Inactivation of food spoilage fungi by ultra violet (UVC) irradiation

The effect of ultraviolet irradiation (254 nm, UVC) on Aspergillus flavus, Aspergillus niger, Penicillium corylophilum and Eurotium rubrum was investigated using three different exposure techniques. Survival was determined for spores suspended in liquid medium after 1, 2 and 3 min UVC exposure at 4644 J/m2/min. The same UVC dose was applied to spores on the surface of agar plates for 5, 10, 15, 30, 60 and 120 s. Spores of A. niger were dried onto a membrane filter, then exposed to UVC treatment. In the liquid medium, treatments from 1–3 min significantly (P < 0.001) reduce the number of viable spores. On the surface of agar plates, after a 15 s exposure, a 80–99% reduction of viable spores was observed for all species except A. niger, for which the reduction was only 62%. For spores dried onto filter membranes, a 3.5 log10 reduction was achieved for A. niger after 180 s exposure. These observations suggest that UVC irradiation can effectively inactivate spores of A. flavus, P. corylophilum, E. rubrum and A. niger but the efficacy of UVC radiation against fungal spores varies significantly according to methods of exposure to the irradiation, and among genera.