Purpose: The purpose of this study was to determine survival and growth characteristics of Salmonella and Listeria monocytogenesin mayonnaise-based deli salads and hummus as affected by sodium content.
Methods: Potato salad, macaroni salad, coleslaw and hummus (pH 5.07, 4.47, 3.94, and 4.59, respectively) were formulated to contain four concentrations of sodium: lowest (no sodium added), low (less than amount in control recipe), control (standard recipe) and highest (more than amount in control recipe). Test products were inoculated with Salmonella or L. monocytogenes. Populations of pathogens and total aerobic microorganisms were determined over a 27-day storage period at 4°C and 10°C.
Results: Populations of Salmonella (2.02 - 2.38 log CFU/g) decreased in coleslaw to undetectable levels (<1 CFU/25 g) within 13 days and in most formulations of macaroni salad within 20 - 27 days. Added sodium in macaroni salad stored at 4°C and hummus stored at 4 or 10°C appeared to protect Salmonella against inactivation. L. monocytogenes(1.86 - 2.23 log CFU/g) did not grow in test products but, with the exception of coleslaw containing sodium at a concentration used in the standard recipe, it was detected (> 1.0 log CFU/g) in all products stored at 4 or 10°C for 27 days. Sodium concentration did not significantly affect aerobic plate counts.
Significance: The acidic pH of deli salads and hummus is a major factor affecting viability of Salmonella and L. monocytogenes. In the absence of added sodium, death may be more rapid. Overall, however, the sodium content in selected deli salad and hummus recipes does not markedly affect the behavior of these pathogens.