What Is the Optimal Freezer Temperature?
When freezers were invented, the ability to store foods for longer periods of time represented a major step forward in preserving food and controlling bacterial growth. Freezing chills food quickly enough to allow it to store at a temperature where bacteria can’t grow, which means that food lasts longer without spoiling. Notice I didn’t say freezing food kills the bacteria, so if a freezer starts warming up, the potential for bacterial decay starts again too.
Water may freeze at 32 degrees Fahrenheit, but most foods require a much lower temperature to freeze properly, often around –10 degrees Fahrenheit. In a perfect world, storing frozen food at 0 degrees Fahrenheit would be enough. Since having two freezers to span this range for short and long term freezing, a good compromise establishes a temperature of –7 degrees Fahrenheit for best results.
Why not compromise with exactly half of the difference, at a temp of –5 degrees Fahrenheit? Good question. The faster food freezes, the smaller the ice crystals that form. Smaller ice crystals contribute to less chance for food dehydration and oxidation, which results in “freezer burn.” So while storing food at 0 degrees Fahrenheit isn’t a bad idea, a freezer should ideally be colder in order to freeze foods quickly and allow more room to fluctuate when adding new foods.
It is important to realize that temperature isn’t the only factor that causes freezer burn. Technically speaking, freezer burn is food dehydration caused by the air circulating inside the freezer. As moisture leaves the foods you freeze, it escapes into the air inside the freezer.
Therefore, keeping your freezer at a proper freezing temperature helps control the level of moisture in the air. The cooler the temperature inside the freezer, the less it heats up when you put more food in. The less the freezer heats up, the less moisture released into the air to cause freezer burn.
Keeping freezers more full is a good strategy for keeping your freezer cold while keeping the cost of operating it down. A full freezer stays cold longer, making it significantly easier to keep frozen foods cold rather than trying to cool all the excess air inside the freezer. A full freezer will keep food cold for two days during a power outage, but a freezer that’s only half full will keep food cold for only 12 hours or so. You can even add pantry items like flour, rice, or dry beans to fill up empty space in a freezer to improve its overall operation.
Many people never adjust their freezer from the time it gets set when being delivered. It can be very important to occasionally adjust the freezer temperature somewhere between 0 and –10 degrees Fahrenheit, ideally around –7 degrees for most foods.
Also, try to keep your freezer full as often as possible. When it starts to get empty, add some pantry items to take up the extra room. When you’ve established a routine for keeping your freezer at a certain temperature, you’ll be amazed at the difference it makes for the quality of your food and the cost of your electric bill.