Effect of electron-beam irradiation before and after cooking on the chemical properties of beef, pork, and chicken.

Ground beef, pork, and chicken thigh meats were irradiated at 0 or 5.0kGy before and after cooking and then stored at -40°C in oxygen permeable bags. The pH, lipid oxidation, volatiles, and carbon monoxide production of the meat were determined at 0 and 6months of storage. The pH values of raw meats from different animal species were different (5.36-6.25) and were significantly increased by cooking, irradiation, and storage (p<0.05). Irradiation had no effect on the TBARS values of ground beef and pork, but significantly increased the TBARS of chicken thigh meat. Cooking, whether it was done before or after irradiation, caused significant increase in TBARS and was most significant in chicken and pork. The numbers of volatiles analyzed by GC/MS were higher in irradiated meats than the non-irradiated ones regardless of meat source. Sulfur-containing compounds were newly produced or increased by irradiation, but dimethyl disulfide and dimethyl trisulfide were not detected in the non-irradiated meats regardless of cooking treatment. Irradiation time, whether done before or after cooking, had little effect on the TBARS, volatiles, and carbon monoxide production in the meat.