The Xmas pudding has been left for a while covered in aluminium foil. I thought it would be ok like this, the pud can last months, but this year I don't think it's so safe. It looks like these holes have been corroded through from inside by contact with the pudding and there is some metal residue on the surface of the pud beneath the holes. What can there be in the pudding that has affected the foil? And does this mean that aluminium foil is not a food-safe covering?