Predictive modeling of Staphylococcus aureus growth and enterotoxin production in chicken cuts

Staphylococcus aureus is a major foodborne pathogen capable of producing heat-stable enterotoxins. In Brazil, the risk it poses in chicken slaughterhouses has been classified as moderate, raising concern since chicken products are often processed at ≤12 °C and toxin production has been reported at 10 °C. We developed predictive microbiology models to assess S. aureus growth and evaluate enterotoxin production in chicken whole leg boneless, skin-on, half breast skinless, without inner fillet, and mechanically separated meat (MSM) exposed to 7-46 °C. Growth curves were used to build primary and secondary predictive models based on the Baranyi & Roberts (1994), and toxin detection was performed in samples presenting ≥4 Log CFU/g. At 15 °C, populations reached 5.0-6.5 Log CFU/g depending on product; at 25 °C, rapid growth to 6-8 Log CFU/g occurred within 24 h without toxin production. No growth occurred at 7 °C to 72 h in MSM, and a slight growth was observed in periods not commonly found in slaughterhouses for half chicken breast and chicken whole leg. At 10 °C, growth patterns varied among products: while no growth occurred in MSM, half chicken breast and chicken whole leg increased 1.5 and 0.9 Log CFU/g, respectively. At 15 °C, populations reached 5.0-6.5 Log CFU/g depending on product; at 25 °C, rapid growth to 6-8 Log CFU/g occurred within 24 h without toxin production. At 37 °C, enterotoxins were detected in MSM and breast after 8-13 h when populations exceeded 6.5-8.0 Log CFU/g. Counts declined sharply at 46 °C. Models showed high accuracy (R², RMSE, Bf, Af) and enabled estimation of μmax, lag phase, and maximum density. Simulated industrial scenarios demonstrated non-negligible growth (>0.5 Log CFU/g) after at least 37 h at 10 °C, 12 h at 12 °C, 8 h at 15 °C, 6 h at 20, and 3.5 h at 25 °C. These findings indicate a low possibility of S. aureus multiplication and enterotoxin production in the chicken products tested when processed under proper slaughterhouse conditions.