Ask A Scientist: Freezer Burn

Question: “What exactly is freezer burn and how can I prevent it?” -Amanda J  Seattle WA

Answer: Freezer burn is a state in frozen foods that happens when they become dehydrated, essentially.  Meats tend to suffer from freezer burn the most with their high water content and shorter frozen shelf life, but just about any food can suffer the burn if they’re stored in the right conditions.

How exactly would something become dehydrated in a freezer, you ask?  A food can become dehydrated in extremely cold conditions through a process called sublimation.  Literally, sublimation is when water freezes and leaves the surface of the food as a gas without becoming a liquid first.  In the case of freezer burnt foods, the liquids inside the food freezes into ice crystals on the surface, evaporate and toughens the exterior.  If you aren’t a meat eater or have never seen this happen before, Antarctica is a good example of the phenomenon of sublimation as the entire continent has the lowest temperatures as well as the lowest amount of precipitation on earth… and its a gigantic chunk of ice, more or less.

Wild.

Although freezer burn is harmless to the food, the burnt foods will be tougher overall and probably have adopted off flavors from the freezer.  It’s also a good reminder that by putting things in the freezer isn’t a catchall way to store foods indefinitely as well.  Frozen foods will still oxidize and go bad, but just at a much slower rate than if they’re stored in a refrigerator or at room temperature.  Ideally, everything that you freeze should be used in a year maximum from the date it has been stored in the freezer to retain the best taste and texture.  Vegetables have the longest freezer shelf life of 8-12 months, while cured meats have the shortest shelf life of only about a month.

This being said, how can freezer burn be prevented?  The easiest way to prevent it from happening is not to give foods the ideal situations in which their liquids in the food can evaporate.  When packaging foods to freeze its best to thoroughly wrap foods in cling film tightly so that as little air as possible comes in contact with the food that would aid evaporation.  Alternately, foods frozen in liquids retain moisture much better than their dry counterparts, although this isn’t a great idea for space conservation.

Secondary to the packaging of the future frozen foods, the temperature of the freezer plays a part in preventing freezer burn.  Ideally, the freezer should be set to about 0 degrees farenheit (or slightly lower) and should not vary much from this.  The extremely cold temperatures cause smaller ice crystals to form and less chance for evaporation.  The end result will be, with proper packaging, a better quality product with less deterioration.

Lastly, if vegetables are going to be frozen for storage then they should be blanched prior to freezing.  Blanching, which is simply boiling or steaming a food and then shocking it in cold water, aids in freezing foods because it stops enzymatic reactions in food that result in off color, texture, nutrient loss and quick deterioration.

Then again, this is a good argument that it also is better to get fresh items as you need them rather than buying the Costco sized package for a family of one.  Just saying.

-By Hannah Nordgren, Science Enthusiast

Comments

In order to comment on BlogHer.com, you'll need to be logged in. You'll be given the option to log in or create an account when you publish your comment. If you do not log in or create an account, your comment will not be displayed.