24 Hours To Improving Machine Espresso
How Does Machine Espresso Work?
Machine espresso employs precise pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly does machines espresso machines work?
Espresso is produced by pushing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee, however the main difference lies in the pressure.
The Head of the Group
The name implies, the group head is the place you place your portafilter while making espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure of the resulting extraction. There are a variety of group heads, each with its own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. Some have a combination, such as the E61. This is a popular choice among baristas because it offers multiple advantages in one package.
As you can see in the above photo The group head features many notches in which you can place your portafilter and twist it manually to secure it. There is also a rubber gasket in the notches and helps to create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact location of the portafilter which is necessary to ensure an efficient extraction.
The group head not only lets you to place your portafilter easily but also maintains an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it's always at the right temperature to extract. This is crucial, since even a few degrees can make the difference between a good and great espresso.
The Pump
The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure required for espresso extraction. This is different from manually operated piston machines that employ a lever. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are typically less expensive than piston-driven machines, and they tend to last longer, but both types of machine can be damaged by excessive use and inadequate cleaning. They also create mechanical complexity which can result in an expensive price for even the simplest models.
Some espresso machines remove the pump completely and instead employ steam pressure to create espresso. This can cause over-extraction because the boiler that makes steam also heats the water until it comes to a boil. They also have to continuously rebuild their pressure between cups. This takes energy and time.
A large majority of espresso machines employ either a vibration or rotary pump. A vibration model makes use of an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at a high speed. Both models can make a great espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the one that is used to heat the water to the ideal temperature to extract. The steam created is then directed to the portafilter, which holds the espresso grounds. The steam is then channeled into the cup. During this process the steam generates enough pressure to push the grounds of the coffee through. This results in a layer crema that is then poured over. This is a sign of a good espresso.
There are three kinds of espresso makers, which differ in the kind of pump they use and how hot the espresso is. There are many ways to control the amount of brew, as well as the size of cup that can be produced by the machine.
The earliest espresso machines were steam-based. They employed a single boiler to make steam and brew, however, the pressure they could produce was very low - just two bars of atmospheric pressure at the most. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was created by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they picture these machines. Semi-automatic machines require you to grind and tamp the beans on your own, but the pump regulates the water flow and pressure. This is an excellent compromise between human touch and mechanized accuracy.
The Filter
Espresso machines usually use filters that separate the coffee grounds from the hot water. The filter is also an essential element of the temperature control system, as it keeps the machine from overheating.
Filters also aid in flavor since it allows for an extended flowering time. This allows the beans to release their flavors, and allows for a better extraction.
It is important to keep in mind that even the finest filter can produce a bad cup of coffee. The quality of the beans and the extraction, remain crucial.
This is where the magic happens. It's what makes espresso taste great. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you use to put the coffee grounds in, when making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through the grounds of coffee under high pressure. They are less expensive and easier to maintain than pumps-driven models. They are however limited in their ability for creating the ideal 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 become more popular. They utilize an air compressor to force the hot water through the grounds and are much more portable than steam-driven electric machines.