Upon reading the question If I vacuum seal a food product like beef stew then boil it in the bag, would it keep un-refrigerated? and the answer provided https://cooking.stackexchange.com/a/69423/6279 I agree that 'normally' it would not result in making something shelf stable. But My question is COULD you (by putting the vacuum sealed bag into a pressure cooker) achieve the results of canning in said bag? I found some speculation on this question here but I am unsure of the conclusion...(given the sources)
(disclaimer: I've only heard of people doing this, not done it myself.)
Yes, it can be done. You're looking for retort pouch canning. Various places will sell you the bags, and you can vacuum seal them with a chamber vac, though you may need an upgraded heat bar. Then you can process them in a pressure canner (or preferably autoclave).
I'd definitely follow the normal reheating recommendations (the boil it 10 minutes bit) before eating. I don't think USDA has home canning guides for retort pouches.
The safety of pressure canning depends on reaching a sufficiently high temperature (generally 240-250F), holding it for long enough, and having a good vacuum seal in the end, and using a trusted recipe that's actually safe to can with that process. The jars typically used aren't magic, they're just something that can take those temperatures and reliably produce a good seal.
So if hypothetically you have a vacuum bag that you know can survive the pressure canning temperatures with the seal completely intact, it would work.
But it seems difficult to find out if vacuum bag materials can actually do that. As far as I can tell, vacuum bag manufacturers don't generally publish upper temperature limits. I would be concerned about the heat seal degrading, the bag weakening and possibly bursting, and so on. I suppose you could try it and see, since it should be fairly obvious if a vacuum bag is no longer airtight. (I'm assuming the plastic is heat safe in terms of food contact to those temperatures, since it's apparently safe to make the heat seal in the first place.)
And for emphasis: you really do need a trusted recipe. The heat needs to penetrate sufficiently into the meat for it to be safe, so if you change the type of meat (different cut, different size, etc) you're potentially making it unsafe. See for example NCHFP on canning meat, and Carolina Canning (from Clemson) on why the list of what you can do is limited.
I'll add to what Jefromi said.
I think you're going to have a hard time finding a heat sealable bag that can handle 252F in a pressure canning process. A quick look at mylar bags and HDPE shows a melting point of right around 250F. I'd be afraid they would leak or leach unpleasantness into the food.
There should be a process for this because you can purchase tuna and other meat in shelf-stable foil pouches. I don't believe it was irradiated.
Another option is to do lower temperature canning. Food stuffs that are high enough in acid to prevent botulism can be simply boiled instead of pressure canned. Jellies or tomatoes recipes will have acid added for this reason.
Given your history, I suspect you may want to bottle beef. I don't know of a high acid beef canning recipe.
Note that in pressure canning (and regular canning) the material in the jar BOILS, and the lids vent excess pressure, then seal as the jar cools.
A sealed vacuum bag would presumably burst, as it has no relief mechanism (which the properly tightened canning lid does, even if many are blissfully unaware of it.)
As such, I don't think this it at all practical in the home kitchen. "Pouch tuna" seems to indicate that industry can manage something like it. Presumably industry is sealing the pouches inside the pressure vessel, which is a bit out of reach for home production.
There are microwavable (non metallic) retort pouches designed to withstand 130 degrees C which exceeds the required temperature for full sterilization in an autoclave / pressure canner or perhaps even a pressure cooker. These effectively become MRE's once they've been processed properly. You will need to ensure thet the cold point within the pouch reached the required temperature for the required amount of time to kill off all hazards. Pouches such as this are very widely available in boxes of 1000 in the UK, in the US - not so much but they are out there.