Beginner's Guide to Coffee Bean Curing - How to Cure Single-Origin Coffee Beans Without Water and Fertilizer

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FrontStreet Coffee - Introduction to Single-Origin Coffee Bean Degassing

After coffee beans are roasted, they undergo a phenomenon known as degassing. This means that coffee beans expand in volume during roasting, and the expanded space within the beans contains carbon dioxide. Additionally, a series of other chemical changes occur. The most intuitive way to observe these changes is through pour-over brewing. When pour-over brewing, we first inject 1-2 times the amount of water into the coffee grounds. The coffee grounds will begin to expand and form a small hill upon contact with water. This is the process of coffee grounds releasing carbon dioxide, and the purpose of degassing is to release this carbon dioxide.

As time passes, carbon dioxide is gradually released while the coffee's flavor also gradually dissipates. Therefore, when we brew coffee that has been stored for over a month, there may be no small hill formation during the blooming stage.

Why Degassing is Necessary

Freshly roasted coffee is full of vitality, which is reflected in coffee extraction - the beans have abundant gases and expand easily upon contact with water.

At this stage, because the coffee is too active, the crema when making espresso will be rather coarse and dissipate quickly. When extracted using pour-over or other brewing methods, the flavor will be bright but lacking in body, with acidity that is often too sharp. This is when degassing becomes necessary.

Some suggest sealed degassing, while others recommend open-air degassing - meaning freshly roasted beans need appropriate contact with air for a certain period.

The length of degassing time depends more on the roast level and extraction method. For lighter roasts and coffee extracted using brewing equipment, generally 1-3 days of degassing is sufficient. For darker roasts and coffee extracted using espresso machines, 3-5 days of degassing is required.

During the roasting process, as green beans are exposed to increasing heat and time, coffee changes from green to yellowish-brown, eventually reaching the designated roast level. When the roasting rhythm is too fast, the molecular structure in the coffee breaks down more severely, and the roasted coffee beans may have some dryness/smoky flavors. Such coffee beans need to be left for several days.

Some people ask, do all beans need degassing? Of course not! When the roasting rhythm is appropriate and the beans have no roasting defects, degassing is not necessary.

Knowledge Point: Degassing must be done in packaging bags equipped with one-way degassing valves.

In Summary

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