How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and mind-blowing filter technology to create the coffee we love. What exactly is it that makes it work?
Espresso is created by forcing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee. However the pressure is the primary difference.
The Group Head
As the name implies, the group head is the place you put your portafilter in when brewing espresso. It distributes water into the portafilter, and then regulates the pressure of extraction. There are a variety of group heads each with its own advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some have a combination, such as the E61. This is a preferred choice for baristas due to the fact that it has multiple benefits in a single package.
As you can see in the above photo the group head is made up of several notches where you place your portafilter and then twist it by hand to lock it in. A gasket made of rubber is placed inside the notches, which helps create a seal while you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is necessary to ensure a consistent extraction.
In addition to allowing you easily insert your portafilter, the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket and around the portafilter, making sure that it's always at the correct temperature for extraction. It is important to realize that even a small differences can make the distinction between a good and great espresso.
The Pump
Unlike manual piston machines, which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure that are required to extract espresso. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the
best ground coffee for espresso machine coffee inside the group head.
Pumps are typically less expensive than piston-driven machines and tend to last longer, but both types of machines may get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, and can add to the cost of even the most basic models.
Some espresso machines use steam pressure instead of a pump to make espresso. The downside is that the same boiler that produces steam also increases the temperature of water to boiling and can result in over-extraction. In addition these machines are often required to restore their pressure between cups, which takes time and energy.
A majority of espresso machines utilize the rotary or vibration pump. A vibration model utilizes a vibrating disk to generate pressure, while a rotary model pushes hot water through the ground at a high speed. Both models are capable of producing excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the part that heats water to an optimal temperature to extract. The steam created is then directed to the portafilter, which is a container for espresso grounds. It is then funneled into the cup. During this process, steam creates pressure to push through the grounds of the coffee. This results in a whipped-up 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 how hot the espresso is. There are different ways to control the brew and the size of the cup that can be produced by the machine.
The first espresso machines were steam-type. They utilized a single boiler to make both steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure at most. The coffee tasted bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso machine is a semiautomatic model with an electric pump. These are what people imagine when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself, but the pump regulates the water flow and pressure. This is a fantastic compromise between human control and mechanized consistency.
The Filter
Espresso machines usually have filters that separate the grounds of the coffee from hot water. The filter is also a vital component of the machine's temperature control, since it helps to prevent overheating.
It also improves flavor, since a filter allows for a more prolonged bloom time. This helps the beans release their nuances and gives the chance for better extraction.
It is important to remember that even the finest filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, are still very important.
This is where the magic happens, it's the thing that makes espresso taste good. The grouphead, often called the brew head, is where the portafilter (the container you place the coffee ground into) is placed when making espresso.
In an
best espresso machine under 200 machine that is driven by steam, hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds at high pressure. These kinds of machines tend to be less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their capacity to create the perfect conditions for brewing, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.
In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air compressor to push hot water through grounds and are more portable than steam-driven electric machines.
