How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to make the perfect cup of coffee. What exactly is it?
Espresso is created by forcing hot water at high pressure through finely ground coffee. The process is similar to that of making drip coffee. However, it is the pressure that makes the main difference.
The Head of the Group
The group head is the portafilter you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are a variety of types of group head, each with their distinct advantages and drawbacks. Some are designed for temperature stability while others are specifically designed to handle pre-infusion. Some are designed to control the lever. There are even espresso coffee machine that contain a variety of features, like the E61, which is the standard choice for many baristas for its ability to offer multiple perks in one package.
As you can see from the above photo, the group head is fitted with a variety of notches. You place your portafilter in these notches, then twist the head to lock it. There is also a rubber gasket in the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is vital for an even extraction.
Aside from allowing you to easily connect your portafilter, the group head is also responsible to ensure that the temperature remains even. It does this by circulating hot water through the brew basket, and around the portafilter, making sure that it is always at the correct temperature for extraction. It is important to remember that even a few degree deviation can make the difference between a good and a excellent espresso.
The Pump
The motorized pumps in espresso machines rotary provide nine atmospheric bar pressure needed to extract espresso. This is different from manual piston machines which use levers. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are generally less expensive than piston-driven machines and tend to last longer, however both types of machines may be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, which can increase the cost of even simple models.
Some espresso machines make use of steam pressure instead of a pump for brewing espresso. This can lead to over-extraction as the boiler that produces steam also heats the water to boil. These machines also have to continuously rebuild their pressure between cups. This takes energy and time.
Many espresso machines utilize the rotary or vibration pump, which is a vibration model using a rotating disc to create pressure and rotating models that push hot water through the grounds under high speed. Both models can produce an excellent espresso, however the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is used to heat the water to the right temperature to extract. The resulting steam is then transferred to the portafilter, which contains ground espresso beans and is then pumped into the cup. In this process, the steam causes pressure to push through the coffee grounds. This results in a whipped-up top of the espresso. This is one of the main characteristics of a good espresso.
There are three types of espresso makers. They differ in the type of pump they use and how hot the coffee is. There are different ways to control the amount of brew, as well as the size of the cup that can be made by the machine.
The earliest espresso machines were steam types. The earliest espresso machines were steam-type machines. The coffee tasted bitter and burnt. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic machine that has an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you have to grind the beans and then tamp them by hand. However, the pump regulates the flow of water and pressure. This is a great compromise between the human touch and the mechanised accuracy.
The Filter
Espresso machines usually use filters that separate the grounds of the coffee from the hot water. The filter is also an essential part of the machine's temperature control, since it helps to prevent overheating.
A filter also helps with flavor as it allows for the beans to flower for a longer period of time. This lets the beans let their nuances out, and also allows for better extraction.
It is important to remember that even the finest filter can produce a bad cup of coffee. The quality of the beans, and the extraction process, are still very important.
This is where the magic happens, it's what makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter, the thingy used to place the coffee grounds into, while making espresso.
In a steam-driven espresso machine hot water is heated in an airtight container to create steam. This 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. 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 been gaining popularity. They use an air compressor to force hot water through the grounds and are much more portable than electric steam-driven machines.