This Week's Most Remarkable Stories Concerning Machine Espresso
This Week's Most Remarkable Stories Concerning Machine Espresso
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How Does Machine Espresso Work?
Machine espresso utilizes precise pressure and mind-blowing filter technology to create the coffee we love. How exactly does it work?
Espresso is created by forcing hot water at high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However, the pressure is the primary difference.
The Group Head
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 extraction. There are many different kinds of group heads, each with their particular advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. Some are a combination, like the E61. This is a favorite among baristas because it offers multiple advantages in a single package.
As you can see in the image above the group head has a number of notches. It is possible to place your portafilter inside these notches, and then twist the head to lock it. A gasket made of rubber is placed inside the notches to help create a seal when you insert your portafilter. The notches on the head allow for an exact location of the portafilter which is essential for an efficient extraction.
The group head not only lets the portafilter to be inserted easily however, it also keeps an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is always at the right level for extraction. It is important to remember that even a few degree differences can make the distinction between a great and a excellent espresso.
The Pump
In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger before being pumped through the ground coffee inside the group head.
Pumps are generally less expensive than piston-driven machines, and they tend to last longer, however both types of machines could degrade with overuse and insufficient cleaning. They also create mechanical complexity that can lead to a high price tag on even the simplest models.
Certain espresso machines can eliminate the pump completely and make use of steam pressure to make espresso. The downside is that the same boiler that produces steam also raises the temperature of water to the point of boiling and can result in over-extraction. The machines also need to continuously rebuild their pressure between cups. This requires energy and time.
Many espresso machines use a rotary or vibration pump. A vibration model employs a vibrating disk to generate pressure, whereas the Rotary model pushes hot coffee through the ground at a high speed. Both models are capable of producing excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to the ideal temperature to extract. The resulting steam reaches the portafilter, which contains the ground espresso coffee and is then funneled down into the cup. During this process, the steam creates pressure that pushes through the coffee grounds. This produces a layer of crema on top. This is the hallmark of a good espresso.
There are three types of espresso makers, and they differ in the type of pump they employ and how hot the coffee is. There are a variety of ways to control the brew and the size of the cup that can be produced by the machine.
The earliest espresso machines were steam-based. The earliest espresso machines were steam-type machines. The coffee tasted bitter and burned. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso machine is a semiautomatic model with an electric pump. These are the images people have when they imagine an espresso machine. If you have a semi-automatic machine you must grind the beans and then tamp them by hand, but the pump provides regulated water flow and pressure. This is a perfect combination of human control and 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 a crucial element of the temperature control system because it stops the machine from overheating.
A filter can also help with flavor, as it permits an extended flowering time. This lets the beans release their nuances, and allows for better extraction.
However, it is important 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 is still crucial.
This is where the magic happens. It's what makes an espresso really taste great. The grouphead, also called the brew head, is where the portafilter (the device you put the ground coffee in) sits when you're making espresso.
In a steam-driven espresso machine hot water is heated in an airtight container to create steam, which then pushes the hot water through the grounds under high pressure. These kinds of machines are typically less expensive and simpler to maintain than pump-driven models. However, they are limited in their ability to produce the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.
In recent years, espresso machines powered more info by a compressed air compressor have become increasingly popular. They utilize an air compressor to force the hot water through the grounds and are much more portable than electric steam-driven machines.