Purpose: The objectives of this investigation were to: a) study the reduction of E. coli O157:H7, L. monocytogenes, S. enterica and Shigella flexneri on parsley by X-ray and b) study the effect of X-ray treatments on microflora counts (mesophilic counts, psychrotrophic counts and yeast and mold counts) of untreated and treated parsley during storage at 5°C for 30 days.
Methods: Dip-inoculated method was used to inoculate parsley leaves, separately, with a mixture of three strains of each tested organism (approximately 8–9 log ml−1), air-dried, and followed by treatment with different doses of X-ray (0, 0.1, 0.5, 1.0, and 1.5 kGy) at 22°C and 55–60% relative humidity. Surviving bacterial populations on parsley leaves were evaluated using a nonselective medium (tryptic soy agar) with a selective medium overlay for each bacterium; E. coli O157:H7 (CT-SMAC agar), L. monocytogenes (MOA), and S. enterica and S. flexneri (XLD).
Results: Approximately 5.8, 3.1, 5.7 and 5.8 log CFU reduction of E. coli O157:H7, L. monocytogenes, S. enterica and Shigella flexneri were achieved by treatment with 1.0 kGy X-ray, respectively. Furthermore, the populations of E. coli O157:H7, L. monocytogenes, S. enterica and Shigella flexneri were reduced to less than the detectable limit (2 log CFU/g) by treatment with 1.5 X-ray. Treatment with 1.5 kGy X-ray significantly reduced the initial inherent microflora on green peppers and inherent levels were significantly (p < 0.05) lower than the control sample throughout refrigerated storage for 30 days.
Significance: The results of investigation indicated that X-ray is an effective technology to eliminate E. coli O157:H7, L. monocytogenes, S. enterica and Shigella flexneri and extend the shelf life of parsley leaves.