How Does Machine Espresso Work?
The machine espresso utilizes precision pressure, and filtering system that is awe-inspiring to make the coffee you love. What exactly is it?
To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the main difference.
The Group Head
The name implies the group head is where you place your portafilter while making 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 their 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. Some come with a combination of both, like the E61. This is a very popular choice for baristas since it provides multiple advantages in one package.
As you can see in the above photo, the group head is fitted with several notches. You place your portafilter in these notches and then twist the head to secure it. A gasket made of rubber is positioned inside the notches to help make a seal when you insert your portafilter. The notches permit the precise placement of the portafilter. This is essential for an accurate extraction.
Apart from allowing you effortlessly insert your portafilter the group head is responsible to maintain an even temperature. It does this by circulating hot water through the brew pan and around the portafilter, making sure that it is always at the right temperature to extract. This is important, as even a few degrees can make the difference between excellent and great espresso.
The Pump
The motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines which use a lever. The pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior to it is shot through the ground coffee inside the group head.
Pumps tend to be cheaper than piston-driven machines, and tend to last longer, but both types of machine can be damaged by excessive use and inadequate cleaning. They also increase the complexity of mechanical systems which can result in costly prices for even the simplest models.
Certain espresso machines eliminate the pump entirely and employ steam pressure to create espresso. This can result in over-extraction because the boiler that produces steam also causes the water to boil. The machines must also continuously rebuild their pressure between cups. This requires energy and time.
A large majority of espresso machines employ a rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while the circular model pushes hot liquid through the ground at high speed. Both machines can website produce excellent espresso, but rotary machines are more quiet, durable and less likely to break.
The Boiler
The boiler is the one that heats the water to the right temperature to extract. The resulting steam reaches the portafilter which holds the ground espresso coffee and is then pumped into the cup. The steam causes pressure to push 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 kinds of espresso makers, and they differ in the type of pump they use and how hot the brew is. There are various ways to control the amount of brew, as well as the size of cup that can be made by the machine.
The earliest espresso machines were steam types. They used a single boiler to make both steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic one with an electric pump. These are the images people have when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp your beans yourself The pump, however, regulates the flow of water and pressure. This is a fantastic compromise between human control and mechanised consistency.
The Filter
Typically, espresso machines employ filters to separate the coffee grounds as they pass through the hot water. The filter is also an essential part of the machine's temperature control, as it prevents overheating.
A filter also improves flavor because it allows for a longer flowering period. This allows the beans to release their nuances, and allows for a better extraction.
However it is crucial to remember that even a good filter could result in a bad cup of coffee, because the quality of the beans and extraction is essential.
This is where the magic happens. It's what makes espresso taste great. The grouphead, sometimes referred to as the brew head, is where the portafilter (the container you place the coffee ground into) sits when you're making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then pushes hot water through grounds of coffee under high pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. However, they are not as efficient in their ability to create the ideal brewing conditions, because they operate at 1-1.5 bars of pressure. While 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 force hot water through grounds and are much more portable than electric steam-driven machines.