Cognition of hand-brewed coffee: what is the steaming of hand-brewed coffee?

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"stuffy steaming" is a process in which coffee powder releases carbon dioxide quickly after contact with water, known as bloom in English, and blossoms agree that it occurs only when brewing fresh coffee.

It is also a great pleasure to observe the expansion of powder. The length of steaming time depends on the roasting degree of the coffee, and it also affects the coffee brewed out, making the flavor more divided.

Exhaust gas

Coffee beans continue to emit carbon dioxide after roasting, a process called "exhaust". Most of the carbon dioxide will be released quickly after baking, especially within four hours after baking, and the remaining gas will be released continuously over the next few weeks, during which time the amount of gas released will gradually decrease.

When the coffee beans are ground into powder, it will accelerate carbon dioxide emissions, because the surface area of the coffee powder is greatly increased, which in turn affects the release of gas. Many stores' coffee will be discarded if it is not used ten minutes after grinding. )

Stuffy steam

In the first stage of making coffee, you only need to inject a little hot water first. when the hot water comes into contact with the coffee powder, it will accelerate the carbon dioxide emission of the coffee powder, and you can clearly see that the surface of the coffee powder is bubbling, but once again, the degree of expansion does not represent the freshness of the coffee.

The deeper coffee has a lower moisture content, and when it comes into contact with water, it will absorb water and release more gas, thus allowing a greater degree of expansion.

Shallow coffee has a higher moisture content, less water absorption and less gas release when it comes into contact with water, so it is less likely to expand.

This program is called "Bloom".

Expansion

The steaming time is usually 20-30 seconds. Once the steaming time is over, hot water should be injected immediately. The judgment point of the end is when the powder expansion is the highest and has not yet collapsed. If you have a scale, you can inject hot water with twice the weight of the powder, or soak the coffee powder with only a small amount of water.

Steaming can have two positive effects on coffee flavor:

First of all, carbon dioxide has a sour taste, if there is no carbon dioxide from the coffee when steaming, it will make the coffee have a bad sour taste.

Second, carbon dioxide will block the contact between water and coffee. Only when carbon dioxide is discharged can the aromatic substances and oils of coffee be completely dissolved.

As long as there is gas in the coffee powder, it will interfere with the water extraction of coffee substances and will make the extracted coffee have an irritating sour taste.

The next time you make coffee by hand, remember to steam first so that you can grasp the charming flavor of the coffee and avoid the negative flavor and sour taste caused by carbon dioxide.