9 . What Your Parents Teach You About Machine Espresso
How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and incredible filter technology to produce the perfect cup of coffee. How does it work exactly?
Espresso is made by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.
The Head of the Group
The name implies the group head is the place you place your portafilter while brewing espresso. It distributes water into the portafilter and regulates the pressure of the extraction. There are numerous kinds of group heads each with its own advantages and disadvantages. Some are specifically designed for temperature stability while others are designed to handle pre-infusion. Others are built to control the lever. There are also some that contain a variety of features, like the E61, which is to be the most popular among baristas due to its ability to provide multiple benefits in one package.
As you can see in the above image the group head is made up of many notches in which you can put your portafilter, then twist it by hand to lock it in. There is also a rubber gasket that is a part of 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 position of the portafilter which is essential for an even extraction.
Aside from allowing you to effortlessly insert your portafilter the group head is responsible for maintaining an even temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, ensuring that the temperature is always at the right level to extract the coffee. It is crucial to keep in mind that even a few degree deviation can make the difference between a good and great espresso.
The Pump
Contrary to manual piston machines which use a lever to pressurize water, rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure needed to extract espresso. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pushed through the ground coffee in the group head.
Pumps tend to be cheaper than piston-driven models, 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 could increase the price of even the simplest models.
Some espresso machines espresso machines make use of steam pressure instead of a pump to make espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of the water to the point of boiling which could lead to over-extraction. The machines must also continually rebuild their pressure between cups. This requires energy and time.
Many espresso machines employ either a rotary or vibration pump, which is a vibration model using a rotating disc to create pressure, and an rotary model that pushes hot water through the grounds at high speed. Both machines produce great espresso but rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the element that heats the water to the ideal temperature to extract. The steam that is produced reaches the portafilter that contains the ground espresso and is then pumped into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This results in a crema on the top of the espresso. This is a hallmark of a great espresso.
There are three kinds of professional espresso machine for home machines, each with distinct pumps and brew temperature. There are various ways to control the brew as well as the size of cup that can be produced by the machine.
The first espresso machines were steam types. The earliest espresso machines were steam-type machines. The coffee tasted bitter and burned. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most commonly used espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you must grind the beans and then tamp them by hand. However, the pump regulates the flow of water and pressure. This is a great compromise between the human touch and mechanized accuracy.
The Filter
Espresso machines usually have a filter that separates the grounds of the coffee from hot water. The filter is also a vital part of the machine's temperature control, as it helps prevent overheating.
It also enhances flavor, as it can allow for a longer bloom time. This allows beans to release their flavor and gives an opportunity to improve extraction.
It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans, and the extraction process are still very important.
It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you put the portafilter, the device used to place the grounds of your coffee 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 the grounds of coffee at high pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal conditions for brewing since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.
In recent years, compressed-air-pump-driven espresso machine sale machines have become more popular. They use an air-compressor to push hot water through the ground and are more mobile than steam-driven electric espresso machines.