UV IRRADIATION OF SHELL EGGS - EFFECT ON POPULATIONS OF AEROBES, MOLDS, AND INOCULATED SALMONELLA-TYPHIMURIUM

The effects were investigated of 254-nm UV radiation on populations of Salmonella typhimurium, aerobes, and molds on the shells of eggs. In the first experiment, the CFU of attached S. typhimurium cells on unwa shed clean shell eggs were determined after 0, 1, 3, 5, and 7 min of U V treatment (620 mu W/cm(2)) on both ends of the egg. All UV treatment s significantly reduced S. typhimurium CFU (P <.01). UV treatment (620 mu W/cm(2)) in I-min alternating light and dark cycles for 5 min (thr ee light and two dark) was compared to 0, 3, and 5 min of UV treatment . No significant differences in microbial populations were observed am ong light and dark cycles and the other UV treatments. In a subsequent experiment, the same UV treatments were utilized to evaluate photorea ctivation. After UV exposure, eggs were exposed to 1 h of fluorescent light or 1 h of darkness or cultured immediately. S. typhimurium CFU w ere significantly (P <.01) reduced by the UV treatments. However, no s ignificant differences between microbial populations exposed to UV tre atment and UV radiation plus photoreactivation were detected. For stud ies of aerobic bacteria and molds, different UV treatment times (0, 15 , and 30 min) at the intensity of 620 mu W/cm(2) and different intensi ties (620, 1350, and 1720 mu W/cm(2)) for 15 min were evaluated. Mold CFU per egg were either 0 or 1 for all UV treatments and a 99% reducti on of CFU of aerobic bacteria per egg were observed for all UV treatme nts. It appears from these studies that UV light can significantly red uce populations of S. typhimurium, aerobes, and molds on shell eggs.