A lot of us already know that, on its own, commercial mayonnaise poses no threat of food poisoning when kept at room temperature (although it may get a funky flavor you probably want to avoid). But when mayo, a perfectly good kid in his own right, starts hanging out with troublemakers (cross-contaminated or low-acid foods), the likelihood that he will toilet-paper your house (cause food poisoning) is pretty high. And even if you’re proud of your remodeled bathroom, you probably want to avoid sending friends and family to get a nice close look at it after they try your famous potato salad at the Fourth of July barbecue.
So how long are mayo-based salads safe to serve at room temperature? Between one to two hours, according to the folks at StateFoodSafety.com. It takes roughly two hours for bacteria in foods to grow to dangerous levels, which is why you want to minimize the amount of time food is in the temperature danger zone (between 41 degrees and 135 degrees Fahrenheit). On days that are 90 degrees Fahrenheit or warmer, that time shrinks to one hour.
Food safety specialist Angela M. Fraser suggests keeping food in an ice-packed cooler until the moment you serve it, and then putting it back in the cooler immediately after lunch. If it sits out for longer than an hour, your best bet is to throw away the leftovers. And if the ice melts in the cooler? Yup, throw that food away—cold water does not prevent mayo-based salads from becoming contaminated the way ice does. Down with food poisoning, up with safe and delicious barbecues!