Survival of Pseudomonas fluorescens and Salmonella Typhimurium after electron beam and gamma irradiation of refrigerated beef

The radurization effects of gamma ray and electron beam irradiation at 1.5 and 3.0 key on beef steaks inoculated with Salmonella Typhimurium and Pseud omonas fluorescens were investigated during 8 days of storage at 5 degrees C. Total bacterial counts and numbers of Salmonella Typhimurium and P. fluo rescens were analyzed at 2-day intervals. Total bacterial counts of samples irradiated by both gamma rays and electron beam were significantly (P < 0. 05) reduced by 3.8 to 5.3 log CFU/g. Salmonella Typhimurium was not detecta ble during the experimental period. P. fluorescens counts of beef samples i rradiated by gamma rays at both 1.5 and 3.0 kGy were not detected; however, P. fluorescens in samples irradiated by electron beam at 1.5 and 3.0 kGy w as recovered after 2 days, and bacterial counts reached 7.8 and 6.9 log CFU /g, respectively. Both gamma ray and electron beam irradiation reduced tota l bacterial counts initially, possibly extending shelf life. Irradiation wa s very effective in destroying Salmonella Typhimurium; however, P. fluoresc ens was not completely eliminated by electron beam irradiation. Consequentl y, gamma ray irradiation was more effective than electron beam irradiation in the destruction of P. fluorescens.