How Does Machine Espresso Work?
The machine espresso utilizes precision pressure, and a filter technology that is mind-blowing to create the coffee you enjoy. What exactly does it work?
Espresso is created by forcing hot water under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the major difference.
The Head of the Group
The group head is the portafilter that is inserted when you are making espresso. It distributes water into the portafilter, and regulates the pressure of extraction. There are many different kinds of group heads, each with their particular advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. There are some that come with a range of features, like the E61, which is the most popular choice among baristas because of its ability to offer multiple benefits in one package.
As you can see from the photo above the group head is equipped with several notches. The portafilter is placed in these notches, then turn the head around to secure it. There is also a gasket made from 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 essential to ensure a consistent extraction.
The group head not only allows you to place your portafilter easily however, it also keeps the same temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is constant to extract the coffee. It is crucial to keep in mind that even a slight difference can make the difference between a good and great espresso.
The Pump
Motorized pumps in espresso machines that rotate provide the nine atmospheric bars of pressure required to extract espresso. This differs from manual piston machines which use a lever. The pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee inside the group head.
Pumps are generally less expensive than piston-driven machines and tend to last longer, but both types of machine can become damaged due to excessive use and poor cleaning. They also add mechanical complexity which can result in costly prices for even the simplest models.
Some espresso machines make use of steam pressure instead of a pump to brew espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of water to the point of boiling and can result in over-extraction. Additionally the machines often have to restore their pressure between cups, which takes time and energy.
A majority of espresso machines use either a rotary or vibration pump, with a vibration model that uses a vibrating disc to create the pressure and the rotary model pushing hot water through the grounds at high speed. Both machines can produce excellent espresso, however rotary machines are more stable, quieter and less likely to fail.
The Boiler
The boiler is used to heat the water to the right temperature for extraction. The resultant steam then reaches the portafilter, which contains ground espresso beans and is then pumped into the cup. During this process the steam causes enough pressure to push the grounds of the coffee through. This results in a layer crema that is then poured over. This is a sign of a good espresso.
There are three types of espresso makers. They differ in the type of pump they use and how hot the coffee is. There are many ways to control the brew as well as the size of the cup that can be made by the machine.
The earliest espresso machines were steam types. The earliest espresso machines were steam types. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most commonly used espresso machine is a semiautomatic that has an electric pump. This is what people envision when they think of an espresso maker. If you have a semi-automatic machine you grind the beans and then tamp them by hand. However, the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized consistency.
The Filter
Espresso machines typically use filters that separate the grounds of the coffee from hot water. The filter is also an essential element of the temperature control system, as it keeps the machine from overheating.
It also helps with flavor, since a filter can allow for a longer bloom phase. This helps the beans to release their nuances and gives an opportunity for a better extraction.
However, it is important to remember that even a great filter can make a terrible cup of coffee, since the quality of the beans and extraction are essential.
This is where the magic happens, it's the thing that makes espresso taste great. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy that you use to put the grounds of your coffee into when making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam, which is then pushed through the grounds at a high pressure. These types of machines are usually less expensive and simpler to maintain than pump-driven models. They are however limited for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. retro espresso machine requires 9-10 bars.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air-compressor to force hot water through the ground, and are more mobile than steam-driven electric espresso machines.