Viability of Salmonella and Listeria monocytogenes in Delicatessen Salads and Hummus as Affected by Sodium Content and Storage Temperature

Abstract

<jats:p>A study was conducted to determine survival and growth behavior of Salmonella and Listeria monocytogenes in commercially prepared mayonnaise-based potato salad, macaroni salad, and coleslaw and in hummus (initial mean pH values were 4.80 to 4.94, 4.18 to 4.31, 3.87, and 4.50 to 4.52, respectively) as affected by sodium concentration (133 to 364, 190 to 336, 146 to 272, and 264 to 728 mg/100 g, respectively) and storage at 4 or 10°C for up to 27 days. Salmonella did not grow in any of the test products. Initial populations (2.02 to 2.38 log CFU/g) decreased in coleslaw to undetectable levels (&amp;lt;1 CFU/25 g) within 13 days and in most formulations of macaroni salad within 20 to 27 days. Salmonella survived in highest numbers in potato salad and hummus. The presence of 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, at an initial population of 1.86 to 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 (control) recipe, this pathogen was detected by direct plating (≥1.0 log CFU/g) in all products stored at 4 or 10°C for 27 days. L. monocytogenes populations were significantly (P &amp;lt; 0.05) lower in potato salad and hummus with no added sodium than in test products with added sodium after storage at 4°C. Sodium concentration did not markedly affect aerobic plate counts over the 27-day storage period. Results confirm that the acidic pH of mayonnaise-based salads and hummus is a major factor preventing growth and influencing rates of inactivation of Salmonella and L. monocytogenes. In the absence of added sodium, death of these bacteria may be more rapid. However, in general decreasing or increasing the sodium concentration in selected delicatessen salad and hummus recipes does not markedly affect the behavior of Salmonella and L. monocytogenes when products are stored at 4 or 10°C for up to 27 days.</jats:p>

Survival and growth of Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus in eggplant dip during storage

“…Alali et al (2012) reported that background microflora numbers in salads and dips immediately after preparation were in the range of 2-3 log 10 CFU/g. Similarly, Omar et al (2012) reported APC and YM numbers of eggplant dip samples prepared in the laboratory to be 3 and 2.5 log 10 CFU/g, respectively.…”

“…After 7 d storage at this temperature, the pH values decreased in samples with 0, 0.4, 0.6 and 0.8% citric acid from 5.respectively. Previous studies on the effects of storage temperature and pH on the survival and growth of foodborne pathogens in salad/dip such as non-tahini-based eggplant salad and tahini-based products such as hummus dip (cooked, mashed chickpeas blended with tahini, lemon juice, garlic and salt) were found in the literature(Skandamis and Nychas, 2000;Tassou et al, 2009;Al-Holy et al 2006;Alali et al 2012). These studies also found that the survival and growth of foodborne pathogens in these products depended on intrinsic (e.g.…”

A Review of Temperature, pH, and Other Factors that Influence the Survival of Salmonella in Mayonnaise and Other Raw Egg Products

“…typhimurium growth was observed in the temperature range of 25–37 °C at pH 4.5 [48,49]. Alali et al [50] proposed that lowering the pH of the mayonnaise-based homemade salads decreased the rate of survival of Salmonella regardless of the temperature. According to a study conducted by Koutsoumanis et al [51], the minimum pH value that permitted the growth of S. typhimurium was 3.94 within the temperature range 25–35 °C.…”

“…Viability of Salmonella decreased as the amounts of vinegar and lemon juice in mayonnaise increased.[35]France S . typhimurium Reduced-calorie mayonnaisepH/TemperatureHigher temperature with a low pH, greater the inactivation of the organism.[78]U.S. Salmonella Mayonnaise-based potato salad, macaroni salad, and coleslawpH, NaCl, and temperatureDecreased pH and increased the bactericidal activity irrespective of sodium concentration or storage temperature Sodium concentrations had little or no effect on the behavior of Salmonella when stored at 4 or 10 °C for up to 27 days.[50]U.K. S. EnteritidisMayonnaisepH acetic acid (vinegar)Mayonnaise made with vinegar to a pH of 4.1 or less controlled S. Enteritidis. Storage of mayonnaise at refrigeration temperatures protected Salmonella spp.…”

The Effect of Potassium Sorbate and pH on the Growth of Listeria Monocytogenes in Ham Salad

“…Therefore, a lower salad pH may be needed to prevent the growth of L. monocytogenes in mayonnaise-based salads. For example, Alali et al (2012) reported that L. monocytogenes was not able to grow in commercially prepared mayonnaise-based potato salads of pHs 4.8-4.9, macaroni salads of pHs 4.2-4.9 and coleslaw of pH 4.5. Comparing the results (Table 1) with other studies reporting the growth of L. monocytogenes in cultural media under conditions similar to those found in mayonnaisebased salads, the present study showed that L. monocytogenes was more readily to grow in ham salads.…”