12 Facts About Machine Espresso To Get You Thinking About The Cooler Water Cooler
12 Facts About Machine Espresso To Get You Thinking About The Cooler Water Cooler
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How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly is it that makes it work?
Espresso is made by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Group Head
As the name suggests, the group head is where you insert your portafilter when making espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some are specifically designed for temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. There are also some that come with a range of features, such as the E61 one, which is the most popular choice among baristas due to its capacity to provide multiple benefits in one package.
As you can see from the above photo, the group head has a number of notches. The portafilter is placed in these notches, then turn the head around to secure it. A gasket made of rubber is positioned inside the notches to help create a seal when you insert your portafilter. The notches permit the precise placement of the portafilter. This is crucial for an even extraction.
The group head is not just able to allow the portafilter to be inserted easily, but it also maintains an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it is always at the correct temperature to extract. It is crucial to keep in mind that even a small variation can mean the difference between a great and a great espresso.
The Pump
The motorized pumps used in espresso machines that rotate provide the nine atmospheric bars of pressure required for espresso extraction. This differs from manual piston machines which use a lever. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are generally less expensive than piston-driven models, and they tend to last longer. However, both types of machines can degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, and can add to the cost of even the simple models.
Certain espresso machines do away with the pump entirely and use steam pressure to brew espresso. This can result in over-extraction because the boiler that makes steam also heats the water to boil. The machines must also constantly rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of an rotary or vibrating pump, which has a vibration model using a vibrating disc to generate the pressure, and rotating models that push hot water through the grounds at high speed. Both types of machines can produce an excellent espresso, but rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is what makes the water warm to the right temperature for extraction. The steam that is created reaches the portafilter, which contains the espresso coffee grounds. It is then poured into the cup. During this process the steam is able to create enough pressure to push the coffee grounds through. This results in a layer crema that is then poured over. This is the hallmark of a good espresso.
There are three distinct types of espresso machines, each with distinct pumps and brew temperature. There are various ways in which the brew can be controlled, as well as espresso makers the size of the cup the maker can create.
The first espresso machines were steam-types. They had one boiler to make steam and brew, however, the pressure they could produce was not very high - two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most commonly used espresso maker is a semi-automatic machine with an electric pump. This is what people envision when they think of an espresso maker. With a semi-automatic espresso machine, you need to grind the beans and then tamp them by hand, but the pump provides regulated water flow and pressure. This is an excellent compromise between human control and mechanised accuracy.
The Filter
Typically, espresso machines use a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also a vital component of the machine's temperature control, as it prevents overheating.
A filter also improves flavor as it allows for a longer flowering phase. This helps the beans to release their flavor and gives an opportunity for a better extraction.
It is important to remember that even the finest filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, are still very important.
It's in this area that the magic takes place. This is what makes espresso taste so delicious. The grouphead, sometimes referred to as the brewhead, is where the portafilter (the container you place the ground coffee into) sits when you're making espresso.
In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds at high pressure. These types of machines are typically less expensive and easier to maintain than pump-driven models. They are however limited in their ability to create 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 times, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air compressor to force hot water into the grounds and are significantly more portable than electric steam-driven machines.