12 Facts About Machine Espresso To Refresh Your Eyes At The Cooler Water Cooler
12 Facts About Machine Espresso To Refresh Your Eyes At The Cooler Water Cooler
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How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How exactly does 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 the main difference lies in the pressure.
The Group Head
The group head is the portafilter that is inserted when you are making espresso. It distributes water into the portafilter, and regulates the pressure during the extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are designed for the stability of temperature while some are designed to handle pre-infusion. Others are made to control the lever. Some are a combination, such as the E61. This is a popular choice among baristas because it offers multiple benefits in one package.
As you can see in the above image The group head features several notches to place your portafilter and then twist it with your hands to secure it. A gasket made of rubber is positioned in the notches to make a seal when you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is necessary for an efficient extraction.
The group head is not just able to allow you to place your portafilter easily, but it also maintains the temperature at a constant level. It does this by circulating hot water through the brew container and around the portafilter to ensure that it is always at the right temperature to extract. It is important to realize that even a tiny difference can make the difference between a good and great espresso.
The Pump
In contrast to piston machines that are manually operated, which use a lever to pressurize water, rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee in the group head.
Pumps are typically less expensive than piston-driven machines and tend to last longer. However, both types of machines could become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which can raise the cost of even the simple models.
Some espresso machines make use of steam pressure instead of a pump to make espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. In addition these machines are often required to restore their pressure between cups, which takes time and energy.
Many espresso machines make use of either a rotary or vibration pump, which is a vibration model using a vibrating disc to generate the pressure, and the rotary model pushing hot water through the grounds under high speed. Both machines produce great espresso however rotary machines tend to be more quiet, durable and less likely to break down.
The Boiler
The boiler is the component that heats the water to the ideal temperature to extract. The steam that is produced reaches the portafilter containing the ground espresso coffee and is then pumped down into the cup. The steam causes enough pressure to push the grounds of the coffee through. This results in a layer of crema on top. This is one of the main characteristics of a great espresso.
There are three different types of espresso machines, each with different pumps and the temperature of the brew. There are also different ways that the brew can be controlled as well as the dimensions of the cup the machine can produce.
The first espresso machines were steam-types. They used one boiler to make both steam and brew, however the pressure they were able to produce was very low - just two bars espresso machine of atmospheric pressure at most. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they imagine these machines. If you have a semi-automatic machine you grind the beans and tamp them yourself but the pump provides regulated water flow and pressure. This is an excellent compromise between human touch and the mechanised accuracy.
The Filter
Typically, espresso machines utilize filters that separate the grounds of coffee when they pass through the hot water. The filter is also an important part of the temperature control system as it prevents the machine from overheating.
It also improves flavor, since a filter lets you enjoy a longer bloom time. This allows the beans to release their nuances, and also allows for better extraction.
It is important to remember that even the most efficient 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, and it's what makes an espresso really taste good. The grouphead, sometimes referred to as the brew head, is the place where the portafilter (the container you place the ground coffee in) is located when you're making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. Steam then pushes the hot water through the grounds with high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited to create the perfect brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They use an air-compressor to force hot water into the ground, and are more mobile than electric steam-driven espresso machines.