The paper containers are aseptic packages, I don't know the details of the equipment but I'm sure broth is very similar to UHT pastuerized milk, heated to high temp for a few seconds and decanted into the sterile container then sealed. I know for things like peanut butter, etc. they not only heat the product while constantly mixing/stirring, but also add stabilizers, then vacuum pack.

I am taking the FDA's Better Process Control School for acidified foods next month and don't know how much detail is going to be provided on the large-scale commercial process (this is a 2-day course for farmers, not the usual 4-day course) but will share info here afterwards.

Actually the cardboard containers like Swanson's Broth comes in can and do withstand high pressure processing and vacuum sealing. They use high pressure steam autoclaves. You can go to Discovery Channel and pull up their How It's Made series and watch all the shows on commercial food preservation.

Depending on the food they use irradiation, pasteurization, high temp flash pasteurization, added preservatives and stabilizers, and high pressure and temperature room-sized autoclaves. None of which we can do at home.

Dave

Aseptic packaging is a fascinating process.

The containers are sterilized separately from the food using a 30% H2O2 solution (hydrogen peroxide).

The food (broth, tomatoes, whatever) is heated up to 295 degrees F for just a few seconds (3 to 5 usually) and goes into a sterile environment, where it is packaged into the sterile containers.

If you have an extra $100,000,000 you, too, can do it at "home".