Resistance of Cronobacter sakazakii in reconstituted powdered infant formula during ultrasound at controlled temperatures: A quantitative approach on microbial responses

Many of the documented outbreaks of Cronobacter sakazakii have been linked to infant formula. The aims of this work are to monitor the inactivation kinetics of C. sakazakii NCTC 08155 and ATCC 11467 and to determine quantitatively the effectiveness of ultrasonic treatments as an alternative to heat processing of reconstituted infant milk formula before feeding of infants at highest risk. Inactivation studies of C. sakazakii inoculated in reconstituted infant formula were performed at the combined conditions of temperature, i.e., 25 °C, 35 °C, 50 °C and amplitude, i.e., 24.4, 30.5, 42.7, 54.9, 61 μm and the kinetics were described by a range of inactivation models. The dependency of the specific inactivation rate with respect to the product of temperature and amplitude was described by a modified Bigelow type model. Ultrasound combined with temperature was efficient to reduce significantly the microbial levels of C. sakazakii. C. sakazakii strain NCTC 08155 was at the same range of temperature and amplitude resistance as strain ATCC 11467. Application of ultrasound is an alternative process for the production of safe reconstituted infant formula. This study contributes on the quantitative assessment of the resistance of C. sakazakii.