Gamma Irradiation Effects on Oxidation, Microbial Growth, and Volatile Compounds in Beef Aged at High Temperatures

The present study aimed to evaluate the effects of gamma irradiation (0 and 3 kGy) and aging (up to 14 days) at different temperatures (1, 7, and 15 °C) on protein and lipid oxidation, mesophilic growth, and the volatile profile of bovine Longissimus lumborum muscle. Although irradiation has been proposed as a strategy to enable accelerated aging, limited information is available on its combined effects with elevated temperatures on the oxidative stability and volatile formation. Protein oxidation was not significantly affected (P > 0.05) by irradiation; however, carbonyl formation increased (P < 0.05) with longer aging periods and higher temperatures. Thiobarbituric acid reactive substance values ranged from 0.15 to 0.50 mg MDA/kg and were higher (P < 0.05) in irradiated samples aged for 14 days at elevated temperatures (7 and 15 °C). Mesophilic growth was greater (P < 0.05) in nonirradiated samples aged at higher temperatures, with mesophilic counts exceeding the acceptable limit (7 log CFU/g) after 7 days at 15 °C. Irradiation reduced (P < 0.05) mesophilic counts below the maximum acceptable limit (10⁷ CFU/g) across all treatments. Increased aging temperature significantly affected (P < 0.05) volatile formation, particularly those compounds associated with spoilage processes (lipid and protein oxidation and microbial metabolism), which were more abundant (P < 0.05) in nonirradiated samples stored at 15 °C. Irradiation had a limited effect on the volatile compounds formed, except for dimethyl sulfide, which increased in irradiated samples. Therefore, a low radiation dose can be effectively used to control mesophilic microbial growth under elevated aging temperatures, although its effect on lipid oxidation is dependent on storage conditions and may increase under extended aging at higher temperatures.