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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Microbial and Chemical Food Safety » Research » Publications at this Location » Publication #193951


item Hwang, Cheng An

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/3/2006
Publication Date: 6/24/2006
Citation: Hwang, C. 2006. The fate of listeria monocytogenes in deli salads . Abstract. #105-03.

Interpretive Summary:

Technical Abstract: Deli salads are a popular ready-to-eat food in the market place. They generally contain one main food component, e.g., ham, chicken, shrimp or potato, and mayonnaise or salad dressing. If not prepared and handled properly, deli salads are susceptible to contamination by L. monocytogenes, and could pose a health risk to consumers. This presentation discusses studies investigating the fate of L. monocytogenes in seafood, ham, potato, egg, and pasta salads during storage. The food components were inoculated with L. monocytogenes, and mixed with mayonnaise (pH 3.8-5.0), and the resulting salads were stored at refrigerated and abuse temperatures (8 deg and 12 deg C). L. monocytogenes was able to grow in all salads, except potato salad, regardless of the pH of mayonnaise or storage temperature. In salads that supported growth, the growth was affected mainly by the storage temperature; slower growth at lower storage temperatures. While L. monocytogenes grew slowest in salads formulated with mayonnaise of pH 3.8 and stored at 4 deg C, its growth was not significantly affected by the mayonnaise pH at 8 deg or 12 deg C. The growth of L. monocytogenes was more rapid in meat- or egg-containing salads than in pasta- or potato-containing salads. This suggests that the food component is also a factor that affects the growth of L. monocytogenes in deli salads. Results indicate that once L. monocytogenes contaminates food components, it is able to grow in deli salads despite the adding of low-pH mayonnaise. Therefore, it is essential to ensure that food components used for deli salads preparation be handled properly to avoid L. monocytogenes contamination, and that finished products be kept at refrigerated temperatures. Growth data from these studies were developed into mathematical models to describe the lag phase durations and growth rates of L. monocytogenes in salads as affected by the mayonnaise pH and storage temperature.