Inactivation mechanisms of electron beam irradiation on Listeria innocua through the integrity of cell membrane, genomic DNA and protein structures

Abstract

As a non-thermal sterilisation technology, electron beam irradiation (EBI) has attracted great interest for microbial inactivation in food preservation. This study aims to investigate the effects of EBI on membrane permeability, physiological status, morphological structure, genome integrity and protein structures of Listeria innocua irradiated at doses of 0.75, 1.50, 2.25, 3.00, 3.75 and 5.00 kGy. The results showed that EBI noticeably reduced the total microbial counts of L. innocua by more than 7 log CFU mL À1 with 5.00 kGy treatment. The cell membrane permeability increased, resulting in the leakage of intracellular substances and changes in cell physiological status, which was proven by the cell staining and electron microscopy (EM) observations. Moreover, the integrity of genomic DNA and protein secondary structure, but not the protein primary structure were also disrupted. These findings provide the intrinsic mechanisms for the inactivation of L. innocua affected by EBI, which could serve as a theoretical basis for a better application of EBI in food sterilisation. the dose of radiation and the logarithm (log) of surviving bacteria (N). Cell membrane permeability assayThe cell membrane permeability was analysed by UV absorption spectra and the protein content in the