title: Magnetized carbonyl iron and insoluble zirconium hydroxide mixture facilitates bacterial concentration and separation from nonfat dry milk.
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 10(3) to 10(6) 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 valueswere 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.
authors.affiliation: Department of Food Science, College of Agriculture and Life Science, North Carolina State University, Raleigh 27695-7624, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Cullison
authors.forename: Lee-Ann
authors.initials: LA
authors.lastname: Jaykus
mesh_terms: D000818:Animals; D001409:Bacillus cereus / Q000302:isolation & purification*; D018914:Cells, Immobilized; D015169:Colony Count, Microbial; D005516:Food Microbiology; D054354:Iron Carbonyl Compounds; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008892:Milk / Q000382:microbiology*; D009942:Organometallic Compounds; D012477:Salmonella enteritidis / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D012995:Solubility; D013171:Spores, Bacterial; D015040:Zirconium
chemical_list: D009942:Organometallic Compounds; D054354:Iron Carbonyl Compounds; D015040:Zirconium