Mayo Probably Isn't What's Causing Your Potato Salad To Spoil

Potato salad isn't a dish that keeps well as leftovers. Although you can give it new life by roasting it or turning it into a delicious breakfast, if you let this dish sit in your fridge for too long, it may be spoiled by the time you get to it. While you might think the mayonnaise is to blame, the truth is the condiment isn't as prone to spoilage as you might assume. 

Though eggs are one of the main ingredients in the condiment, vinegar stabilizes them because its high acidity level inhibits the growth of bacteria. Opened mayonnaise lasts for up to two months, which means it isn't the ingredient that causes potato salad to spoil. It's actually the potatoes.

Being a root vegetable, they sit in dirt for a long time and that dirt often harbors bacteria. When potato salad is served at warm events like picnics or barbecues, the heat can cause this bacteria to multiply, leading to the spoilage of the entire dish. This is why even if you make a French-style potato salad (the kind without mayonnaise) you'll notice that it can still go bad just as fast.

Opened mayonnaise may be safe to eat for two months, but when you combine that with cooked potatoes, the timeframe is much shorter. According to the U.S. Department of Agriculture (USDA), cooked potatoes only last for three to four days when stored in the refrigerator. But the longer your potato salad is left out at room temperature, the less time you have to enjoy it before it spoils. 

When food is kept at temperatures between 40 and 140 degrees Fahrenheit, the USDA estimates that it only takes 20 minutes for any bacteria to double. The organization also advises against leaving it out for longer than two hours or longer than one hour if it's more than 90 degrees out. For reference, room temperature is about 70 degrees Fahrenheit and a refrigerator is typically 37 degrees Fahrenheit.

Whether you left your potato salad out or kept it refrigerated, you can determine when it has spoiled based on its smell, appearance, and texture. When this meal has gone bad, it develops a slimy texture and a sour smell. You may also see mold, but it can also not be safe to eat before that even appears. However, if you're not sure either way, it's probably best to use caution and throw your potato salad out.

Since the main cause of this dish's spoilage stems from soil bacteria left behind on the potatoes, it's a good idea to clean them thoroughly before putting them in. Scrubbing and running them under water can be effective, but to also address the bacteria, give them a five to 10-minute soak in vinegar diluted with water. This should reduce the amount of bacteria on the surface of the root vegetable and therefore in your simple potato salad recipe.

When it's time to serve the meal, a metal bowl is ideal because it does the best job of retaining the cold temperature from the refrigerator. It also helps to nest it in another bigger container filled with ice. This method doesn't necessarily guarantee that your potato salad will stay at a steady, food-safe temperature for the whole time it's out, but it will certainly help spoilage from setting in prematurely. Just make sure not to leave it out longer than the USDA's recommended time limits.