Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/17/2012
Publication Date: 9/1/2012
Citation: Fang, T., Gurtler, J., Huang, L. 2012. Growth kinetics and model comparison of cronobacter sakazakii in reconstituted powdered infant formula. Journal of Food Science. 77(9):247-255. Interpretive Summary: Cronobacter sakazakii is a life-threatening foodborne pathogen primarily associated with powdered infant formula (PIF), and can cause serious illnesses in neonates and infants. This study was conducted to develop mathematical models to predict the growth of this bacterium in reconstituted PIF. The results of this study can be used by the PIF industry and regulatory agencies for conducting risk assessments of reconstituted PIF exposed to various temperature abuse conditions, as well as for parents and other caretakers to properly store left-over reconstituted PIF.
Technical Abstract: Cronobacter sakazakii is a life-threatening bacterium, primarily implicated in illnesses associated with the consumption of powdered infant formula (PIF). It can cause rare but invasive infections, leading to sepsis, meningitis, or necrotizing enterocolitis in infants fed with contaminated PIF. The objective of this research was to investigate the growth kinetics of C. sakazakii in reconstituted PIF (RPIF) and to develop mathematical models to predict its growth. RPIF, inoculated with a 6-strain cocktail, non-heat-treated or heat-injured, was incubated isothermally at different temperatures to develop growth models. Except at 6 C, C. sakazakii grew well at all test temperatures between 10 and 48 C. C. sakazakii unexposed to thermal treatments did not exhibit noticeable lag phases, while a lag phase was observed in heat-treated cells. For non-heat-treated C. sakazakii, a simple three-parameter logistic equation was used to fit growth curves. For heat-treated C. sakazakii, both Baranyi and Huang models were suitable for describing the isothermal bacterial growth. The minimum and maximum growth temperatures were 6.5 and 51.4 C for non-heat-treated cells, and 6.9 and 50.1 C for heat-treated cells of C. sakazakii in RPIF, respectively. There was no significant difference between the growth rates of non-heat-treated and heat-injured cells in RPIF. For heat-treated cells of C. sakazakii, the lag phase was temperature dependent, and was very short (i.e., between 25 – 48 C). This observation suggests that both non-heat-treated and the heat-injured C. sakazakii in RPIF may present a risk to infants if the bacteria are not completely destroyed by heat and then exposed to subsequent temperature abuse.