Machine espresso uses precision pressure and amazing filter technology to make the perfect cup of coffee. What exactly is it?Espresso is created by forcing hot water under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the primary difference.
The Group Head
The group head is the portafilter you put in when making espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are many different kinds of group head, each with their particular advantages and disadvantages. Some are focused on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some have a combination, like the E61. This is a favorite among baristas due to the fact that it has multiple advantages in one package.
As you can see from the photo above, the group head has a number of notches. It is possible to place your portafilter in these notches and then turn the head around to secure it. There is also a gasket of rubber that resides inside the notches and helps to create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is vital to ensure an efficient extraction.
The group head not only lets the portafilter to be inserted easily however it also keeps a constant temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level to extract the coffee. It is important to realize that even a few degree difference can make the difference between a decent and a great espresso.
The Pump
Unlike 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 by removing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee and espresso maker inside the group head.
Pumps tend to be less expensive than piston-driven machines, and they tend to last longer, although both types of machine can become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which can increase the cost of even most basic models.
Certain espresso machines utilize steam pressure instead of a pump to make espresso. This could lead to over-extraction since the boiler that produces steam also heats the water until it comes to a boil. These machines also have to constantly rebuild their pressure in between cups. This takes energy and time.
Many espresso machines utilize a vibration or rotary pump, which is a vibration model that uses a vibrating disc that generates the pressure, and the rotary model pushing hot water through the grounds under high speed. Both types of machines can produce an excellent espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats the water to the ideal temperature to extract. The steam created gets to the portafilter which is the container that holds the espresso coffee makers coffee and espresso machine grounds. It is then poured into the cup. During this process the steam generates enough pressure to push the grounds of the coffee through. This results in a whipped-up the top of the espresso. This is a hallmark of a good espresso.
There are three kinds of espresso makers, which differ in the type of pump they employ and the degree of heat that the brew is. There are different ways to control the amount of brew, as well as the size of the cup that can be produced by the machine.
The first espresso machines were steam types. The earliest espresso machines were steam types. This led to the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic machine with an electric pump. These are the things people think of when they think of an espresso machine. With a semi-automatic machine, you must grind the beans and then tamp them by hand. However, the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanised quality.
The Filter
Typically, espresso machines use a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also a vital part of the machine's temperature control, as it helps prevent overheating.
It also improves flavor, since a filter lets you enjoy a longer bloom time. This allows beans to release their flavor and gives an opportunity for a better extraction.
It is important to remember that even the best filter could result in a poor cup of coffee. The quality of the beans and the extraction process remain vital.
It's here that the magic happens. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you put the portafilter - the thingy used to place the coffee grounds in, when making espresso.
Steam-driven espresso machines make use of hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water through grounds of coffee machines espresso under high pressure. These kinds of machines tend to be less expensive and simpler to maintain than pumps-driven models. However, they are not as efficient in their ability to produce the perfect conditions for brewing, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.
In recent years, compressed air pump-driven espresso machines have been gaining popularity. They use an air compressor bean to cup espresso machine force the hot water through the grounds and are much more portable than steam-driven electric machines.
