How does a sealed container preserve food safely at room temperature for months/years, but a sealed contained of leftovers in the fridge spoils in less than a week?

Question

For dinner today, I had a liquid precooked curry mix (sauce, cooked veggies etc..) that comes in a little foil pouch and doesn’t have to be refrigerated- just heat the pouch in hot water for 5 minutes and pour over cooked rice. All the food is precooked, just chilling at room temperature in that pouch for months, but perfectly safe to eat.

How can it be so safe and not-spoiled like that, when the same ingredients sitting in a Tupperware in the fridge will go bad in just a few days?

In: Chemistry

Answer 1

Canning/jarring involves removing the oxygen and heating the contents,while sealed, to high heat to kill bacteria.

More complicated then slapping a Tupperware lid and putting it in the fridge.

This is also why most things must be used immediately after opening or at least refrigerated because it’ll go bad.