Freezer burn occurs when frozen food undergoes dehydration due to improper packaging. The humidity level in a freezer is usually quite low, so if food is not stored in airtight packaging, water in the food can be drawn out into the freezer atmosphere by sublimation. Also, because the food is exposed to air, oxidation can occur, though at the lower temperatures in a freezer, these reactions are quite slow. Thankfully, although freezer burn looks nasty it’s not a food safety concern, it just causes discoloration.