Use of irradiation for decontamination of chicken and spray-dried whole egg powder from Salmonellae

The effect of 60Co gamma irradiation was investigated on the concentration of Salmonella (S.) typhimurium in artificially contaminated chicken carcasses and on the number of S. tennessee and S. agona in artificially contaminated spary-dried whole egg powder and liquid whole egg. Irradiation of carcasses and of liquid whole egg was carried out at deep frozen conditions between -10 0C and -18 0C and whole egg powder at 15-20 0C. The irradiation doses used where between 0.05 and 8.0 kGy. The D10-value of S. typhimurium in broiler chicks ranged between 0.57 and 0.74 and of S. agona and S. tennessee, resp., amounted to 0.95 and 1.07 in spray dried whole egg powder and 0.47 and 0.53, resp., in whole egg content. Irradiation caused drastic reduction of physiological microflora in chicken carcasses. By radiation treatment using a dose of 4.0 kGy, germ count reductions by 3-5 decimal powers were achieved. Resistance of microbes increased in following succession: Pseudomonas spp., Salmonella spp., other Enterobacteriaceae spp., Micrococcus spp., Flavobacteriaceae spp., yeasts. Bacillus spp., Streptomyces spp., fungi. Results of microbiological and sensorial examinations allow following conclusions: (1) irradiation is highly effective against Salmonella. (2) Irradiation dose of 4.0 kGy is able to kill about 1 million Salmonellae per chicken. This guarantees safe elimination of naturally occurring Salmonellae in broiler chicken carcasses. (3) Irradiation of chicken carcasses up to 4.0 kGy causes no deterioration of quality, however storage longer than 4 months deteriorates sensorial qualities more than of unirradiated carcasses. (4) Whole egg powder tolerates a maximal irradiation dose of 2.0 kGy without deterioration of sensorial food quality. (5) Irradiation dose of 1.0 kGy eliminates about 100 to 1000 Salmonellae per kg whole egg powder, if the egg powder is stored 3 to 5 weeks after irradiation. (author)