How Does Machine Espresso Work?
The machine espresso makes use of precise pressure, as well as a filter technology that is mind-blowing to create the coffee you enjoy. What exactly is it that makes it work?
Espresso is created by forcing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Group Head
The group head is the portafilter that you place in the espresso maker when making it. It disperses the water into the portafilter, and then regulates the pressure during the extraction. There are a variety of types of group heads, each with their unique advantages and drawbacks. Some are designed to provide stability of temperature while others are 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 favorite among baristas because it offers multiple advantages in a single package.
As you can see in the photo above the group head comes with several notches to place your portafilter before twisting it with your hands to secure it. A gasket made of rubber is placed inside the notches, which helps make a seal when you insert your portafilter. The notches on the head allow for a precise positioning of the portafilter which is crucial to ensure a consistent extraction.
Aside from allowing you to easily connect your portafilter, the group head is responsible for maintaining an even temperature. This is done 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 note that even a tiny deviation can make the difference between a decent and a excellent espresso.
The Pump
The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure that is required to extract espresso. This is different from manually operated piston machines that employ a lever. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger before being pumped through the ground coffee inside the group head.
Pumps are generally less expensive than piston-driven machines and tend to last longer, but both types of machine can be damaged by excessive use and inadequate cleaning. Pumps are also more complicated mechanically, and can add to the cost of even simplest models.
Certain espresso machines utilize steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since 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 large majority of espresso machines employ an rotary or a vibration pump. A vibration model employs a vibrating disk to generate pressure, while the Rotary model pushes hot coffee through the ground at a high speed. Both models are capable of producing excellent espresso, however the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is what makes the water warm to a temperature that is ideal to extract. The resulting steam is then transferred to the portafilter that contains ground espresso beans and is then funneled down into the cup. The steam creates enough pressure to push the grounds of the coffee through. This results in a layer crema on top. This is one of the hallmarks of a good espresso.
There are three types of espresso makers, and they differ in the type of pump they employ and how hot the brew is. There are different ways to control the brew and the size of cup that can be produced by the machine.
The first espresso machines were steam type. The first espresso machines were steam types. The coffee tasted bitter and burned. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most commonly used espresso machine is a semiautomatic that has an electric pump. These are the things people think of when they imagine an espresso machine. Semi-automatic website machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a perfect compromise between human control and mechanised reliability.
The Filter
Espresso machines typically have filters that separate the coffee grounds from the hot water. The filter is also an important element of the temperature control system, since it helps prevent the machine from overheating.
It also aids in flavor, as it lets you enjoy a longer bloom time. This lets the beans release their nuances, and allows for a better extraction.
It is important to remember that even the most efficient filter can result in a bad cup of coffee. The quality of the beans, and the extraction process, remain crucial.
This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter, the device used to place the grounds of your coffee into when making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through grounds of coffee under high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent times, espresso machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to force the hot water through the grounds and are significantly more portable than electric steam-driven machines.