How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How does it work exactly?
To make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the key 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 regulates the pressure during the extraction. There are a variety of group heads, each with its own advantages and disadvantages. Some are specifically designed for stability in temperature, while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some are a combination, like the E61. This is a favorite among baristas because it offers multiple benefits in one package.
As you can see from the image above, the group head is equipped with several notches. It is possible to place your portafilter in these notches and then twist the head to lock it. A gasket made of rubber is placed inside the notches to help create a seal while you insert your portafilter. The notches on the head allow for a precise positioning of the portafilter which is necessary to ensure a consistent extraction.
The group head not only lets you to place your portafilter easily however, it also keeps a constant temperature. It does this by circulating hot water through the brew pan and around the portafilter, ensuring that it's always at the correct temperature to extract. It is important to note that even a small variation can mean the difference between a great and a great espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, rotating espresso machines rely upon motorized pumps to provide the nine atmospheric bars of pressure required for espresso extraction. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger before it is shot through the ground coffee in the group head.
Pumps are generally less expensive and last longer than piston-driven machines. However, both kinds of machines can deteriorate due to excessive use and inadequate cleaning. They also increase the complexity of mechanical systems and can lead to a high price tag on even the simplest models.
Certain espresso machines do away with the pump entirely and utilize steam pressure to make espresso. The drawback is that the boiler that produces steam also raises the temperature of water until it reaches boiling which could lead to excessive extraction. In addition the machines often have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines make use of either a rotary or vibration pump, with a vibration model that uses a vibrating disc to generate the pressure and an rotary model that pushes hot water through the grounds at high speed. Both machines can produce excellent espresso, but rotary machines are more quiet, durable and less likely to break.
The more info Boiler
The boiler is the element which heats the water to the optimal temperature for extraction. The steam that is created will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. It is then funneled into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This results in a crema on the top of the espresso. This is the hallmark of a great espresso.
There are three kinds of espresso makers, and they differ in the type of pump they use and how hot the coffee is. There are different ways that the brew can be controlled check here and the size of the cup the machine can produce.
The earliest espresso machines were steam type. They used only one boiler to make both steam and brew however the pressure they were able to create was minimal - two bars of atmospheric pressure at most. This resulted in the coffee tasting burnt and bitter. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular 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. If you have a semi-automatic machine you grind the beans and then tamp them by hand. The pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized quality.
The Filter
Espresso machines typically have a filter that separates the grounds of the coffee from hot water. The filter is also an essential component of the machine's temperature control, since it stops overheating.
A filter also improves flavor as it allows for an extended flowering time. This lets the beans let their nuances out, and also allows for better extraction.
However it is crucial to keep in mind that even a top filter can result in a poor cup of coffee, since the quality of the beans and extraction is vital.
This is where the magic happens. It's what makes espresso taste great. The grouphead, also referred to as the brewhead, is where the more info portafilter (the device you put the ground coffee in) is placed when making espresso.
In a steam-driven espresso machine hot water is heated in an airtight tank to create espresso machine with milk frother steam. Steam is then pushed through the grounds with high pressure. These kinds of machines are usually cheaper and easier to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the perfect brewing conditions since here they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air compressor to force hot water through the ground and are much more mobile than steam-driven electric espresso machines.