How Does Machine Espresso Work?
The machine espresso uses precision pressure, and filtering technology that is amazing to create the coffee you enjoy. How does it work exactly?
To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the major 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 is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are many different types of group heads each with its own advantages and drawbacks. Some are designed for stability of temperature while others are built to handle pre-infusion. Some are designed to control the lever. Some contain a variety of features, such as the E61 that is the standard choice for many baristas due to its capacity to offer multiple benefits in a single package.
As you can see in the image above the group head is made up of several notches where you place your portafilter and then twist it manually to lock it in. There is also a rubber gasket that resides inside the notches to help create the seal when you insert your portafilter into the machine. The notches permit an exact placement of the portafilter. This is essential for an accurate extraction.
Aside from allowing you to effortlessly insert your portafilter the group head is responsible to ensure that the temperature remains even. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level for extraction. This is important, as just a few degrees could make the difference between good and excellent espresso.
The Pump
In contrast to manual piston machines which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure required for espresso extraction. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger before being shot through the ground coffee in the group head.
Pumps are typically less expensive than piston-driven machines, and tend to last longer, although both types of machines may degrade with overuse and insufficient cleaning. They also make mechanically complex, which can result in costly prices for even the simplest models.
espresso coffee maker remove the pump entirely and employ steam pressure to create espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of the water to boiling, which can lead to excessive extraction. They also have to constantly rebuild their pressure in between cups. This takes energy and time.
A majority of espresso machines utilize an rotary or a vibration pump. A vibration model makes use of a rotating disk to generate pressure, while a Rotary model pushes hot coffee through the ground at a rapid speed. Both models can produce an excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the one that makes the water warm to a temperature that is ideal to extract. The steam that is produced gets to the portafilter which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. The steam creates pressure that pushes through the grounds of the coffee. This results in a layer crema on top. This is a sign of a great espresso.
There are three kinds of espresso makers, and they differ in the kind of pump they use and the degree of heat that the brew is. There are also different ways that the brew can be controlled as well as the dimensions of the cup the machine can produce.
The earliest espresso machines were steam type. They employed one boiler to make both steam and brew, however, the pressure they could create was minimal - two bars of atmospheric pressure at the most. This resulted in the coffee tasting bitter and burnt. This is the reason Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most common espresso maker is a semi-automatic machine that has an electric pump. These are the things people think of when they think of an espresso maker. With a semi-automatic machine you need to grind the beans and tamp them by hand. However, the pump provides regulated water flow and pressure. This is a great compromise between the human touch and the mechanized accuracy.
The Filter
Espresso machines typically have a filter that separates the coffee grounds from the hot water. The filter is also an essential part of the temperature control system, as it prevents the machine from overheating.
A filter also helps with flavor as it allows for a longer flowering period. This helps the beans to release their nuances and gives an opportunity for a 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 and the extraction process, remain vital.
It's here that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead, also called the brew head, is the place where the portafilter (the thingy you put the coffee ground into) is placed when you're making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. This is then pushed through the grounds under high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They make use of an air compressor to push hot water across the ground. They are also more mobile than steam-driven electric espresso machines.