How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and amazing filter technology to make the perfect cup of coffee. But how exactly does 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 main difference.
The Group Head
The name implies the group head is where you place your portafilter while brewing espresso. It disperses water in the portafilter and regulates the pressure of the extraction. There are various kinds of group head each with its unique advantages and disadvantages. Some are designed to provide the stability of temperature while some are specifically designed to handle pre-infusion. Some are designed to control the lever. There are also some that include a mix of features, such as the E61, which is considered the standard choice for many baristas because of its ability to provide multiple benefits in one package.
As you can see in the above photo the group head is made up of numerous notches that you can put your portafilter, then twist it by hand to secure it. A rubber gasket is located in the notches to create a seal as you insert your portafilter. The notches allow for an exact placement of the portafilter. This is vital for a consistent extraction.
Apart from allowing you effortlessly insert your portafilter the group head is also responsible for maintaining an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is at the right level for extraction. It is important to remember that even a few degree deviation can make the difference between a good and a great espresso.
The Pump
Unlike manual piston machines, which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure required for espresso extraction. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior being pumped through the ground coffee and espresso machine inside the group head.
Pumps are generally less expensive than piston-driven machines, and they tend to last longer, but both types of machines may become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which could increase the cost of even simple models.
Some espresso machines eliminate the pump entirely and make use of steam pressure to make espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of the water until it reaches boiling, which can lead to excessive extraction. These machines also have to constantly rebuild their pressure between cups. This takes energy and time.
Many espresso machines utilize either a rotary or vibration pump, with a vibrating model that uses a vibrating disc that generates the pressure, and the rotary model pushing hot water through the grounds at high speed. Both types of machines can produce an excellent espresso capsule machine, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats the water to the ideal temperature to extract. The steam that is produced is then directed to the portafilter, which is the container that holds the espresso coffee grounds. It is then pumped into the cup. The steam creates enough pressure to push the coffee grounds through. This creates a layer crema on top. This is one of the hallmarks of a good espresso.
There are three types of italian espresso machines machines, each having distinct pumps and the temperature of the brew. There are many ways to control the amount of brew, as well as the size of the cup that can be made by the machine.
The earliest espresso machines were steam-based. The earliest espresso machines were steam types. This led to the coffee tasting bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most common espresso machine is a semiautomatic that has an electric pump. These are the images people have when they think of an espresso machine. With a semi-automatic espresso machine (learn here), you need to grind the beans and tamp them by hand. The pump is able to regulate the flow of water and pressure. This is a perfect combination of human control and mechanised accuracy.
The Filter
Typically, espresso machines utilize a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also an important component of the temperature control system as it keeps the machine from overheating.
A filter can also help with flavor because it allows for an extended flowering time. This helps the beans to release their flavor and gives an opportunity to improve extraction.
However, it is important to remember that even a top filter can result in a poor cup of coffee, as the quality of the beans and extraction is still important.
This is where the magic happens, and it’s what makes an espresso really taste good. The grouphead, sometimes referred to as the brew head, is where the portafilter (the thing you put the coffee grounds into) is located when you’re making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to create steam, which is then pushed through the grounds at a high pressure. These machines are less expensive and easier for the user to maintain than pumps-driven models. They are however limited in their ability for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air-compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.