How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. How exactly does it work?
In order to make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However it is the pressure that makes the main difference.
The Group Head
The name implies the group head is where you insert your portafilter when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are various kinds of group head, each with their distinct advantages and drawbacks. Some are focused on temperature stability, while others on pre-infusion features, and others are designed to control the lever. Some come with a combination of both, such as the E61. This is a preferred choice for baristas as it provides a variety of advantages in one package.
As you can see in the photo above The group head features many notches in which you can place your portafilter and twist it manually to secure it. There is also a gasket made from rubber which is located inside the notches and helps create the seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is essential for an even extraction.
The group head not only allows you to place your portafilter easily, but it also maintains an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket, ensuring that the temperature is always at the right level for extraction. This is important, as just a few degrees could make the difference between good and excellent espresso.
The Pump
Unlike manual piston machines, that use a lever to pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure required to extract espresso. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground coffee inside the group head.
Pumps are typically more affordable and last longer than piston-driven machines. However, commercial espresso machine of machines can deteriorate because of excessive use and inadequate cleaning. Pumps are also more complex mechanically, which could increase the cost of even the simplest models.
Some espresso machines use steam pressure instead of a pump to brew espresso. This can result in over-extraction because the boiler that produces steam also heats the water to boil. The machines also need to continually rebuild their pressure between cups. This requires energy and time.
A majority of espresso machines use either a rotary or vibration pump, which has a vibration model that uses a vibrating disc to create pressure, and a rotary model pushing hot water through the grounds under high speed. Both models are capable of producing excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the one that will heat the water to the ideal temperature for extraction. The resultant steam then reaches the portafilter that contains ground espresso beans and is then pumped into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This creates a crema on top of the espresso. This is one of the hallmarks of a good espresso.
There are three types of espresso makers, which differ in the type of pump they employ and how hot the coffee is. There are different ways to control the brew as well as the size of cup that can be made by the machine.
The earliest espresso machines were steam type. The earliest espresso machines were steam-type machines. The coffee tasted bitter and burned. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most popular espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they think of these machines. Semi-automatic machines require you to grind and tamp your beans yourself, but the pump regulates the water flow and pressure. This is a great compromise between the human touch and the mechanised accuracy.
The Filter
Espresso machines typically use filters that separate the grounds of the coffee from 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 a filter allows for a more prolonged bloom time. This allows the beans to release their nuances, and also allows for better extraction.
However, it is important to keep in mind that even a great filter can make a terrible cup of coffee, because the quality of the beans and extraction are vital.
It's in this area that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy which you put the grounds of coffee into when making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through grounds of coffee under high pressure. These kinds of machines are usually cheaper and easier to maintain than pumps-driven models. They are however limited in their ability for creating 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 years, espresso machines driven by a compressed air pump have become increasingly popular. They make use of an air compressor to push hot water across the ground, and are more mobile than steam-driven electric espresso machines.
