How Does Machine Espresso Work?
The machine espresso utilizes precision pressure, and filtering system that is awe-inspiring to create the coffee you enjoy. What exactly is it?
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 primary difference.
The Head of the Group
As the name suggests the group head is the place you put your portafilter in when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the extraction. There are a variety of types of group heads, each with their unique advantages and disadvantages. Some are designed to provide stability in temperature, while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some have a combination, like the E61. This is a preferred choice for baristas because it offers multiple benefits in one package.
As you can see in the above photo the group head is made up of numerous notches that you can put your portafilter, then twist it manually to secure it. There is also a gasket made from rubber that is a part of the notches and helps to create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact placement of the portafilter, which is vital to ensure an even extraction.
In addition to allowing you to effortlessly insert your portafilter the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket and around the portafilter, making sure that it's always at the correct temperature for extraction. It is important to remember that even a small difference can make the difference between a good and great espresso.
The Pump
The motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines that rely on levers. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee in the group head.
Pumps are typically more affordable and last longer than piston-driven machines. However, both kinds of machines can degrade due to excessive use and insufficient cleaning. Pumps are also more complicated mechanically, and can add to the price of even the most basic models.
Some espresso machines eliminate the pump entirely and employ steam pressure to create espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of the water to the point of boiling and can result in excessive extraction. The machines must also constantly rebuild their pressure between cups. This requires energy and time.
A large majority of espresso machines employ either a vibration or rotary pump. A vibration model uses a rotating disk to generate pressure, whereas a rotary model pushes hot water through the ground at high speed. Both machines produce great espresso however rotary machines tend to be more quiet, durable and less likely to break down.
The Boiler
The boiler is what will heat the water to the perfect temperature to extract. The steam that is produced reaches the portafilter containing the ground espresso and gets funnelled down into the cup. During this process, steam creates pressure to push through the grounds of the coffee. This results in a layer crema on top. This is a sign of a great espresso.
There are three kinds of espresso machines, each having a different type of pump and brew temperature. There are a variety of ways that the brew may be controlled, as well as the size of the cup the machine is capable of making.
The first espresso machines were steam-type. The first espresso machines were steam types. This led to the coffee tasting burnt and bitter. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most well-known espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans yourself however the pump controls the flow of water and pressure. This is a fantastic solution that combines human control with mechanized reliability.
The Filter
Typically, espresso machines employ filters to separate the grounds of coffee as they move through the hot water. The filter is also an essential component of the machine's temp control, as it helps prevent overheating.
A filter also improves flavor since it allows for a longer flowering period. This allows the beans to release their nuances and gives an opportunity to improve extraction.
However, it is important to keep in mind that even a great filter could result in a bad cup of coffee, since the quality of the beans and extraction are important.
It's here that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you put the portafilter, the device which you put the grounds of your coffee into while making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then pushes hot water through the grounds of coffee under high pressure. These kinds of machines are usually less expensive and simpler to maintain than pump-driven models. They are however limited in their ability for creating the ideal conditions for brewing since 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 more mobile than electric steam-driven espresso machines.