Take some mayo, put it in a cup and let it sit out for a few hours and then look at it.. it’s nasty looking. Heat really messes with Mayo. We keep ours on ice. Since we left the South, we have been reduced to using mayos other than my preferred Duke’s Mayo (it’s sugar free unlike every other brand I have found). Dukes does go bad (I left a small jar in the refrigerator of the popup with no power one week…. ick!). I really don’t know about the other brands. We go thru it by the quart. Jar lasts a month or less (I use it too). I have found it is best to keep mayo, and mayo based condiments, cold (not freezing) and limit the amount of air that gets to it.