How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and a filter technology that is mind-blowing to make the coffee you enjoy. What exactly does it work?
Espresso is produced by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.
The Group Head
The group head is the portafilter that is inserted when you are making espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure that results from the extraction. There are various kinds of group heads, each with their own advantages and drawbacks. Some are specifically designed for stability of temperature 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 popular choice among baristas because it offers multiple benefits in one package.
As you can see in the above photo, the group head has a number of notches. It is possible to place your portafilter in these notches, then twist the head to secure it. A gasket of rubber is situated within the notches to create a seal while you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is vital for an even extraction.
Apart from allowing you effortlessly insert your portafilter the group head is also responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew basket, and around the portafilter, making sure that it's always at the right temperature to extract. It is crucial to keep in mind that even a tiny difference can make the difference between a great and a great espresso.
The Pump
In contrast to manual piston machines which use a lever to pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure needed to extract espresso. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger prior to being pumped through the ground coffee inside the group head.
Pumps are typically less expensive than piston-driven machines and tend to last longer, but both types of machines can become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which can raise the price of even the simplest models.
Certain espresso machines remove the pump completely and instead use steam pressure to brew espresso. This can lead to over-extraction as the boiler that produces steam also heats the water to boil. In addition these machines are often required to restore their pressure between cups, which requires time and energy.
Many espresso machines employ a vibration or rotary pump, which has a vibration model using a vibrating disc that generates the pressure and rotating models that push hot water through the grounds under high speed. Both models can produce an excellent espresso, however the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the part that heats the water to the ideal temperature to extract. espresso coffee machines created gets to the portafilter which holds the espresso grounds. It is then pumped into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This results in a crema on the top of the espresso. This is a hallmark of a great espresso.
There are three different types of espresso machines, each having a different type of pump and the temperature of the brew. There are different 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 had only one boiler to make both steam and brew however, the pressure they could create was minimal - two bars of atmospheric pressure maximum. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso machine is a semiautomatic one with an electric pump. This is what people envision when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the water flow and pressure. This is a great compromise between the human touch and mechanized quality.
The Filter
Typically, espresso machines use filters to separate the grounds of coffee when they pass through the hot water. The filter is also an important element of the temperature control system since it helps prevent the machine from overheating.
A filter also helps with flavor, as it permits a longer flowering period. This allows the beans to let their nuances out, and improves extraction.
However it is crucial to remember that even a top filter could result in a bad cup of coffee as the quality of the beans and extraction are essential.
This is where the magic happens, it's the thing that makes espresso taste great. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you use to put the grounds of coffee into while making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then moves hot water through the grounds of coffee under high pressure. These types of machines tend to be less expensive and easier to maintain than pump-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 ideal shot requires 9-10 bars.
In recent times, espresso machines powered by a compressed air pump have become increasingly popular. They use an air compressor to push hot water through the grounds and are significantly more portable than electric steam-driven machines.