One Of The Most Untrue Advices We've Ever Received On Machine Espresso
One Of The Most Untrue Advices We've Ever Received On Machine Espresso
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How Does Machine Espresso Work?
Machine espresso employs precise pressure and amazing filter technology to make the coffee we love. How exactly does it work?
To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Head of the Group
As the name implies the group head is the place you place your portafilter while brewing espresso. It distributes water into the portafilter and controls the pressure of the extraction. There are a variety of types of group head each with its own advantages and drawbacks. Some focus on temperature stability, others on pre-infusion features, and others are designed to control the lever. There are even some that contain a variety of features, such as the E61 that is the most popular choice among baristas due to its capacity to provide multiple benefits in a single package.
As you can see in the above image the group head is made up of many notches in which you can place your portafilter and then twist it manually to lock it in. There is also a gasket of rubber in the notches and helps to create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for an exact location of the portafilter which is necessary for a consistent extraction.
In addition to allowing you to effortlessly insert your portafilter the group head is also responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew basket, and around the portafilter, making sure that it's always at the correct temperature for extraction. It is important to realize that even a few degree difference can make the difference between a good and a great espresso.
The Pump
The motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure that is required to extract espresso. This is different from manually operated piston machines that employ a lever. This pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger before it is shot through the ground coffee in the group head.
Pumps are generally cheaper and last longer than piston-driven machines. However, both types of machines may degrade because of frequent use and inadequate cleaning. Pumps are also more complicated mechanically, and can add to the cost of even most basic models.
Certain espresso machines can eliminate the pump entirely and utilize steam pressure to make espresso. This can result in over-extraction because the boiler that produces steam also causes the water to boil. Additionally the machines often have to rebuild their pressure between cups, which takes time and energy.
A large majority of espresso machines employ a rotary or vibration pump. A vibration model utilizes a rotating disk to generate pressure, whereas the rotary model pushes hot water through the ground at a fast speed. Both models can produce an excellent espresso, however the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the one that heats the water to the right temperature to extract. The resulting steam reaches the portafilter which holds the ground espresso and is then pumped down into the cup. The steam causes enough pressure to push the grounds of coffee through. This results in a layer crema on top. This is the hallmark of a good espresso.
There are three kinds of espresso machines, each having different pumps and brew temperature. There are different ways that the brew may be controlled as well as the size of the cup that the machine is capable of making.
The first espresso machines were steam types. They utilized one boiler to make both steam and brew 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 the reason why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed 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 however the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized quality.
The Filter
Typically, espresso machines use a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a vital part of the machine's temperature control, as it helps prevent overheating.
A filter can also help with flavor as it allows for a longer flowering period. This helps the beans to release their nuances and gives an opportunity for a better extraction.
It is important to keep in mind that even the best filter can produce a bad cup of coffee. The quality of the beans, as well as the extraction, remain crucial.
This is where the magic happens, and it's what makes espresso taste great. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy which you put the coffee grounds into, when making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to create steam. The steam then moves hot water through the grounds of coffee under high pressure. These types of machines tend to be cheaper and easier to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing as they only operate more info with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent times, espresso machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to push hot water through the grounds and are much more portable than steam-driven electric machines.