Why Does Coffee Need to Rest?

The idea that "the fresher the coffee, the better" is quite common. This is one of the fundamental mistakes made especially by newcomers to the coffee world. The main reason for this belief is that those who offer specialty coffee frequently emphasize "freshness." After all, the primary difference between specialty coffee and industrial coffee is the freshness of the coffee. On one side, there are coffees that have sat on supermarket shelves for months, and on the other, coffees roasted specifically for your order…

The truth about coffee freshness is this: as bad as stale coffee is, coffee beans roasted just a few days ago taste just as bad. So, why is that? In this article, we will address this issue.

Degassing

Coffee beans are exposed to high heat during the roasting process. This causes their cellular structure to expand; the sugars and amino acids inside break down, releasing carbon dioxide gas. Once the roasting is complete, some of the released gas remains trapped in the expanded cells.

Coffee beans release approximately 40% of their carbon dioxide within the first 24 hours. After that, the remaining gases continue to be slowly released, depending on the hardness and roast level of the coffee.

What Happens If We Grind and Brew Fresh Coffee?

When water comes into contact with coffee, the gases trapped within the coffee push the water away. This results in an uneven extraction. Bitter and sour flavors emerge in the coffee, while aromas are lost.

When you grind and brew fresh coffee, you might observe different reactions depending on the brewing method. You might see reactions like excessive blooming in filter coffee or excessive crema in espresso. While this might look appealing to you, it creates a negative gas barrier in the cup that overrides the aroma.

What Factors Affect Degassing?

The factors affecting degassing can essentially be discussed under two main headings: roast color and coffee hardness.

Roast

Less gas is released in light roast coffees. However, due to the hard structure imparted by light roasting, gas release occurs slowly, so the degassing period is longer. It is necessary to wait 10 days for filter coffee and 15 days for espresso.

Dark roast coffees, on the other hand, release more gas. Gas release happens faster in these coffees. The main reason for this is that as coffees are roasted, they soften, which facilitates gas release. A waiting period of 7 days for filter coffee and 10 days for espresso is sufficient.

Hardness

Coffees grown at high altitudes are harder. Therefore, their degassing periods are longer. For example, Ethiopian coffees grown at an altitude of 2,000 meters have a longer degassing period compared to Brazilian coffees grown at 1,000 meters.

Can Degassing Be Accelerated?

It is possible to accelerate degassing, or gas release. The finer the coffee is ground, the faster the gas release. Grinding espresso-based coffees minutes before brewing is sufficient to release carbon dioxide gas. For coarser ground filter coffee, hours will be required.

However, grinding coffee and letting it sit for degassing is not a good idea. This is because there is a risk of the coffee becoming stale due to oxidation. On the other hand, if you are forced to, it might be a better option than drinking an underextracted coffee.

If you buy pre-ground coffee, you don't need to wait for degassing. By the time the coffee reaches you, most of the gas will have been released through the one-way valve on the package.

If you buy your coffee as whole beans, you need to pay attention to the roast date. You should wait for a certain period depending on the roast color of the beans and your brewing method.

By taking the degassing period into account when purchasing your coffee, you can elevate your coffee experience to the next level.