How Does Machine Espresso Work?
Machine espresso uses precision pressure and amazing filter technology to make the coffee we love. How does it work exactly?
Espresso is made by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee, however the main difference lies in the pressure.
The Head of the Group
The group head is the portafilter you put in when making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, while others are designed to control the lever. There are even some that include a mix of features, such as the E61, which is considered the classic choice among many baristas due to its capacity to provide multiple benefits in a single package.
As you can see from the picture above, the group head is fitted with a variety of notches. You place your portafilter in these notches, then twist the head to lock it. There is also a gasket of rubber that resides inside the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is vital for an accurate extraction.
In addition to allowing you easily connect your portafilter, the group head is also responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew pan and around the portafilter to ensure that it is always at the correct temperature to extract. It is important to remember that even a tiny differences can make the distinction between a decent and a excellent espresso machines uk.
The Pump
Contrary to manual piston machines which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior being pumped through the ground coffee in the group head.
Pumps tend to be more affordable and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which can increase the price of even the most basic models.
Some espresso machines home machines can eliminate the pump entirely and use steam pressure to brew espresso. This can lead to over-extraction as the boiler that produces steam also heats the water to boil. They also have to continuously rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of an rotary or a vibration pump. A vibration model makes use of an oscillating disk to create pressure, whereas the rotating model pushes hot water through the ground at a high speed. Both machines can make excellent espresso however rotary machines tend to be more stable, quieter and less likely to fail.
The Boiler
The boiler is the component that heats water to an ideal temperature to extract. The steam produced will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. It is then pumped into the cup. The steam creates enough pressure to push the grounds of coffee through. This creates a foam on the top of the espresso. This is one of the hallmarks of a good espresso.
There are three types of espresso coffee maker makers. They differ in the type of pump they employ and how hot the coffee is. There are different ways in which the brew can be controlled, as well as the dimensions of the cup the machine can produce.
The first espresso machines were steam-type. They had one boiler to create both steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure at the most. This resulted in the coffee tasting bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you need to grind the beans and tamp them by hand. The pump provides regulated water flow and pressure. This is a fantastic solution that combines human control with mechanized consistency.
The Filter
Espresso machines typically have filters that separate the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temperature control, since it stops overheating.
It also aids in flavor, as it allows for a more prolonged bloom time. This helps the beans release their nuances and gives the chance for better extraction.
However, it is important to keep in mind that even a high-quality filter can produce a bad cup of coffee, because the quality of the beans and extraction are 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 put the portafilter, the device which you put the grounds of coffee into when making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight container to make steam. The steam then pushes hot water through the grounds of coffee at high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability 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, espresso home machine machines driven by a compressed air compressor have become increasingly popular. They utilize an air compressor to push hot water through grounds and are much more portable than steam-driven electric machines.