How Does Machine Espresso Work?
Machine espresso uses precision pressure and mind-blowing filter technology to create the perfect cup of coffee. How exactly does it work?
Espresso is produced 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 Head of the Group
The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the extraction. There are a variety of types of group head, each with their own advantages and disadvantages. Some focus on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. Some contain a variety of features, like the E61, which is the standard choice for many baristas due to its ability to offer multiple perks in one package.
As you can see in the image above the group head comes with numerous notches that you can put your portafilter, then twist it manually to lock it in. A gasket made of rubber is positioned inside the notches to help make a seal when you insert your portafilter. The notches on the head permit an exact positioning of the portafilter which is essential to ensure a consistent extraction.
The group head not only allows you to place your portafilter easily but also maintains the temperature at a constant level. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is vital, because just a few degrees could make the difference between excellent and great espresso.
The Pump
Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure needed to extract espresso. This differs from manually operated piston machines that employ a lever. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines are susceptible to degrading due to overuse and inadequate cleaning. Pumps are also more complicated mechanically, which can increase the price of even the simple models.
Some espresso machines remove the pump entirely and make use of steam pressure to make espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of water to the point of boiling which can cause over-extraction. In addition the machines often have to restore their pressure between cups, which takes time and energy.
A majority of espresso machines utilize an rotary or a vibration pump. A vibration model uses the vibrating disk to create pressure, while the rotating model pushes hot water through the ground at a rapid speed. Both machines can make great espresso, but rotary machines are quieter, more durable and less likely to break down.
The Boiler
The boiler will heat the water to the ideal temperature to extract. The steam that is produced reaches the portafilter, which holds the espresso grounds. The steam is then channeled into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This creates a layer crema that is then poured over. This is one of the main characteristics of a good espresso.
There are three types of espresso makers, and they differ in the kind of pump they use and how hot the espresso is. There are different ways to control the strength of the brew and the size of cup that can be produced by the machine.
stay with me were steam-based. The earliest espresso machines were steam-type machines. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic machine 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 an excellent compromise between human control and mechanised reliability.
The Filter
Espresso machines typically use a filter that separates the coffee grounds from the hot water. The filter is also an essential element of the temperature control system as it prevents the machine from overheating.
A filter also improves flavor since it allows for the beans to flower for a longer period of time. This allows the beans to let their nuances out and provides an opportunity for a better extraction.
It is important to remember that even the best filter can make a bad cup of coffee. The quality of the beans, and the extraction, remain vital.
It's in this area that the magic occurs. This is what makes espresso taste so good. The grouphead, often called the brew head, is the place where the portafilter (the device you put the ground coffee into) is placed when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. Steam then pushes the hot water through the grounds at high pressure. These types of machines are generally less expensive and simpler to maintain than pumps-driven models. They are however limited in their ability to create the perfect brewing conditions as 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 compressor have become increasingly popular. They use an air compressor to force hot water through the ground and are much more mobile than electric steam-driven espresso machines.