The Complete Guide To Machine Espresso
How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and incredible filter technology to produce the delicious coffee we enjoy. What exactly is espresso coffee machines coffeee.uk ?
Espresso is produced by pushing hot water at high pressure through finely ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.
The Group Head
The name implies, the group head is the place you put your portafilter in when making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure of the extraction. There are many different kinds of group head each with its own advantages and disadvantages. Some focus on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. Some include a combination like the E61. This is a preferred choice for baristas as it provides a variety of benefits in a single package.
As you can see in the above photo the group head has a number of notches. You can place your portafilter in these notches, then turn the head around to secure it. There is also a rubber gasket which is located inside the notches to help create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact placement of the portafilter, which is crucial to ensure a consistent extraction.
The group head is not just able to allow you to place your portafilter easily however it also keeps the same temperature. It does this by circulating hot water through the brew basket, and around the portafilter, making sure that it is always at the right temperature for extraction. It is crucial to keep in mind that even a few degree variation can mean the difference between a good and a great espresso.
The Pump
Unlike manual piston machines, that use a lever to pressurize water, the rotary espresso machines use motorized pumps that provide the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior to being pumped through the ground coffee in the group head.
Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines are susceptible to degrading due to overuse and inadequate cleaning. Pumps are also more complicated mechanically, and can add to the cost of even the simple models.
Some espresso machines do away with the pump entirely and make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that makes steam also heats the water until it comes to a boil. The machines must also constantly rebuild their pressure between cups. This requires energy and time.
Many espresso machines make use of an rotary or vibrating pump, which has a vibration model that uses a vibrating disc to create the pressure and rotating models that push hot water through the grounds at high speed. Both machines can produce excellent espresso but rotary machines are more stable, quieter and less likely to break down.
The Boiler
The boiler is the one that heats the water to the right temperature for extraction. The steam created will eventually reach the portafilter, which contains the espresso coffee grounds. It is then funneled into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This results in a crema on the top of the espresso. This is a sign of a great espresso.
There are three types of espresso makers, which differ in the type of pump they use and the degree of heat that the espresso is. There are different ways that the brew may be controlled as well as the size of the cup the machine is capable of making.
The first espresso machines were steam-based. They employed one boiler to create both steam and brew but the pressure they could produce was very low - just two bars of atmospheric pressure at the most. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso maker is a semi-automatic device with an electric pump. These are what people imagine when they think of an espresso maker. With a semi-automatic espresso machine, you grind the beans and tamp them yourself but the pump provides regulated water flow and pressure. This is a great combination of human control and mechanized consistency.
The Filter
Espresso machines usually use filters that separate the coffee grounds from the hot water. The filter is also an important component of the temperature control system, because it stops the machine from overheating.
A filter also improves flavor since it allows for the beans to flower for a longer period of time. This lets the beans let their nuances out, and improves extraction.
However, it is important to keep in mind that even a good filter can result in a poor cup of coffee, since the quality of the beans and extraction are important.
This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter - the thingy that you use to put the grounds of coffee into when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. Steam is then pushed through the grounds with high pressure. These machines are less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to produce the ideal conditions for brewing since they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.
In recent years, compressed-air-pump-driven espresso machines have become more popular. They make use of an air compressor to force hot water into the ground and are much more mobile than steam-driven electric espresso machines.