Magnetized Carbonyl Iron and Insoluble Zirconium Hydroxide Mixture Facilitates Bacterial Concentration and Separation from Nonfat Dry Milk

Authors: Cullison M.A.1; Jaykus L-A.2

Source: Journal of Food Protection®, Volume 65, Number 11, 1 November 2002 , pp. 1806-1810(5)

Publisher: International Association for Food Protection

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Abstract:

A mixture of magnetized carbonyl iron and insoluble zirconium hydroxide was investigated for its ability to concentrate various foodborne pathogens from 25-ml samples of reconstituted nonfat dry milk. Each sample was artificially contaminated with 103 to 106 CFU/25 ml of representative foodborne pathogens (Salmonella enterica serovar Enteritidis, Listeria monocytogenes, and Bacillus cereus spores) and processed for bacterial concentration with high-speed centrifugation for the primary concentration followed by a secondary concentration step involving the carbonyl iron-zirconium hydroxide mixture. Bacterial recoveries, as evaluated on the basis of loss to discarded supernatants, exceeded 75% for all organisms at all inoculum levels and were usually >90%. Recovery was confirmed by direct plating of the immobilized pellet, for which the values were similar albeit more varied. Additional experiments confirmed that the magnetized carbonyl iron-insoluble zirconium hydroxide mixture was relatively nontoxic to both Salmonella Enteritidis and L. monocytogenes. Overall, the entire concentration scheme resulted in a 25-fold reduction in sample volume with the recovery of viable bacterial cells. This novel compound shows promise for facilitating inexpensive, rapid, and effective bacterial concentration in food systems.

Document Type: Research article

Affiliations: 1: Department of Food Science, College of Agriculture and Life Science, Box 7624, North Carolina State University, Raleigh, North Carolina 27695-7624, USA 2: Department of Food Science, College of Agriculture and Life Science, Box 7624, North Carolina State University, Raleigh, North Carolina 27695-7624, USA

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