Factors affecting staphylococcal enterotoxin Cbovine production in milk

The effect of different combinations of temperature and pH on production of enterotoxin C (SEC) by Staphylococcus aureus was studied. Batch cultures of 10% sterile reconstituted skim milk were inoculated with about log 4.5 cfu mL−1S. aureus and grown for up to 66 h. A full factorial experiment of 4 temperatures and 4 pH values was undertaken. Cultures were also grown at fixed temperatures and uncontrolled pH, and in pasteurised and unpasteurised milk. The optimum controlled conditions for SEC production were 37 °C/pH6.5. At temperatures of 25, 30, 37 and 40 °C with uncontrolled pH, a lower concentration of SEC was produced compared with the controlled pH conditions. In pasteurised and unpasteurised milk, no SEC production occurred at temperatures up to 30 °C after 72 h. These studies contribute to risk assessment with regard to SEC production in milk and in cheese made from unpasteurised milk.