Effects of irradiation dose and O₂ and CO₂ concentrations in packages on foodborne pathogenic bacteria and quality of ready-to-cook seasoned ground beef product (meatball) during refrigerated storage

Combined effects of gamma irradiation and concentrations of O₂ (0, 5, 21%) and CO₂ (0, 50%) on survival of Escherichia coli O157:H7, Salmonella enteritidis, Listeria monocytogenes, lipid oxidation, and color changes in ready-to-cook seasoned ground beef (meatball) during refrigerated storage were investigated. Ground beef seasoned with mixed spices was packaged in varying O₂ and CO₂ levels and irradiated at 2 and 4kGy. Irradiation (4 kGy) caused about 6 Log inactivation of the inoculated pathogens. Inactivation of Salmonella was 0.9- and 0.4-Log lower in 0 and 5% O₂, respectively, compared to 21 O₂. Irradiation at 2 and 4kGy increased thiobarbituric acid reactive substances in meatballs by 0.12 and 0.28mg malondialdehyde kg^-1, respectively, compared to control. In reduced-O₂ packages, radiation-induced oxidation was lower, and the initial color of an irradiated sample was maintained. Packaging with 0 + 50 CO₂ or 5 O₂ + 50 CO₂ maintained the oxidative and the color quality of irradiated meatballs during 14-day refrigerated storage. MAP with 5O₂ + 50 CO₂ combined with irradiation up to 4kGy is suggested for refrigerated meatballs to reduce the foodborne pathogen risk and to maintain the quality.