9 . What Your Parents Teach You About Machine Espresso
How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and amazing filter technology to make the perfect cup of best coffee espresso machine. 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
The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure of the extraction. There are many different kinds of group heads, each with their particular advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. There are also some that include a mix of features, like the E61, which is considered the standard choice for many baristas for its ability to offer multiple perks in a single package.
As you can see in the photo above the group head comes with several notches where you place your portafilter and twist it by hand to secure it. There is also a gasket made of rubber in the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise positioning of the portafilter which is necessary for an efficient extraction.
The group head does not just allow you to place your portafilter easily, but it also maintains the temperature at a constant level. It does this by cycling hot water through the brew basket, and around the portafilter, ensuring that it is always at the right temperature to extract. This is vital, because even a small difference in temperature can make the difference between excellent and 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 needed to extract espresso. The pressure is built 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, but both types of machines may degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, which could increase the price of even the simpler models.
Some espresso machines do away with the pump entirely and employ steam pressure to create espresso. This can cause over-extraction because the boiler that produces steam also causes the water to boil. The machines also need to continually rebuild their pressure between cups. This takes energy and time.
A large majority of barista espresso coffee machine machines employ an rotary or a vibration pump. A vibration model makes use of an oscillating disk to create pressure, while the Rotary model pushes hot coffee through the ground at high speed. Both models can make a great espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what will heat the water to a temperature that is ideal for extraction. The steam that is produced reaches the portafilter, which holds the espresso grounds. It is then pumped into the cup. During this process, steam creates pressure to push through the grounds of the coffee. This creates a foam on the top of the espresso. This is one of the main characteristics of a good espresso.
There are three kinds of professional espresso machine makers, which differ in the type of pump they employ and the degree of heat that the coffee is. There are various ways to control the strength of the brew and the size of the cup that can be produced by the machine.
The first espresso machines were steam-type. They utilized only one boiler to make both steam and brew, but the pressure they could create was minimal - two bars of atmospheric pressure, at most. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp your beans yourself however the pump controls the water flow and pressure. This is a perfect combination of human control and mechanised accuracy.
The Filter
Espresso machines typically use a filter that separates the grounds of the coffee from hot water. The filter is also an essential part of the machine's temperature control, as it helps prevent overheating.
It also improves flavor, as it lets you enjoy a longer bloom phase. This lets the beans release their nuances, and also allows for better extraction.
It is important to keep in mind that even the finest filter can produce a bad cup of coffee. The quality of the beans, and the extraction process, are still crucial.
This is where the magic happens, it's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter, which is the thingy used to place the grounds of your coffee into when making espresso.
In the steam-driven espresso machine hot water is heated in an airtight container to produce steam, which is then pushed through the grounds under high pressure. They are less expensive and easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air pump-driven espresso machines have become more popular. They use an air compressor to force hot water into the grounds, and are far more portable than electric steam-driven machines.