Modelling the inactivation of dry-adapted Cronobacter sakazakii in infant formula during microwave heating

Cronobacter sakazakii is a widespread pathogen recognized as the primary agent for infection in infants due to contaminated powdered milk consumption. To support food safety during common domestic practices, a mathematical model was developed to predict the inactivation of C. sakazakii in reconstituted powdered infant formula (RPIF) during microwave heating. The thermal resistance of seven strains at 55 °C showed a wide range of D-values from 4.43 ± 0.12 min to 9.28 ± 3.39 min using non-selective plate count media, and from 2.58 ± 0.52 min to 6.04 ± 7.97 min using a selective one, demonstrating the presence of injured cells that could survive the treatment and be not visible in selective media usually used in food control system, causing the risk of over-estimate the lethality process. For model development, a dry-adapted (14 days at room temperature) -freeze-dried inoculum was prepared to contaminate the RPIF. A central composite design (CCD) was implemented to study the effect of volume (29.3-180.6 mL), power (80-920 W) and time (0.33-1.17 min) on C. sakazakii in RPIF during microwave heating. Then, the response surface methodology was implemented according to the generated model. The model, validated by twenty additional experiments within the CCD range, was considered to be within the acceptable range, with bias and accuracy factors of 1.09 and 1.60, respectively. The predictive model generated in this study can be an effective tool, improving guidelines and suggested practices for the heating and consumption of RPIF, especially considering sensitive consumers.