Degassing is the process where freshly roasted coffee beans release carbon dioxide (CO₂), which is formed during roasting. This gas can negatively affect brewing if it is too high – causing uneven extraction, acidity, or unstable crema in espresso. At the same time, a small amount of CO₂ is a sign of freshness, contributing to aroma and bloom.
During roasting, chemical reactions such as the Maillard reaction, caramelization, and pyrolysis occur, producing CO₂ and over 800 aroma compounds. Much of the gas is released already during roasting (especially at first and second crack), but some remains trapped inside the bean's porous structure.
After roasting, degassing begins immediately:
Factors affecting the rate:
Roast level
Light roasting produces less CO₂, but the beans are denser, so the gas escapes more slowly (up to 2-3 weeks). Dark roasting produces more CO₂, but the beans are more porous, so degassing happens faster (3-5 days).
Temperature
Higher storage temperature accelerates the process.
Grinding
Fine grinding releases up to 50-60% more CO₂ quickly.
Bean type
High-grown or natural-processed beans often degas more slowly.
Degassing is more critical for espresso than for filter methods because espresso involves high pressure and a short extraction time – excess CO₂ can cause channeling, unstable crema, or sour taste.
Recommended resting times (from roasting date):
Filter coffee (pour-over, drip, French press)
3-7 days. You can often brew already after 2-4 days, as the bloom phase naturally releases CO₂. For light roasts: It is advisable to wait 5-10 days for maximum clarity and fruitiness.
Espresso
7-14 days (often peaks at 8-12 days). For light roasts, it can take up to 2-3 weeks. Dark roasts: 3-7 days is often sufficient.
These times are guidelines – test yourself, as it depends on your roasting profile and beans.
You don't need advanced equipment – here are easy ways to assess if your coffee is ready:
The Bloom Test (for filter)
Pour hot water over freshly ground coffee (bloom phase). Fresh coffee bubbles vigorously (large bloom) due to CO₂. If the bloom is weak or absent, the coffee is fully degassed (or too old). Ideally: A moderate, even bloom.
The Crema Test (for espresso)
Pull a shot. For fresh coffee: Thick, unstable crema that bubbles and disappears quickly. Optimally degassed: Stable, golden crema that lasts long.
The Bag Test
Place beans in a sealed ziplock bag (press out the air). If the bag puffs up overnight, a lot of CO₂ is still being released – wait longer.
Taste Test
Brew small portions daily from the same batch. Note when the flavor peaks (most balance, sweetness, and complexity).
With home roasting, you have full control – log your roasts and test resting times to find your perfect profile. Freshly roasted coffee is fantastic, but a little patience often yields the best result in the cup!
Contact us via chat or kontakt@homeroast.dk for advice and questions. Take the leap and experience the difference yourself! ☕
