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How to Maintain the Right Temperature for Refrigerators and Freezers

Did you know that honeydew melons should be stored at 45°-50° but that shellfish needs temperatures below 41°F? To be safe most commercial refrigerators are set at 38°F – a few degrees colder than the 41°F maximum temperature recommended by the U.S. Food & Drug Administration (FDA). But, in busy restaurants, maintaining that temperature can be challenging.

The refrigerator or freezer’s thermostat may be the issue. Aside from mechanical failure – which occasionally happens – the thermostat may be placed in the wrong location to give accurate readings. Most commercial thermostats are located near the door, where readings will be several degrees warmer than positions near the back, closer to the compressor.

Checking the right temperature

The ideal temperatures for stand-alone refrigerators are 41°F/5°C for the top shelf (typically the warmest) and 34°F/1°C at the bottom (coolest) shelf. Walk-in units are cooler, typically 35°F near the door and 37°F in the colder sections.  For freezers, the ideal temperature should be 0°F/-18°C. Set the thermostat to the warmest safe setting.

To check the temperature, the FDA advises kitchen managers clients to invest in a refrigerator/freezer thermometer for all their cooling units – including cooling drawers.

Refrigerator/freezer thermometers typically measure temperatures between -20°F and about 60°F. Some advanced electronic models feature audible alarms when temperatures get too hot or cold, and others record temperatures so kitchen managers can monitor fluctuations over time. This is particularly handy if they worry a unit may be failing.

Temperature logging

Another option is to install a temperature logger (like the type used for shipping) that records temperatures and sends email or text alerts when temperatures go above or below pre-established parameters.

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Single use temperature logger

Loggers come in all shapes and sizes – some are extremely advanced, providing Wi-Fi connectivity with push notifications to mobile devices while others are simple single-use devices that log records for 2-6 months then get thrown away.

With all loggers, of course, the goal is to gather data when there is no technician or manager around to keep an eye on the numbers. Especially when the refrigeration equipment works unreliably or inconsistently, a logger can often be the only way to determine when malfunctions happen.

To take an accurate temperature reading, place a refrigerator/freezer thermometer in the middle of the top shelf of a standalone unit or on an upper rack at the back of a walk-in unit. A 15-minute read can give you a good indication of temperature, but for true accuracy, leave the thermometer in place overnight. Check the reading in the morning before kitchen activities begin.

For freezers, position the thermometer on the top shelf near where the door opens. Leave it for a few hours – overnight isn’t necessary. The temperature should read 0°F/-18°C.

Once you know the true temperature inside the refrigerator or freezer, adjust the thermostat accordingly. Many units have digital thermostats that can be adjusted with the press of a button, but walk-in units generally have mechanical thermostats that are adjusted with a screwdriver.

Refrigeration slows bacterial growth to keep foods safe and fresh, but selecting the proper temperature is a balancing act. Temperatures that are too high or too low affect the texture, taste, appearance, and nutrition of food. Maintaining optimal refrigeration temperatures, therefore, is an essential step in determining the quality of food the restaurant serves.

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What you can do…

As a maintenance technician, you play an important role. Take the extra step to check the actual temperature of your clients’ refrigeration equipment, and recommend they add refrigerator/freezer thermometers to each of their units as backups to alert them to impending failures. It should not need reminding that the loss of contents in a freezer can add up to thousands of dollars.