How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and a filtering system that is awe-inspiring to create the coffee you love. But how exactly does it work?
Espresso is created by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.
The Group Head
The group head is the portafilter you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter before controlling the pressure of the extraction. There are various kinds of group heads, each with their particular advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion capabilities, while others are designed to control the lever. Some include a mix of features, such as the E61 that is to be the most popular among baristas for its ability to offer multiple benefits in one package.
As you can see from the photo above, the group head is fitted with a variety of notches. You can place your portafilter in these notches, then turn the head around to secure it. A gasket of rubber is situated inside the notches, which helps make a seal when you insert your portafilter. The notches on the head allow for a precise placement of the portafilter, which is vital for an even extraction.
Apart from allowing you easily connect your portafilter, the group head is also responsible for maintaining an even temperature. It does this by circulating hot water through the brew container and around the portafilter, ensuring that it is always at the correct temperature for extraction. It is important to realize that even a small variation can mean the difference between a great and a great espresso.
The Pump
Contrary to manual piston machines which rely on a lever that pressurize water, the rotary De'Longhi Dedica Style Espresso Machine: Premium Coffee Equipment - https://www.coffeee.uk/products/de-longhi-dedica-style-espresso-machine-... machines use motorized pumps that provide the nine atmospheric bars of pressure needed to extract espresso. The pressure is created 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, although both types of machines may become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which could increase prices of even simplest models.
Some espresso machines remove the pump entirely and use steam pressure to brew espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling and can result in excessive extraction. In addition, these machines frequently have to restore their pressure between cups, which takes time and energy.
Many espresso machines utilize either a rotary or vibration pump, with a vibrating model that uses a vibrating disc to create pressure and a rotary model pushing hot water through the grounds at high speed. Both machines can produce excellent espresso however rotary machines tend to be more quiet, durable and less likely to break down.
The Boiler
The boiler is what is used to heat the water to the ideal temperature to extract. The steam produced is then directed to the portafilter, which is a container for espresso grounds. It is then poured into the cup. During this process, the steam creates pressure to push through the coffee grounds. This creates a crema on top of the espresso. This is a hallmark of a great espresso.
There are three kinds of espresso makers, and they differ in the type of pump they employ and the degree of heat that the brew is. There are also different ways in which the brew can be controlled, as well as the size of the cup that the machine can produce.
The first espresso machines were steam-type. They employed one boiler to make both steam and brew however, the pressure they could produce was not very high - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso maker is a semi-automatic machine that has an electric pump. This is what people envision when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own The pump, however, regulates the flow of water and pressure. This is an excellent combination of human control and mechanised accuracy.
The Filter
Espresso machines typically have filters that separate the grounds of the coffee from hot water. The filter is also a vital component of the machine's temperature control, as it prevents overheating.
A filter also improves flavor as it allows for an extended flowering time. This helps the beans to release their flavor and gives an opportunity to improve extraction.
However it is crucial to remember that even a great filter can produce a bad cup of coffee, because the quality of the beans and extraction are vital.
It's in this area that the magic happens. This is what makes espresso taste so good. The grouphead, sometimes called the brewhead, is where the portafilter (the device you put the coffee ground into) is located when you're making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then moves hot water through the coffee grounds under high pressure. These types of machines tend to be cheaper and easier to maintain than pump-driven models. They are however limited to create the perfect brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, compressed-air-pump-driven espresso machines have been gaining popularity. They use an air-compressor De'Longhi ECP3630 Espresso/Cappuccino Machine: Adjustable Frother - https://www.coffeee.uk/products/de-longhi-ecp3630-espresso-cappuccino-ma... to push hot water through the ground. They are also more mobile than electric steam-driven espresso machines.