How Does Machine Espresso Work?

Machine espresso uses precision pressure and amazing filter technology to make the perfect cup of coffee. What exactly is it that makes it work?

To make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.

The Group Head

The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the extraction. There are a variety of types of group heads, each with their particular advantages and disadvantages. Some are specifically designed for the stability of temperature while some are specifically designed to handle pre-infusion. Others are made to control the lever. Some are a combination, like the E61. This is a favorite among baristas since it provides multiple advantages in one package.

As you can see in the image above, the group head has many notches in which you can place your portafilter and then twist it by hand to secure it. There is also a gasket made from rubber that is a part of the notches and helps create a seal when you insert your portafilter into the machine. The notches allow for precise placement of your portafilter. This is crucial to ensure an accurate extraction.

The group head does not just allow the portafilter to be inserted easily but also maintains the temperature at a constant level. It does this by circulating hot water through the brew basket and around the portafilter, ensuring that it is always at the correct temperature to extract. It is important to remember that even a few degree variation can mean the difference between a good and excellent espresso.

The Pump

Motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines that use levers. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically more affordable and last longer than piston-driven machines. However, both types of machines may degrade because of excessive use and inadequate cleaning. They also increase the complexity of mechanical systems and can lead to costly prices for even the simplest models.

Some espresso machines make use of steam pressure instead of a pump to brew espresso. This can lead to over-extraction as the boiler that makes steam also heats the water until it comes to a boil. In addition these machines typically have to rebuild their pressure between cups, which requires time and energy.

Many espresso machines employ a vibration or rotary pump, which has a vibration model using a vibrating disc to create the pressure, and a rotary model pushing hot water through the grounds at high speed. Both models are capable of producing excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the one that heats the water to a temperature that is ideal to extract. The resulting steam reaches the portafilter which holds the ground espresso coffee, and is then pumped down into the cup. During this process, steam creates pressure that pushes through the coffee grounds. This results in a crema on top of the espresso. This is a sign of a great Breville One-Touch Espresso And Latte Machine: Shop Now!.

There are three different types of espresso machines, each with distinct pumps and the temperature of the brew. There are various ways in which the brew can be controlled, as well as the size of the cup the maker can create.

The first espresso machines were steam-types. They used a single boiler to make both brew and steam, but the pressure they could create was minimal - two bars of atmospheric pressure, at most. This led to the coffee tasting burnt and bitter. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most well-known espresso maker is a semi-automatic machine that has an electric pump. This is what people envision when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the flow of water and pressure. This is a perfect compromise between human control and mechanised reliability.

The Filter

Typically, espresso machines have filters that separate the grounds of the coffee as they go through the hot water. The filter is also an essential element of the machine's temperature control, since it helps to prevent overheating.

A filter can also help with flavor, as it permits a longer flowering period. This allows the beans to release their flavor and gives an opportunity for better extraction.

It is important to remember that even the most efficient filter could result in a poor cup of coffee. The quality of the beans and the extraction, are still very important.

It's here that the magic occurs. This is what makes espresso taste so delicious. The grouphead (also called the brewhead) is where you put the portafilter - the thingy used to place the coffee grounds into, when making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. This is then pushed through the grounds with high pressure. These types of machines are usually less expensive and simpler to maintain than pumps-driven models. They are however limited for creating the ideal 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 electric steam-driven espresso machines.