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 30days. A mixture of three strains of each test organism was spot inoculated (100μl; approx. 8-9logCFUml(-1) ), separately, onto the surface (5cm(2) ) of whole mangoes, air-dried (30min), and then treated with different doses of X-ray (0, 0·1, 0·5, 1·0, and 1·5kGy). Approximately 2·9, 1·8, 2·1 and 5·2logCFUcm(-2) reduction of E.coli O157:H7, L.monocytogenes, Sh.flexneri and Salm.enterica were achieved by treatment with 0·5kGy 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 (2·0logCFUcm(-2) ) by treatment with 1·5kGy X-ray. Treatment with 1·5kGy 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 30days. Fresh produce was associated with 770 outbreaks between 1990 and 2005, resulting in 35060 cases of illness that costs the US $39 billion annually. The food industry is looking for new preservation methods. This investigation indicated that X-ray treatment was very effective against Escherichia coli O157:H7, Listeria monocytogenes, Shigella flexneri and Salmonella enterica and inherent microflora on whole mangoes which could offer an applicable approach to control pathogens and spoilage bacteria for the mango industry.