How Does Machine Espresso Work?
The machine espresso utilizes precise pressure, as well as a filtering technology that is amazing to make the coffee you enjoy. How exactly does it work?
Espresso is created by forcing hot water under high 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 the water into the portafilter, and regulates the pressure of extraction. There are a variety of group heads each with its own advantages and disadvantages. Some are designed for the stability of temperature while some are designed to handle pre-infusion. Others are built to control the lever. Some have a combination of features, like the E61, which is the most popular choice among baristas due to its ability to offer multiple perks in one package.
As you can see from the picture above, the group head has a number of notches. It is possible to place your portafilter in these notches and then twist the head to lock it. There is also a rubber gasket that resides inside the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise placement of the portafilter, which is vital to ensure an even extraction.
The group head not only allows you to insert your portafilter easily but also maintains 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. It is important to remember that even a tiny differences can make the distinction between a good and a great espresso.
The Pump
In contrast to manual piston machines which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure needed for espresso extraction. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground coffee inside the group head.
Pumps tend to be cheaper and last longer than piston-driven machines. However, both types of machines can degrade because of frequent use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simple models.
Some espresso machines do away with the pump entirely and make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that produces steam also heats the water until it comes to a boil. Additionally the machines often have to rebuild their pressure between cups, which requires time and energy.
A large majority of espresso machines employ either a vibration or rotary pump. A vibration model makes use of an oscillating disk to create pressure, whereas the rotating model pushes hot water through the ground at a high speed. Both models can make excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the element that heats the water to the optimal temperature for extraction. The steam that is created will eventually reach the portafilter, which holds the espresso grounds. The steam is then channeled into the cup. The steam causes enough pressure to push the coffee grounds through. This results in a layer of crema on top. This is the hallmark of a good espresso.
There are three types of espresso makers, and they differ in the type of pump they use and the degree of heat that the espresso is. There are different ways in which the brew could be controlled and the size of the cup the machine is capable of making.
The earliest espresso machines were steam-based. They used only one boiler to make steam and brew, however the pressure they were able to produce was very low - just two bars of atmospheric pressure maximum. This led to the coffee tasting burnt and bitter. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most commonly used espresso maker is a semi-automatic machine that has an electric pump. When people think of espresso machines, they picture these machines. If you have a semi-automatic machine you have to grind the beans and tamp them by hand. However, the pump is able to regulate the flow of water and pressure. This is an excellent combination of human control and mechanized consistency.
The Filter
Espresso machines usually have a filter that separates the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temp control, as it prevents overheating.
A filter also helps with flavor, as it permits the beans to flower for a longer period of time. This allows the beans to release their nuances, and allows for better extraction.
It is important to keep in mind that even the best filter can result in a bad cup of coffee. espresso coffee machine of the beans as well as the extraction, remain vital.
It's in this area that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter, the thingy which you put the grounds of coffee into when 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 high pressure. These kinds of machines tend to be less expensive and simpler to maintain than pump-driven models. However, they are limited in their ability 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 bars.
In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air compressor to force hot water into the grounds and are significantly more portable than steam-driven electric machines.