Tuesday, July 24, 2012
Exhibit Hall (Rhode Island Convention Center)
Introduction: Cutting boards are considered as a vehicle of foodborne pathogens to contaminate meat, and Salmonella is one of the primary foodborne pathogens in meat processing.
Purpose: This study developed models to predict growth probabilities and kinetic behavior of Salmonella on the cutting boards.
Methods: Polyethylene coupons (3 x 5 cm) were inoculated with Salmonella (5-strain mixture). These coupons were then stored at 13, 15, 20, 25, 28, 30, 33 and 35°C for 12 h, and total bacterial and Salmonella cell counts were enumerated on tryptic soy agar and xylose lysine deoxycholate agar, respectively, every 2 h. The 0.5 log CFU/cm2 was used as a threshold to determine growth or no growth for 56 combinations (temperature (8) ¡¿ time (7)). These growth response data were analyzed by the logistic regression to develop the model predicting growth/no growth interfaces of Salmonella. In addition, cell counts of Salmonella were fitted to the modified Gompertz model to calculate growth rate (µmax; log CFU/cm2/h), log phage duration (LPD; h), and upper asymptote (Nmax; log CFU/cm2), following secondary modeling with the square root function. The model performances were validated with observed data.
Results: Total bacteria and Salmonella growth were observed only at more than 25°C and 28°C, respectively. However, cell counts of total bacteria and Salmonella on cutting board decreased (P < 0.05) at less than 20 and 25°C, respectively. Growth/no growth interfaces were produced at 0.1, 0.5, and 0.9 of probabilities with acceptable performance (concordance: 93.7 %, disconcordance: 5.6%). In kinetic model, µmax increased as growth temperature increased, but LPD and Nmax were similar among growth temperatures (28-35 °C). The prediction of the model was also acceptable (Bias factor: 1.03, Accuracy factor: 1.15).
Significance: The result suggests that developed models in this study may be useful in predicting growth/no growth interface and kinetic behavior of Salmonella on polyethylene cutting board.
Purpose: This study developed models to predict growth probabilities and kinetic behavior of Salmonella on the cutting boards.
Methods: Polyethylene coupons (3 x 5 cm) were inoculated with Salmonella (5-strain mixture). These coupons were then stored at 13, 15, 20, 25, 28, 30, 33 and 35°C for 12 h, and total bacterial and Salmonella cell counts were enumerated on tryptic soy agar and xylose lysine deoxycholate agar, respectively, every 2 h. The 0.5 log CFU/cm2 was used as a threshold to determine growth or no growth for 56 combinations (temperature (8) ¡¿ time (7)). These growth response data were analyzed by the logistic regression to develop the model predicting growth/no growth interfaces of Salmonella. In addition, cell counts of Salmonella were fitted to the modified Gompertz model to calculate growth rate (µmax; log CFU/cm2/h), log phage duration (LPD; h), and upper asymptote (Nmax; log CFU/cm2), following secondary modeling with the square root function. The model performances were validated with observed data.
Results: Total bacteria and Salmonella growth were observed only at more than 25°C and 28°C, respectively. However, cell counts of total bacteria and Salmonella on cutting board decreased (P < 0.05) at less than 20 and 25°C, respectively. Growth/no growth interfaces were produced at 0.1, 0.5, and 0.9 of probabilities with acceptable performance (concordance: 93.7 %, disconcordance: 5.6%). In kinetic model, µmax increased as growth temperature increased, but LPD and Nmax were similar among growth temperatures (28-35 °C). The prediction of the model was also acceptable (Bias factor: 1.03, Accuracy factor: 1.15).
Significance: The result suggests that developed models in this study may be useful in predicting growth/no growth interface and kinetic behavior of Salmonella on polyethylene cutting board.