Got (too much) milk? Don't put it in the freezer - at least, not if you want to drink it. Milk is completely safe to freeze; it's just not the most pleasant once it's thawed. The otherwise smooth, creamy beverage will separate into chunks of other compounds floating in water. While it's still going to be OK to throw into a smoothie or bake with, your milk will not be pleasant to drink. That's why some people use an ice cube tray to separate the milk before it's frozen to later throw into a blender or melt into a recipe.
Don't expect to thaw leaves of lettuce to use in a salad later. Greens contain a lot of water. When you freeze greens, that water expands and bursts the cell walls that maintain a leaf's structure, meaning your crisp and fresh greens are now soggy and limp. That's fine if you're simply throwing them in a smoothie or sautéing them in a pan; but if you want to reuse these greens for a salad or other dish where the greens are eaten raw, freezing them is a bad idea.
Cooked eggs are perfectly fine to freeze and can actually make a convenient on-the-go breakfast. But when they're still in the shell, you don't want to try to preserve them in your freezer. The raw egg inside the shell expands when frozen, which may cause the shell to crack and leave a mess behind for you to clean up.
Raw potatoes contain a surprising amount of water; when you freeze them, the consistency is altered irreversibly. Once the potatoes are thawed, they will take on a mushy, slimy texture that is far from pleasant to eat. It will also be difficult to cook them many of the ways potatoes are best prepared.
After you freeze it, mayo is not going to be something you ever want to spread on your sandwiches. The condiment transforms from creamy to clumpy. Gross. Mayonnaise has a pretty long shelf life in your fridge, but if you don't tend to use much of it, you may not want to buy mayo in bulk.
You can freeze cheese safely without encountering any health risks - but you will risk your cheese's quality. If you're preserving a quality chunk of Brie or sharp cheddar, you may want to refrain. Freezing can alter both the taste and texture of cheese, especially if it is aged, has air pockets, or is soft. But if you're simply trying to make your shaved Parmesan last a little longer, freezing it is no big deal.
Cucumbers are one of the most hydrating foods you can eat - largely because they contain so much water. More than 90 percent of a cucumber is made up of water! So once you freeze a cucumber, the water crystallizes into ice. That's all fine and dandy, but it will mess with the texture of your cucumber. If you, like most people, love cucumbers for their crunch, you may want to keep them out of the freezer. When they thaw again, they'll be more mush and less crunch.
Tomatoes just don't hold up in the freezer; once you thaw them, you're going to end up with a runny, gooey mess rather that a plump, fresh tomato. This change in texture is in large part due to the amount of water in a tomato. However, if you want to save tomatoes for another purpose, such as to use in a soup or sauce, freezing them is perfectly acceptable. Their flavor (not their texture) holds up, even months later.
There are many great ways to use the leftover half of an avocado. But freezing it is not a good idea. When you thaw the avocado to slice on a salad, mush into guacamole, or eat with a spoon, you're going to be sorely disappointed. The creamy, light texture of an avocado transforms in the freezer. It becomes slimy, mushy, and altogether unpleasant.
Dried spices have a really long shelf life (as long as you clean your spice rack), but if you don't cook very often you might have some that are close to their expiration date. But preserving them in the freezer is not a good idea. You want to keep spices in a dry environment to prevent clumping, but freezing and thawing can result in unusual levels of dryness or humidity added to the spice. Additionally, the flavor of spices can alter when they freeze.
This may sound obvious, but do not under any circumstances put a whole unopened can of something in the freezer. Water expands when it freezes; if you're not careful, you could end up with an exploded can and a huge mess of spilled mush to clean up.
If you thaw meat, you should probably cook it. Though freezing the meat again is perfectly safe according to the USDA, it will leave the meat dried out and altered. As a result, once you cook the meat again later, it may not be a texture you enjoy. Speaking of which, you're probably defrosting your food all wrong - here's how to do it right.
More From The Daily Meal:
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15 Healthiest Frozen Dinners
25 Healthy Breakfasts You Can Freeze and Take to Go
Grocery Items You Should Stop Buying and Just Make Instead