How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and mind-blowing filter technology to make the coffee we love. How exactly does it work?
Espresso is made by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.
The Head of the Group
As the name suggests the group head is where you insert your portafilter when brewing 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 disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. Some have a combination of features, such as the E61 that is the standard choice for many baristas for its ability to offer multiple perks in a single package.
As you can see from the photo above the group head is equipped with several notches. It is possible to place your portafilter in these notches, then twist the head to secure it. A gasket of rubber is situated inside the notches, which helps create a seal as you insert your portafilter. The notches on the head permit a precise placement of the portafilter, which is necessary to ensure a consistent extraction.
Aside from allowing you to easily place your portafilter in, the group head is also responsible to maintain an even temperature. It does this by cycling hot water through the brew basket and around the portafilter to ensure that it's always at the right temperature for extraction. It is important to realize that even a tiny deviation can make the difference between a
Decent espresso machine and a excellent espresso.
The Pump
The motorized pumps used in rotary
espresso capsule machine machines provide the nine atmospheric bar pressure that is required to extract
espresso capsule machine. This differs from manual piston machines which use levers. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps are typically less expensive than piston-driven machines and tend to last longer. However, both types of machine can be damaged by excessive use and inadequate cleaning. They also create mechanical complexity, which can result in an expensive price for even the most basic models.
Some espresso machines make use of steam pressure instead of a pump in order to brew espresso. This can result in over-extraction because the boiler that makes steam also warms the water to boil. The machines also need to continuously rebuild their pressure between cups. This requires energy and time.
A large majority of espresso machines employ the rotary or vibration pump. A vibration model makes use of a vibrating disk to generate pressure, whereas a circular model pushes hot liquid through the ground at a high speed. Both machines can make excellent espresso however rotary machines tend to be more quiet, durable and less likely to fail.
The Boiler
The boiler is the part that heats the water to the optimal temperature for extraction. The steam created will eventually reach the portafilter, which holds the espresso grounds. It is then poured into the cup. During this process, the steam creates pressure and pushes through the grounds of the coffee. This results in a whipped-up the top of the espresso. This is one of the hallmarks of a great espresso.
There are three different types of espresso machines, each having different types of pumps and brew temperature. There are a variety of ways to control the amount of brew, as well as the size of cup that can be made by the machine.
The first espresso machines were steam-type. The earliest espresso machines were steam types. This resulted in the coffee tasting bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso machine is a semiautomatic one with an electric pump. These are the images people have when they imagine an
barista espresso machine machine. Semi-automatic machines require you to grind and tamp the beans yourself while the pump controls the water flow and pressure. This is an excellent compromise between human touch and the mechanized consistency.
The Filter
Typically, espresso machines employ filters that separate the coffee grounds as they pass through the hot water. The filter is also a crucial element of the temperature control system as it prevents the machine from overheating.
It also enhances flavor as a filter allows for a more prolonged bloom phase. This helps the beans release their flavors and provides an opportunity to improve extraction.
However, it is important to keep in mind that even a top filter can produce a bad cup of coffee, as the quality of the beans and extraction is crucial.
This is where the magic happens, and it's what makes an espresso really taste great. The grouphead, often called the brew head, is where the portafilter (the container you place the coffee ground into) is placed when you're making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to make steam. The steam then pushes hot water through the grounds of coffee under high pressure. They are less expensive and easier for the user to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines driven 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 electric steam-driven espresso machines.