What you see: Unexpected ice crystals, or maybe something that looks like a snowdrift on your frozen food.
What it is: Frost!
Eat or toss: In many cases, eat! If you’re planning to heat it up, you may not notice any difference once the food is prepared. If, however, you see discolored patches under the ice crystals or elsewhere on the food, that’s freezer burn. Certain food textures could be permanently disrupted by ice crystals (looking at you, ice cream), while a small amount of ice crystals on another food, like, say, the muffins pictured above, will probably make little difference once the muffin is warmed up. You can also brush or knock off excessive amounts of frost. Even a lot of ice crystals may not impact the quality of certain foods once they’re prepped.
Frost or freezer burn?
In casual conversation, I suspect people often say “freezer burn” to refer to any unexpected clump of ice on the surface of a food. But the type of food and whether the food has actually lost moisture (true freezer burn) will make a difference in whether the food tastes just as you’d expect or may taste off with a less pleasant texture.
Why do ice crystals form on food?
Ice is a sign that moisture’s moving around and crystallizing, but its impact on your food will depend on a couple of factors, particularly if the dry freezer air forcefully yanked moisture out of the food (freezer burn). While freezer burn and frost can happen together, one doesn’t guarantee the other.
“Freezer burn can be equated with moisture loss from the product (quality issue and safe to eat) while frost could be equated with moisture accumulation on the product (temperature fluctuation in the freezer and should also be safe to eat),” explained Sanjay Gummalla, senior vice president for scientific affairs at the American Frozen Food Institute.
Here are some scenarios that could lead to ice on the surface of your food:
- External moisture crystalizes on the food. Often ice crystals appear on frozen foods when water that’s on the food’s surface or in the air crystalizes. It happens on the food and not within the food. So, a little moisture in your frozen bag of bread could show up as tiny bits of ice. Or a brittle icy layer on your pizza. But once you defrost and heat up your leftovers/veggies/bread, you may not notice anything.
- Moisture in the food melts and refreezes on the surface. If a food’s texture while frozen is central to its quality, any melting and refreezing can mess with it. Consider ice cream. If it melts a little, the water may separate out of the creamy ice cream matrix and refreeze as grainy bits of ice.
- Moisture ripped out of the food contributes to an icy crust. The dry air of the freezer can pull moisture out of food, leaving it to crystalize on the food’s surface or elsewhere. Once moisture is sucked away from a food, particularly a food made up of cells, like meats and fruits and vegetables, the quality suffers. We call this freezer burn. Frost on your food does not equal freezer burn. Frost can be brushed off. Freezer burn cannot. Gummalla theorized that “freezer burned areas can serve as the substrate for frost build up—these areas are colder and attract condensation resulting in frost build up.”
Ice crystal build up is more likely if food has been frozen for a long time and if it has been stored in a way that facilitated exposure to moisture, air and fluctuating temperatures. A poorly sealed container, a container that’s frequently opened and taken in and out of the freezer, or a freezer that’s often left open for extended periods of time can make frost and freezer burn more likely. They also increase the odds of food thawing and refreezing, which can further mess with a food’s texture.
What’s the difference between freezer burn and simple ice crystals?
Frequently opening the freezer door and opening the food packaging can let in a surprisingly large amount of water vapor. The resulting ice can slide, break or melt off and the food will probably be fine. But if the ice crystals you see on the food are made up of water that used to be in the food itself, then the food has basically dehydrated and theoretically maybe even erected an ice sculpture with some of the water of its former self. If you see dry, whitish patches on the food, or if you can see that the food has visibly shrunk, then freezer burn is at work and the food will probably taste off. After extended periods of time at any temperature (though it happens faster at warmer temperatures), fatty foods may also go rancid, which is unrelated to freezer burn, but will also result in off flavors.
Can ice crystals alone ever be a signal that the food has lost quality?
If a food’s frozen texture is central to its quality, then ice crystals are clearly a problem. Ice cream’s “protective ice,” as my dad used to call it, will obviously impact the texture and may disrupt the delicately churned balance in the rest of the ice cream, leading to other quality issues.
A lot of ice is also a sign that freezer burn is more likely. Many of the circumstances that facilitate ice formation also facilitate freezer burn.
How to prevent ice crystals from forming on your food
Tips for preventing ice crystal formation are basically the same as those for preventing freezer burn. Keeping frozen foods in tightly sealed containers and packages will make it harder for moisture in the freezer to crystallize on them. Similarly, not leaving those packages open for very long while you’re taking out portions of the food will also help (that way, it’s harder for moisture in the air to sneak in). Set your freezer to 0 degrees Fahrenheit and don’t leave the freezer door open for extended periods of time.
SOURCES:
- Sanjay Gummalla. Senior Vice President for Scientific Affairs at the American Frozen Food Institute. Executive Director, Frozen Food Foundation
- How long can you leave food in the freezer? R. Jackson. EatOrToss.com. October 31, 2025.
