How Does Machine Espresso Work?
The machine espresso uses precise pressure and filter technology that is mind-blowing to make the coffee you enjoy. How does it work exactly?
Espresso is created by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.
The Head of the Group
The name implies the group head is the place you insert your portafilter when making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure that results from the extraction. There are numerous kinds of group heads, each with its own advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion features, and others are designed to control the lever. There are even some that contain a variety of features, such as the E61, which is considered the classic choice among many baristas due to its capacity to provide multiple benefits in one package.
As you can see in the above photo, the group head has a number of notches. The portafilter is placed into these notches and twist the head to lock it. A gasket made of rubber is positioned inside the notches, which helps make a seal when you insert your portafilter. The notches on the head permit a precise location of the portafilter which is vital to ensure an efficient extraction.
The group head not only allows you to insert your portafilter easily but also maintains an even temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is at the right level for extraction. It is crucial to keep in mind that even a few degree variation can mean the difference between a great and a excellent espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure that are required to extract Salter EK3131 Black Espresso Coffee Machine: Barista Style. The pressure is created by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be less expensive and last longer than piston-driven machines. However, both kinds of machines may degrade due to excessive use and inadequate cleaning. Pumps are also more complex mechanically, which can raise prices of even simple models.
Some espresso machines use steam pressure instead of a pump in order to brew espresso. This could lead to over-extraction since the boiler that makes steam also heats the water until it comes to a boil. In addition the machines often have to rebuild their pressure between cups, which requires time and energy.
Many espresso machines employ a vibration or rotary pump, which has a vibration model using a vibrating disc to create the pressure, and a rotary model pushing hot water through the grounds under high speed. Both machines can make excellent espresso but rotary machines are quieter, more durable and less likely to break.
The Boiler
The boiler is the part which heats the water to the optimal temperature for extraction. The steam that is produced reaches the portafilter, which is the container that holds the espresso coffee grounds. It is then funneled into the cup. The steam creates pressure that pushes through the grounds of the coffee. This results in a whipped-up top of the espresso. This is a hallmark of a good espresso.
There are three distinct types of espresso machines, each having different pumps and brew temperature. There are many ways to control the amount of brew, as well as the size of cup that can be made by the machine.
The first Sage Bambino Espresso Machine: Stainless Steel SES450BSS machines were steam-types. They had one boiler to create steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure at most. This resulted in the coffee tasting burnt and bitter. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most common espresso maker is a semi-automatic device that has an electric pump. These are what people imagine when they think of an espresso maker. With a semi-automatic espresso machine, you grind the beans and then tamp them yourself but the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human touch and the mechanised quality.
The Filter
Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temp control, since it helps to prevent overheating.
A filter also improves flavor, as it permits the beans to flower for a longer period of time. This allows the beans to release their flavors, and improves 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, remain crucial.
This is where the magic happens, and it's what makes espresso taste great. The grouphead, often called the brewhead, is where the portafilter (the container you place the coffee ground into) is placed when you're making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds under high pressure. These kinds of machines are typically less expensive and simpler to maintain than pump-driven models. They are however limited in their ability for creating the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines driven by compressed air-pump are becoming increasingly popular. They use an air compressor to force hot water through grounds and are significantly more portable than steam-driven electric machines.