Notes

Where Will Machine Espresso Be One Year From This Year?
How Does Machine Espresso Work?

Machine espresso employs precise pressure and amazing filter technology to make the coffee we love. How exactly does it work?

Espresso is made by forcing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee. However, the pressure is the primary difference.

The Group Head

The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure of the resulting extraction. There are a variety of types of group head each with its distinct advantages and disadvantages. Some are designed to provide stability of temperature while others are built to handle pre-infusion. Others are made to control the lever. Some include a combination such as the E61. This is a very popular choice for baristas since it provides multiple benefits in one package.

As you can see in the above photo, the group head has several notches where you put your portafilter, then twist it by hand to secure it. A gasket of rubber is situated within the notches to create a seal when you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is vital for an efficient extraction.

The group head not only allows you to place your portafilter easily, but it also maintains the temperature at a constant level. It does this by cycling hot water through the brew basket, and around the portafilter, ensuring that it's always at the right temperature to extract. This is vital, because just a few degrees could mean the difference between good and excellent espresso.


The Pump

The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure required to extract espresso. 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 tend to be more affordable and last longer than piston-driven machines. However, both types of machines can degrade because of frequent use and poor cleaning. They also add mechanical complexity that can lead to costly prices for even the simplest models.

Some espresso machines make use of steam pressure instead of a pump to make espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of water until it reaches boiling which could lead to excessive extraction. In addition these machines are often required to restore their pressure between cups, which takes time and energy.

Many espresso machines make use of a rotary or vibration pump. automatic espresso machine employs a vibrating disk to generate pressure, whereas the Rotary model pushes hot coffee through the ground at high speed. Both machines produce great espresso, however rotary machines are more quiet, durable and less likely to fail.

The Boiler

The boiler is the part which heats the water to the ideal temperature for extraction. The steam that is produced reaches the portafilter which holds ground espresso beans and is then funneled down 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 the hallmark of a great espresso.

There are three types of espresso makers. They differ in the kind of pump they use and how hot the espresso is. There are different ways to control the amount of brew, as well as the size of cup that can be made by the machine.

The first espresso machines were steam type. They utilized one boiler to create both steam and brew but 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 commonly used espresso machine is a semiautomatic that has an electric pump. These are what people imagine when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a great compromise between the human touch and the mechanised quality.

The Filter

Typically, espresso machines employ filters to separate the grounds of coffee when they pass through the hot water. The filter is also an essential part of the machine's temperature control, since it helps to prevent overheating.

It also improves flavor, as a filter allows for a more prolonged bloom phase. This helps the beans release their flavor and gives an opportunity to improve extraction.

It is important to keep in mind that even the best filter could result in a poor cup of coffee. The quality of the beans, and the extraction, are still crucial.

It's here that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you place the portafilter - the thingy that you put the grounds of your coffee into when making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through grounds of the coffee under pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, compressed air-driven espresso machines have become more popular. They utilize an air compressor to push hot water across the ground and are more mobile than electric steam-driven espresso machines.

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