I buy 2-3 bags of fresh roasted beans and after a few days the bags balloon out. Should I squeeze the gases out or let the gases seep out naturally?

  • Only vaguely related, this actually proves that you are getting fresh coffee. Feb 26, 2015 at 17:09

1 Answer 1


It doesn't actually matter!

The valve on the bag is there to let gas out without letting gas in. The reason for this is that freshly roasted beans will continue to give off a bit of CO2 for a little while. Coffee that's packaged immediately after roasting will give off a bit in the bag, hence the need for a valve.

Oxygen causes coffee to go off, which is why we keep our coffee in airtight containers to preserve it as long as possible. It's why the valve on the bag is designed to prevent air from the outside getting in.

The CO2 that's accumulating in the bags is essentially inert, and won't cause the coffee beans to go off. It makes no difference whether you squeeze it out or not!

  • 1
    Agreed, and also... still don't squeeze! I don't fully trust the "one-way-ness" of one-way valves in cheap, one-time-use packaging. In fact, I put the whole thing (original packaging and all, whether opened or not) nested in an additional bag (like a zip-top plastic bag with extra air exhausted) to further minimise the gas exchange.
    – hoc_age
    Feb 26, 2015 at 11:52
  • 4
    @hoc_age Yeah. To be honest, the positive pressure in an inflated bag is probably a good way to make sure no extra oxygen is getting in!
    – fredley
    Feb 26, 2015 at 11:53
  • 1
    Indeed. Sometimes the bags are flushed with more-inert gas (e.g., nitrogen, CO2) to evacuate the less-inert stuff in regular air. Anything that's in there already is better than anything that might seep in!
    – hoc_age
    Feb 26, 2015 at 11:56
  • 2
    Got email from the roaster and they said essentially the same thing. If the coffee is being consumed within 21 days it really has no effect one way or the other.
    – Francisco
    Feb 26, 2015 at 22:07

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