How Does Machine Espresso Work?
The machine espresso makes use of precise pressure and filter technology that is awe-inspiring to make the coffee you love. What exactly is it?
To make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference.
The Group Head
The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter, and controlling the pressure that results from the extraction. There are many different types of group heads each with its own advantages and drawbacks. Some are specifically designed for the stability of temperature while some are specifically designed to handle pre-infusion. Others are made to control the lever. There are also some that come with a range of features, such as the E61 one, which is the classic choice among many baristas because of its ability to offer multiple benefits in one package.
As you can see in the above photo The group head features numerous notches that you can place your portafilter before twisting it manually to secure it. A gasket made of rubber is placed within the notches to create a seal when you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is crucial for an even extraction.
The group head does not just allow you to put in your portafilter easily however it also keeps the same temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, making sure that the temperature is constant for extraction. This is crucial, since just a few degrees could make the difference between excellent and great espresso.
The Pump
Contrary to 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 needed for espresso extraction. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger before being shot through the ground coffee inside the group head.
Pumps tend to be less expensive and last for longer than piston-driven machines. However, both kinds of machines can deteriorate due to excessive use and poor cleaning. They also make mechanically complex and can lead to costly prices for even the most basic models.
Some espresso machines employ steam pressure instead of a pump to brew espresso. This can lead to over-extraction as the boiler that makes steam also warms the water to boil. They also have 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 employs a vibrating disk to generate pressure, whereas the rotating model pushes hot water through the ground at a rapid speed. Both machines can make great espresso, however rotary machines are more quiet, durable and less likely to fail.
The Boiler
The boiler is what makes the water warm to the right temperature to extract. The steam that is produced will eventually reach the portafilter, which contains the espresso coffee grounds. espresso machines uk is then poured into the cup. During this process, the steam creates pressure to push through the coffee grounds. This creates a foam on top of the espresso. This is a sign of a great espresso.
There are three kinds of espresso makers, which differ in the type of pump they employ and the degree of heat that the espresso is. There are a variety of ways to control the strength of the brew and the size of cup that can be produced by the machine.
The first espresso machines were steam-type. They had a single boiler to make steam and brew, however the pressure they were able to generate was low - only two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most well-known espresso machine is a semiautomatic one with an electric pump. This is what people envision when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the water flow and pressure. This is a great compromise between the human touch and the mechanised consistency.
The Filter
Typically, espresso machines employ filters to separate the grounds of coffee as they move through the hot water. The filter is also an essential component of the machine's temp control, since it helps to prevent overheating.
It also aids in flavor as a filter lets you enjoy a longer bloom phase. This allows the beans to let their nuances out and provides an opportunity to improve extraction.
However, it is important to keep in mind that even a top filter can make a terrible cup of coffee, as the quality of the beans and extraction is still vital.
This is where the magic happens, it's the thing that makes an espresso really taste great. 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.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to make steam. The steam then pushes hot water through the coffee grounds under high pressure. These types of machines are generally less expensive and easier to maintain than pump-driven models. They are however limited to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. 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 across the ground and are more mobile than electric steam-driven espresso machines.