Synergistic effects of E-Beam irradiation and dried herbs powder(Thymus capitatus) on the physicochemical and microbiological quality of minced beef

In response to increasing consumer concerns over synthetic additives and essential oils(EOs) use, plant powders are gaining attention as natural and stable alternatives for food preservation. This study explores the effects of low-dose electron beam (E-Beam) irradiation (2 kGy) and Thymus capitatus powder, on the quality and microbial stability of minced beef stored at refrigeration temperature over nine days. The thyme leaves, harvested from northern Tunisia, were first characterized and found to contain high levels of total phenolics, along with moderate concentrations of flavonoids and condensed tannins. UHPLC-DAD-ESI/MS n analysis revealed high concentrations of rosmarinic acid and carvacrol, which are presumed to contribute significantly to the observed antibacterial activity. When applied to minced meat, the combined treatment of low-dose irradiation (2 kGy) and thyme powder achieved a synergistic reduction in microbial counts, including E. coli (4.73 Log 10 CFU/g), total coliforms (4.62Log 10 CFU/g), Staphylococcus spp. (3.87 Log 10 CFU/g), molds and yeasts (1.9 Log 10 CFU/g) compared to untreated controls. Moreover, the combination significantly limited lipid oxidation (0.206 mg MDA/kg), while maintaining acceptable color parameters and mitigating the discoloration typically caused by thyme alone. The difference between the combined treatment (2 kGy and thyme) and high dose irradiation treatment (4 kGy) was statistically non-significant. Although lipid oxidation increased in some treatments (e.g., 4 kGy), all TBARS values remained below the threshold associated with detectable rancidity, ensuring acceptable sensory quality throughout storage. These findings highlight the potential of combining Thymus capitatus powder with low-dose E-Beam irradiation as a natural, effective preservation strategy that may reduce the need for higher irradiation doses, synthetic preservatives or EOs. • 4 kGy irradiation exhibited the highest antimicrobial activity but accelerated oxidation. • The synergy thyme-irradiation extends beyond oxidative and colour stability. • Low-dose E-Beam and Thyme powder have synergistic antimicrobial activity. • Treatment's nature had an impact on measured microbial populations during storage.