Mayonnaise's bad reputation

BURNING QUESTIONS

August 23, 2006|By ERICA MARCUS | ERICA MARCUS,Newsday

Why are mayonnaise salads so perishable?

Poor mayonnaise. It has a completely undeserved reputation as the food most likely to go bad.

But perishability is not the mayonnaise's fault, said Kathryn Boor, professor of food microbiology at Cornell University. Rather, it gets blamed because it is a common feature of many perishable foods.

The Food and Drug Administration's definition of mayonnaise requires that it be made from vegetable oil, egg and vinegar and/or lemon juice. Those last two ingredients not only provide an acidic tang, they also discourage microbial growth. Thus, commercial mayonnaise is considered a shelf-stable product and is stocked in a nonrefrigerated section of the market.

So where do these mayonnaise horror stories come from? As Cassius might have said to Brutus if the latter were considering making potato salad instead of assassinating Julius Caesar, "The fault lies not in our mayonnaise but in ourselves."

To make mayonnaise-based salad, ingredients with a neutral pH (potatoes, eggs) are added, making the mixture less acidic. More problematic, Boor said, is that the methods used to prepare the salad often are less than sterile.

Because they traditionally are eaten at outdoor events, mayonnaise-based salads often spend hours at room (or backyard or beach) temperature. This affords any nascent microorganisms the time to multiply.

The bottom line is: Be careful with your mayonnaise-based salads; just don't blame the mayonnaise.

I should add that the forgoing discussion applies only to commercially prepared mayonnaise. Homemade mayonnaise, an uncooked emulsion made from oil and raw egg yolks, is not shelf-stable, and its acidity depends on how much vinegar or lemon juice is added by the cook.

Erica Marcus writes for Newsday. E-mail your queries to burningquestions@newsday.com, or send them to Erica Marcus, Food/Part 2, Newsday, 235 Pinelawn Road, Melville, NY 11747-4250.

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