To be honest, do you know what the degassing and oxidation of coffee beans are?

People often say that "the fresher the coffee, the better". But this is not true. After the raw coffee beans are roasted, two opposing forces will immediately wrestle, which determines when the peak state of the coffee will occur. These two forces are exhaust and oxidation.

The reason why coffee beans are not better the fresher they are is that freshly roasted coffee beans have too much carbon dioxide, and the various flavors cannot be fully released, so they taste tasteless. It takes some time to "exhale", and this process is called bean curing, which takes about 24-48 hours.

The period from when the beans are grown and consumed until the obvious defective flavor appears is called the best flavor period. For example, for medium roasted beans, the best flavor period is about 30 days. For light roasted beans, it is about 40-50 days, while the best flavor period for dark roasted beans is shorter, usually within 30 days.

Of course, this optimal flavor period is based on certain storage conditions, which are the three key factors for preserving cooked beans: sealing, avoiding light, and preventing moisture.

In addition to these three key factors, the packaging of coffee beans is also very important. Most coffee beans are packaged in one-way exhaust valve bags lined with aluminum foil. The aluminum foil can block light and air, while the one-way exhaust valve is used to discharge excess carbon dioxide.

But once you get the coffee beans, the bag is useless. Because once the beans are grown, there is no need to let them vent. When you press the exhaust valve and smell the coffee aroma, in addition to the carbon dioxide, many aromas are also exhausted and lost.

Because the bag with a one-way exhaust valve will emit too much aroma, it is not suitable for long-term use even if it can be sealed repeatedly. Therefore, changing the container seal is a must for preserving coffee beans. Sealed cans are the first choice. Try to choose odorless and opaque sealed cans. In addition, sealed cans are not necessarily sealed. Most sealed cans will leak a little, which is normal. There is also air in the can, and the coffee beans will continue to oxidize at a slower rate. Therefore, sealing prolongs the fresh life.

exhaust

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Exhaust means that freshly roasted coffee beans release the carbon dioxide stored in them. In the first week after coffee is roasted, the carbon dioxide will be discharged at a particularly intense and rapid rate.

So why is CO2 emissions such a headache for baristas?

In the first week after roasting, coffee beans are emitting carbon dioxide very vigorously, and the state of coffee beans will be like a beast that is unwilling to be tamed. It is very unstable, which can easily lead to uneven extraction, difficult to predict the brewing process, and loss of consistency in the product. Any barista who has tried to use too fresh coffee beans to produce espresso should have faced this dilemma.

No matter how hard you try to control the grind size, water-to-powder ratio, water temperature, and time, the state of the extracted coffee will still be extremely unstable. It will be different from today to tomorrow; from morning to afternoon; even two consecutive cups can be different. It is basically impossible to formulate an extraction plan under such circumstances.

The second reason why I don't like carbon dioxide is the impact it has on the flavor of coffee. When brewing coffee that is too fresh, some of the characteristics of the beans, such as the unique flavor of the origin and variety, may be weakened or masked by carbon dioxide. You may not taste a very clear flavor when you drink it. The sweetness may become incomplete, and the whole sensory experience may feel a little unpleasant and uncomfortable.

Therefore, a few days after roasting, coffee is not actually at its peak freshness or flavor, which is why you need to let the beans rest and exhaust for a while before brewing.

Oxidation

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What is oxidation? It's the force that causes metal to rust, food to spoil when exposed to air, and coffee to lose its flavor. In short, oxidation is a bad thing.