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You may have noticed that ice cubes kept in the freezer for a long time have a tendency to shrink as water is lost. This is because in dry freezer air, ice can transform directly into water vapour without first becoming a liquid, in a process known as sublimation. Ice sublimates in an effort to equilibrate with the vapour pressure of air in the freezer. The water lost from food items during sublimation is redeposited on the food’s surface, and on refrigeration cools as ice crystals. The moisture loss means that fruit and vegetables can become shrivelled and dry, while meats can develop a leathery texture and dark spots. The dehydration creates pockets in the food which are then open to the air, accelerating oxidation. In fatty foods, this oxidation can cause unpleasant flavours. Food with freezer burn is unpalatable, but safe to eat.