Effect of X-ray treatments on Escherichia coli O157: H7, Listeria monocytogenes, Shigella flexneri, Salmonella enterica and inherent microbiota on whole mangoes

Abstract

The aims of this investigation were to; (i) study the effect of X-ray treatments in reducing Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on whole mangoes, and (ii) study the effect of X-ray treatments on microflora counts (mesophilic counts, psychrotrophic counts and yeast and mould counts) of whole mangoes during storage at ambient temperature (22°C) for 30 days. A mixture of three strains of each test organism was spot inoculated (100 μl; approx. 8-9 log CFU ml-1), separately, onto the surface (5 cm2) of whole mangoes, air-dried (30 min), and then treated with different doses of X-ray (0, 0·1, 0·5, 1·0, and 1·5 kGy). Approximately 2·9, 1·8, 2·1 and 5·2 log CFU cm-2 reduction of E. coli O157:H7, L. monocytogenes, Sh. flexneri and Salm. enterica were achieved by treatment with 0·5 kGy X-ray respectively. Furthermore, the populations of E. coli O157:H7, L. monocytogenes, Sh. flexneri and Salm. enterica were reduced to less than the detectable limit (2·0 log CFU cm-2) by treatment with 1·5 kGy X-ray. Treatment with 1·5 kGy X-ray significantly reduced the initial inherent microflora on skin of whole mangoes and inherent levels were significantly (P < 0·05) lower than the control sample throughout storage at 22°C for 30 days.