Effects of Extended Dry Storage of Powdered Infant Milk Formula on Susceptibility of Enterobacter sakazakii to Hot Water and Ionizing Radiation

Authors: Osaili, Tareq M.1; Al-Nabulsi, Anas A.1; Shaker, Reyad R.1; Ayyash, Mutamed M.1; Olaimat, Amin N.1; Abu Al-Hasan, Ashraf S.1; Kadora, Khaled M.1; Holley, Richard A.2

Source: Journal of Food Protection®, Number 5, May 2008, pp. 886-1088 , pp. 934-939(6)

Publisher: International Association for Food Protection

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Infant milk formula has been identified as a potential source of Enterobacter sakazakii, which has been implicated in neonatal meningitis and necrotizing enterocolitis. This study was undertaken to determine whether the length of E. sakazakii storage in powdered infant milk formula (PIMF) affected the ability of the pathogen to survive subsequent reconstitution of the powder with hot water or treatment with gamma radiation. Five E. sakazakii strains were mixed individually with PIMF and kept for up to 12 months at 25°C. After storage PIMF was reconstituted with water at 60 to 100°C or was exposed to ≤5 kGy of gamma radiation. Without any treatment secondary to drying, E. sakazakii counts decreased <1 log/g after 1 month but decreased about 4 log/g during storage for 8 to 12 months. Dry storage decreased thermal resistance but increased resistance of E. sakazakii to ionizing radiation in PIMF. Reconstitution of contaminated powder with water at 70°C after 1 month of dry storage reduced E. sakazakii viability slightly, >2 log/g, and after powder was stored for 12 months all E. sakazakii strains were eliminated. In contrast, desiccation substantially increased the resistance of E. sakazakii strains to ionizing radiation. Although the D-value for E. sakazakii IMF1 following overnight storage in PIMF was 0.98 kGy, >4 kGy was required to kill 1.5 log/g of the same strain that had survived 12 months in dry PIMF. Results suggested that low-dose irradiation will more effectively eliminate E. sakazakii from PIMF if the treatment is applied shortly after PIMF manufacture.

Document Type: Research Article

Affiliations: 1: Department of Nutrition and Food Technology, Faculty of Agriculture, Jordan University of Science and Technology, P.O. Box (3030) Irbid, 22110, Jordan 2: Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2

Publication date: May 1, 2008

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    First published in 1937, the Journal of Food Protection®, is a refereed monthly publication. Each issue contains scientific research and authoritative review articles reporting on a variety of topics in food science pertaining to food safety and quality. The Journal is internationally recognized as the leading publication in the field of food microbiology with a readership exceeding 11,000 scientists from 70 countries. The Journal of Food Protection® is indexed in Index Medicus, Current Contents, BIOSIS, PubMed, Medline, and many others.

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