As I understand it, food products, like beans, are heated up to very high temperatures to kill all germs, and then put into a metal can and sealed. Thus, they are sealed while sterile, and so no germs live in them, making them shelf stable.
How is this possible with plastic packaging for shelf stable products like beans, etc.?
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One of two things can be happening. Canning means sealing the food in the container and THEN sterilizing it. Bacteria exist air too, so everything has to be sealed and THEN sterilized. If you “put” sterile food into a sterile container you can still get contamination during the motion of “putting” the food there, from contact with air or contaminated surfaces.
Anyway. Water boils at 100 Celsius, meaning that you can apply a flame of 2000 Celsius through a (very conducting) metal pot and the water (soup, whatever) will NOT go above 100 Celsius until it completely boils off. All the energy from the flame goes into separating the water molecules (from tightly packed liquid to “loose” vapor), and NOT into raising the temperature. So, all you need to boil your foods and sterilize them is a plastic that can withstand 100 Celsius, which is not difficult to achieve.
The second option is that you can achieve sterilization with radiation rather than heat. Radiation can kill bacteria very well, and otherwise not deliver that much energy to the food items (will not heat up much). And radiation would go through the plastic container easier than it would through the metal.
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