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.

Inactivation of sanitizer-injured Escherichia coli O157:H7 on baby spinach using X-ray irradiation

“…In previous work, gamma radiation respectively yielded D 10 -values of 0.27 and 0.14 kGy for E. coli O157:H7 internalized in spinach and on the surface of lettuce (Niemira, 2007;Niemira, Sommers, & Fan, 2002). Similar E. coli O157:H7 inactivation values also have been reported using E-beam, with a D 10 -value of 0.20 kGy for baby spinach (Neal, Cabrera-Diaz, Marquez-Gonzalez, Maxim, & Castillo, 2008).…”

Application of electron beam to inactivate Salmonella in food: Recent developments

“…In another study Neal, Cabrera-Diaz, Maquez-Gonzalez, Maxim, & Castillo (2008) investigated the effects of low-dose e-beam on the reduction of rifampin-resistant Salmonella inoculated in baby spinach. E-beam at 0.4 and 0.7 kGy resulted in the reduction of Salmonella by 3.4 and 4-log, respectively.…”

Comparison of multiple chemical sanitizers for reducing Salmonella and Escherichia coli O157:H7 on spinach (Spinacia oleracea) leaves

“…Therefore, in an effort to reduce the number of foodborne illnesses associated with fresh produce, research must be conducted on each type of fruit or vegetable concerning specific pathogens as well as multiple types of interventions or treatment methods (Neal, Cabrera-Diaz, Marquez-Gonzalez, Maxim, & Castillo, 2008). Numerous studies have been performed to demonstrate the influence of chemical sanitizers on produce as well as the influence of hurdle treatments on minimally processed vegetables.…”