How Does Machine Espresso Work?
Machine espresso employs precise pressure and amazing filter technology to make the perfect cup of coffee. What exactly does it work?
To make espresso hot water is pushed 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 name implies the group head is where you insert your portafilter when brewing espresso. It disperses water into the portafilter and regulates the pressure of extraction. There are several different types of group heads, each with their own advantages and disadvantages. Some focus on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. Some have a combination, such as the E61. This is a favorite among baristas due to the fact that it has multiple benefits in one package.
As you can see in the above image The group head features many notches in which you can place your portafilter and then twist it by hand to secure it. There is also a gasket made from rubber that is a part of the notches to help create the seal when you insert your portafilter into the machine. The notches permit precise placement of your portafilter. This is crucial for an accurate extraction.
Apart from allowing you easily place your portafilter in, the group head is also responsible to ensure that the temperature remains even. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it's always at the right temperature for extraction. This is important, as even a small difference in temperature can mean the difference between good and excellent espresso.
The Pump
Unlike manual piston machines, which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure required to extract espresso. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are typically less expensive and last for longer than piston-driven machines. However, both types of machines can degrade because of excessive use and insufficient cleaning. They also add mechanical complexity that can lead to an expensive price for even the simplest models.
Some espresso machines use steam pressure instead of a pump to brew espresso. The downside is that the boiler that produces steam also increases the temperature of water to boiling and can result in over-extraction. The machines must also continually rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of an rotary or vibrating pump, which is a vibration model that uses a more info vibrating disc to create pressure, and rotating models that push hot water through the grounds at high speed. Both models can make a great espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats water to the optimal temperature for extraction. The resultant steam then reaches the portafilter, which contains the ground espresso coffee and is then pumped down into the cup. During this process, steam creates pressure that pushes through the coffee grounds. This produces a layer of crema that is then poured over. This is one of the hallmarks of a good espresso.
There are three distinct types of espresso machines, each having different pumps and the temperature of get more info the brew. There are a variety of ways in which the brew can be controlled and the size of the cup the machine can produce.
The earliest espresso machines were steam types. They used one boiler to create 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 click here tasting bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular espresso machine is a semiautomatic with 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, more info but the pump regulates the water flow and pressure. This is a perfect compromise between human control and mechanised consistency.
The Filter
Typically, espresso machines use 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 improves flavor, since a filter allows for a more prolonged bloom phase. This helps the beans release their flavor and gives an opportunity for a better extraction.
It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, remain vital.
It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead, also referred to as the brewhead, is where the portafilter (the device you put the coffee ground into) sits when you're making espresso.
In a steam-driven espresso machine hot water read more is heated in an airtight container to create steam, which is then pushed through the grounds with high pressure. These kinds of machines are generally less expensive and easier to maintain than pump-driven models. They are however limited in their ability to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air compressor to force hot water through grounds and are much more portable than electric steam-driven machines.