The effect of freezer burn on food

April 20, 2009

Freezer burn is a common problem that significantly affects the color, texture, and flavor of frozen foods. An article published in the Journal of Food Science Education explains the causes and consequences of freezer burn and the factors influencing the rate of freezer burn. In the narrowest use of the term, freezer burn describes only the loss of moisture from the surface of frozen foods over time. Freezer burn yields an opaque dehydrated surface to food and causes deterioration in color, texture and flavor on the surface of frozen foods during storage. Freezer burn turns beef from red to brown, skinless chicken breasts from pink to tan, and shrivels frozen green beans. Freezer burn occurs when moisture is lost from the frozen food surface via sublimation—the transition of ice directly to the vapor phase—without going through the liquid phase. Sublimation occurs because the vapor pressure of ice at the surface of the food is greater than the vapor pressure of water in the air.

Two modern conveniences have inadvertently contributed to an increase in the dehydration aspects of freezer burn: self-defrosting (or frost free) freezers and individually quick frozen products. Self-defrosting freezers contain a heating coil that regularly melts the ice layer of the refrigeration coils, preventing frost accumulation in the freezer compartment. While this removes unwanted frost, it keeps the vapor pressure of the air inside the freezer compartment low, promoting sublimation from the food’s surface. Individually quick frozen products or those products that have multi-servings promote sublimation because of their large exposed surface area and because they lack the surplus ice associated with traditionally frozen “block” products.
The time it takes frozen food to develop freezer burn varies according to the type, quality and integrity of the packing materials, storage temperature and air circulation inside the freezer.