Re-useable Vacuum Sealer Bags

[chokkidog]

And... your comment on storing beans in the fridge does do your coffee knowledge credibility no favours.

or flavours......:-D

[Vinitasse]

Happy new year all!

Yes, I know you've claimed the eggnog, but the challenge was to cause the valve to off-gas, not demonstrate your flatulent beans. More work to be done I'm afraid...

(BTW, try storing them in the fridge, they'll stay fresh longer...)

As stated before, the strong aroma of coffee in the room following 12 hours of off-gassing was more than enough evidence that the valves were indeed "passing gas".

And... your comment on storing beans in the fridge does do your coffee knowledge credibility no favours. My advice would be to stick with your "professional" science career and to leave us to our professional coffee careers.

[jaybee]

I've already claimed the Eggnog!

Prevaricate as much as you like but the truth will not be bludgeoned, or deferred, to meet your definition of reality.

You can find my mailing address via Google and I prefer the Nog with Grog so don't be shy.

Happy new year all!

Yes, I know you've claimed the eggnog, but the challenge was to cause the valve to off-gas, not demonstrate your flatulent beans. More work to be done I'm afraid...

(BTW, try storing them in the fridge, they'll stay fresh longer...)

[Vinitasse]

Good to see some gray matter being stretched here.

And for Vinitasse to claim the Eggnog, (And thanks for rising to the challenge) he has to demonstrate that the bag of beans, left sealed has to reduce in weight by about 4 grams after a couple of weeks showing that 2.5 litres of CO2 have been off gassed and lost through the valve. What do we all think??

The control needs to be a similar batch of beans sealed in a vacuum food saver bag (without the vacuum!) which we would expect to swell up like a balloon!

BTW, I was referring to off-gassing with regard to the roasting process rather than staleing due to the further introduction of air, but that's my bad for nor being clear.

I've already claimed the Eggnog!

Prevaricate as much as you like but the truth will not be bludgeoned, or deferred, to meet your definition of reality.

You can find my mailing address via Google and I prefer the Nog with Grog so don't be shy.

[jaybee]

Good to see some gray matter being stretched here.

And for Vinitasse to claim the Eggnog, (And thanks for rising to the challenge) he has to demonstrate that the bag of beans, left sealed has to reduce in weight by about 4 grams after a couple of weeks showing that 2.5 litres of CO2 have been off gassed and lost through the valve. What do we all think??

The control needs to be a similar batch of beans sealed in a vacuum food saver bag (without the vacuum!) which we would expect to swell up like a balloon!

BTW, I was referring to off-gassing with regard to the roasting process rather than staleing due to the further introduction of air, but that's my bad for nor being clear.

[chokkidog]

Well, 10L of any gas with a density of 1.97 kg/m3 (at 0ºC) will weigh 19.7 g.
At 25C, the density would be lower, so 10 L of gas would actually weigh approx. 18 g.

To confirm the Wikipedia density approximation:
At 25ºC, one mole of an ideal gas (carbon dioxide is pretty much ideal at room temp) will be approximately 24.5 L in volume at atmospheric pressure (101.3 kPaa). The mass of one mole of carbon dioxide is ~44.01 g.

So 10 L of pure CO2 (@ 25ºC & 1 atm) = 44 × 10/24.47 = 18 g

Of course, there are probably other gases being evolved from the beans too.

Sheldon enough for you?



Because they don't know about the Kintetic Theory of Gases (and by extension, Effusion)?

Thanks MrJack, :-D

And 'they' obviously don't but Thundergod and Vinitasse obviously do! :-D

Cheers.

[MrJack]

If carbon has a molecular weight of 44.01 and the gas has a density of 1.977 kg/m3 @ 1 atm and 0°C ( Wikipedia)
perhaps one of the Sheldon types ( I'm all for Penny) can tell us how much 10 litres weigh @ 1 atm and 25°C?( Just out of interest as carbon footprints are measured in tonnes of CO2)

Well, 10L of any gas with a density of 1.97 kg/m3 (at 0ºC) will weigh 19.7 g.
At 25C, the density would be lower, so 10 L of gas would actually weigh approx. 18 g.

To confirm the Wikipedia density approximation:
At 25ºC, one mole of an ideal gas (carbon dioxide is pretty much ideal at room temp) will be approximately 24.5 L in volume at atmospheric pressure (101.3 kPaa). The mass of one mole of carbon dioxide is ~44.01 g.

So 10 L of pure CO2 (@ 25ºC & 1 atm) = 44 × 10/24.47 = 18 g

Of course, there are probably other gases being evolved from the beans too.

Sheldon enough for you?

Why do people say that because the bag is puffed up the valve isn't working? Have any of you packed the same roast in a valved and a valveless bag and
compared the difference? Perhaps the Sheldon types could be a lot more scientific? Although bags don't explode, seams of unvalved bags have been known to give.

Because they don't know about the Kintetic Theory of Gases (and by extension, Effusion)?

[Yelta]

It's easy to avoid outgassing. You just sell and pack beans which are totally, utterly stale.

Seems most resellers of roasted beans have already mastered this technique.

[TC]

Thank goodness for a little recent sanity.

Just goes to support the fact that in amongst the occasional gems, you can find all sorts of well meaning but ultimately ill-informed opinions on the internerd.

