How Does Machine Espresso Work?
Machine espresso employs precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. What exactly does it work?
Espresso is produced by pushing hot water at high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.
The Head of the Group
The name implies, the group head is the place you place your portafilter while brewing espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. There are some that have a combination of features, such as the E61, which is considered the classic choice among many baristas for its ability to offer multiple benefits in a single package.
As you can see in the picture above the head of the group is fitted with a variety of notches. You place your portafilter into these notches and twist the head to lock it. There is also a gasket made from rubber that resides inside the notches, which helps create the seal when you insert your portafilter into the machine. The notches allow for precise placement of your portafilter. This is vital for an efficient extraction.
In addition to allowing you easily place your portafilter in, the group head is responsible for maintaining an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it is always at the correct temperature for extraction. It is important to remember that even a few degree deviation can make the difference between a good and great espresso.
The Pump
Motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure required for espresso extraction. This differs from manual piston machines which use a lever. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pushed through the ground coffee in the group head.
Pumps are typically more affordable and last longer than piston-driven machines. However, best portable espresso makers of machines can degrade due to overuse and inadequate cleaning. Pumps are also more complicated mechanically, which could increase prices of even simple models.
Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. This can cause over-extraction because the boiler that produces steam also causes the water to boil. Additionally these machines are often required to restore their pressure between cups, which requires time and energy.
A majority of espresso machines utilize a rotary or vibration pump. A vibration model uses a vibrating disk to generate pressure, while the rotating model pushes hot water through the ground at high speed. Both machines can make excellent espresso, but rotary machines are quieter, more durable and less likely to break.
The Boiler
The boiler is used to heat the water to the perfect temperature to extract. The steam created is then directed to the portafilter, which is a container for espresso grounds. It is then pumped into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This results in a whipped-up top of the espresso. This is a sign of a great espresso.
There are three kinds of espresso makers, and they differ in the type of pump they use and the degree of heat that the brew is. There are also different ways in which the brew could be controlled as well as the size of the cup the machine can produce.
The earliest espresso machines were steam types. The earliest espresso machines were steam types. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most common espresso maker is a semi-automatic one that has an electric pump. These are the things people think of when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp your beans yourself while the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized consistency.
The Filter
Espresso machines typically have filters that separate the grounds of the coffee from hot water. The filter is also a vital part of the machine's temperature control, since it helps to prevent overheating.
It also enhances flavor, since a filter allows for a longer bloom time. This allows the beans to let their nuances out, and allows for a better extraction.
It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans and the extraction process, are still very important.
This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter, which is the thingy which you put the coffee grounds in, while making espresso.
Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These types of machines tend to be less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to produce the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.
In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They make use of an air compressor to push hot water across the ground. They are also more mobile than electric steam-driven espresso machines.