system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Canned tuna. Why does it stay good for so long? Why is light tuna low in mercury?

How is canned tuna cooked, and why is storing it in a can with a bunch of water keeping it good for so long, whereas without the can cooked fish goes bad pretty quickly? And what is light tuna, and why is it lower in mercury than, say, white tuna?
gpt
I don't know about tuna specifically, but canned food in general lasts a long time because the canning process kills all the microorganisms that were in it. Usually you put the food in the can and seal it, then heat it up, cooking the food inside and sterilizing it at the same time. Without the bacteria and fungi breaking things down, the food takes a lot longer to decay.