Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/9/2005
Publication Date: N/A
Technical Abstract: Deli salads have a relatively high incidence of contamination by Listeria monocytogenes. The objective of this study was to examine the behavior of this pathogen in ham salad and potato salad as affected by the pH of mayonnaise and storage temperature. Cooked ham and potato were inoculated with an 8-strain cocktail of L.monocytogenes, and mixed with mayonnaise adjusted to pH 3.8, 4.2, or 4.6. The cell counts of L. monocytogenes in salads during storage at 4°, 8°, or 12°C were used to model the behavior of L. monocytogenes in ham salad and potato salad. At each storage temperature, L. monocytogenes was able to grow in ham salad, but not in potato salad. The growth rates (GR) of L. monocytogenes in ham salad stored at 4°, 8°, and 12°C ranged from 0.0079 to 0.124, 0.0247 to 0.0339, and 0.0414 to 0.0458 log10 cfu/h, respectively. The GR of L. monocytogenes in potato salad stored at 4°, 8°, and 12°C ranged from -0.0115 to -0.210, -0.0138 to -0.0286, and -0.0265 to -0.0414 log10 cfu/h, respectively. A significant longer lag phase duration (LPD, h) of L. monocytogenes in both ham salad and potato salad was observed at lower storage temperatures. Mathematical models that described the GR and LPD of L. monocytogenes in ham salad or potato salad as a function of mayonnaise pH and storage temperature were produced. The models indicated that the GR and LPD of L. monocytogenes in ham salad and potato salad were mainly affected by the storage temperature.