Dose rates of electron beam and gamma ray irradiation affect microbial decontamination and quality changes in dried...

Due to differences in radiation sources (electron beam from electron accelerator, gamma ray from ⁶⁰ Co radionuclide) and energy delivery time (dose rate, kGy/time), the effects on foods are expected to be different with regard to chemical quality change and microbial decontamination. To better understand this impact, effects of variable dose rates of electron beam (EB, kGy s^-1 ) and gamma rays (GR, kGy h^-1 ) on microbial reduction, capsanthin content, and color parameters of red pepper (Capsicum annuum L.) powders (RPP) were determined. RPP samples were irradiated with 3 kGy absorbed dose, at variable dose rates of 1 and 5 kGy s^-1 of EB (10 MeV/10 kW), and 1.8 and 9 kGy h^-1 of GR (⁶⁰ Co).

Aerobic plate counts (APC) as well as yeast and mold counts of non-irradiated samples were 7.12 log CFU g^-1 and 6.62 log CFU g^-1 , respectively. EB and GR reduced these by 2-3 log CFU g^-1 . A lower dose rate (1 kGy s^-1 ) of EB was more effective for microbial reduction than a higher dose rate (5 kGy s^-1 ). In contrast, a higher dose rate (9 kGy h^-1 ) of GR efficiently decreased APC compared to a lower dose rate (1.8 kGy h^-1 ). Higher EB and GR dose rates significantly decreased the capsanthin content and Hunter's red color (a* value).

Low EB (kGy s^-1 ) and high GR (kGy h^-1 ) dose rates are recommended for microbiological safety of RPP with negligible changes in color attributes visible to the human eye, in contrast to the measured values. Thus the study demonstrates that the influence of absorbed dose is dependent on the applied dose rates. © 2018 Society of Chemical Industry.