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

Back in the 1880s a French microbiologist named Louis Pasteur showed that heat could be used to kill/deactivate microbes that spoil food. This coupled with the concept that microbes don’t appear out of nowhere meant that food treated with heat then sealed in a container that prevented entry of microbes would be able to stop the food from spoiling. This process is called “pasteurization” and is the underlying concept behind many food packaging today.

Your Tupperware container of food has microbes in it already, and isn’t sufficient seal against their entry either. Cool temperatures can slow down the action of the microbes and delay the spoiling, but it will happen eventually.