How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to make the coffee we love. But how exactly does it work?
In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Head of the Group
As the name implies the group head is where you place your portafilter while making espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure that results from the extraction. There are numerous kinds of group heads, each with its own advantages and disadvantages. Some are focused on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. There are some that come with a range of features, such as the E61 that is the classic choice among many baristas due to its ability to offer multiple benefits in one package.
As you can see in the image above, the group head is fitted 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 to help create a seal when you insert your portafilter. The notches permit precise placement of your portafilter. This is crucial for a consistent extraction.
The group head is not just able to allow the portafilter to be inserted easily however it also keeps the same temperature. It does this by cycling hot water through the brew pan and around the portafilter, making sure that it's always at the correct temperature to extract. It is important to realize that even a few degree variation can mean the difference between a good and a great espresso.
The Pump
The motorized pumps in espresso machines rotary provide nine atmospheric bar pressure needed to extract espresso. This differs from manually operated piston machines that employ levers. The pressure is created 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 machine can become damaged due to excessive use and poor cleaning. They also increase the complexity of mechanical systems, which can result in costly prices for even the most basic models.
Certain espresso machines do away with the pump completely and instead use steam pressure to brew espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling which can cause excessive extraction. In addition these machines are often required to rebuild their pressure between cups, which takes time and energy.
Many espresso machines use either a vibration or rotary pump. A vibration model uses an oscillating disk to create pressure, while a circular model pushes hot liquid through the ground at a high speed. Both models can make excellent espresso, but rotary machines espresso are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats the water to the optimal temperature to extract. The steam that is produced reaches the portafilter which holds the ground espresso coffee and is then pumped down into the cup. During this process, the steam creates pressure and pushes through the coffee grounds. This results in a crema on top of the espresso. This is a hallmark of a good espresso.
There are three types of espresso machines, each having different pumps and the temperature of the brew. There are various ways to control the brew as well as the size of the cup that can be made by the machine.
The first espresso machines were steam-type. The first espresso machines were steam types. This resulted in the coffee and espresso maker tasting burnt and bitter. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso machine is a semiautomatic one with an electric pump. These are the images people have when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans on your own, but the pump regulates the flow of water and pressure. This is an excellent solution that combines human control with mechanized reliability.
The Filter
Typically, espresso machines employ filters that separate the grounds of coffee when they pass through the hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating.
A filter can also help with flavor since it allows for the beans to flower for a longer period of time. This allows the beans to release their nuances, and improves extraction.
It is important to keep in mind that even the best filter can make a bad cup of coffee. The quality of the beans, as well as the extraction, are still very important.
This is where the magic happens, it's what makes an espresso really taste great. The grouphead (also known as the brewhead) is where you place the portafilter, which is the thingy which you put the coffee grounds in, when making espresso coffee machine with milk frother.
In the 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 kinds of machines are typically less expensive and simpler to maintain than pump-driven models. They are however limited in their ability to create the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water into the grounds and are significantly more portable than electric steam-driven machines.