How Does Machine Espresso Work?
The machine espresso makes use of precise pressure, as well as a filtering system that is awe-inspiring to create the coffee you love. What exactly is it that makes it work?
To make an espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the primary difference.
The Group Head
The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are a variety of group heads each with its own advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some have a combination, such as the E61. This is a preferred choice for baristas due to the fact that it has multiple advantages in one package.
As you can see from the above photo the group head is fitted with a variety of notches. You can place your portafilter into these notches and turn the head around to secure it. There is also a gasket made from rubber in the notches, which helps create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of the portafilter. This is crucial for an even extraction.
The group head not only allows you to place your portafilter easily however it also keeps an even temperature. It does this by circulating hot water through the brew pan and around the portafilter to ensure that it is always at the correct temperature for extraction. It is important to remember that even a tiny variation can mean the difference between a good and a great espresso.
The Pump
In contrast to manual piston machines which rely on a lever to pressurize water, rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure that are required to extract espresso. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.
Pumps tend to be cheaper than piston-driven models, and they tend to last longer, however both types of machines may become damaged due to excessive use and poor cleaning. They also create mechanical complexity, which can result in costly prices for even the most basic models.
Some espresso machines make use of steam pressure instead of a pump for brewing espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling which can cause over-extraction. Additionally the machines often have to rebuild their pressure between cups, which requires time and energy.
A majority of espresso machines use the rotary or vibration pump, which is a vibration model that uses a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds under high speed. Both machines can make excellent espresso however rotary machines tend to be quieter, more durable and less likely to fail.
The Boiler
The boiler is the part that heats water to an ideal temperature for extraction. The resulting steam reaches the portafilter, which contains the ground espresso and is then pumped into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This creates a layer crema that is then poured over. This is a sign of a good espresso.
There are three types of espresso makers. They differ in the type of pump they employ and the degree of heat that the coffee is. There are various ways in which the brew could be controlled as well as the size of the cup that the machine is capable of making.
The first espresso machines were steam-types. The first espresso machines were steam types. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine, you need to grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized quality.
The Filter
Espresso machines typically use filters that separate the coffee grounds from the hot water. The filter is also an essential component of the machine's temp control, since it helps to prevent overheating.
A filter also helps with flavor as it allows for the beans to flower for a longer period of time. This allows beans to release their flavors and provides an opportunity for better extraction.
However, it is important to remember that even a great filter can produce a bad cup of coffee as the quality of the beans and extraction is still vital.
This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy that you use to put the coffee grounds into, while making espresso.
Steam-driven espresso machines make use of hot water that is heated inside an airtight vessel to create steam. The steam then moves hot water through the grounds of coffee under high pressure. These types of machines are typically less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.
In recent years, compressed-air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push the hot water through the grounds, read more and are far more portable than steam-driven electric machines.