Studies conducted nearly 30 years ago by Edwin M. Foster and his colleagues at the University of Wisconsin's Food Research Institute in Madison found that the high acid content of commercially prepared mayonnaise, not the variety made at home with fresh eggs, killed strains of salmonella and staphylococcus bacteria. The story adds that in the 1980s, Mike Doyle and his colleagues at the University of Georgia's Center for Food Safety and Quality found that the high acidity of commercial mayonnaise rendered it lethal to salmonella and Listeria. The bacteria failed to grow in either type of mayonnaise, the team reported in 1995 in the Journal of Applied Environmental Microbiology. Even when researchers raised temperatures by up to 10 degrees, the bacteria not only failed to grow but were also inactivated and reduced to undetectable levels within two days. The story says that recipes that use uncooked eggs are what tainted mayonnaise's reputation.
Raw eggs are a common source of salmonella.
An investigation showed that raw eggs had been used to make mayonnaise for patients on low-sodium diets. While most patients received commercially prepared mayonnaise, all batches of salad became contaminated by utensils that were used to mix the salads. Nine people died. But just because commercially prepared mayonnaise has a good track record for killing common bacteria does not mean that it can be used without taking the proper precautions.