Growth and Enterotoxin Production by Staphylococcus aureus in Whey from the Manufacture of Domiati Cheese

Abstract

Staphylococcus aureus able to produce enterotoxin A was inoculated into Domiati cheese whey treated four different ways. Included were raw and pasteurized whey with 15% salt and unsalted raw and pasteurized whey. All wheys and their controls were kept at 30°C, and tested after 6, 12, 24, 48 and 72 h. There was a substantial loss in viability of S. aureus after 6 h of incubation in unsalted raw whey. Substantial loss of viability by S. aureus occurred in unsalted heat-treated whey after 24 h of incubation. S. aureus decreased in number slowly after 24 and 48 h of incubation in both salted raw and salted pasteurized whey. Thermonuclease and enterotoxin A were detected in unsalted heat-treated whey at and after 24 h when the number of S. aureus was 1.6 × 108/ml. Thermonuclease could not be detected after 6 h of incubation of unsalted or salted raw whey and after 48 h of incubation of salted whey.