How Does Machine Espresso Work?
Machine espresso employs precise pressure and incredible filter technology to produce the coffee we love. What exactly is it that makes it work?
In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However, it is the pressure that makes the main difference.
The Group Head
The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the resulting extraction. There are a variety of group heads each with its own advantages and disadvantages. Some are designed to provide temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. There are also some that include a mix of features, like the E61 that is the most popular choice among baristas because of its ability to offer multiple perks in a single package.
As you can see in the above photo the group head is made up of numerous notches that you can place your portafilter and twist it manually to secure it. There is also a rubber gasket that resides inside the notches to help create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact position of the portafilter which is necessary for a consistent extraction.
The group head is not just able to allow you to insert your portafilter easily however, it also keeps the same 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 for extraction. This is important because even a few degrees can make the difference between good and excellent espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure that are required for espresso extraction. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade due to overuse and inadequate cleaning. Pumps are also more complex mechanically, which can increase the cost of even simple models.
Certain espresso machines utilize steam pressure instead of a pump to make espresso. This can result in over-extraction because the boiler that produces steam also heats the water until it comes to a boil. Additionally these machines typically have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines employ the rotary or vibration pump, which has a vibration model using a rotating disc to create pressure, and a rotary model pushing hot water through the grounds at high speed. Both models can make a great espresso, but rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats water to the optimal temperature to extract. The steam that is produced reaches the portafilter, which holds the espresso grounds. It is then poured into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This creates a foam on the top of the espresso. This is the hallmark of a good espresso.
There are three kinds of espresso makers, which differ in the type of pump they employ and the degree of heat that the brew is. There are different ways in which the brew could be controlled, as well as the size of the cup that the maker can create.
The first espresso machines were steam types. The earliest espresso machines were steam-type machines. The coffee tasted bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most commonly used espresso machine machine espresso is a semiautomatic one with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp your beans yourself The pump, however, regulates the water flow and pressure. This is a perfect combination of human control and mechanised consistency.
The Filter
Espresso machines typically use filters that separate the grounds of coffee from hot water. The filter is also a vital component of the machine's temp control, since it stops overheating.
It also improves flavor, since a filter can allow for a longer bloom time. This allows beans to release their nuances and gives an opportunity to improve extraction.
It is important to remember that even the most efficient filter can result in a bad cup of coffee. The quality of the beans, and the extraction process remain crucial.
This is where the magic happens, and it's what makes espresso taste great. The grouphead, also called the brew head, is the place where the portafilter (the container you place the ground coffee into) sits when you're making espresso.
Steam-driven espresso machines use hot water heated in an airtight container to make steam. The steam then pushes hot water into the grounds of coffee at high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the ground and are much more mobile than electric steam-driven espresso machines.