Shelf Life of Ground Beef Patties Treated by Gamma Radiation

Abstract

The effects of irradiation on microbial populations in ground beef patties vacuum packaged and irradiated frozen at target doses of 0.0,1.0, 3.0, 5.0, and 7.0 kGy were determined. Irradiated samples were storedat4or − 18°C for 42 days, and mesophilic aerobic plate counts (APCs) were periodically determined. Fresh ground beef (initial APC of 102 CFU/g) treated with 3.0,5.0, and 7.0 kGy was acceptable (<107 CFU/g) for 42 days at 4°C. The 1.0 kGy-treated beef samples were acceptable microbiologically (<107 CFU/g) after 42 days but developed an unacceptable off-odor after 21 days. Shelf life diminished in fresh ground beef patties with an initial APC of 104 CFU/g. Only beef patties treated with 7.0 kGy were found to be acceptable at 42 days. Beef patties treated at 1.0 and 3.0 kGy reached spoilage APC levels (>107 CFU/g) by day 14 and 21, respectively, whereas patties treated at 5.0 kGy did not spoil until 42 days. The nonirradiated control samples for both batches of ground beef spoiled within 7 days. Microbial counts in ground beef patties stored at − 18°C did not change over the 42-day period. Shelf life of ground beef patties stored at 4°C may be extended with gamma radiation, especially at 5.0 and 7.0 kGy. Initial microbial load in ground beef samples was an important shelf life factor.