The FDA recommends keeping the refrigerator temperature at or below 40 degrees, which slows bacterial growth and maintains quality, according to the University of Nebraska extension service. A refrigeration repair website suggests 38 degrees as an optimum temperature. A unit set for 38 degrees can start cooling at that temperature and turn off at 35 degrees. Setting a temperature below 35 degrees requires a forced defrost cycle and uses additional energy.
Keep the freezer at zero degrees, according to the FDA. The Nebraska extension service points out that zero degrees does not kill most bacteria, but it does stop bacterial growth. Flavor changes occur over time with frozen foods, and quality decreases the longer a product stays frozen.
Measuring Refrigerator Temperatures
The FDA recommends using appliance thermometers to monitor refrigerator temperatures. Buy two thermometers, one for the refrigerator and one for the freezer. Make thermometers easy to read and place them near the front. A refrigerator manufacturer suggests putting a thermometer in a glass of water. Check the temperature on first opening after the door has been closed at least eight hours. In this way, you are checking the temperature of something in the refrigerator, rather than the air inside the refrigerator. To adjust a temperature, adjust one control, then wait 24 hours to take a reading.
Measuring Freezer Temperatures
Use the same FDA recommendations for measuring freezer temperatures as those for refrigerators. To get an internal temperature of a frozen product, the refrigerator manufacturer suggests putting a thermometer between two sacks of frozen vegetables. Like refrigerators, wait at least eight hours before taking a temperature reading.