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We investigated the effects of UV irradiation on Salmonella enteritidis viability spiked onto the eggshell surface. The eggshell was experimentally contaminated with S. enteritidis (108 CFU/ml) and then treated by UV irradiation at 245 nm with the intensity of 730, 1,580 and 3,000 μW/cm2, respectively, and also irradiation time was set as 10, 30, and 60 seconds respectively. The viable counts for S. enteritidis after the iradiation showed that all the UV irradiated groups resulted in significant reduction of the viable cell count by more than 2 log units, compared with control group (p<0.05). However, no significant differences were recognized by the parameter of irradiation time on the cell viability. These results suggested that the bacteriocidal activity of UV irradiation on S. enteritidis might be affected markedly, as the irradiation intensity increases up to 3,000 μW/cm2, rather than the irradiation time. The viability of aerobic microorganism assessed by an APC method after UV irradiation was also significantly reduced, however the reduction rate was lower than that of S. eneteritidis. Additionally, the viability of S. enteritidis during storage at room temperature agter high intensity irradiation (3,000 μW/cm2) were also investigated in daily basis. The bacterial cell population on the eggshell after the irradiation were decreased to log 3.89 from log 7.36 CFU of untreated eggshell group, and finally no bacterial counts were detected after 9 days of storage.
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