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KMID : 0545120070170020364
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Journal of Microbiology and Biotechnology
2007 Volume.17 No. 2 p.364 ~ p.368
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Thermal Resistance and Inactivation of E. sakazakii Isolates During Rehydration of Powdered Infant Formula
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Kim Soo-Hwan
Park Jong-Hyun
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Abstract
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Enterobacter sakazakii may be related to outbreaks of meningitis, septicemia, and necrotizing enterocolitis, mainly in neonates. To reduce the risk of E. sakazakii in baby foods, thermal characteristics for Korean E. sakazakii isolates were determined at 52, 56, and 60oC in saline solution, rehydrated powdered infant formula, and dried baby food. In saline solution, their D-values were 12-16, 3-5, and 0.9-1 min for each temperature. D-values increased to 16-20, 4-5, and 2-4 min in rehydrated infant formula and 14-17, 5-6, and 2-3 min in dried baby food. The overall calculated z-value was 6-8 for saline and 8-10 for powdered infant formula, and 9-11 for dried baby food. Thermal inactivation of E. sakazakii during rehydration of powdered infant formula was investigated by viable counts. Inactivation of cultured E. sakazakii in infant formula milk did not occur for 20 min at room temperature after rehydration with the water at 50oC and their counts were reduced by about 1-2 log CFU/g at 60oC and 4-6 log CFU/ml with the water at 65 and 70oC. However, the thermostability of adapted E. sakazakii to the powdered infant formula increased more than two times. Considering that the levels of E. sakzakii observed in powdered infant formula have generally been 1 CFU/100 g of dry formula or less, contamination with E. sakazakii can be reduced or eliminated by rehydrating water with at least 10oC higher temperature than the manufacturer-recommended 50oC
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KEYWORD
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Enterobacter sakazakii, powdered infant formula, D-value, thermal inactivation, rehydration
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