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How Does Machine Espresso Work?

The machine espresso utilizes precise pressure and filter technology that is awe-inspiring to make the coffee you enjoy. What exactly does it work?

To make an espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.

The Head of the Group

As the name suggests, the group head is the place you place your portafilter when brewing espresso. It disperses water into the portafilter, and then regulates the pressure during the extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some focus on temperature stability, some on pre-infusion features, and others are designed to control the lever. Some are a combination, like the E61. This is a preferred choice for baristas because it offers multiple advantages in one package.

As you can see from the photo above the head of the group is equipped with several notches. It is possible to place your portafilter in these notches, then turn the head around to secure it. There is also a gasket made of rubber that is a part of the notches and helps create a seal when you insert your portafilter into the machine. The notches permit precise placement of your portafilter. This is crucial to ensure a consistent extraction.

The group head is not just able to allow the portafilter to be inserted easily however, it also keeps an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is always at the right level to extract the coffee. It is important to remember that even a few degree variation can mean the difference between a good and a excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure that are required for espresso extraction. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground Smeg 146875 Coffee Machine with Adjustable Temperature in the group head.

Pumps tend to be less expensive than piston-driven models, and they tend to last longer, however both types of machines could become damaged due to excessive use and poor cleaning. They also add mechanical complexity and can lead to an expensive price for even the simplest models.

Some espresso machines make use of steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since the boiler that produces steam also heats the water to boil. The machines must also constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines utilize the rotary or vibration pump, with a vibrating model that uses a vibrating disc to create pressure and the rotary model pushing hot water through the grounds under high speed. Both machines can make great espresso, but rotary machines are more stable, quieter and less likely to fail.

The Boiler

The boiler is the element that heats the water to the optimal temperature for extraction. The resultant steam then reaches the portafilter, which contains the ground espresso coffee, and is then pumped down into the cup. The steam is able to create enough pressure to push the grounds of the coffee through. This results in a crema on the top of the espresso. This is one of the main characteristics of a good espresso and filter coffee machine (My Source).

There are three types of espresso makers, and they differ in the type of pump they employ and the degree of heat that the brew is. There are different ways to control the brew as well as the size of cup that can be made by the machine.

The first espresso machines were steam-types. The earliest espresso machines were steam types. The coffee tasted bitter and burned. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic machine you need to grind the beans and then tamp them by hand. However, the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human touch and mechanized consistency.

The Filter

Typically, espresso machines employ a filter to separate out the coffee grounds as they pass through the hot water. The filter is also a crucial component of the temperature control system as it prevents the machine from overheating.

It also aids in flavor, since a filter allows for a longer bloom time. This allows the beans to let their nuances out, and improves extraction.

It is important to remember that even the most efficient filter can make a bad cup of coffee. The quality of the beans, and the extraction process are still very important.

This is where the magic happens. It's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you place the portafilter, the device which you put the grounds of your coffee into when making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through grounds of coffee under high pressure. These machines are less expensive and easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They use an air-compressor to force hot water into the ground and are much more mobile than steam-driven electric espresso machines.