The big story in Rochester today – the one they’ll be laughing at for the next 24 hours, at least – is the hapless trio of thieves in Mount Morris who busted into a Build-a-Burger and stole.. mac salad. Lots of other stuff, too, but the comical vision of three guys who according to reports, “took turns eating along their escape route,” is just too much to resist. And so I won’t.
I thought I’d write up a quick article about how and why mayonnaise spoils and what you could do to prevent it. You know, in case you have any food service larceny in mind. But to my surprise, there are actually several sources online vehemently denying the myth of bad mayo. It turns out that this is actually a vestigial belief from the days of homemade mayo.

Tell me more, man.
So, does mayo spoil?
All things organic return to the Earth. But the idea that mayo is riddled with death-dealing parasites doesn’t really square with the reality of prepackaged foods that sit on a grocer’s shelves for a year. Things have changed.
It seems that the idea of mayo gone bad comes to us from the use of unpasturized eggs in homes back when that was the cheaper solution. Nasties could get into the eggs before you made the mayo and thus, with incautious mixing, would end up colonizing your stomach. Hence dad turns into an upside-down chocolate fountain right after the church brunch.
But modern mayos are so larded down with preservatives and vinegar that anything that might have been alive in the eggs would soon meet it’s doom in the final product. Besides that, the eggs are always pasturized to be sure there aren’t any nasty things growing in the first place.
Most of the time, if your mac salad went bad, it was probably the unpasturized eggs you boiled and cut up in the salad. Or maybe just a mix up with your cookware – did you use that knife to cut chicken? where did that spoon come from? – rather than the mayo itself.
Mind you: if your mayo says “bottled in China,” I’d bring a roll of toilet paper with me everywhere I go for the next twenty four hours. Better safe than soggy. But our Mt. Morris thieves have only the law to fear in the next few days. Running around Mt. Morris with three guys, a bowl full of mac salad and only one spoon may be dumb as shit. But it’s not life-threatening.