How Does Machine Espresso Work?
Machine espresso employs precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it that makes it work?
In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.
espresso coffee machine Coffeee
As the name implies the group head is where you place your portafilter when brewing espresso. It distributes water into the portafilter, and regulates the pressure of the extraction. There are various kinds of group head, each with their own advantages and disadvantages. Some are specifically designed for temperature stability 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 in the picture above the group head is fitted with a variety of notches. You place your portafilter in these notches and then turn the head around to secure it. A gasket of rubber is situated inside the notches, which helps create a seal as you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial for an even extraction.
The group head does not just allow you to insert your portafilter easily, but it also maintains a constant temperature. It does this by cycling hot water through the brew pan and around the portafilter to ensure that it is always at the correct temperature to extract. This is vital, because even a few degrees can mean the difference between good and excellent espresso.
The Pump
Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines which use a lever. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.
Pumps are generally less expensive than piston-driven machines, and tend to last longer. However, both types of machines may become damaged due to excessive use and poor cleaning. They also add mechanical complexity that can lead to a high price tag on even the simplest models.
Certain espresso machines utilize steam pressure instead of a pump to brew espresso. The drawback of this is that the boiler that produces steam also raises the temperature of the water to boiling which can cause over-extraction. They also have to constantly rebuild their pressure in between cups. This requires energy and time.
A majority of espresso machines use the rotary or vibration pump, with a vibrating model using a vibrating disc to create the pressure, and rotating models that push hot water through the grounds at high speed. Both types of machine can make excellent espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter that contains the ground espresso and gets funnelled down into the cup. The steam creates pressure that pushes through the grounds of the coffee. This creates a layer crema on top. This is one of the main characteristics of a great espresso.
There are three distinct types of espresso machines, each with different pumps and brew temperature. There are various ways in which the brew could be controlled as well as the dimensions of the cup the machine is capable of making.
The first espresso machines were steam types. The earliest espresso machines were steam types. This led to the coffee tasting burnt and bitter. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most commonly used espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they picture these machines. If you have a semi-automatic machine you have to grind the beans and then tamp them by hand, but the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanised accuracy.
The Filter
Espresso machines usually have filters that separate the grounds of the coffee from hot water. The filter is also a vital element of the machine's temperature control, since it stops overheating.
A filter can also help with flavor because it allows for a longer flowering phase. This helps the beans release their flavor and gives an opportunity for a better extraction.
However it is crucial to keep in mind that even a great filter can make a terrible cup of coffee as the quality of the beans and extraction are important.
It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead, often referred to as the brewhead, is where the portafilter (the thingy you put the coffee grounds into) is placed when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to produce steam, which then pushes the hot water through the grounds at a high pressure. These machines are cheaper and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the perfect brewing conditions because they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.
In recent years, espresso machines driven by a compressed air pump have become increasingly popular. They utilize an air compressor to push the hot water through the grounds and are more portable than electric steam-driven machines.