why does “freezer burn” happen, and what actually is it?
In: Physics
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The meat is dehydrating. Even though it’s frozen, the air in your freezer is very dry and water molecules in the frozen food can end up becoming vapor even though they’re frozen. Freezer burn isn’t bad in the sense of the food being rotten or spoiled; in effect, you’re slowly turning the meat into jerky. That’s what makes the ‘burned’ parts have a weird texture to them. For meats it’s hard and chewy because you can’t turn jerky back into meat. For veggies it’s limp and gross because plant cells need water inside to hold themselves up.
At freezer temperatures, proteins gradually denature. This changes their texture and flavor. In addition, water is pushed out, so it is more easily cooked away when the food is heated.
Freezer burn is caused by water sublimation from ice crystals at the meat’s surface into the dry freezer air. Sublimation occurs when a solid substance undergoes a phase change and becomes a vapor without first passing through the liquid phase. The ice crystals on the meat surface sublimate, and leave behind tiny cavities. These tiny yet numerous cavities increase the surface area of the meat and expose more tissue to the air. This accelerates oxidation of fats, which causes the rancid flavors of old spoiled meat
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Water in intact plant and animal cells freeze, expand, and burst changing the consistency of the food.
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