Ten Things You Learned In Kindergarden To Help You Get Started With Machine Espresso
Ten Things You Learned In Kindergarden To Help You Get Started With Machine Espresso
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How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it that makes it work?
Espresso is created by forcing hot water under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the major difference.
The Group Head
The name implies the group head is the place you place your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure of the resulting 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 of features, such as the E61, which is the most popular choice among baristas because of its ability to offer multiple benefits in one package.
As you can see in the photo above the group head is made up of several notches where you place your portafilter and then twist it with your hands to lock it in. There is also a gasket made of rubber that is a part of the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of the portafilter. This is essential for an efficient extraction.
In addition to allowing you to easily insert your portafilter, the group head is responsible to maintain an even temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is always at the right level to extract the coffee. This is important because just a few degrees could be the difference between a good and excellent espresso.
The Pump
Motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure that is required to extract espresso. This differs from manual piston machines that rely on a lever. 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 models, and they tend to last longer, however both types of machines may degrade with overuse and insufficient cleaning. They also increase the complexity of mechanical systems that can lead to an expensive price for even the simplest models.
Some espresso machines can eliminate the pump completely and instead make use of steam pressure to make espresso. The drawback is that the boiler that produces steam also raises the temperature of the water until it reaches boiling which can cause excessive extraction. The machines must also continually rebuild their pressure between cups. This takes 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, while the circular model pushes hot liquid through the ground at a rapid speed. Both types of machine are capable of producing excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the part that heats water to an optimal temperature to extract. The steam that is produced reaches the portafilter, which contains the ground espresso coffee, and is then funneled down into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This results in a whipped-up the top of the espresso. This is a sign of a good espresso.
There are three kinds of espresso machines, each having different pumps and the temperature of the brew. There are various ways in which the brew can be controlled as well as the size of the cup that the machine can produce.
The first espresso machines were steam-types. They had one boiler to espresso machines for home create both steam and brew, but the pressure they could create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most common espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you need to grind the beans and tamp them yourself but the pump provides regulated water flow and pressure. This is a great compromise between the human touch and mechanized accuracy.
The Filter
Espresso machines typically use filters that separate the grounds of coffee from hot water. The filter is also an essential component of the temperature control system, as it prevents the machine from overheating.
A filter also improves flavor because it allows for a longer flowering phase. This allows the beans to release their flavors, and allows for a better extraction.
It is important to remember that even the most efficient filter can make a bad cup of coffee. The quality of the beans and the extraction, remain vital.
This is where the magic happens, it's the thing that makes espresso taste great. The grouphead, sometimes called the brew head, is where the portafilter (the device you put the coffee grounds into) is placed when making espresso.
Steam-driven espresso machines make use of hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water into the grounds of coffee at high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. However, they are limited in their capacity to create the perfect brewing conditions because they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.
In recent times, espresso machines powered by compressed air-pump have become increasingly popular. They use an air-compressor to force hot water into the ground and are more mobile than steam-driven electric espresso machines.