How Does Machine Espresso Work?
The machine espresso utilizes precise pressure, as well as a filtering technology that is amazing to make the coffee you enjoy. But how exactly does it work?
Espresso is made by pushing hot water 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
As the name implies the group head is the place you insert your portafilter when making espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the resulting extraction. There are various kinds of group head each with its particular advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some include 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 above photo the group head is fitted with several notches. The portafilter is placed inside these notches, and then twist the head to secure it. A gasket made of rubber is positioned in the notches to create a seal when you insert your portafilter. The notches on the head allow for a precise placement of the portafilter, which is crucial for an efficient extraction.
The group head is not just able to allow the portafilter to be inserted easily however, it also keeps a constant temperature. This is accomplished by cycling hot water around the portafilter and through the brew basin, ensuring that the temperature is always at the right level for extraction. It is crucial to keep in mind that even a few degree differences can make the distinction between a good and great espresso.
The Pump
Unlike manual piston machines, that use a lever to pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure needed to extract espresso. The pressure builds up by removing tap water from a reservoir and pumping it through a heat exchanger prior being shot through the ground coffee in the group head.
Pumps tend to be cheaper than piston-driven machines, and tend to last longer, however both types of machines can be damaged by excessive use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase the cost of even most basic models.
Some espresso machines employ steam pressure instead of a pump for brewing espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of the water until it reaches boiling and can result in excessive extraction. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy.
A large majority of espresso machines employ the rotary or vibration pump. A vibration model employs a rotating disk to generate pressure, whereas the circular model pushes hot liquid through the ground at high speed. espresso machines for home of machines are capable of producing excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what is used to heat the water to the right temperature for extraction. The resultant steam then reaches the portafilter, which contains the ground espresso and is then funneled down into the cup. During this process the steam causes enough pressure to push the grounds of the coffee through. This creates a crema on the top of the espresso. This is one of the hallmarks of a good espresso.
There are three types of espresso machines, each having distinct pumps and the temperature of the brew. There are different 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-types. The earliest espresso machines were steam types. This led to the coffee tasting burnt and bitter. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular espresso maker is a semiautomatic machine that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans yourself The pump, however, regulates the flow of water and pressure. This is a fantastic combination of human control and mechanized consistency.
The Filter
Typically, espresso machines employ a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also an essential component of the machine's temp control, as it prevents overheating.
It also improves flavor, since a filter allows for a more prolonged bloom time. This allows beans to release their flavors and provides an opportunity to improve extraction.
It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans and the extraction process remain vital.
This is where the magic happens, it's what makes espresso taste good. The grouphead (also called the brewhead) is where you place the portafilter, the thingy that you put the grounds of your coffee into when making espresso.
Steam-driven espresso machines make use of hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water into the grounds of coffee at high pressure. These kinds of machines tend to be less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their capacity to create the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars.
In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They use an air compressor to force hot water through the ground and are more mobile than steam-driven electric espresso machines.