How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to make the perfect cup of coffee. How exactly does it work?
To make an espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference.
The Head of the Group
As the name suggests, the group head is where you place your portafilter when brewing espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the resulting extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. There are some that come with a range of features, such as the E61, which is considered to be the most popular among baristas due to its ability to offer multiple benefits in one package.
As you can see from the photo above the group head is fitted with a variety of notches. You can place your portafilter into these notches and twist the head to lock it. There is also a gasket made of rubber in the notches and helps to create a seal when you insert your portafilter into the machine. The notches on the head allow for an exact positioning of the portafilter which is crucial for a consistent extraction.
Aside from allowing you to easily connect your portafilter, the group head is also responsible to ensure that the temperature remains even. This is achieved by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is constant for extraction. This is important because even a few degrees can be the difference between a excellent and great espresso.
The Pump
In contrast to manual piston machines which rely on a lever to pressurize water, rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being pumped through the ground coffee in the group head.
Pumps are generally less expensive than piston-driven machines, and tend to last longer. However, both types of machine can become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which can raise prices of even most basic models.
Certain espresso machines can eliminate the pump completely best home espresso machine and instead employ steam pressure to create espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of water to the point of boiling, which can lead to over-extraction. The machines must also continually rebuild their pressure between cups. This takes energy and time.
Many espresso machines utilize either a rotary or vibration pump, which has a vibration model that uses a vibrating disc to create pressure and the rotary model pushing hot water through the grounds at high speed. Both machines produce great espresso, however rotary machines are quieter, more durable and less likely to break.
The Boiler
The boiler is the component which heats the water to the optimal temperature for extraction. The steam created reaches the portafilter, which contains the espresso coffee grounds. It is then poured into the cup. The steam causes enough pressure to push the grounds of coffee through. This creates a foam on the top of the espresso. This is a hallmark of a great espresso.
There are three types of espresso makers, which differ in the type of pump they employ and how hot the espresso is. There are different ways to control the brew and the size of the cup that can be made by the machine.
The first espresso machines were steam-types. They utilized one boiler to make steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure at the most. 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 maker is a semiautomatic machine that has an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic machine you must grind the beans and tamp them by hand, but the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized consistency.
The Filter
Typically, espresso machines use filters that separate the grounds of coffee as they move through the hot water. The filter is also an essential component of the temperature control system as it keeps the machine from overheating.
It also improves flavor, as a filter allows for a longer bloom time. This allows beans to release their flavor and gives the chance for 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, as well as the extraction, are still crucial.
This is where the magic happens. It's what makes an espresso really taste good. The grouphead, also called the brew head, is where the portafilter (the device you put the coffee grounds into) is located when you're making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds at a high pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect brewing conditions because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.
In recent years, compressed-air-pump-driven espresso machines have become more popular. They utilize an air compressor to push hot water through the grounds and are more portable than electric steam-driven machines.