How Does Machine Espresso Work?
The machine espresso utilizes precise pressure, as well as a filtering technology that is amazing to make the coffee you enjoy. What exactly is it?
In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the difference is in the pressure.
The Head of the Group
As the name implies, the group head is where you place your portafilter while making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure that results from the extraction. There are numerous kinds of group heads each with its own advantages and disadvantages. Some are designed to provide stability in temperature, while others are designed to handle pre-infusion. Others are built to control the lever. Some have a combination, such as the E61. This is a preferred choice for baristas because it offers multiple advantages in a single package.
As coffee machine espresso can see in the above photo the head of the group is fitted with several notches. You place your portafilter into these notches and twist the head to lock it. A rubber gasket is located inside the notches, which helps create a seal while you insert your portafilter. The notches on the head permit a precise location of the portafilter which is necessary to ensure an even extraction.
The group head not only lets you to insert your portafilter easily however, it also keeps a constant temperature. This is achieved by cycling hot water around the portafilter, and through the brew basin, ensuring the temperature is always right for extraction. It is important to note that even a small differences can make the distinction between a great and a great espresso.
The Pump
Unlike manual piston machines, which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pushed through the ground coffee inside the group head.
Pumps are typically less expensive and last for longer than piston-driven machines. However, both kinds of machines may degrade due to overuse and inadequate cleaning. They also create mechanical complexity which can result in costly prices for even the most basic models.
Certain espresso machines remove the pump completely and employ steam pressure to create espresso. The downside is that the same boiler that produces steam also raises the temperature of the water to the point of boiling, which can lead to over-extraction. They also have to 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 generate the pressure and a rotary model pushing hot water through the grounds at high speed. Both machines produce great espresso, but rotary machines are more stable, quieter and less likely to fail.
The Boiler
The boiler is the part that heats the water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter that contains ground espresso beans and gets funnelled down into the cup. During this process the steam is able to create enough pressure to push the coffee grounds through. This results in a whipped-up top of the espresso. This is a sign of a good espresso.
There are three types of espresso machines, each with a different type of pump and the temperature of the brew. There are a variety of ways to control the strength of the brew and the size of the cup that can be made by the machine.
The first espresso machines were steam-type. They had one boiler to create steam and brew, however, the pressure they could create was minimal - two bars of atmospheric pressure at the most. The coffee tasted bitter and burned. This is the reason Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most commonly used espresso maker is a semi-automatic device that has an electric pump. This is what people envision when they think of an espresso maker. With a semi-automatic machine you need to grind the beans and tamp them by hand. The pump is able to regulate the flow of water and pressure. This is a perfect compromise between human control and mechanized accuracy.
The Filter
Typically, espresso machines employ filters that separate the coffee grounds as 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, as a filter can allow for a longer bloom phase. This allows the beans to let their nuances out, and allows for a better extraction.
It is important to keep in mind that even the finest filter can result in a bad cup of coffee. The quality of the beans, and the extraction process remain crucial.
It's in this area 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 that you use to put the coffee grounds into, when making espresso.
Steam-driven espresso machines make use of hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through coffee grounds under high pressure. They are less expensive and easier for the owner to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal brewing conditions, 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 been gaining popularity. They use an air compressor to push hot water across the ground. They are also more mobile than steam-driven electric espresso machines.