How Does Machine Espresso Work?
Machine espresso uses precision pressure and mind-blowing filter technology to create the coffee we love. How exactly does it work?
To make an espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the primary difference.
The Group Head
As the name implies the group head is the place you place your portafilter while brewing espresso. It disperses water in the portafilter, and then regulates the pressure during the extraction. There are a variety of types of group heads each with its distinct advantages and drawbacks. Some are specifically designed for stability of temperature while others are built to handle pre-infusion. Others are made to control the lever. Some come with a combination of both, like the E61. This is a favorite among baristas because it offers multiple advantages in one package.
As you can see in the photo above The group head features many notches in which you can place your portafilter and twist it with your hands to secure it. A gasket made of rubber is positioned in the notches to make a seal when you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial for an accurate extraction.
In addition to allowing you easily place your portafilter in, the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket, and around the portafilter, making sure that it's always at the correct temperature for extraction. It is crucial to keep in mind that even a slight difference can make the difference between a good and a excellent espresso.
The Pump
Contrary to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior to it is shot through the ground coffee inside the group head.
Pumps tend to be less expensive than piston-driven machines, and tend to last longer, but both types of machines can get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, which could increase the price of even the simplest models.
Some espresso machines make use of steam pressure instead of a pump to brew espresso. This could lead to over-extraction since the boiler that produces steam also warms the water to boil. They also have to constantly rebuild their pressure in between cups. This requires energy and time.
Many espresso machines employ a vibration or rotary pump, which is a vibration model using a vibrating disc that generates the pressure and an rotary model that pushes hot water through the grounds at high speed. home espresso machine of machines can produce an excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the component that heats water to the optimal temperature to extract. The steam created gets to the portafilter which is a container for espresso grounds. The steam is then channeled into the cup. The steam creates pressure and pushes through the coffee grounds. This creates a crema on the top of the espresso. This is the hallmark of a great espresso.
There are three types of espresso machines, each having a different type of pump and brew temperature. There are different ways in which the brew could be controlled, as well as the size of the cup that the machine is capable of making.
The first espresso machines were steam-types. The first espresso machines were steam types. This led to the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso machine is a semiautomatic model with an electric pump. These are what people imagine when they think of an espresso maker. Semi-automatic machines require you to grind and tamp your beans yourself The pump, however, regulates the water flow and pressure. This is a great combination of human control and mechanised consistency.
The Filter
Typically, espresso machines employ 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 temperature control, as it prevents overheating.
It also improves flavor, as it allows for a longer bloom phase. This allows the beans to release their flavors, and allows for a better extraction.
It is important to keep in mind that even the finest filter can produce a bad cup of coffee. The quality of the beans as well as the extraction, remain vital.
This is where the magic happens. It's what makes espresso taste good. The grouphead (also called the brewhead) is where you place the portafilter, which is the thingy used to place the grounds of your coffee into while making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then pushes hot water into the grounds of coffee under high pressure. These kinds of machines are typically less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their capacity to create the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.
In recent years, espresso machines powered by a compressed air compressor have become increasingly popular. They make use of an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven espresso machines.