Science & Technology

Is It Safe to Eat Food That Has Freezer Burn?

Is there anything worse than the emotional rollercoaster of realizing you still have ice cream in the freezer and immediately discovering that it's transformed into a chewy, gummy, icy mess? Well, you still have ice cream (sort of), so it's not all bad. But still, what's going on there? Why do things go bad in the freezer?

Related Video: Foods to Never Put in the Freezer

Ice Rage

What happened to your ice cream — and your dried-out chicken, and your shriveled peas — is freezer burn. "Freeze" and "burn" are basically as opposite as you can get. And freezers are supposed to preserve food, not ruin it. So when you pull a snack out of the freezer only to discover that it's been rendered basically inedible, it feels like the ultimate betrayal by the appliance you trusted most. The thing is, freezers don't stop time; they only stop things like bacterial growth and enzyme decay. But just as high temperatures can cause water to escape in the form of steam, low temperatures can make water disappear as well.

When liquid water is heated to its boiling point and becomes gas, it's called evaporation. But when it goes straight from solid ice to gaseous vapor, it's called sublimation. For that to happen, the ice has to be in a cold, dry place with the exact right amount of air pressure. For dry ice, sublimation readily occurs at room temperature, which is why the solid cubes pour off enough steam to fill a rock-band stage. But for water, the effect is harder to spot because it happens much more slowly.

It happens, though, and the evidence is in the dried-out, discolored steaks you forgot in your freezer. What's happened is the water inside the meat has been drawn out into the air, then turned back into solid ice crystals on the meat's surface (just like sublimation means going from solid to gas, "deposition" means gas-to-solid). That's why the more water there is in a given food, the longer it takes to get freezer-burned. Meat dries out pretty quickly, but soup takes a long, long time to lose its moisture. As for the characteristic discoloration, that's another side effect — as the water leaks out of your steak, it's oxidized by the surrounding air, changing color like a browning apple.

Don't Get Burned

Freezer-burned food isn't spoiled, but it's not especially tasty, either. And unfortunately, it's inevitable. But there are a few steps you can take to stave it off as long as possible. The most important thing to do is keep your food wrapped up extra tight. That's why people preserve things in Mason jars and use vacuum sealers — they keep the air out. If the water in the food doesn't have contact with the dry air around it, it won't be able to sublimate. Other than that, the only thing that's sure to work is to make sure you eat your food in a timely manner. If you wait six months to eat that ice cream, you've got nobody to blame but yourself.

Actually, sometimes people freezer-burn food on purpose — though you might know it better as "freeze-dried." That's right; astronaut ice cream is basically just ice cream that's had all the water sublimated out of it. So the next time you forget about those tasty treats in the fridge, you might console yourself with the knowledge that you didn't leave them inedible, just bunker-ready.

Get stories like this one in your inbox each morning. Sign up for our daily email here.

For more explanations of food mysteries, check out "What Einstein Told His Cook: Kitchen Science Explained" by Robert L. Wolke. We handpick reading recommendations we think you may like. If you choose to make a purchase through our links, Curiosity will get a share of the sale.

Written by Reuben Westmaas April 24, 2018

Curiosity uses cookies to improve site performance, for analytics and for advertising. By continuing to use our site, you accept our use of cookies, our Privacy Policy and Terms of Use.