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

Your pre-cooked meal pouch was made in a place that was very, very clean (aseptic) compared to the conditions in your kitchen. The food maker follows important rules to keep grocery store food safe (government and industry regulations about hygiene and manufacturing conditions). There are probably some few germs in there, but it usually takes a long time before they grow enough to ruin the food or make you sick.

Food that has been in the clean — but not very, very clean — area of your kitchen picks up germs that grow even faster with the bit of heat that comes from a cooked meal. So, it takes much less time for them to grow enough to ruin the food or make you sick.

Edit: as /u/nadalcameron points out, you can preserve food very well in your kitchen. “Canning” is a time-tested way of using pressure and high temperature to get the pasteurization or sterilization of industrial production at home. Pickling is another accessible way to keep germs at bay and preserve food.