title: Thermal death time measurement using thin flexible sleeves: a new experimental approach for determining microbial destruction kinetics in fluids of arbitrary viscosity.
abstract: The thermal death time kinetics of Salmonella Enteritidis (SE) was measured in buffer, egg yolk, and albumen using thin layer plastic sleeves. The sleeves allowed for the loading and sampling of liquids of high or unusual viscosity, as in the case of yolk and albumen, and accepted relatively large volumes (2 to 3 ml) of fluid. The sleeves maintained the volume of the fluid in a thin layer and could be easily handled for heat exposure. The thin layer maintained one-dimensional heat transfer and minimized temperature gradients, thus preventing parts of the fluid from experiencing different heating rates. A representative strain of SE associated with an egg-based salmonellosis outbreak was used in this study. The D- and z-values of the chosen strain, H7037, were measured in buffer, yolk, and albumen. In buffer, SE had the following mean (±standard deviation) D-values: D(55°C) = 3.51 ± 0.30 min, D(57°C) = 1.75 ± 0.13 min, and D(60°C) = 0.25 ± 0.06 min. In yolk, D(58°C) = 0.90 ± 0.05, D(60°C) = 0.26 ± 0.03, and D(62°C) = 0.20 ± 0.02. In albumen, D(55°C) = 1.26 ± 0.31, D(56°C) = 0.68 ± 0.10, and D(57°C) = 0.44 ± 0.04. The z-values for SE calculated from these D-values were 4.29 ± 0.39°C in buffer, 6.12 ± 0.26°C in yolk, and 4.63 ± 1.14°C in albumen. The sleeves allowed one consistent approach to determining thermal death time kinetics regardless of viscosity.
authors.affiliation: U.S. Food and Drug Administration, National Center for Food Safety and Technology, 6502 South Archer Road, Summit-Argo, Illinois 60501, USA. gregory.fleischman@fda.hhs.gov
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Fleischman
authors.forename: Mani K
authors.initials: MK
authors.lastname: Badvela
authors.forename: Andre
authors.initials: A
authors.lastname: Rehkopf
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Stewart
mesh_terms: D000818:Animals; D003257:Consumer Product Safety; D004530:Egg Yolk / Q000382:microbiology; D004531:Eggs / Q000032:analysis / Q000382:microbiology*; D005519:Food Preservation / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D050296:Microbial Viability; D010047:Ovalbumin / Q000032:analysis; D012478:Salmonella Food Poisoning / Q000517:prevention & control; D012477:Salmonella enteritidis / Q000254:growth & development*; D014783:Viscosity
chemical_list: D010047:Ovalbumin