ARS | Publication request: The effect of potassium sorbate and pH on the growth of Listeria monocytogenes in ham salad

Submitted to: Journal of Food Processing and Preservation Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 2013
Publication Date: N/A

Interpretive Summary: Delicatessen salads are susceptible to Listeria monocytogenes contamination. The products receive no terminal heat treatment during manufacturing and are ready-to-eat without cooking. The ability of L. monocytogenes to grow at refrigerated temperature makes it a significant health hazard in salads. Potassium sorbate is a GRAS chemical preservative widely used in various food products. This study examined the effect of sorbate and salad pH on the growth of L. monocytogenes in a model ham salad. A mathematical model was developed to describe the increases in population of L. monocytogenes as affected by salad pH and sorbate. The model will assist salad producers in selecting levels of salad pH and sorbate for their products to reduce L. monocytogenes risk in mayonnaise-based salads.

Technical Abstract: This study examined and modeled the growth of Listeria monocytogenes in ham salads of various pHs and potassium sorbate concentrations. Minced ham was inoculated with L. monocytogenes and mixed with sorbate (0-0.2%) and mayonnaise to achieve salad pH ranging from 5.4 to 5.8. The population increases of L. monocytogenes in salads after 4 weeks of storage at 4 degrees Celsius were determined and correlated to salad pH and sorbate concentration. In salads with pHs of 5.4-5.8 containing 0, 0.1, 0.15 and 0.2% sorbate, the populations of L. monocytogenes increased 2.7-6.4, 2.4-5.2, 1.0-3.7 and 0.2-2.0 log cfu/g, respectively. A polynomial model was developed to describe the population increases as a function of salad pH and sorbate concentration. The model indicated that the increases of L. monocytogenes were significantly lower (p less than 0.05) in salads containing higher sorbate concentrations. Results from this study will help salad producers to identify the range of salad pH and sorbate levels that reduce the hazard of L. monocytogenes in mayonnaise-based salads.