Why different self-preserved foods don’t preserve each other?

Question

As per the title, if for example butter preserves itself, and strawberry jam preserves itself, why does a blob of butter go mouldy if it’s dropped in the jam jar?

In: Chemistry

Answer 1

It is because the food itself is preserved not the container that holds the said food. For example, butter is not preserved when it is dropped into a jar that contains jam.