What is espresso coffee?
Espresso coffee is a type of coffee with strong taste, it is made with special espresso coffee maker. It has a more dense texture and contains a higher dissolved substances compared with the drip coffee, it is usually calculated by “shot”. The chemical composition of espresso coffee is complex and changeable. Many of these components will be decomposed due to temperature decreasing or oxidation. You can easily get a cup of espresso coffee from some espresso coffee machine.
It is invented and developed in Italy in the early 20th century, it is a single drink produced by the vapor pressure until the mid 1940s. It is transformed into today’s espresso drinks with the production of spring piston lever coffee machine, and then it is commercialized successfully.
Peculiarities of espresso coffee drinks
If be made correctly, there will be some crema, a kind of reddish-brown foam, floating on the surface of the espresso coffee. The crema is made of vegetable oil, protein and carbohydrates. It has combined both of the emulsion and foam colloid. The espresso coffee has unique flavor due to the short-time and high-pressure brewing process and the taste is denser than some other drip coffee. However, caffeine is also less as a result of short-time boiling. The espresso coffee is usually used as base of some other drinks, such as latte, cappuccino, and mocha, without diluting coffee ingredients overly.
Structure of espresso makers
It seems that the components of espresso maker are complex, but actually, it is very easy to understand. It has a cell used to store the water, and then the pump will pump the water out from this cell to heating chamber. The heating chamber is a strong stainless steel structure, there is a heating device placed in the grooves in the bottom. This thermal resistance device is a simple metal coil, similar to filament of the light bulb. That means once get though the power, it can get hot. The coil is embedded in the rubber tube which makes it more durable. Heating chamber has a one-way valve, which can only pump the water into the heating room and will not return from the heating chamber to the pump.
Filter of the espresso coffee maker is used to put the movable parts of coffee powder. There is a small removable net in the pressure filling device, used to place the coffee powder. The espresso will be out from two exits at the bottom. Steam wand is used to heat and make the foam for different espresso drinks. When the users adjust the valve to the steam position, the milk will be pumped from the bar by the team caused by heating container. Control panel of the espresso maker includes switches, two lights and a control valve. It also has two fine-tuning switch, they control the pump and heating device, respectively.
How espresso machines work?
Firstly, I want to tell you some important but changeable factors during the making process of the espresso coffee. They are the temperature, pressure, the fineness and compaction of coffee powder, etc. The espresso makers must control these factors.
For this type of espresso coffee machine, coffee is placed in a funnel-shaped metal container. Put some water into it, and then cover it tightly. During the heating process of water, the container will generate pressure inside. The pressure will be released though a tube, and then the coffee, and come out finally from the top of tube. Since the end of the tube is in the water, pressures impel hot water upward flow along the pipe. This kind of espresso makers have several disadvantages, for example, the pressure of the system depends on water temperature, and temperature caused by pressure may be higher than the desired temperature.
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