How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and incredible filter technology to produce the coffee we love. How does it work exactly?
To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However it is the pressure that makes the main difference.
The Head of the Group
The name implies, the group head is the place you put your portafilter in when making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure of the extraction. There are many different types of group heads each with their own advantages and drawbacks. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some come with a range of features, such as the E61, which is the standard choice for many baristas due to its ability to provide multiple benefits in one package.
As you can see in the above photo, the group head is equipped with several notches. It is possible to place your portafilter into these notches and twist the head to lock it. A gasket made of rubber is placed in the notches to make a seal when you insert your portafilter. The notches on the head allow for a precise placement of the portafilter, which is vital for a consistent extraction.
Apart from allowing you easily connect your portafilter, the group head is also responsible to maintain an even temperature. It does this by cycling hot water through the brew container and around the portafilter, ensuring that it's always at the right temperature for extraction. It is important to realize that even a tiny variation can mean the difference between a good and a excellent espresso.
The Pump
The motorized pumps that are used in espresso machines that rotate provide the nine atmospheric bars of pressure required for espresso extraction. This differs from manual piston machines that use levers. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be cheaper than piston-driven machines and tend to last longer. However, both types of machine can get damaged through overuse and lack of cleaning. They also create mechanical complexity and can lead to a high price tag on even the simplest models.
Some espresso machines make use of steam pressure instead of a pump to brew espresso. This can cause over-extraction here because the boiler that produces steam also heats the water until it comes to a boil. Additionally the machines often have to restore their pressure between cups, which takes time and energy.
Many espresso machines utilize a vibration or rotary pump, with a vibrating model using a vibrating disc that generates the pressure and an rotary model that pushes hot water through the grounds under high speed. Both machines can produce excellent espresso, but rotary machines are quieter, more durable and less likely to break down.
The Boiler
The boiler is the element that heats the water to the optimal temperature to extract. The resultant steam then reaches the portafilter containing ground espresso beans and gets funnelled down into the cup. The here steam is able to create enough pressure to push the coffee grounds through. This results in a layer of crema that is then poured over. This is a sign of a great espresso.
There are three kinds of espresso makers. They differ in the type of pump they use and how hot the espresso is. There are different ways that the brew can be controlled and the size of the cup that the machine is capable of making.
The first espresso machines were steam-based. They had only one boiler to make both steam and brew, however the pressure they were able to create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso machine is a semiautomatic with an electric pump. These are the images people have when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and pressure. This is a great compromise between the human touch and mechanized consistency.
The Filter
Espresso machines typically have filters that separate the grounds of the coffee from hot water. The filter is also an essential part of the temperature control system because it stops the machine from overheating.
It also improves flavor, since a filter can allow for a longer bloom phase. This allows beans to release their flavor and gives an opportunity for better extraction.
It is important to keep in mind that even the finest filter can make a bad cup of coffee. The quality of the beans and the extraction, are still very important.
This is where the magic happens, and it's what makes espresso taste great. The grouphead, often called the brewhead, is where the portafilter (the here thing you put the ground coffee into) is placed here when making espresso.
Steam-driven espresso machines make use of hot get more info water that is heated in an airtight container to produce steam. The steam then pushes hot water into the grounds of the coffee under pressure. They are less expensive and easier for the user to maintain than pumps-driven models. However, they are limited in their capacity to create the ideal conditions for brewing since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the grounds and are significantly more portable than steam-driven electric machines.