Mayo is safe, really!
Now that Memorial Day is past and summer is officially here, the myth of unsafe mayonnaise is upon us. Any time you have an outdoor gathering in pleasant weather, someone is going to pucker up their face, make a tutting noise, and complain about the potato salad or egg salad being unsafe. Everyone always blames the mayonnaise, but it's just not true.
In fact, commercial mayonnaise is as shelf-stable as mustard. The manufacturers suggest that you refrigerate it, but this is only because it becomes visually unappealing if kept at room temperature for too long. (All you need to do is stir it up and it's fine to use, of course.)
Commercial mayonnaise is extremely acidic, thanks to the lemon juice and/or vinegar which has been added. Commercial mayonnaise also does not use raw egg - it is made with pasteurized eggs instead. In fact, mayo is so acidic that it actually makes the stuff in it safer. Egg salad dressed with mayonnaise will be safer to eat than plain old hard boiled eggs kept under the same conditions.
The mayonnaise myth almost certainly goes back to the days when mayonnaise was made by hand, with raw eggs. Even though its acidity still keeps it safer than raw eggs alone, homemade mayo should be more carefully refrigerated than the commercial stuff.
While our grandmothers should have taken care with their potato salad left out at a picnic all afternoon, this information is completely out of date for us today.
You should be far more concerned about the eggs, ham, and potatoes that get used in the salads themselves. Although mayonnaise will help slow the growth of harmful bacteria in these foods, mayonnaise is not a cure-all. The FDA still recommends that you follow the "two hour rule," meaning that everything at your cookout should only be left unrefrigerated for two hours before being put away.
Image courtesy Flickr/texascooking