Wisdom On Machine Espresso From The Age Of Five
How Does Machine Espresso Work?
The machine espresso uses precise pressure, as well as a filter technology that is mind-blowing to make the coffee you enjoy. How exactly does it work?
Espresso is made 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 is inserted when you are making espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure that results from the extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some are designed for the stability of temperature while some are built to handle pre-infusion. Some are designed to control the lever. There are also some that include a mix of features, such as the E61, which is considered the classic choice among many baristas for its ability to offer multiple benefits in a single package.
As you can see in the above photo the group head comes with numerous notches that you can place your portafilter and twist it manually to lock it in. There is also a gasket made of rubber in the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches on the head permit an exact positioning of the portafilter which is vital for an efficient extraction.
In addition to allowing you to easily insert your portafilter, the group head is responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right for extraction. It is important to note that even a small differences can make the distinction between a good and excellent espresso.
The Pump
Unlike manual piston machines, which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure required for espresso extraction. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be less expensive than piston-driven machines and tend to last longer. However, both types of machines could become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which can increase prices of even most basic models.
Some espresso machines make use of steam pressure instead of a pump to make espresso. This can result in over-extraction because the boiler that produces steam also causes the water to boil. The machines also need to continuously rebuild their pressure between cups. This requires energy and time.
Many espresso machines use the rotary or vibration pump. A vibration model uses a rotating disk to generate pressure, whereas a Rotary model pushes hot coffee through the ground at a high speed. Both types of machines can make excellent espresso, but rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats the water to the ideal temperature to extract. The steam created reaches 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 grounds of coffee through. This creates a foam on top of the espresso. This is one of the main characteristics of a good espresso.
There are three distinct types of espresso machines, each having different pumps and brew temperature. There are different ways to control the brew and the size of the cup that can be produced by the machine.
The first espresso machines were steam-type. They employed a single boiler to make both steam and brew however the pressure they were able to create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burned. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most common espresso machine is a semiautomatic that has an electric pump. These are the images people have when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself while the pump controls the water flow and pressure. This is an excellent compromise between human control and mechanized reliability.
The Filter
Typically, espresso machines use filters to separate the grounds of coffee as they move through the hot water. The filter is also an important component of the temperature control system because it stops the machine from overheating.
A filter also helps with flavor because it allows for an extended flowering time. This allows beans to let their nuances out and provides an opportunity for better extraction.
It is important to keep in mind that even the best filter can produce a bad cup of coffee. The quality of the beans and the extraction process, are still very important.
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 that you put the grounds of your coffee into when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. Steam then pushes the hot water through the grounds at high pressure. These kinds of machines tend to be less expensive and simpler to maintain than pump-driven models. However, professional espresso machine for home are limited in their ability to provide the perfect brewing conditions as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.
In recent years, espresso machines driven by compressed air-pump are becoming increasingly popular. They utilize an air compressor to push hot water into the grounds and are more portable than steam-driven electric machines.