Direct application of supercritical carbon dioxide for the reduction of Cronobacter spp. (Enterobacter sakazakii) in end products of dehydrated powdered infant formula

The objective of this study was to develop a viable new method for inactivation of Cronobacter spp. that could be applied directly to dehydrated powdered infant formula (PIF) using supercritical carbon dioxide (SC-CO(2)). Samples inoculated with Cronobacter spp. were subjected to SC-CO(2) treatment under various conditions (temperature: 63, 68, and 73 degrees C; pressure: 15, 20, and 25 MPa; time: 10, 20, and 30 min). The survival of Cronobacter spp. was assayed, as were any changes in the quality of the treated PIF. Inactivation of Cronobacter spp. by SC-CO(2) was enhanced as temperature and pressure conditions increased (>6.32 log(10) cfu/g). In a validation assay using low-level inoculation (3.21 log(10) cfu/g), treatment at 73 degrees C and 15 MPa for 30 min, 20 MPa for 20 and 30 min, or 25 MPa for 20 and 30 min reduced Cronobacter spp. to undetectable levels, with no recovery of cell viability. There was no significant change in water activity, pH, and color of the treated PIF. Overall, the optimum conditions for elimination of Cronobacter spp. were determined to be 73 degrees C and 20 MPa for 20 min. These parameters for effective SC-CO(2) treatment are feasibly applicable to end product of dehydrated PIF. The results of our study may contribute to the development of an efficient method for improving the microbiological safety of PIF.