Self-defrosting freezers briefly circulate warmer air inside the freezer between one and four times a day to prevent ice crystals forming on food. Although self-defrosting freezers represent an added expense, they offer more even temperature control and less loss of food to freezer burn.,
Once food is frozen solid, it is mostly protected from freezer burn. Freezer burn is the term for dehydration caused by ice forming frost on the packaged foods and food containers in the freezer. Freezer burn can result in a lot of wasted food, as it ruins the texture, color and taste of food, especially meats, if it can't be trimmed away. Self-defrosting freezers prevent the build-up of ice crystals on packaging and in the air space inside storage containers where food is only thinly wrapped or unwrapped entirely. Self-defrosting freezers have a mechanism to heat the unit’s evaporator coil and melt any ice that forms on it. The water then drains away, or, if the freezer is combined with a refrigerator, helps to maintain proper humidity levels in the refrigerator compartment. Also, the defrosting and cooling cycles circulate air back and forth from the refrigerator to the freezer to maintain the proper temperature in each compartment.