Don't Eat Them: 10 Tell-Tale Signs That Your Food Has Gone Bad

5. Frozen items develop ice crystals or frost.

Although frozen foods covered in crystals or frost may indicate that they were kept extremely cold, the truth is quite the opposite. Ice crystals on the surface are a sign that the food probably came up above freezing and then was re-frozen. So if you can't tell what the item is, just throw it in the trash bin.