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) re duced calorie mayonnaise dressing, and (iii) reduced calorie/reduced f at mayonnaise dressing. The salads were inoculated with 10(3)/ml level s 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 r efrigerated shelf-life limit and microbial spoilage profile of both sa lads. Salmonella spp. growth occurred in the temperature-abused chicke n salad, while L. monocytogenes grew in the temperature-abused and ref rigerated chicken salad. The synergistic combination of mayonnaise and refrigeration inhibited L monocytogenes outgrowth for >7 d. The micro biological shelf life of refrigerated chicken and pasta salads was 5 a nd 7 d, respectively. Microbial spoilage was predominantly caused by h eterofermentative lactic acid bacteria, of which Leuconostoc mesentero ides was the most important. The organism was psychotropic and exhibit ed competitive inhibition against Salmonella spp. The latter was attri buted to diacetyl formation synergistically interacting with the acidi c salad environment. No microbiological safety or spoilage differences were observed between the salads prepared with real mayonnaise or red uced calorie mayonnaise dressings. Under proper refrigeration and good hygienic practices, home-style salads made with commercial real mayon naise/mayonnaise dressings represent negligible microbial health hazar d risks to consumers.