Because the last thing you want to hear after setting the table is, “I’m not sure if those mashed potatoes are still good.”

Mashed potatoes are a real boon for the home cook. And is it any wonder, really? Potatoes can be picked up at a bargain at any grocery store, they keep for weeks in the pantry, and they don’t take much to boil, mash up, and turn into the most delicious accompaniment for an array of meals.

But if you made more mashed potatoes than you and your family can eat in one meal, how should you store them and how long will they keep? Join me as I address your unanswered questions about the world’s creamiest and fluffiest side dish!

How Long Are Mashed Potatoes Good For?

The USDA says that leftovers, which include mashed potatoes, can be kept in the fridge for 3 to 4 days and in the freezer for 3 to 4 months.

Freezing puts the bacteria that spoil our food and cause foodborne illnesses into hibernation. So, technically, frozen mashed potatoes will stay safe to eat forever. But after a few months after freezing, they will dry out and become bland—so don’t wait too long to use them up.

Refrigerating the mashed potatoes, however, only slows this bacterial activity down. If the mashed potatoes have been in the fridge for more than 3-4 days, you should throw them away, as you have no way to determine if they’re still safe to eat or not.

How Long Can Mashed Potatoes Sit Out?

What we call room temperature, food safety experts refer to as “the danger zone.” That’s because the bacteria that cause food poisoning grow the fastest in the range of temperatures of 40°F (4.4°C) to 140°F (60°C).

Leave a bowl of mashed potatoes on the counter or the dining table, and the number of bacteria on it will double every 20 minutes. In a few hours, this harmless side dish will have turned into a breeding ground for germs that can make you and anyone else who eats it sick.

Keep mashed potatoes out of the danger zone. The USDA recommends that cooked foods not be left out for more than 2 hours. In summer, when the outside temperature is 90°F (32°C) and above, this time is reduced to only 1 hour.

How to Tell If Mashed Potatoes Have Gone Bad

If you kept mashed potatoes at room temperature for more than 1-2 hours, or in the fridge for longer than 3-4 days, you should assume that they’ve gone bad and throw them away. (We’ll get to the reasons why in a moment.)

But with that being said, the tell-tale signs of food gone bad include a sticky consistency, an off odor, a sour taste, and the appearance of mold. If you notice any of these signs on your mashed potatoes, it should raise eyebrows. Throw them away; they can’t be salvaged.

To make your mashed potatoes last longer, cover the bowl with plastic wrap before placing it in the fridge (or transfer them to an airtight food storage container with the lid closed.)

If They Smell and Taste Fine, Aren’t They Still Safe?

The bacteria that spoil our food are not the same ones as those that can give us food poisoning. It’s hard to miss spoiled food; it smells off and tastes bad. In contrast, food that’s been kept for too long at room temperature or in the fridge may smell and taste fine, but still be overrun with germs.

Rule number one of food safety is, “When in doubt, throw it out.” If a serving of mashed potatoes has been sitting on the kitchen counter or dining room table for more than 1-2 hours, or in the fridge for more than 3-4 days, you cannot tell if it is still edible. So the only sensible thing to do is get rid of it.

The basics of food safety should always be followed, but they are especially important when it comes to dairy. In other words, if you made mashed potatoes with cheese or cream, you should put the leftovers in the refrigerator promptly and eat them up within a few days.

Won’t Heating Them Make Them Edible Again?

Many home cooks think that heating bad food makes it safe to eat again—but this is simply not true.

Yes, the heat will kill the pathogenic bacteria on the mashed potatoes. As American author Harold McGee explains in Keys to Good Cooking, 15 seconds of exposure to a temperature of 155°F (68°C) effectively eliminates bacteria.

What the heat doesn’t do, however, is inactivate the poisonous, heat-resistant toxins that these bacteria have left in our food. These toxins make us sick within hours and are just as capable of causing food poisoning as the bacteria that created them in the first place.

Even if you have made the most delicious mashed potatoes in the world, food poisoning is not worth the gamble. The Centers for Disease Control and Prevention (CDC) estimates that 48 million Americans contract food poisoning each year. Of them, 128,000 are hospitalized and 3,000 die.

Do Mashed Potatoes Freeze Well?

Yes, mashed potatoes freeze well, and they retain their best quality for 3 to 4 months in the freezer. If you made a large bowl, freeze it in meal-sized portions to have a side dish that can be thawed quickly.

The best way to thaw mashed potatoes is to move them from your freezer to your fridge the night before you want to eat them. You can also thaw mashed potatoes in cold water or microwave them on the defrost setting, but you should never thaw them by leaving them out. (If you do, the mashed potatoes can cause food poisoning by the time they’re completely thawed out.)

A nifty trick is to blanch or boil whole potatoes, then cool, peel, and freeze them. They will retain their best quality for 6 to 9 months, much longer than mashed potatoes, and can be thawed and mashed at any time.

Up next: The best potatoes for soups and stews