Eli5 How can canned meats like fish and chicken last years at room temperature when regularly packaged meats only last a few weeks refrigerated unless frozen?

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Eli5 How can canned meats like fish and chicken last years at room temperature when regularly packaged meats only last a few weeks refrigerated unless frozen?

In: Chemistry

Part of the canning process usually includes cooking in the can after it’s sealed, so that any bacteria inside is killed and there’s no way for more bacteria to get inside to spoil the food.

The process of canning includes a step after the vessel containing the food is sealed where the contents are heated above a temperature where bacteria can survive thus killing all the bacteria. Since it is sealed no new bacteria can get and cause the meat to spoil.

In contrast, refrigeration does not kill off all the bacteria. It merely slows their multiplication significantly so it takes a lot longer to go bad than at room temperature but it is in fact slowly becoming more infested with bacteria every second. It’s just kept below a level where it will hurt us for as long as possible.

The canning process heats the food to a safe temperature while also creating a vacuum and sealing out pathogens that could potentially get into the food. This creates an environment in which it is highly unlikely for harmful bacteria to grow, resulting in a more shelf stable food. Fresh meats are exposed to oxygen, which most harmful food-borne bacteria need in order to reproduce.

How does botulism develop in canned foods? Sorry, piggybacking this question off of OP.

Canned food will eventually go bad because metal rusts/degrades and eventually the seal is breached, even if not noticed. If you ever find a can that has been sitting for, say, 50 years, I wouldn’t trust it. Besides, by then the contents would likely have become quite disagreeable…