How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and a filter technology that is mind-blowing to create the coffee you love. But how exactly does it work?
Espresso is made by forcing hot water at high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.
The Group Head
The group head is the portafilter that you put in when making espresso. It distributes water into the portafilter, and controls the pressure of the extraction. There are various kinds of group head, each with their particular advantages and disadvantages. Some are designed for stability in temperature, while others are specifically designed to handle pre-infusion. Others are built to control the lever. There are even some that have a combination of features, like the E61 one, which is to be the most popular among baristas due to its ability to provide multiple benefits in one package.
As you can see in the above photo the head of the group is equipped with several notches. You place your portafilter inside these notches, and then twist the head to lock it. A gasket made of rubber is placed inside the notches, which helps create a seal as you insert your portafilter. The notches on the head permit a precise placement of the portafilter, which is vital for an even extraction.
In addition to allowing you to easily connect your portafilter, the group head is responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is always at the right level to extract the coffee. This is vital, because even a small difference in temperature can make the difference between good and excellent espresso.
The Pump
Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure needed for espresso extraction. This is different from manual piston machines that rely on a lever. The pressure builds up by removing tap water from a reservoir and pumping it through a heat exchanger before being shot through the ground coffee in the group head.
Pumps tend to be less expensive and last longer than piston-driven machines. However, both types of machines are susceptible to degrading due to overuse and poor cleaning. Pumps are also more complex mechanically, which can increase prices of even simple models.
Certain espresso machines utilize steam pressure instead of a pump in order to brew espresso. The downside is that the boiler that produces steam also raises the temperature of the water to the point of boiling which can cause excessive extraction. In addition these machines typically have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines make use of either a rotary or vibration pump, which has a vibration model using a rotating disc that generates the pressure and the rotary model pushing hot water through the grounds at high speed. Both types of machine can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what heats the water to the right temperature for extraction. The steam that is produced gets to the portafilter which contains the espresso coffee grounds. It is then poured into the cup. During this process the steam causes enough pressure to push the grounds of coffee through. This produces a layer of crema that is then poured over. This is one of the hallmarks of a good espresso.
There are three types of espresso makers, and they differ in the type of pump they use and the degree of heat that the coffee is. There are various ways to control the amount of brew, as well as the size of cup that can be made by the machine.
The first espresso machines were steam-based. The earliest espresso machines were steam types. The coffee tasted bitter and burned. This is the reason why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso machine is a semiautomatic with an electric pump. This is what people envision when they think of an espresso maker. With a semi-automatic machine, you must grind the beans and tamp them by hand. The pump is able to regulate the flow of water and pressure. This is an excellent compromise between human touch and the mechanised consistency.
The Filter
Typically, espresso machines employ a filter to separate out the grounds of coffee as they move through the hot water. The filter is also a vital part of the machine's temperature control, since it stops overheating.
It also enhances flavor, as a filter allows for a longer bloom time. This helps the beans to let their nuances out and provides an opportunity for a better extraction.
However, it is important to remember that even a good filter could result in a bad cup of coffee as the quality of the beans and extraction is important.
This is where the magic happens, and it's what makes an espresso really taste good. The grouphead, often referred to as the brew head, is where the portafilter (the device you put the ground coffee into) is located when you're making espresso.
In read here -driven espresso machine hot water is heated in an airtight container to produce steam, which then pushes the hot water through the grounds under high pressure. These kinds of machines are typically less expensive and simpler to maintain than pumps-driven models. They are however limited for creating the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have been gaining popularity. They utilize an air compressor to push hot water through the ground. They are also more mobile than steam-driven electric espresso machines.