Title: Sensitivity of Pseudomonas fluorescens to gamma irradiation following surface inoculations on romaine lettuce and baby spinach Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2014
Publication Date: August 3, 2014
Citation: Olanya, O.M., Niemira, B.A., Phillips, J.G. 2014. Sensitivity of Pseudomonas fluorescens to gamma irradiation following surface inoculations on romaine lettuce and baby spinach. Journal of Food Protection Supplement. Meeting Abstract. IAFP Annual Meeting, Indianapolis, Indiana. 8/3 to 8/6, 2014. Volume 71: 104 pg.. Technical Abstract: Irradiation of fresh fruits and vegetables is a post-harvest intervention measure often used to inactivate pathogenic food-borne microbes. We evaluated the sensitivity of Pseudomonas fluorescens strains (2-79, Q8R1, Q287) to gamma irradiation following surface inoculations on romaine lettuce and spinach. The P. fluorescens strains are non-plant pathogenic, non-pectolytic, and saprophytic in nature. Gamma irradiation was applied on romaine lettuce and spinach at doses of 0 (control), 0.25, 0.5, 0.75 and 1.0 kGy and the leafy greens were subsequently stored for 24 hrs at 5 ºC. The effects of gamma irradiation were also determined on bacteria cells suspended in buffered peptone water (BPW) in tubes. The initial Pseudomonas populations ranged from 9.08 to 9.69 log CFU/ml of BPW in the non-irradiated control. The bacterial counts on the non-irradiated spinach and romaine lettuce ranged from 8.14 to 8.95 and from 8.32 to 8.63 log CFU/g, respectively. The radiation D10 values of P. fluorescens suspended in BPW ranged from 0.09 to 0.12 kGy when enumerated on Pseudomonas Agar F and Trypticase Soy Agar. However, on spinach and romaine lettuce, the D10 values of P. fluorescens were significantly (P<0.05) lower and ranged from 0.04 to 0.05 and from 0.05 to 0.06 kGy, respectively. These results indicate that P. fluorescens has a relatively high sensitivity to irradiation and the simultaneous applications of irradiation and biological control treatments will enhance potential inactivation of food-borne pathogens.