I once heard that a problem with common food preservatives in the US
is that they tend to spoil once exposed to oxygen and left at room temperature,
leading to the instruction "refrigerate after opening".
I heard that "food poisoning" is commonly caused in the US
by preservatives which have not been properly stored than
by food which has become contaminated by bacteria.
But I can't find any sources, so I've begun to believe that
I heard or remember incorrectly.