How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and mind-blowing filter technology to create the coffee we love. But how exactly does it work?
Espresso is created by forcing hot water 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
As the name suggests, the group head is where you put your portafilter in when brewing espresso. It disperses water into the portafilter and regulates the pressure of extraction. There are a variety of types of group heads, each with their distinct advantages and drawbacks. Some are specifically designed for temperature stability while others are built to handle pre-infusion. Some are designed to control the lever. There are also some that have a combination of features, like the E61 one, which is the most popular choice among baristas for its ability to provide multiple benefits in one package.
As you can see in the image above the group head comes with numerous notches that you can place your portafilter before twisting it manually to lock it in. There is also a rubber gasket that resides inside the notches and helps create the seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is necessary for an even extraction.
Aside from allowing you to easily insert your portafilter, the group head is also responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew container and around the portafilter, making sure that it is always at the correct temperature to extract. This is vital, because just a few degrees could be the difference between a good and great espresso.
The Pump
In contrast to manual piston machines which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure that are required to extract espresso. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger prior it is shot through the ground coffee in the group head.
Pumps tend to be less expensive than piston-driven machines and tend to last longer, although both types of machines may become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which could increase prices of even most basic models.
Certain espresso machines eliminate the pump entirely and use steam pressure to brew espresso. The drawback is that the same boiler that produces steam also raises the temperature of water to boiling which can cause over-extraction. These machines also have to constantly rebuild their pressure between cups. This takes energy and time.
A large majority of espresso machines employ 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 high speed. Both models can make excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats the water to the ideal temperature to extract. The steam created gets to the portafilter which is a container for espresso grounds. It is then poured into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This creates a foam on the top of the espresso. This is a sign of a good espresso.
There are three types of espresso makers. They differ in the kind of pump they use and how hot the brew is. There are many ways to control the amount of brew, as well as the size of cup that can be produced by the machine.
The first espresso machines were steam-based. The first espresso machines were steam-type machines. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso maker is a semi-automatic machine that has an electric pump. This is what people envision when they think of an espresso maker. If you have a semi-automatic machine you must grind the beans and then tamp them by hand, but the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human control and mechanised consistency.
The Filter
Typically, espresso machines have a filter to separate out the coffee grounds as they pass through the hot water. The filter is also an essential component of the machine's temperature control, since it helps to prevent overheating.
It also helps with flavor as a filter can allow for a longer bloom phase. This helps the beans to release their nuances and gives an opportunity for better extraction.
It is important to remember that even the finest filter can result in a bad cup of coffee. The quality of the beans and the extraction process remain crucial.
It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter, which is the thingy which you put the grounds of your coffee into when making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam, which is then pushed through the grounds under high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. best coffee espresso machine requires 9-10 bars.
In recent times, espresso machines powered by a compressed air pump have become increasingly popular. They make use of an air compressor to force hot water into the ground, and are more mobile than steam-driven electric espresso machines.