The No. One Question That Everyone Working In Machine Espresso Should Be Able To Answer
The No. One Question That Everyone Working In Machine Espresso Should Be Able To Answer
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How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and amazing filter technology to make the coffee we love. What exactly is it that makes it work?
Espresso is made by pushing hot water at high 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
As the name implies the group head is where you place your portafilter while brewing espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are a variety of types of group heads each with its particular advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. Some have a combination of features, like the E61, which is considered the classic choice among many baristas because of its ability to offer multiple benefits in one package.
As you can see in the above photo the group head is fitted with several notches. It is possible to place your portafilter into these notches and 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 position of the portafilter which is vital to ensure a consistent extraction.
Aside from allowing you to easily connect your portafilter, the group head is responsible to ensure that the temperature remains even. This is achieved by cycling hot water around the portafilter, and through the brew-basket, making sure that the temperature is always at the right level for extraction. It is important to note that even a small difference can make the difference between a great and a excellent espresso.
The Pump
Motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure that is required to extract espresso. This differs from manually operated piston machines that employ a lever. The pressure is created by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and insufficient cleaning. They also make mechanically complex which can result in costly prices for even the most basic models.
Some espresso machines can eliminate the pump completely and make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that produces steam also heats the water until it comes to a boil. Additionally the machines often have to restore their pressure between cups, which requires time and energy.
A majority of espresso machines use the rotary or vibration pump, with a vibrating model that uses a vibrating disc to create the pressure, and rotating models that push hot water through the grounds under high speed. Both models are capable of producing excellent espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the one that makes the water warm to a temperature that is ideal for extraction. The steam that is created will eventually reach the portafilter, which contains the espresso coffee grounds. It is then poured into the cup. During this process, steam creates pressure that pushes through the coffee grounds. This results in a layer of crema on top. This is a sign 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 different ways to control the amount of brew, as well as the size of the cup that can be produced by the machine.
The first espresso machines were steam-types. They employed only one boiler to make both brew and steam, however the pressure they were able to produce was very low - just two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans on your own while the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized consistency.
The Filter
Espresso machines usually have filters that separate the grounds of the coffee from hot bean to cup espresso machine water. The filter is also a crucial component of the temperature control system, as it keeps the machine from overheating.
A filter also helps with flavor because it allows for the beans to flower for a longer period of time. This lets the beans let their nuances out, and allows for a better extraction.
It is important to remember that even the best filter can result in a bad cup of coffee. The quality of the beans, and the extraction, are still crucial.
It's here that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead, also called the brew head, is where the portafilter (the thingy you put the ground coffee in) is placed when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam, which then pushes the hot water through the grounds under high pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent times, espresso machines powered by a compressed air compressor have become increasingly popular. They utilize an air compressor to push hot water through the grounds and are more portable than electric steam-driven machines.