Individual and combined mild heat and UV-C processes for orange juice against Escherichia coli O157:H7

This study was conducted to evaluate the individual and combined efficacies of mild heating at 53 degrees C and ultraviolet-C (UV-C) irradiation at 1.14 mW/cm(2) (0.0114 kJ/m(2) s) against E. coli O157:H7 in orange juice. Processes were calculated from inactivation parameters and applied to orange juice either individually such as heating to inactivate 5 log cycles of the organism (H-5D), UV-C irradiation to inactivate the same (UV-C-5D); or sequentially to achieve an additive inactivation rate of 5 log cycles, including H-3D -> UV-C-2D, and UV-C-2D -> H-3D. A simultaneous treatment of H-3D + UV-C-0.(2D) was also tested. Among the processes that targeted the 5-log reduction, only the H-5D was able to achieve the desired population decline (5.03 +/- 0.03 log CFU). The greatest population change was observed when subjected to the simultaneous H-3D + UV-C-0.(2D) process (6.35 log CFU). Microbiological quality indicators of orange juice subjected to the same set of processes were significantly improved with significant reduction in the ascorbic acid. Color space coordinates were also significantly affected by the treatments as determined by colorimetric measurements. However, color changes were not detected by consumers in samples, except for that subjected to the UV-C-5D.