Which practice is important for maintaining proper temperatures during food storage?

Using a thermometer regularly is crucial for maintaining proper temperatures during food storage because it allows for the monitoring of food and storage environment temperatures effectively. Temperatures must be kept within specific ranges to prevent the growth of harmful bacteria, so using a calibrated and accurate thermometer helps ensure that both refrigerators and freezers are functioning correctly and that food is stored at safe temperatures. This practice can help in early detection of temperature fluctuations that may lead to food safety issues.

The other options do not contribute to maintaining proper storage temperatures. Leaving the refrigerator door open would lead to temperature increases as cool air escapes. Storing hot food next to cold food can compromise the temperature of the colder food, potentially putting it in a danger zone for bacterial growth. Overloading the refrigerator can obstruct air circulation, making it difficult to maintain consistent and safe temperature levels.