13 Things About Machine Espresso You May Not Have Known
How Does Machine Espresso Work?
The machine espresso is made using precision pressure, and a filtering system that is awe-inspiring to create the coffee you enjoy. What exactly is it that makes it work?
Espresso is made by pushing hot water at high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.
The Head of the Group
The name implies, the group head is the place you place your portafilter when making espresso. It disperses water into the portafilter and controls the pressure of the extraction. There are a variety of group heads, each with its own advantages and drawbacks. Some focus on temperature stability, others on pre-infusion options, and others are designed to control the lever. Some have a combination of features, like the E61, which is the standard choice for many baristas due to its ability to offer multiple benefits in one package.
As you can see in the photo above the group head is made up of several notches where you place your portafilter and twist it manually to lock it in. A gasket of rubber is situated inside the notches to help create a seal as you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial for an efficient extraction.
In addition to allowing you easily place your portafilter in, the group head is also responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket, ensuring that the temperature is constant for extraction. It is crucial to keep in mind that even a tiny variation can mean the difference between a good and excellent espresso.
The Pump
The motorized pumps that are used in espresso machines that rotate provide the nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines which use a lever. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines may degrade because of frequent use and insufficient cleaning. They also make mechanically complex and can lead to costly prices for even the simplest models.
Some espresso machines can eliminate the pump entirely and utilize steam pressure to make espresso. This can result in over-extraction because the boiler that makes steam also heats the water to boil. These machines also have to continually rebuild their pressure between cups. This requires energy and time.
A majority of espresso machines utilize a rotary or vibration pump. A vibration model uses the vibrating disk to create pressure, whereas the rotating model pushes hot water through the ground at a rapid speed. Both types of machines are capable of producing excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component which heats the water to the optimal temperature for extraction. The resulting steam reaches the portafilter that contains the ground espresso coffee, and is then funneled down into the cup. The steam creates enough pressure to push the grounds of coffee through. This results in a layer crema that is then poured over. This is one of the main characteristics of a good espresso.
There are three distinct types of espresso machines, each with different types of pumps and brew temperature. There are different ways to control the amount of brew, as well as the size of the cup that can be produced by the machine.
The first espresso machines were steam-types. They had one boiler to make steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most well-known espresso machine is a semiautomatic with an electric pump. This is what people envision when they think of an espresso machine. With a semi-automatic machine you need to grind the beans and then tamp them yourself but the pump provides regulated water flow and pressure. This is a fantastic combination of human control and mechanised consistency.
espresso makers have a filter that separates the grounds of the coffee from hot water. The filter is also an essential element of the temperature control system, as it prevents the machine from overheating.
It also helps with flavor, as a filter can allow for a longer bloom time. This lets the beans release their nuances, and allows for a better extraction.
However it is crucial to keep in mind that even a good filter can make a terrible cup of coffee, since the quality of the beans and extraction are essential.
It's in this area that the magic happens. This is the reason why espresso tastes so delicious. The grouphead (also known as the brewhead) is where you place the portafilter, the device that you put the grounds of coffee into while making espresso.
In the steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which then pushes the hot water through the grounds under high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create 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 years, compressed air-pump-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the grounds and are more portable than electric steam-driven machines.