Some kinds of food packages are either vacuum-packed or else packaged with nitrogen in place of air. What this accomplishes is the removal of (most) oxygen. Oxygen likes to form compounds (oxides) and it is famous among chemists for being one of the most volatile and corrosive of the elements. Nitrogen, on the other hand, is pretty tame, inert stuff.

If I know something is vacuum-packed or else packed in nitrogen, I wait to the last minute to repackage it. It will last better in the original package.