How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. How exactly does it work?
In order to make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.
The Head of the Group
The group head is the portafilter that you insert when brewing espresso. It disperses water in the portafilter and controls the pressure of the extraction. There are many different kinds of group heads, each with their unique advantages and disadvantages. Some are designed for stability of temperature while others are built to handle pre-infusion. Others are made to control the lever. Some have a combination, such as the E61. This is a very popular choice for baristas as it provides a variety of benefits in one package.
As you can see in the image above the group head is equipped with several notches. You place your portafilter inside these notches, and then turn the head around to secure it. A rubber gasket is located inside the notches, which helps make a seal when you insert your portafilter. The notches permit the precise placement of the portafilter. This is crucial to ensure a consistent extraction.
The group head does not just allow you to put in your portafilter easily, but it also maintains the same temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is always at the right level for extraction. It is crucial to keep in mind that even a few degree difference can make the difference between a great and a great espresso.
The Pump
Motorized pumps in rotary espresso machines provide the nine atmospheric bars of pressure required to extract espresso. This is different from manual piston machines which use levers. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.
Pumps are typically more affordable and last longer than piston-driven machines. However, both kinds of machines may degrade due to excessive use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simpler models.
Some espresso machines make use of steam pressure instead of a pump to make espresso. This can result in over-extraction because the boiler that produces steam also warms the water to boil. In addition these machines typically have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines make use of the rotary or vibration pump, which is a vibration model using a rotating disc to generate the pressure, and the rotary model pushing hot water through the grounds at high speed. Both machines produce great 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 the optimal temperature for extraction. The steam created gets to the portafilter which holds the espresso grounds. It is then funneled into the cup. During this process the steam is able to create enough pressure to push the grounds of the coffee through. This results in a whipped-up the top of the espresso. This is a hallmark of a great espresso.
There are three types of espresso makers, and they differ get more info in the kind of pump they use and the degree of heat that the brew is. There are different ways that the brew can be controlled as well as the size of the cup that the machine can produce.
The first espresso machines were steam-type. They had only one boiler to make both steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure, at most. This resulted in the coffee tasting bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most commonly used espresso machine is a semiautomatic one with an electric pump. This is what people envision when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized consistency.
The Filter
Espresso machines typically have a filter that separates the grounds of coffee from hot water. The filter is also a crucial element of the temperature control system, as it prevents the machine from overheating.
It also improves flavor as a filter allows for a more prolonged bloom time. This allows the beans to let their nuances out and provides the chance for better extraction.
It is important to keep in mind that even the most efficient filter can make a bad cup of coffee. The quality of the beans and the extraction process remain crucial.
It's in this area that the magic occurs. This is what makes espresso taste so delicious. The grouphead, often referred to as the brew head, is where the portafilter (the container you place the ground coffee in) is placed when you're making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds under high pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. They are however limited for creating the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have become more popular. They utilize an air compressor to push hot water across the ground, and are more mobile than steam-driven electric espresso machines.