The "canning" of foods has gotten very sophisticated.

Remember, "canning" is nothing more than cooking food and their containers, then putting the cooked food in to "cooked" containers (cans or jars) that, once they're sealed, also shrink as they cool, creating a vacuum that makes any surviving bacteria/molds/decomposers starve.

As we get closer to global warming extremes, you can and should expect longer power outages. Folks with gas cooking will have the adantage of being able to "Can" or "preserve" foods that those of us with just electricity won't have.

Using pure nitrogen gas inside these packs also stops "oxidation" and starves 'aerobic" (oxygen breathing) bacteria...so that's one trick. (You might have heard about tire dealers using pure nitrogen to make the inside of your tires last longer).

Vitamin C...ascorbic acid...has also proven to be an excellent preservative.

And there's many more chemicals and techniques....most quite safe....although there were some experimental drugs that were used that created problems and issues. But today's "preserved foods"...even those from a couple of decades ago...are pretty safe.

Those "use by" labels? That's relatively new...and used more to encourage you to replace older foods...than to warn you of them becoming dangerous.

I even did a similar post a few months ago about very outdated "condoms" ....chances are good that they're still "useable and safe" as well...