Don't Buy Into These "Trends" Concerning Machine Espresso
Don't Buy Into These "Trends" Concerning Machine Espresso
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How Does Machine Espresso Work?
The machine espresso uses precise pressure, as well as a filter technology that is mind-blowing to create the coffee you enjoy. How exactly does it work?
In order to make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure.
The Head of the Group
The group head is the portafilter that you insert when brewing espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are various kinds of group head, each with their particular advantages and disadvantages. Some are specifically designed for the stability of temperature while some are built to handle pre-infusion. Some are designed to control the lever. Some have a combination, like the E61. This is a very popular choice for baristas since it provides multiple advantages in a single package.
As you can see in the image above the group head comes with several notches to place your portafilter and twist it manually to lock it in. There is also a rubber gasket in the notches and helps create a seal when you insert your portafilter into the machine. The notches permit precise placement of your portafilter. This is crucial for a consistent extraction.
The group head is not just able to allow you to place your portafilter easily however, it also keeps a constant temperature. It does this by cycling hot water through the brew basket, and around the portafilter to ensure that it is always at the right temperature for extraction. It is crucial to keep in mind that even a tiny deviation can make the difference between a great and a excellent espresso.
The Pump
Unlike manual piston machines, which rely on a lever to pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure that are required for espresso extraction. The pressure is created 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 are generally less expensive than piston-driven machines, and tend to last longer, however both types of machines may degrade with overuse and insufficient cleaning. They also add mechanical complexity, which can result in a high price tag on even the simplest models.
Certain espresso machines do away with the pump entirely and use steam pressure to brew espresso. The downside is that the boiler that produces steam also raises the temperature of water to the point of boiling which could lead to excessive extraction. The machines must also constantly rebuild their pressure in between cups. This requires energy and time.
Many espresso machines make use of the rotary or vibration pump. A vibration model employs a rotating disk to generate pressure, whereas a rotating model pushes hot water through the ground at a rapid speed. Both models can produce an excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what will heat the water to a temperature that is ideal for extraction. The steam that is created reaches the portafilter, which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process, the steam causes pressure to push through the coffee grounds. This results in a layer of crema on top. This is one of the hallmarks of a good espresso.
There are three kinds of espresso machines, each having a different type of pump and the temperature of the brew. There are different ways to control the brew as well as the size of cup that can be made by the machine.
The first espresso machines were steam-types. They had one boiler to create steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure at most. This led to the coffee more info tasting burnt and bitter. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most common espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you have to grind the beans and then tamp them by hand. However, the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and mechanized consistency.
The Filter
Typically, espresso machines utilize filters to separate the grounds of coffee as they move through the hot water. The filter is also a vital part of the machine's temperature control, as it helps prevent overheating.
It also enhances flavor, since a filter can allow for a longer bloom phase. This lets the beans release their flavors, and allows for a better extraction.
However it is crucial to keep in mind that even a great filter can make a terrible cup of coffee as the quality of the beans and extraction are essential.
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 coffee grounds in, while making espresso.
In the steam-driven espresso machine hot water is heated in an airtight container to create steam. Steam then pushes the hot water through the grounds at high pressure. They are less expensive and easier for the user to maintain than pumps-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 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 more portable than electric steam-driven machines.