Effect of Irradiation on Salmonella Survival and Quality of 2 Varieties of Whole Green Onions

Abstract

Two varieties of green onions, Banner and Baja Verde, were inoculated with a cocktail of 3 Salmonella strains using dip and spot inoculation and irradiated at 0, 0.3, 0.6, 0.9, and 1.2 kGy using electron beam. Salmonella survivors were enumerated using a XLD underlay/TSAYE overlay plating method. The D values were in the range of 0.26 to 0.32 kGy depending on variety but not on the method of inoculation. This indicated that a 5-log reduction of Salmonella can be achieved at a dose of 1.6 kGy. For the quality study, both varieties of green onions were irradiated at 0, 1.5, 2.0, and 2.5 kGy and evaluated for changes in microbial counts, color, texture, and visual quality during storage at 4 °C. Irradiation reduced total plate counts and psychrotrophs by 3 logs. Although the counts increased during storage, they did not exceed the initial counts of control. No significant difference was observed in color and texture between irradiated samples and control. The control maintained good visual quality for about 13 d as compared to 15 d for 1.5 and 2.5 kGy samples. The 2.0 kGy samples maintained good visual quality for 17 d suggesting that irradiation can increase shelf life by reducing spoilage microorganisms but higher doses can be detrimental to quality. At the dose levels required to achieve a 5-log reduction in Salmonella, the shelf life of whole green onion can be extended. This study shows that irradiation can be used to enhance safety without adverse effects on quality.

Application of pulsed light (PL)-surfactant combination on inactivation of Salmonella and apparent quality of green onions

“…There is a need to find an alternative decontamination strategy that is more effective, safer to use and more environmental friendly. In the last decade, several emerging techniques including ozonated water (Xu & Wu, 2014), high hydrostatic pressure (Neetoo, Nekoozadeh, Jiang, & Chen, 2011), electrolyzed water (Park, Alexander, Taylor, Costa, & Kang, 2008) and irradiation (Fan, Niemira, & Sokorai, 2003;Murugesan, Williams-Hill, & Prakash, 2011) have been studied to inactivate Salmonella and/or Escherichia coli O157:H7 in green onions. Studies of hurdle techniques, especially combinations of emerging technique and traditional sanitizer washing have drawn great attention.…”

Scientific Opinion on the risk posed by pathogens in food of non‐animal origin. Part 2 (Salmonella, Yersinia, Shigella and Norovirus in bulb and stem vegetables, and carrots)

“…Various sanitizers and other treatments have been evaluated for treating bulb and stem vegetables and carrots for reducing Salmonella contamination, and these are generally of experimental nature and provide a low strength of evidence. These treatments included: chlorine and peroxyacetic acid (Ge et al, 2013); electrolyzed water (Abadias et al, 2008;Park et al, 2008Park et al, , 2009; ozonated water (Xu and Wu, 2014); irradiation (Lopez et al, 2005;Dhokane et al, 2006;Song et al, 2006;Murugesan et al, 2011;Ndoti-Nembe et al, 2013); thermoultrasound and calcium propionate (Kwak et al, 2011); dense phase carbon dioxide (Liao et al, 2010); essential oils and bacteriocins (Ndoti-Nembe et al, 2013); high hydrostatic pressure (Nettoo et al, 2011(Nettoo et al, , 2012; carvacrol and cinnamaldehyde (Ravishankar et al, 2010); and gaseous chlorine dioxide (Sy et al, 2005).…”

Localization of Viable Salmonella Typhimurium Internalized through the Surface of Green Onion during Preharvest

“…Internalization of pathogens reduces the efficacy of washing with chemical sanitizers because of their limited ability to permeate the subsurface of the produce (18,25,26). Owing in part to its unique flavor, green onion is commonly used as a fresh garnish or seasoning, and it is consumed raw or minimally cooked, especially in Asian and Mexican cuisines (20,28). Therefore, any pathogen contamination in green onions can cause foodbome outbreaks.…”