Espresso is the base for making Italian coffee such as Americano, Latte, etc. The biggest feature of the espresso is the rich golden coffee oil (Crema) on the surface. Front Street Coffee This article will discuss the extraction mystery of the next espresso machine.
How is the oil in espresso produced?
Normal atmospheric pressure brewing cannot produce golden brown coffee fat. When the coffee machine extracts espresso, the coffee powder is ground to a very fine point and extracted under a pressure of up to 9 bar. When the hot water passes through the coffee powder, the carbon dioxide in the coffee powder is too pressurized, and the water is supersaturated with the carbon dioxide. There is no way for the carbon dioxide to be released directly into the coffee liquid. The high pressure also forces the oil contained in the coffee to break away from the coffee powder, which is then carried out by the hot water.
After the coffee is extracted, when the coffee liquid flows out of the coffee machine, the atmospheric pressure also returns to normal, and this carbon dioxide still remains in the coffee liquid. Also preparing to return to the air, the carbon dioxide encounters the grease in the coffee liquid. The grease traps the carbon dioxide ready to be returned to the air. So that's why this layer of crema comes into being.
Therefore, we know that it is the pressurized extraction of the espresso machine that creates the richness of the espresso.
How much pressure does a coffee machine take to make espresso?
When Qianjie is making espresso, the coffee powder in the handle powder bowl will be extracted under the pressure of 9bar, and the substances in the coffee powder will be quickly dissolved under the pressure, so the espresso production time is very short, and the hand-brewed coffee is average. It takes 2 to 3 minutes, while espresso is more likely to be brewed in 20 to 30 seconds. This brewing method also allows us to classify espresso as a "pressurized brew".
The coffee machine for making espresso mainly relies on the pump to provide pressure, which is mainly divided into two types: vibration pump and rotary pump. The vibration pump generates pressure through repeated vibration at high speed through a structure similar to a piston. , the pressure cannot be guaranteed to be stable at 9bar during the entire extraction process.
The rotary pump generates pressure through the high-speed rotation of the metal sheet. Compared with the vibration pump, it has no reciprocating motion, lower noise, longer life, and pressure in one step. Therefore, commercial coffee machines are generally based on rotary pumps, which continuously produce cups. better stability.
How does an under- or over-pressurized espresso machine affect coffee?
Under normal circumstances, if the extraction pressure of the coffee machine is less than 9 bar, the extraction efficiency will be reduced, and the performance of the coffee fat will tend to be thin and light. When the pressure is greater than 9 bar, the extraction efficiency will be improved, which may cause the espresso to be bitter. Of course, this is based on extraction parameters at a pressure of 9 bar.
What are the reasons for insufficient extraction pressure in a coffee machine?
In the absence of a malfunction of the coffee machine itself, Front Street believes these reasons may occur:
1. Insufficient heating time, insufficient boiler water temperature, and insufficient steam, so the pressure is insufficient.
2. The boiler capacity of the coffee machine is small. After continuous production or a large amount of hot water is used, the boiler will be refilled with water, and the pressure will also be insufficient.
3. The boiler pressure of the coffee machine is low at the factory setting, which causes the steam pressure of the coffee machine to be insufficient under any circumstances. You need to find the after-sales service to readjust the pressure for you.
