Coffee preservation - Degassing

In the lab

Coffee preservation - Degassing

Jérémie Vergne | 2019-03-12

The new year is upon us along with its good resolutions, one of which concerns a series of articles about preserving coffee, which is not only a huge subject, but is also one of the most commonly asked questions by our customers.

Degassing is a necessary step to improve coffee quality!

 Today I would like to speak to you about degassing as well as the main factor responsible for the future fragility of a roasted bean.... yes, you've guessed it... :


Coffee roasting is the moment when a green bean without flavor turns into a roasted bean with great aromas.

Chemical reactions

We know that through its process, roasting creates a range of complex chemical reactions and also provokes physical changesion the bean, which increases its mass and makes it more porous, leading to a higher rate of diffusion of the volatile aromatic components. At the same time, the Maillard reaction produces components which contribute to the oxidation of the oils (fats) after roasting. In short, through its action, roasting creates unique aromatic profiles but also weakens the coffee bean by making it more porous to exterior elements as well as provoking an acceleration in its aging over time. However, via its various chemical reactions and particularly through the Strecker degradation, roasting also produces an accumulation of CO2 inside the bean which means the bean needs to be rested after roasting.

Roasting with Cropster software during a coffee training

Reactions after roasting

Whilst we generally mean at least 48 hours rest after roasting, today we know that it is much more complicated than that. The final temperature and the total roasting time have a major influence on the optimal degassing time, without even mentioning the future extraction of coffee, specifically for espresso. Even if it is possible to extract a nicely balanced espresso with a fresh coffee, it is the consistency of extractions over time which will prove problematic. This is due to the over-presence of CO2 in the bean. Studies have shown that around 40% of CO2 is released in the first 24 hours but then degassing slows down somewhat depending on roasting parameters. A long or darker roast (or both combined) accelerate the process of degassing roasted coffee, but also accelerate its aging through a increased diffusion of volatile aromatic components. In plain terms, the greater the physical changes on your bean (weight loss, increase in volume, final coloring...) and the more micro-cracks you create (or enlarge to be precise!) in your bean – which will allow CO2 to be released - the more the volatile aromas and then the oils in contact with the air will degrade and be responsible for the creation of a rancid taste.

Roasting coffee increases bean size and creates microcracks that allow CO2 to escape.

Improve your degassing

Let's not forget that, even if we agree on the resting time necessary after roasting, time is clearly an enemy of roasted coffee! Today we talk about a degassing time of between 24h and 12 days depending on the aforementioned elements. For optimum degassing, you need a dry environment at between 20 and 25°C, in clean closed dampers reserved exclusively for roasted coffee (not air-tight, as we need the gas to be released). If these conditions are difficult to meet, you also have the option – and we see this more and more often these days – to pack your coffee directly into valved bags, which I may remind you allow gas to be released but stop air entering to avoid oxidation.

Coffee container to keep roasted coffees only.


To conclude, as you have no doubt noticed, it is very difficult to have just one degassing rule for all your coffees as your roasting process and the nature of your beans will provide fundamental differences in terms of the resting time necessary; the only way to fully master these times is to regularly taste your coffees compared to your roasting profiles in order to understand how they change to be able to fully optimize the gustatory consistency of your coffee. Next time I will talk to you specifically about the enemies of roasted coffee and sound preservation rules for the end consumer.

Jérémie for Belco Team

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