How Does Machine Espresso Work?
The machine espresso uses precise pressure, as well as a filter technology that is awe-inspiring to create the coffee you enjoy. How exactly does it work?
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 the pressure is the major difference.
The Head of the Group
The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter and then controlling the pressure that results from the extraction. There are numerous kinds of group heads each with distinct advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some contain a variety of features, such as the E61 that is the classic choice among many baristas for its ability to offer multiple perks in one package.
As you can see in the photo above The group head features several notches to place your portafilter before twisting it with your hands to secure it. A gasket made of rubber is placed 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 not only allows you to insert your portafilter easily, but it also maintains the temperature at a constant level. This is accomplished by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is constant for extraction. It is crucial to keep in mind that even a few degree variation can mean the difference between a good and a great espresso.
The Pump
Contrary to manual piston machines which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee in the group head.
Pumps tend to be less expensive than piston-driven machines and tend to last longer, however both types of machine can degrade with overuse and insufficient cleaning. They also add mechanical complexity, which can result in the cost of even the most basic models.
Some espresso machines use steam pressure instead of a pump for brewing espresso. This can lead to over-extraction as the boiler that produces steam also warms the water to boil. In addition these machines typically have to restore their pressure between cups, which requires time and energy.
Many espresso machines utilize a vibration or rotary pump, which is a vibration model using a vibrating disc that generates the pressure and a rotary model pushing hot water through the grounds under high speed. Both machines produce great espresso but rotary machines are more quiet, durable and less likely to fail.
The Boiler
The boiler is the part that heats the water to the ideal temperature to extract. The resulting steam is then transferred to the portafilter that contains the ground espresso coffee, and is then pumped down into the cup. read more During this process the steam creates enough pressure to push the grounds of the coffee through. This results in a crema on the top of the espresso. This is one of the hallmarks of a good espresso.
There are three kinds of espresso makers, which differ in the kind of pump they use and how hot the espresso is. There are a variety of ways to control the brew as well as the size of the cup that can be made by the machine.
The first espresso machines were steam-types. The first espresso machines were steam types. The coffee tasted bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso machine is a semiautomatic one with an electric pump. These are the things people think of when they think of an espresso machine. Semi-automatic machines require you to grind and tamp your beans yourself while the pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized consistency.
The Filter
Typically, espresso machines have filters to separate the grounds of coffee as they move through the hot water. The filter is also a vital component of the machine's temp control, since it helps to prevent overheating.
A filter also helps with flavor since it allows for a longer flowering period. This allows the beans to release their flavor and gives the chance for better extraction.
It is important to remember that even the finest filter could result in a poor cup of coffee. The quality of the beans and the extraction, remain vital.
It's in this area that the magic occurs. This is what makes espresso taste so good. The grouphead, also referred to as the brew head, is where the portafilter (the container you place the ground coffee in) sits when you're making espresso.
In a steam-driven espresso machine hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds under high pressure. These kinds of machines tend to be cheaper and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to produce the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.
In recent years, compressed air-pump-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the ground, and are more mobile than electric steam-driven espresso machines.