title: Reduction of Escherichia coli O157:H7 and Salmonella on baby spinach, using electron beam radiation.
abstract: The effect of low-dose electron beam (e-beam) radiation on the reduction of Escherichia coli O157:H7 and Salmonella in spinach was studied. Fresh baby spinach (Spinacia oleracea) was inoculated with a bacterial cocktail containing multiple strains of rifampin-resistant E. coli O157:H7 and rifampin-resistant Salmonella. Inoculated samples were exposed to e-beam radiation from a linear accelerator and tested for counts of both E. coli O157:H7 and Salmonella. Irradiated spinach was also stored for 8 days at 4 degrees C, and counts were made at 2-day intervals to determine if there was any effect of radiation on the survival trend of both pathogens. When no pathogens were detected on plates, additional enrichment plating was conducted to verify total destruction. Respiration rates were measured on spinach samples exposed to e-beam radiation. Each dose of e-beam radiation significantly reduced the numbers of E. coli O157:H7 and Salmonella from initial levels of 7 log CFU/g. Treatment by e-beam radiation at a dose of 0.40 kGy resulted in a reduction in populations of E. coli O157:H7 and Salmonella of 3.7 and 3.4 log cycles, respectively. At 0.70 kGy, both pathogens were reduced by 4 log. All doses above 1.07 kGy showed reductions greater than 6 log and decreased to undetectable levels when stored for 8 days. The respiration rate of spinach showed no changes after irradiation up to 2.1 kGy. These results suggest that low-dose e-beam radiation may be a viable tool for reducing microbial populations or eliminating E. coli O157:H7 and Salmonella from spinach without product damage.
authors.affiliation: Department of Animal Science, 2471 TAMU, Texas A&M University, College Station, Texas 77843-2471, USA.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Neal
authors.forename: Elisa
authors.initials: E
authors.lastname: Cabrera-Diaz
authors.forename: Mayra
authors.initials: M
authors.lastname: Márquez-González
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Maxim
authors.forename: Alejandro
authors.initials: A
authors.lastname: Castillo
mesh_terms: D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004307:Dose-Response Relationship, Radiation; D019453:Escherichia coli O157 / Q000254:growth & development / Q000528:radiation effects*; D005506:Food Contamination / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005514:Food Irradiation; D005516:Food Microbiology; D012475:Salmonella / Q000254:growth & development / Q000528:radiation effects*; D018724:Spinacia oleracea / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors