Coffee bag valve: how the degassing valve works
The aroma valve is a one-way valve: it lets the CO₂ that freshly roasted coffee gives off escape from the bag and stops oxygen from getting in. The bag does not puff up and the coffee stays aromatic. It is not a smelling window.
As of: 18.10.2026 · Reviewed by: Editorial team Elke Plastic GmbH · Information provided without guarantee.
Why does coffee need a valve?
Freshly roasted coffee releases carbon dioxide (CO₂) in the days after roasting. If the bag were completely airtight without a valve, it would puff up and could burst. The aroma valve lets gas out only. Oxygen, which weakens the aroma, stays outside.
Bag types with an aroma valve
| Bag type | Material structure (example) | Aroma-tight and light-proof |
|---|---|---|
| Coffee Bags with Aroma Protection Valve | OPP matt 19 / aluminium 7 / PE 110 (Black coffee bag) | yes |
| Side gusset bag with aroma protection valve | Aluminium laminate (side gusset bag with aroma protection valve) | yes |
| Stand-Up Pouches with Valve | PET 12 / aluminium 7 / LDPE 110 (Black stand-up pouch with aroma protection valve) | yes |
Stand-up pouches are also available with a zip closure and tear notch. All bags with a valve are marked as food-safe.
Material structure: why aluminium, PET and PE?
Aroma protection bags are made of several layers. The outer layer (PET or OPP) carries the print, the thin aluminium layer blocks light, oxygen and aroma loss, and the PE inner layer is heat-sealable and suitable for food. Because of the aluminium, such laminates are harder to recycle than pure mono-materials. More on this: Mono-PE instead of aluminium laminate.
What to look for when choosing
- Roasted coffee: bags with a valve, aroma-tight and light-proof.
- Fill quantity: choose a suitable size, see the bag size chart.
- Resealing: stand-up pouches with a zip closure keep the coffee fresh after opening.
- Tea and spices do not need a valve, but they do need aroma protection: see Stand-Up Pouches for Tea and Stand-Up Pouches for Spices.
Frequently asked questions
What is the valve on a coffee bag for?
It lets the CO₂ from freshly roasted coffee escape and keeps oxygen out. This keeps the bag flat and the coffee fresh.
Can you smell coffee through the aroma valve?
The valve is not a smelling window. It is there to equalise pressure. If you press the bag gently, some scent may escape, but that is a side effect.
Does every coffee need a valve?
Freshly roasted coffee gives off CO₂ and benefits from the valve. For coffee that has already degassed, an aroma-tight bag without a valve is enough.
Are bags with an aroma valve food-safe?
The bags in our range are marked as food-safe. You can find the evidence in the data sheet archive.