Prediction of the staphylococcal enterotoxin A production in simulated Minas Frescal cheese conditions

This study aimed to develop a predictive model to investigate the effect of temperature, pH, NaCl concentration, initial inoculum concentration and time on enterotoxin A (SEA) production by <i>Staphylococcus aureus</i>. Combinations of three levels of temperature (10, 15 and 25°C ), five levels of pH (5.3, 5.5, 6.0, 6.5 and 6.7), five levels of NaCl (0.8, 1.0, 1.5, 2.0 and 2.2%), three levels of inoculum concentration (0, 3 and 5 log CFU/mL) in brain heart infusion (BHI) broth were studied. Colonies were counted and SEA production was assessed at 24 h intervals for up to 240 h. A probabilistic logistic regression model was used to describe the production of SEA by <i>Staphylococcus aureus</i>. SEA production was influenced by all factors, except NaCl concentration. <i>S. aureus</i> produced SEA in all samples at 25°C, while the temperature of 10°C delayed the growth and SEA production of <i>S. aureus</i> at initial contamination levels of 3 log CFU/mL and 5 log CFU/mL and prevented it at 0 log CFU/mL. The model was statistically and experimentally validated, demonstrating a good fit, with a high percentage agreement, Nagelkerke's R² and the Hosmer and Lemeshow test for the SEA production model. The experimental validation confirmed the effectiveness of the models for predicting the probability of SEA production by <i>S. aureus</i> in Minas Frescal cheese.