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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. What exactly does it work?

Espresso is produced by pushing hot water under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.

The Head of the Group

As the name implies, the group head is the place you place your portafilter while brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are numerous kinds of group heads each with distinct advantages and disadvantages. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Others are built to control the lever. Some have a combination of features, such as the E61, which is the standard choice for many baristas due to its ability to provide multiple benefits in one package.

As you can see in the image above, the group head has several notches to put your portafilter, then twist it manually to secure it. There is also a rubber gasket which is located inside the notches and helps to create an airtight seal after inserting your portafilter into the machine. The notches on the head permit an exact location of the portafilter which is vital for an efficient extraction.

In addition to allowing you effortlessly insert your portafilter the group head is responsible to maintain an even temperature. This is achieved 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 note that even a few degree variation can mean the difference between a great and a excellent espresso.

The Pump

The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines that rely on levers. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven machines, and tend to last longer, however both types of machines can degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, and can add to the price of even the simple models.

Certain espresso machines eliminate the pump entirely and make use of steam pressure to make espresso. This can cause over-extraction because the boiler that makes steam also heats the water to boil. In addition the machines often have to restore their pressure between cups, which requires time and energy.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model utilizes a rotating disk to generate pressure, whereas a rotary model pushes hot water through the best ground coffee for espresso machine at a rapid speed. Both models are capable of producing excellent espresso, but the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is the element that heats water to the optimal temperature to extract. The steam created reaches the portafilter, which holds the espresso grounds. It is then funneled into the cup. In this process, the steam creates pressure and pushes through the coffee grounds. This creates a layer crema that is then poured over. This is the hallmark of a great mini espresso machine.

There are three types of espresso machines, each having distinct pumps and the temperature of the brew. There are various 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-type. The earliest espresso machines were steam types. This resulted in the coffee tasting bitter and burnt. This is the reason Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most common espresso machine is a semiautomatic one with an electric pump. These are the things people think of when they think of an espresso maker. With a semi-automatic machine, you must grind the beans and tamp them yourself but the pump provides regulated water flow and pressure. This is an excellent compromise between human touch and the mechanized consistency.

The Filter

Typically, espresso machines employ filters to separate 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.

A filter also helps with flavor since it allows for a longer flowering phase. This helps the beans to release their flavor and gives an opportunity for a better extraction.

However it is crucial to remember that even a great filter could result in a bad cup of coffee, as the quality of the beans and extraction is still crucial.

This is where the magic happens, it's the thing that makes espresso taste great. The grouphead, also referred to as the brewhead, is where the portafilter (the thingy you put the coffee ground into) is placed when making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. Steam is then pushed through the grounds at high pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. However, they are not as efficient in their ability to produce the ideal conditions for brewing because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.

In recent years, commercial espresso machine machines driven by a compressed air compressor have become increasingly popular. They use an air compressor to force the hot water through the grounds, and are far more portable than steam-driven electric espresso maker machines.