How Does Machine Espresso Work?
Machine espresso employs precise pressure and incredible filter technology to produce the delicious coffee we enjoy. But how exactly does it work?
In order to make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.
The Group Head
As the name implies, the group head is where you put your portafilter in when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure that results from the extraction. There are a variety of types of group heads each with its particular advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. There are some that contain a variety of features, such as the E61 that is the standard choice for many baristas for its ability to provide multiple benefits in a single package.
As you can see in the above image the group head is made up of many notches in which you can place your portafilter before twisting it manually to secure it. A gasket of rubber is situated inside the notches to help make a seal when you insert your portafilter. The notches allow for an exact placement of the portafilter. This is vital for an efficient extraction.
The group head not only lets you to place your portafilter easily, but it also maintains the temperature at a constant level. It does this by circulating hot water through the brew basket and around the portafilter to ensure that it's always at the correct temperature to extract. It is important to note that even a tiny deviation can make the difference between a good and great espresso.
The Pump
Contrary to manual piston machines which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure that are required for espresso extraction. The pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior to it is shot through the ground coffee in the group head.
Pumps tend to be less expensive and last longer than piston-driven machines. However, both types of machines can deteriorate because of excessive use and insufficient cleaning. Pumps are also more complicated mechanically, and can add to the cost of even most basic models.
Some espresso machines remove the pump completely and utilize steam pressure to make espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of the water to the point of boiling which can cause excessive extraction. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy.
Many espresso machines utilize a vibration or rotary pump, which has a vibration model that uses a vibrating disc that generates the pressure and rotating models that push hot water through the grounds under high speed. Both types of machines can make a great espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the part that heats water to an optimal temperature to extract. The steam that is produced gets to the portafilter which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process, steam creates pressure and pushes through the grounds of the coffee. This creates a layer crema that is then poured over. This is a hallmark of a great espresso.
There are three kinds of espresso machines, each having distinct pumps and brew temperature. There are a variety of ways to control the brew as well as the size of the cup that can be made by the machine.
The first espresso machines were steam-types. They had a single 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. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso maker is a semi-automatic one that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp your beans yourself The pump, however, regulates the flow of water and pressure. This is a fantastic solution that combines human control with mechanized accuracy.
The Filter
Typically, espresso machines utilize filters to separate the grounds of coffee when they pass through the hot water. The filter is also a vital element of the temperature control system, as it keeps the machine from overheating.
Filters also aid in flavor as it allows for the beans to flower for a longer period of time. This helps the beans to release their nuances and gives an opportunity to improve extraction.
However, it is important to remember that even a high-quality filter could result in a bad cup of coffee as the quality of the beans and extraction is important.
coffee machine espresso 's here that the magic happens. This is what makes espresso taste so delicious. The grouphead, also called the brew head, is where the portafilter (the container you place the ground coffee in) 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 pushes hot water through the grounds of the coffee under pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.
In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to force the hot water through the grounds and are significantly more portable than electric steam-driven machines.