title: Effect of x-ray treatments on pathogenic bacteria, inherent microbiota, color, and texture on parsley leaves.
abstract: This work is a part of systematic studies of the effect of X-ray treatments on fresh produce. The main objective of this investigation was to study the effects of X-ray treatments in reducing the concentration of artificially inoculated Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, and Shigella flexneri, and inherent microbiota on parsley leaves. The secondary objective was to study the effects of X-ray treatments on color and texture parameters on treated parsley leaves. The Dip-inoculated method was used to inoculate parsley leaves with a mixture of two or three strains of each tested organism at 10(8) to 10(9) colony-forming unit (CFU)/mL; the inoculated parsley leaves were then 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). Approximately 5.8, 3.1, 5.7, and 5.2 log CFU reductions 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 (1.0 log CFU/g) by treatment with 1.5 kGy X-ray. Treatment with 1.5 kGy X-ray significantly reduced the initial inherent microbiota on parsley leaves, and inherent levels were significantly (p < 0.05) lower than the control sample throughout refrigerated storage for 30 days. No significant differences (p > 0.05) in color or texture of control and treated samples with 0.1-1.5 X-ray were observed. 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 to extend the shelf life of parsley leaves.
authors.affiliation: Coastal Research & Extension Center, Mississippi State University, Pascagoula, Mississippi 39567, USA. bm547@msstate.edu
authors.forename: Barakat S M
authors.initials: BS
authors.lastname: Mahmoud
mesh_terms: D003080:Cold Temperature; D015169:Colony Count, Microbial; D003116:Color; D003257:Consumer Product Safety; D019453:Escherichia coli O157 / Q000254:growth & development / Q000528:radiation effects; D005511:Food Handling / Q000379:methods; D005514:Food Irradiation / Q000379:methods*; D005516:Food Microbiology; D061353:Food Storage; D008089:Listeria monocytogenes / Q000254:growth & development / Q000528:radiation effects; D054892:Metagenome / Q000528:radiation effects*; D028528:Petroselinum / Q000737:chemistry / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology*; D019779:Salmonella enterica / Q000254:growth & development / Q000528:radiation effects; D012763:Shigella flexneri / Q000254:growth & development / Q000528:radiation effects; D013234:Stem Cells; D014965:X-Rays