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?

  • I give the slice a quick rinse and dry with paper towel and the grit is gone.
    – Rich
    Commented Jul 16, 2017 at 5:18

2 Answers 2


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.

  • We made grilled cheese sandwiches with it. They tasted fine. Commented Jan 13, 2012 at 18:16

When the protein in milk (casein) breaks down, the amino acid, tyrosine, will form crystals inside the cheese. These are common in some aged Gouda, cheddar, and, I think, manchego. These are perfectly harmless and actually indicate that the cheese is well aged. I don't know if this is the same as crystals on the outside, and American cheese is certainly not aged.

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