It's easy to avoid outgassing. You just sell and pack beans which are totally, utterly stale.

[Vinitasse]

There has never been any gas in the bags after packaging shop bought coffee, and home roasted only off-gasses a small amount for a very short time anyway and after a day the beans are inert.

I would just like to add that if your coffee really is that inert (read dead) so soon after being roasted it is time to switch the roasters you buy from and also time to relearn your home roasting techniques as you certainly are not getting the best out of your beans.

[Vinitasse]

Nothing wrong with egg nog!

Ok, Vinitasse, I challenge you to prove me wrong. I say that 250g of freshly roasted green will not cause an appropriately sized valved bag to off-gas. Prove me wrong by EASTER, and I'll send you with love and admiration, a bottle of Eggnog. Fail, and you admit to being full of, er, CO2 yourself

I'm a professional scientist, so I don't mind being proven wrong...

I accept your challenge.

Last night I was so annoyed by the obtuse assertions flying in the face of reality, as known by actual commercial roasters, that I decided to provide photographic evidence to prove you wrong. Knowing that scientists, even those from Queensland , respect observable evidence I respectfully submit the following:





The first picture shows a 250g bag of coffee that was roasted on the 18th of December. Last night, after reading all the silliness above, I used a vacuum to remove the air/CO2 from within the bag and let it rest overnight.

The second pic shows the same bag 12 hours later and it has very obviously puffed itself up again with the CO2 still actively being degassed 5 days post roast. The volume of CO2 expelled is far greater than the "trace" elements described by Jaybee, and far beyond the immediately post-roast time frame Jaybee was spouting off about.

As for the volume of CO2 given off being sufficient to vent through the valve, I wish I were able to invent a "smellometer" so that you could see just how strong the smell of coffee was in the room the bag of coffee was left in. The dining room was absolutely filled with the sweet, rich aroma of freshly roasted coffee and the only way that smell could have left the sealed bag was via the one-way valve.

Before you suggest that the smell was released when I vacuumed the bag last night, the fact is that the vacuum is in my coffee roastery and the bag was brought into the house for photography after the fact.

In any event, please PM me for my mailing address so that you can send me the promised egg nog. And please be fast about it as I would much rather have it for Christmas than for Easter.

[Yelta]

I've only had one bag so far with a faulty valve.
When I went to retrieve the beans from the cupboard a week after roasting, the bag had puffed up enough to pop the ziplock and the bag was as taught as could be.

The beans did not taste one week old. I surmised they'd not aged normally because the gas had nowhere to go.

Have wondered about this as a longer term storage option for roasted beans, eliminate air and replace with CO2, wonder if anyone has done any work in this area?

[Thundergod]

I'll repeat here an experience I've posted before.

I've only had one bag so far with a faulty valve.
When I went to retrieve the beans from the cupboard a week after roasting, the bag had puffed up enough to pop the ziplock and the bag was as taught as could be.

The beans did not taste one week old. I surmised they'd not aged normally because the gas had nowhere to go.

[chokkidog]

Crikey! All the lay experts are coming outta the wood work! Must be the silly season. ;-D

A kilo of beans will degas approximately 10 litres of CO2 ( Illy, Espresso Coffee and B.A. Blakistone, Principles and Applications of Modified Atmosphere Packaging of Foods)
over a period of several weeks with about 40% of the volume degassing in the first 24-48 hrs (dependent on ambient temp).

If carbon has a molecular weight of 44.01 and the gas has a density of 1.977 kg/m3 @ 1 atm and 0°C ( Wikipedia)
perhaps one of the Sheldon types ( I'm all for Penny) can tell us how much 10 litres weigh @ 1 atm and 25°C?( Just out of interest as carbon footprints are measured in tonnes of CO2)

Why do people say that because the bag is puffed up the valve isn't working? Have any of you packed the same roast in a valved and a valveless bag and
compared the difference? Perhaps the Sheldon types could be a lot more scientific? Although bags don't explode, seams of unvalved bags have been known to give.

After being around fermenting grapes for quite a few years I am very familiar with the sensation of being in a CO2 rich environment.
The same environmental sensation can be had (at a much reduced level) if you chuck 20 kgs of roasted coffee, stored in valved bags, in your car and drive around for a while.
CO2 is clearly emitting from the coffee and is easily distinguished from methane. :-D


I am certainly not against vacuum packing coffee either green or roasted but I am fond of accurate information.

I also meant to add that if the emission of CO2 relates to the degradation and oxidisation of roasted beans i.e. the process of going stale,
then it stands to reason that for as long as the beans are going stale they will continue to emit CO2. It's just plain logic.

Coffee beans wouldn't become 'inert" ( if they ever do ) until this process has run it's course.

Said my bit, over and out.

[Journeyman]

I had a bag of beans from my local roaster - he said 4 days old when I got them. About a week later when the subject came up I went and checked them (they're kept in behind my coffee jars) and the bag was bulging with gas - wasn't enough obviously to trigger the valve and when I squashed it down to the beans, the bag did not get any more inflation.

I take that to mean the beans will out-gas anything up to a week after roast but after 10 days it's done. Both figures could be adjusted downwards as i didn't check them except going into the cupboard (day 4) and when I squashed them (day 10 or 11)