FATE OF SALMONELLA SPP, LISTERIA-MONOCYTOGENES, AND INDIGENOUS SPOILAGE MICROORGANISMS IN HOME-STYLE SALADS PREPARED WITH COMMERCIAL REAL MAYONNAISE OR REDUCED CALORIE MAYONNAISE DRESSINGS

Two home-style salads, chicken and macaroni, were prepared with three different commercial mayonnaise products: (i) real mayonnaise, (ii) reduced calorie mayonnaise dressing, and (iii) reduced calorie/reduced fat mayonnaise dressing. The salads were inoculated with 10(3)/ml levels of Salmonella spp. or Listeria monocytogenes and held at 4-degrees-C (refrigeration) and 12.8-degree-C (temperature abuse) for 10 and 2 d, respectively. Uninoculated controls were evaluated to determine the refrigerated shelf-life limit and microbial spoilage profile of both salads. Salmonella spp. growth occurred in the temperature-abused chicken salad, while L. monocytogenes grew in the temperature-abused and refrigerated chicken salad. The synergistic combination of mayonnaise and refrigeration inhibited L monocytogenes outgrowth for >7 d. The microbiological shelf life of refrigerated chicken and pasta salads was 5 and 7 d, respectively. Microbial spoilage was predominantly caused by heterofermentative lactic acid bacteria, of which Leuconostoc mesenteroides was the most important. The organism was psychotropic and exhibited competitive inhibition against Salmonella spp. The latter was attributed to diacetyl formation synergistically interacting with the acidic salad environment. No microbiological safety or spoilage differences were observed between the salads prepared with real mayonnaise or reduced calorie mayonnaise dressings. Under proper refrigeration and good hygienic practices, home-style salads made with commercial real mayonnaise/mayonnaise dressings represent negligible microbial health hazard risks to consumers.