12 Companies Setting The Standard In Machine Espresso
How Does Machine Espresso Work?
Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. What exactly does it work?
To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the key difference is in the pressure.
The Group Head
The name implies, the group head is the place you insert your portafilter when brewing espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are several different types of group head each with its distinct advantages and drawbacks. Some are designed to provide stability in temperature, while others are designed to handle pre-infusion. Some are designed to control the lever. There are some that have a combination of features, such as the E61 that is to be the most popular among baristas due to its ability to offer multiple perks in a single package.
As you can see from the photo above the head of the group is fitted with a variety of notches. The portafilter is placed in these notches, then twist the head to lock it. There is also a gasket made of rubber which is located inside the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches on the head permit an exact position of the portafilter which is necessary for an efficient extraction.
The group head is not just able to allow you to insert your portafilter easily however, it also keeps the temperature at a constant level. This is done 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 that are used in rotary espresso machines for home machines supply the nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines which use a lever. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.
Pumps are generally less expensive than piston-driven machines and tend to last longer, however both types of machines can be damaged by excessive use and inadequate cleaning. They also create mechanical complexity which can result in costly prices for even the most basic models.
Some espresso machines remove the pump completely and instead make use of steam pressure to make espresso. This can result in over-extraction because the boiler that makes steam also heats the water to boil. They also have to continuously rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of an rotary or vibrating pump, with a vibration model that uses a vibrating disc to create the pressure, and rotating models that push hot water through the grounds under high speed. Both types of machine can make a great espresso, but the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to the optimal temperature for extraction. The resulting steam reaches the portafilter, which contains the ground espresso coffee, and gets funnelled down into the cup. During this process the steam causes enough pressure to push the grounds of coffee through. This creates a foam on top of the espresso. This is one of the hallmarks of a great espresso.
There are three kinds of espresso makers. They differ in the kind of pump they use and the degree of heat that the coffee is. There are various ways in which the brew can be controlled and the dimensions of the cup the machine is capable of making.
The first espresso coffee maker machines were steam-type. They employed one boiler to create steam and brew, however, the pressure they could generate was low - only two bars of atmospheric pressure at most. The coffee tasted bitter and burned. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso Machines home machine.
The most commonly used espresso maker is a semiautomatic machine with an electric pump. These are the images people have when they think of an espresso maker. If you have a semi-automatic machine you have to grind the beans and tamp them by hand. The pump regulates the flow of water and pressure. This is a perfect compromise between human control and mechanized consistency.
The Filter
Typically, espresso machines have a filter to separate out the grounds of coffee as they move through the hot water. The filter is also an essential element of the temperature control system, as it keeps the machine from overheating.
A filter also improves flavor, as it permits the beans to flower for a longer period of time. This allows the beans to release their nuances and gives an opportunity for a better extraction.
It is important to remember that even the best filter can produce a bad cup of coffee. The quality of the beans, as well as the extraction, remain vital.
It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead, sometimes called the brew head, is the place where the portafilter (the thingy you put the coffee grounds into) is placed when you're making espresso.
In a steam-driven espresso machine hot water is heated in an airtight container to create steam. This is then pushed through the grounds under high pressure. They are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machine sale machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water through the grounds and are more portable than steam-driven electric machines.