Quick answerDegassing is the release of carbon dioxide (CO2) from coffee beans after roasting. Most gas escapes in the first few days. Letting beans rest about 3-7 days before brewing, longer for espresso, gives more even extraction and sweeter flavor. The bubbling "bloom" you see when pouring water is degassing in action.
Why it happens
Roasting creates CO2 inside the bean. It slowly escapes over days and weeks, which is why coffee bags have one-way valves.
Why it matters
- Too much CO2 pushes water away from grounds, causing uneven extraction.
- Very fresh espresso can be gassy and sour.
- Too little (very old coffee) means flat taste.
How to work with it
Bloom your coffee: pour a little water first and wait 30-45 seconds before brewing the rest.
Frequently asked questions
Why does my coffee bag have a valve?
It lets CO2 out without letting oxygen in.
No bloom means stale?
Usually, yes: little bloom suggests older coffee.
How long to rest for espresso?
About 7-14 days after roasting.
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