How Does Machine Espresso Work?
The machine espresso is made using precision pressure, and a filtering technology that is amazing to make the coffee you enjoy. What exactly does it work?
Espresso is made by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee. However the pressure is the major difference.
The Head of the Group
As the name implies, the group head is where you place your portafilter while making espresso. It disperses the water into the portafilter and regulates the pressure of the extraction. There are several different types of group heads each with its distinct advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. Some include a combination such as the E61. This is a favorite among baristas as it provides a variety of advantages in a single package.
As you can see from the photo above the group head is equipped with several notches. You can place your portafilter in these notches, then twist the head to secure it. There is also a gasket of rubber that is a part of the notches to help create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of your portafilter. This is crucial to ensure an even extraction.
Aside from allowing you to easily place your portafilter in, the group head is responsible to maintain an even temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level for extraction. It is important to note that even a small variation can mean the difference between a great and a excellent espresso.
The Pump
Motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure needed for espresso extraction. This is different from manual piston machines which use levers. This pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior to being pumped through the ground coffee inside the group head.
Pumps are generally less expensive and last for longer than piston-driven machines. However, portable espresso maker of machines can degrade due to overuse and inadequate cleaning. Pumps are also more complex mechanically, which can increase the cost of even simplest models.
Some espresso machines eliminate the pump completely and employ steam pressure to create espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water to the point of boiling which could lead to over-extraction. The machines also need to constantly rebuild their pressure in between cups. This requires energy and time.
Many espresso machines make use of either a vibration or rotary pump. A vibration model makes use of a rotating disk to generate pressure, while a rotary model pushes hot water through the ground at a rapid speed. Both machines produce great espresso but rotary machines are more stable, quieter and less likely to break.
The Boiler
The boiler is the part that heats water to an optimal temperature for extraction. The resulting steam reaches the portafilter which holds the ground espresso and is then pumped down into the cup. The steam causes enough pressure to push the grounds of coffee through. This results in a layer crema that is then poured over. This is one of the hallmarks of a good espresso.
There are three kinds of espresso makers. They differ in the kind of pump they use and how hot the coffee is. There are different ways that the brew may be controlled and the dimensions of the cup the machine is capable of making.
The earliest espresso machines were steam-based. The first espresso machines were steam-type machines. This led to the coffee tasting burnt and bitter. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso machine is a semiautomatic one with an electric pump. These are what people imagine when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself while the pump controls the flow of water and pressure. This is an excellent solution that combines human control with mechanised reliability.
The Filter
Typically, espresso machines utilize a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also an important component of the temperature control system because it stops the machine from overheating.
Filters also aid in flavor, as it permits a longer flowering phase. This helps the beans release their flavor and gives an opportunity for better extraction.
However, it is important to remember that even a good filter can make a terrible cup of coffee, since the quality of the beans and extraction is essential.
It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also known as the brewhead) is where you place the portafilter, the device used to place the grounds of coffee into while making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds at high pressure. These kinds of machines tend to be cheaper and easier to maintain than pumps-driven models. They are however limited 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 driven by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water into the ground and are more mobile than steam-driven electric espresso machines.