Purpose: This study examined the effect of potassium sorbate on the growth of L. monocytogenes in meat salad.
Methods: Ground ham was inoculated with a four-strain mixture of L. monocytogenes and mixed with mayonnaise containing potassium sorbate. The final pHs of salads were 5.4-5.8 and sorbate concentrations were 0-0.2%. Samples were stored at 4°C for up to 4 weeks, and the net increases of L. monocytogenes population in salads were determined.
Results: The initial level of L. monocytogenes in salads was 2.1 log CFU/g. Without sorbate, the net increases of L. monocytogenes in salads of pHs 5.4-5.8 were 2.7-6.4 log CFU/g. Addition of sorbate significantly reduced the growth of L. monocytogenes. The net increases were reduced to 2.4-5.2, 1.0-3.7, and 0.2-2.0 log CFU/g in salads containing 0.1, 0.15, and 0.2% sorbate, respectively. Generally, salads formulated with lower pHs and higher concentrations of sorbate had lower net increases of L. monocytogenes. A model was developed to correlate the population increase to salad pH and sorbate concentration. It suggests that the increases of L. monocytogenes population in salads would be < 1.0 log CFU/g if pHs are ≤ 5.6 with 0.2% sorbate and ≤ 2.0 log CFU/g if pHs are ≤ 5.4 with ≥ 0.13% sorbate, pH 5.5 with ≥ 0.15% sorbate, and pH 5.6 with ≥ 0.18% sorbate.
Significance: Findings from this study may be used by salad producers to formulate the salad pHs and sorbate levels that can reduce hazard associated with L. monocytogenes in mayonnaise-based salads.