Behavior of Listeria monocytogenes and Salmonella heidelberg in Rennet Whey Containing Added Sodium and/or Potassium...

The behavior of Listeria monocytogenes and Salmonella heidelberg in rennet whey salted with sodium chloride, potassium chloride, or a 55/45 mixture of these two salts was evaluated. Other variables included initial whey pH, 4.8 or 5.6, percent salt in moisture (S/M), 3.6 or 4.8, and the addition or omission of lactic culture. Inoculated whey samples were incubated at 4°C for 14 d ( L. monocytogenes only) or 25°C for 5 d. At 4°C, populations of L. monocytogenes remained static in whey at pH 4.8 and increased slowly in whey at pH 5.6 whether or not lactic culture had been added. At 25°C, with no lactic culture added, populations of both L. monocytogenes and S. heidelberg increased rapidly, more rapidly at pH 5.6 than at pH 4.8. Populations of both organisms decreased when lactic culture was added. Numbers of S. Heidelberg decreased more in unsalted (control) than in salted wheys. Populations of S. heidelberg were slightly lower in wheys salted to S/M 4.8 than in wheys salted to S/M 3.6. There were no indications that behavior of either L. monocytogenes or S. heidelberg correlated with the type of salt utilized. Sodium and potassium chlorides appear to function interchangeably in simulated cheese safety systems.