How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to create the perfect cup of coffee. What exactly is it that makes it work?
Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.
The Group Head
The group head is the portafilter you insert when brewing espresso. It distributes water into the portafilter, and then regulates the pressure of the extraction. There are several different types of group head, each with their unique advantages and drawbacks. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. Some have a combination, such as the E61. This is a popular choice among baristas due to the fact that it has multiple advantages in a single package.
As you can see from the photo above the group head has a number of notches. You place your portafilter into these notches and turn the head around to secure it. A rubber gasket is located in the notches to create a seal as you insert your portafilter. The notches allow for precise placement of the portafilter. This is vital for an accurate extraction.
The group head is not just able to allow the portafilter to be inserted easily however, it also keeps the temperature at a constant level. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level to extract the coffee. This is crucial, since just a few degrees could make the difference between excellent and great espresso.
The Pump
The motorized pumps used in espresso machines that rotate provide the nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines which use a lever. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground Gaggia Anima Prestige Coffee Maker: Automatic Espresso Machine - https://www.coffeee.uk/products/gaggia-anima-prestige-automatic-coffee-m... inside the group head.
Pumps are generally more affordable and last longer than piston-driven machines. However, both types of machines may degrade because of excessive use and poor cleaning. They also add mechanical complexity, which can result in the cost of even the most basic models.
Certain espresso machines utilize steam pressure instead of a pump for brewing espresso. This can cause over-extraction because the boiler that produces steam also heats the water until it comes to a boil. In addition the machines often have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines employ an rotary or vibrating pump, which has a vibration model using a vibrating disc to create pressure, and rotating models that push hot water through the grounds under high speed. Both machines produce great espresso, however rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the one that heats the water to a temperature that is ideal to extract. The steam produced is then directed to the portafilter, which contains the Swan Retro Black Espresso Coffee Machine Frother - https://www.coffeee.uk/products/swan-retro-black-espresso-coffee-machine... coffee grounds. The steam is then channeled into the cup. The steam creates pressure that pushes through the grounds of the coffee. This creates a crema on the top of the espresso. This is the hallmark of a great espresso.
There are three types of espresso machines, each with a different type of pump and the temperature of the brew. There are many ways to control the brew as well as the size of the cup that can be made by the machine.
The first espresso machines were steam-types. They had only one boiler to make both steam and brew however, the pressure they could generate was low - only two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic machine that has an electric pump. When people think of espresso machines, they picture these machines. With a semi- automatic espresso machine - https://www.coffeee.uk/products/gaggia-classic-pro-espresso-machine-indu... , you must grind the beans and tamp them yourself but the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized accuracy.
The Filter
Typically, espresso machines use filters to separate the grounds of coffee when they pass through the hot water. The filter is also a vital component of the machine's temp control, as it helps prevent overheating.
A filter can also help with flavor because it allows for a longer flowering phase. This allows the beans to release their flavors and provides an opportunity to improve extraction.
It is important to remember that even the finest filter can make a bad cup of coffee. The quality of the beans and the extraction process remain crucial.
It's here that the magic takes place. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you put the portafilter, the device 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, which is then pushed through the grounds with high pressure. These types of machines tend to be cheaper and easier to maintain than pump-driven models. They are however limited to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have become more popular. They make use of an air compressor to force hot water through the ground. They are also more mobile than steam-driven electric espresso machines.