How Does Machine Espresso Work?
Machine
espresso machine black friday makes use of precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. How does it work exactly?
Espresso is produced by pushing hot water under 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 that you insert when brewing espresso. It disperses water in the portafilter, and regulates the pressure of extraction. There are various kinds of group head each with its unique advantages and drawbacks. Some are specifically designed for stability of temperature while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some include a combination like the E61. This is a popular choice among baristas since it provides multiple benefits in one package.
As you can see in the photo above the group head comes with many notches in which you can put your portafilter, then twist it with your hands to secure it. There is also a gasket made of rubber which is located inside the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches on the head permit a precise position of the portafilter which is crucial to ensure a consistent extraction.
The group head not only allows you to insert your portafilter easily however, it also keeps the same temperature. It does this by cycling hot water through the brew pan and around the portafilter, making sure that it's always at the right temperature for extraction. It is important to realize that even a tiny deviation can make the difference between a great and a great espresso.
The Pump
The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure needed for espresso extraction. This is different from manual piston machines that use levers. This pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.
Pumps tend to be cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade due to excessive use and poor cleaning. They also increase the complexity of mechanical systems that can lead to costly prices for even the most basic models.
Some espresso machines eliminate the pump completely and instead utilize steam pressure to make espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of water to boiling and can result in over-extraction. These machines also have to constantly rebuild their pressure in between cups. This requires energy and time.
A majority of espresso machines use an rotary or vibrating pump, with a vibration model that uses a vibrating disc that generates the pressure and a rotary model pushing hot water through the grounds under high speed. Both machines can produce excellent espresso, but rotary machines are more quiet, durable and less likely to fail.
The Boiler
The boiler is the element which heats the water to the ideal temperature to extract. The resultant steam then reaches the portafilter which holds the ground espresso coffee and is then funneled down into the cup. The steam causes enough pressure to push the grounds of coffee through. This creates a crema on the top of the espresso. This is one of the hallmarks of a good espresso.
There are three different types of espresso machines, each with different pumps and the temperature of the brew. There are many ways to control the strength of the brew and the size of cup that can be produced by the machine.
The earliest
compact espresso machine machines were steam types. They had one boiler to create 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 Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most commonly used espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine you have to grind the beans and tamp them yourself but the pump is able to regulate the flow of water and pressure. This is a great compromise between the human touch and the mechanised accuracy.
The Filter
Typically, espresso machines employ filters that separate the grounds of coffee as they move through the hot water. The filter is also a vital part of the temperature control system, as it prevents the machine from overheating.
It also enhances flavor, since a filter allows for a more prolonged bloom phase. This lets the beans let their nuances out, and improves extraction.
However, it is important to remember that even a good filter can make a terrible cup of coffee, since the quality of the beans and extraction is vital.
It's in this area that the magic takes place. This is what makes espresso taste so delicious. The grouphead, also called the brew head, is where the portafilter (the container you place the ground coffee in) is placed when making espresso.
Steam-driven espresso machines make use of hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through grounds of the coffee under pressure. These kinds of machines are usually cheaper and easier to maintain than pump-driven models. However, they are limited in their capacity to create the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires
9 bar espresso machine-10 bar.
In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to force the hot water through the grounds, and are far more portable than steam-driven electric machines.