Never second guess when it comes to food safety. 
Close-Up Of Potato Salad In Plate On Table
Credit: Christopher Kimball/Getty Images

Growing up, many of us are told that mayonnaise-based salads like potato salad can't be left sitting out, unrefrigerated, because the mayo is apt to go bad and make people sick. And if you're not ServSafe certified (as restaurant workers are) or exceptionally well versed in food safety, it's easy to take that advice at face value. It makes enough sense — mayonnaise is made with eggs, which can make you sick when not stored properly, and mayo itself is a condiment that has to be refrigerated once it's opened.

But the truth is, mayonnaise isn't your main concern when it comes to spoilage. The actual culprit is the potatoes

Yes, it's true! The humble, reliable potato is a hotbed for bacterial growth if improperly stored after cooking. In terms of food safety, potatoes are what's known as a low-acid food. This means that there isn't enough acid naturally present in the food item to inhibit the growth of bacteria. Left in the right temperature range, cooked spuds are a breeding ground for potentially harmful bacteria.

an overhead, close up view of a large bowl of potato salad

What Goes In Potato Salad?

There are obviously variations between different potato salad recipes, but at its core, the standard chilled, picnic-style potato salad consists of cooked potatoes, mayonnaise, and various other seasonings and add-ins. It's not uncommon to find hard-boiled eggs, onions, celery, or even diced dill pickles in a potato salad. Unfortunately, cut vegetables, and especially hard-boiled eggs, are also potentially hazardous foods when left unrefrigerated. Cut fruits and vegetables are major vessels for bacterial growth. When veggies are cut, or the exterior is breached in some way, they release liquid — providing the perfect environment for bacteria to thrive. 

So while you certainly want to boost the flavor and texture of this essential cookout side, it's worth remembering that these add-ins can also increase the potentially hazardous nature of your potato salad. One key addition that both improves the flavor of potato salad and helps slow the growth of bacteria is acid. Mixing in, say, a splash of vinegar or a squeeze of fresh lemon juice not only brightens the taste of your salad, but also makes for a slightly less hospitable environment for harmful bacteria. 

Added acid by no means negates the bacteria-prone nature of the other ingredients, but it does add an extra layer of protection. Of course, the best way to avoid food-borne illness is storing your potato salad at proper temperatures. 

Horseradish Potato Salad
Credit: lutzflcat

How Long Can Potato Salad Sit Out?

When you learn about food safety, one of the first topics covered is the "Danger Zone." According to the USDA, the government agency that oversees food safety rules, the danger zone is between 40 and 140 degrees Fahrenheit. This is the temperature range that fosters bacterial growth. Cooking raw ingredients and keeping food hot can raise food items out of the danger zone, and refrigerating or freezing food items can lower them out of the danger zone. So how long can food stay in the danger zone before it's unsafe to eat? Well, it depends. 

The USDA says food can still safely be consumed after being in the danger zone for up to two hours. However, there's a difference between leaving a bowl of potato salad out on the counter, in an air conditioned home and leaving it outdoors; the rules change a bit when it gets hot outside.

Potato salad is a common staple for barbecues, picnics, and cookouts during the summer, where it may be in direct sunlight at temperatures much higher than what you'd usually consider "room temperature." In these circumstances, it can only be left out for one hour before potentially harmful bacteria may start to grow. And once the bacteria starts, it can't be stopped. The bacterial colonies can double in just 20 minutes after one hour in the sun. Meaning, if you realize a dish of potato salad has been sitting out on the patio for an hour or longer, cut your losses and toss it. 

A safer serving situation would be to have folks dish up indoors before returning outside. Just remember, even indoors, potato salad cannot be safely left out of the refrigerator for more than two hours. Alternatively, consider using a meat thermometer to monitor the temperature (on the surface and in the middle) of chilled side dishes like potato salad and coleslaw in order to keep tabs on when they're close to crossing into the danger zone.

creamy potato salad with cauliflower rice in it
Credit: Allrecipes Magazine

How Long Does Potato Salad Last?

Assuming your potato salad is stored in the refrigerator, the USDA recommends that it be consumed within five days of when it was mad. But keep in mind, five days is intended as the absolute maximum and this rule only applies if the salad was held at a temperature below the danger zone range the entire time.

Labeling your containers is a great way to help yourself remember when something is slated to expire. A small piece of painter's tape and a sharpie can save you a headache — or rather, a stomach ache — later on. If you find yourself unsure as to whether or not your potato salad is still good, or if it has been held at the correct temperature the entire time since being made, follow the old adage from professional kitchens: "When in doubt, throw it out."

Can You Freeze Potato Salad?

Technically, it is perfectly safe to freeze potato salad. As long as you defrost it slowly in the fridge and don't refreeze it once it's thawed, potato salad is totally fine to freeze from a food safety standpoint. 

Now, should you freeze potato salad? No, probably not. Mayonnaise is an emulsion, meaning the microscopic oil droplets are suspended in water and other liquids. When emulsions are frozen and defrosted, they tend to separate. This means that the texture of your potato salad will be extremely grainy. There will likely be water at the bottom of the container once thawed and an oily coating on any of the chunkier bits. In short, the texture will never be the same and you're better off making a new batch. 

Old Fashioned Potato Salad recipe in a wooden bowl
Credit: Allrecipes Magazine

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