Why refrigerate in separate container?

[automagic]

I just noticed that on a can of string beans it says to refrigerate after opening in separate container. I have always just used half the can plopped it in the fridge and used it a few days later with no ill effects (yet). What could happen if the food is in the fridge in its original can after opening?

[Musicat]

Cans can rust. Presumably, the separate container won’t be metal.

[Harmonious_Discord]

The metal interior of the can can have a chemical reaction with the food and air that doesn’t happen if the can doesn’t have air in it. Some foods that have bad reaction to the metal and air are sometimes put in a can with a plastic coating to allow you to store the food in the can.

[tellyworth]

Is it dangerous to store leftover canned food in the refrigerator in the metal can it was purchased in?

No, the food is safe. It might taste rather tinny after awhile, but it is safe.

There are lots of claims around that it’s dangerous, but I think that’s an urban legend - lots of contradictory explanations, no cites, and the same explanations applied to different types of can (tin, steel, aluminium). Modern cans seem to have some kind of plastic coating on the inside, but the warnings seem to date back to the days of real tin.

[Ostrya]

I think Harmonious Discord is right, except I think in recent years manufacturers of cans began to line them internally (this link says it’s with a lacquer) to protect against the potential O2/food reaction.

From link:

Dissolution of the tin coating into the food
Although tin is corrosion resistant, acidic food like fruits and vegetables can cause corrosion of the tin layer. Nausea, vomiting, and diarrhea have been reported after ingesting canned food containing 200 mg/kg of tin. A 2002 study showed that 99.5% of 1200 tested cans contained below the UK regulatory limit of 200 mg/kg of tin, an improvement over most previous studies largely attributed to the increased use of fully lacquered cans for acidic foods, and concluded that the results do not raise any long term food safety concerns for consumers. The 2 non-compliant products were voluntarily recalled.