Assessment of the Cronobacter sakazakii risk in reconstituted infant formula

The study focused on assessing Cronobacter sakazakii growth in reconstituted powdered infant formula at temperatures ranging from 5 °C to 48 °C using the Baranyi-Roberts model. The count of C. sakazakii was determined by the plate method on ESIA agar (44 °C, 24 h). Bacteria grew in reconstituted milk only at temperatures above 8 °C. The lag phase duration decreased with increasing temperature, from approximately 123.0–141.0 h at 8 °C to 0.931–1.281 h at 44 °C. The growth rate ranged from 0.025–0.027 ln cfu/ml/h (8 °C) to 2.441–2.633 ln cfu/ml/h (44 °C). The resulting growth models imply an increase of more than 4 orders of magnitude in the number of C. sakazakii in less than 17 h at 24 °C; at temperatures of 27 °C and above, the bacteria reach the critical concentration considered in our study (8 log cfu) in a few hours (4.5–11.9 h). In conclusion, it is unsafe and inappropriate to store reconstituted infant milk at temperatures higher than 8 °C.