How Does Machine Espresso Work?
Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it that makes it work?
Espresso is produced by pushing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee, but the difference is in the pressure.
The Head of the Group
As the name implies the group head is the place you insert your portafilter when brewing espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are a variety of group heads each with its own advantages and drawbacks. Some focus on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. Some are a combination, such as the E61. This is a favorite among baristas due to the fact that it has multiple benefits in a single package.
As you can see in the above image the group head is made up of several notches where you place your portafilter before twisting it by hand to secure it. A rubber gasket is located within the notches to make a seal when you insert your portafilter. The notches on the head permit a precise placement of the portafilter, which is essential for an even extraction.
The group head is not just able to allow the portafilter to be inserted easily, but it also maintains the temperature at a constant level. It does this by circulating hot water through the brew basket, and around the portafilter to ensure that it's always at the right temperature for extraction. It is crucial to keep in mind that even a tiny deviation can make the difference between a good and a great best espresso machine under 500.
The Pump
Contrary to manual piston machines which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure necessary to extract espresso. 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 machines and tend to last longer, however both types of machine can be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, and can add to the cost of even simplest models.
Certain espresso machines for home machines eliminate the pump completely and instead make use of steam pressure to make espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of water to the point of boiling, which can lead to excessive extraction. They also have to continuously rebuild their pressure between cups. This takes energy and time.
Many espresso machines employ either a rotary or vibration pump, which has a vibration model using a rotating disc that generates the pressure and the rotary model pushing hot water through the grounds under high speed. Both machines can produce excellent espresso but rotary machines are more quiet, durable and less likely to fail.
The Boiler
The boiler is the one that heats the water to the right temperature for extraction. The steam that is produced reaches the portafilter which holds ground espresso beans and is then pumped into the cup. The steam creates enough pressure to push the coffee grounds through. This results in a layer crema on top. This is one of the main characteristics of a great espresso.
There are three types of espresso makers, and they differ in the type of pump they use and how hot the coffee is. There are various ways to control the brew and the size of the cup that can be made by the machine.
The earliest espresso machines were steam type. The earliest espresso machines were steam types. This led to the coffee tasting burnt and bitter. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most common espresso coffee machine machine is a semiautomatic that has an electric pump. These are what people imagine when they think of an espresso maker. With a semi-automatic machine, you have to grind the beans and then tamp them by hand. However, the pump is able to regulate the flow of water and pressure. This is a fantastic compromise between human control and mechanized consistency.
The Filter
Typically, espresso machines utilize filters to separate the grounds of coffee as they move through the hot water. The filter is also an essential component of the machine's temperature control, as it helps prevent overheating.
Filters also aid in flavor since it allows for a longer flowering period. This allows beans to release their nuances and gives an opportunity for a better extraction.
However it is crucial to remember that even a top filter can result in a poor cup of coffee, as the quality of the beans and extraction is still essential.
This is where the magic happens, it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you put the portafilter, the thingy that you use to put the grounds of your coffee into while making espresso.
Steam-driven espresso machines make use of hot water heated in an airtight container to produce steam. The steam then pushes hot water through coffee grounds under high pressure. These types of machines are usually cheaper and easier to maintain than pumps-driven models. However, they are limited in their capacity to create the perfect conditions for brewing, since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air-compressor to force hot water through the ground and are much more mobile than electric steam-driven espresso machines.