Purpose : The aims of this investigation were to: a) study the effect of x-ray treatments in reducing E. coli O157:H7, L. monocytogenes, S. enterica and Shigella flexneri on whole mangos and b) study the effect of x-ray treatments on microflora counts (mesophilic counts, psychrotrophic counts and yeast and mold counts) of whole mangos during storage at ambient temperature 22°C for 30 days.
Methods: A mixture of three strains of each test organism was spot inoculated (100 µl), separately, onto the surface (5 cm2) of whole mangos (approximately 8-9 log CFU ml-1), air dried (30 min), and then treated with different doses of X-ray (0, 0.1, 0.5, and 1.0 kGy) at 22°C and 55% relative humidity at 22°C and 55–60% relative humidity. Surviving bacterial populations on whole mango surfaces 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 2.2, 0.8, 4.1 and 2.0 log CFU reduction of E. coli O157:H7, L. monocytogenes, S. enterica and Shigella flexneri were achieved by treatment with 0.1 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 storage at 22°C for 30 days.
Significance : These results showed that treatment with X-ray significantly reduced selected pathogens and inherent microorganisms on whole mangos, which could be a good alternative to other technologies for fruits industry.