How Does Machine Espresso Work?
The machine espresso utilizes precision pressure, and filter technology that is awe-inspiring to create the coffee you enjoy. How exactly does it work?
Espresso is made by pushing espresso coffee machine under high pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference.
The Group Head
The group head is the portafilter is inserted when you are making espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure that results from the extraction. There are several different types of group heads each with its distinct advantages and drawbacks. Some are designed to provide temperature stability while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some are a combination, such as the E61. This is a preferred choice for baristas as it provides a variety of advantages in one package.
As you can see in the photo above, the group head has many notches in which you can place your portafilter and then twist it by hand to secure it. A rubber gasket is located within the notches to create a seal while you insert your portafilter. The notches allow for an exact placement of the portafilter. This is crucial for a consistent extraction.
The group head does not just allow you to place your portafilter easily but also maintains an even 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. This is important because even a few degrees can make the difference between excellent and great espresso.
The Pump
The motorized pumps used in rotary espresso machines provide the nine atmospheric bars of pressure required to extract espresso. This differs from manually operated piston machines that employ levers. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being shot through the ground coffee in the group head.
Pumps are generally cheaper and last longer than piston-driven machines. However, both types of machines can deteriorate due to excessive use and poor cleaning. Pumps are also more complex mechanically, and can add to the cost of even the simplest models.
Certain espresso machines remove the pump completely and make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. Additionally the machines often have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines use the rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while a rotating model pushes hot water through the ground at a rapid speed. Both types of machines can produce an excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler heats the water to the ideal temperature to extract. The steam created will eventually reach the portafilter, which is a container for espresso grounds. The steam is then channeled into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This creates a crema on top of the espresso. This is a sign of a good espresso.
There are three distinct types of espresso machines, each having different types of pumps and brew temperature. There are a variety of ways that the brew may be controlled, as well as the dimensions of the cup the maker can create.
The earliest espresso machines were steam type. They employed a single boiler to make steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans by 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 that separate the grounds of the coffee as they go through the hot water. The filter is also an essential component of the machine's temp control, since it helps to prevent overheating.
It also aids in flavor, as a filter can allow for a longer bloom time. This helps the beans release their nuances and gives an opportunity for better extraction.
It is important to remember that even the finest filter can make a bad cup of coffee. The quality of the beans and the extraction, remain vital.
This is where the magic happens, it's the thing that makes espresso taste great. The grouphead, often called the brew head, is the place where the portafilter (the device you put the coffee grounds into) sits when you're making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to create steam. The steam then moves hot water through the grounds of coffee at high pressure. These types of machines are generally less expensive and simpler to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect conditions for brewing, as they only operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.
In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They use an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven espresso machines.