How Does Machine Espresso Work?
The machine espresso makes use of precision pressure, and filtering system that is awe-inspiring to make the coffee you love. But how exactly does it work?
Espresso is made by pushing hot water under pressure through finely ground coffee. The process is similar to making drip coffee, however the main difference lies in the pressure.
The Group Head
The group head is the portafilter you insert when brewing espresso. It distributes water into the portafilter and regulates the pressure of the extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are designed for stability in temperature, while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some come with a combination of both, like the E61. This is a favorite among baristas as it provides a variety of benefits in one package.
As you can see from the image above the group head is equipped with several notches. The portafilter is placed in these notches, then twist the head to lock it. There is also espresso machines uk that resides inside the notches and helps create an airtight seal after inserting your portafilter into the machine. The notches on the head permit a precise location of the portafilter which is essential to ensure a consistent extraction.
The group head not only lets the portafilter to be inserted easily however it also keeps the same temperature. This is done by cycling hot water around the portafilter, and through the brew basin, ensuring the temperature is always right to extract the coffee. This is important because even a few degrees can make the difference between a good and excellent espresso.
The Pump
Contrary to manual piston machines which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure needed to extract espresso. The pressure builds up by removing tap water from a reservoir and pumping it through a heat exchanger prior being shot through the ground coffee in the group head.
Pumps are generally cheaper and last longer than piston-driven machines. However, both types of machines can degrade because of frequent use and insufficient cleaning. They also add mechanical complexity and can lead to an expensive price for even the simplest models.
Some espresso machines make use of steam pressure instead of a pump to make espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling and can result in over-extraction. The machines must also constantly rebuild their pressure between cups. This requires energy and time.
Many espresso machines make use of the rotary or vibration pump, which has a vibration model that uses a vibrating disc to create the pressure, and a rotary model pushing hot water through the grounds at high speed. Both machines can make excellent espresso, but rotary machines are quieter, more durable and less likely to break down.
The Boiler
The boiler is the element that heats water to the optimal temperature to extract. The steam created gets to the portafilter which holds the espresso grounds. It is then pumped into the cup. The steam creates pressure and pushes through the coffee grounds. This results in a layer of crema on top. This is the hallmark of a good espresso.
There are three kinds of espresso makers, and they differ in the kind of pump they use and how hot the espresso is. There are also different ways that the brew may be controlled and the size of the cup the machine can make.
The first espresso machines were steam type. They had only one boiler to make both brew and steam, however the pressure they were able to generate was low - only two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic one that has an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans by yourself The pump, however, regulates the water flow and pressure. This is a perfect compromise between human control and mechanized accuracy.
The Filter
Espresso machines typically use a filter that separates the coffee grounds from the hot water. The filter is also a crucial element of the temperature control system, as it prevents the machine from overheating.
It also helps with flavor, since a filter allows for a more prolonged bloom phase. This lets the beans let their nuances out, and also allows for better extraction.
However, it is important to keep in mind that even a good filter can produce a bad cup of coffee, because the quality of the beans and extraction is important.
This is where the magic happens, and it's what makes an espresso really taste great. The grouphead, often referred to as the brew head, is where the portafilter (the thingy you put the ground coffee into) is placed when you're making espresso.
In a steam-driven espresso machine hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds at a high pressure. They are less expensive and easier for the owner to maintain than pumps-driven models. However, they are limited in their capacity to create the ideal conditions for brewing since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, espresso machines driven by a compressed air compressor have become increasingly popular. They utilize an air compressor to force hot water through the grounds and are significantly more portable than steam-driven electric machines.