Freezers that have temperatures lower than the default setting maintain the quality of food for a longer time. The minimum temperature for a freezer is 0 degrees Fahrenheit, although temperatures of -10 or -20 degrees Fahrenheit keep food fresh longer.
The freezer temperature should be tested with a thermometer to ensure it is maintaining a food-safe temperature. One practical way to test the freezer temperature is to examine a container of ice cream, which should be completely solid if the freezer is cold enough. Food that is stored improperly can develop freezer burn, which affects the quality but not the safety of the food.