title: Recovery of Salmonella enterica serovars Typhimurium and Tennessee in peanut butter after electron beam exposure.
abstract: The effect of electron beam (e-beam) radiation on the recovery of Salmonella serotypes Tennessee (ATCC 10722) and Typhimurium (ATCC 14028) in creamy peanut butter over a 14-d storage period at 22 °C was studied. Each Salmonella type was independently inoculated into peanut butter and subjected to e-beam doses that ranged from 0 to 3.1 kGy, confirmed by film dosimetry. After 2-, 4-, 6-, 8-, and 14-d of storage, microbial analyses were conducted. Survivors were recovered on growth and selective media using standard spread-plating methods. Microbial counts (CFU/g) were log-converted and differences were determined by ANOVA and Tukey's Honestly Significant Differences test. When samples were not e-beam-treated, there were no significant changes (P > 0.05) in microbial numbers over time. In e-beamed samples, microbial numbers decreased over time; however, reductions were not always significant. Initial recovery rates (R-rates) 2 d after e-beam treatment were significantly different for the 2 strains of Salmonella and between recovery media (P < 0.05); however, these differences did not persist for the remainder of the storage period (P > 0.05) indicating that injured cells were not able to survive in the high-fat, low-water activity peanut butter environment. R-rates for both strains of Salmonella were maintained until day 14 when there were significant reductions in Salmonella Typhimurium (P < 0.05). These results indicate that Salmonella Tennessee and Salmonella Typhimurium will survive in peanut butter when exposed to nonlethal doses of e-beam irradiation.
  
  
  CONCLUSIONS
  Electron beam (e-beam) irradiation is an alternative to thermal processing; this technique inactivates microorganisms and insects that might be present in a food by generating radiation by accelerated electrons that inactivate organisms directly because of interaction with cell components and indirectly by producing free radicals that disrupt integrity of the cell membrane. E-beam radiation will reduce the number of probable microbiological hazards that could be present while the food remains generally unaffected in texture, taste, and nutritional value. A recent study showed e-beam irradiation to be effective at reducing both Salmonella Tennessee and Typhimurium in peanut butter by one log after exposure to less than 1 kGy, highlighting the need to explore this process further.
authors.affiliation: West Virginia Univ., Dept. of Animal and Nutritional Sciences, Morgantown, WV 26506, USA. kristen.matak@mail.wvu.edu
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Matak
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Hvizdzak
authors.forename: Sarah
authors.initials: S
authors.lastname: Beamer
authors.forename: Jacek
authors.initials: J
authors.lastname: Jaczynski
mesh_terms: D010367:Arachis / Q000382:microbiology*; D015169:Colony Count, Microbial; D003212:Condiments / Q000382:microbiology*; D005511:Food Handling; D005514:Food Irradiation / Q000379:methods; D050296:Microbial Viability; D015203:Reproducibility of Results; D012475:Salmonella / Q000254:growth & development / Q000528:radiation effects*; D012478:Salmonella Food Poisoning / Q000517:prevention & control; D012486:Salmonella typhimurium / Q000254:growth & development / Q000528:radiation effects; D012639:Seeds / Q000382:microbiology*; D013045:Species Specificity; D013997:Time Factors