Once you open a tin can containing food like tomato paste, fruit or sardines, you may think it's fine to cover the opening with plastic wrap or aluminum foil and store it in the fridge. But once a tin can is open, it's not a safe food storage vehicle. Bacteria can grow along the edges of the can in no time at all, and highly acidic foods can take on a metallic taste. If you have leftover ingredients after opening a can, transfer the leftovers to an airtight container. Then be sure to toss the can in the recycling bin.