THE FATE OF SALMONELLA TYPHIMURIUM AND STAPHYLOCOCCUS AUREUS IN COTTAGE CHEESE WHEY1

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Abstract
Cottage cheese whey was inoculated with Salmonella typhimurium and Staphylococcus aureus and stored for up to 9 days at 5, 25, and 35 C. Salmonellae could not be isolated from samples stored longer than 3 days when the inoculum provided 1.9 × 103 cells per milliliter or less. Staphylococci were more resistant to the adverse effect of pH than salmonellae. When the initial population was 1.0 × 105 cells per milliliter, salmonellae counts decreased 99.99% in one day at both 25 and 35 C. Under similar conditions, staphylococcal counts decreased about 90% at 25 C and 99% at 35 C during the first day of storage. Storage at 5 C had a very limited effect on the viability of staphylococci. The rapid inactivation of both pathogen at 25 C and 35 C could be explained primarily by the low pH (4.5 – 4.6) resulting from the presence of lactic acid.

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