How Does Machine Espresso Work?
machine espresso (
read review) makes use of precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. What exactly is it?
In order to make espresso, hot water is forced 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 suggests, the group head is where you place your portafilter when brewing espresso. It distributes water into the portafilter, and regulates the pressure of the extraction. There are many different kinds of group heads each with its particular advantages and drawbacks. Some are specifically designed for stability of temperature while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some come with a combination of both, like 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 above image the group head is made up of many notches in which you can place your portafilter and then twist it with your hands to lock it in. There is also a gasket made from rubber that resides inside the notches, which helps create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for an exact location of the portafilter which is essential for a consistent extraction.
The group head not only allows you to insert your portafilter easily however, it also keeps the same temperature. This is achieved by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is at the right level to extract the coffee. It is important to realize that even a tiny difference can make the difference between a decent and a great espresso.
The Pump
The motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines that use a lever. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pushed through the ground coffee in the group head.
Pumps are typically less expensive than piston-driven machines and
Machine Espresso tend to last longer. However, both types of machines may get damaged through overuse and lack of cleaning. They also increase the complexity of mechanical systems which can result in costly prices for even the most basic models.
Certain espresso machines remove the pump completely and instead make use of steam pressure to make espresso. The drawback is that the same boiler that produces steam also increases the temperature of water until it reaches boiling which can cause excessive extraction. In addition these machines are often required to restore their pressure between cups, which takes time and energy.
A majority of espresso machines use the rotary or vibration pump, which has a vibration model using a vibrating disc to create the pressure and an rotary model that pushes hot water through the grounds under high speed. Both models are capable of producing excellent espresso, but rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what is used to heat the water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter that contains the ground espresso coffee and is then pumped into the cup. During this process the steam is able to create enough pressure to push the grounds of the coffee through. This creates a foam on top of the espresso. This is one of the hallmarks of a good espresso.
There are three types of
cafe espresso machine makers. They differ in the kind of pump they use and the degree of heat that the espresso is. There are various ways that the brew may be controlled as well as the size of the cup that the machine can produce.
The earliest
uk espresso machine machines were steam type. The first espresso machines were steam-type machines. This resulted in the coffee tasting bitter and burnt. This is why the Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most well-known espresso maker is a semi-automatic one that has an electric pump. These are what people imagine when they think of an espresso maker. With a semi-automatic machine, you grind the beans and then tamp them by hand. However, the pump regulates the flow of water and pressure. This is an excellent compromise between human control and mechanized reliability.
The Filter
Espresso machines usually have filters that separate the coffee grounds from the hot water. The filter is also a vital component of the machine's temp control, as it helps prevent overheating.
It also aids in flavor, since a filter lets you enjoy a longer bloom time. This lets the beans release their flavors, and allows for better extraction.
It is important to keep in mind that even the best filter can make a bad cup of coffee. The quality of the beans, as well as the extraction, remain crucial.
This is where the magic happens. It's what makes espresso taste great. The grouphead, often referred to as the brew head, is where the portafilter (the thingy you put the ground coffee in) sits when you're making espresso.
Steam-driven espresso machines make use of hot water heated in an airtight vessel to create steam. The steam then pushes hot water into the grounds of coffee at high pressure. These types of machines are usually less expensive and easier to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.