How Does Machine Espresso Work?
The machine espresso is made using precision pressure, and a filter technology that is awe-inspiring to make the coffee you enjoy. What exactly is it?
In order to make espresso hot water is pushed under pressure through finely ground coffee. espresso coffee machines is similar to making drip coffee, but the major difference is in the pressure.
The Group Head
The name implies the group head is the place you place your portafilter when brewing espresso. It disperses the water into the portafilter, and then regulates the pressure of the extraction. There are many different types of group heads each with its own advantages and drawbacks. Some focus on temperature stability, others on pre-infusion features, and others are designed to control the lever. Some include a mix of features, such as the E61, which is to be the most popular among baristas for its ability to offer multiple benefits in one 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 gasket made from rubber that resides inside the notches and helps to create an airtight seal after inserting your portafilter into the machine. The notches on the head permit a precise placement of the portafilter, which is essential for a consistent extraction.
The group head not only allows you to insert your portafilter easily but also maintains an even temperature. It does this by circulating hot water through the brew container and around the portafilter, making sure that it is always at the right temperature for extraction. This is vital, because even a few degrees can make the difference between a good and great espresso.
The Pump
Unlike manual piston machines, that use a lever to pressurize water, rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure that are required to extract espresso. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.
Pumps tend to be cheaper than piston-driven machines, and they tend to last longer, although both types of machines can become damaged due to excessive use and poor cleaning. They also add mechanical complexity that can lead to an expensive price for even the simplest models.
Certain espresso machines can eliminate the pump entirely and make use of steam pressure to make espresso. The drawback is that the boiler that produces steam also raises the temperature of the water until it reaches boiling, which can lead to excessive extraction. Additionally these machines typically have to restore their pressure between cups, which requires time and energy.
A majority of espresso machines use either a rotary or vibration pump, which has a vibration model using a rotating disc to generate the pressure and the rotary model pushing hot water through the grounds at high speed. Both machines can make excellent espresso however rotary machines tend to be quieter, more durable and less likely to break down.
The Boiler
The boiler is what heats the water to the perfect temperature for extraction. The resultant steam then reaches the portafilter that contains the ground espresso and is then pumped down into the cup. During this process the steam generates enough pressure to push the grounds of the coffee through. This creates a crema on the top of the espresso. This is a sign of a great espresso.
There are three different types of espresso machines, each having different types of pumps and the temperature of the brew. There are different ways to control the amount of brew, as well as the size of the cup that can be made by the machine.
The earliest espresso machines were steam type. They utilized only one boiler to make both steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure maximum. This resulted in the coffee tasting burnt and bitter. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular espresso maker is a semi-automatic one with an electric pump. These are what people imagine when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and pressure. This is a great compromise between the human touch and mechanized accuracy.
The Filter
Espresso machines usually have a filter that separates the grounds of coffee from hot water. The filter is also an important component of the temperature control system because it stops the machine from overheating.
A filter can also help with flavor as it allows for an extended flowering time. This allows beans to release their flavors and provides an opportunity for a better extraction.
It is important to keep in mind that even the best filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, are still crucial.
It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you put the portafilter, the device which you put the grounds of coffee into when making espresso.
In a steam-driven espresso machine hot water is heated in an airtight container to create steam. Steam is then pushed through the grounds with high pressure. These machines are less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. 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 grounds and are much more portable than electric steam-driven machines.