9 . What Your Parents Teach You About Machine Espresso
How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and a filtering system that is awe-inspiring to create the coffee you enjoy. What exactly does it work?
To make an espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.
The Head of the Group
The group head is the portafilter you place in the espresso maker when making it. It disperses water into the portafilter, and controls the pressure of the extraction. There are a variety of types of group head, each with their particular advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. There are some that have a combination of features, such as the E61 one, which is the classic choice among many baristas because of its ability to offer multiple benefits in a single package.
As you can see in the above image the group head is made up of numerous notches that you can put your portafilter, then twist it by hand to secure it. There is also a rubber gasket that resides inside the notches and helps to 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 crucial to ensure a consistent extraction.
In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is at the right level for extraction. This is vital, because even a few degrees can mean the difference between good and great espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure necessary for espresso extraction. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.
Pumps are generally less expensive than piston-driven machines and tend to last longer, however both types of machine can get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, and can add to the cost of even the simple models.
Some espresso machines do away with the pump entirely and make use of steam pressure to make espresso. This can result in over-extraction because the boiler that produces steam also heats the water until it comes to a boil. The machines must also continually rebuild their pressure between cups. This takes energy and time.
Many espresso machines use the rotary or vibration pump. A vibration model utilizes a rotating disk to generate pressure, whereas a rotary model pushes hot water through the ground at a rapid speed. espresso coffee machines can make excellent espresso, but rotary machines are quieter, more durable and less likely to break.
The Boiler
The boiler is the element which heats the water to the optimal temperature for extraction. The resultant steam then reaches the portafilter which holds ground espresso beans and gets funnelled down into the cup. In this process, the steam creates pressure that pushes through the grounds of the coffee. This results in a whipped-up top of the espresso. This is the hallmark of a great espresso.
There are three types of espresso machines, each with distinct pumps and the temperature of the brew. There are a variety of ways that the brew can be controlled, as well as the size of the cup that the machine can make.
The first espresso machines were steam-types. The earliest espresso machines were steam types. The coffee tasted bitter and burnt. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine, you have to grind the beans and tamp them yourself but the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human touch and mechanized consistency.
The Filter
Typically, espresso machines utilize filters that separate the grounds of the coffee as they go through the hot water. The filter is also an important part of the temperature control system, because it stops the machine from overheating.
It also helps with flavor, as it allows for a longer bloom phase. This helps the beans to release their flavors and provides an opportunity to improve extraction.
It is important to remember that even the finest filter can produce a bad cup of coffee. The quality of the beans, and the extraction, are still crucial.
It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you put the portafilter - the thingy which you put the coffee grounds into, when making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight container to make steam. The steam then pushes hot water into the grounds of coffee under high pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the ideal brewing conditions, 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 pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.