Growth and Survival of Staphylococcus aureus in Egyptian Domiati Cheese

Abstract

Domiati cheese was prepared from unsalted raw milk and from raw milk with 5 or 10% added sodium chloride, Milks were inoculated with enterotoxigenic Staphylococcus aureus strain 100 (produces enterotoxin A) before addition of salt and rennet. Cheeses were stored in whey containing 15% sodium chloride; were held at 30°C and were examined periodically for S. aureus count, aerobic plate count, DNase and moisture and salt contents. Numbers of S. aureus increased rapidly during preparation of cheese. There was a rapid decrease in number of viable S. aureus during storage of cheese made from unsalted milk and cheese made from milk with 5% added salt. In cheese from milk with 10% added salt, S. aureus survived until the fourth week. An increase in salt content and a decrease in the pH value of all cheeses occurred during storage in salted whey. DNase was detected only in cheese made from salted milk, but these samples did not contain a detectable amount of staphylococcal enterotoxin either after cheeses were made or after they were stored for 1 week.

Unveiling Staphylococcus aureus enterotoxin production in dairy products: a review of recent advances to face new challenges

“…Then, the population of S. aureus decreased to the initial level of contamination after 75 days at a rate depending on salt concentration, starter activity and storage time. Conversely, in Domiati cheese, the presence of a high salt concentration (10% of sodium chloride) was advantageous to the growth of S. aureus when competing with LAB (Ahmed et al 1983). In Camero cheese, Olarte et al (2000) reported that the growth of S. aureus was higher in batches without starter, but they did not detect any SE.…”

Microbiological quality of white‐brined cheeses: a review

“… 69 However, it has been reported that increasing the amount of salt in the milk used for the manufacture of domiati cheese enhanced the survival of S. aureus in the cheese; this effect was probably due to the inhibition of the LAB by the high salt content. 70 …”

Microbiological Quality of Domiati Cheese and the Influence of Probiotics on the Behavior of Staphylococcus aureus and Escherichia coli O157:H7 in Domiati Cheese

“…However, challenge studies have revealed that S. aureus and E. coli O157:H7 can survive the processing conditions used for a variety of cheeses, including domiati cheese (Ahmed et al . ; Nunez et al . ; Maher et al .…”