On CFUK I started discussions on it, or tried to for 5+ years (from when I started doing it), then gave up. I also tried to start a discussion on biodegradable/compostable and how to tell if it was harming your coffee, as all bags are not created equal.
On both occasions, a small group of people killed the discussion each time….so I gave up.
There are 2 reasons roasters don’t do it, partly related:
- The bags can explode if too small, kept too warm, or too old. Or any combination
- Coffee must be packed ASAP after roasting, I roast and pack, so the coffee is still warm when it’s bagged (if this isn’t done the coffee oxidises more before packing and adsorbs more O2 into the structure, causing it to produce more CO2 within the bag.
The bag below contains coffee roasted on 4th April, you can see the coffee area on the left and the CO2 area on the right. The coffee might produce a little more gas, but most of the residual oxygen in the bag is used up. Unless the temperature rises quite high the reaction has a reluctance to “go”. I do squeeze as much air as I can out of the bag before sealing.
Roasted coffee does not contain a load of CO2 in little “gas bottles” waiting to seep out and expand, it produces it as a result of exposure to O2 some of which I believe is adsorbed into the structure…hence packing it fast.
In a non valve bag, freshness is maintained far longer…I can open coffee after 3 months, and it pours and tastes like it was roasted a few days ago. The only is it seems to stale a little quicker once opened if the coffee is 2 or 3 months old.
P.S. There was an SCAA paper that said how much weight of “trapped” CO2 outgasses from coffee. When converting the weight of CO2 supposedly trapped to volume, it meant my bags should have burst at least 2 times over.
In the first 24 hours after roasting, coffee releases around 40% of all absorbed CO2 because of the pressure in the beans. After that, the process slows down, although the time it takes largely depends on whether the coffee is whole bean or ground.
This quote from the internet is completer rubbish, because I squeeze as much air out of the bag before packing, usually the remaining O2 on the bag contracts, making it look like it’s vacuum sealed. In the first 24 hours it still looks vacuum sealed, that appearance softens after 24 hours…certainly 40% of the total CO2 production is not done in that time…not even close..
