How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. What exactly is it that makes it work?
In order to make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However it is the pressure that makes the main difference.
The Head of the Group
The name implies the group head is where you put your portafilter in when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are many different types of group heads, each with its own advantages and drawbacks. Some focus on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some include a mix of features, such as the E61 that 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 photo above the group head comes with several notches to place your portafilter and twist it manually to secure it. There is also a gasket made of rubber that resides inside the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches on the head allow for an exact placement of the portafilter, which is necessary for an even extraction.
The group head not only lets the portafilter to be inserted easily but also maintains the temperature at a constant level. This is accomplished by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level for extraction. This is important because just a few degrees could mean the difference between good and excellent espresso.
The Pump
Contrary to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure needed for espresso extraction. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pumped through the ground coffee in the group head.
Pumps tend to be less expensive than piston-driven models, and they tend to last longer, however both types of machines can get damaged through overuse and lack of cleaning. They also add mechanical complexity, which can result in the cost of even the most basic models.
Certain espresso machines utilize steam pressure instead of a pump to brew espresso. The downside is that the same boiler that produces steam also raises the temperature of water to boiling, which can lead to excessive extraction. The machines also need to continually rebuild their pressure between cups. This requires energy and time.
Many espresso machines make use of either a rotary or vibration pump, which has a vibration model using a vibrating disc to create pressure, and an rotary model that pushes hot water through the grounds under high speed. Both machines can make excellent espresso, but rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the one that will heat the water to the perfect temperature for extraction. The resulting steam is then transferred to the portafilter, which contains the ground espresso coffee, and is then pumped down into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This creates a layer crema on top. This is one of the hallmarks of a good espresso.
There are three different types of espresso machines, each with a different type of pump and the temperature of the brew. There are various ways to control the amount of brew, as well as the size of the cup that can be made by the machine.
The first espresso machines were steam type. The earliest espresso machines were steam-type machines. This led to the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso machine is a semiautomatic that has an electric pump. These are the images people have when they imagine an espresso machine. With a semi-automatic machine, you grind the beans and then tamp them by hand. The pump controls the flow of water and pressure. This is a great compromise between the human touch and mechanized consistency.
The Filter
Espresso machines typically have a filter that separates the grounds of the coffee from the hot water. The filter is also an important element of the temperature control system as it keeps the machine from overheating.
It also helps with flavor, as a filter allows for a longer bloom time. This helps the beans let their nuances out and provides an opportunity to improve extraction.
It is important to keep in mind that even the most efficient filter can make a bad cup of coffee. The quality of the beans as well as the extraction, are still crucial.
This is where the magic click here happens, it's what makes an espresso really taste great. The grouphead, also called the brew head, is where the portafilter (the container you place the ground coffee into) is placed when you're making espresso.
In the steam-driven espresso machine hot water is heated in an airtight container to create steam. This is then pushed through the grounds under high pressure. These kinds of machines are typically less expensive and easier to maintain than pump-driven models. However, they are limited in their ability to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.
In recent years, compressed-air-pump-driven espresso machines have become more popular. They utilize an air compressor to push hot water into the grounds, and are far more portable than steam-driven electric machines.