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Food Prep

The truth about mayonnaise and food safety

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Is mayo safe to eat if it's been left out? (iStock)

Of all the anxieties surrounding taking work to lunch—and there are plenty, from what to carry said lunch in, to making sure said lunch isn't stolen—perhaps none is as nagging as the anxiety around mayonnaise.

In short, people seem convinced that, if left at room temperature for even a short period of time, the mayonnaise on their sandwich will sprout all sorts of bacterial growths—growths that will cause illness, financial ruin, and all sorts of other tragedies.

Like so much other drama, it's unnecessary.

A seminal study from 2000 took a look at the fragility of mayonnaise and set the record straight: "Salmonella, E. coli O157:H7, E. coli, L. monocytogenes, Staphylococcus aureus, and Yersinia enterocolitica die when inoculated into mayonnaise and dressings."

To put it just as plainly, but in layman's terms, store-bought mayonnaise contains enough acid (from vinegar or lemon juice) to not only kill food-borne pathogens, but also to prevent them from forming.

What this means is that the angst around an egg salad sandwich—that is, the fear of letting the sandwich sit out for an hour or two at room temperature because the mayo might spoil—is actually backwards. 

If anything, the mayonnaise is preventing microbial growth. The eggs (and turkey, and sliced ham) would be more dangerous without it.

Get the real deal with mayo direct from food safety experts.

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