Purpose: The objective of this study was to develop mathematical models for prediction of the growth of S. aureus in salad dressing sauce, leading to the development of effective control methods for S. aureus.
Methods: A five-strain mixture (S. aureus ATCC14458, 27664, 23235, 13565 and 19095) was inoculated in 250 g of salad dressing sauce at 2 log CFU/g. The inoculated samples were then exposed to 10, 20, 25 and 35°C, and growth of S. aureus were enumerated on Baird Parker agar for 720 h. Moreover, growth data of S. aureus were fitted to the Gompertz and Polynomial model to calculate specific growth rates (SGR) and lag time (LT).
Results: The growth rate data fit well with the Gompertz and Polynomial equation model, evidencing a high degree of goodness of fit (R2 = 0.9472 to 0.9945) for all temperatures. Temperature also exerted a significant effect on both the SGR and LT. As storage temperature increased, the SGR increased markedly and the LT decreased. The results of R2, Bf, and Af which were different statistical indices for the SGR and LT of S. aureus in salad dressing sauce were 0.9825, 1.17, 1.27 and 0.9765, 0.94, 1.16, respectively. The higher r2 (0<r2<1) values resulted in more accurate model predictions.
Significance: The predictive model of S. aureus in salad dressing sauce is expected to provide risk managers and consumers with important risk information regarding the shelf life and appropriate storage condition.