How Does Machine Espresso Work?
Machine espresso employs precise pressure and incredible filter technology to produce the delicious coffee we enjoy. But how exactly does 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 but the major difference is in the pressure.
The Group Head
The name implies the group head is the place you insert your portafilter when brewing espresso. It disperses water in the portafilter and controls the pressure of the extraction. There are various kinds of group head, each with their distinct advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. Some are a combination, such as the E61. This is a very popular choice for baristas due to the fact that it has multiple advantages in a single package.
As you can see in the image above the head of the group is equipped with several notches. The portafilter is placed in these notches and then turn the head around to secure it. There is also a gasket of rubber in the notches to help create an airtight seal when you insert your portafilter into the machine. The notches permit an exact placement of the portafilter. This is essential for an accurate extraction.
The group head not only allows you to put in your portafilter easily however it also keeps a constant temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is always at the right level for extraction. It is important to remember that even a slight differences can make the distinction between a good and a excellent espresso.
The Pump
Motorized pumps in rotary espresso machines supply the nine atmospheric bars of pressure required to extract espresso. This differs from manual piston machines which use levers. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps are typically cheaper and last longer than piston-driven machines. However, both kinds of machines can deteriorate due to excessive use and insufficient cleaning. They also create mechanical complexity, which can result in a high end espresso machine price tag on even the most basic models.
Certain espresso machines do away with the pump completely and utilize steam pressure to make espresso. This can lead to over-extraction as the boiler that makes steam also warms the water to boil. Additionally these machines are often required to restore their pressure between cups, which takes time and energy.
A large majority of espresso machines employ an rotary or a vibration pump. A vibration model employs an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at a rapid speed. Both machines can make excellent espresso but rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the part that heats water to an ideal temperature for extraction. The resulting steam is then transferred to the portafilter containing ground espresso beans and is then funneled down into the cup. During this process the steam is able to create enough pressure to push the grounds of the coffee machine espresso through. This produces a layer of crema on top. This is one of the main characteristics of a good espresso.
There are three types of espresso makers, which differ in the kind of pump they use and the degree of heat that the brew is. There are various ways in which the brew can be controlled, as well as the size of the cup that the machine can make.
The first espresso machines were steam-type. They used one boiler to create both brew and steam, however the pressure they were able to generate was low – only two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they think of these machines. If you have a semi-automatic machine you must grind the beans and tamp them by hand. However, the pump provides regulated water flow and pressure. This is a great compromise between the human touch and mechanized consistency.
The Filter
Espresso machines typically have filters that separate the grounds of coffee from hot water. The filter is also an important component of the temperature control system as it prevents the machine from overheating.
It also aids in flavor, as it allows for a longer bloom time. This allows the beans to release their flavors, and allows for better extraction.
However it is crucial to remember that even a high-quality filter can produce a bad cup of coffee, because the quality of the beans and extraction is still crucial.
It’s here that the magic happens. This is what makes uk espresso machine taste so delicious. The grouphead, often referred to as the brew head, is where the portafilter (the device you put the ground coffee in) is placed when making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water into the coffee grounds under high pressure. These types of machines are generally less expensive and simpler to maintain than pump-driven models. However, they are not as efficient in their ability to provide the perfect brewing conditions because they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air pump-driven espresso machines have been gaining popularity. They utilize an air compressor to force the hot water through the grounds and are much more portable than electric steam-driven machines.
