9 Things Your Parents Taught You About Machine Espresso
How Does Machine Espresso Work?
Machine espresso makes use of precise pressure and amazing filter technology to make the coffee we love. How does it work exactly?
Espresso is created by forcing hot water at High End Espresso machine pressure through finely-ground coffee espresso machines. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.
The Head of the Group
The group head is the portafilter that you put in when making espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are a variety of group heads each with their own advantages and disadvantages. Some focus on temperature stability, others on pre-infusion options, and others are designed to control the lever. There are even some that contain a variety of features, such as the E61 that is the most popular choice among baristas due to its capacity to offer multiple perks in one package.
As you can see from the image above the head of the group has a number of notches. You place your portafilter into these notches and twist the head to lock it. There is also a rubber gasket that is a part of the notches to help create the seal when you insert your portafilter into the machine. The notches permit precise placement of the portafilter. This is vital for an accurate extraction.
The group head does not just allow you to insert your portafilter easily however it also keeps the temperature at a constant level. This is done by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is constant for extraction. This is important because even a few degrees can mean the difference between good and excellent discount espresso machines.
The Pump
The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure required to extract espresso. This is different from manual piston machines which use levers. The pressure builds up by removing 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 less expensive than piston-driven machines, and they tend to last longer. However, both types of machine can become damaged due to excessive use and poor cleaning. They also create mechanical complexity and can lead to costly prices for even the most basic models.
Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of the water to boiling and can result in excessive extraction. The machines must also constantly rebuild their pressure in between cups. This takes energy and time.
Many espresso machines make use of a rotary or vibration pump. A vibration model makes use of a rotating disk to generate pressure, while the rotary model pushes hot water through the ground at high speed. Both machines can make excellent espresso, however rotary machines are more quiet, durable and less likely to break.
The Boiler
The boiler is the element that heats water to an optimal temperature for extraction. The steam produced reaches the portafilter, which holds the espresso grounds. It is then funneled into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This results in a crema on the top of the espresso. This is a sign of a good compact espresso machine.
There are three types of espresso makers, and they differ in the type of pump they use and how hot the espresso is. There are various ways to control the brew as well as the size of the cup that can be produced by the machine.
The first espresso machines were steam-type. They used one boiler to create steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure at most. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most common espresso maker is a semiautomatic machine that has an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans yourself while the pump controls the flow of water and pressure. This is a perfect solution that combines human control with mechanized accuracy.
The Filter
Typically, espresso machines employ filters to separate the grounds of coffee as they move through the hot water. The filter is also an essential element of the machine's temperature control, since it stops overheating.
A filter also helps with flavor because it allows for an extended flowering time. This allows the beans to release their flavor and allows for better extraction.
However it is crucial to keep in mind that even a high-quality filter can make a terrible cup of coffee, because the quality of the beans and extraction are vital.
This is where the magic happens. It's what makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter, the device used to place the coffee grounds into, when making espresso.
In the steam-driven espresso machine hot water is heated in an airtight container to produce steam, which is then pushed through the grounds under high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air pump-driven espresso machines have been gaining popularity. They use an air compressor to push the hot water through the grounds and are more portable than steam-driven electric machines.