According to the Minnesota Food Code, all frozen food must remain frozen until ready to use and the USDA recommends setting freezers to zero degrees Fahrenheit. This got us wondering; why zero? Is zero a scientifically determined number, or is it in the correct temperature range and just happens to be a good round number? Will two degrees work just as well? Or maybe -12.5? This week we’ll take a good look at freezer temperatures and how zero degrees became the standard for ServSafe Food Managers.
ServSafe Food Managers and Freezer Temperatures
The history of the standard of zero degrees goes back to the 1930s when the American Fruit and Vegetable Coalition advocated zero degree temperatures because it was, in fact, a round number. Prior to this, freezing recommendations had been set at 14 degrees Fahrenheit. Science didn’t even come into the conversation until much later.
According to the laws of thermodynamics and the use of a mathematical logarithm known as the Van’t-Hoff equation, scientists much smarter than us were able to show that there is a uniform lowering of the velocity of chemical reactions in any substance as temperatures decrease. To break it down in terms those of us without PhDs in chemistry and physics can understand, once the temperature reaches zero degrees, the molecules and atoms in frozen product slow to the point where there is little perceptible movement. This means that bacteria cease to grow and there is very little loss of nutrition in foods frozen below zero degrees. Using this method, it has been determined that the ideal range of freezer temperatures is between zero and -22 degrees Fahrenheit.
So now that we know why ServSafe food manager training tells us to keep freezers at zero degrees, why don’t we go further and freeze product closer to the low end of the range?
First, while bacteria are held at bay indefinitely, that doesn’t mean that there isn’t a risk of freezer burn. Freezer burnt product may still be safe to eat from a food safety standpoint, but it sure isn’t pleasant from a taste and texture standpoint. Long exposure to extremely low temperatures will keep your food safe to eat but will tarnish its quality.
Finally, it’s unwise from an efficiency and energy use standpoint. Keeping your freezer at the upper end of the freezing range and closer to zero degrees will use a lot less electricity and keep utility costs down.
As a ServSafe food manager, what temperature do you set your freezer?