Why does Espresso use 9bar? What is the effect of stress on espresso?

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Guide reading

As we all know, espresso is the base of espresso. The taste of espresso is affected to some extent by espresso. Delicious espresso often needs a properly extracted espresso base, so the importance of espresso is self-evident.

The steps for making espresso are actually very simple, but there are many details to pay attention to when making espresso. The first step is to make sure that the beans are fresh enough and the beans are fully nourished. The first step is to remove the handle and wipe the powder bowl clean. The second step is to grind the coffee beans and drop the coffee powder into the powder bowl on the handle. The third step is cloth powder and filling pressure, the fourth step is to buckle the handle for extraction, and finally is to end the extraction, take off the handle for cleaning.

It seems simple, but there are many details that need to be paid attention to. Make sure the powder bowl is clean and dry before receiving the powder, keep the coffee powder evenly distributed in the powder bowl when receiving the powder and cloth powder, and make the coffee powder vertically downward, and each time the pressure should be consistent, etc., so it is not difficult to learn to make a cup of espresso, but to make a good cup of espresso and every cup of espresso requires more study and practice.

But today, Qianjie Coffee has to share not only espresso, but also a major element of espresso, the pressure of making espresso.

Characteristics of espresso-pressurized extraction

Common hand-brewed coffee, such as coffee brewed in a v60 filter cup, generally boils down to trickling extraction, while we call it immersion extraction, which relies on the flow of water to bring out the coffee substance, while immersion extraction relies on soaking to directly extract the taste of the coffee. However, it is difficult for us to classify espresso into the above two categories. Compared with most brewing methods, the greatest feature of espresso is the pressure of extraction.

When making espresso, 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 time for making espresso is very short, with an average of 2 to 3 minutes for hand brewing, 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.

The product of pressure-- Crema

Because of the pressure, espresso also has an attractive layer of oil on its appearance. In the process of extraction, the hot water passes through the coffee pressed powder, and the carbon dioxide in the coffee powder is under too much pressure, so the water shows a state of supersaturation for the carbon dioxide, and the carbon dioxide has no way to be released and melts directly into the coffee liquid, and the high-pressure environment also forces the fat in the coffee to break away from the coffee pressed powder and is brought out by the hot water.

After the extraction, the coffee liquid flowed out of the coffee machine, and the atmospheric pressure returned to normal, and the carbon dioxide left in the coffee liquid was ready to return to the air, but encountered the fat in the coffee liquid during the regression process. Fat surrounds carbon dioxide and floats on the surface of coffee liquid, which is why this layer of fat (Crema) is produced.

The oil of espresso is mainly affected by several factors, namely, the freshness of coffee beans, the baking degree of coffee beans and the extraction degree of coffee beans. The fresher the coffee beans are, the more carbon dioxide they contain, the more abundant the oil; similarly, the deeper the roasting, the more abundant the oil.

In addition to these, the oil of espresso is also affected by the pressure of the coffee machine. The production of oil mainly depends on the high-pressure extraction environment. If the pressure is not enough, the fat in the coffee beans will be reduced, and the oil will naturally be less.

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