Purpose: This study developed dynamic models to predict the fates of S. aureus in sauces and dressing.
Methods: S. aureus 5-strain mixture was inoculated in 5 g of Carbonara and octopus sauce at 3 log CFU/g, and oriental dressing, bean paste sauce, Katsuobushi sauce, low sodium soy sauce and Soba sauce at 7 log CFU/g. Carbonara and octopus sauces were stored at 10, 15, 20, 25 and 30 °C for 15 days, and they were analyzed for S. aureus growth, but the other sauces were analyzed at room temperature to estimate decreases in cell counts of S. aureus. Growth data of S. aureus for Carbonara and octopus sauces were fitted to the Baranyi model to calculate lag phage duration (LPD; day), maximum specific growth rate (µmax; log CFU/g/day) and upper asymptote (Nmax; log CFU/g). The parameters were then fitted to secondary models, and a dynamic model was also developed for changing temperatures. The developed model was validated using observed data, and bias (B) and accuracy (A) factors were calculated.
Results: Carbonara and octopus sauces had S. aureus growth at 10-30 °C and 15-30 °C, respectively, but the other sauces had significant S. aureus decrease (P < 0.05). The LPD and µmax of S. aureus in Carbonara and octopus sauces were 2.18-80.7 days and 0.02-0.45 log CFU/g/day, respectively, and S. aureus grew up to around 9 log CFU/g. R2 values of secondary models were 0.732-0.975. The goodness of fit for growth model was acceptable (A factor: 1.03-1.07; B factor: 0.99-1.06), and prediction of the dynamic model showed also acceptable performance.
Significance: The developed predictive models for Carbonara and octopus sauces should be useful in predicting S. aureus growth.