What Is Freezer Burn

Photo of bag of food from a freezer with freezer burn

What exactly is freezer burn and can we prevent it?

There seems to be a lot of confusion about what exactly freezer burn is. According to Wikipedia, freezer burn is a condition that occurs when frozen food has been damaged by dehydration and oxidation due to air reaching the food. Well, unfortunately that is not accurate. And here's why. When they say air by implication they are talking about moisture. The assumption being that when you see ice crystals on the food its from moisture getting into the food. The problem with that is, refrigeration systems are designed to remove moisture. Your freezer is actually a very dry place.

Most people use freezer bags made of plastic to store food in their freezer. In fact, if you take something out of the freezer and try to thaw it out, you'll put it in hot water to try and accelerate the thawing process. But does the bag fill up with water? Does air or moisture migrate into the bag? The fact is air can't pass through a typical plastic bag. Otherwise we wouldn't need warning labels on plastic bags that say keep away from children, this is not a toy.

Frozen food manufacturers go to great lengths to displace any air or moisture inside the plastic bag where they put the food. In fact, in the packaging process at the very end of the line, just before the bag is sealed, a shot of dry food grade nitrogen is shot into the bag to displace any air and the bag is sealed. And even that does not prevent freezer burn. Take a look at the picture of some frozen food that was in my freezer for an extended length of time. The bag was never opened and even though the bag is still full of dry nitrogen, you can see extensive freezer burn has taken place.

Okay if moisture and air cannot penetrate the plastic, and in a lot of cases the bags are full of dry nitrogen displacing any air, what exactly is freezer burn? Well when you take a piece of food out of your freezer it feels to your hand like a solid. But in reality that food has a lot of molecular motion going on inside. In fact the molecules will continue to vibrate and move around unless they are cooled to a temperature of -459.67 degrees Fahrenheit. Which is impossible especially inside a freezer where the normal operating temperature is zero to minus ten.

Well those molecules continue to vibrate and move around inside the food and eventually they will migrate to the surface. And if there is space between the plastic storage container and the food, those moisture molecules will leave the food, go up on top, and form ice crystals. And what they have left behind is a food that is dry. What we refer to as freezer burn.

Okay so the question is can you stop freezer burn? And the simple answer is no, you can not. But there are things you can do to mitigate the sublimation process so that your food lasts longer in the freezer and does not dry out so much. One of the things that you can do is use a vacuum type system. I use the Food Saver system to seal the food in an airtight environment evacuating the air eliminating the space between the food and the plastic. This way when the moisture in the food migrates to the surface the plastic holds it in place. And if you don't have a vacuum type system, once you put the food into a Ziplock type storage bag then you can use a straw to suck the air out and get as much of the plastic bag in contact with the food as possible.

Also consider buying a manual defrost freezer. Manual defrost freezers keep food closer to 0 degrees whereas automatic defrost freezers have fluctuating temperature environments that will not keep food as long. Keeping your freezer full of food or plastic water bottles full of frozen water will also keep temperatures from fluctuating, help food last longer and reduce freezer burn.