High hydrostatic pressure treatment applied to model cheeses made from cow’s milk inoculated with Staphylococcus aureus

Pasteurized milk was inoculated with two strains of Staphylococcus aureus (CECT4013 or ATCC13565) and used to elaborate soft-curd cheeses with approximately 7.5-log CFU/g of S. aureus. Cheeses were submitted to 10 min high hydrostatic pressure (HHP) treatments of 300, 400 or 500 MPa at 5 °C or 20 °C. Staphylococcus enterotoxin (SE) was evaluated in cheeses containing ATCC13565. Counts of S. aureus were measured after HHP treatment (day 1) and after 2, 15 and 30 days ripening at 8 °C. Inactivation increased with pressure and storage time, but was similar for both treatment temperatures. Maximum S. aureus reductions were achieved after 30 days ripening for samples treated at 500 MPa and 5 °C: 6.0 ± 0.1 and 4.7 ± 0.5-log CFU/g for CECT4013 and ATCC13565, respectively. However, SE was detected in all cheese samples containing ATCC13565 before and after HHP and after 30 days ripening.