Discoloration and dehydration of poultry skin or the surface of skinless products during storage is commonly called “freezer burn.” This defect detracts from the appearance of the product and, in the case of either moderate or severe freezer burn, lowers the quality of the poultry. Slow freezing promotes ice formation on the outside of the meat tissue cells, drawing water out of the cells, possibly preventing the tissue from ever freezing, and causing the tissue to dehydrate and shrink. Also, larger ice crystals are formed that may rupture the cells causing the release of the cell contents, increasing drip loss, and resulting in a less juicy and softer textured product as the muscle structure breaks down. This can adversely affect the shelf life of the product. Slow freezing also affects product color. It causes bone darkening as bone marrow material is released into the bone structure and adjacent meat. It causes dark carcasses as the transparency of the skin increases, thus allowing the dark color of the meat to show through the skin. Poultry quality and stability are adversely affected at temperatures above 10 °F. Poultry products begin to thaw from the outside in once the product temperature reaches a temperature above 10 °F, at which time seepage of moisture from the defrosting product results in clear, pinkish, or reddish colored layers of ice. Poultry located in the center of a tightly stacked pallet may not freeze if cold air is prevented from circulating between and around the individual cases.