Unstable extraction pressure adjustment method of coffee machine Coffee mechanism for coffee skill teaching

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Espresso is the base for making espresso such as American coffee and latte. The most important feature of espresso is that it has rich golden coffee oil (Crema) on the surface. Qianjie Coffee this article is to explore the mystery of Italian coffee machine extraction. How the oil of espresso is produced at normal atmospheric pressure, there is no golden coffee oil. When the coffee machine extracts espresso, the coffee powder is ground to very fine and extracted under pressure up to 9bar. When the hot water passes through the coffee pressed powder, the carbon dioxide in the coffee powder is under too much pressure, and the water is supersaturated for the carbon dioxide. There is no way to release the carbon dioxide and melt directly into the coffee liquid. The high pressure also forces the oil in the coffee to detach from the coffee pressed powder and is brought out by the hot water. After the coffee is extracted, when the coffee liquid flows out of the coffee machine, the atmospheric pressure returns to normal, and the carbon dioxide that remains in the coffee liquid. When it was ready to return to the air, the carbon dioxide encountered the oil in the coffee liquid. The grease wraps the carbon dioxide that is ready to return to the air. So this is why this layer of oil (Crema) is produced.

Therefore, we know that the rich oil in espresso is due to the pressurized extraction of espresso machines. How much pressure does the coffee mechanism have to make espresso? When making espresso in Qianjie, the coffee powder in the handle powder bowl is extracted under the pressure of 9bar, and the substance in the coffee powder is quickly dissolved under pressure, so the production time of espresso is very short. It takes an average of 2 to 3 minutes to brew coffee by hand, while espresso can be extracted in 20 to 30 seconds. This method of extraction also allows us to classify espresso as "pressurized extraction". The coffee machine for making espresso mainly relies on pumps to provide pressure, which is mainly divided into two types: vibration pump and rotary pump. Vibration pump produces pressure through high-speed repeated vibration similar to the structure of pistons, but the disadvantages are high noise, short life, and the pressure is gradually increasing, so it is impossible to ensure that the pressure is stable at 9bar in the whole extraction process.

The rotary pump produces pressure through the high-speed rotation of the metal sheet, compared with the vibration pump, there is no reciprocating movement, the noise is lower, the life is longer, and the pressure is in place in one step, so the commercial coffee machine is generally based on the rotary pump, and the stability of the continuous cup is better. What is the effect of insufficient or excessive stress in Italian coffee machine on coffee? Under normal circumstances, if the extraction pressure of the coffee machine is less than 9bar, the extraction efficiency will be reduced, and the coffee oil will tend to be thin and light color. When the pressure is greater than 9bar, it will improve the extraction efficiency, which may cause espresso bitterness. Of course, this is based on the pressure of the extraction parameters for 9bar.

What are the reasons for the insufficient extraction pressure of the coffee machine? In the case of no failure of the coffee machine itself, Qianjie believes that these reasons may occur: 1, insufficient heating time, insufficient boiler water temperature, insufficient steam, so insufficient pressure. 2, coffee machine boiler capacity is small, continuous production or a large number of hot water, the boiler re-water, there will be insufficient pressure. 3. The boiler pressure of the coffee machine is low when it leaves the factory, so that the steam pressure of the coffee machine is not strong enough no matter what the situation. Need to find after-sale to re-adjust the pressure for you.

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