A Proficient Rant Concerning Machine Espresso
How Does Machine Espresso Work?
Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. How does it work exactly?
In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.
The Head of the Group
The group head is the portafilter that you place in the espresso maker when making it. It disperses water into the portafilter, and then controls the pressure of the extraction. There are many different types of group heads each with its own advantages and drawbacks. Some are designed to provide stability of temperature while others are designed to handle pre-infusion. Others are built to control the lever. There are also some that contain a variety of features, such as the E61 one, which is to be the most popular among baristas because of its ability to offer multiple perks in a single package.
As you can see from the above photo, the group head is fitted with several notches. The portafilter is placed into these notches and twist the head to lock it. A gasket made of rubber is placed within the notches to create a seal as you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial to ensure an efficient extraction.
The group head does not just allow you to place your portafilter easily however, it also keeps the same temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is always at the right level for extraction. This is vital, because even a small difference in temperature can make the difference between excellent and great espresso.
The Pump
The motorized pumps used in espresso machines rotary provide nine atmospheric bars of pressure required for espresso extraction. This is different from manual piston machines which use a lever. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are typically more affordable and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to overuse and poor cleaning. They also increase the complexity of mechanical systems that can lead to a high price tag on even the most basic models.
Certain espresso machines utilize steam pressure instead of a pump for brewing espresso. The downside is that the boiler that produces steam also increases the temperature of water to boiling which can cause excessive extraction. Additionally the machines often have to rebuild their pressure between cups, which requires time and energy.
A majority of espresso machines use a vibration or rotary pump, with a vibration model using a vibrating disc to create pressure and an rotary model that pushes hot water through the grounds under high speed. Both types of machines can make excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is what makes the water warm to a temperature that is ideal to extract. The resulting steam is then transferred to the portafilter which holds the ground espresso coffee, and gets funnelled down into the cup. During this process, steam creates pressure to push through the grounds of the coffee. This creates a foam on top of the espresso. This is a sign of a great espresso.
There are three distinct types of espresso machines, each having distinct pumps and brew temperature. There are different ways in which the brew could be controlled, as well as the size of the cup the machine is capable of making.
The first espresso machines were steam types. They had one boiler to create both brew and steam, however, the pressure they could create was minimal - two bars of atmospheric pressure, at most. This led to the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic one that has an electric pump. These are what people imagine when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans by yourself, but the pump regulates the flow of water and pressure. This is a great compromise between human control and mechanised accuracy.
The Filter
Typically, espresso machines use filters to separate the grounds of coffee espresso machines when they pass through the hot water. The filter is also a vital part of the temperature control system, because it stops the machine from overheating.
It also enhances flavor, as it can allow for a longer bloom time. This allows the beans to release their flavor and gives an opportunity for a better extraction.
It is important to remember that even the best espresso machine under 200 (Recommended Studying) filter can make a bad cup of coffee. The quality of the beans, and the extraction process, remain vital.
It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you put the portafilter, the thingy that you use to put the coffee grounds into, when making espresso.
In the steam-driven espresso machine hot water is heated in an airtight tank to create steam. Steam is then pushed through the grounds at high pressure. These kinds of machines tend to be less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing, as they 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 utilize an air compressor to push hot water through grounds, and are far more portable than electric steam-driven machines.