What is the reason for coffee steaming for too long? what is the reason for hand steaming without swelling?

In normal brewing coffee, after pouring water into the dried coffee powder layer during the steaming stage, the coffee powder will absorb water and expand into the shape of "hamburger". When the coffee powder layer does not expand during the steaming phase, it indicates that there is a problem, and we should find out where the problem lies and solve it.

- Coffee beans are stale-The easiest reason to think of is that the rest of the beans are drained and no longer fresh. The main reason why coffee powder expands into a "hamburger" shape is that after roasting, there is a lot of carbon dioxide gas in the coffee beans. When the coffee powder absorbs water, it will expel gas, and at the same time, the gas will also "prop up" the entire coffee powder layer and expand into a bulge. Of course, with the passage of time, the gas in the roasted coffee beans will be slowly discharged. Generally, the coffee beans will exhaust the gas in about 45 days, and the coffee beans with almost all the gas will not expand when they are steamed, and the flavor will also be weakened. Time is not absolutely accurate, this is related to the storage environment of coffee beans, coffee beans stored in a sealed environment, reduce contact with oxygen, can make coffee exhaust more slowly. If the bag is often opened, or directly exposed to the atmosphere, coffee beans will be exhausted very quickly. The following is an experiment on the front street. The first picture shows coffee beans stored in coffee bags for 2 months and then brewed (unopened). During brewing, the coffee powder layer still expands and bulges, but it is not as obvious as in the early stage. The second image shows coffee beans roasted not in bags, but exposed to the atmosphere, brewed after 20 days, without expansion of the coffee powder layer. Therefore, proper storage of coffee beans is an important way to maintain a longer taste period. Qianjie suggested that the original coffee packaging bag can be stored. The coffee packaging bag has a one-way exhaust valve, which can adjust the internal and external air pressure, and a blockade strip to ensure the tightness of the storage environment. If you open the bag and take the beans every day, and then seal the lock, you can keep them for about 30 days. In terms of daily consumption, you can definitely drink them before the gas is exhausted. Grind Coarse-This problem usually occurs when a new bean is replaced. If you replace another coffee bean with a different style, if you use the previously fixed grind scale, it will occur because the grind is too coarse and the steam does not expand.

Just as Qianjie often emphasizes when sharing knowledge of grinding, coffee beans do not all grind to the same thickness due to factors such as variety, altitude, treatment, roasting, etc. Therefore, it is very important to choose the correct grinding degree. The grinding calibration of Qianjie coffee is calibrated by using a sieve with an aperture of 0.85mm. The fineness of hand-brewed coffee is selected at a grinding rate of 80% through the sieve. - Very shallow roast-very shallow roast because of the early, hard beans, less gas, so in the steam time, and will not appear obvious expansion, its performance is not fresh coffee beans, the subsequent water injection appears thin gold foam. But that doesn't affect its flavor. Some lightly roasted coffee beans also have a similar phenomenon. When steaming, the coffee bulge is not obvious, and the shallow bulge is also a normal phenomenon.