Causes and Prevention of Freezer Burn

Frozen food, when poorly wrapped, or left in the cold for too long, can eventually develop freezer burn. Ice crystals form on the surface, and the food itself becomes discolored and dried out. Although it is not dangerous to eat freezer burned food, the smell and taste is a bit “off”. The characteristic cardboard-like smell and nasty flavor occur because fats in the food have become oxidized, creating unwanted chemical byproducts.

What Causes Freezer Burn?

Cold air is dry air, whether it is in the great outdoors or behind the door of your freezer, and water evaporates easily into dry air. This is why skin has a tendency to become dry in the winter. Food also contains moisture. When it is placed in the freezer, the water in the food expands as it freezes and forms ice crystals. If frozen food is poorly wrapped, water molecules can evaporate from the surface of the crystals, leaving behind dehydrated spots.

How to Prevent Freezer Burn

The key to avoiding freezer burn is to wrap items as tightly as possible to prevent water from evaporating from the food. Here are the steps required to properly prepare food for freezing:

1. If you buy large portions of meat, fruit or vegetables in bulk, start by separating the food item into smaller portions that correspond to the amount you would typically need for preparing a meal.

2. If the food is a solid item, such as a slab of meat, divide it into portions and then wrap each portion tightly in plastic wrap. If the food item is composed of small pieces or is liquid, fill a small freezer bag, making sure to remove air bubbles from the bag before sealing the zipper.

3. Once you have the separate portions sealed in plastic wrap or small freezer bags, place them together into a large freezer bag, again removing the air pockets before sealing the bag.

4. Take the time to clearly label the bag with the name of the food item and the date. Frozen food, no matter how well packaged, does not keep forever, and the longer it remains frozen, the more likely it will develop freezer burn, even if properly wrapped.

Freezing Fruit So That It Thaws Fresh

If you would like to freeze fresh berries and have them thaw out almost as good as new (rather than in a mushy berry soup), use dry ice. First select berries that are not too big, then break up the dry ice so that it is crushed. Finally, mix the berries and crushed dry ice together in a metal bowl. Store the mixture in a cooler for at least 20 minutes. When you are ready to bag the berries for the freezer, transfer them to a plastic freezer bag right inside the cooler. The atmosphere in the cooler is full of carbon dioxide from the dry ice. This will prevent the freezer bag from becoming full of oxygen, which can contribute to food spoilage.

Reference:

• www.uga.edu/nchfp/how/gen_freeze.html
• www.loc.gov/rr/scitech/mysteries/freezerburn.html