How long will mayonnaise keep unrefrigerated after opening and is it true that mayo does not have to be refrigerated?
According to "The Association for Dresses and Sauces,"
commercially available mayonnaise can be left out of the
refrigerator for a long time and still be safe. Apparently, the
eggs used in commercial mayo are pasteurized, killing bacteria like
Salmonella. Also, they say, commercial mayo is sufficiently acidic
to be unfavorable to bacteria that may be introduced after opening
the jar. I always assumed that Salmonella was the prime problem,
but if you think about it, mayo sits on store shelves
unrefrigerated for a long time, and there's no reason Salmonella
couldn't grow then. TADS also says the reason refrigeration is
recommended by the mayo jar is to preserve fresh taste.