How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How exactly does it work?
In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the major difference.
The Head of the Group
As the name implies, the group head is where you insert your portafilter when brewing espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the resulting extraction. There are various kinds of group heads each with its own advantages and drawbacks. Some are designed to provide the stability of temperature while some are designed to handle pre-infusion. Others are made to control the lever. Some have a combination of features, such as the E61 that is the standard choice for many baristas because of its ability to offer multiple perks in one package.
As you can see in the image above the group head is made up of several notches to put your portafilter, then twist it with your hands to secure it. There is also a gasket made of rubber that is a part of the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head permit a precise location of the portafilter which is crucial to ensure an efficient extraction.
The group head not only lets you to insert your portafilter easily but also maintains the temperature at a constant level. This is done by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right to extract the coffee. It is important to note that even a few degree variation can mean the difference between a great and a great espresso.
The Pump
Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure that is required to extract espresso. This differs from manual piston machines that use a lever. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be less expensive than piston-driven machines espresso machines, and tend to last longer, but both types of machine can degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, which can increase the cost of even the simpler models.
Certain espresso machines do away with the pump entirely and employ steam pressure to create espresso. This can result in over-extraction because the boiler that produces steam also warms the water to boil. The machines also need to continuously rebuild their pressure between cups. This requires energy and time.
Many espresso machines make use of the rotary or vibration pump. A vibration model uses an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at a rapid speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to break down.
The Boiler
The boiler is the element which heats the water to the optimal temperature to extract. The steam that is produced is then directed to the portafilter, which contains the espresso coffee grounds. It is then funneled into the cup. In this process, the steam creates pressure and pushes through the coffee grounds. This creates a foam on the top of the espresso. This is a sign of a great espresso.
There are three different types of espresso machines, each having different pumps and brew temperature. There are a variety of ways to control the amount of brew, as well as the size of the cup that can be made by the machine.
The first espresso machines were steam type. They used one boiler to make steam and brew, however, the pressure they could produce was very low - just two bars of atmospheric pressure, at most. This led to the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic machine with an electric pump. This is what people envision when they think of an espresso maker. Semi-automatic machines require you to grind and tamp your beans yourself however the pump controls the water flow and pressure. This is an excellent compromise between human touch and mechanized accuracy.
The Filter
Typically, espresso machines use filters that separate the coffee grounds as they pass through the hot water. The filter is also an essential part of the machine's temperature control, since it helps to prevent overheating.
A filter can also help with flavor as it allows for a longer flowering period. This lets the beans let their nuances out, and also allows for better extraction.
However it is crucial to keep in mind that even a high-quality filter can produce a bad cup of coffee, since the quality of the beans and Coffeee.Uk extraction is still crucial.
It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead, also referred to as the brew head, is where the portafilter (the device you put the ground coffee into) is placed when making espresso.
In the steam-driven espresso machine hot water is heated in an airtight tank to create steam, which then pushes the hot water through the grounds with high pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. However, they are limited in their capacity to create the perfect conditions for brewing, because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.
In recent years, espresso machines powered by a compressed air compressor have become increasingly popular. They use an air compressor to force hot water into the ground. They are also more mobile than steam-driven electric espresso machines.