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Apr 14, 2002 01:55 PM

Is mayonaise *really* dangerous if left out?

  • h

With summer approaching, we're sure to start hearing those warnings about the dangers of leaving potato salad (et al) out, because (allegedly) the mayo in those salads can easily go bad--presumably because the egg yolk in mayo is a nice growth medium for nasty little buggies.

But is that true? I don't think I've *ever* had mayonaise go bad because of microbial infestation. In fact, I've had some mayo in a fridge for as long as two *years* and it didn't go bad--and that's about the only food I can think of that has not gone bad!

My guess is that it's really the potatoes or the pasta or whatever that go bad, not the mayo.

Does anyone here have any *definitive* information on this, such as a reference to some paper in a food science journal, some experiment done by CDC or some other group, etc? I vaguely recall hearing some years ago that this rumor had been debunked, but I'm not entirely sure. Does anyone have any info?

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  1. Not exactly the NIH, but according to the Hellman's website, because of the acidity of mayonnaise, it can actually retard the growth of food bacteria.

    Scroll down on the Q & A page a little way and see what they have to say.


    1 Reply
    1. re: Pat Hammond

      I lived in Mexico for two years in an area where few people had refrigerators in their homes. You'd be surprised what can remain unrefrigerated and still be fine. I had jars of mayonaise in a pantry for months (like 10)without going bad. Eggs for weeks, butter and milk (in a box) for days. This was in the mountains where it was usually pretty cool, in hotter places it might be different.
      Leaving the first world does wonders for changing your perception about what is safe and unsafe (foodwise and otherwise).

    2. For those who still use homemade mayo, the answer is to treat it with all due caution as is can become a host for the nasties and make people ill. Keep it refrigerated. I believe the rule of thumb is that pregnant women, the elderly, or those with an immune compromised system should avoid it.

      Commercial mayo probably has been processed especially to limit the chances of becoming a host if only to reduce the companies' liability. Maybe someone out there has a link to some government site with a definitive answer.

      1. w
        Wendy Leonard

        My understanding is that commercial mayonnaise really doesn't spoil and that the warnings and scare stories predate the ubiquitousness of commercial mayonnaise. I do make my own mayonnaise--but I don't use it for kids school lunches, picnics, etc.--any situation where the food will be unrefrigerated for a length of time.

        1. mayonaisse is also a lot of oil, which goes rancid. its ok if you keep it cold because bacteria (in general for the kitchen kind) don't like to be alive in the refer. On the table, especially the picnic table in the sun, is a nice warm environment, which they LOVE.
          However, if you feel compelled to eat a mayo product that has been out a while, feel free, but do not DO NOT try to feed such items to a child or a very old person or anyone who doesn't know that the stuff's been out for more than, i'd say 1/2 hour, 45 minutes for my own taste.

          1. This is from a transcript of Alton Brown's Good Eats show on making mayo:

            "...Now I usually cover my fresh mayo and leave it at room temperature for 4 to 8 hours. [camera does a double-take on the jar] Now take it easy. Take it easy. I know. Leaving raw eggs in this zone sounds like crazy talk. But here's the thing. There's a small, tiny, infinitesimal, little chance that, uh, that egg yolk was contaminated with salmonella. Now the cold of the refrigerator would prevent that salmonella from breeding but it will not actually kill it. Acid, on the hand, will. And with a pH of, wow, 3.6 this is a decidedly acidic environment. But for reasons that still have lab-coaters scratching their heads, acid does its best bug killing at room temperature. So leaving this out for 8, 10, even 12 hours is sound sanitation. After that, straight to the refrigerator for no more than a week. You can even put it in the door."