baldheadracing wrote:There is more to it than the size of the molecule. For example, water is smaller than oxygen, but easier to contain. For oxygen and nitrogen in particular, the hand-waving answer is they are not organic (Carbon-based) gases. As such, they have a harder time "getting through" the (Carbon-based) materials used in (some layers of) bags than an organic compound.

Vacuum bags are made up of layers of multiple materials. Here's a summary of the three main types: https://packagingblog.org/2019/10/11/ca ... l-any-bag/

As an aside, FoodSaver claims odor resistance for their 5-layer bags/rolls. I personally use generic vac-seal rolls, but organize the vac-sealed bags in Ziploc(brand) freezer bags. (Those particular bags are also supposed to offer odor resistance.) Anecdotally, when my freezer failed a couple years ago, no odours were transferred - but everything else in the freezer was also in Ziploc freezer bags.

A bit about the chemistry of permeability: https://polymerdatabase.com/polymer%20p ... ility.html

Thanks for the interesting article. When I switched from Foodsaver brand bags to generic ones at least 5 years ago I read something about them and recalled the term barrier. I have experienced no difference between the Amazon generic bags and the foodsaver brand. I try to get the thickest ones available and they work fine.

I still don't understand a chemical mechanism for an organic large molecule to get through where an uncharged neutral tiny gas is sealed out. It's been 50 years since organic chem and physical chemistry.

Man, you'd think that deep freezers would come with a small battery powered alarm that beeps if temperature rises above a certain value.

I have a friend who was out of town and their house lost power for a few days in the summer from a bad storm... and it was an old deep freeze and the power surge fried it, so it never came back on. He had like half a cow in his deep freeze and it all went bad by the time he got back. It was >$1000 worth of meat. Turns out he was able to include it on a home owner's insurance claim and got reimbursed for it (he had some other damage from a tree falling on his garage as well).

Pacotacomeat wrote:Man, you'd think that deep freezers would come with a small battery powered alarm that beeps if temperature rises above a certain value.

Most do have an alarm but it's only useful if there's an issue not involving a power failure. Of course if you are home you will know that the powers off, if not there's not much you can do about it. The other issue with built in alarms is that freezers are usually located in basements, garages or out of the way rooms. Most folks won't hear an alarm beeping unless they go to get something out of the freezer. Our remote monitor has save us several times when the door on one of our older freezers didn't stay fully closed. We now keep that door locked.

GC7 wrote:... I still don't understand a chemical mechanism for an organic large molecule to get through where an uncharged neutral tiny gas is sealed out. It's been 50 years since organic chem and physical chemistry.

It's 40 years for me, and, to be honest, I didn't understand physical chemistry then, so I definitely can't explain it properly today .

Best I can say is Carbon compounds in bags (polymers, long chains of Carbon molecules with lots of H, N, O, etc. attached to them) attract the usual gases (H2, N2, O2) like two magnets that are already stuck to something other object weakly attract. To stretch the analogy, the H2, N2, O2 are looking for empty places where they can attach to the Carbon (and vice versa) so they stick to, or are repelled by, the polymers. On the other hand, if there is a Carbon already in the gas, for example CO2, then the gas can pass without the magnet/sticky analogy happening.

Carbon-containing or not, the gases also have to deal with the shape of the bag's polymer molecules (a chain, a ring, etc.) and how those polymers are arranged (crystals, semi-crystals, etc.). Thus, bag polymers can be chosen/made to better handle particular compounds.

Sorry, I know that's not a great explanation.

glf wrote:Something like this then might give greater piece of mind? https://vacuumsealersunlimited.com/shop ... ling-bags/

I didn't even know that mylar bags/rolls for food sealers were even made. Over 3x more expensive than their regular rolls, but I think that I'll try them out - and leave my "regular" bags for sous-vide. Thanks!

baldheadracing wrote:Sorry, I know that's not a great explanation.
I didn't even know that mylar bags/rolls for food sealers were even made. Over 3x more expensive than their regular rolls, but I think that I'll try them out - and leave my "regular" bags for sous-vide. Thanks!

- Thanks for that. I wasted some time and couldn't find anything about how these bags work but I did find this interesting fact.

Can dogs smell through FoodSaver bags?
Although man's best friend tends to have a pretty incredible ability to sniff things out, dogs cannot smell though airtight, vacuum sealed containers. Pups can smell under things, around things, into things and even things underwater. However, airtight containers are vacuum sealed, keeping any air from escaping.

My guess from this is that volatile organics can't get through the bags. If a dog can't smell it then it just isn't there at any appreciable level.

I'm going to try those foil bags as well.