Final answer:
A freezer must be maintained at -18 deg C or below to properly preserve food by halting bacterial growth, although it does not kill bacteria, only rendering them dormant.
Step-by-step explanation:
The temperature at which a freezer must be maintained to ensure proper food storage and safety is -18 deg C (0 degrees F). Keeping your freezer at this temperature or below is crucial as it halts the growth of bacteria and preserves the food's quality indefinitely. It is important to note that while freezing at this temperature preserves food, it does not kill bacteria. Instead, the bacteria become dormant and will become active again once the food is thawed. Therefore, it's recommended to thaw food in a refrigerator, in cool water, or in the microwave, never at room temperature, to prevent bacteria from becoming active too quickly.