Adulteration is the act of making food or drink — or another product — less pure by adding something cheaper or worse, or it is the dirty result of that act. “Adulteration of cooking oil” means someone put the wrong stuff in. Same serious, legal, food-safety flavour as adulterate. It is a noun: the adulteration, not “they adulteration it.” News stories use it when a factory or a seller has cheated on what is inside the packet.