Effects of the Reconstitution and Storage Conditions of Powdered Infant Formula (PIF) on the Survival and Growth of Enterobacter sakazakii

Abstract

The effect of the reconstruction and storage conditions of powdered infant formula (PIF) on the survival and growth of three Enterobacter sakazakii strains, ATCC 29004, HT 022 and HT 028, was investigated. D values of E. sakazakii ATCC 29004 and HT 022 at 60 degrees C were 3.6 and 1.6 min, respectively, and that of HT 028 at 52 degrees C was 1.6 min. The effect of the temperature of the water used for the reconstruction of PIF on the inactivation of the three E. sakazakii strains was also investigated. One to 2 log order inactivation occurred at 70 degrees C, and above 5 log order inactivation at 80 degrees C. Storage tests at 5, 10 and 25 degrees C showed that none of the strains could grow at 5 degrees C, HT 028 grew slightly at 10 degrees C, and at 25 degrees C all three strains started growth after 4 hr incubation and reached up to 8 log CFU/mL after 16 hr incubation. From the above results, it is concluded that a suitable temperature of the hot water for reconstruction of PIF is above 70 degrees C, and the preferred storage temperature of reconstructed PIF, which is recommended to be consumed within 2 hr, is below 5 degrees C.