Top 10+ Leftovers You Should Never Keep, Freeze, or Mix (But Families Do Anyway)

Rice and Pasta: The Silent Killer in Your Fridge

Uncooked rice and pasta can contain spores of the bacterium, Bacillus cereus, which is common and widespread in our environments. Notably, B.

cereus can survive even after the food has been properly cooked. B.

cereus is one of the most common causes of food poisoning in the United States. Eat pasta and rice immediately after cooking it.

Afterward, cool it quickly by storing it in the fridge. Eat the leftovers within 1 day.

Remember, in the food safety temperature danger zone of 40-140°F, the amount of bacteria can double every 20 minutes so time is definitely of the essence. This applies to rice and pasta especially, which often have the bacteria bacillus cereus, also known as B.Cereus.

The spores of the B.Cereus can survive initial cooking, adn then during the moderate temperature period, grow quickly. These bacteria can rapidly multiply and, in severe cases, lead to liver necrosis and even death.

Raw Mushrooms: The Slimy Surprise

Since mushrooms contain a lot of water, when you freeze them raw, the water inside the mushroom cells can form ice crystals. As these crystals expand, they rupture the cell walls, resulting in a slimy and mushy texture upon thawing.

Freezing will change the color and texture of mushrooms, making them both darker and softer. Since they have a high water content, mushrooms are more prone to freezer burn than other foods.

Note that sometimes washing mushrooms can make them soggy and lead to freezer burn. Mushrooms should be cooked before freezing.

Eggs in Shell: The Expansion Explosion

But avoid putting whole eggs in the freezer, even if you score a dozen on sale. Once frozen, the insides expand and the shells often crack.

However, don't try to freeze raw eggs in the shell. The interior will expand when frozen, which may cause the shell to crack, wasting food and leaving a mess behind.

If an egg accidentally freezes and the shell cracked during freezing, discard the egg. Keep any uncracked eggs frozen until needed; then thaw in the refrigerator.

That's because freezing causes the yolk to become thick and syrupy so it will not flow like an unfrozen yolk or blend very well with the egg white or other ingredients.

Mayonnaise: The Broken Emulsion Nightmare

If you freeze mayonnaise, it will look normal while still in frozen form. However, once it starts to defrost, you will notice that the texture of the creamy condiment changes significantly.

As mayonnaise thaws, that emulsion will break, leaving you with the liquid, acidic ingredients, and oil floating on top of the yolk base. Classic examples of this are mayonnaise and aioli, which is why we as the Food Safety Information Council recommend not making your own mayonnaise or aioli and to stick to supermarket versions.

The oil and water separate when mayonnaise is frozen. Once the mixture is thawed, the creamy texture is replaced with a watery mess.

Soft Cheeses: The Grainy Downfall

If you think tossing Brie or cottage cheese in the freezer is a clever way to avoid spoilage, think again. These soft, high-moisture cheeses do not handle freezing well.

Brie's creamy center turns into a crumbly, sad shadow of its former self, while cottage cheese separates into watery curds. As with other foods, if you freeze cheese you risk ruining the quality of the product—and it is often just too expensive to waste.

Freezing can alter both the texture and taste, especially if the cheese is soft, aged, or full of air pockets. While you can freeze cream cheese, like a lot of other dairy products, it can become grainy when defrosted.

It's still perfectly safe to use, but we don't recommend using it as a spread on a bagel.

Dairy Products: The Separation Story

As a dairy product, yogurt can separate and become watery and grainy when thawed from frozen. Even worse, it might acquire an acidic taste—and some of the live, good-for-you bacterial cultures found in yogurt may be destroyed by the freezing process.

Like a lot of dairy products, sour cream will separate when frozen and take on the lumpy consistency of cottage cheese. It's certainly safe to use, but thawed sour cream won't have the smooth texture you would expect.

Sure, freezing might seem like a smart way to stretch the shelf life of these dairy staples, but think twice. Once thawed, sour cream and yogurt lose their smooth, creamy consistency.

Instead, you're left with a grainy, watery mess that no amount of stirring can save.

Cooked Potatoes: The Grainy Gloop

Freezing baked or boiled potatoes will yield a bunch of grainy gloop, according to the NCHFP, and Rust wouldn't recommend freezing any potato whole. When you go to use thawed raw potatoes in your cooking, they will become discolored.

In some cases, they'll turn black, which renders them inedible. The same can be said for potato salad made with sour cream or other dairy-based ingredients, which also don't freeze well.

While you're better off freezing an oil- or mustard-based potato salad, the salad simply won't be the same when it thaws. The potatoes will be soggy and can turn gray in the freezer.

Leafy Greens: The Watery Collapse

Leafy greens contain a lot of water. When you freeze greens, that water expands and bursts the cell walls that maintain a leaf's structure, resulting in soggy and limp lettuce.

When water (which lettuce contains a lot of) is frozen, it expands. This expansion can damage the cell walls of vegetables, which is why frozen veggies are rarely as crunchy as their fresh counterparts.

Use leftover leafy greens in main-dish salads, or stir them into soups and stews—just don't freeze them. Some foods simply don't freeze well.

Examples are mayonnaise, cream sauce and lettuce.

Overnight Pizza: The Bacterial Playground

One in 3 people admit to eating pizza left out overnight. If those slices have been sitting out for hours, throw them away.

The temperature range of 40-140°F is widely known amongst health and food service professionals as the temperature danger zone—aka the climate where bacteria can thrive. The USDA reports that bacteria can start taking over your leftovers in as little as 20 minutes.

And after two hours, it's deemed unsafe to eat left-out pizza at all. Sorry to break the news, but pizza should absolutely not be stored at room temperature overnight.

In fact, it shouldn't even spend more than a few hours on the counter. In mild to moderate cases, getting food-borne illnesses from room temperature food means stomach pain, diarrhea, vomiting, and fever.

But more serious cases involve hospitalization and even death, like this 2008 case involving leftover pasta.

Cooked Hard-Boiled Eggs: The Rubber Transformation

The cooked whites of hard-boiled eggs do not translate well to the freezer. You'll end up with hard, rubbery eggs that no one will touch.

While raw eggs or whites freeze beautifully, cooked ones can get rubbery due to the lack of fat (yolk) says Proto. Stick to recipes that call for the whole egg if you want to freeze them, like quiches or egg cups.

The proteins in eggs change, becoming rubbery or watery, which affects both texture and flavor. Plus, frostings made with egg whites will separate.

Conclusion: Your Family's Food Safety Depends on Breaking These Habits

The reality is that every year in Australia there are around 4.1 million food poisoning cases. That means one in six of us experience food poisoning once a year.

More than a third of Americans have too-warm refrigerators. This can lead to bacteria growth.

Many of these incidents could be prevented by simply knowing which leftovers to avoid keeping, freezing, or mixing together. The foods mentioned above represent common household items that families regularly mishandle without realizing the consequences.

You can't see, smell, or taste the bacteria that can make you sick. To protect against food poisoning, toss out food after 3 to 4 days in the fridge or move it to the freezer.

Remember, just because something looks fine doesn't mean it's safe to eat. Did you know that something as simple as leaving pizza out overnight affects one in three people?