Modeling the growth and dynamics of uropathogenic Escherichia coli in sugarcane juice for shelf life predictions

Abstract

In this study, we assessed the effects of temperature and dilution on uropathogenic Escherichia coli (UPEC) growth in sugarcane juice and modeled the kinetics for shelf life simulation. Diluted and undiluted sugarcane juice samples inoculated with a four-strain UPEC cocktail were stored at 4, 10, 15, 20, 30, and 40 °C to evaluate their growth during storage. Changes in UPEC growth were fitted using three primary models (Baranyi, Huang, and reparameterized Gompertz models), and two secondary models (Huang square-root and Ratkowsky square-root models) were selected to evaluate the effect of temperature on specific growth rates. The best-fitted models (reparameterized Gompertz and Huang square-root models) were validated by an additional experiment under isothermal storage (35 °C). Combining differential forms of the Baranyi model, the prediction performances of these models were further validated under storage at dynamic temperature profiles (15 to 37 °C in 4-h cycles). Results revealed that UPEC growth was observed in diluted and undiluted juice samples at storage temperatures of 15 to 40 °C. No growth of UPEC was found in either type of juice at storage temperatures below 10 °C. The estimated minimum growth temperatures (T_min) of UPEC in sugarcane juice and diluted juice were 10.7 and 11.2 °C, respectively. Validation results showed that the model perfectly estimated UPEC growth under isothermal conditions in both types of sugarcane juice (proportion of prediction error (pPE) = 1.00). Predictions of dynamic conditions in sugarcane juice (pPE = 0.73) and diluted juice (pPE = 0.91) were acceptable, at pPE > 0.7. Using the model, shelf life charts were derived based on the time to reach a certain microbial concentration. In conclusion, these results together with shelf life charts provide valuable information for the food industry to enhance sugarcane juice safety.