Radio frequency thermal inactivation mechanisms of Salmonella typhimurium and Listeria monocytogenes in broth: macroscopic and microscopic comparisons to conventional thermal treatments

Summary

Aims The objective of this study was to add valuable insight to the inactivation mechanisms of (Gram-negative) Salmonella typhimurium and (Gram-positive) Listeria monocytogenes by comparing radio frequency (RF) heating to conventional thermal treatments with similar dynamic temperature profiles. Methods and Results The Geereard et al. (2000) model with a Bigelow-type temperature dependency was fitted to the experimental data. Inactivation kinetics parameters were estimated and the sublethal injury was assessed. DNA and membrane integrity were evaluated by fluorescence and agarose gel electrophoresis methods. For both microorganisms, RF heating demonstrated a higher inactivation rate and higher sublethal injury than conventional treatments. RF treatments also caused more membrane damage than conventional treatments in both microorganisms. Agarose gel electrophoresis indicated an RF treatment-specific effect on DNA integrity only for L. monocytogenes. Conclusions Possible RF treatment-specific inactivation mechanisms were related to membrane damage and, depending on the microorganism, DNA damage. Effects are possibly caused by energy absorption of the bacterial cells. Future research using additional techniques (e.g. flow cytometry, next-generation sequencing) is necessary to gain deeper insights into the exact interactions of RF energy with the membrane and DNA of the two foodborne pathogens.

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DOI : doi.org/10.1093/jambio/lxaf292
NVA : hdl.handle.net/11250/5508468