Noonievut Senior Member Joined: 9 Sep 2006 Posts: 458 Location: Toronto. Canada Expertise: I love coffee
Espresso: Brasilia Club Grinder: Rocky DL Vac Pot: Other - Aeropress Roaster: Behmor
Posted Tue May 13, 2008, 4:43am Subject: De-gassing question
I roasted beans on Saturday afternoon in my freshroast + 8. After they cooled to room temperature, I put them in mason jars and loosely put the lids on. I left the lids that way for about 18 hours, I then sealed the jars (there was about 1 centimeter of head space in the jars). On Monday I opened a jar and there was very little 'pop' (that sound when the air escapes the jar). Beans tasted fine though. I used about 1/2 the beans then I resealed the jar (now about 2 inches of headspace). Today when I opened the jar there was a much more noticeable 'pop'. Why the difference in the 'pop'? Is it because of headspace (more headspace = more pop), or because of the extra day of the beans sealed in the jars?
Posted Tue May 13, 2008, 5:02am Subject: Re: De-gassing question
It might be because of more headspace. Gases are very compressible, while coffee beans are not :-) so extra room means more gas can build up before the "backpressure" slows the degassing down.
Having said that, I confess that I don't fully understand the degassing process either. I will get pressure buildup for at least the first 3 or 4 days in a truly airtight container. It also seems that keeping them under pressure just lengthens the degassing process, but I haven't done any real scientific investigation to determine all the variables and how they affect the final result. Possible variables: smaller volume container, keeping under pressure, allowing slow release (as in degassing valves), taste results under various conditions, etc.
The main problem I have because of all this is bloom during brewing. It gets in the way of drip, vac pot, Aeropress, just about any brewing type at all. If I could get the gas out faster without exposing to oxygen as well, I'd be happy about it.
Posted Tue May 13, 2008, 6:23am Subject: Re: De-gassing question
I'd have to say that the mason jar method would retard the outgassing longer than one would wish. You want to begin enjoying the coffee as soon after roast as possible.
I began with the fear that exposure to air just hastens the staling process, but I've found that not to be the case.
What I have success with is the one-way valve bags. I use them about 12-18 hours after leaving the roasted beans in an open bowl. Then I've noticed in the bags they sort of cure to a sweet spot in a couple of days.
But I do notice that they deteriorate quickly after that. That's the point where I move them to vaccuum storage.
Interestingly, I usually don't get to the vaccuum stage point because I'm usually out and roasting another batch by then.
DavecUK Senior Member Joined: 21 Sep 2005 Posts: 203 Location: UK Expertise: I love coffee
Espresso: Izzo Alex Duetto (serial... Grinder: Mazzer Mini E Roaster: Toper 1kg (sold) Gene Cafe
Posted Tue May 13, 2008, 8:16am Subject: Re: De-gassing question
Noonievut Said:
I roasted beans on Saturday afternoon in my freshroast + 8. After they cooled to room temperature, I put them in mason jars and loosely put the lids on. I left the lids that way for about 18 hours, I then sealed the jars (there was about 1 centimeter of head space in the jars). On Monday I opened a jar and there was very little 'pop' (that sound when the air escapes the jar). Beans tasted fine though. I used about 1/2 the beans then I resealed the jar (now about 2 inches of head-space). Today when I opened the jar there was a much more noticeable 'pop'. Why the difference in the 'pop'? Is it because of headspace (more headspace = more pop), or because of the extra day of the beans sealed in the jars?
You have probably experienced something similar to my own findings when experimenting with vacu seal packaging. This is not keeping the beans in a vacuum per se, but using a flexible bag from which all free air has been removed as far as possible (via a one way valve). I firmly believe the "gas" is not stored within the beans as a gas, but produced as part of oxidising and possibly non oxidising reactions that take place after roasting. I have many times (in fact almost all the time, managed to vacuum fresh coffee into a "brick" straight after roasting (I mean within 6-7 minutes of the roast ending), some coffees will need a further vacuum a few days later (as some CO2 will be produced). The Coffees will then sit in brick form, no more gas produced for days or even weeks, until they are opened and then resealed and re-vacuumed.....then they start producing CO2 again. I am not the only one to notice this behaviour, as more of our forum members have bought the Vacu seal system (which is actually for food not for coffee), they have also noticed the same thing. You can read all about what we have tried on the link below.
It may be different to most of the information on the internet to do with degassing, but the experimental results don't support current accepted theories on degassing of coffee.
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