espresso hot water is forced 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
The group head is the portafilter you insert when brewing espresso. It disperses water in the portafilter, and regulates the pressure during the extraction. There are various kinds of group heads, each with their unique advantages and drawbacks. Some are designed for temperature stability while others are designed to handle pre-infusion. Others are built to control the lever. Some include a combination like the E61. This is a favorite among baristas due to the fact that it has multiple benefits in one package.
As you can see in the above image the group head is made up of several notches where you place your portafilter and then twist it manually to secure it. There is also a gasket of rubber which is located inside the notches and helps to create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of the portafilter. This is vital for an efficient extraction.
The group head not only allows you to place your portafilter easily however it also keeps the temperature at a constant level. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it's always at the correct temperature for extraction. It is crucial to keep in mind that even a tiny variation can mean the difference between a decent and a great espresso.
The Pump
The motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure required to extract espresso. This is different from manual piston machines that use levers. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be less expensive and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to overuse and insufficient cleaning. They also increase the complexity of mechanical systems, which can result in a high price tag on even the most basic models.
Some espresso machines do away with the pump entirely and employ steam pressure to create espresso. The drawback is that the boiler that produces steam also increases the temperature of water to boiling which could lead to excessive extraction. Additionally these machines typically have to restore their pressure between cups, which requires time and energy.
A majority of espresso machines use a vibration or rotary pump, with a vibration model using a vibrating disc to create the pressure and a rotary model pushing hot water through the grounds at high speed. Both machines can make great espresso, but rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the one that heats the water to the ideal temperature for extraction. The steam created gets to the portafilter which contains the espresso coffee grounds. The steam is then channeled into the cup. During this process the steam creates enough pressure to push the grounds of coffee through. This creates a layer crema on top. This is one of the hallmarks of a good espresso.
There are three kinds of espresso machines, each with distinct pumps and brew temperature. There are espresso coffee machines of ways to control the brew and the size of cup that can be produced by the machine.
The earliest espresso machines were steam types. They used a single boiler to make both steam and brew however, the pressure they could generate was low - only two bars of atmospheric pressure at most. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso maker is a semi-automatic machine that has an electric pump. These are what people imagine when they think of an espresso maker. If you have a semi-automatic machine you need to grind the beans and then tamp them by hand, but the pump controls the flow of water and pressure. This is an excellent combination of human control and mechanised accuracy.
The Filter
Typically, espresso machines have filters that separate the coffee grounds as they pass through the hot water. The filter is also a crucial component of the temperature control system since it helps prevent the machine from overheating.
It also enhances flavor, as it allows for a longer bloom time. This helps the beans to release their flavor and gives the chance for better extraction.
However, it is important to keep in mind that even a great filter can make a terrible cup of coffee, because the quality of the beans and extraction are crucial.
This is where the magic happens, it's the thing that makes espresso taste good. The grouphead, sometimes referred to as the brew head, is where the portafilter (the thingy you put the ground coffee into) sits when you're making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through grounds of coffee at high pressure. These types of machines are generally less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their ability to create the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have become more popular. They use an air-compressor to push hot water through the ground, and are more mobile than electric steam-driven espresso machines.