I have some American Cheese with fine white crystals on the outside of each slice. They have a gritty texture. Is this a sign that the cheese is spoiled, or just lactic acid salts like aged cheese gets?
It is calcium lactate crystals. It is safe to eat. On regular cheeses it is a sign that it is aged well. For packaged, sliced american cheese I am not sure I would care for it. But it is a matter of personal preference.