How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to make the perfect cup of coffee. How exactly does it work?
To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However it is the pressure that makes the main difference.
The Head of the Group
As the name implies the group head is where you insert your portafilter when brewing espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure of the resulting extraction. There are many different kinds of group head, each with their unique advantages and drawbacks. Some are specifically designed for stability of temperature while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some include a mix of features, like the E61 one, which is the classic choice among many baristas due to its capacity to offer multiple benefits in one package.
As you can see in the photo above the group head is made up of numerous notches that you can place your portafilter before twisting it with your hands to secure it. There is also a rubber gasket that is a part of the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for an exact positioning of the portafilter which is essential for an even extraction.
The group head not only lets the portafilter to be inserted easily however, it also keeps a constant temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right to extract the coffee. This is important, as even a small difference in temperature can be the difference between a good and great espresso.
The Pump
Unlike manual piston machines, that use a lever to pressurize water, rotating espresso machines rely upon motorized pumps to provide the nine atmospheric bars of pressure needed for espresso extraction. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground coffee inside the group head.
Pumps tend to be less expensive than piston-driven machines, and they tend to last longer, however both types of machines could become damaged due to excessive use and poor cleaning. They also create mechanical complexity and can lead to costly prices for even the simplest models.
Some espresso machines eliminate the pump entirely and make use of steam pressure to make espresso. The downside is that the same boiler that produces steam also raises the temperature of the water to boiling and can result in excessive extraction. The machines must also continually rebuild their pressure between cups. This requires energy and time.
Many espresso machines make use of a vibration or rotary pump, with a vibrating model using a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds at high speed. Both types of machines can produce an excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the element that heats the water to the ideal temperature for extraction. The steam that is produced reaches the portafilter which holds the ground espresso coffee, and is then funneled down 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 a sign of a good espresso.
There are three types of espresso makers, and they differ in the kind of pump they use and the degree of heat that the brew is. There are various ways that the brew can be controlled as well as the dimensions of the cup the maker can create.
The first espresso machines were steam types. They used one boiler to make both brew and steam, but the pressure they could generate was low - only two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most well-known espresso maker is a semi-automatic one that has an electric pump. When people think of espresso machines, they envision these machines. coffee and espresso maker -automatic machines require you to grind and tamp the beans by yourself The pump, however, regulates the water flow and pressure. This is a fantastic combination of human control and mechanized accuracy.
The Filter
Typically, espresso machines employ a filter to separate out the coffee grounds as they pass through the hot water. The filter is also an essential part of the temperature control system, as it prevents the machine from overheating.
Filters also aid in flavor as it allows for a longer flowering period. This lets the beans release their nuances, and allows for a better extraction.
However, it is important to remember that even a good filter could result in a bad cup of coffee, since the quality of the beans and extraction is still crucial.
It's in this area that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy which you put the grounds of your coffee into while making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. This is then pushed through the grounds under high pressure. These kinds of machines are usually cheaper and easier to maintain than pumps-driven models. However, they are limited in their capacity to create the ideal brewing conditions, since they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.
In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to force hot water into the grounds and are significantly more portable than electric steam-driven machines.