Nine Things That Your Parent Taught You About Machine Espresso > 자유게시판

How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to make the perfect cup of coffee. What exactly is it that makes it work?

To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However the pressure is the main difference.

The Group Head

The group head is the portafilter that you insert when brewing espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are various kinds of group heads each with its unique advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. Some have a combination, such as the E61. This is a popular choice among baristas since it provides multiple benefits in a single package.

As you can see in the above photo the group head is made up of several notches to place your portafilter and then twist it with your hands to lock it in. There is also a rubber gasket in the notches to help create an airtight seal when you insert your portafilter into the machine. The notches permit an exact placement of the portafilter. This is essential for an even extraction.

The group head not only lets you to put in your portafilter easily but also maintains the temperature at a constant level. It does this by cycling hot water through the brew container and around the portafilter to ensure that it is always at the right temperature to extract. This is vital, because just a few degrees could make the difference between a good and excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure needed to extract espresso. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be less expensive and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to overuse and poor cleaning. They also add mechanical complexity that can lead to the cost of even the most basic models.

Certain espresso machines remove the pump completely and use steam pressure to brew espresso. This can result in over-extraction because the boiler that produces steam also heats the water until it comes to a boil. They also have to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines employ the rotary or vibration pump, which is a vibration model using a rotating disc to create pressure and an rotary model that pushes hot water through the grounds at high speed. Both types of machines can make excellent espresso, but Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the element which heats the water to the optimal temperature to extract. The resulting steam reaches the portafilter containing ground espresso beans and is then pumped into the cup. During this process the steam generates enough pressure to push the grounds of the coffee through. This creates a layer crema that is then poured over. This is one of the hallmarks of a great espresso.

There are three distinct types of espresso machines, each with a different type of pump and brew temperature. There are a variety of ways in which the brew could be controlled and the dimensions of the cup the machine can produce.

The first espresso machines were steam-types. They utilized one boiler to make both brew and steam, however the pressure they were able to create was minimal - two bars of atmospheric pressure at most. This resulted in the coffee tasting burnt and bitter. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most commonly used espresso machine is a semiautomatic one 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 yourself while the pump controls the water flow and pressure. This is an excellent compromise between human touch and the mechanised consistency.

The Filter

Typically, espresso machines utilize a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating.

It also improves flavor, as it allows for a more prolonged bloom time. This lets the beans release their flavors, and also allows for better extraction.

It is important to remember that even the most efficient filter can produce a bad cup of coffee. The quality of the beans, and the extraction process remain vital.

This is where the magic happens, and it's what makes an espresso really taste great. The grouphead, often referred to as the brew head, is the place where the portafilter (the container you place the coffee grounds into) is placed when making espresso and filter coffee machine.

Steam-driven espresso machines use hot water heated in an airtight container to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. However, they are limited in their ability to create the ideal brewing conditions, since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.

In recent years, espresso machines driven by compressed air-pump are becoming increasingly popular. They use an air compressor to push hot water through grounds, and are far more portable than steam-driven electric machines.