Hand-brewed coffee steaming techniques: How to make coffee bulge? What does steaming coffee mean? Why should I steam coffee before brewing?

"Boss, why can your powder bed expand so big when you steam? How did you do it? "Looking at the powder layer in the filter cup that expanded due to steaming during cooking on the front street, many guests and friends asked this question. The implication is that the expansion coefficient of the powder layer he washed out is not so large. (See the following figure)

For Xiaobai, who has just begun, this is indeed a question worth exploring. Because even if the same parameters are used, the powder bed is always flat when I rush it, and it looks like it lacks some "vitality." In fact, making the powder bed expand into a huge "burger" is not difficult, or even very simple. Because we only need to understand why the powder bed can bulge, we can know how to expand into a huge "burger"~

Why does the powder bed expand? The phenomenon of bulging powder beds occurs during the steaming process. I believe the purpose of steaming is very clear to everyone, that is: to expel carbon dioxide from the body of coffee beans and improve the extraction efficiency of subsequent injection of hot water! The carbon dioxide discharged at this time is the main factor leading to the bulging phenomenon of the powder bed.

When coffee powder comes into contact with hot water, carbon dioxide in the body will be released first. Since a large amount of hot water does not penetrate quickly after being soaked in coffee powder, the carbon dioxide emitted at this time will combine with the water to form bubbles and surge upward. However, because the surface tension between water molecules and the capillary force between coffee powder particles jointly build a tough "prison", bubbles have nowhere to be released and can only continue to accumulate inside the powder layer. Then, because carbon dioxide is not released in one breath but is continuously released outward, we can see that the huge powder bed is actually gradually filled up.

To sum up, we can know that the main reason why the coffee powder layer bulges when steaming is caused by the accumulation of blisters formed by carbon dioxide (but this is not the only reason for bulges is also because the coffee powder itself absorbs water and expands, but this reason is secondary)! Therefore, if we want to steam a huge "burger", we need to make the coffee powder contain enough carbon dioxide, and at the same time, we must ensure that the parameters during extraction can "stimulate" the carbon dioxide!

How to steam a huge "burger"? There are two main factors that determine the carbon dioxide content of coffee beans: the roastness and freshness of the beans. Coffee beans produce carbon dioxide due to high temperatures when roasted. The deeper the coffee beans are roasted, the more carbon dioxide content will be generated. So if we want to steam a huge "burger", then deep-roasted coffee beans are definitely the best "bean" choice. This is also the reason why there is a huge difference in the degree of steaming between different roasted coffee beans (including the expansion of the beans themselves).

But in many cases, even if we use deep-baked beans to cook, we can still steam a huge "burger" very slowly. This is because the time that carbon dioxide stays in coffee beans is limited, which is the second factor mentioned in Qianjie earlier-the freshness of coffee beans. After the coffee beans are roasted, the gas in the body will continuously escape out due to changes in pressure, so the carbon dioxide content of the coffee beans will gradually decrease over time. In other words, when the coffee beans are fresher, the more carbon dioxide content it contains and the bigger the bulge will be, and vice versa. If we want to steam into a huge bun, freshly roasted fresh coffee beans are definitely the best choice.

However, freshly baked coffee will have a certain dryness. At the same time, due to the excessive carbon dioxide content, the obstacle to extraction is very high. It is easy to make a cup of coffee with heavy flavor and insufficient extraction. Therefore, Qianjie does not recommend choosing too fresh coffee beans for making in order to make them. It is completely unnecessary. What's interesting is that when the coffee beans you use are not as fresh, although the powder bed will expand at the beginning of steaming, it will soon sag due to insufficient carbon dioxide "supply".

In addition to the choice of coffee beans, after inquiry, Qianjie found that the reason why many friends couldn't make the "burger" was that the parameters were not used correctly. Factors such as too rough grinding and too low water temperature cannot make a big enough "burger"! Because coffee powders are not "stimulated" enough, they cannot release large amounts of carbon dioxide in a short period of time. No matter how fresh the coffee beans are and how deeply they are roasted, if the carbon dioxide is not emitted in a timely manner, the powder bed cannot form a large enough "burger" during steaming. This is roughly the case! Isn't it easy? By using the right coffee beans and the right parameters, we can get a big enough "burger" during the steaming stage. In turn, this is also a sharing of coffee bean information through the bulging state of the powder bed. The freshness and roasting degree of coffee beans can be read from the state of the powder bed during steaming according to the above-mentioned contents of Qianjie. Congratulations! One step closer to the great coffee god ~

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