Growth kinetic model developed for three common pathogenic bacteria in rehydrated infant milk formula

Objective To develop the kinetic model and study the growth parameters of listeria monocytogenes, enterobacter sakazakii and bacillus cereus in the rehydrated infant milk formula stored at different temperatures and time periods.Methods The three pathogenic bacteria were inoculated respectively in the rehydrated infant milk formula, and stored at 4℃,8℃, 25℃,37℃ and 42℃ separately for different periods of time. The numbers of bacteria colony were counted referring to national standards (GB 4789.2-2010). A modified Gompertz model and root square model were used to estimate the primary and secondary growth parameters of three pathogenic bacteria in the rehydrated infant milk formula. The validity of the model was further verified.Results Modified Gompertz model fitted well with the growth curves of three pathogenic bacteria in the rehydrated infant milk formula respectively, with the range of R² between 0.97 and 1.00. Good linear fitting was found between temperature and μ_max(R²:0.93-0.99) of the three pathogenic bacteria by using root square model. Further validation of the developed models indicated that the value of B_f and A_f were acceptable.Conclusion The primary and second growth kinetic models were developed for three bacteria respectively in the rehydrated infant milk formula. This study contributes to providing theoretical basis for the risk assessment and early warning of the three pathogenic bacteria in rehydrated infant milk formula.