How Does Machine Espresso Work?
The machine espresso is made using precision pressure, and a filter technology that is mind-blowing to create the coffee you love. How exactly does it work?
Espresso is made by pushing hot water under pressure through finely-ground coffee. The process is similar to that of making drip coffee. However, the pressure is the primary difference.
The Head of the Group
The group head is the portafilter that is inserted when you are making espresso. It distributes water into the portafilter, and then regulates the pressure of extraction. There are many different kinds of group head each with its own advantages and disadvantages. Some are designed to provide stability of temperature while others are specifically designed to handle pre-infusion. Others are made to control the lever. Some have a combination of features, like the E61, which is considered the standard choice for many baristas for its ability to provide multiple benefits in a single package.
As you can see from the photo above the group head has a number of notches. You place your portafilter inside these notches, and then turn the head around to secure it. A rubber gasket is located within the notches to create a seal when you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is necessary to ensure an efficient extraction.
The group head is not just able to allow you to put in your portafilter easily but also maintains an even temperature. This is done by cycling hot water around the portafilter and through the brew basin, ensuring that the temperature is always at the right level to extract the coffee. It is important to realize that even a slight difference can make the difference between a good and a great espresso.
The Pump
The motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure that is required to extract espresso. This is different from manually operated piston machines that employ levers. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be less expensive than piston-driven machines, and tend to last longer, however both types of machines can be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, and can add to the price of even the most basic models.
Some espresso machines make use of steam pressure instead of a pump to brew espresso. This can lead to over-extraction as the boiler that makes steam also heats the water until it comes to a boil. The machines also need to continually rebuild their pressure between cups. This takes energy and time.
A majority of espresso machines utilize the rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while the rotary model pushes hot water through the ground at 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 the part that heats the water to the ideal temperature for extraction. The steam produced reaches the portafilter, which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process, steam creates pressure that pushes through the coffee grounds. This results in a whipped-up the top of the espresso. This is one of the hallmarks of a great espresso.
There are three different types of espresso machines, each with different pumps and the temperature of the brew. There are a variety of ways to control the strength of the brew and the size of the cup that can be made by the machine.
espresso coffee machines were steam-types. They used only one boiler to make both steam and brew however, the pressure they could produce was very low - just two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most well-known espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they imagine these machines. If you have a semi-automatic machine you need to grind the beans and tamp them yourself but the pump controls the flow of water and pressure. This is a perfect compromise between human control and mechanized accuracy.
The Filter
Espresso machines usually have filters that separate the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temperature control, since it helps to prevent overheating.
It also aids in flavor as a filter allows for a longer bloom phase. This allows beans to release their flavors and provides an opportunity for better extraction.
However it is crucial to remember that even a great filter can result in a poor cup of coffee, as the quality of the beans and extraction are vital.
It's in this area that the magic occurs. This is the reason why espresso tastes so good. The grouphead, sometimes referred to as the brew head, is the place where the portafilter (the thingy you put the coffee ground into) sits 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 types of machines are usually cheaper and easier to maintain than pump-driven models. However, they are limited in their ability to create the ideal conditions for brewing because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.
In recent years, espresso machines driven by a compressed air pump have become increasingly popular. They utilize an air compressor to push hot water through grounds and are significantly more portable than electric steam-driven machines.